Titanium alloy

FIELD: metallurgy.

SUBSTANCE: titanium alloy contains, wt %: platinum metal 0.01-0.15, rare-earth metal 0.001-0.10 and Ti and impurity - the rest. The titanium alloy preferably includes Co as partial replacement of Ti amounting 0.05-1.00 wt %.

EFFECT: alloy is characterised by high corrosion resistance, good workability.

7 cl, 9 dwg, 4 tbl, 2 ex

 

Area of technology

[0001] the Present invention relates to a titanium alloy, in particular, titanium alloy, which has high corrosion resistance, for example resistance to crevice corrosion and acid resistance with good machinability and economic advantages. The present invention also relates to a titanium alloy having high corrosion resistance and good machinability, with less chance of spread of corrosion arising from such defects as cracks.

Background of the invention

[0002] Titanium is widely used in areas such as the aviation industry, due to its characteristics of lightness and strength. In addition, due to its high corrosion resistance of titanium is increasingly used in various fields, such as materials of construction for chemical plants, thermal and nuclear power plants and water desalination plants.

[0003] However, although titanium is known for its good corrosion resistance, this high corrosion resistance manifested only in a limited number of environments such as oxidising acidic conditions (nitric acid) and neutral chloride environments such as seawater. He was not able to show sufficient resistance to crevice corrosion in high temperature outside�turno chloride environments or sufficient corrosion resistance in non-oxidizing acid solutions, such as hydrochloric acid (hereinafter collectively referred to as "corrosion resistance").

[0004] to solve the above problem, proposed titanium alloys, obtained by adding to the titanium metal of the platinum group, and on various assignments were used a number of standardized products, including alloys of ASTM of ASTM 7 and 17.

[0005] In particular, in the chlor-alkali industry as a material for the anode in the electrolysis of titanium alloys are used in areas where it may occur crevice corrosion due to the use of chlorine-containing highly concentrated brine, for example, 20-30% of the brine with a temperature of 100°C or above.

[0006] in addition, in the industrial sector of the refining of Nickel or lead alloys are used as material for reaction vessels or pipes that are exposed to suspensions containing highly concentrated solution of sulfuric acid at temperatures above 100°C.

[0007] in addition, titanium alloys are also used in the field of heat exchangers, e.g., heat exchanger tubes to produce the salt, experiencing the action of hot concentrated brines, and heat exchanger tubes for use in waste incinerators to heat exchange with flue gases containing chlorine, oxides of nitrogen and oxides of sulfur.

[0008] � petrochemical industries titanium alloys are used, for example, in the desulfurization reactor, exposed to crude oil, hydrogen sulfide, ammonium chloride or the like at elevated temperatures exceeding 100°C in the course of refining.

[0009] as an alloy with improved corrosion resistance for the aforementioned applications was developed alloy Ti-0,15 Pd (grade 7 ASTM). This titanium alloy takes advantage of the fact that Pd included in the composition of the alloy, reduces the hydrogen overvoltage and, thus, retains the potential of the spontaneous polarization within the range of passivation potential. Thus, the deposition and accumulation of Pd leached from the alloy during corrosion, causes a decrease in hydrogen overvoltage, thereby holding the potential of the spontaneous polarization within the range of passivation potential and achieving high corrosion resistance.

[0010] However, since the alloy ASTM 7 with high corrosion resistance contains Pd, which is a platinum group metal and very expensive (2200 Japanese yen per gram, according to the morning edition of the Nihon Keizai Shimbun dated 9 February 2011 ), its use was limited.

[0011] to solve this problem, they proposed a titanium alloy with low content of Pd, from 0.03 to 0.1 wt%. (mark ASTM 17), which was implemented in the practical application, as described in patent document 1. Despite the leniency�enny the Pd content in comparison with an alloy of ASTM 7, the alloy grade ASTM 17 exhibits a high resistance to crevice corrosion.

[0012] Patent document 2 discloses a titanium alloy, which can be produced at lower cost, without compromising its corrosion resistance. Titanium alloy according to the patent document 2 contains from 0.01 to 0.12 wt%. in the amount of at least one of the metals of the platinum group and 5% of the mass. or less of at least one of Al, Cr, Zr, Nb, Si, Sn and Mn. In typical applications of titanium alloys exhibit adequate properties such as corrosion resistance, if Pd is present in an amount of from 0.01 to 0.12 wt%. However, to answer the arisen in recent years the requirements for further improvement of properties, the Pd content, especially if it be reduced to less than 0.05%, it is insufficient for the manifestation of a titanium alloy appropriate properties such as corrosion resistance. Furthermore, even in typical applications there is a growing need to further reduce costs.

[0013] Patent documents 3 and 4 disclose titanium alloys containing a combination of platinum group metal, rare earth metal and transition metal, as inventions related to a different technical field than the present invention. These inventions relate to ultrahigh vacuum chambers and titanium alloys for application in ultrahigh vacuum chambers the relevant�but.

[0014] In these inventions the addition of platinum group metal and a rare earth metal that strive to achieve the advantages of inhibition in ultrahigh vacuum environment of diffusion and extraction in the vacuum of gaseous components forming a solid solution in the material. These patent documents claim that the platinum group metal acts in the titanium alloy as a trap hydrogen, and rare-earth element acts as a trap oxygen.

[0015] in addition, these inventions provide as a significant component of a transition metal selected from the group consisting of Co, Fe, Cr, Ni, Mn and Cu, in addition to the platinum group metal and rare earth metal. These patent documents claim that the transition metal promotes binding of hydrogen atoms adsorbed on the surface of the vacuum chamber, a platinum group metal. However, it is not clear if the titanium alloys according to patent documents 3 and 4, the corrosion resistance, as in that respect is silent or not assumed.

[0016] non-Patent document 1 indicates that Pd must be present in an amount of 0.05 wt%. or more, to provide resistance to crevice corrosion of the alloy Ti-Pd, and that the addition of Co, Ni or V as the third component improves the resistance to crevice corrosion.

[0017] As described above, the level of those methods�IKI less meet the requirements for further improvement of properties, if the Pd content lower than 0.05 wt%.

[0018] in addition, even the alloy Ti-Pd with a Pd content of 0.05 wt%. or above had a problem that, when conditions arise on the surface defects such as cracks are likely to develop corrosion originating on the defects.

The citation list

[0019] Patent literature

Patent document 1: Japanese patent publication no. H04-57735

Patent document 2: international publication no WO 2007/077645

Patent document 3: published Japanese patent application No. H06-64600

Patent document 4: published Japanese patent application No. H06-65661

[0020] non-Patent literature

Non-patent document 1: The Society of Materials Science, Committee on Corrosion and Protection, "Low Titanium Alloy Having Good Crevice Corrosion Resistance ("Low-alloy titanium, with good resistance to crevice corrosion"), SMI-ACE, 12.09.2001.

Summary of the invention

Technical problem

[0021] the Present invention was created in view of the above problems. Accordingly, the present invention is to develop a titanium alloy, the corrosion resistance which is comparable or better than in the prior art, and which also has good machinability and has economic advantages due to a low content of platinum group metal such as Pd, in comparison with the level of technical�Ki. Another object of the invention is to create a titanium alloy, which is close to the level of technology the Pd content, but which has the advantages of corrosion resistance, comparable or better than in the prior art, and good workability and also lower the probability distribution of corrosion originating on the defects, such as formed in the surface of the crack.

The solution to the problem

[0022] to solve the above problem, the authors of the present invention achieved a better understanding of the mechanism of improving the corrosion resistance of the alloy Ti-Pd and has conducted research in the following areas: improving the corrosion resistance of the alloy Ti-Pd by incorporating non-traditional element that contributes to the achievement of the desired conditions on the surface for superior corrosion resistance; and achieving corrosion resistance, comparable or better than in the prior art, at low Pd content in comparison with the prior art.

[0023] In this respect the present invention differs from prior art methods aimed at achieving improved corrosion resistance of titanium alloy by incremental inclusion of additional elements which are effective in improving the corrosion resistance, as described in patent document 2 and non-patent document 1.

<> [0024] Figure 1 schematically illustrates the mechanism for improving the corrosion resistance of the alloy Ti-Pd(-Co). Alloy Ti-Pd, and an alloy of Ti-Pd-Co in the initial conditions is in the active state. Being immersed in the acid solution, such as boiling hydrochloric acid, Ti and Pd, or Ti, Pd and Co, are dissolved from the surface, and dissolved Pd or dissolved Pd and Co are deposited on the surface and accumulate therein, thereby reducing the hydrogen overvoltage of the alloy as a whole. This allows the alloy to remain in the range of passivation potential and, thus, to show good corrosion resistance.

