A method for controlling microstructure and properties of high forging ratio difference TA15 titanium alloy component

Abstract

The application belongs to the technical field of metal material hot working, and particularly relates to a microstructure and performance regulation method for high-forging-ratio TA15 titanium alloy components. The method comprises the following steps: S1: blank heating, placing the blank in a heating furnace to heat to T1 temperature and heat penetration; S2: blank fast forging, taking the blank out of the furnace after heat penetration, performing multi-fire-time forging to prepare a blank on a fast forging machine to obtain an intermediate blank; S3: intermediate blank heating, placing the intermediate blank in the heating furnace to heat to T2 temperature and heat penetration; S4: die forging, taking the intermediate blank out of the furnace after heat penetration, performing die forging on a die forging press to obtain a final forging piece; and S5: post-forging treatment. The application effectively improves the internal microstructure uniformity and strength level of the high-forging-ratio TA15 titanium alloy forging piece by adjusting the forging heating temperature and deformation distribution in the blank preparation and die forging processes without increasing the remaining processes, so that the strength level is 30 MPa higher than the standard requirement.

Description

Technical Field

[0001] This invention belongs to the field of hot working technology of metal materials, specifically a method for controlling the microstructure and properties of TA15 titanium alloy components with high forging ratio difference. Background Technology

[0002] Titanium alloys possess excellent comprehensive properties, including high specific strength, corrosion resistance, low-temperature resistance, non-magnetic properties, and good biocompatibility. They are increasingly used in key components across industries such as aerospace, marine engineering, petrochemicals, and civilian applications, particularly in the aerospace sector. Simultaneously, with the increasing demand for lightweight aircraft, load-bearing components are becoming more complex, integrated, and modular. TA15 is a near-alpha titanium alloy with excellent comprehensive mechanical properties and is widely used in load-bearing components of multiple aircraft models.

[0003] Figure 1 This demonstrates a load-bearing component for an aircraft, including a large-section end and a small-section end. Currently, this is aimed at... Figure 1 The forging production of complex components, as shown, typically employs a high-speed forging mill with better controllability for the pre-forging billet manufacturing. However, due to the complexity of the components and the large differences in their cross-sections (the ratio of large to small cross-sections exceeding 3 times), a large forging ratio difference exists at different locations during the forging process. Typically, the forging ratio at high-strain locations is more than 3 times that at low-strain locations. This high forging ratio difference results in extremely uneven microstructure and properties of the forgings, and areas with high forging ratios exhibit low strength and substandard performance. Summary of the Invention

[0004] This invention provides a method for controlling the microstructure and properties of TA15 titanium alloy components with high forging ratio differences, which solves the problems of uneven internal microstructure and low strength level of forgings with high forging ratio differences, improves the strength level of forgings at high forging ratio positions, and makes the overall performance of forgings qualified with a margin ≥30MPa.

[0005] The technical solution adopted by this invention to solve its technical problem is a method for controlling the microstructure and properties of TA15 titanium alloy components with high forging ratio difference, comprising the following steps:

[0006] S1: Billet heating. The billet is placed in a heating furnace and heated to temperature T1 and held at that temperature until fully heated. (T...) β -60℃)≤T1≤(T β -40℃); T β This refers to the β-phase transformation temperature of titanium alloys.

[0007] S2: Billet fast forging. After the billet is fully heated, it is taken out of the furnace and forged in multiple passes on a fast forging mill to obtain an intermediate billet. The overall deformation of one end of the intermediate billet is ε1, and the overall deformation of the other end of the intermediate billet is ε2. The intermediate billet smoothly transitions from the end with deformation ε1 to the other end with deformation ε2, where ε1 < ε2. When forging on the fast forging mill, the deformation of each pass at both ends of the intermediate billet is 0% or 10%-40%.

[0008] S3: Heating of intermediate billet. The intermediate billet is placed in a heating furnace and heated to temperature T2 and kept at that temperature until fully heated. Where (T1+5℃)≤T2≤(T1+20℃).

