Forging method and application of high-uniformity TA31 titanium alloy plate

Abstract

The invention belongs to the technical field of non-ferrous metal processing, and relates to a forging method and application of a high-uniformity TA31 titanium alloy plate. According to the forging method, through the X-direction, Y-direction and Z-direction three-dimensional homogenization forging mode, the overall uniformity of the blank can be effectively improved. Meanwhile, through X-direction and Y-direction alternate drawing-out forming, the purposes of improving the tissue uniformity of a finished plate and reducing anisotropy are achieved; furthermore, the invention innovatively provides a production process of the titanium alloy plate with small thickness and large width, and through the process, the problem that the anisotropy of the titanium alloy plate produced in a traditional rolling mode is large can be solved. By the adoption of the forging method, the qualified TA31 titanium alloy plate meeting the design requirement can be produced, and the forging method has excellent structure uniformity and performance uniformity and is suitable for industrial production.

Description

Technical Field

[0001] The invention belongs to the technical field of nonferrous metal processing and relates to a forging method and application of a high-uniformity TA31 titanium alloy plate. Background Art

[0002] Titanium alloys possess excellent properties, including corrosion resistance, high specific strength, and non-magnetic properties, and are widely used in aviation, aerospace, shipbuilding, and weaponry. TA31 titanium alloy, with a nominal composition of Ti-6Al-3Nb-2Zr-1Mo, is a specialty titanium alloy independently developed in my country for shipbuilding. Due to its high strength, excellent impact toughness, formability, and weldability, it has been widely used in shipbuilding and marine engineering pressure hulls, sea-going pipelines, and other fields. Currently, TA31 titanium alloy is primarily used in large quantities in the form of bars, plates, cakes, and rings.

[0003] Usually, titanium alloy plates with a thickness of less than 100mm and a width of less than 1800mm need to be rolled into shape using large-tonnage rolling equipment. Due to the problems of small pass reduction and poor core penetration during the rolling process, the surface deformation of the plate is large, the deformation of the core is small, and the transverse and longitudinal deformation of the plate are quite different. There is obvious anisotropy in different positions and directions of the plate, especially the transverse and longitudinal strength difference reaches more than 30MPa.

[0004] Therefore, a forging method for high-uniformity TA31 titanium alloy plates is urgently needed. By adopting the forging forming method, starting from the forging processing technology, by controlling the temperature rise of the plate and improving the forgeability of the core, the uniformity of the structure and performance can be improved, and the anisotropy of the plate in the transverse and longitudinal directions can be reduced. Summary of the Invention

[0005] The present invention aims to overcome the shortcomings of the prior art by providing a forging method and application for highly uniform TA31 titanium alloy sheet materials. This method effectively improves the overall uniformity of the blank through three-dimensional homogenization forging in the X, Y, and Z directions. Furthermore, alternating stretching in the X and Y directions improves the microstructure uniformity of the finished sheet and reduces anisotropy. The method is particularly suitable for TA31 titanium alloy sheet materials with a thickness of 50 mm ≤ H ≤ 100 mm and a width of 1200 mm ≤ W ≤ 1800 mm.

[0006] To achieve the above object, the present invention provides the following technical solutions: In one aspect, the present invention provides a method for forging a high-uniformity TA31 titanium alloy plate, comprising the following steps: Step 1, blank forging: first heat the ingot and keep it warm, then perform upsetting and drawing to fully break up the coarse cast structure, with a deformation of 40% to 60%, and then water-cool it after forging to obtain blank A; Step 2, intermediate forging: In order to further refine and homogenize the structure of the blank, the blank A is first heated to a specific temperature above the phase transformation point and kept warm, and then subjected to X-, Y-, and Z-direction upsetting, with the deformation amount of each fire being 35% to 50%. In order to refine the grains, water cooling is adopted after each fire forging to obtain blank B; Step 3: Homogenization treatment: The blank B is first heated and held at a specific temperature below the phase transition point, and then uniformly cooled to obtain a blank C. By holding the temperature for a long time in a temperature range near the phase transition point, the deformed blank is given sufficient thermodynamic power to undergo recrystallization, further refining the grain size, thereby facilitating control of the structural uniformity and anisotropy of the finished plate. Step 4, finished product forging: first, the blank C is heated to a specific temperature below the phase transition point and kept warm, and then alternately stretched in the X and Y directions, with the deformation amount of each fire being 20% ​​to 40%, to finally obtain the required TA31 titanium alloy plate.