[0025] to ensure rapid and uniform deposition and accumulation of Pd on the surface after the alloy Ti-Pd immersed in the acid solution, the authors of the present invention conducted a search of elements that facilitate the dissolution of the matrix alloy, occurring at an early stage after immersion in the solution.

[0026] the following assumptions are made. If the presence of non-traditional element included in the composition of the alloy, makes the matrix of the alloy to melt at an early stage after immersion in acid solution, that can occur increasing the concentration of Pd ions in solution near the outer surface, and therefore it is possible to quickly reach the appropriate degree of deposition and accumulation of Pd (a"proper degree" means here is great�e the number of Pd, than in the case where the non-traditional element is not present). If it is the deposition and accumulation of Pd is reached, the hydrogen overvoltage of the alloy Ti-Pd may decline rapidly, even if the Pd content is low, allowing, thus, to shift to more noble and stable potential (potential range passivation).

[0027] In the case of alloy Ti-Pd low Pd content the rapid dissolution of the matrix alloy in the active state at an early stage can be achieved by the introduction of this innovative item. If this takes place, the concentration of Pd ions and Ti near the surface should be increased compared with the case where this element is absent, so is the deposition and accumulation of Pd. As a result, the hydrogen overvoltage of the alloy should decline rapidly, thus allowing you to keep the alloy in the range of passivation potential.

[0028] on the other hand, if the alloy Ti-Pd low Pd content to facilitate the dissolution of the matrix alloy, the concentration of Pd ions and Ti near the surface can be enhanced, and leached Pd can diffuse. Thus, the deposition of Pd may occur with a smaller probability, which can lead to low corrosion resistance.

[0029] meanwhile, in the case of the alloy Ti-Pd high Pd content, even if the conditions there are such p�surface defects as cracks, the presence of non-traditional element may allow the rapid deposition and accumulation of Pd on the fresh surface, resulting from defects. This should allow to move the hydrogen overvoltage of the alloy in the range of passivation potential and, thus, lead to the elimination of defects. The result is to be achieved the advantage of less risk of the spread of incipient defects on the corrosion.

[0030] Based on the above assumptions, the authors of the present invention conducted experiments in search of elements that facilitate the dissolution of the matrix alloy, which occurs at an early stage after immersion in the solution, that is, elements that facilitate the deposition and accumulation of Pd on the surface of the alloy Ti-Pd. As a result, the authors found that such an element, which satisfies these requirements, are rare earth metals.

[0031] the Present invention was established on the basis of these detected data, and its essence is expressed below in paragraphs (1) to(5) related to titanium alloys.

[0032] (1) Titanium alloy containing, in wt.%, platinum group metal: 0.01 to 0.15% and rare earth metal: 0,001-0,10%, while the remainder Ti and impurities.

[0033] (2) Titanium alloy according to the above item (1), which includes Co as a partial replacement of Ti in an amount of 0.05 to 1.00 wt.%, work for this rare earth metal is present in an amount of from 0.001 to less than 0.02% of the mass.

[0034] (3) Titanium alloy on the above item (1) or (2) in which the platinum group metal is present in amounts of 0.01-0.05% of the mass.

[0035] (4) Titanium alloy according to any one of the above paragraphs (1) to(3), in which the platinum group metal is Pd.

[0036] (5) Titanium alloy according to any one of above paragraphs (1) to(4), in which the rare earth metal is Y.

[0037] In the description below, the expression "% by weight" and "ppm by mass" (mass ppm) used in the composition of the titanium alloy, marked simply "%" and "ppm", respectively, unless otherwise indicated.

Advantageous effects of invention

[0038] the Titanium alloy of the present invention has high corrosion resistance and good machinability. Due to this, when using a titanium alloy of the present invention can improve the performance and reliability of equipment and machines that are used in corrosive environments (especially in hot concentrated chloride environments). If the platinum group metal is contained in relatively small quantities, the invention provides the advantage of more economical material costs for these titanium alloys. If the platinum group metal is included in relatively large quantities, the invention provides the advantage of a lower probability p�of prostrate corrosion emerging from such defects as encountered in surface cracks.

Brief description of the drawings

[0039] Fig. 1 is a schematic diagram illustrating a mechanism for improving the corrosion resistance of the alloy Ti-Pd(-Co).

Fig. 2 is a schematic diagram of the test specimen for resistance to crevice corrosion, and Fig. 2(a) shows a top view, and Fig. 2(b) - side view.

Fig. 3 is a schematic diagram of the sample when used in a test for crevice corrosion (ASTM G78).

Fig. 4 is a schematic diagram of the test specimen in hot (boiling) hydrochloric acid, and Fig. 4(a) shows a top view, and Fig. 4(b) - side view.

Fig. 5 is a graph showing the change with time of the corrosion rate of the comparative example 6 and comparative example 7 when immersed in boiling 3% hydrochloric acid solution.

Fig. 6 is a graph showing the change with time of the corrosion rate of example 8 according to the invention, comparative example 5 and conventional example 2, when immersed in boiling 3% solution of hydrochloric acid.

Fig. 7 is a graph showing the concentration profile of Pd, Ti and O in titanium alloy of example 4 according to the invention, depending on the distance inward from the surface.

Fig. 8 is a graph showing the concentration profile Pd, T and O in titanium alloy of comparative example 5 as a function of the distance inward from the surface.

Fig. 9 is a graph showing the results of trials in hot (boiling) hydrochloric acid. In this Fig. 9(a) is a graph showing the relationship between the average corrosion rate for 96 hours and the content of Y; and Fig. 9(b) is a graph showing the relationship between the surface concentration of Pd after the test and the content of Y.

Description of embodiments of

[0040] As described above, the titanium alloy of the present invention contains, in wt.%: platinum group metal: 0.01 to 0.15% and rare earth metal: 0,001-0,10%, and the remainder consists of Ti and impurities. The details of the present invention are set forth below.

1. The range of chemical compositions of titanium alloy and the reasons for its restrictions

1-1. Platinum group metal

[0041] as Used herein, the expression "platinum group metal" refers to Ru, Rh, Pd, Os, Ir and Pt. Platinum group metals provide an advantageous effect of reducing the hydrogen overvoltage of titanium alloy and retention potential of the spontaneous polarization in the range of passivation potential and therefore are an essential component of a titanium alloy having corrosion resistance. Titanium alloy of the present invention includes one or more platinum group metals. The total content of one or more platinum group metals (hereinafter simply referred to as "ODS�the neighing of platinum group metals") is in the range from 0.01 to 0.15%. This is because if the content of platinum group metals is lower than 0.01%, the alloy exhibits poor corrosion resistance and, thus, may experience the impact of corrosion in hot concentrated chloride solution. Meanwhile, the content of platinum group metals exceeding 0.15%, and gives no further improvement in corrosion resistance, requiring a lot of material costs.

[0042] For use on traditional appointments, the content of platinum group metals preferably varies from 0.01 to 0.05%, taking into account the balance between economic benefit and corrosion resistance. The fact is that even in this range of the content of platinum group metals titanium alloy of the present invention exhibits corrosion resistance comparable to traditional corrosion resistance of titanium alloys having a content of platinum group metals than 0.05%.

[0043] meanwhile, when a titanium alloy there are cracks or the like, then the higher the content of platinum group metals, the faster the deposition and accumulation of platinum group metals on the fresh surface, resulting from cracks or etc., as described above, taking as an example the alloy Ti-Pd. Thus, the higher the content of platinum group metals, the faster the potential in the place of the tre�ins (or so p. ) will shift toward the range of passivation potential, allowing you to restore the surface, which leads to a lower probability of corrosion originating on the cracks or etc. Thus, even when the platinum group metal contained in the range from 0.05 to 0.15%, there is also a benefit in relation to the suitability for use in harsh environments.

[0044] In the present invention the most preferred platinum group metals, i.e., Ru, Rh, Pd, Os, Ir and Pt, is Pd, because Pd is relatively inexpensive and is able to provide a greater degree of improvement of corrosion resistance per unit content. Rh and Pt are not economically feasible, as they are very expensive. Ru and Ir are less expensive than Pd, and can be used as substitute Pd. However, their production is not as high as the production of Pd, therefore, the preferred solution is always available Pd.

