A TiAl alloy temperature-stress dual plasticization upsetting blank making method

Abstract

The present invention discloses a temperature-stress dual plasticization upsetting blank making method for TiAl alloy. The temperature-stress dual plasticization upsetting blank making method comprises the following steps: placing a TiAl bar into a first metal sleeve, then sealing both ends of the first metal sleeve and heating it to 1000-1400°C and keeping it warm for 30-240 minutes; heating the punch and base of a press to 400-1100°C and keeping it warm for 30-60 minutes; placing the first metal sleeve after being kept warm into a second metal sleeve, then placing the second metal sleeve on the base after being kept warm, and compressing the first metal sleeve with the punch after being kept warm, and completing the blank making after reaching the expected deformation amount. The present invention utilizes the tightening effect of the second metal sleeve during the upsetting of the TiAl bar to generate a three-dimensional compressive stress similar to that of extrusion forming, thereby improving the plasticity of the TiAl alloy, avoiding cracking, and obtaining a forging cake with a larger diameter than the original blank.

Description

Technical Field

[0001] The invention belongs to the technical field of material processing, and in particular relates to a TiAl alloy temperature-stress dual plasticization upsetting blank making method. Background Art

[0002] As a new generation of high-temperature resistant intermetallic compounds, TiAl alloy has achieved certain results in applications in the aerospace field due to its high specific strength and excellent creep properties, and has helped to achieve the goal of energy conservation and emission reduction. Therefore, it is considered to be one of the best new lightweight structural materials.

[0003] TiAl alloy ingots need to be opened and the cast structure broken before they can be used or further processed. However, due to the low plasticity and narrow thermal deformation process window of TiAl alloys, the opening operation is very difficult. Especially for the second-generation cast TiAl alloys, plastic deformation is almost impossible, and direct casting is usually used to manufacture parts. However, compared with parts that have undergone plastic deformation, the mechanical properties of the castings are poor, which has become a key factor limiting the further application of TiAl alloys.

[0004] Currently, the commonly used blanking methods for TiAl alloys include jacket forging and jacket extrusion. Jacket forging is to put the TiAl alloy into a jacket material, heat it together, and then forge and upset it as a whole. Jacket forging can obtain a forging cake with a larger diameter than the original billet. Since the strength of the jacket material at high temperature is much lower than that of the TiAl alloy, the jacket material mainly plays a role of heat preservation during the forging process. The edges of TiAl alloys are prone to cracking when subjected to tensile stress, so multiple forging and intermediate annealing are required to achieve a larger deformation. During the jacket extrusion process, the TiAl alloy is always under strong triaxial compressive stress, which can improve the plasticity of the alloy and reduce the tendency to crack, thereby achieving a large deformation. However, due to its forming characteristics, the jacket extrusion method can only produce extruded rods with a diameter smaller than the original billet. Summary of the Invention

[0005] To address the low plasticity, narrow thermal deformation window, and difficulty in forming TiAl alloys, the present invention proposes a temperature-stress dual-plasticization upsetting method for TiAl alloys. This method uses a stress metal sleeve (i.e., a second metal sleeve) to tighten the TiAl bar during upsetting, generating intense triaxial compressive stress similar to that experienced in extrusion. This significantly improves the plasticity of the TiAl alloy, prevents cracking, and produces forging cakes with a larger diameter than the original billet.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A TiAl alloy temperature-stress dual plasticization upsetting blank making method comprises the following steps:

[0008] (1) Place the TiAl rod into the first metal sleeve, seal both ends of the first metal sleeve, heat it to 1000-1400°C and keep it warm for 30-240 minutes, and set aside;

[0009] (2) Heat the punch and base of the press to 400~1100℃ and keep them warm for 30~60min, and set aside;

[0010] (3) Place the insulated first metal sleeve into the second metal sleeve, then place the second metal sleeve on the insulated base, and use the insulated punch to compress the first metal sleeve. After reaching the expected deformation, stop the compression and complete the upsetting blank.

[0011] Preferably, in step (1), the TiAl rod is coated with glass lubricant and then placed in the first metal sleeve.

[0012] Preferably, in step (1), gaskets are used to seal both ends of the first metal sleeve.

[0013] Preferably, the gasket is made of titanium alloy, stainless steel or nickel-based alloy. The gasket and the first metal sleeve are made of metals with low thermal conductivity and high melting point.

