Sheet of pure titanium with excellent balance between ductility and strength

FIELD: metallurgy.

SUBSTANCE: sheet is made from pure titanium and contains titanium and unavoidable impurities. It features yield point of 215 MPa or higher, mead size d of the grain making 25 mcm of larger and 75 mcm or smaller, and hexagonal crystalline structure. Appropriate grains in hexagonal crystalline structure feature means Schmidt factors (SF) of twins 11-22 with rolling direction oriented along their axes. Means Schmidt factor (SF) and grain means size d satisfy the following relationship: 0.055≤[SF/√d]≤0.084. Heat exchanger plate comprises sheet of pure titanium and as integral component.

EFFECT: high ductility and strength, heat exchange plate with such sheet.

2 cl, 6 dwg, 3 tbl

 

The LEVEL of TECHNOLOGY

The present invention relates to a titanium sheet (or plate)having an excellent balance between shtampuemostju and durability. More specifically, the present invention relates to a sheet of pure titanium, which includes pure titanium, the corresponding grade 2 prescribed in Japanese industrial standards (JIS) H4600 (2007), has a yield strength (the stress at which the residual strain is 0.2%), referred to hereinafter also referred to as strength, 215 MPa or higher, and is shtampuemostju.

Titanium, which has such unique properties as corrosion resistance, specific strength and lightness, was approved for use in many fields and applications such as eyeglass frames, wallets, cameras, housings, typically mobile devices, constructions, such as bicycles; parts exhaust systems, such as silencers motorcycles and cars, pipes and plate heat exchangers and the electrodes tanks chemical plants. It is expected that titanium is also approved for use in materials with improved properties, for example, separators for fuel cells.

Pure titanium, which is widely used in these applications prescribed in JIS H4600 and is divided into grade JIS 1, 2, and 3 depending on the content of impurities such as iron (Fe) and oxygen (O), and the t strength. With the increase of the number of brands increases the minimum strength of pure titanium, and in accordance with different purposes, use different brands of pure titanium.

One of the applications in which, for the most part used leaves of pure titanium that is a heat exchanger (TVET). The titanium sheets suitable for this application are usually subjected to cold pressing to obtain a complex corrugated shape to have a higher effective heat exchange surface to improve the efficiency of heat exchange. In particular, for stamping the sheets are subjected to conditions that are very harsh for the material. Pure titanium brand JIS 1, which is soft and most suitable for forming among all brands of pure titanium should be used in such harsh conditions stamping.

However, such a titanium sheet requires an even higher strength and better formemost, so as to improve the efficiency of the heat exchanger is achieved not only due to the form of the heat exchanger, but also usually due to the increased velocity of the fluid (or coolant), and this measure requires a higher tightness under pressure. However, the strength and stampability are inversely proportional, and it is a fact that still have not proposed a titanium sheet that job satisfaction is oral would both properties.

As methods improve stanoevska sheets of pure titanium was proposed method of control patterns titanium (publication of unexamined patent application Japan (JP-A) No. 2004-285457) and method of alloying titanium (publication of the patent application in Japan (JP-A) No. 2002-317234). However, these methods are aimed at improving formemost pure titanium has the strength (yield strength)corresponding to JIS brand 1, but not formemost pure titanium with a strength corresponding to the brand JIS 2. In particular, the main role in the deformation of pure titanium grade JIS 1 plays deformation twinning, but pure titanium with a strength corresponding to JIS brand 2, with low probability will be subjected to deformation twinning, and the formability is not improving, when methods for pure titanium grade JIS 1, apply to the brand 2 without modification.

As a method of improving stanoevska pure titanium, the strength of which corresponds to JIS brand 2, or brand JIS 3 (215 MPa or more), in publication of unexamined patent application Japan (JP-A) No. 2009-228092, a method of regulating the content of oxygen (O) and iron (Fe) and control the grain size of titanium. However, by simple adjustment of the contents of oxygen and iron and control the grain size of titanium is difficult to achieve a good balance between shtampuemostju and durability.

DISCLOSURE OF WHAT BRETANIA

The present invention was created in consideration of these circumstances, and its objective is to develop a sheet of pure titanium with a great balance between shtampuemostju and durability.

More specifically, the present invention is the creation of a sheet of pure titanium, which has a strength corresponding to the level of the brand JIS 2 (215 MPa in terms of yield strength) or above, and has an excellent stampability.