1-2. Rare earth metal

1-2-1. The reasons for introducing the rare earth metal

[0045] the Authors present invention investigated the possibility of the formation of the alloy Ti-a 0.02 Pd, incorporating a trace amount of an element that is easily soluble in hot concentrated chloride environments. To detect the effect produced by such an element, the authors conducted a study, immersing titanium alloy, formed with possibly effective elemento�, in chloride solution and maintaining it dissolved in the potential activation, and investigated the effect of shift of the alloy in the range of passivation potential by facilitating the deposition and accumulation of platinum group metal on the surface. The study of a number of elements, it was found that rare earth elements are able to give such an effect.

[0046] As described above, the content of the platinum group metal is preferably in the range of from 0.01 to 0.05%. After additional studies, the inventors found that the same effect can be obtained when the content of platinum group metal more than 0,05%. Thus, if the rare earth metal is introduced into the composition containing the platinum group metal titanium alloy containing platinum group metal more than 0.05%, as in the case of containing a platinum group metal alloy with the content of the platinum group metal of 0.01-0.05%, rapid dissolution of Ti and a metal of the platinum group occurs at an early stage after exposure to a corrosive environment. Thus, the ion concentration of the platinum group metal near the outer surface of the titanium alloy is increased, thereby allowing rapid deposition and accumulation of platinum group metal on the surface of a titanium alloy. Essentially containing a platinum group metal �economy alloy, educated with rare-earth metal that can cause the deposition of platinum group metal on the surface more efficiently than those containing platinum group metal titanium alloy containing no rare earth metal. Consequently, it exhibits higher corrosion resistance, making possible the efficient deposition of platinum group metal, even if the extent of corrosion of all titanium alloy small. Besides containing the platinum group metal titanium alloy, formed with a rare earth metal, is able to maintain its corrosion resistance even in more severe conditions than is commonly practiced. For example, when applied to the installation or the like, which use hot concentrated chloride solutions, even if deposited on the surface of the platinum group metal is removed due to abrasion or the like, or even if there are surface defects such as cracks, as described above, this titanium alloy is able to restore the surface, providing the possibility of rapid deposition and accumulation of platinum group metal and thereby maintaining its corrosion resistance.

[0047] the Rare earth metals include Sc, Y, light rare earth elements (La through Eu) and heavy rare earth elements (Gd to Lu). According to the results�the ATA research conducted by the authors of the present invention, it was found that all effective rare earth metals. Also, do not need to enter only one rare earth metal. Effective was the use of a mixture of rare earth metals, such as mixed rare earth metals before the separation and refining (mischmetal, hereinafter referred to also "Mm") or Didim (a mixture of Nd and Pr). Therefore, from an economic point of view, the preferred rare earth metals are La, Ce, Nd, Pr, Sm, Mm, Didim, Y, etc. for their availability and relative cheapness. As for the Mm and Didymus, you can use any ratio of constituent components in the composition, if used to purchase these materials.

1-2-2. The content of rare earth metal

[0048] In the titanium alloy of the present invention, the content of rare earth metals varies from 0.001 to 0.10%. The reason for choosing the lower limit of the content of rare earth metal in a 0.001% is to sufficiently obtain the advantageous effect of the deposition of Pd on the surface of the alloy to provide a simultaneous dissolution of Ti, Pd and rare-earth metal chloride in a solution at a potential activation of the alloy Ti-Pd.

[0049] the Reason for choosing the upper limit of the rare earth metal content of 0.10% is that excessively in�high amount of rare earth metal in the alloy Ti-Pd can cause the formation of a new compound in the titanium alloy. This new connection is predominantly soluble in the chloride solution and, thus, leads to the initiation of pitting corrosion in the alloy Ti-Pd. Because of this, alloys Ti-Pd, including this compound, showing the worst corrosion resistance in comparison with alloys of Ti-Pd, not containing rare earth metals. In addition, it is preferable that the content of rare earth metal in the alloy Ti-Pd was not more than its limit of solubility in the solid state in the phase α-Ti, as shown on the phase diagram or the like.

[0050] for Example, the solubility limit of Y in the solid state in the phase α-Ti alloy Ti-a 0.02 Pd equal to 0.02% of the mass. (0.01 at.%). Thus, when administered Y, its content is preferably less than 0.02% of the mass.

[0051] the content of Y is less than 0.02% is enough from the viewpoint of facilitating the accumulation of platinum group metal on the surface of a titanium alloy, although the more significant advantages are achieved if the content of Y is limited to 0.01% or less.

[0052] La has a very large limit of solubility in the phase α-Ti alloy Ti-a 0.02 Pd, at the level of 2.84% of the mass. (1 at.%) (T. B. Massalski, "Binary Alloy Phase Diagrams, Volume 3" ("Phase diagrams of binary alloys"), USA, 2nd Edition, ASM International, 1990, p. 2432). However, from the point of view of providing economic benefits to La, if administered, is contained in the amount of 0.10% of the mass. or less.

[0053] As in the case of Y, contain sufficient�R La from the point of view of facilitating the accumulation of platinum group metals on the surface of the titanium alloy is less than 0.02%, although the more significant advantages are achieved if the content is limited to 0.01% or less.

1-3. The addition of Co in combination with rare-earth metal

[0054] the Titanium alloy of the present invention may include Co, as a partial replacement of Ti in an amount of 0.05-1%. Co is an element that increases the resistance to crevice corrosion of titanium alloy. The authors present invention found that the introduction of Co as partial replacement of Ti containing platinum group metal, titanium alloy, formed with a rare earth metal, leading to a higher corrosion resistance due to the synergy with rare-earth metal.

[0055] to obtain synergy, Co should be present in an amount of 0.05% or more. At the same time, if the Co content exceeds 1%, rare earth metal and Co are formed intermetallic compound type AB5(A = rare earth metal, B = Co), which leads to deterioration of corrosion resistance of titanium alloy. So was the range of the Co content is from 0.05 to 1%.

1-4. Ni, Mo, V, Cr and W

[0056] the Titanium alloy of the present invention may include Ni, Mo, V, Cr, and W as a partial replacement of Ti. The introduction of these elements leads to high resistance to crevice corrosion due to the synergy with rare-earth metal. When these elements are introduced, their contents status�control: Ni: 1,0% or less, Mo: 0.5% or less, V: 0.5% or less, Cr: 0.5% or less and W: 0.5% or less.

1-5. Impurity elements

[0057] the Impurity elements in the titanium alloy include, for example, Fe, O, C, H, N, etc., coming from raw materials that dissolve the electrode and the environment, as well as Al, Cr, Zr, Nb, Si, Sn, Mn, Cu, etc. entered, when used as the raw material scrap, or the like. The introduction of these impurity elements does not matter, unless it does not adversely affect the advantages of the present invention. In particular, the range of component composition, without a negative impact on the advantages of the present invention, is as follows: Fe: 0.3% or less, About: of 0.35% or less: 0.18% of or less, N: 0,015% or less, N: 0.03% or less, Al: 0.3% or less, Cr: 0.2%, or less, Zr: 0.2% or less, Nb: 0.2% or less, Si: 0.02% or less, Sn: 0,2% or less, Mn: 0.01% to or less, and Cu: 0.1% or less when the total of their contents, amounting to 0.6% or less. Example 1

[0058] To confirm the resistance to crevice corrosion and resistance to hot (boiling) hydrochloric acid titanium alloys of the present invention, the following tests were evaluated and their results.

1. The test conditions

1-1. Samples

1-1-1. Titanium alloys according to the traditional examples

[0059] traditional Titanium alloys of examples 1-3 were obtained from purchased, commercially available sheets of the alloy Ti-Pd thick� 4 mm. Types and results of the analysis of the elemental composition of purchased materials are also given in table 1. A traditional example 1 is a brand of ASTM 7, conventional example 2 - ASTM brand 17, a traditional example of 3 - class 19 to JIS (grade ASTM 30). Traditional examples 4 and 5 represent the alloys Ti-Pd with Pd content, close to the lower limit of the range disclosed in patent document 1. All traditional examples 1-5 are examples of the alloy Ti-Pd, not containing rare earth metals. Traditional examples 1 and 2 are standards for the examples according to the invention, which will be discussed later.

