Blank making method for improving texture uniformity of TC18 titanium alloy thick plate type forge piece

Abstract

The invention discloses a blank making method for improving the texture uniformity of a TC18 titanium alloy thick plate type forge piece. The blank making method comprises the steps that firstly, Z-X-Y three-direction forging is conducted on an original bar; drawing out the blank subjected to three-direction forging in the X direction and the Y direction; and then the drawn blank is flattened and shaped in the X direction, the Y direction and the X direction in sequence. According to the method, Z-direction deformation is increased by adopting three-direction forging during blank manufacturing through a method of increasing the height deformation of the bar, so that the forge piece deforms in three directions in the blank manufacturing process, the difference of the deformation in the three directions of the blank in the blank manufacturing process is reduced, strong orientation texture segregation caused by the difference of the three-direction deformation is weakened, and the mechanical property of the forge piece has anisotropy; and the material is uniformly deformed in three directions, the effect of weakening the beta-phase texture is achieved, the requirement for improving the texture uniformity of the forge piece is met, and the mechanical property of the material is improved.

Description

Technical Field

[0001] The invention relates to a blank making method for improving the texture uniformity of a TC18 titanium alloy thick plate forging, and belongs to the field of titanium alloy plastic forming. Background Art

[0003] TC18 titanium alloy is a high-strength and high-toughness near-β titanium alloy. Its nominal composition is: Ti-5Al-5Mo-5V-1Cr-1-Fe. The strength after annealing can reach 1090 MPa, and it has good performance in hardenability and plasticity. In TC18 titanium alloy, the β phase accounts for about 50%, which is a typical body-centered cubic crystal structure. Its mechanical properties are directional. <111> The strength, elastic modulus and impact toughness of the direction are greater than <110> Direction, greater than <100> direction, so in the process of forging preparation, it is necessary to weaken the β phase texture strength and reduce the anisotropy of forging performance to obtain products with excellent mechanical properties.

[0004] TC18 titanium alloy forgings are usually made of bars through free forging and then die forging. However, during the entire process from billet making to die forging to heat treatment, the organization and texture of the titanium alloy bars have a genetic effect. During the forging process, due to the different deformation temperatures and deformation degrees, the forgings will change from the initial orientation to the texture type that is biased towards the forging direction as the strain increases, causing the forgings to have anisotropy in mechanical properties, which has a great impact on the quality of the forgings. For thick plate forgings, the cylindrical bars need to be flattened into thick plates during billet making. The traditional unidirectional flattening method will cause the TC18 titanium alloy β phase to form a strong <100> , <111> The oriented texture makes the final forging mechanical properties anisotropic, that is, the billet deforms unevenly in the three directions of XYZ, causing the texture to be segregated, thus affecting the mechanical properties of the subsequent die forgings. Summary of the invention

[0006] In view of the above-mentioned deficiencies in the prior art, an object of the present invention is to provide a billet making method for improving the texture uniformity of TC18 titanium alloy thick plate forgings, thereby solving the problem of uneven texture of thick plate type TC18 titanium alloy forgings during the forging process.

[0007] To achieve the above purpose, the present invention adopts the following technical solutions: A method for improving the texture uniformity of TC18 titanium alloy thick plate forgings, characterized in that it comprises the following steps: Step 1: Perform ZXY three-way forging on the original bar; Step 2: Lengthen the three-way forged billet in the X and Y directions; Step 3: The drawn blank is flattened and shaped in the X, Y and X directions in turn.

[0008] Furthermore, in step 1, the heated original billet is taken out of the furnace and turned over in sequence along the ZXY directions on the free forging press for upsetting deformation; wherein the upsetting deformation amount along the billet height direction Z should be consistent with the total deformation in the billet flattening direction to ensure the uniformity of deformation, and the upsetting amounts along the diameter directions X and Y remain the same.

[0009] Furthermore, in step 2, the three-way forged billet is stretched in the X and Y directions in sequence, firstly stretching in the X direction, and then turning the billet over to stretch in the Y direction; the stretching deformation amount in the X direction and the stretching deformation amount in the Y direction remain the same.

[0010] Furthermore, in step 3, the stretched blank is flattened along the X direction to the pre-blank design size; the blank flattened in the X direction is flattened along the Y direction to the same width as the two ends of the blank to eliminate the bulge generated when flattened in the X direction; the blank flattened in the Y direction is flattened along the X direction to the specified size to complete the blank making.

[0011] In step 1, the starting temperature of the three-way forging of the TC18 titanium alloy billet is 870-890°C, the preset temperature of the die is 300-350°C, the billet is heated to a temperature in a heating furnace and then kept warm for 3-5 minutes to make the temperature distribution in the bar uniform, and then transferred from the heating furnace to the free forging press, and the transfer time is set to 90-120s; The pressing speed of the free forging upper die is 15-20 mm / s, the heat transfer between the billet and the air is set to 6N / sec / mm / C, and the friction coefficient between the die and the billet is set to 0.3.