SOLUTION

In the present invention these objectives and a sheet of pure titanium containing titanium and inevitable impurities. A sheet of pure titanium has a yield strength of 215 MPa or higher. A sheet of pure titanium has an average grain size d of its structure 25 μm or more and 75 μm or less. A sheet of pure titanium has a hexagonal crystal structure, and the corresponding grain in the hexagonal crystal structure have an average value of the coefficients Schmidt (SF) doubles (11-22) with the rolling direction as the axes, and the average value of the coefficient Schmidt (SF) and average grain size d satisfy the following expression (1):

by 0.055≤[SF/√d]≤0,084(1)

The present invention provides a sheet of pure titanium with excellent balance m is waiting for shtampuemostju and strength, provided that the sheet of pure titanium has a coefficient Schmidt special to the plane of the grains and the average grain size that meet a specified criterion. The obtained sheet of pure titanium is very well suited as a material having satisfactory stampability and high strength, which are required when a sheet of pure titanium is used as the fitting of complex shape, usually in the heat exchanger or chemical plant. In particular, a sheet of pure titanium is suitable as the material for the plate heat exchanger.

BRIEF DESCRIPTION of DRAWINGS

Figa is a front view showing how to evaluate stampability;

FIGU is a schematic view in section along the line A-A' figa;

Figure 2 is a graph showing how the stampability depending on size (SF/√d) after use lubrication 1 in the working examples;

Figure 3 is a graph showing how the stampability depending on size (SF/√d) after grease 2 in the working examples;

Figure 4 is a graph showing how the stampability depending on size (SF/√d) after grease 3 in the working examples;

Figure 5 is a graph showing how the stampability depending on compression in the cold SOS is the right before the final annealing (final compression in a cold state); and

6 is a photograph illustrating the evaluation criteria test results stampability.

DESCRIPTION of embodiments of the INVENTION

As for formemost, it is known that a sheet of pure titanium has a more satisfactory stampability with increased propensity for twinning, as in addition to deformation by slip, a great contribution to the deformation of a sheet of pure titanium makes deformation twinning. The softer pure titanium, the more deformation twinning and the better stampability. For these reasons, the leaves of pure titanium with a strength corresponding to JIS brand 2, or brand JIS 3 (strength from more than 215 MPa to less than 485 MPa), are, as is well known, less deformation twinning and have the worst stampability than sheets of pure titanium with a strength corresponding to the brand JIS 1 (strength of 165 MPa or higher).

The authors of this invention have conducted various studies of the metal structure to improve stampability (especially stampability shaped parts of complex shape, such as plate heat exchanger), while maintaining a high level of strength (the strength of 215 MPa or higher), the corresponding JIS brand 2, or brand JIS 3, and made the following discovery.

Titanium sheet during cold rolling in one direction and batyvaet anisotropy strength and as a result has strength in the rolling direction below than the strength in the transverse direction with a low viscosity. When this titanium sheet is subjected to stamping (pressing), the deformation occurs mainly in the direction of rolling with low strength. Based on this, the authors of the present invention believe that the regulation of patterns to strengthen deformation twinning in the main direction of deformation, i.e. in the direction of rolling, effectively to improve stanoevska, and they found that for titanium sheets brand JIS 2 or grade 3 it is also important to align the orientation of the crystals, which facilitates deformation twinning.

The authors of the present invention have conducted studies of the coefficient Schmidt and grain size, which affect the presence of a tendency to deformation twinning, and found that control of the ratio between the coefficient Schmidt and grain size within a certain range allows you to get a sheet of pure titanium with the best shtampuemostju while maintaining a high level of durability. The present invention was made on the basis of these data.

More specifically, a titanium sheet having a particularly good stampability while maintaining a high level of durability appropriate stamp 2 or stamp 3 according to JIS can be obtained if the sheet of pure titanium, which was laminated in the same direction and which has a g is xianling crystal structure, the average value of the coefficients Schmidt (SF) and average grain size (d in μm) in the structure of the titanium sheet satisfy the condition represented by expression (1), i.e. by 0.055≤[SF/√d]≤0,084, where 25≤d≤75, hereafter referred to as the expression (1). The Schmidt coefficients reflect the deformation twinning with the rolling direction as the axes in the plane of the (11-22) hexagonal crystal structure.

The crystallographic plane (crystal face) are denoted by the Miller indices. When an index is negative, it is usually indicated by numbers with a line over it. However, in the present description, such a negative index for convenience referred to as the "negative number". Accordingly, the designation of "-2" for a plane, (11-22) indicates that this index is negative.

In the present invention as an indicator of improvement of stanoevska is factor Schmidt. It is known that the magnitude of the critical stress-slip (τ)required for the movement of dislocations along the crystallographic plane, usually varies depending on the crystallographic plane and the axis direction of the crystal and is given by the expression: τ=σcosφ·cosλ, where σ denotes tensile stress in the direction of the axis; φ represents the angle formed by a line normal to the slip plane, and the axis of tension, and λ denotes Hugo settled between the sliding direction and the axis of tension.

Multiplier [cosφ·cosλ] in the expression (1) is called the coefficient of Schmidt and indicates the inclination of the crystal axis of stretching. Accordingly, the critical voltage slip (τ)required for plastic deformation of polycrystalline metal varies depending on the ratio of Schmidt [cosφ·cosλ], and when the metal sheet is applied external force, the first deformed crystallographic plane having the maximum coefficient Schmidt.