[0060]

Table 1
ClassificationComposition of alloy (wt.%, and the rest - Ti and impurities)Note
Redkozemel-tion metalMetal pay new groupCoFeOAl
example 1 according to the invention isY:0,02Pd:0,15-- --
example 2 according to the invention isY:0,02Pd:0,11----
example 3 according to the invention isY:0,02Pd:0,05----
example 4 according to the invention isY:0,02Pd:0,02----
example 5 according to the invention isY:0,02Pd:0,01----
(comparative example 3)Y:0,02Pd:0,004--- -
example 6 according to the invention isY:0,02Pd:0,021,0---
example 7 according to the invention isY:0,02Pd:0,020,5---
(comparative example 1)Y:0,12Pd:0,02
(example 4 of the invention)Y:0,02Pd:0,02----
example 8 according to the invention isY:0,01Pd:0,02----
example 9 according to the invention isY:0,003Pd:0,02----
(comparative example 2)Y:4 ppmPd:0,02----
(comparative example 5)-Pd:0,02----
example 10 according to the invention isY:0,10Pd:0,03----
example 11 according to the invention isDy:0,10Pd:0,03----

example 12 according to the invention isLa:0,08Pd:0,03----example 13 according to the invention isDidim:0,04Pd:0,03----example 14 according to the invention isPr:0,03Pd:0,03----example 15 according to the invention isCe:0,09Pd:0,02----example 16 according to the invention isMm:0,05Pd:0,02---- example 17 according to the invention isNd:0,05Pd:0,020,2---example 18 according to the invention isSm:0,06Pd:0,010,3---example 19 according to the invention isY:0,02EN:0,04----PGM: EN(comparative example 8)-EN:0,04----PGM: ENcomparative example 1Y:0,12Pd:0,02----REM: outside the preset range comparative example 2Y:4 ppmPd:0,02----REM: outside the preset rangecomparative example 3Y:0,02Pd:0,004----PGM: outside the preset rangecomparative example 4La:0,10Pd:0,031,2---Co content: outside the preset rangecomparative example 5-Pd:0,02----No REMcomparative example 6Y:0,01---- -No PGMcomparative example 7-----Ti class-1 JIS

1-1-2. The samples according to examples of the invention and comparative examples

[0061] Titanium alloys according to the examples according to the invention and comparative examples prepared using sheet materials with elemental compositions shown in table 1.

1-1-2-1. Materials samples

[0062] Titanium alloys according to the examples according to the invention and comparative examples were prepared, using quality materials manufactured sponge pure titanium (JIS class 1), powder of palladium (Pd) manufactured by KISHIDA CHEMICAL Co., Ltd. (99.9% purity), powder of ruthenium (Ru) manufactured by KISHIDA CHEMICAL Co., Ltd. (99.9% purity), shavings of yttrium (Y) manufactured by KISHIDA CHEMICAL Co., Ltd. (99.9% purity), ingot rare earth metal and the ingot electrolytic cobalt (Co) (purity of 99.8%). Used rare earth metals were Mm, La, Nd, CE, Dy, Pr, Sm and Didim, all of which, except for Mm and Didymus, had a purity of 99%. Mm consisted of La: 28,6%, Ce: 48,8%, Pr: 6.4% and Nd: 16.2% and Didim consisted of a Nd: 70,1% and Pr: 29,9%.

0063] The titanium alloys according to the examples 1 to 18 according to the invention have the composition, defined by the present invention. Of these, examples 6, 7, 17 and 18 according to the invention contain a rare earth metal, Pd and Co, example 19 according to the invention contains Y and Ru, but does not contain a platinum group metal, and other examples of the invention contain a rare earth metal and Pd, but do not include other constituent elements. In table 1, the symbol "-" indicates that the element content was below detection limits.

[0064] The titanium alloys according to comparative examples 1 to 8 have a composition outside the range specified in the present invention. Both comparative example 1 and 2 contain Y and Pd. Comparative example 1 has a content of Y is higher than the range defined by the present invention and the comparative example 2 has a content of Y is lower than the range defined by the present invention. Comparative example 3 contains Y and Pd, and the Pd content is below the range established by the present invention. Comparative example 4 contains La, Pd and Co, and the content of Co is higher than the range defined by the present invention. Each of comparative examples 5-8 contains only one rare earth metal and platinum group metal or does not contain either. Of these, comparative example 7 is made of titanium grade 1 according to JIS.

[0065] In table 1, example 4 according to the invention, comparative example 3, CPA�comparative example 5 and comparative example 8 are shown twice for each of the comparisons.

1-1-2-2. Method of preparation of samples

[0066] Using an electric arc melting furnace in an argon atmosphere, produced five ingots of the above materials, of 80 grams each. Then all five bars combined and melted, having a square ingot with a thickness of 15 mm. of Finished square ingot melted homogenization and again molded in square ingot with a thickness of 15 mm. Thus, only conducted three stages of melting.

[0067] since the square bars in all the examples contained trace amounts of Pd and/or rare earth metal, applied a homogenization heat treatment to reduce segregation of the elements, under the following conditions:

atmosphere: vacuum (<10-3Torr);

temperature: 1100°C; and

time: 24 hours.

[0068] the Square ingot subjected to homogenizing heat treatment, roll under the following conditions and molded to sheet thickness of 4 mm:

β-phase hot rolling: at 1000°C, the reduction of thickness from 15 mm to 9 mm; and

α+β-phase hot rolling: at 875°C, the reduction of thickness from 9 mm to 4 mm.

[0069] the Sheet materials obtained after rolling, annealed to relieve stresses in vacuum at 750°C for 30 minutes.

1-2. The test conditions

[0070] the Test for resistance to crevice corrosion and test in hot (boiling) hydrochloric acid was carried out using� samples taken from sheet materials purchased on the market or obtained by the above described method.

1-2-1. The test for resistance to crevice corrosion

[0071] Fig. 2 schematically shows a sample for testing for resistance to crevice corrosion, and Fig. 2(a) is a top view, and Fig. 2(b) is a side view. The sample thickness of 3 mm, a width of 30 mm and a length of 30 mm, as shown in the figure, cut out of sheet material and provided with a hole diameter of 7 mm at its center. This sample was polished with sandpaper 600.

[0072] Fig. 3 schematically shows the sample used to test for crevice corrosion. Shown in the figure the sample polished with sandpaper, used to test for crevice corrosion in accordance with the test multiple crevice corrosion in accordance with specification ASTM G78. Sample 1 was kept on both sides mnogotselevye nodes 2, pressed against him and tightened to a torque of 10 kgf·cm with the use of a bolt 3 and nut 4 from pure titanium. Mnogotselevye nodes 2 were made of politicalarena. They were placed so that their grooved surfaces were in contact with the sample 1. Test for crevice corrosion was performed under the following conditions:

Wednesday test: 250 g/l NaCl, pH=2 (pH was adjusted with HC1), 150°C, rich atmosphere; and

the duration of the ISP�taniya: 240 hours.

1-2-2. The test in hot (boiling) hydrochloric acid

[0073] Fig. 4 schematically shows the test specimen in hot (boiling) hydrochloric acid, and Fig. 4(a) is a top view, and Fig. 4(b) is a side view. A sample having the shape of a coin with a thickness of 2 mm and a diameter of 15 mm, as shown in the figure, cut out of sheet material. This sample was polished with sandpaper 600. After immersing the sample in hot hydrochloric acid under the following conditions expected degree of corrosion (corrosion rate) per unit time by the reduction of mass due to corrosion.

[0074] the Test in hot (boiling) hydrochloric acid, representing the corrosion test, which simulates the internal environment in cracks in crevice corrosion was performed in the following conditions. Boiling capacity for testing supplied coil condenser for cooling and condensation of hot steam back into liquid, to ensure that the concentration of the solution:

the concentration and temperature of solution: 3% hydrochloric acid (boiling);

the pH of the solution: pH≈0 (normal temperature); and

dive time: 96 hours.

1-2-3. The study of changes in the concentration of Pd near the surface of a titanium alloy

[0075] As described above, the rare earth metal included in the alloy Ti-Pd, facilitates the dissolution of the matrix alloy in the hot environment�of concentrated chloride solution. This facilitates the deposition of Pd on the surface of a titanium alloy, providing an advantageous effect of the shift of the alloy in the range of passivation potential. Thus, it is assumed that the test for crevice corrosion of titanium alloy containing rare earth metal, will have a higher concentration of Pd on the surface than titanium alloy containing no rare earth metal. To test this hypothesis, samples after 96-hour tests in hot (boiling) hydrochloric acid was investigated on the change in the concentration of Pd depending on the distance inward from the outer surface.

[0076] the measurement of Pd was carried out under the following conditions:

method of analysis: optical emission spectroscopy glow discharge, the type of Marcus with radiofrequency source (hereinafter referred to as the "GDOES"),

analyzer: GD-Profiler 2 HORIBA;

analyzed field: the area of the sample surface 4 mm in diameter in contact with boiling hydrochloric acid; and

depth: area up to 250 nm inward from the outer surface.

2. The test results

[0077] to evaluate the number of slot places affected by corrosion, the average corrosion rate and economic benefits, as well as evaluating on the basis of all of these factors combined. The results are shown in table 2.

