Method for obtaining nano-twinned titanium material by casting

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, namely to a method for obtaining technically pure nano-twinned titanium material. The method for obtaining technically pure nano-twinned titanium material involves casting of technically pure titanium material containing not more than 0.05 wt % N, not more than 0.08 wt % C, not more than 0.015 wt % H, not more than 0.50 wt % Fe, not more than 0.40 wt % O and the rest is not more than 0.40 wt %; cast material is brought to the temperature on the level of or below 0°C and plastic deformation is performed at this temperature in such a degree that nano-twins are formed in the material.

EFFECT: material is characterised by high strength and ductility characteristics.

15 cl, 6 dwg, 4 tbl, 4 ex

 

The technical FIELD

This invention relates to a method of producing commercially pure titanium material containing nanodevice.

The LEVEL of TECHNOLOGY

Titanium has a number of applications where highly valued to its favorable mechanical properties and its relatively low density. In some applications it is interesting to apply commercially pure titanium, instead of the commonly used alloys such as Ti-6Al-4V. This is particularly interesting in applications where the end product can have daily contact with human tissue, usually in the form of implants, as well as in other forms, such as jewelry, piercings and the like.

This is a consequence of the fact that the vanadium, which are often present in Ti-6Al-4V and other mechanically advantageous alloys, is toxic and allergenic, and is therefore not suitable to be contained in the materials that you want to use in the form of implants or in other similar applications. In addition, the biocompatibility of commercially pure titanium is usually better than the biocompatibility of other titanium alloys.

The problem, however, in that the titanium material with a low content of vanadium, such as, for example, commercially pure titanium, has a markedly lower yield strength and tensile strength than the corresponding alloys.

Therefore, there is the duty to regulate the need for titanium material with a low content of vanadium, usually technically pure (PM) titanium material with a relatively high yield strength and tensile strength than conventional PM titanium material, and preferably with continued high plasticity.

You can increase the strength of PM titanium material by introducing dislocations or by reducing the grain size. Typically, however, these methods lead to unwanted decrease of plasticity, which makes these materials are less suitable for most applications.

Recently it was proved that the introduction of nanojoining in metallic materials is an effective way to obtain materials with high strength and high ductility. All materials, however, are immune to this treatment. In addition, there is the usual operation, which nanodevice can be entered in the material. It has been shown that different methods cause the emergence of nanojoining in different materials.

The double can be defined as two separate crystal that share part of one of the crystal lattice. For nanodevice the distance between the individual crystals is less than 1000 nm.

Of non-patent document XP-002639666 known hardening of nanostructured titanium at high strain rates. This titanium material is prepared by equal-channel angular presova is I plus cold rolling. Therefore, this titanium material is sverhmedlennym titanium material. During the deformation process titanium material at high strain rates in this material is observed twinning.

The document US 2005/0109158 relates to a method of obtaining products of sverhmedlennogo titanium or titanium alloy. Coarse-grained titanium materials are strongly deformed mechanically in sverhseksualnoy powder when using cryogenic grinding. This method gives a material with improved mechanical properties.

However, there is no way to improve the strength of titanium, which is not molded from a powder, such as, for example, cast titanium.

The INVENTION

The purpose of this invention is to provide technically pure titanium material with improved strength and method of making such material. This is achieved by the present invention according to the independent claims.

This invention concerns a method of obtaining nanojoining technically pure titanium material, which contains steps:

- cast commercially pure titanium material other than titanium contains not more than 0.05 wt.% N, not more than 0.08 wt.% With not more than 0,015 wt.% N, not more than 0.50 wt.% Fe, not more than 0.40 wt.% Oh and not more than 0.40 wt.% the rest is,

- bring this material to a temperature at or below 0°C, and

- imparting plastic deformation to the material at this temperature to such an extent that the material formed nanodevice.