In a sheet of pure titanium critical voltage slip (τ)required for the deformation of the crystal can be determined by calculating the average coefficient Schmidt (SF) on the basis of the ratio between the angle φ and the angle λ.

The crystal grain (main phase α) pure titanium has a structure with a hexagonal close-Packed lattice. It is known that, when pure titanium has the strength of corresponding stamp JIS 1, deformation twinning is most likely to occur in the plane of the (11-22) of the crystal grain. The authors of the present invention have confirmed that the sheet of pure titanium with a strength corresponding to grade 2 or 3 according to JIS has the best stampability, the higher the gain Schmidt in the plane, (11-22) of the crystal grains in the rolling direction (the direction of the axis of stretching). On the basis of these data in the crust the present invention as a secondary factor Schmidt (SF) used value for a plane, (11-22) of the respective crystal grains with the rolling direction as the axes in the hexagonal crystal structure titanium sheet.

In the present invention the range of the average coefficient Schmidt (SF) is not critical as long as the ratio (SF/√d) average coefficient Schmidt (SF) to the square root of the average grain size (d) is within certain limits (0,055≤[SF/√d]≤0,084), as in expression (1). A sheet of pure titanium, which has an average coefficient Schmidt (SF) satises the above may be satisfactory formability regardless of the conditions of lubrication.

In the present invention a sheet of pure titanium should have an average grain size of titanium (d in μm) 25 μm or more. A sheet of pure titanium with an average grain size less than 25 microns unlikely deformation twinning and can have the worst stampability due to insufficient voltage at the grain boundaries, and this voltage is necessary for deformation twinning. Therefore, a lower limit of the average grain size of titanium 25 μm. A sheet of pure titanium preferably has an average grain size of 30 μm or more, more preferably 35 μm or more.

If titanium sheet is too large average grain size, it may have structural defects (bad appearance) because of the "orange peel", which is formed on its surface, and may experience cracking from grain boundaries after molding (profilirovav the Oia) due to coarsening of crystal grains and the stress concentration at the grain boundaries. For these reasons, it is desirable that the sheet of pure titanium had an average grain size of 75 μm or less, preferably 65 μm or less, more preferably 55 μm or less.

The ratio between the average coefficient Schmidt (SF) and average grain size (d in μm) is defined through the ratio SF/√d, that is, as the average coefficient Schmidt (SF)divided by the square root of the average grain size (d). The average coefficient Schmidt (SF) divided by the square root of the average grain size (d), as the frequency of occurrence of deformation twinning, which affects stampability, can be expressed by the orientation of the crystals, i.e. the "SF", and the value of the internal voltage, which causes deformation twinning. The magnitude of the internal voltage is inversely proportional to the square root of the average grain size (d in μm). You may find that a sheet of pure titanium, which has the relation [SF/√d] less to 0.055, has no satisfactory stanoevska, as it has a large grain size and deformation twinning occurs in random directions. So [SF/√d] is the lower limit value 0,055 or more, preferably it is 0,058 or more, more preferably 0,061 or more. On the contrary, a sheet of pure titanium, which [SF/√d] exceeds 0,084 may have insufficient stampability, that is how the grains are too small, that creates a lack of internal stress at the grain boundaries, and therefore, deformation twinning is difficult. For these reasons, the value of [SF/√d] here is the upper limit 0,084 or less, preferably is of 0.081 or less, more preferably 0,078 or less.

A sheet of pure titanium according to the present invention is designed to have a composition of approximately corresponds to the composition used in industrial pure titanium (mark 2 or mark 3 prescribed in JIS H4600). Accordingly, a sheet of pure titanium preferably has a chemical composition to meet the chemical composition prescribed for the grade JIS 2 or marks JIS 3, and has the strength (yield strength) 215 MPa or more. The present invention is applicable also to the leaves of pure titanium defined in other standards, such as standards of the American society for testing and materials (ASTM), the relevant brand JIS 2 or Marche JIS 3. In particular, common examples of sheets of pure titanium, which applies the present invention include mark 2 according to JIS H4600 (2007) (N: 0.03 wt.% or less, C: 0.08 wt.% or less, H: of 0.013 wt.% or less, Fe: 0.25 wt.% or less, and O: 0.20 wt.% or less, the rest of the Titan), JIS mark 3 (N: 0.05 wt.% or less, C: 0.08 wt.% or less, H: of 0.013 wt.% or less, Fe: 0.30 wt.% or less, and O: 0.30 wt.% or less, else Ti), grade 1 according to ASTM B265 (N: 0.03 wt.% or less, C: 0.08 wt.% or less, H: of 0.015 wt.% or less, Fe: 0.20 wt.% or less, and About: 0.18 wt.% or less, else Ti), and mark 2 of the same standard (N: 0.03 wt.% or less, C: 0.08 wt.% or less, H: of 0.015 wt.% or less, Fe: 0.30 wt.% or less, and About: 0.25 wt.% or less, else Ti). However, it should be noted that these marks are given for example only and should not be interpreted as limiting the scope of the present invention.

