JP2012224935A - Titanium alloy billet and method for producing titanium alloy billet, and method for producing titanium alloy forged material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: titanium alloy billets with which an α+β type titanium alloy product with small anisotropy can be manufactured at a relatively simplified forging process; a method for producing the titanium alloy billets; and a method for producing a titanium alloy forged material, by which a titanium alloy forged material is produced using the titanium alloy billets.SOLUTION: In the titanium alloy billets, a c-axis direction of an α phase is integrated within ±30° from the longitudinal direction of each of the titanium alloy billets toward the Y direction (direction of heavy reduction) and in a range ±40-90° from the longitudinal direction of each of the titanium alloy billets toward the X direction (direction perpendicular to the Y direction and the longitudinal direction), and a degree of the integration is 3 or greater.

Description

  The present invention relates to a titanium alloy billet obtained during the manufacturing process of a titanium alloy product, a method for manufacturing the titanium alloy billet, and a method for manufacturing a titanium alloy forged material using the titanium alloy billet to manufacture a titanium alloy forged material. It is about.

  Α + β type titanium alloy, represented by Ti-6Al-4V alloy, has various processing characteristics such as weldability, superplasticity, and diffusion bondability in addition to light weight, high strength, and high corrosion resistance. Has been used extensively. In order to further utilize these characteristics, in recent years it has come to be used for sports equipment such as golf equipment, such as consumer products such as automobile parts, civil engineering materials, various tools, Application to deep seas and energy development applications is also expanding.

  The α + β type titanium alloy product is first a titanium alloy after the raw material is melted and then subjected to a forging process of β region forging → α + β region forging → β heat treatment → α + β region forging as described in Patent Document 1, for example. The billet is manufactured by subjecting the titanium alloy billet to die forging, heat treatment, and machining, which include a plurality of wasteland forging steps and finish forging steps.

  The metal structure of this α + β type titanium alloy is composed of an α phase and a β phase. Among these metal structures, the β phase is a body-centered cubic crystal and has isotropic characteristics, but the α phase is a dense hexagonal crystal, and the crystal cell direction, particularly the c-axis direction (shown in FIG. 1). ) And the direction perpendicular to the c-axis are greatly different. For this reason, α + β type titanium alloy products may have anisotropy in various characteristics including mechanical characteristics depending on the orientation state (texture structure) of the α-phase crystal cell.

  The final product made of α + β type titanium alloy may be intentionally anisotropic for a specific purpose, but in many cases it is desired to have isotropic characteristics. Therefore, various efforts have been made to produce a final product having isotropic characteristics.

  In the conventional manufacturing method, first, a titanium alloy billet having no anisotropy in the radial direction is manufactured, and then the die forging, heat treatment, and machine comprising a plurality of rough forging processes and finishing forging processes are performed on the titanium alloy billet. It has been common to produce final products by processing. However, when manufacturing a final product with isotropic characteristics in such a manufacturing process, fine contrivances have been made in the wasteland forging process and the finishing forging process so that the strain introduced by die forging is not biased in one direction. It is necessary to elaborate. For that purpose, trial and error for finding the optimum forging process, including the contrivance of the shape of the mold, was carried out, and it took a lot of labor to produce the final product made of α + β type titanium alloy.

US Pat. No. 5,277,718

  The present invention has been made as a solution to the above-mentioned conventional problems, and a titanium alloy billet capable of producing an α + β type titanium alloy product having a small anisotropy by a relatively simple forging process, and the titanium alloy billet It is an object of the present invention to provide a method for producing a titanium alloy forged material that produces a titanium alloy forged material using the titanium alloy billet.

  The invention according to claim 1 is a titanium alloy billet having a metal structure composed of an α phase and a β phase, which is within ± 30 ° from the longitudinal direction of the billet toward the Y direction (downward pressure), and the billet The α-axis c-axis direction is accumulated in the range of ± 40 ° to 90 ° from the longitudinal direction of the film toward the X direction (the direction perpendicular to the Y direction and the longitudinal direction), and the degree of accumulation is 3 or more. This is a titanium alloy billet.