[0012] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention increases the deformation of the bar material in the high direction by using three-way forging to increase the deformation in the Z direction during blank making, so that the forging is deformed in three directions during the blank making process, reduces the difference in the deformation of the blank in the three directions during the blank making process, weakens the strong orientation texture segregation caused by the difference in the three-way deformation, makes the mechanical properties of the forging anisotropic, makes the material deform evenly in the three directions, plays a role in weakening the β-phase texture, meets the requirement of improving the texture uniformity of the forging, and improves the mechanical properties of the material.

[0013] 2. The method of the present invention can effectively weaken the β-phase texture of the blank and improve the uniformity of the texture. The types and strengths of the strong oriented textures such as {100} and {111} of the blank are greatly weakened, and the difference in texture types between the core and edge of the blank is also reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1A flow chart of a method for improving the texture uniformity of a TC18 titanium alloy thick plate forging according to the present invention; Figure 2 This is a schematic diagram of the texture comparison position of the blank of the present invention; Figure 3 The texture diagram of the TC18 titanium alloy produced by unidirectional flattening of the present invention; Figure 4 This is the texture diagram of the TC18 titanium alloy produced by three-way forging and then stretching and flattening. DETAILED DESCRIPTION

[0017] The technical solution of the present invention is clearly and completely described below in conjunction with specific embodiments and drawings. Obviously, the embodiments are only representative of embodiments of the present invention and are not limited to the described embodiments. Therefore, the following detailed description of the embodiments provided in the drawings is not intended to limit the scope of the invention claimed for protection. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] It should be noted that similar numbers and letters represent similar items in the following figures, so once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. The terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the figures, or the positions or positional relationships in which the invented product is usually placed when used. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0019] Example 1 like Figure 1 As shown, the present invention provides a method for improving the texture uniformity of TC18 titanium alloy thick plate forgings, comprising the following steps: Step 1: Perform ZXY three-way forging on the original bar; Step 2: Lengthen the three-way forged billet in the X and Y directions; Step 3: The stretched blank is flattened in the X, Y and X directions in turn.

[0020] In this embodiment, the size of the TC18 titanium alloy cylindrical bar is selected as φ300×500 mm, the billet will eventually be flattened into a thick plate with a thickness of 150 mm along the diameter direction, and the total deformation in the thickness direction of the billet is 50%.

[0021] Among them, the starting temperature of the three-way forging of TC18 titanium alloy billet is 890 ℃, the preset temperature of the die is 300 ℃, the heating coefficient of the billet is 10 ℃ / s, the billet is heated to temperature in the heating furnace and kept warm for 3 minutes to make the temperature distribution in the bar uniform, and then transferred from the heating furnace to the free forging press, and the transfer time is set to 90 s. The pressing speed of the free forging upper die is 15 mm / s, the heat transfer between the billet and the air is set to 6 N / sec / mm / C, and the friction coefficient between the die and the billet is set to 0.3.

[0022] In step 1, the upsetting pressure of the blank in the length direction Z is 250 mm, and the deformation is 50%, which is consistent with the total deformation in the thickness direction. After the upsetting in the Z direction is completed, the blank is turned over for upsetting in the X direction. When the upper and lower dies are deformed in the X direction to a closing distance of 250 mm, the pressing is stopped. Then the blank is turned over for upsetting in the Y direction, and the Y direction is also pressed down to a closing distance of 250 mm. Finally, after three-way free forging, the size of the blank changes from the original cylindrical bar to a square material of 515×337×250 mm.

[0023] In step 2, the three-way forged billet is turned over on the free forging press to be stretched in the X and Y directions. The billet is first pressed down and stretched in the X direction. After the X direction stretching is completed, it is stretched in the Y direction. The X direction is pressed down to the upper and lower mold distance of 250 mm, and the Y direction is also pressed down to the mold distance of 250 mm. After stretching, the billet size changes to 599×282×250 mm.

[0024] In step 3, the stretched billet is turned over again to be flattened in the X direction until the billet's X-direction dimension is 150 mm; the flattened billet is turned over again to be flattened in the Y direction to eliminate the bulge in the width direction during the previous step of flattening, and the billet is flattened in the Y direction until the billet's Y-direction dimension is 300 mm. Finally, the billet is turned over again to be shaped in the X direction to make the billet flat in the X direction, and pressed down to a dimension of 150 mm in the X direction. The final size of the billet is 784×360×150 mm.

[0025] The above billet making process is completed in one heating. After the billet making is completed, the temperature of most areas of the billet is above 700 ℃, the highest temperature of the billet core reaches 976 ℃, and the surface temperature of the billet in contact with the free forging die drops rapidly, with the lowest temperature being 429 ℃. The maximum forming load of the upper die in the free forging stage is 1720 tons. Compared with the original billet making scheme, the proportion of small deformation area at the edge of the billet material after optimization is greatly reduced, and the strain distribution of the billet is more uniform.