Below is illustrated a method of obtaining a sheet of pure titanium according to the present invention. However, it should be noted that the leaves of pure titanium according to the present invention is not limited to leaves, obtained in the following way.

To obtain pure titanium present invention can apply the usual way in which the production conditions are not limited, except that the required conditions of cold rolling and annealing such as specified below.

A sheet of pure titanium are usually produced by sequential processes of casting, rolling on the blooming mill, hot rolling, annealing after hot rolling, cold rolling, process annealing (intermediate annealing, cold rolling and final annealing.

Usually, pure titanium with controlled special composition is usually subjected to the casting in ingots/forging, so he had desired shape (for example, the form of blocks), and subjected to hot rolling to obtain a hot rolled sheet. The obtained hot-rolled sheet is sequentially subjected to annealing, leaching acid for descaling, cold rolling and annealing, and the result is a sheet of pure titanium according to the present invention.

Of these processes to obtain a sheet of pure titanium according to the present invention, the important processes (stages) are cold rolling immediately before final annealing and final annealing, and their conditions are important for control of the middle coefficient Schmidt (SF) plane, (11-22) and the average grain size (d) and to control values [SF/√d] in the above defined limits.

To control SF authors of the present invention have conducted studies of the relationship between SF and compression in a cold state and found that the cold rolling, which is held to the degree of compression in a cold state, 68% or more, provided that the orientation of the crystals, which makes them amenable to deformation twinning, i.e. allows to have a high SF, and it provides satisfactory stampability. With increasing compression (reduction in cross-section) during cold rolling of SF increases, and stampability even more improved. Accordingly, cold car is and is conducted to the degree of compression is preferably 70% or more, more preferably 80% or more. The upper limit of compression is not limited and may be increased until the marginal reduction in cold rolling.

Although the details of this remain unclear, probably connected with the following. If cold rolling is carried out until the degree of compression in the cold state is less than 68%, the cold rolling deformed predominantly of crystalline grains having high coefficients Schmidt before cold rolling, the recrystallized grains in this zone are relatively small. On the contrary, the crystal grain with low coefficients Schmidt resist deformation, so they don't feel recrystallization annealing and tend to remain relatively large crystal grains. Still grains that have undergone deformation, tend after recrystallization to form a crystal grain with high rates Schmidt. Usually during the growth of polycrystalline grains of a large grain captures small grain, forming a coarse grain, for these reasons, the grain having a lower coefficient Schmidt (but larger), may, at the annealing to capture the grain having a higher coefficient Schmidt (but with a smaller size), which leads to a low average coefficient Schmidt (SF). On the contrary, when there is intense cold p is Okada to the degree of compression of 68% or more, even crystal grain with a low coefficient Schmidt deformed largely and as a result forms the annealing of small recrystallized grains, and the newly formed crystal grains having a high coefficient Schmidt, resulting in high average coefficient Schmidt (SF). On the other hand, the crystal grain having a high coefficient Schmidt, gradually deformed from the early stages of rolling, is the strain that is accumulated in large quantities, and preferably increases during grain growth after recrystallization, namely, a crystal grain with a high coefficient Schmidt captures crystal grain with a low coefficient Schmidt, and this allows the sheet of pure titanium having a high average coefficient Schmidt (SF), thereby providing improved stampability. It is the opinion of the authors of the present invention.

As used here, the term "compression in a cold state (compression during cold rolling) applies only to compression during cold rolling immediately before final annealing (final annealing). Although in the present invention, the cold rolling, if necessary, may be carried out several times, on average coefficient Schmidt (SF) affects mainly the compression on the final cold is th rolling, and this is only the compression on the final cold rolling.

According to the present invention, after carrying out cold rolling to a reduction of 68% or more is the final annealing (final annealing). The grain size and orientation of crystals of titanium can properly be controlled by adjusting conditions such as the temperature and the dwell time at the final annealing.

The rate of temperature rise during annealing can appropriately be adjusted, but preferably it is 20°C/s or higher, more preferably 25°C or higher, since the annealing is conducted at a very low rate of temperature increase, may not provide the orientation of the crystals, suitable for stamping.

It is desirable to properly control the temperature of annealing, as it affects, for example, on the grain size. If the annealing is conducted at a temperature is too high, it can lead to a large number of beta-phase, and therefore titanium sheet may be insufficient stampability. To avoid this, it is desirable that the annealing temperature was preferably 880°C or less, more preferably 860°C or less. On the contrary, if the annealing is carried out at too low a temperature, it may not provide the desired grain size. Therefore, the temperature of annealing is preferably SOS which defaults to 750°C or above, more preferably 800°C or higher. However, if the annealing is carried out at a temperature below the specified range, the size of crystal grains can be controlled within specified above range, if you carry out annealing for a long period of storage. However, from a performance perspective, it is desirable to carry out the annealing at a temperature within a predetermined higher temperature range.