[0007] Specifically, in step 1, before heating, it is necessary to apply multiple coats of anti-oxidation coating on the surface of the ingot. The natural gas furnace is used for heating, and the heating temperature is 1200°C to 1300°C, which is conducive to sufficient diffusion of elements. The holding time = insulation coefficient × minimum side length of the cross section. The insulation coefficient is 0.6 min / mm to 1.2 min / mm, and the minimum side length of the cross section is in mm, to ensure that the ingot is fully and evenly heated.

[0008] Specifically, in step 2, the heating temperature is 20°C to 100°C above the phase transition point, the holding time = insulation coefficient × minimum side length of the cross section, the insulation coefficient is 0.6 min / mm to 1.2 min / mm, and the unit of the minimum side length of the cross section is mm; 3 to 5 fires of upsetting are performed in the form of square upsetting, and each fire is upsetting once in the X direction, Y direction and Z direction. The X direction, Y direction and Z direction of the blank are distinguished before upsetting.

[0009] Specifically, in step 3, the heating temperature is 10°C to 20°C below the phase change point, the holding time = insulation coefficient × minimum side length of the cross section, the insulation coefficient is 1.0 min / mm to 2.0 min / mm, and the unit of the minimum side length of the cross section is mm; the cooling rate during the uniform cooling is 3°C / min to 6°C / min.

[0010] Specifically, in step 4, the heating temperature is 30°C to 60°C below the phase transformation point, the holding time = holding coefficient × minimum side length of the cross section, the holding coefficient is 1.0 min / mm to 1.8 min / mm, and the minimum side length of the cross section is in mm; 3 to 5 fires of drawing are used, the forging rate during drawing is 70 mm / s to 90 mm / s, and the forging transfer time is controlled to be less than 60 s. By ensuring a relatively high initial forging temperature and forging rate, the blank is reduced by recovery and dynamic recrystallization during the forging process, thereby reducing anisotropy.

[0011] Specifically, in step 4, the anisotropy is reduced by alternately stretching in the X and Y directions and designing the deformation in the width and length directions to ensure that the deformation in the length direction / the deformation in the width direction is ≤ 2.0.

[0012] On the other hand, the present invention provides an application of a high-uniformity TA31 titanium alloy plate prepared by the forging method as described above, and its application in ships and marine engineering pressure hulls and sea pipelines.

[0013] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects: The forging method of the present invention can effectively improve the overall uniformity of the blank through three-dimensional homogenization forging in the X, Y, and Z directions. At the same time, through alternating stretching and forming in the X and Y directions, uniform plastic deformation can occur in both the X and Y directions during the plate forming process, thereby achieving the purpose of improving the uniformity of the finished plate structure and reducing anisotropy. Furthermore, the present invention innovatively proposes a production process for titanium alloy plates with small thickness and large width. Through the above process, the problem of large anisotropy of titanium alloy plates produced by traditional rolling methods can be solved. The use of this forging method can produce qualified TA31 titanium alloy plates that meet design requirements, have excellent structural uniformity and performance uniformity, and are suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings are incorporated in and constitute a part of this specification and, together with the description, serve to explain the principles of the invention.