[0009] S4: Die forging. After the intermediate billet is fully heated, it is taken out of the furnace and die forged on a die forging press. The deformation of the intermediate billet is ε3, where 25%≤ε3≤50%, to obtain the final forging.

[0010] S5: Post-forging treatment, cooling the final forging to 600°C at a rate of 30°C / min or higher, followed by air cooling to room temperature.

[0011] Furthermore, in step S2, if the surface temperature of the billet is lower than the final forging temperature during the second forging, it needs to be kept in the furnace for 15-30 minutes to achieve uniform temperature.

[0012] Furthermore, in step S1, the heat preservation time of the billet is (0.5-1)*d minutes, where d is the minimum thickness of the maximum cross section of the billet, in mm.

[0013] Furthermore, in step S4, the forging deformation rate is controlled to be 1-10 mm / s.

[0014] Furthermore, the heating furnace adopts an electric furnace with a heating accuracy of ±10℃ or better.

[0015] The beneficial effects of this invention are: Based on fast forging billet making, this invention effectively improves the internal structure uniformity and strength level of TA15 titanium alloy forgings with high forging ratio difference by adjusting the distribution of forging heating temperature and deformation amount in the billet making and die forging processes without adding other processes, so as to meet the standard requirements and achieve a strength level margin of ≥30MPa. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the forging of the present invention;

[0017] Figure 2 This is a flowchart of the present invention. Detailed Implementation

[0018] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0019] like Figure 2 As shown, the present invention provides a method for controlling the microstructure and properties of TA15 titanium alloy components with high forging ratio differences, comprising the following steps:

[0020] S1: Billet heating. The billet is placed in a heating furnace and heated to temperature T1 and held at that temperature until fully heated. (T...) β -60℃)≤T1≤(T β -40℃); T β The β-phase transformation temperature of titanium alloys; by adjusting the billet temperature at (T... β -60℃ to (T β Heating in the α+β region (-40℃) avoids grain coarsening; and since the temperature of the billet core rises during forging on the high-speed forging mill, controlling the billet temperature can prevent the temperature from exceeding T during forging on the high-speed forging mill. β This ensures the homogeneity of the α and β phases.

[0021] S2: Rapid forging of billets. After the billets are fully heated, they are removed from the furnace and forged in multiple passes on a rapid forging mill to obtain intermediate billets. The overall deformation at one end of the intermediate billet is ε1, and the overall deformation at the other end is ε2. The transition from the end with deformation ε1 to the end with deformation ε2 is smooth, with ε1 < ε2. A deformation gradient of ε1 < ε2 is preset in the rapid forging process (larger deformation at the smaller cross-section end and smaller deformation at the larger cross-section end) to pre-compensate for the forging ratio difference in subsequent die forging. During forging on the rapid forging mill, the deformation at both ends of the intermediate billet per pass is 0% or 10%-40%. Due to the existence of a critical deformation zone with a deformation of 1-9%, if the deformation is too small in the critical deformation zone, secondary α phase and grain growth will occur, which is not conducive to strength improvement, and the spheroidization effect of the primary α phase will be poor. If the deformation exceeds 40%, a texture structure is easily formed, resulting in anisotropy and large differences in strength levels.

[0022] S3: Heating the intermediate billet. The intermediate billet is placed in a heating furnace and heated to temperature T2 and held at that temperature until fully heated, where (T1+5℃)≤T2≤(T1+20℃). The temperature is then raised to T2=T1+(5~20)℃ and reheated to improve the material's plasticity. Increasing the intermediate billet heating temperature increases the dissolution of the primary α phase, resulting in the precipitation of more secondary α phase after forging and cooling. This allows for adjustment of the α-to-β phase volume ratio. Simultaneously, since the deformation rate and amount can be well controlled during die forging, it effectively reduces backheating of the billet caused by high pressing speed, ensuring that the core temperature of the intermediate billet remains below Tβ during die forging.