The dwell time at the temperature of annealing is preferably 1 minute or more and 10 minutes or less. If you carry out annealing at a very short time, it may not provide crystal grains of the desired size. On the contrary, if the annealing is carried out for too long time, this can lead to performance degradation and to an excessively large grain size, thus being undesirable. More preferably, the exposure time is 2 minutes or more and up to 6 minutes or less.

The final annealing can be performed at the air, as well as in any environment, without limitation, for example in vacuum or in an atmosphere of inert gas such as argon.

To obtain the average grain size in the desired range, the annealing can be repeated several times for grain size control.

Using the appropriate combination of the reduction in cold rolling the right near St the public before final annealing and conditions subsequent final annealing, as mentioned above, you can get a sheet of pure titanium according to the present invention, having high strength and excellent formability.

Methods of coating a titanium sheet lubricating oil or formation of lubricant film on the surface of the titanium sheet is known. These methods are carried out to ensure satisfactory stampability for stamping. According to these methods, the titanium sheet is deformed along the stamp to be thereby improved stampability due to the action of oil for the press or by the action of the lubricant film formed on the surface of the titanium sheet. A sheet of pure titanium according to the present invention mainly manifests satisfactory stampability and without application of the above lubricant film. However, if necessary, on the surface of the titanium sheet may be formed of a film with a high lubricating ability. A sheet of pure titanium subjected to such a process lubricant, can have a more satisfactory stampability.

Typical methods of lubrication include a method of coating titanium sheet lubricating oil, such as oil presses, a method of coating the surface of the titanium sheet film, such as polyethylene film, and a method of coating the surface of the titanium sheet with an organic resin containing VI is m, for example, polyurethane resin or polyolefin resin. In such lubricating film can add inorganic solid lubricant oxide of silicon.

Titanium sheet according to the present invention is suitable as a typical material for heat exchangers and chemical plants, and is particularly advantageous as the material for plate heat exchangers. Titanium sheet according to the present invention differs satisfactory shtampuemostju, when used as such material. Titanium sheet can have any non-critical thickness, but if the titanium sheet is too thick, it may impede the processing of the titanium sheet. For these reasons, titanium sheet according to the present invention preferably is a sheet having a thickness suitable for the desired application, and is suitable, for example, titanium sheet with a thickness of 2 mm, although the exact upper limit of the thickness here is not defined. The lower limit of the thickness can also be determined, usually with the necessary strength. Titanium sheet according to the present invention, having high strength, can be approached sufficiently even when the thickness of 0.1 mm

A sheet of pure titanium for use in the present invention includes titanium and inevitable impurities. As used here, the term "inevitable impurities" refers the I to the impurity elements, inevitably contained in the raw material sponge titanium. Typical examples of such impurities include oxygen, iron, carbon, nitrogen, hydrogen, chromium and Nickel. In addition, examples of the inevitable impurities include elements which can be introduced into the product during manufacturing processes, such as hydrogen.

Although this is not critical, the content of inevitable impurities present in the titanium sheet, preferably a suitable way to reduce because of the high content of impurities can interfere with the manufacturing environment, preferred in the present invention, namely, they can interfere with the cold rolling before the final annealing to the degree of compression in a cold state, 68% or higher at normal production of the rolls.

Usually, basic oxygen effectively allows a titanium sheet having satisfactory strength. So oxygen could show such effects, the oxygen content should be 0,06% or more (percentage calculated on the weight (wt.%), the same is true in terms of chemical composition), more preferably of 0.08% or more. However, titanium sheet with a too high oxygen content may be too high strength and may have insufficient capacity to cold working and/or stampability. For these reasons, the desired content is the oxygen is 0.3% or less, preferably of 0.2% or less, more preferably 0.15% or less.

Elemental iron, and oxygen, effectively allows a titanium sheet having satisfactory durability and can be contained in the titanium sheet in accordance with the need to complement the strengthening effect of oxygen. However, if there is a too high content of iron, it can lead to too high strength titanium sheet and thereby to lack the ability to cold working and/or stanoevska and low resistance to crevice corrosion. To avoid this, it is desirable that the iron content was of 0.50% or less, preferably of 0.35% or less.

Elemental carbon as well as oxygen to iron, which is effective for providing strength titanium sheet. However, if the titanium sheet is too high carbon content, it may be too high strength and thus may have insufficient capacity to cold working and/or stampability. To avoid this, the carbon content is preferably 0.05% or less, more preferably of 0.03% or less.

Below the present invention will be illustrated in more detail on several working examples. However, it should be noted that these examples should not be construed as limiting the volume of the crust is asego invention; can be made various changes or modifications not beyond the nature and scope of the invention, and assumes that all such changes and modifications are covered by the nature and scope of the invention.