[0026] See also Figure 2 From the texture comparison position of the blank of the present invention, it can be seen that the center and edge of the blank are selected to compare the texture type and strength before and after deformation, where P1 is the area with large strain in the center of the blank, and P2 is the area with small deformation at the edge of the blank.

[0027] See also Figure 3 The texture of TC18 titanium alloy produced by unidirectional flattening is that before deformation, the core position P1 is {110} texture, and the edge position P2 is {110} and {001} texture. After the original unidirectional flattening, the core position P1 of the billet still maintains {110}, and the edge position is {110} and {001} texture. The strongly oriented texture is obviously segregated and the texture strength is relatively high. The weakening of the strongly oriented texture cannot be achieved through the original billet making scheme.

[0028] It can be seen that, by comparing the blank making method of this embodiment with the original unidirectional flattening blank making method, after the original blank making scheme is deformed, the blank still retains the core {110}, edge {110} and {001} textures, and the texture type after deformation is the same as the original texture, and there is a large difference between the core and edge textures, which will lead to anisotropy in subsequent forgings. The blank making method in this embodiment uses the same original texture as the original blank making scheme to make blanks, and the strong {110} and {001} textures in the original texture β phase are weakened, and the texture difference between the core position P1 and the edge position P2 is small, the texture type is basically the same, and only the texture strength is different. After deformation, the overall texture distribution of the blank is more uniform.

[0029] See also Figure 4 The texture of TC18 titanium alloy after three-way forging and then stretching and flattening is consistent with the unidirectional flattening before deformation, which is still the {110} texture at the core position P1 and the {110} and {001} textures at the edge position P2. After three-way forging and stretching and flattening, the texture at the core position P1 is {012}, {110}, {112}, and the texture type at the edge position P2 is similar to that of the core. Since there is {001} texture in the original texture of the edge, there is still {001} texture at the edge after deformation, but its strength is weakened after deformation.

[0030] In summary, the blank making method of the present invention increases the deformation of the blank in the height direction by first forging in three directions, then stretching in the X and Y directions, and finally flattening in the XYX directions in sequence, compared with the method of directly flattening the cylindrical bar in one direction, and can reduce the deformation non-uniformity of the material in the three directions of XYZ, and reduce the influence of texture segregation on the mechanical properties of subsequent die forgings by weakening the β phase texture.

[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for improving the texture uniformity of TC18 titanium alloy thick plate forgings, characterized in that: The following steps are involved: Step 1: Perform ZXY three-way forging on the original bar; Step 2: Lengthen the three-way forged billet in the X and Y directions; Step 3: The drawn blank is flattened and shaped in the X, Y and X directions in turn.

2. The forming method according to claim 1, characterized in that: In the step 1, the heated original billet is taken out of the furnace and turned over in sequence along the ZXY directions on the free forging press for upsetting deformation; wherein the upsetting deformation amount along the billet height direction Z should be consistent with the total deformation in the billet flattening direction to ensure the uniformity of deformation, and the upsetting amounts along the diameter directions X and Y remain the same.

3. The method for making a blank according to claim 1, characterized in that: In the step 2, the three-way forged billet is stretched in the X and Y directions in sequence, firstly stretching in the X direction, and then turning the billet over to stretch in the Y direction; the stretching deformation amount in the X direction and the stretching deformation amount in the Y direction remain the same.

4. The method for making a blank according to claim 1, characterized in that: In the step 3, the stretched blank is flattened along the X direction to the pre-blank design size; the blank flattened in the X direction is flattened along the Y direction to the same width as the two ends of the blank to eliminate the bulge caused by flattening in the X direction; the blank flattened in the Y direction is flattened along the X direction to the specified size to complete the blank making.

5. The method for making a blank according to claim 1, characterized in that: In step 1, the starting temperature of the three-way forging of the TC18 titanium alloy billet is 870-890°C, the preset temperature of the die is 300-350°C, the billet is heated to a temperature in a heating furnace and then kept warm for 3-5 minutes to make the temperature distribution in the bar uniform, and then transferred from the heating furnace to the free forging press, and the transfer time is set to 90-120s; The pressing speed of the free forging upper die is 15-20 mm / s, the heat transfer between the billet and the air is set to 6N / sec / mm / C, and the friction coefficient between the die and the billet is set to 0.

3.

6. The method for making a blank according to claim 1, characterized in that: The starting temperature of the three-way forging of TC18 titanium alloy billet is 890 ℃, and the preset temperature of the die is 300 ℃. The billet is heated to temperature in the heating furnace and kept warm for 3 minutes to make the temperature distribution in the bar uniform, and then transferred from the heating furnace to the free forging press, and the transfer time is set to 90 s; the pressing speed of the free forging upper die is 15 mm / s, the heat transfer between the billet and the air is set to 6 N / sec / mm / C, and the friction coefficient between the die and the billet is set to 0.3.

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