  The invention according to claim 2 is formed of a titanium alloy containing, by mass%, Al: 5.50 to 6.75%, V: 3.50 to 4.50%, the balance being Ti and inevitable impurities. The titanium alloy billet according to claim 1, wherein the billet is a titanium alloy billet.

In manufacturing the titanium alloy billet using the titanium alloy material, the invention described in claim 3 is the following formula (1) after heating the intermediate material forged using the titanium alloy material at a temperature lower than the β transformation temperature. A titanium alloy billet manufacturing method is characterized in that forging is performed under conditions satisfying the expression (3) to manufacture a titanium alloy billet.
(A1 × b2) / (a2 × b1) ≧ 1.5 (1)
(A1-a2) /a1≧0.4 Formula (2)
A2 / A1 ≧ 0.6 Formula (3)

  However, a1, b1, and A1 are cross-sectional shapes that are orthogonal to the longitudinal direction of the intermediate material before forging under strong pressure, a1 is the length of the intermediate material in the downward direction, and b1 is in the direction orthogonal to a1. A1 indicates the length of the intermediate material, A1 indicates the cross-sectional area, and a2, b2, and A2 indicate the cross-sectional shape orthogonal to the longitudinal direction of the intermediate material after forging, and a2 indicates the intermediate direction in the strong pressure downward direction. The length of the material, b2 indicates the length of the intermediate material in the direction orthogonal to a2, and A2 indicates the cross-sectional area.

  In the invention according to claim 4, the titanium alloy material contains, by mass%, Al: 5.50 to 6.75%, V: 3.50 to 4.50%, the balance being Ti and inevitable impurities. The titanium alloy billet manufacturing method according to claim 3, wherein the titanium alloy billet is a titanium alloy.

In manufacturing the titanium alloy forged material using the titanium alloy billet according to the first or second aspect, the invention according to the fifth aspect is characterized in that after the titanium alloy billet is heated at a temperature lower than the β transformation point, the strong pressure is reduced. The titanium alloy billet is deformed under conditions satisfying the following formulas (4) and (5) from a direction that is perpendicular to the direction and within a range of ± 10 ° from the direction perpendicular to the longitudinal direction. An alloy forging material is produced. A method for producing a titanium alloy forging material.
(B2-b3) /b2≧0.2 (4)
(B2-b4) /b2≦0.6 (5)

  However, b3 and b4 show the length of the titanium alloy forging material in the direction parallel to b2 (defined in claim 3) after the forging process for producing the titanium alloy forging material, b3 shows the length of the longest part, b4 Indicates the length of the shortest part, respectively.

  According to the titanium alloy billet and the titanium alloy billet manufacturing method and the titanium alloy forging material manufacturing method of the present invention, the ingenuity of the forging process is devised, such as devising the shape of the mold to produce the titanium alloy forging material. Even without elaboration, an α + β type titanium alloy product having a small anisotropy can be produced by a relatively simple forging process.

It is a perspective view which shows the alpha phase of an alpha + beta type titanium alloy. It is a cross-sectional view of a titanium alloy billet illustrating the inclination of the α-phase c-axis from the billet longitudinal direction to the Y direction. It is a longitudinal cross-sectional view of the titanium alloy billet which illustrates the inclination of the c-axis of the α phase from the billet longitudinal direction to the X direction. It is explanatory drawing which shows the accumulation position and accumulation degree of c phase direction of (alpha) phase.

  When trying to obtain titanium alloy products with low anisotropy by forging using α + β type titanium alloy material with a metal structure consisting of α phase and β phase, it has conventionally been very complicated and finely devised to mold shape etc. It cannot be produced unless it is subjected to a forging process such as scouring, and this is a major factor, leading to an increase in the cost of α + β type titanium alloy products.