[0014] Preferably, in step (1), the inner diameter of the first metal sleeve is 0.1 to 0.5 mm larger than the diameter of the TiAl rod.

[0015] Preferably, in step (1), the ratio of the wall thickness to the inner diameter of the first metal sleeve is 1 / 6 to 1:1.

[0016] Preferably, in step (1), the material of the first metal sleeve is titanium alloy, stainless steel or nickel-based alloy.

[0017] Preferably, in step (3), the second metal sleeve is made of 40Cr steel, 42CrMo steel or H13 steel. The second metal sleeve is made of high-strength material to ensure that it can provide sufficient three-dimensional compressive stress.

[0018] Preferably, in step (3), the diameters of the base and the punch after thermal insulation expansion are 0.2-0.5 mm smaller than the inner diameter of the second metal sleeve, and the diameter of the first metal sleeve after thermal insulation expansion is 0.5-1 mm smaller than the inner diameter of the second metal sleeve.

[0019] Preferably, in step (3), the compression deformation rate is 0.1~10s -1 , the deformation is 50~90%.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] This method utilizes the securing effect of a stressed metal sleeve (i.e., a second metal sleeve) during the roughing process of a TiAl alloy bar. The resulting strong triaxial compressive stress, similar to that experienced during extrusion, significantly enhances the plasticity of the TiAl alloy and prevents cracking. Furthermore, this method can produce forging discs with a larger diameter than the initial billet. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the TiAl alloy temperature-stress dual plasticization upsetting blank making method of the present invention; wherein, 1-press upper table, 2-punch, 3-gasket, 4-first metal sleeve, 5-TiAl bar, 6-second metal sleeve, 7-base, 8-press lower table. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0024] See also Figure 1 , Figure 1 Figure 3 is a schematic diagram of the TiAl alloy temperature-stress dual plasticization upsetting blanking method according to the present invention. The upsetting blanking process is as follows: a TiAl bar stock 5 is placed in a first metal sleeve 4. The upper and lower ends of the first metal sleeve 4 are tightly sealed with gaskets 3. The first metal sleeve 4 is placed as a whole in a second metal sleeve 6. The second metal sleeve 6 contacts the lower table 8 of the press through a base 7 located inside the second metal sleeve 6. The upper table 1 of the press contacts the punch 2, pushing the punch 2 to compress the first metal sleeve 4, thereby upsetting the TiAl bar stock 5 located inside the first metal sleeve 4.

[0025] Example 1

[0026] A TiAl alloy temperature-stress dual plasticization upsetting blank making method, the steps are as follows:

[0027] Ti-48Al-2Cr-2Nb alloy (hereinafter referred to as TiAl bar) is used as the billet

[0028] (1) Apply glass lubricant to a TiAl rod with a diameter of 100 mm and a height of 100 mm and insert it into a TA1 titanium alloy insulation metal sleeve (i.e., the first metal sleeve) with an inner diameter of 100.2 mm and an outer diameter of 140 mm, and cover both ends with TA1 gaskets;

[0029] (2) Place the TA1 insulating metal sleeve containing the TiAl rod into a heating furnace and heat it to 1300°C and keep it warm for 180 minutes. At the same time, place the H13 punch and base mold with a diameter of 142 mm into another heating furnace and heat it to 600°C and keep it warm for 60 minutes.

[0030] (3) After the insulation is completed, the base made of H13 steel is first taken out from the heating furnace, and then placed on the lower table of the press together with a stress metal sleeve made of 40Cr with an inner diameter of 143 mm and an outer diameter of 200 mm (the temperature of the stress metal sleeve is room temperature, i.e., the second metal sleeve). Then, the insulation metal sleeve containing the TiAl rod is taken out from the heating furnace and placed in the stress metal sleeve. Finally, the punch is taken out from the heating furnace and placed in the stress metal sleeve, located above the insulation metal sleeve.

[0031] (4) The upper table of the press moves downward and continues to press down after contacting the punch, causing the punch to compress the insulating metal sleeve containing the TiAl rod, with a deformation rate of 1s -1 , the deformation is 70%;

[0032] (5) The base and punch are removed, and the stress and heat-insulating metal sleeve are removed by machining to obtain the deformed TiAl blank.