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0016] Figure 1 is a flow chart of the forging method of the present invention; Figure 2 This is a microstructure sampling location diagram of the TA13 titanium alloy plate of the present invention; Figure 3 This is a macroscopic microstructure diagram of a TA13 titanium alloy plate with a thickness of H=50 mm in Example 1; Figure 4 : Microstructure of TA13 titanium alloy plate with thickness H=50 mm in Example 1; Figure 5 : Macrostructure of the TA13 titanium alloy plate with a thickness of H=100 mm in Example 2; Figure 6 : Microstructure diagram of TA13 titanium alloy plate with thickness H=100mm in Example 2. DETAILED DESCRIPTION

[0017] Exemplary embodiments will now be described in detail, with examples shown in the accompanying drawings. The embodiments described in the following exemplary embodiments are not intended to represent all embodiments consistent with the present invention. Instead, they are merely examples consistent with some aspects of the present invention as detailed in the appended claims.

[0018] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present invention is described in further detail below with reference to the accompanying drawings and embodiments.

[0019] The present invention provides a forging method for a high-uniformity TA31 titanium alloy plate, comprising the following steps: Step 1, blank forging: first heat the ingot and keep it warm, then perform upsetting and drawing to fully break up the coarse cast structure, with a deformation of 40% to 60%, and then water cool it after forging to obtain blank A; Step 2, intermediate forging: In order to further refine and homogenize the structure of the blank, the blank A is first heated to a specific temperature above the phase transformation point and kept warm, and then subjected to X-, Y-, and Z-direction upsetting, with the deformation amount of each fire being 35% to 50%. In order to refine the grains, water cooling is adopted after each fire forging to obtain blank B; Step 3: Homogenization treatment: The blank B is first heated and held at a specific temperature below the phase transition point, and then uniformly cooled to obtain a blank C. By holding the temperature for a long time in a temperature range near the phase transition point, the deformed blank is given sufficient thermodynamic power to undergo recrystallization, further refining the grain size, thereby facilitating control of the structural uniformity and anisotropy of the finished plate. Step 4, finished product forging: first, the blank C is heated to a specific temperature below the phase transition point and kept warm, and then alternately stretched in the X and Y directions, with the deformation amount of each fire being 20% ​​to 40%, to finally obtain the required TA31 titanium alloy plate.

[0020] Specifically, in step 1, before heating, it is necessary to apply multiple coats of anti-oxidation coating on the surface of the ingot. The natural gas furnace is used for heating, and the heating temperature is 1200°C to 1300°C, which is conducive to sufficient diffusion of elements. The holding time = insulation coefficient × minimum side length of the cross section. The insulation coefficient is 0.6 min / mm to 1.2 min / mm, and the minimum side length of the cross section is in mm, to ensure that the ingot is fully and evenly heated.

[0021] Specifically, in step 2, the heating temperature is 20°C to 100°C above the phase transition point, the holding time = insulation coefficient × minimum side length of the cross section, the insulation coefficient is 0.6 min / mm to 1.2 min / mm, and the unit of the minimum side length of the cross section is mm; 3 to 5 fires of upsetting are performed in the form of square upsetting, and each fire is upsetting once in the X direction, Y direction and Z direction. The X direction, Y direction and Z direction of the blank are distinguished before upsetting.

[0022] Specifically, in step 3, the heating temperature is 10°C to 20°C below the phase change point, the holding time = insulation coefficient × minimum side length of the cross section, the insulation coefficient is 1.0 min / mm to 2.0 min / mm, and the unit of the minimum side length of the cross section is mm; the cooling rate during the uniform cooling is 3°C / min to 6°C / min.

[0023] Specifically, in step 4, the heating temperature is 30°C to 60°C below the phase transformation point, the holding time = holding coefficient × minimum side length of the cross section, the holding coefficient is 1.0 min / mm to 1.8 min / mm, and the minimum side length of the cross section is in mm; 3 to 5 fires of drawing are used, the forging rate during drawing is 70 mm / s to 90 mm / s, and the forging transfer time is controlled to be less than 60 s. By ensuring a relatively high initial forging temperature and forging rate, the blank is reduced by recovery and dynamic recrystallization during the forging process, thereby reducing anisotropy.