  The present inventors have found an invention capable of producing an α + β type titanium alloy product (titanium alloy forging material) having a small anisotropy by a relatively simple forging process without elaborating the mold shape or the like. In order to achieve this goal, we have conducted extensive research. As a result, the c-axis direction (shown in FIG. 1) of the α phase of the titanium alloy billet obtained in the course of the manufacturing process of the α + β type titanium alloy product is accumulated in a specific range and is anisotropic at the stage of the titanium alloy billet. When the titanium alloy billet is used for the production of titanium alloy products, it has been found that α + β type titanium alloy products with small anisotropy can be produced by a relatively simple forging process. It was completed.

  Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings. First, the titanium alloy billet obtained in the middle of the manufacturing process of the titanium alloy product will be described in detail.

  The α + β-type titanium alloy is composed of a dense hexagonal α phase and a body-centered cubic β phase. Among these metal structures, the β phase is isotropic because it is a body-centered cubic crystal, but the α phase having a crystal structure (dense hexagonal crystal) as shown in FIG. In particular, the characteristics are greatly different between the c-axis direction and the direction perpendicular to the c-axis. Therefore, an α + β type titanium alloy product may cause anisotropy in various characteristics including mechanical characteristics depending on the orientation direction of the α-phase crystal cell.

  The most preferable condition for obtaining an α + β type titanium alloy product with small anisotropy is when the crystal orientation (texture) is randomly oriented. Moreover, even if there is an accumulation of crystal orientations, if there are a plurality of accumulation locations and the accumulation positions are spatially dispersed (if their orientations are different), the titanium alloy product The anisotropy of becomes smaller. That is, satisfying one of the above-mentioned conditions at the final product stage is a condition for obtaining an α + β-type titanium alloy product with low anisotropy.

  When manufacturing titanium alloy products by die forging using titanium alloy billets, if the length of the titanium alloy product is larger than the billet diameter of the titanium alloy billet, the longitudinal direction of the titanium alloy billet and the maximum length direction of the titanium alloy product Titanium alloy products are manufactured in such a way as to match.

  In this case, the titanium alloy billet is mainly deformed from the vertical direction orthogonal to the longitudinal direction of the billet. If the main deformation can be limited to one direction, the productivity will be improved. However, if the crystal orientation (texture) of the raw material (titanium alloy billet) is randomly oriented, A specific texture is formed, and as a result, a strong anisotropy is likely to occur. This is because the α-phase c-axis tends to accumulate in a direction (vertical direction) orthogonal to the processing direction.

  In order to reduce the anisotropy generated in the titanium alloy product, it is necessary to satisfy one of the two conditions described above at the final product stage, but the present inventors satisfy these conditions. In order to find a method that can do this, we have intensively studied.

  As described above, the α-phase c-axis tends to accumulate in a direction (vertical direction) perpendicular to the processing direction. There is also a tendency to accumulate in the forging direction. As a result of studying based on these trends, it is possible to accumulate the c-axis direction of the α phase in a certain range at the stage of titanium alloy billet and to add anisotropy at the stage of titanium alloy billet. It was found that this is effective for obtaining an α + β type titanium alloy product (titanium alloy forged material) having a small anisotropy.

  As described above, a titanium alloy product is manufactured from a titanium alloy billet by die forging. In the die forging process, if the α phase is deformed in a direction parallel to or close to the c axis of the α phase, the α phase is deformed. However, all crystal grains are not oriented at the same time, and some of the grains remain in an almost initial state parallel to the processing direction. Is a stage in the middle of alignment. In addition, when forging is applied, there are crystal grains oriented in the forging direction. As a result, despite the fact that the processing direction at the die forging stage is a constant direction, it is possible to avoid the accumulation of α-phase extremely and to obtain a titanium alloy product having a small anisotropy.

  For example, as shown in FIGS. 2 to 4, within ± 30 ° from the longitudinal direction of the billet toward the Y direction (the downward direction of strong pressure during billet forging) (FIG. 2 shows an example of 0 °), and The α-phase c-axis direction may be accumulated in a range of ± 40 ° to 90 ° from the longitudinal direction of the billet in the X direction (the direction perpendicular to the Y direction and the longitudinal direction). If the c-axis direction of the α phase is accumulated outside this range, even if the degree of accumulation is 3 or more, when deformation is mainly applied from one direction in the die forging process, A texture is formed, resulting in anisotropy in the mechanical properties.