[0033] Example 2

[0034] A TiAl alloy temperature-stress dual plasticization upsetting blank making method, the steps are as follows:

[0035] Ti-45Al-8Nb alloy (hereinafter referred to as TiAl bar) is used as the blank

[0036] (1) Apply glass lubricant to a TiAl rod with a diameter of 30 mm and a height of 60 mm and insert it into a 304 stainless steel insulation metal sleeve with an inner diameter of 30.1 mm and an outer diameter of 100 mm (i.e., the first metal sleeve), and cover both ends with 304 stainless steel gaskets;

[0037] (2) Place the TA1 insulating metal sleeve containing the TiAl rod into a heating furnace and heat it to 1100°C and keep it warm for 120 minutes. At the same time, place the WRe25 tungsten-rhenium alloy punch and base mold with a diameter of 101 mm into another heating furnace and heat it to 900°C and keep it warm for 60 minutes.

[0038] (3) After the insulation is completed, the base made of N3 nickel-based alloy is first taken out from the heating furnace, and then placed on the lower table of the press together with a stress metal sleeve made of 42CrMo with an inner diameter of 102 mm and an outer diameter of 150 mm (the temperature of the stress metal sleeve is room temperature, i.e., the second metal sleeve), and then the insulation metal sleeve containing the TiAl rod is taken out from the heating furnace and placed in the stress metal sleeve. Finally, the punch is taken out from the heating furnace and placed in the stress metal sleeve, located above the insulation metal sleeve;

[0039] (4) The upper table of the press moves downward and continues to press down after contacting the punch, so that the punch compresses the insulating metal sleeve containing the TiAl bar, and the deformation rate is 10s -1 , the deformation is 50%;

[0040] (5) The base and punch are removed, and the stress and heat-insulating metal sleeve are removed by machining to obtain the deformed TiAl blank.

[0041] The specific embodiments of the present invention described above do not limit the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A TiAl alloy temperature-stress dual plasticizing upsetting blank making method, characterized in that: The steps include: (1) Place the TiAl rod into the first metal sleeve, seal both ends of the first metal sleeve, heat it to 1000-1400°C and keep it warm for 30-240 minutes, and set aside; (2) Heat the punch and base of the press to 400~1100℃ and keep them warm for 30~60min, and set aside; (3) Place the first metal sleeve after heat preservation into the second metal sleeve, then place the second metal sleeve on the heat-insulated base, and use the heat-insulated punch to compress the first metal sleeve. After reaching the expected deformation, stop the compression and complete the roughing and blanking.

2. The TiAl alloy temperature-stress dual plasticizing upsetting blank making method according to claim 1, characterized in that: In step (1), the TiAl rod is coated with glass lubricant and then placed in a first metal sleeve.

3. The TiAl alloy temperature-stress dual plasticizing upsetting blank making method according to claim 1, characterized in that: In step (1), gaskets are used to seal both ends of the first metal sleeve.

4. The TiAl alloy temperature-stress dual plasticizing upsetting method according to claim 3, characterized in that: The material of the gasket is titanium alloy, stainless steel or nickel-based alloy.

5. The TiAl alloy temperature-stress dual plasticizing upsetting blank making method according to claim 1, characterized in that: Step (1) The inner diameter of the first metal sleeve is 0.1-0.5 mm larger than the diameter of the TiAl rod.

6. The TiAl alloy temperature-stress dual plasticizing upsetting blank making method according to claim 5, characterized in that: In step (1), the ratio of the wall thickness to the inner diameter of the first metal sleeve is 1 / 6 to 1:

1.

7. The TiAl alloy temperature-stress dual plasticizing upsetting blank making method according to claim 1, characterized in that: Step (1) The first metal sleeve is made of titanium alloy, stainless steel or nickel-based alloy.

8. The TiAl alloy temperature-stress dual plasticizing upsetting blank making method according to claim 1, characterized in that: In step (3), the second metal sleeve is made of 40Cr steel, 42CrMo steel or H13 steel.

9. The TiAl alloy temperature-stress dual plasticizing upsetting blank making method according to claim 1, characterized in that: In step (3), the diameters of the base and the punch after thermal insulation expansion are 0.2-0.5 mm smaller than the inner diameter of the second metal sleeve, and the diameter of the first metal sleeve after thermal insulation expansion is 0.5-1 mm smaller than the inner diameter of the second metal sleeve.

10. The TiAl alloy temperature-stress dual plasticizing upsetting blank making method according to claim 1, characterized in that: The compression deformation rate in step (3) is 0.1~10s -1 , the deformation is 50~90%.

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