Materials for testing, each 3.5 mm thick, was obtained by exposing sheets of pure titanium (thickness 200 mm) with chemical compounds 1-3 (JIS H4600), listed in table 1 below, hot rolling (rolling: rolling at 830°C thickness of 200 mm to a thickness of 4.0 mm), annealing and acid leaching (acid washing: 250 μm on one side).

Materials received for testing was sequentially subjected to annealing after hot rolling (see table 2), the first cold rolling and technological annealing (see table 2). Then the samples were subjected to a second cold rolling (up to the degree of compression, specified in column Compression in a cold state before the final annealing in table 2) and the result obtained cold-rolled material having a thickness of 0.6 mm cold-Rolled materials were subjected to final annealing in air (the average rate of temperature rise of about 20°C/s, the annealing temperature and exposure period when the annealing temperature indicated in table 2) and acid washing (processing salt: 50 μm on each side), and the received samples (sheet thickness 0.5 mm).

Regardless of what t was prepared with the reference sample (sample A), chemical composition (chemical composition 2 in table 1) and the strength that match grade 2 according to JIS.

On the respective samples of the following ways were measured average grain size (d), the average coefficient Schmidt (SF), stampability and strength, the results are shown in table 3.

(1) Average grain size (d in μm)

The average grain size (d) of each sample was determined in accordance with the method section using the optical microsemi each sample at magnification of 100 times. The determination was conducted on the cross section in the rolling direction of the sample in any position across the thickness (0.5 mm) in the field of 0.7 mm in the rolling direction.

(2) the Average coefficient Schmidt (SF)

The average coefficient Schmidt (SF) in the plane (11-22) hexagonal crystal with the rolling direction as the axis of elongation was determined as follows. Measured the Schmidt coefficients of the respective crystal grains in an area with a size of 1.8 mm long, 1.8 mm wide, and deep at one-fourth the thickness (t/4, where t means the thickness) in accordance with the analysis of the orientation of the crystals using electronography backscattering in increments of one-tenth the size of the crystal grain, and the average value of the coefficient Schmidt for the respective crystal grains was defined is but as the average coefficient Schmidt (SF).

(3) Stampability (evaluation)

Figa and 1B are explanatory drawings showing how to evaluate stampability. Cooked above samples by stamping (pressing), using the 80-ton oil hydraulic press, received the pressed samples, each of which simulates heat exchange link plate heat exchanger. All extruded samples were the same size 160 mm in width and 160 mm in length (estimated size: 100 mm in width and 100 mm in length) and a drawing of a tree with six ridges in increments of 10 mm, a maximum height of 4 mm and 6 radii of curvature R is equal to 0.4, and 0.6, and 0.8, and 1.0, 1.4 and 1.8 mm, and these six crests had six different radii of curvature R, respectively. The stamping was carried out in the conditions: rate of 1 mm/sec, the pressing depth (penetration depth) of 3.4 mm, maximum load 200 kN and the coating weight of the lubricant 1.0 g/m2. For lubrication used any of the following greases 1-3.

Grease 1 (film): polyethylene film.

Grease 2: oil press (SUNPRESS S-304, comes Sugimura Chemical Industrial Co., Ltd.

Grease 3 (film): lubricant film containing 80 wt.% acrylic resin, 10 wt.% colloidal silica and 10 wt.% polyethylene wax.

Cracking of the pressed samples were measured in twenty-four points of intersection of the ridges and the dotted lines (twelve-point is at the edges of the ridges (convexity) and twelve points in the centers of the ridges (6 convexity and concavity 6)), as shown in figa and 1B, and figa is a top view, and FIGU - transverse incision.

Each of the measured points relative to the line A-A', line B-B' and line C-C', serving as a place of cracking was evaluated by visual observation, and were given 4 points, when the sample had no defects; 3 points when the sample had a tendency to the formation of the cervix (the phenomenon of necking); 2 points when the sample had education cervix; 1 point when the sample had a hairline crack; and 0 points when the sample had a large crack (see the following expression (2)). The state of cracking converted into a numerical value, dividing the points on the corresponding radii of curvature R (here they are all marked as R(ij)), and the ratio of this value to the value obtained under the assumption that all measured points had no cracks, has been defined as "the assessment" (according to the expression (3)). This score is used in the present invention as an indicator to assess stanoevska.

E(jj)=(no of defects: 4, the tendency to crack formation: 3, the formation of a neck: 2, hairline crack: 1, a large crack: 0) (2)

Score =[E(ij)/R(i j)]/[4/R(ij)]×100(3)

As shown in Fig.6, "the tendency to the formation of the neck" refers to such a state, when the formation of a neck not recognized by visual observation, and examination with touch sensors; "the formation of a neck" refers to such a state, when the thinning of the sample is determined by visual observation; "hairline crack" refers to a crack formed in the deformed area; and "big crack" refers to a crack size of 3 mm or more.