[0024] Specifically, in step 4, the anisotropy is reduced by alternately stretching in the X and Y directions and designing the deformation in the width and length directions to ensure that the deformation in the length direction / the deformation in the width direction is ≤ 2.0.

[0025] It should be noted that the phase transition points referred to in this article are all β phase transition points.

[0026] In order to demonstrate the effectiveness of the forging method of the present invention, the following examples are provided for verification.

[0027] Example 1 This embodiment provides a forging method for a high-uniformity TA31 titanium alloy plate with a thickness of H=50 mm. The specific method is as follows: Step 1. Blanking forging: The ingot blanking temperature is 1250℃, and it is heated in a natural gas furnace. Before heating, the anti-oxidation coating is applied to the surface of the ingot three times. The holding time of the ingot is calculated according to 0.8 min / mm×(minimum side length of the cross section), and the deformation is controlled at 55%. The TA31 titanium alloy ingot is upset and drawn to fully break up the coarse cast structure. After forging, it is water-cooled to obtain billet A.

[0028] Step 2, intermediate forging: In order to further refine and homogenize the structure of the billet, it is heated at 70℃ above the phase transformation point. The holding time of billet A is calculated according to 0.9min / mm×(minimum side length of the cross section). It is upset and drawn 3 times. The deformation of each fire is controlled at 35%. Each fire adopts 3 upsetting and 3 drawing. The first time is upsetting and drawing along the X direction, the second time is upsetting and drawing along the Y direction, and the third time is upsetting and drawing along the Z direction. Water cooling is adopted after each forging to obtain billet B.

[0029] Step 3: Homogenization treatment: Heat and hold blank B at 15°C below the phase transition point. The holding time is calculated as 1.5 min / mm × (minimum side length of the cross section). After the holding period, the blank is taken out of the furnace and slowly cooled. The cooling rate is controlled at about 4°C / min to obtain blank C.

[0030] Step 4, finished product forging: the heating temperature of the billet C is 50°C below the phase transformation point, the holding time is calculated according to 1.3min / mm×(minimum side length of the cross section), and the drawing is divided into 4 times. The deformation of the finished plate during each fire during the drawing is 25%, the forging rate during the drawing is 80mm / s, and the forging transfer time is strictly controlled to be less than 60s. Each drawing is completed in two passes, 1 pass of X-direction drawing combined with 1 pass of Y-direction drawing; during the drawing, the total deformation in the width direction is 50%, the total deformation in the length direction is 80%, and the deformation in the length direction / the deformation in the width direction is 1.6; after forging, air cooling is performed to finally obtain the required TA31 titanium alloy plate X.

[0031] Example 2 This embodiment provides a forging method for a high-uniformity TA31 titanium alloy plate with a thickness of H=100 mm. The specific method is as follows: Step 1. Blanking forging: The ingot blanking temperature is 1300℃, and it is heated in a natural gas furnace. Before heating, the anti-oxidation coating is applied to the surface of the ingot three times. The holding time of the ingot is calculated according to 1.0 min / mm×(minimum side length of the cross section), and the deformation is controlled at 45%. The TA31 titanium alloy ingot is upset and drawn to fully break up the coarse cast structure. After forging, it is water-cooled to obtain billet A.

[0032] Step 2, intermediate forging: In order to further refine and homogenize the structure of the billet, it is heated at 80 ° C above the phase transformation point. The holding time of billet A is calculated according to 1.1 min / mm × (minimum side length of the cross section). The upsetting and drawing are performed 4 times, and the deformation of each fire is controlled at 40%. Each fire adopts 3 upsetting and 3 drawing. The first upsetting and drawing is along the X direction, the second upsetting and drawing is along the Y direction, and the third upsetting and drawing is along the Z direction. Water cooling is adopted after each forging to obtain billet B.