Experiments show that by performing these steps in the material entered nanodevice, and increasing the tensile strength and the yield strength of titanium material. This invention is not limited to any particular type casting, but is intended to cover all types of ways, where the base material is a powder. Therefore, this invention covers, among other things, continuous casting and cast shapes. In addition, deformation at low temperature can be performed at any time after casting. In the invention, the step of molding important to obtain a microstructure which is receptive to the other stages of the method of the present invention. Therefore, there are no restrictions on what deformation at low temperature must be done in accordance with the stage of casting.

In one embodiment of the present invention the deformation to give the material a with a speed of less than 2% per second, preferably less than 1.5% per second and more preferably less than 1% per second.

The relatively low strain-rate preferred because it keeps the temperature increase in Matera the ale on the regulated level. If the strain-rate is too high, the material temperature can rise and adversely affect the predictability of plastic deformation, such as education of nanojoining.

Preferably, the material is brought to a temperature below -50°C. or even more preferably -100°C before this material give the plastic deformation.

In one embodiment, the proposed method the material is cooled to a temperature of -196°C, for example, using liquid nitrogen before this material give the plastic deformation.

In one embodiment, the proposed method the plastic deformation give the material by compressing, for example, from rolling.

As an alternative or Supplement to compression plastic deformation may include stretching, which give the material a, for example, by extrusion. The material can be plastically deformed to an extent which corresponds to the plastic deformation of at least 10%, preferably at least 20%, and more preferably at least 30%.

In a special embodiment of the method according to this invention the plastic deformation give the material periodically with less than 10% deformation, preferably less than 6% for the deformation and more preferably less than 4% for the deformation is.

For the scope of this application periodically pulling means pulling perform steps. Between each of the stages load instantly reduced to less than 90%, or preferably less than 80% or 70% of the instantaneous load within a short period of time, preferably more than 1 second, more preferably more than 3 seconds, for example, from 5 to 10 seconds, before resuming the drawing.

In an additional embodiment of the method according to this invention the deformation to give the material a with a speed of more than 0.2% per second, preferably more than 0.4% per second and more preferably more than 0.6% in the second.

In an additional embodiment of the method according to this invention cast commercially pure titanium material contains not more than 0.01 wt.% H, and in another embodiment of the method according to the invention, this material contains not more than 0.45 wt.% Fe. In yet another embodiment, the cast commercially pure titanium material contains no more than 0,35% by weight Oh and preferably no more than to 0.30 wt.% O.

Using the proposed method are commercially pure titanium material with a relatively high strength. The average distance between nano-twins in the material provided by the method, is less than 1000 nm./p>

Preferably, this material has a distance between nanoscale twins less than 500 nm and more preferably less than 300 nm.

Thanks to the method of this invention, the material is preferably to obtain a yield strength above 700 MPa, preferably above 750 MPa and more preferably above 800 MPa.

In another preferred embodiment of the present invention, the material has a tensile strength higher than 750 MPa, preferably above 800 MPa and more preferably above 850 MPa.

BRIEF DESCRIPTION of DRAWINGS

Below the invention will be described in detail with reference to the accompanying drawings,

where Fig.1 shows a block diagram depicting the method according to this invention;

Fig.2 shows a graph depicting the voltage under tension from stretching for PM titanium material at different temperatures;

Fig.3 shows a microscopic image nanojoining PM Ti-material obtained according to this invention;

Fig.4 shows TEM study nanojoining PM Ti-material obtained according to this invention;

Fig.5 shows an image of x-ray diffraction nanojoining PM Ti-material obtained according to this invention; and

Fig.6 shows the measurement display misorientation in nonadvalorem mate is Yale, obtained according to this invention.

DETAILED DESCRIPTION

The present invention provides an improvement of commercially pure titanium materials and, in particular, the method of obtaining such materials.

Titanium exists in a number of brands of different composition. Titanium with composition, which corresponds to grades 1-4, usually called technically pure. Titanium with composition brand 5 commonly known as Ti-6Al-4V and is today the most widely used titanium material due to its very good mechanical properties.