  The α-phase c-axis direction is more preferably accumulated within a range of ± 10 ° from the longitudinal direction of the billet toward the Y direction, and from ± 60 ° to the X direction from the longitudinal direction of the billet. It is more preferable to accumulate in a range of 70 °.

  Further, as described above, the degree of integration needs to be 3 or more. When the degree of integration is less than 3, if a large strain is applied in one direction in the subsequent die forging process, the c-axis of the α phase may accumulate in another direction due to the processing, and anisotropy may occur in the mechanical characteristics. is there.

  The present invention can be applied to any α + β type titanium alloy. In particular, it is preferably formed of a component specified by AMS4928. That is, it is preferable that Al: 5.50 to 6.75% by mass, V: 3.50 to 4.50% by mass, with the balance being Ti and an inevitable impurity titanium alloy. As an unavoidable impurity, N: 0.05 mass%, C: 0.08 mass%, H: 0.015 mass%, Fe: 0.30 mass%, O: 0.20 mass% are contained.

  The titanium alloy billet may be formed of a titanium alloy specified by AMS4981. The titanium alloy specified by AMS4981 contains Al, Sn, Zr and Mo as main additive elements, and the contents thereof are Al: 5.50 to 6.50 mass%, Sn: 1.75 to 2.75. 25% by mass, Zr: 3.50 to 4.50% by mass, Mo: 5.50 to 6.50% by mass, with the balance being Ti and inevitable impurities. As inevitable impurities, N: 0.04 mass%, C: 0.08 mass%, H: 0.015 mass%, Fe: 0.15 mass%, and O: 0.15 mass% are contained.

  Next, the manufacturing method of the titanium alloy billet of this invention is demonstrated.

  Usually, a titanium alloy billet is manufactured through each process of (a) β region forging → (b) α + β region forging → (c) β heat treatment → (d) α + β region forging. The physical properties and structure of the titanium alloy billet to be manufactured vary depending on the order and the conditions of each process, so the conditions should be selected and determined comprehensively as a series of manufacturing processes. It is not appropriate to strictly define the order of processes and the conditions for each process.

  However, when the present inventors diligently studied the production conditions for producing the titanium alloy billet of the present invention, titanium having the anisotropy intended by the present invention was adopted by adopting the production conditions shown below. It was confirmed that the alloy billet can be produced reliably.

  The manufacturing conditions are as follows: (d) in the α + β forging step, an intermediate material previously forged using a titanium alloy material is heated at a temperature lower than the β transformation temperature (α + β temperature range), and the following formula ( Forging is performed under conditions that satisfy 1) to (3).

Each conditional expression is as follows.
(A1 × b2) / (a2 × b1) ≧ 1.5 (1)
(A1-a2) /a1≧0.4 Formula (2)
A2 / A1 ≧ 0.6 Formula (3)
However, a1, b1, and A1 are cross-sectional shapes that are orthogonal to the longitudinal direction of the intermediate material before forging under strong pressure, a1 is the length of the intermediate material in the downward direction, and b1 is in the direction orthogonal to a1. A1 indicates the length of the intermediate material, A1 indicates the cross-sectional area, and a2, b2, and A2 indicate the cross-sectional shape orthogonal to the longitudinal direction of the intermediate material after forging, and a2 indicates the intermediate direction of the strong pressure downward The length of the material, b2 indicates the length of the intermediate material in the direction orthogonal to a2, and A2 indicates the cross-sectional area.

  When heating at a temperature equal to or higher than the β transformation temperature before starting forging of the intermediate material, strain introduced by forging is not effectively accumulated, and desired anisotropy cannot be imparted to the titanium alloy billet. Therefore, the heating temperature before starting forging of the intermediate material is set to a temperature lower than the β transformation temperature (α + β temperature range).

  Equation (1) defines the ratio of the amount of deformation in the direction of strong pressure and the direction perpendicular to the direction required for the titanium alloy billet to obtain anisotropy. If the value obtained from (a1 × b2) / (a2 × b1) is smaller than 1.5, sufficient anisotropy cannot be imparted to the titanium alloy billet. Therefore, (a1 × b2) / (a2 × b1) ≧ 1.5.