[0033] Step 3: Homogenization treatment: Heat and hold blank B at 20°C below the phase transition point. The holding time is calculated as 1.8 min / mm × (minimum side length of the cross section). After the holding period, the blank is taken out of the furnace and slowly cooled. The cooling rate is controlled at about 6°C / min to obtain blank C.

[0034] Step 4, finished product forging: the heating temperature of the billet C is 40 ° C below the phase transformation point, the holding time is calculated according to 1.7 min / mm×(minimum side length of the cross section), and the drawing is divided into 5 times. The deformation of the finished plate during each fire during the drawing is 30%, and the forging rate during the drawing is selected to be 90 mm / s. The forging transfer time is strictly controlled to be less than 60s. Each drawing is completed in two passes, 1 pass of X-direction drawing combined with 1 pass of Y-direction drawing; the total deformation in the width direction during the drawing is 60%, the total deformation in the length direction is 110%, and the deformation in the length direction / deformation in the width direction is 1.83; after forging, air cooling is performed to finally obtain the required TA31 titanium alloy plate Y.

[0035] Example 3 This embodiment provides a forging method for a high-uniformity TA31 titanium alloy plate with a thickness of H=70 mm. The specific method is as follows: Step 1. Blank forging: The blanking temperature of the ingot is 1200℃, and it is heated in a natural gas furnace. Before heating, the anti-oxidation coating is applied to the surface of the ingot three times. The holding time of the ingot is calculated according to 0.6 min / mm×(minimum side length of the cross section), and the deformation is controlled at 40%. The TA31 titanium alloy ingot is upset and drawn to fully break up the coarse cast structure. After forging, it is water-cooled to obtain billet A.

[0036] Step 2, intermediate forging: In order to further refine and homogenize the structure of the billet, it is heated at 30 ° C above the phase transformation point. The holding time of billet A is calculated according to 0.6 min / mm × (minimum side length of the cross section). The upsetting and drawing are performed 5 times, and the deformation of each fire is controlled at 50%. Each fire adopts 3 upsetting and 3 drawing. The first upsetting and drawing is along the X direction, the second upsetting and drawing is along the Y direction, and the third upsetting and drawing is along the Z direction. Water cooling is adopted after each forging to obtain billet B.

[0037] Step 3: Homogenization treatment: Heat and hold blank B at 10°C below the phase transition point. The holding time is calculated as 1.2 min / mm × (minimum side length of the cross section). After the holding period, the blank is taken out of the furnace and slowly cooled. The cooling rate is controlled at about 3°C / min to obtain blank C.

[0038] Step 4, finished product forging: the heating temperature of the billet C is 60°C below the phase transformation point, the holding time is calculated according to 1.0 min / mm×(minimum side length of the cross section), and the billet is drawn and formed in 3 times. The deformation of the finished plate during each fire during drawing is 40%, the forging rate during drawing is selected to be 70 mm / s, and the forging transfer time is strictly controlled to be less than 60 s. Each drawing is completed in two passes, 1 pass of X-direction drawing combined with 1 pass of Y-direction drawing; the total deformation in the width direction during drawing is 70%, the total deformation in the length direction is 119%, and the deformation in the length direction / deformation in the width direction is 1.7; air cooling is performed after forging to finally obtain the required TA31 titanium alloy plate Z.

[0039] To further verify the effectiveness of the technical solution provided by the present invention, mechanical properties tests were performed on the above-mentioned TA31 titanium alloy plate X and TA31 titanium alloy plate Y. The test results of TA31 titanium alloy plate X are shown in Table 1, and the test results of TA31 titanium alloy plate Y are shown in Table 2.