The composition of the titanium materials grades 1-5 are summarized in table 1. Values show the maximum wt.%, if not given interval.

Table 1
The composition of the titanium of different brands (wt.%)
ONCHFeAlVOther
Mark 10,180,030,080,0150,2Mark 20,250,030,080,0150,30,4
Mark 30,350,050,080,0150,300,4
Mark 40,400,050,080,0150,500,4
Mark 50,200,050,080,0150,40of 5.5 to 6.753.5 to 4.50,4

As mentioned above, commercially pure titanium materials are very attractive in some applications, such as, for example, in the field of medicine, because they do not contain or contain things which are very small amounts of allergenic metal vanadium. The specific objective of the invention is to find a way to improve the mechanical properties, particularly the yield strength of the titanium material with the composition grades 1-4 to match the mechanical properties of titanium material, a composition of grade 5.

In General, commercially pure titanium materials strength of the material increases in proportion to the increase in oxygen content. Table 2 shows some typical mechanical properties of titanium grades 1-5 and grades 23, where Rp0,2 corresponds to the yield stress at a plastic strain of 0.2%, Rm corresponds to the tensile strength, And corresponds to the elongation (total elongation), and E corresponds to the young's modulus.

Table 2
Typical mechanical properties of titanium of different brands
Rp0,2RmAE
(MPa)(MPa)(%)(HPa)
Ti Mark 117024024102,7
Ti Mark 2 27534520102,7
Ti Mark 338045018103,4
Ti Mark 448355015104,1
Ti Mark 582889510110-114
Ti Mark 2377594816,4

According to this invention, it was shown that nanodevice can be entered in the commercially pure titanium material. It will be shown below in the four examples, of which perhaps the proposed generalization.

The compositions of the approximate four samples are shown in table 3.

Table 3
The compositions of the four approximate samples (Max. wt.%)
CompositionNCH FeOAlOther
PM Ti #10,030,060,010,10,19--
PM Ti #2, #30,050,060,010,20,225--
PM Ti #40,010,010,010,40,28--

From table 3 we can conclude that the first sample, i.e., PM Ti #1, has a composition which corresponds to titanium grade 2, and that the second and third samples, i.e., PM Ti #1 and #3 have a structure that corresponds to the titanium grade 3 due to the higher nitrogen content. The fourth sample refers to grade 4 due to the higher iron content.

In the four examples below, these samples were subjected to periodic pulling. For the scope of this application manual or periodic stretching of who appoints, that load instantly reduced to less than 90%, or preferably to less than 80% or 70% of the instantaneous load within a short period of time, for example, from 5 to 10 seconds to resume drawing.

It was proved that periodic plastic deformation is an effective way to increase full resistance to deformation, which can be achieved a higher full deformation than for continuous deformation.

In addition, to avoid increasing the temperature during extrusion, the material is continuously cooled during the whole drawing process.

The source material for the examples below is a rod-shaped material, which is obtained in the usual metallurgical method including melting, casting, forging/hot rolling and extrusion rod material.

Therefore, the proposed method can be performed on the product completed in a different way.

Example 1

In the first sample of PM Ti #1 was cooled to a temperature below -100°C and then plastically deformed at this temperature.

The sample, which had initial complete length of 50 mm, plastically deformed by tensile rate of 20 mm/min (0,67% per second) to complete the deformation of 35%. Deformation was performed at intervals of 2% during this time.

Example 2

In the second example, the sample of PM Ti #ohlidal to a temperature below -100°C and then plastically deformed at this temperature.

The sample, which had initial complete length of 50 mm, plastically deformed by stretching at a speed of 30 mm/min (1% per second) to complete the deformation of 35%. Deformation was performed at intervals of 2% during this time.