[0078]

example 5 according to the invention is
Table 2
ClassificationResistance to crevice corrosionResistance to hot (boiling) hydrochloric acidEconomic benefits (accounting for the cost of materials)*2
The slot number of places affected by corrosion*1The average corrosion rate for the first 7 hours (mm/year)The average corrosion rates at 96 hours (mm/year)
example 1 according to the invention is00,140,02δ
example 2 according to the invention is00,210,05δ
example 3 according to the invention is02,180,14δ
example 4 according to the invention is0Of 3.980,19
04,020,25
(comparative example 3)289,14Of 3.87
example 6 according to the invention is02,220,13
example 7 according to the invention is02,380,17
(comparative example 1)86,121,74
(example 4 of the invention)0Of 3.980,19
example 8 according to the invention is04,400,27
example 9 according to the invention is04,78 0,29
(comparative example 2)15For 15.391,90
(comparative example 5)209,540,70
example 10 according to the invention is03,110,18

a traditional example 1
example 11 according to the invention is03,740,21
example 12 according to the invention is03,790,23
example 13 according to the invention is0Of 3.870,22
example 14 according to the invention is03,49 0,21
example 15 according to the invention is03,810,22
example 16 according to the invention is0Of 3.910,24
example 17 according to the invention is02,910,18
example 18 according to the invention is03,090,19
example 19 according to the invention is04,120,28
(comparative example 8)118,35Of 1.82
comparative example 186,121,74
comparative example 215For 15.391,90
comparative example 3289,14Of 3.87
comparative example 414,821,11
comparative example 5209,540,70
comparative example 64016,2016,60
comparative example 7404,104,12
comparative example 8118,35Of 1.82
00,210,04δ
a traditional example 204,170,37δ
a traditional example 303,020,20δ
a traditional example 475,381,68
a traditional example 536,861,93
1Resistance to crevice corrosion: was estimated by the number of slit places affected by corrosion (the number of seats crevice corrosion of all slit 40 seats)
*2Economic benefit: the symbol "◯" refers to the Pd content of less than 0.05% or EN content of 0.04%, and the symbol "∆" refers to the Pd content is from 0.05 to 0.15%*

2-1. Resistance to crevice corrosion

[0079] table 2 vklyuchayaego the resistance to crevice corrosion, specify the number of places affected by corrosion, of the 40 annular seats formed mnogotselevye nodes. After tests conducted under the above conditions, none of the examples according to the invention (examples 1 to 19 according to the invention) and none of the conventional examples 1-3 did not suffer from the effects of corrosion in any of the slit 40. Among these examples, examples 4-18 according to the invention, the Pd content of less than 0.05%, and example 19 according to the invention, with the EN content of 0.04%, were cost-effective.

[0080] meanwhile, all comparative examples (comparative examples 1-8) and traditional examples 4 and 5 suffered from the effects of corrosion. From the traditional results of examples 1-5 shows that if you do not enter a rare earth metal, you need the Pd content of about 0.06 percent, to provide resistance to crevice corrosion.

2-2. The test in hot (boiling) hydrochloric acid

[0081] Since the corrosion rate of the alloys Ti-Pd decreases with time, the score test in hot (boiling) hydrochloric acid under the above conditions was performed using two indicators: the average corrosion rate for the first 7 hours and the average corrosion rates at 96 hours after the start of the dive.

[0082] Fig. 5 and Fig. 6 are graphs showing changes with time of the corrosion rate of the comparative examples 6 and 7 and example 8 of the invention, will compare�form of further example 5 and conventional example 2 accordingly, when immersed in boiling 3% solution of hydrochloric acid. Of the figures and results are shown in table 2, were obtained the following conclusions(1)-(8).

[0083] (1) Titanium alloys according to comparative examples 6 and 7, which do not contain Pd, felt the spread of corrosion without reducing the corrosion rate, as shown in Fig. 5. It is assumed that the higher the average corrosion rate in comparative example 6 than in comparative example 7, the results of the presence of Y, which facilitated the dissolution of the matrix alloy.

[0084] (2) Examples 1 to 18 according to the invention had an average corrosion rate, lower or comparable to the corrosion rate in conventional example 2, that serves as a benchmark, as for the first 7 hours, and 96 hours. In particular, conventional example 2 had an average corrosion rate of 4.17 mm and 0.37 mm/year for the first 7 hours and 96 hours, respectively, while examples of the invention had an average corrosion rate of 5 mm/year or less and 0.3 mm/year or less, respectively. In addition, as shown in Fig. 6, example 8 according to the invention with a content of Y is 0.01% and Pd content of 0.02% had an average corrosion rate, comparable to or less than conventional example 2 with the Pd content of 0.06%. From Fig. 6 it is also seen that when Y is absent, a higher Pd content leads to a lower corrosion rate.

[0085] (3) Compared�e between the results of example 1 according to the invention with high Pd content of 0.15% and conventional example 1 as a benchmark, also with high Pd content at 0.14%, and shows that the presence of Y leads to a lower average corrosion rate for the first 7 hours and 96 hours, and better resistance to hot (boiling) hydrochloric acid.

[0086] (4) Comparison between the results of examples 1-5 according to the invention and comparative example 3, which all had the same content of Y is 0.02%, shows that the higher the Pd content, the less the average corrosion rate for the first 7 hours and 96 hours, and the higher the resistance to hot (boiling) hydrochloric acid.

[0087] (5) Comparison between the results of example 4 according to the invention, of example 8 according to the invention, of example 9 according to the invention, comparative example 1, comparative example 2 and comparative example 5, which all have the same Pd content of 0.02%, shows that the higher content of Y, the less the average corrosion rate for the first 7 hours and 96 hours, and the better resistance to hot (boiling) hydrochloric acid. However, the content of Y above 0.1% (comparative example 1) leads to the worst resistance to hot (boiling) hydrochloric acid for the reasons stated above. In addition, in comparative example 5, the average corrosion rate decreased significantly with 9,54 mm/year for the first 7 hours to 0.70 mm/year for 96 hours. This indicates that in the absence of a rare earth metal deposition and accumulation of Pd requires �more time and thus, its efficiency is low.

[0088] (6) the Comparison between the results of example 4 according to the invention, of example 6 according to the invention and example 7 of the invention, which all have the same content Y of 0.02% and a Pd content of 0.02%, shows that the higher the Co content, the less the average corrosion rate for the first 7 hours and 96 hours, and the better resistance to hot (boiling) hydrochloric acid.

[0089] (7) Examples 10-16 of the invention have a content of Pd of 0.03% or less and the content of rare earth metal from 0.03 to 0.10%, and each sample contains different rare earth metal. From these results it is evident that the presence of any rare earth metal leads to a lower average corrosion rate for the first 7 hours and 96 hours, and better resistance to hot (boiling) hydrochloric acid than conventional example 2. This means that the presence of rare earth metal facilitated the dissolution of the matrix alloy and, thus, improve the efficiency of deposition and accumulation of Pd. It was also found that the introduction of Y, and no other rare-earth metals, contributes to a better resistance to hot (boiling) hydrochloric acid.

[0090] (8) the Comparison between the results of example 19 according to the invention and comparative example 8, which both have the same content of Ru in of 0.04%, which is a platinum group metal, while�device, what example 19 according to the invention, which contains Y, shows the best resistance to hot (boiling) hydrochloric acid, than that of comparative example 8, which does not contain a rare earth metal.

2-3. The economic benefit

[0091] the Economic benefit specified in table 2, an assessment is made taking into account the cost of raw materials, in which the Pd content of less than 0.05% and the EN content of 0.04% are denoted by "◯" (good), and the Pd content is from 0.05 to 0.15% is indicated by the symbol "∆" (satisfactory).

[0092] As shown in table 2, examples 4 to 19 of the invention provide economic benefits and exhibit high resistance to crevice corrosion and resistance to hot (boiling) hydrochloric acid. Examples 1-3 according to the invention was tested in hot (boiling) hydrochloric acid under the above conditions after the supply of cracks on the surface. The results of the test confirm that they have not suffered from the spread of corrosion originating on the cracks, and, thus, show a very high corrosion resistance. It was also found that all the titanium alloys according to the examples of the invention have machinability, machinability comparable to pure titanium of comparative example 7.

2-4. The study of changes in the concentration of Pd near the surface of a titanium alloy

[0093] the Study of the change of conc�tion Pd near the surface of the titanium alloy was carried out to example 8 of the invention and comparative example 5. Example 8 according to the invention and comparative example 5 have the same Pd content of 0.02%, but the example 8 according to the invention contains Y, and comparative example 5 no. As described above, after the test in hot (boiling) hydrochloric acid, the surfaces of these samples were studied in terms of profiles of the concentrations of Pd, Ti and O as a function of the distance inward from the surface, using GDOES method.