[0040] Table 1 Table 2 In summary, Figures 3 to 6 It can be seen that the macrostructure of the H=50mm and H=100mm plates is mainly characterized by fine semi-fuzzy crystals. The microstructure is composed of spherical primary α phase and lamellar secondary α phase. The microstructure is uniform from the edge to the core of the plate, and the content of primary α phase in different parts is basically the same, indicating that the forging deformation of the plate is uniform and sufficient. At the same time, it can be seen from Tables 1 and 2 that the mechanical properties results at different positions and directions show that the plates have good transverse and longitudinal uniformity, and the anisotropy is controlled within 10MPa, indicating that no obvious texture is formed in different directions of the plate, which meets the use requirements.

[0041] The foregoing description is intended only to provide specific embodiments of the present invention, which will enable those skilled in the art to understand and implement the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0042] It should be understood that the present invention is not limited to the above description and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A forging method for a high uniformity TA31 titanium alloy plate, characterized in that: The steps include: Step 1, blank forging: first heat the ingot and keep it warm, then perform upsetting with a deformation of 40% to 60%, and cool it after forging to obtain blank A; Step 2, intermediate forging: first, heating the blank A to a specific temperature above the phase transformation point and keeping the temperature, then performing upsetting in the X, Y and Z directions, with the deformation amount of each fire being 35% to 50%, and cooling after forging to obtain the blank B; Step 3: Homogenization treatment: first heating the blank B to a specific temperature below the phase transition point and keeping the temperature, and then uniformly cooling the blank to obtain the blank C; Step 4, finished product forging: first, the blank C is heated to a specific temperature below the phase transition point and kept warm, and then alternately stretched in the X and Y directions, with the deformation amount of each fire being 20% ​​to 40%, to finally obtain the required TA31 titanium alloy plate.

2. The forging method according to claim 1, characterized in that In step 1, before heating, the ingot surface needs to be coated with multiple layers of anti-oxidation coating. The ingot is heated in a natural gas furnace at a temperature of 1200°C to 1300°C. The holding time = holding coefficient × minimum side length of the cross section. The holding coefficient is 0.6 min / mm to 1.2 min / mm, and the minimum side length of the cross section is in mm. After forging, the ingot is water-cooled.

3. The forging method according to claim 1, wherein: In step 2, the heating temperature is 20°C to 100°C above the phase transition point, the holding time = insulation coefficient × minimum side length of the cross section, the insulation coefficient is 0.6 min / mm to 1.2 min / mm, and the minimum side length of the cross section is in mm; 3 to 5 fires of upsetting are performed in the form of square upsetting, and each fire is upsetting once in the X direction, Y direction, and Z direction.

4. The forging method according to claim 3, characterized in that Distinguish the X, Y and Z directions of the blank before upsetting.

5. The forging method according to claim 1, wherein: In step 3, the heating temperature is 10°C to 20°C below the phase change point, the holding time = insulation coefficient × minimum side length of the cross section, the insulation coefficient is 1.0 min / mm to 2.0 min / mm, and the unit of the minimum side length of the cross section is mm; the cooling rate during the uniform cooling is 3°C / min to 6°C / min.

6. The forging method according to claim 1, wherein: In step 4, the heating temperature is 30°C to 60°C below the phase transition point, the holding time = holding coefficient × minimum side length of the cross section, the holding coefficient is 1.0 min / mm to 1.8 min / mm, and the minimum side length of the cross section is in mm; 3 to 5 fires of drawing forming are adopted, the forging rate during drawing forming is 70 mm / s to 90 mm / s, and the forging transfer time is controlled to be less than 60 seconds.

7. The forging method according to claim 1, wherein: In step 4, the steel sheet is stretched alternately in the X and Y directions, and the deformation in the width and length directions is designed to ensure that the deformation in the length direction / the deformation in the width direction is ≤ 2.

0.

8. Application of a high-uniformity TA31 titanium alloy sheet prepared by the forging method according to any one of claims 1 to 7, characterized in that: Application in ships, marine engineering pressure hulls, and seagoing pipelines.

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