  Equation (2) defines the amount of deformation in the direction of strong pressure by forging the intermediate material. When the value obtained from (a1-a2) / a1 is a value smaller than 0.4, even if the condition according to Equation (1) is satisfied, the deformation amount itself is small, so that the titanium alloy billet has sufficient anisotropy. Cannot be granted. Therefore, (a1-a2) /a1≧0.4.

  In Formula (3), the material outflow amount in the longitudinal direction when the intermediate material is forged is defined. If the value obtained from A2 / A1 is a value smaller than 0.6, the material has flowed out in the longitudinal direction by strong forging even if the conditions according to Equation (1) and Equation (2) are satisfied. Therefore, desired anisotropy cannot be imparted to the titanium alloy billet. Therefore, A2 / A1 ≧ 0.6.

  In addition, after forging the intermediate material under the conditions satisfying the expressions (1) to (3), forging in which the shape of the cross section perpendicular to the longitudinal direction of the intermediate material isotropically changes in the α + β temperature range. You can go. It should be noted that the amount of deformation in the direction of strong pressure / (the amount of deformation in the direction perpendicular to the direction of strong pressure) by this forging must be within 1.1.

  During the forging process and after the forging process, the intermediate material and the titanium alloy billet should not be heated at a temperature equal to or higher than the β transformation point. When the intermediate material and the titanium alloy billet are heated to the β transformation point or higher, the anisotropy imparted by forging under the conditions satisfying the formulas (1) to (3) is lost.

  Next, a method for producing a titanium alloy forged material (titanium alloy product) using the titanium alloy billet will be described.

  Titanium alloy forgings are manufactured from titanium alloy billets by die forging. In the die forging process, if a strain is applied in the direction parallel to the direction of strong rolling by the above-described strong rolling forging, the texture of the titanium alloy billet already exists ( The α-phase c-axis is oriented in the vertical direction perpendicular to the direction of strong pressure.) Is further promoted. That is, the anisotropy of mechanical properties is promoted, and the anisotropy is further increased.

  On the other hand, when strain is applied from the direction orthogonal to the direction of strong pressure, the deformation direction substantially coincides with the orientation direction of the α-phase c-axis. The α phase tends to be oriented in a direction perpendicular to the deformation direction, but all the crystal grains are not oriented at the same time, and some of the crystal grains are generally in an initial state parallel to the processing direction. Some are in the middle of alignment. As a result, regardless of the processing direction in the die forging stage being a constant direction, it is possible to avoid the accumulation of the α phase extremely and to obtain a titanium alloy product having a small anisotropy.

  Specifically, in this die forging process, the titanium alloy billet is heated at a temperature below the β transformation point (α + β temperature range), and then within a range of ± 10 ° in the direction perpendicular to the strong pressure lowering direction and the longitudinal direction. What is necessary is just to produce a titanium alloy forging material by adding a deformation | transformation to the said titanium alloy billet on the conditions which satisfy | fill following formula (4) and formula (5) from the direction of a position.

Each conditional expression is as follows.
(B2-b3) /b2≧0.2 (4)
(B2-b4) /b2≦0.6 (5)
However, b3 and b4 show the length of the titanium alloy forging material in the direction parallel to b2 (defined in claim 3) after the forging process for producing the titanium alloy forging material, b3 shows the length of the longest part, b4 Indicates the length of the shortest part, respectively.

  When the titanium alloy forging material is heated at a temperature equal to or higher than the β transformation temperature before starting forging, the anisotropy imparted by forging under conditions satisfying the expressions (1) to (3) disappears. End up. Therefore, the heating temperature before starting forging of the forged intermediate material of the titanium alloy forged material is set to a temperature lower than the β transformation temperature (α + β temperature range).