Example 3

In the third sample PM Ti #3 was cooled to a temperature below -100°C and then plastically deformed at this temperature.

The sample, which had initial complete length of 50 mm, plastically deformed by tensile rate of 20 mm/min (0,67% per second) to complete the deformation of 40%. Deformation was performed at intervals of 2% during this time.

Example 4

In the fourth sample of PM Ti #4 was cooled to a temperature below -100°C and then plastically deformed at this temperature.

The sample, which had initial complete length of 50 mm, plastically deformed by stretching at a speed of 30 mm/min (1% per second) to complete the deformation of 25%. Deformation was performed at intervals of 2% during this time.

After presents pre-tension at these temperatures, the samples #1-4 were left at room temperature for testing mechanical properties at room temperature.

The observed mechanical properties of the samples are presented in table 4.

From table 4 it is seen that the yield strength, and tensile strength was significantly increased for all four obrazovateljno respective comparative values for titanium materials grade 2 or 3. This increase in strength is due to the formation of nanojoining in the structure of these materials, which is caused by pre-stretching at a low temperature, so that they correspond to the properties of the comparative materials, or even higher, for example, titanium grade 5, and grade 23.

Table 4
Mechanical properties of samples compared to reference data
Rp0,2RmAεfZE
(MPa)(MPa)(%)(%)(%)(HPa)
Nanodosimetry PM Ti #181382919,413-1555120
Nanodosimetry PM Ti #28038181912-1456 116
Nanodosimetry PM Ti #3912117052
Nanodosimetry PM Ti #474782912,5107
Ti-6Al-4V (Ti Mark 5)828895106-7110-114
Ti Mark 2377594816,457

From the above examples it is possible to generalize the proposed method. In the next part of this detailed description the block diagram of the method of obtaining commercially pure titanium material according to this invention is described with reference to Fig.1.

At the first stage provide technically pure titanium material. According to this invention provided the material is cast, and not get the powder method, such as, for example, sintering and/or hot isostatic pressing (CIP).

Cast titanium material is cooled to a temperature below room temperature. As a General rule, the lower the temperature, the greater will be the effect of nanojoining.

In Fig.2 shows a graph of test tension titanium grade material 2. In this graph you can see a quick jump in voltage, followed by a stretch of jagged curves. These jagged curves show that twinning occurs. In addition, the graph in Fig.2 detects that the temperature at which perform the test tension, exerts a strong influence on the strength of the material, as well as in tension, in which there is a rapid surge. The lower the temperature, the less tension is required to cause a rapid surge and thus to begin the formation of twins.

From the graph it is also clear that the twins can be formed at a temperature of 0°C and below, although the formation of twins occurs only when extending approximately above 9% at 0°C.

In step 4, a block diagram of a material subject to plastic deformation before the formation of nanojoining in the material. The plastic deformation must be maintained to achieve a certain density of nanojoining or the distance between nanoscale twins" in the material. is then described in more detail below.

According to the shown examples, there is a wide range of compositions, in which nanodosimetry material with satisfactory mechanical properties can be obtained by plastic deformation at low temperature. In particular, it is clear that the oxygen content, which controls the strength titanium material without nanojoining should not be high for the formation of nanojoining. In the sample of PM Ti #1 the oxygen content is low, as to 0.19 wt.%, what is the limit of detection of titanium grade 1 (no more than 0,18%).

To test theory that the samples of PM Ti #1-4 indeed contain nanodevice, their corresponding microstructure was examined in a microscope with low magnification and TEM study.

Nanofountain pure titanium material has a microstructure filled with needles or paintings in the form of rails. These needles or Reiki shown at relatively low magnification in Fig.3. As can be seen, the needle or slats have the same crystal orientation within a specific cluster, but each cluster has a particular orientation, which does not depend on the neighboring cluster.