[0094] Fig. 7 and Fig. 8 are graphs showing the profiles of the concentrations of Pd, Ti and O as a function of distance from the surface of the titanium alloys shown in example 8 of the invention and comparative example 5, respectively. In the figures, the concentration of each element is indicated by the intensity measured by GDOES.

[0095] As can be seen from Fig. 7, in titanium alloy of example 8 according to the invention containing Y peak was observed, indicating the accumulation of Pd near the surface. On the other hand, as can be seen from Fig. 8, a titanium alloy in comparative example 5, which does not contain Y, no peak Pd was observed. As a result of these observations were obtained the following findings (1) and (2).

[0096] (1) it is Assumed that the presence of Y enables rapid dissolution of Ti and Pd at an earlier stage after exposure to a corrosive environment as compared to the case when Y is absent, which leads to an increased concentration of Pd ions in hot hydrochloric acid near the outer�arnosti titanium alloy. Thus, the deposition and accumulation of Pd on the surface of the titanium alloy is progressing rapidly, thereby allowing for a short period of time to displace titanium alloy generally in the direction of the passivation potential. Accordingly it is possible to believe that the titanium alloy formed with the metal of the platinum group and rare earth metal, will show the best resistance to hot (boiling) hydrochloric acid than titanium alloy formed with the metal of the platinum group, but not containing a rare earth metal.

[0097] (2) Comparison of concentration profiles of Ti in depth revealed the following. In titanium alloy according to example 8 of the invention the composition of the matrix alloy (almost 100% titanium) essentially is installed immediately under the layer of accumulation Of Pd on the surface throughout the alloy, except for the area of a depth of up to 120 nm from the surface. This indicates that the accumulation of Pd near the surface causes a shift of the titanium alloy as a whole to noble potential where is stably supported by the surface passivation. On the contrary, in titanium alloy in comparative example 5, the composition of the matrix alloy (almost 100% titanium) is essentially set throughout alloy, except for the area of a depth of up to 250 nm from the surface. This indicates that the corrosion was developing inside from the surface of napravlenie depth.

Example 2

[0098] In example 2 relating to the content of rare earth metal below 0.02%, conducted additional detailed study of the resistance to crevice corrosion and resistance to hot (boiling) hydrochloric acid.

1. The test conditions

1-1. Samples

[0099] the Elemental compositions of the titanium alloys in the examples according to the invention and comparative examples used in example 2 are shown in table 3. Of these, the alloys according to example 8 of the invention, comparative example 2 and comparative example 5 were also used in example 1.

[0100]

Table 3
ClassificationComposition of alloy (wt.%, the rest - Ti and impurities)Notes
Rare earth metalPlatinum group metalCo
comparative example 5-Pd:0,02-No REM
comparative example 2Y:4 ppmPd:0,02- REM: outside the specified range
example 20 according to the invention isY:11 ppmPd:0,02-
example 21 according to the invention isY:21 ppmPd:0,02-
example 22 according to the invention isY:40 ppmPd:0,02-
example 8 according to the invention isY:100 ppmPd:0,02-
example 23 according to the invention isY:190 ppmPd:0,02-
example 24 according to the invention isY:290 ppmPd:0,02-
example 25 according to the invention isMm:100 ppmPd:0,02-
example 26 according to the invention isY:50 ppmPd:0,020,5
example 27 according to the invention isY:40 ppmPd:0,01, EN:0,03-

[0101] All titanium alloys in examples 8 and 20-27 of the invention have a composition defined by the present invention. From their example 25 according to the invention contains Mm and Pd without other constituent elements, example 26 according to the invention contains Y, Pd and Co, example 27 according to the invention contains Y, Pd and Ru, other examples according to the invention contain Y and Pd without other constituent elements.

[0102] Titanium alloys in comparative examples 2 and 5 both have a composition defined by the present invention. Comparative example 2 contains Y and Pd without other constituent elements, and comparative example 5 contains Pd, but does not contain Y. In table 3, the symbol "-" indicates that the element content was below detection limits.

[0103] Comparative examples 5 and 2, and examples 20-22, 8, 23 and 24 according to the invention materials were used to study the effects of the content of rare earth metal (Y). Example 26 according to the invention is a material used to study the effects poluchaemyh case when the transition metal, and example 27 according to the invention is a material used to study the effects produced by the platinum group metals.

[0104] All titanium alloys, used in example 2 was prepared with the same materials and the same method as in example 1.

1-2. The test conditions

1-2-1. The test for resistance to crevice corrosion and test in hot (boiling) hydrochloric acid

[0105] In example 2 was carried out the test for resistance to crevice corrosion and test in hot (boiling) hydrochloric acid under the same conditions as in example 1.

1-2-2. The study of changes in the concentration of Pd near the surface of a titanium alloy

[0106] To investigate changes in the concentration of Pd near the surface of the titanium alloy used in the intensity, measured in example 1 GDOES method. On the other hand, in example 2, was built calibration curves dependence of the intensity on the concentration by analyzing pure Ti ASTM brand 17 (Ti-0,06 Pd), ASTM brand 7 (Ti-0,14 Pd) and pure Pd by GDOES method to calculate the approximate concentration of Pd on the surface of the titanium alloy. Because in addition to Pd, on the surface of the titanium alloy also detected Ti and O, in example 2, the concentration of Pd was adjusted so that the total content of Ti, O, and Pd was 100%.

[0107] For comparative �reamer 5, examples 20-22, 8, 23 and 24 according to the invention the analysis of each of them GDOES method was performed under the same conditions as those used in constructing the calibration curves and the concentration of Pd on the surface of the titanium alloy was calculated from the newly obtained calibration curves.

2. The test results

[0108] the evaluation was conducted on the number of slot places affected by corrosion, the average corrosion rate and economic benefits, as well as assessment on the basis of these factors. The results are shown in table 4. The alloys according to the examples according to the invention and comparative examples used in example 2, were all evaluated as good (◯) in respect to economic gain.

[0109]

Table 4
ClassificationResistance to crevice corrosionResistance to hot (boiling) hydrochloric acidEconomic benefits (accounting for the cost of materials)*2On top surface of concen-tion of Pd (%)
The number of slots affected by corrosion*1The average corrosion rate for the first 7 hours (mm/year)Sredneskorostnyh corrosion 96 hours (mm/year)
comparative example 5209,540,700,4
comparative example 215For 15.391,90-
example 20 according to the invention is03,210,291,2
example 21 according to the invention is02,140,221,9
example 22 according to the invention is02,010,133,4
example 8 according to the invention is04,400,272
example 23 according to the invention is0 3,610,281,5
example 24 according to the invention is03,840,30-
example 25 according to the invention is04,220,25-
example 26 according to the invention is02,210,15-
example 27 according to the invention is01,020,09-
*1Resistance to crevice corrosion: was estimated by the number of slit places affected by corrosion (the number of seats crevice corrosion of all slit 40 seats)
*2Economic benefit: the symbol "◯" indicates that the Pd content of less than 0.05%, or the EN content of 0.04%, and the symbol "∆" indicates the Pd content is from 0.05 to 0.15%

2-1. Resistance to crevice corrosion

[0110] In table 2 bring�Xia evaluation of the resistance to crevice corrosion, specify the number affected by corrosion spots from number 40 of annular seats formed mnogotselevye nodes. After the tests under the above conditions was that none of the examples according to the invention (examples 8 and 20 to 27 according to the invention) have not suffered from the effects of corrosion in any of the slit 40. Both comparative example 2 and 5 suffered from the effects of corrosion. From these results it is seen that Y must be present in an amount of about 10 ppm in order to achieve high resistance to crevice corrosion when the Pd content is 0.02%.

2-2. The test in hot (boiling) hydrochloric acid

[0111] In example 1, the examples according to the invention showed low corrosion rates, with average corrosion rates of 5 mm/year over the first 7 hours and 0.3 mm/year for 96 hours respectively. In example 2, we investigated the influence of the content of rare earth metal on average for 96 hours corrosion rate. Resistance to hot (boiling) hydrochloric acid closely associated with resistance to crevice corrosion.

[0112] Figure 9 is a graph showing the results of trials in hot (boiling) hydrochloric acid. Thus the graph of Fig. 9(a) shows the ratio between the average for 96-hours the corrosion rate and the content of Y, and the graph in Fig. 9(b) shows the ratio between the surface concentration of Pd after the test and provides�against Y. Fig. 9 shows the summary results for cases in which the content of Y was changed, and the Pd remained constant at the level of 0.02%.

