TiAl alloy temperature-stress double-plasticizing upsetting blank making method

Abstract

The invention discloses a TiAl alloy temperature-stress double plasticizing upsetting blank making method. The temperature-stress double-plasticizing upsetting blank making method comprises the following steps that a TiAl bar is put into a first metal sleeve, then the two ends of the first metal sleeve are closed, then the first metal sleeve is heated to 1000-1400 DEG C, and heat preservation is conducted for 30-240 min; a punch and a base of the press machine are heated to 400 DEG C to 1100 DEG C, and heat preservation is conducted for 30 min to 60 min; and the first metal sleeve obtained after heat preservation is placed in a second metal sleeve, then the second metal sleeve is placed on a base obtained after heat preservation, the punch obtained after heat preservation is adopted for compressing the first metal sleeve, and after the expected deformation is achieved, blank manufacturing is completed. According to the method, the fastening effect of the second metal sleeve during upsetting forming of the TiAl bar is utilized, three-way pressure stress similar to extrusion forming is generated, the plasticity of the TiAl alloy is improved, cracking is avoided, and a forging cake with the diameter larger than that of an original blank can be obtained.

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 plasticizing upsetting blank making method. Background Art

[0002] As a new generation of high-temperature resistant intermetallic compounds, TiAl alloy has achieved certain results in the application of aerospace due to its high specific strength and excellent creep performance, 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 alloy, the opening operation is very difficult. Especially for the second-generation cast TiAl alloy, plastic deformation is almost impossible, and direct casting is usually used to manufacture parts. However, compared with parts that have been plastically deformed, the mechanical properties of the castings are poor, which has become a key factor limiting the further application of TiAl alloys.

[0004] At present, the commonly used blanking methods for TiAl alloys include jacket forging and jacket extrusion. Jacket forging is to put TiAl alloy into a jacket material, heat it together, and then forge and upset it as a whole. Through jacket forging, a forging cake with a larger diameter than the original billet can be obtained. Since the strength of the jacket material at high temperature is much lower than that of TiAl alloy, the jacket material mainly plays a role of heat preservation during the forging process. The edge of TiAl alloy is prone to cracks when subjected to tensile stress, so multiple forging and intermediate annealing are required to achieve a larger deformation. During the jacket extrusion process, TiAl alloy is always under strong triaxial compressive stress, which can improve the plasticity of the alloy and reduce the tendency of cracking, 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] In view of the problems of low plasticity, narrow thermal deformation process window and great difficulty in blanking of existing TiAl alloys, the purpose of the present invention is to propose a temperature-stress dual plasticization upsetting method for TiAl alloys. The present invention generates strong three-dimensional compressive stress similar to extrusion forming by tightening the TiAl bar material during upsetting blanking by a stress metal sleeve (i.e., a second metal sleeve), thereby greatly improving the plasticity of the TiAl alloy and avoiding cracking. At the same time, a forging cake with a larger diameter than the original blank can be obtained.

[0006] The purpose of the present invention is achieved through the following technical solutions: A TiAl alloy temperature-stress dual plasticizing upsetting blank making method comprises the following steps: (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 for later use; (2) Heat the punch and base of the press to 400~1100℃ and keep them warm for 30~60min for standby use; (3) The heat-insulated first metal sleeve is placed into the second metal sleeve, and then the second metal sleeve is placed on the heat-insulated base. The heat-insulated punch is used to compress the first metal sleeve. After the expected deformation is achieved, the compression is stopped to complete the upsetting and blanking.

[0007] Preferably, in step (1), the TiAl rod is coated with glass lubricant and then placed in the first metal sleeve.

[0008] Preferably, in step (1), gaskets are used to seal both ends of the first metal sleeve.

[0009] 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.

[0010] Preferably, in step (1), the inner diameter of the first metal sleeve is 0.1-0.5 mm larger than the diameter of the TiAl rod.

[0011] 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.

[0012] Preferably, in step (1), the first metal sleeve is made of titanium alloy, stainless steel or nickel-based alloy.

[0013] 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 sufficiently large three-dimensional compressive stress.

[0014] Preferably, in step (3), the diameters of the base and the punch after thermal 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 expansion is 0.5-1 mm smaller than the inner diameter of the second metal sleeve.