(4) Strength (MPa)

The strength was determined by taking the sample as prescribed in ASTM, and measuring the voltage plastic flow (yield strength) of the sample in the longitudinal (L) direction (rolling direction) in accordance with the methods of tensile tests of metallic materials prescribed in the ASTM standard E8. Test the stretching was performed at a rate of 0.5%/min at the beginning of the test until the strain of 0.5% and at a speed of 40%/min after that.

Table 1
RoomChemical composition (wt.%)
OFeC
Chemical composition 10,094%0,051%0,006%
Chemical composition 2of 0.081%by 0.055%0,008%
Chemical composition 30,101%0,057%0,006%
*Inevitable impurities other than O, Fe and C, lie within prescribed in JIS grade 2.
*The rest of the titanium

Table 2
SampleChemical composition
No.
Conditions of annealing after hot rollingThe first compression in a cold state (%)Conditions of intermediate annealingCompression cold lane is d final annealing (%) Conditions final annealing
Temperature (°C)Time (min)Temperature
(°C)
Time (min)Temperature
(°C)
Time (min)
128003---82,98001
238003---82,98002
318003---82,98003
41800 3---82,98006
528003---82,97502
638003438003708002
A27503578003607500,8
B18003---82,9 74015
C28003578003608006
D18003---82,97003
E28003578003607506
F38003688003508002
G3800 3748003308002
H38003808003108002

Table 3
CategorySampleThe average grain size d (μm)The average coefficient Schmidt SFSF/√dScore (%)
grease 1
Score (%)
grease 2
Score (%)
grease 3
Yield strength (MPa)
Example130,80,430,07783,063,072,8233
When the er 236,90,440,07286,364,275,8229
Example348,90,440,062to 83.563,274,2223
Example464,50,450,05677,1to 58.166,9220
Example5250,410,08379,859,369,2235
Example6to 45.40,410,06180,059,2 68,1229
Comparative exampleA22,00,400,08574,055,265,1230
Comparative exampleB72,30,450,05374,554,664,1220
Comparative exampleC67,50,410,04972,453,462,2219
Comparative exampleD180,360,08671,351,059,9243
Comparative exampleE 60,20,380,04968,247,957,3232
Comparative exampleF470,360,05373,253,258,7238
Comparative exampleG460,360,05372,052,6of 56.4251
Comparative exampleH50,70,350,04971,051,256,2250

Table 3 shows that the samples 1-6, satisfying conditions (SF/√d and d)defined in the present invention, had a strength (conditional limits yield) 215 MPa or higher, which corresponds to JIS brand 2, and had a satisfactory stamp is resistant.

In contrast, samples A-H, with values SF/√d is outside the range defined in the present invention, had the worst stampability, although they had the strength of 215 MPa or higher.

In particular, the data for samples C, E, F, G and H show that titanium sheets, subjected to cold rolling before the final annealing is carried out to low compression in a cold state (compression), usually had very high average coefficient Schmidt (SF), but had a large average grain size and therefore were likely to have lower stampability, because the value of SF/√d lying outside the range defined in the present invention.

Data on A sample show that titanium sheet, if it is subjected to final annealing in a short time, does not have sufficient grain growth, and if it is subjected to cold rolling before the final annealing to low compression in a cold state, does not have a high enough average coefficient Schmidt and tend to have the worst formability, since the value of SF/√d lies outside of the range defined in the present invention.

Data for sample B shows that titanium sheet, if it is subjected to a final annealing for excessive time, even at a low temperature, is experiencing excessive grain growth, respectively, it has kudsi the balance between SF and the average grain size and tend to have the worst stampability, because the value of SF/√d lies outside of the range defined in the present invention.

Sample D is a sample that was subjected to final annealing at an excessively low temperature, and suffers from a lack of grain growth and insufficient grain size.

2 to 4 are graphs showing how the stampability depending on the conditions of lubrication. The data shown in figure 2-4 shows that the leaves of pure titanium according to the present invention, satisfying the condition on SF/√d, have a higher shtampuemostju than the reference titanium sheets brand JIS 2 (sample A) under any conditions lubrication (grease 1-3). 2, 3 and 4 are graphs relating to the use of grease 1 grease 2 and lubrication 3, respectively.

Figure 5 is a graph showing how changes stampability depending on compression (final compression in a cold state) during cold rolling before the final annealing using lubrication 1. Figure 5 shows that titanium sheets, subjected to final cold rolling to a high compression, are the best stampability than the reference titanium sheets brand JIS 2 (sample A).

1. A sheet of pure titanium containing titanium and inevitable impurities, with
a sheet of pure titanium has a yield strength of 215 MPa or higher
a sheet of pure Titus is and has an average grain size d of its structure 25 μm or more and 75 μm or less, and
a sheet of pure titanium has a hexagonal crystal structure, and the corresponding grain in the hexagonal crystal structure have an average value of the coefficients Schmidt (SF) doubles (11-22) with the direction of rolling as their axes, and the average rate of Schmidt (SF) and average grain size d satisfy the following expression (I):

2. Plate heat exchanger containing a sheet of pure titanium according to claim 1 as a component.



 

Same patents:

FIELD: heating.