  In formula (4), the degree of dispersion of crystals (the degree to which strong anisotropy at the stage of titanium alloy billet is reduced) in the process of manufacturing a titanium alloy forged material (titanium alloy product) using a titanium alloy billet ). When the value obtained from (b2-b3) / b2 is a value smaller than 0.2, strong anisotropy imparted in the direction perpendicular to the direction of strong reduction remains in the step of manufacturing the titanium alloy billet. Thus, the anisotropy of the titanium alloy forged material cannot be reduced. Therefore, (b2−b3) /b2≧0.2.

  Formula (5) defines the degree of dispersion of crystals in the process of manufacturing a titanium alloy forged material (titanium alloy product) using a titanium alloy billet. When the value obtained from (b2-b4) / b2 is a value larger than 0.6, the ratio of the α phase in which the c-axis is oriented in the direction perpendicular to the deformation direction in the die forging process for producing the titanium alloy forged material Since anisotropy is formed in a direction different from the state of the titanium alloy billet, the anisotropy of the titanium alloy forged material cannot be reduced. Therefore, (b2−b4) /b2≦0.6.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples, but may be implemented with appropriate modifications within a range that can be adapted to the gist of the present invention. These are all included in the technical scope of the present invention.

  In the test of this example, first, using a Ti-6Al-4V ingot of φ840 mm, each of (a) β region forging → (b) α + β region forging → (c) β heat treatment → (d) α + β region forging Through the process, a titanium alloy billet was obtained.

  Specifically, after (a) β zone forging, (b) α + β zone forging step, finish various cross-sectional shapes before forging shown in Table 1 as an intermediate material, then (c) β heat treatment, After holding at 1050 ° C. for 1.5 hours, water cooling was performed, and stress strain removal was performed at 700 ° C. for 2.5 hours. Thereafter, the intermediate material after the β heat treatment was heated to 950 ° C. below the β transformation temperature in the heating furnace (the β transformation temperature of the titanium alloy used was 995 ° C.), held for 3 hours, then taken out of the heating furnace and listed in Table 1. (D) α + β region forging was performed so as to obtain the shape after forging. Then, after heating again to 950 degreeC and hold | maintaining for 3 hours, it forged so that a cross-sectional shape might be set to 270 mm, and obtained the titanium alloy billet. Table 2 shows values obtained by the formulas (1) to (3).

(Texture evaluation)
Samples each having a cross section perpendicular to the longitudinal direction as shown in FIG. 2 as an evaluation surface were cut out from the center in the circumferential direction of each cylindrical titanium billet. These evaluation surfaces were polished with emery paper (# 2400), and then mirror polishing was performed for measurement.

  The texture evaluation was carried out by measuring the X-ray positive dot diagram. Specifically, using a Rigaku X-ray diffractometer (RINT-5000), a {0002} texture measurement of α phase is performed by a reflection method under the condition of a target output of 40 kV-200 mA with a Cu target, and a standardization process After that, the measurement result was output. The integration degree was output at 0.5 pitch, and the integration position and the integration degree were evaluated. The results are shown in Table 2. In addition, {0002} is a plane orthogonal to the c-axis direction of the α phase.

  FIG. 4 shows an example of outputting measurement results. The scale of the vertical axis (Y direction: strong pressure downward direction) and the horizontal axis (X direction: vertical direction to the strong pressure downward direction) is a scale given every 10 °, and the vertical axis (Y direction) is the c axis of the α phase. The horizontal axis (X direction) indicates the inclination angle of the α-phase c-axis from the longitudinal direction of the billet to the X direction, respectively. Also, the numbers drawn from the contour lines are the degree of integration and are displayed at 0.5 pitches. According to FIG. 4, it is within ± 30 ° from the longitudinal direction of the billet toward the Y direction (strong downward direction), and ± from the longitudinal direction of the billet to the X direction (direction perpendicular to the Y direction and the longitudinal direction). It can be seen that the c-axis direction of the α-phase is accumulated in the range of 40 ° to 90 °, and the degree of accumulation is 3 or more.