[0015] Preferably, in step (3), the compression deformation rate is 0.1~10s -1 , the deformation is 50~90%.

[0016] Compared with the prior art, the beneficial effects of the present invention include: The present invention utilizes the fixing effect of the stress metal sleeve (i.e., the second metal sleeve) during the roughing process of the TiAl alloy bar, and the strong triaxial compressive stress similar to extrusion molding generated thereby significantly enhances the plasticity of the TiAl alloy and prevents the material from cracking. In addition, this method can also produce forging round cakes with a larger diameter than the initial billet. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the TiAl alloy temperature-stress dual plasticizing 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

[0018] In order to make the purpose, technical solution 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 used to limit the present invention.

[0019] See also Figure 1 , Figure 1 Schematic diagram of the temperature-stress dual plasticization upsetting blank making method of TiAl alloy of the present invention. The upsetting blank making process is as follows: TiAl bar 5 is placed in the first metal sleeve 4, the upper and lower ends of the first metal sleeve 4 are tightly closed with gaskets 3, the first metal sleeve 4 is placed as a whole in the second metal sleeve 6, the second metal sleeve 6 contacts with the lower table 8 of the press through the base 7 located inside the second metal sleeve 6, the upper table 1 of the press contacts with the punch 2, pushing the punch 2 to compress the first metal sleeve 4, thereby upsetting the TiAl bar 5 located inside the first metal sleeve 4.

[0020] Example 1 A TiAl alloy temperature-stress dual plasticizing upsetting blank making method, the steps are as follows: Ti-48Al-2Cr-2Nb alloy (hereinafter referred to as TiAl bar) is used as the blank (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 with an inner diameter of 100.2 mm and an outer diameter of 140 mm (i.e., the first metal sleeve), and cover both ends with TA1 gaskets; (2) Place the TA1 insulating metal sleeve containing the TiAl rod in a heating furnace and heat it to 1300°C for 180 minutes. At the same time, place the H13 punch and base mold with a diameter of 142 mm in another heating furnace and heat it to 600°C for 60 minutes. (3) After the insulation is completed, the base made of H13 steel is first taken out of 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), and then the insulation metal sleeve containing the TiAl rod is taken out of the heating furnace and placed in the stress metal sleeve. Finally, the punch is taken out of the heating furnace and placed in the stress metal sleeve, located above the insulation metal sleeve; (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%; (5) The base and punch are removed, and the stress and heat-insulating metal sleeve are removed by mechanical processing to obtain the deformed TiAl blank.

[0021] Example 2 A TiAl alloy temperature-stress dual plasticizing upsetting blank making method, the steps are as follows: Ti-45Al-8Nb alloy (hereinafter referred to as TiAl bar) is used as the blank (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; (2) Place the TA1 insulating metal sleeve containing the TiAl rod in a heating furnace and heat it to 1100°C for 120 minutes. At the same time, place the WRe25 tungsten-rhenium alloy punch and base mold with a diameter of 101 mm in another heating furnace and heat it to 900°C for 60 minutes. (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; (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 rod, and the deformation rate is 10s -1 , the deformation is 50%; (5) The base and punch are removed, and the stress and heat-insulating metal sleeve are removed by mechanical processing to obtain the deformed TiAl blank.

[0022] The specific implementation of the present invention described above does not constitute a limitation on the protection scope 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 protection scope 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) placing a TiAl rod into a first metal sleeve, sealing both ends of the first metal sleeve, heating the sleeve to 1000-1400° C. and keeping the temperature for 30-240 min for later use; (2) Heat the punch and base of the press to 400~1100℃ and keep them warm for 30~60min for standby use; (3) The first metal sleeve after heat preservation is placed in the second metal sleeve, and then the second metal sleeve is placed on the heat-insulated base. The first metal sleeve is compressed by the heat-insulated punch. After the expected deformation is achieved, the compression is stopped to complete the upsetting blank.

2. The TiAl alloy temperature-stress dual plasticizing upsetting blank making method according to claim 1, characterized in that: 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 blank making 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: 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: Step (3) The material of the second metal sleeve is 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 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 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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