2-3. Summary of test results

[0113] After studying the test results of example 2 were obtained the following conclusions(1)-(7).

[0114] (1) Cases that meet the established in the present invention the condition of "content of Y 0,001-0,10%", showed good resistance to hot (boiling) hydrochloric acid in 0.30 mm/year, estimated on average at 96 hours corrosion rate (Fig. 9(a)).

(2) Found that the preferred content of Y is in the range from 10 ppm to 200 ppm, in which the average corrosion rate is further reduced, and more preferably, the content of Y is from 20 ppm to 100 ppm.

(3) In the concentration range of Y is from 20 ppm to 100 ppm Pd surface concentration after the test was high (Fig. 9(b)).

(4) Example 24 according to the invention is a material having a content of Y 290 ppm, which is more than the solubility limit of Y in the solid state Ti of approximately 200 ppm. Example 24 according to the invention showed resistance to hot (boiling) hydrochloric acid 0.30 mm/year in terms of average for 96 hours corrosion rate. Although it is within the range of the present invention, as shown in example 1, it is the upper limit of the range. Approx�R 23 according to the invention with a content of Y, not to exceed the limit of solubility in the solid state, showed an average of 96 hours, the corrosion rate of 0.28 mm/year. From these results it follows that it is preferable that the content of Y does not exceed the limit of solubility in the solid state at 200 ppm.

(5) In the case where the transition metal is present, which is the essential element in patent documents 3 and 4, small average corrosion rate and thus high resistance to hot (boiling) hydrochloric acid are achieved when the content of Y is 50 ppm, which is not higher than the limit of solubility in the solid state (example 26 according to the invention).

(6) In the case when there is non Pd platinum group metal, small average corrosion rate and thus high resistance to hot (boiling) hydrochloric acid is also achieved when the content of Y is not higher than 200 ppm (example 27 according to the invention).

(7) In the case where there is different from Y, rare earth metal (example 25 according to the invention with 100 ppm Mm), small average corrosion rate and thus high resistance to hot (boiling) hydrochloric acid is also achieved when the content of the rare earth metal is not higher than 200 ppm.

[0115] From the actual data obtained in the above experiments, it was found that titanium alloys exhibit high corrosion resistance when the content of Y is from 0.001 to 0.10%, as set� by the present invention and even better corrosion resistance if the content of Y is limited to less than 0.02%.

Industrial applicability

[0116] the Titanium alloy of the present invention has high corrosion resistance and good machinability. Due to this, when using a titanium alloy of the present invention it is possible to improve performance and reliability of equipment and machines used in corrosive environments (in particular, in hot concentrated chloride environments). If the platinum group metal is contained in relatively small quantities, the invention provides the advantage of more economical material costs for these titanium alloys. If the platinum group metal is contained in relatively large quantities, the invention provides the advantage of smaller probability distribution of corrosion originating on the defects, such as appeared in the crack surface.

List of reference symbols

[0117] 1: sample, 2: mnogotselevoy node 3: bolt, 4: nut

1. Titanium alloy, characterized by the fact that it contains, in wt.%, platinum group metal, 0.01 to 0.15 and the rare earth metal is 0.001-0.10 and Ti and impurities - the rest.

2. Titanium alloy according to claim 1, characterized in that it contains Co as a partial replacement of Ti in an amount of 0.05-1.00 wt.%, and rare earth m�Tull is present in an amount of from 0.001 to less than 0.02 wt.%.

3. Titanium alloy according to claim 1, characterized in that the platinum group metal is present in an amount of 0.01-0.05 wt.%.

4. Titanium alloy according to claim 2, characterized in that the platinum group metal is present in an amount of 0.01-0.05 wt.%.

5. Titanium alloy according to any one of claims. 1-4, characterized in that as a platinum group metal alloy comprises Pd.

6. Titanium alloy according to any one of claims. 1-4, characterized in that the rare earth metal alloy contains Y.

7. Titanium alloy according to claim 5, characterized in that the rare earth metal alloy contains Y.



 

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SUBSTANCE: method to produce titanium blanks involves placement of titanium sponge particles in a press chamber, compaction of the sponge particles to produce a blank, its pressing, removal of dirt from the pressed blank surface, its covering with grease and following rolling. Prior to placing the titanium sponge particles in the press chamber they are heated in a vacuum heating furnace up to the temperature of 700-800°C, alloyed by hydrogen up to the concentration of 0.1-0.9 wt %, then the temperature in the furnace is reduced to the temperature not lower than 300°C, compaction is carried out under the temperature of 300-700°C, compacted blanks are pressed by semicontinuous method via a matrix under the temperature of not more than 700°C with reduction ratio of maximum two and then under the temperature of not more than 700°C and the reduction ratio of maximum three, the blanks are rolled under the temperature of not more than 700°C, with following annealing in vacuum under the temperature of not less than 700°C.

EFFECT: possibility to process hardly deformable titanium under lower temperatures, improved mechanical properties of produced blanks.

1 ex

FIELD: medicine.

SUBSTANCE: titanium aluminide alloy Ti3Al contains, wt %: Al 13-15, Nb 3-6, V 2-4, Zr 0.5-1.0, Mo 1-3, Sn 0.5-3, Si 0.1-0.3, Ti - the rest. A titanium aluminide alloy Ti3Al blank is subject to thermal hydrogen processing by hydrogen saturation followed by vacuum annealing. The hydrogen saturation of the blank is carried out to the concentration of 0.4-0.6 wt % at two stages, and then the blank is rolled. Vacuum annealing is two-staged at residual pressure no more than 5·10-5 mmHg.

EFFECT: heat-resistant titanium aluminide alloy Ti3Al is characterised by high plasticity and heat-resistance.

2 cl, 1 tbl

FIELD: metallurgy.

SUBSTANCE: proposed process comprises production of the mix of powders, forming the pellet therefrom and execution of self-propagating high-temperature synthesis. Obtained the mix of pure metals containing titanium, aluminium, niobium and molybdenum in the following amount, it wt %: aluminium - 40-44, niobium - 3-5, molybdenum - 0.6-1.4, titanium making the rest. This pellet is compacted to relative density of 50-85% and subjected to thermal vacuum processing at 550-560°C for 10-40 min, heating rate of 5-40°C/ min and pressure of 10-1-10-3 Pa while SPS is performed at initial temperature of 560-650°C.

EFFECT: preset shape of casts, high mechanical properties.

2 dwg, 2 tbl, 2 ex

FIELD: mechanical engineering; piston internal combustion engines.

SUBSTANCE: invention relates to valve of internal combustion engine, method of its manufacture and heat-resistant titanium alloy used for manufacture of valve consisting of following components, mass %: aluminum 7.5-12.5; molybdenum 1.6-2.6; zirconium 1.4-2.4; silicon 0.1-0.2' yttrium 0.005-0.1; titanium - the rest. It has α+α2+β phase composition with intermetallide α2 phase on Ti3Al base dispersed in α phase. Proposed method includes forming of valve from cylindrical blank by deformation machining with preliminary heating and subsequent heat treatment. Preliminary heating of part of blank related to rod done to temperature 5-20oC lower than temperature of complete polymorphic transformation of alloy, and its deformation machining is carrying out by wedge cross rolling. Deformation machining of part of blank related to head is done by forging with preliminary heating to temperature 5-50oC higher than temperature of complete polymorphic transformation of alloy corresponding to beginning of forging, and forging is finished at temperature lower than complete polymorphic transformation of alloy to form plate head of valve and transition section provided smooth changing of head into rod. Invention provides designing of valve, method of its manufacture and heat-resistant alloy used in manufacture of valve making it possible to operate valve within operating temperature range owing to increased long-term strength and creep resistant of valve head material and increased strength, modulus of elasticity and hardness of valve rod material.

EFFECT: improved quality of valve and increased reliability in operation.

16 cl, 3 tbl, 1 ex, 15 dwg

FIELD: powder metallurgy, namely sintered titanium base alloys used as constructional materials.

SUBSTANCE: sintered titanium base alloy contains, mass. %: aluminum, 5.5 - 7.0; zirconium, 1.4 -2.5; molybdenum,, 0.5 - 1.8; vanadium,, 0.8 -2.3; titanium, the balance. Alloy is prepared of powder of said content with particle size in range 0.5 - 3.0 micrometers. Structure of particles includes martensite α - phase and ω-phase with coherent dissipation range 300 - 600 Å. Percentage density of alloy - 99.6%. In structure of alloy there is no α2 - phase. Alloy is prepared by compacting under pressure 1200 Mpa, sintering at 1523 K for 3 hours in vacuum 0.0133 Mpa, annealing at 723 - 823 K for 1.5 hours and cooling together with furnace until room temperature.