The density of nanojoining can be very high, as can be seen in the TEM study of Fig.4. In this case it is higher than 72%. The so-called "distance between nanoscale twins" for this material which is less than 1000 nm. For most doubles the distance between nanoscale twins is less than 500 nm, and especially less than 300 nm. In addition, most of the doubles is the distance between the nano-twins" above 50 nm.

Domains doubles do not apply across the grain, but rather divide it into smaller segments. The mutual orientation between grains is very weak and completely different crystallographic orientation of neighboring domains. From the image x-ray diffraction shown in Fig.5, a small additional points occur near most points, which is characteristic of the NDS-structure titanium. These additional points indicate the presence of twins.

Fig.6 shows the measurement display misorientation in nonadvalorem material PM titanium material. In this drawing uncorrelated peaks indicated by the numerical designation of 1, whereas the correlated peaks indicated by the numerical designation 2. Correlated peaks 2 follow random or theoretical line, which is indicated by the numerical designation 3. There are several uncorrelated peaks at approximately 9, 29, 63 and 69, 83 and 89. This misorientation is different from the misorientation of the normal PM titanium material, where there is only misorientation located at 60 and 85. Misorientation at 60 are of compression the m twinning and misorientation at 85 is created by tensile twinning. Misorientation at 32 is typically created 27 twinning. Misorientation of less than 10-20, created a special diskografie grain boundaries, which does not mean twins.

One assumption that can be made in respect nanofountain materials, is that the misorientation at 63 and 69 can belong to the same group (compression twinning) and misorientation at 83 and 89 may belong to another group (twinning under tension).

From TEM studies can, however, conclude that the twins are present, and that most of the domains doubles has a size of at least less than 1000 nm, so that they must be called nanojoining.

In this description shows four examples. However, other examples with similar characteristics were also obtained that supports the examples and the achieved mechanical properties. Thus, the invention is not limited to the given examples, and subsequent claims.

1. The method of obtaining nanojoining technically pure titanium material, characterized by the steps are:
- perform casting technically pure titanium material other than titanium contains not more than 0.05 wt.% N, not more than 0.08 wt. With, not more than of 0.015 wt.% N, not more than 0.50 wt.% Fe, not more than 0.40 wt.% Oh and not more than 0.40 wt.% other elements,
- lead the cast material to a temperature at or below 0°C, and
- hold the plastic deformation of the material at this temperature with the degree, providing education material nanojoining.

2. The method according to p. 1, characterized in that the conducting material deformation speeds of less than 2% per second.

3. The method according to p. 1, characterized in that the conducting material deformation speeds of less than 1.5% in the second.

4. The method according to p. 1, characterized in that the conducting material deformation speeds of less than 1% per second.

5. The method according to any of paragraphs.1-4, characterized in that the material is brought to a temperature below -50°C and hold the plastic deformation of the material at this temperature.

6. The method according to any of paragraphs. 1-4, characterized in that the material is brought to a temperature below -100°C and hold the plastic deformation of the material at this temperature.

7. The method according to any of paragraphs. 1-4, characterized in that the material is brought to a temperature below -196°C and hold the plastic deformation of the material at this temperature.

8. The method according to any of paragraphs.1-4, characterized in that hold the plastic deformation of the material by compression.

9. The method according to any of paragraphs.1-4, characterized in that the plastic Def rmacy includes stretching, which give the material stretching.

10. The method according to any of paragraphs.1-4, characterized in that the material is plastically deform to the extent which corresponds to the plastic deformation of at least 10%, preferably at least 20%, and more preferably at least 30%.

11. The method according to p. 10, characterized in that hold the plastic deformation of the material periodically with the degree of deformation less than 10% deformation, preferably less than 6% for the deformation, and more preferably less than 4% for the strain.

12. The method according to any of paragraphs.1-4, characterized in that conduct the deformation of the material at a rate of more than 0.2% in the second.

13. The method according to p. 12, characterized in that the conducting material deformation speeds of more than 0.4% in the second.