  Next, the titanium alloy billet is heated and held at 950 ° C., forged in a direction perpendicular to the longitudinal direction and the direction of strong pressure under the condition (b2-b3) = 0.4, and cooled to room temperature. A titanium alloy forged material was used. Thereafter, texture evaluation was performed in the same manner as described above, and the degree of integration was determined in the same manner as the titanium alloy billet. When there are five or more regions where the degree of integration obtained here is 1.5 or more and each peak position is sufficiently separated (50 ° or more is regarded as acceptable), the anisotropy is small macroscopically. It was judged that an isotropic titanium alloy forged material (α + β type titanium alloy product) was obtained. The results are shown in Table 2 as forging materials.

  No. 1 and no. 2 is a titanium alloy billet manufactured with manufacturing requirements satisfying the formulas (1) to (3). As a result, the texture (accumulation position and integration degree) of the titanium alloy billet satisfies the requirements of the present invention, and the titanium alloy forging produced from the titanium alloy billet has a small anisotropy and isotropic titanium alloy forging. It became a material.

  In contrast, no. 3 and no. No. 4 shows that, among the manufacturing requirements, the formulas (1) and (2) do not satisfy the requirements of the present invention. 5, all of the formulas (1) to (3) do not satisfy the requirements of the present invention. As a result, the texture (accumulation position and degree of accumulation) of the titanium alloy billet does not satisfy the requirements of the present invention, and the titanium alloy forged material produced from the titanium alloy billet is a titanium alloy forged material having large anisotropy. It was.

Claims (5)

A titanium alloy billet having a metal structure composed of an α phase and a β phase,
Within ± 30 ° from the longitudinal direction of the billet toward the Y direction (high pressure downward direction), and ± 40 ° to 90 ° from the longitudinal direction of the billet toward the X direction (direction perpendicular to the Y direction and the longitudinal direction) The c-axis direction of the α phase is accumulated in the range of
A titanium alloy billet having an integration degree of 3 or more.   It is characterized by containing Al: 5.50 to 6.75%, V: 3.50 to 4.50%, and the balance being made of Ti and a titanium alloy that is an inevitable impurity. The titanium alloy billet according to claim 1. In manufacturing titanium alloy billets using titanium alloy materials,
After heating an intermediate material forged using a titanium alloy material at a temperature lower than the β transformation temperature, forging is performed under conditions satisfying the following formulas (1) to (3):
A method for producing a titanium alloy billet, characterized by producing a titanium alloy billet.
(A1 × b2) / (a2 × b1) ≧ 1.5 (1)
(A1-a2) /a1≧0.4 Formula (2)
A2 / A1 ≧ 0.6 Formula (3)
However, a1, b1, and A1 are cross-sectional shapes that are orthogonal to the longitudinal direction of the intermediate material before forging under strong pressure, a1 is the length of the intermediate material in the downward direction, and b1 is in the direction orthogonal to a1. A1 indicates the length of the intermediate material, A1 indicates the cross-sectional area, and a2, b2, and A2 indicate the cross-sectional shape orthogonal to the longitudinal direction of the intermediate material after forging, and a2 indicates the intermediate direction of the strong pressure downward The length of the material, b2 indicates the length of the intermediate material in the direction orthogonal to a2, and A2 indicates the cross-sectional area.   The titanium alloy material is a titanium alloy containing, by mass%, Al: 5.50 to 6.75%, V: 3.50 to 4.50%, and the balance being Ti and inevitable impurities. The method for producing a titanium alloy billet according to claim 3. In producing a titanium alloy forged material using the titanium alloy billet according to claim 1 or claim 2,
After heating the titanium alloy billet at a temperature less than the β transformation point, the following formulas (4) and (4) are obtained from a direction that is perpendicular to the direction of strong pressure and within a range of ± 10 ° from the direction perpendicular to the longitudinal direction: 5. A method for producing a titanium alloy forged material comprising producing a titanium alloy forged material by deforming the titanium alloy billet under the conditions satisfying 5).
(B2-b3) /b2≧0.2 (4)
(B2-b4) /b2≦0.6 (5)
However, b3 and b4 show the length of the titanium alloy forging material in the direction parallel to b2 (defined in claim 3) after the forging step for producing the titanium alloy forging material, b3 shows the length of the longest part, b4 Indicates the length of the shortest part, respectively.

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