EFFECT: enhanced mechanical properties of alloy.

FIELD: metallurgy, namely processes for forging titanium alloys and blank of such alloy suitable for forging.

SUBSTANCE: method comprises steps of preparing blank and forging it. Forging is realized at providing mechanical hardening factor equal to 1.2 or less and at difference of hardness values between central (along width) zone and near-surface zone equal to 60 or less by Vickers. Factor of mechanical hardening is determined as HV(def)/HV(ini), where HV(ini) - hardness of titanium alloy blank before forging; HV(def) -hardness of titanium alloy blank after forging at forging reduction 20%. Forging may be realized at deformation rate from 2 x 10 -4 s -1 to 1s-1 while keeping relations (T β - 400)°C ≤ Tm ≤ 900°C and 400°C ≤ Td ≤ 700°C, where Tβ (°C) -temperature of β-phase transition of titanium alloy, T m(°C) - temperature of worked blank; Td(°C) - temperature of die set. Blank has factor of mechanical hardening 1.2 or less and difference of hardness values between central (along width) zone and near-surface zone equal to 60 or less by Vickers.

EFFECT: possibility for forging titanium alloy blanks at minimum difference of material properties along depth, simplified finishing of blank surface after forging, reduced cracking of blank material, good workability of blank with favorable ductility and fatigue properties.

8 cl, 5 tbl, 6 dwg, 4 ex

FIELD: metallurgy.

SUBSTANCE: invention proposes titanium-base alloy and article made of thereof. Alloy comprising aluminum, molybdenum, vanadium, chrome, iron, zirconium, oxygen, carbon, hydrogen, nitrogen, copper and nickel comprises additionally silicon and tungsten in the following ratio of components, wt.-%: aluminum, 2.0-6.8; molybdenum, 1.0-3.5; vanadium, 3.0-6.0; chrome, 0.4-1.6; iron, 0.2-1.2; zirconium, 0.01-0.3; oxygen, 0.04-0.14; carbon, 0.02-0.1; hydrogen, 0.003-0.02; nitrogen, 0.005-0.05; copper, 0.001-0.1; nickel, 0.001-0.01; silicon, 0.02-0.15; tungsten, 0.001-0.03, and titanium, the balance. Invention provides the development of titanium alloys designated for making plane stringers, ribs, frames, fuselage, wings and engines and for applying as material for welding. Invention provides enhancing strength and crack-resistance of the basic alloy and welding joints and reducing article mass.

EFFECT: improved properties and quality of alloy.

3 cl, 2 tbl, 3 ex

FIELD: non-ferrous metallurgy; methods of titanium alloy bricks production.

SUBSTANCE: the invention is pertaining to the field of non-ferrous metallurgy, in particular, to the brick made out of α+β titanium alloy and to a method of its manufacture. The offered brick consists of the following components (in mass %): aluminum - 4-5, vanadium - 2.5-3.5, iron - 1.5-2.5, molybdenum - 1.5-2.5, titanium - the rest. At that the alloy out of which the brick is manufactured, contains - 10-90 volumetric % of the primary α-phase. The average grain size of the primary α-phase makes 10 microns or less in a cross-section plain parallel to the brick rolling direction. Elongation of grain of the primary α -phase is the four-fold or less. The offered method of manufacture of the given brick includes a stage of a hot rolling. At that before the stage of the hot rolling conduct a stage of the alloy heating at the surfaces temperature (Tβ-150)- Tβ°C. During realization of the stage of the hot rolling the surface temperature is kept within the range of (Tβ-300)-( Tβ -50)°C, and the final surface temperature, that is a surface temperature directly after the last rolling, makes (Tβ-300)-( Tβ-100)°C, where Tβ is a temperature of α/β-transition. The technical result of the invention is formation of a brick out of the high-strength titanium alloy having a super pliability, excellent fatigue characteristics and moldability.

EFFECT: the invention ensures production of a brick out of the high-strength titanium alloy having a super pliability, excellent fatigue characteristics and moldability.

7 cl, 7 dwg, 21 tbl, 2 ex

FIELD: nonferrous metallurgy; aircraft industry; mechanical engineering; development of alloys on the basis of titanium.

SUBSTANCE: the invention is pertaining to the field of nonferrous metallurgy, in particular, to development of alloys on the base of titanium, working at the heightened temperatures. It may be used in an aircraft industry for manufacture of components, for example, disks, vanes, rings, and also in mechanical engineering. The invention presents an alloy based on titanium and a hardware product produced out of it. The alloy contains aluminum, zirconium, stannum, niobium, a molybdenum, silicon, carbon and oxygen. At that it in addition contains tungsten and iron, at the following ratio of components (in mass %): aluminum 5.8 - 6.6, zirconium 2.0 - 4.0, stannum - 2.5 - 4.5, niobium - 0.8-2.5, molybdenum - 0.8- 1.5, silicon - 0.25-0.45, carbon - 0.05-0.1, oxygen -0.05-0.12, tungsten - 0.35-0.8, iron - 0.06-0.13, titanium - the rest. The technical result is a development of an alloy having the lower weight at the given short-time strength and a specific low-cycle fatigue, that increases an operational life and reliability of the components of the hot tract of aero-engines.

EFFECT: the invention ensures development of an alloy with the lower weight at the given short-time strength and a specific low-cycle fatigue with increased operational life and reliability.

2 cl, 2 tbl, 3 ex

FIELD: medicine; instrument-making industry; radio industry; production of materials with a memory effect of the form.

SUBSTANCE: the invention is pertaining to the materials with a memory effect of the form and with the modified surface, which may be used as implants in medicine and as the temperature sensors, thermo-sensitive and executive elements and designs in instrument-making industry, the radio industry. The offered material consists of a base made out of a titanium nickelide of the following composition (in at. %): titanium - 49-51, nickel - the rest, and the surface layer modified by alloying elements. The modified surface layer is formed by irradiation with a low-energy high-current electronic beam and has a depth of 1000-2500 nanometers and the dimensions of the crystal grains of no more than 30 nanometers. In the capacity of the alloying elements it contains oxygen and carbon at the following ratio of components (in at. %): oxygen - 10-20, carbon - 10-15, titanium - 40-50, nickel - the rest. The technical result of the invention is production of the materials with an effect of memory of the form and a high degree capability of the form restoration both at a low and high deforming loadings.

EFFECT: the invention ensures production of the materials with an effect of memory of the form and a high degree capability of the form restoration both at a low and high deforming loadings.

1 tbl, 1 ex

FIELD: metallurgy, in particular, titanium-based materials resistant to change of color.

SUBSTANCE: construction material of pure titanium contains, wt%: Fe 0.08 or less; Nb 0.02 or less; Co 0.02 or less, and is provided with surface oxide film having thickness of 170Å or less. Method involves producing material from pure titanium; etching and heating to temperature X( C) within the range of from 130 C to 280 C for time T (min) satisfying condition of T≥239408xX-2,3237.

EFFECT: increased resistance to change of color for prolonged time as compared to traditional materials.

3 cl, 2 dwg, 4 tbl, 3 ex

Titanium-base alloy // 2269584

FIELD: metallurgy.

SUBSTANCE: invention relates to titanium-base alloys used in making high-strength and high-efficient articles. Titanium-base alloy consists of aluminum, vanadium, molybdenum, iron and oxygen. Components of alloy are taken in the following ratio, wt.-%: aluminum, 3.5-4.4; vanadium, 2.0-4.0; molybdenum, 0.1-0.8; iron, max 0.4; oxygen, max 0.25, and titanium, the balance. Invention provides the development of universal alloy for large-sized forged pieces and stamps, thin-sheet roll and foil possessing the necessary strength and plastic indices and structure.

EFFECT: improved and valuable properties of alloy.

2 tbl

FIELD: metallurgy; high-strength alpha-beta alloys.

SUBSTANCE: Specification gives versions of titanium-based alpha-beta alloys. The proposed alloy contains the following components: aluminum, 4.5-5.5; vanadium, 3.0-5.0; molybdenum, 0.3-1.8; iron, 0.2-0.8; oxygen, 0.12-0.25; by-elements and admixtures, lesser than 0.1 each; total amount of by-elements and admixtures is lesser than 0.5; the remainder being titanium.

EFFECT: high strength of alloy, good workability and ballistic properties.

4 cl, 5 tbl, 3 ex

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