14. The method according to p. 12, characterized in that the conducting material deformation speeds of more than 0.6% in the second.

15. The method according to any of paragraphs.1-4, characterized in that the cast commercially pure titanium material contains not more than 0,35% by weight Oh, and preferably not more than to 0.30 wt.% O.



 

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1 dwg, 1 ex

FIELD: aircraft industry; mechanical engineering; methods of metals plastic working.

SUBSTANCE: the invention is pertaining to the methods of metals plastic working, in particular, to production of blanks for units of a gas turbine engine and may be used in production of aircraft engines and in mechanical engineering. The method includes heating of a high-temperature resistant alloy bar and its straining during several runs. For obtaining a homogeneity of the blank chemical composition and structure in the whole volume of the blank and for increasing the alloy mechanical properties during the blank subsequent machining at least one run is conducted at the temperature exceeding the temperature of the beginning of the alloy hardening inter-metallic phase dissolution. Then, they conduct a press forming in the interval of the temperatures from the temperature of a recrystallization process start to the temperature of the recrystallization process end for production of the uniform fine grained structure, that ensures a high level of general physical-mechanical properties of the blank and the item as a whole.

EFFECT: the invention ensures production of the uniform fine-grained structure and a high level of general physical-mechanical properties of the blank and the item as a whole.

2 ex

FIELD: non-ferrous metallurgy; methods of thermal treatment of items or blanks made out of the two-phase titanium alloys titanium alloys.

SUBSTANCE: the invention is pertaining to the field of metallurgy, in particular, to the method of thermal treatment of an item or blanks made out of the two-phase titanium alloys titanium alloys. The offered method of thermal treatment of an item or a blanks made out of the two-phase titanium alloys provides for their heating, seasoning and chilling. At that the item or the blank is heated up to the temperature of (0.5-0.8)tag , where tag is the temperature of the alloy aging, and chilling is conducted from -10 up to -20°С at simultaneous action of a gas current and an acoustic field of an acoustical range frequency with a level of the sound pressure of 140-160 dB. The technical result is the invention ensures an increased strength of items or blanks at keeping the satisfactory plastic properties.

EFFECT: the invention ensures an increased strength of items or blanks at keeping the satisfactory plastic properties.

7 cl, 1 dwg, 1 tbl, 1 ex

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: 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: processes and equipment for diffusion welding of tubular adapters of zirconium and steel sleeves.

SUBSTANCE: method comprises steps of placing sleeve of zirconium alloy inside steel sleeve and heating them in vacuum till diffusion welding temperature; then compressing welded surfaces due to expanding zirconium sleeve by means of roller expander; after diffusion welding cooling adapter in temperature range in which zirconium alloy has no phase containing α-zirconium and β-zirconium; subjecting zirconium sleeve to hot deformation by depth no less than 0.5 mm at reduction degree no less than 10%; cooling adapter till temperature range 540 - 580°C and keeping it in such temperature range no less than 30 min.

EFFECT: simplified method for making adapters having improved corrosion resistance in hot water and steam.

FIELD: plastic metal working, possibly manufacture of intermediate blanks of titanium alloys by hot deforming.

SUBSTANCE: method comprises steps of deforming ingot at temperature in β -range and combination type operations of deforming blank temperature of (α + β) and β-ranges; at final deforming stage at temperature in (α + β) range realizing at least one forging operation after heating blank till temperature that is lower by 50 - 80°C than polymorphous conversion temperature of alloy; at least one time cooling blank in water; before deforming blank for final size, heating blank till temperature that is lower by 20 - 40°C than polymorphous conversion temperature for time period providing globule formation of α - phase; fixing formed structure by cooling in water; again heating blank till temperature that is lower by 20 - 40°C than polymorphous conversion temperature and finally deforming blank.

EFFECT: possibility for producing blank with globular-plate microstructure, lowered level of structural defects at ultrasonic flaw detection of turned blank.

1 ex

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