SUBSTANCE: heat exchange system with a heat exchanger comprises inlet and outlet surfaces. To exchange heat between a transportation liquid medium and coolant flowing through the heat exchanger in the working condition, the transportation liquid medium supply is provided through a supply surface of the heat exchange system and the inlet surface to the heat exchanger, bringing in contact with the heat exchanger and again discharge via an outlet surface from the heat exchanger. According to the invention, the heat exchange system for removal of dirt comprises an automatic cleaning system.

EFFECT: automatic system of heat exchanger filter treatment in process of operation, elimination of heat exchange system outage.

12 cl, 6 dwg

FIELD: heating.

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9 cl, 3 dwg

FIELD: heating.

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13 cl, 6 dwg

FIELD: instrument making.

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EFFECT: provision of optimal distribution of load along a plate heat exchanger, simplified manufacturing and reduced manufacturing cost.

11 cl, 10 dwg

Heat exchanger // 2472091

FIELD: instrument making.

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11 cl, 8 dwg

FIELD: heating.

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11 cl, 13 dwg

FIELD: heating.

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EFFECT: simplifying the assembly and improving the operating reliability without any damage to heat exchange plates.

10 cl, 11 dwg

FIELD: instrument making.

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8 cl, 19 dwg

FIELD: instrument making.

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14 cl, 8 dwg

FIELD: power industry.

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4 dwg

FIELD: metallurgy.

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2 dwg

FIELD: metallurgy.

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6 dwg, 1 ex

FIELD: metallurgy.

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5 dwg, 2 tbl

FIELD: process engineering.

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5 cl, 1 dwg, 1 tbl, 1 ex

FIELD: process engineering.

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2 dwg, 4 tbl, 1 ex

FIELD: metallurgy.

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EFFECT: higher strength and fatigue characteristics of alloys.

2 cl, 1 tbl, 1 ex

FIELD: nanotechnologies.

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EFFECT: improved characteristics.

3 dwg, 1 tbl

FIELD: metallurgy.

SUBSTANCE: invention is related to the treatment method of titanium-nickel alloys with nickel content of 49-51 at % with shape memory effect and reversible shape memory effect (versions). The above method involves thermomechanical treatment combining deformation and annealing after deformation in the temperature range of 350-500°C till the accumulated deformation degree of 25-40% annealing after deformation in the temperature range of 350-500°C is obtained; thermomechanical guiding of shape memory effect (SME) and reversible shape memory effect (RSME) the annealing after deformation is performed during 1.5-10 h, and guiding of SME and RSME is performed by means of loading of the alloy as per the bending pattern with deformation of 12-20% at temperature Ak -10 ≤ T ≤ Ak +10, exposure at that temperature during 0.25-5 minutes, cooling to the end temperature of martensitic transformation; after that, alloy is unloaded and thermally cycled in the temperature range of Ak to -196°C with exposures during 0.25-5 minutes. According to the second version of the method, after the deformation is completed, first, recrystallisation annealing is performed at the temperature of 700°C during 0.20-120 minutes, and then, annealing after deformation is performed.

EFFECT: improving functional properties of the alloy.

2 cl, 1 dwg, 3 ex

FIELD: metallurgy.

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EFFECT: needles have painted surface, are characterised by increase in rigidity and plastic bending moment of bent surgical needles.

19 cl, 9 dwg, 4 ex

FIELD: metallurgy.

SUBSTANCE: method of thermomechanical treatment of workpieces from two-phase titanium alloys involves multi-stage severe plastic deformation with cumulative logarithmic deformation degree of not less than two and ageing. Severe plastic deformation of workpieces is performed with step-by-step temperature decrease at the interval of 0.99-0.3 of temperature of polymorphic transformation of alloy; at that, at the last stage of deformation the workpiece obtains the final shape. Prior to ageing the workpieces are heated up to temperature of 0.99-0.85 of temperature of polymorphic alloy transformation at the rate of not less than 50°C per minute and hardened.

EFFECT: increasing strength characteristics of two-phase titanium alloys and treatment process effectiveness.

3 cl, 1 tbl

FIELD: metallurgy.

SUBSTANCE: thermomechanical device includes a working member made in the form of one pre-deformed element or several pre-deformed and parallel and/or in-series connected elements from alloy based on titanium with shape memory effect. The working member is made in the form of a rod with working part of cylindrical or rectangular shape and fixing parts in the form of expansions on the rod ends, the sectional area of which is at least by five times more than the sectional area of its working part.

EFFECT: achieving maximum possible translational relative movements of the member at variation of its temperature at the temperature interval of reverse martensitic transformation of material.

6 dwg, 1 ex

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