[0023] S4: Die forging. After the intermediate billet is fully heated, it is taken out of the furnace and die forged on a die forging press. The deformation of the intermediate billet is ε3, where 25%≤ε3≤50%, to obtain the final forging. It should be noted that the deformation of both the large end and the small end is within the range of 25%-50%. The large end refers to the end of the intermediate billet with a deformation of ε1, and the small end refers to the end of the intermediate billet with a deformation of ε2. By controlling the deformation of the intermediate billet, dynamic recrystallization in the high forging ratio region is promoted, and the uniformity of the microstructure and properties of the forging is improved. Steps S1 and S2 control the uniformity of α and β phases, and steps S3 and S4 control the volume ratio of α and β phases, so that the strength of the high forging ratio area is increased by ≥30MPa and the overall performance is qualified.

[0024] S5: Post-forging treatment, cooling the final forging to 600°C at a rate of ≥30°C / min, followed by air cooling to room temperature. By controlling the cooling rate of the forging to ≥30°C / min to 600°C, followed by air cooling, the grain size can be refined, improving the strength of the high forging ratio zone.

[0025] Furthermore, in step S1, the heat preservation time of the billet is (0.5-1)*d minutes, where d is the minimum thickness of the maximum cross section of the billet, in mm.

[0026] Furthermore, in step S4, the forging deformation rate is controlled to be 1-10 mm / s. By limiting the forging rate range to 1-10 mm / s, it is avoided that the rate is too high, which may cause cracks or increase the core temperature and produce coarse grain structure, while the rate is too low, which may affect dynamic recrystallization.

[0027] Furthermore, the heating furnace adopts an electric furnace with a heating accuracy of ±10℃ or better.

[0028] Example 1

[0029] TA15 titanium alloy β phase transformation point T β =1000℃;

[0030] Forging structure: small end section 180×90mm (high forging ratio zone), large end section 480×140mm (forging ratio difference 3.2 times);

[0031] Equipment: ±10℃ precision electric furnace, high-speed forging machine, die forging press

[0032] (1) Bar preparation: Flatten and chamfer the bar with a specification of φ300×260mm.

[0033] (2) Heating of billet: Heating in an electric furnace with heating accuracy of ±10℃ or better, heating temperature of 950℃, holding time of 180min.

[0034] (3) Billet forging: After the billet is fully heated, it is taken out of the furnace and drawn into a billet on a high-speed forging machine. The cross-sectional dimensions of the small end of the test piece per forging are controlled as follows: 300×220mm, 280×190mm, 200×190mm, 200×140mm, 180×115mm, 180×90mm; the dimensions of the large end of the test piece per forging are controlled as follows: 410×220mm, 460×190mm, 460×190mm, 480×140mm, 480×140mm, 480×140mm. That is, the deformation per forging is 0%, or 10%-40%; if the inner surface temperature of the forging is lower than the final forging temperature, i.e. 950℃, the holding time in the forging is 15min.

[0035] (4) Die forging heating: an electric furnace with heating accuracy of ±10℃ or better is used to heat the material at 965℃.

[0036] (5) Die forging: After the billet is heated through, it is taken out of the furnace and die forged on a die forging press. The deformation amount is controlled at 35% and the deformation rate is 1mm / s to obtain the final forging.

[0037] (6) Cool the final forging to 600°C at a rate of 30°C / min, and then air cool to room temperature.

[0038] (7) Physicochemical testing: Microstructure, low magnification structure and tensile properties of experimental forgings are tested.

[0039] Example 2

[0040] TA15 titanium alloy β phase transformation point T β =1000℃;

[0041] Forging structure: small end section 180×90mm (high forging ratio zone), large end section 480×140mm (forging ratio difference 3.2 times);

[0042] Equipment: ±10℃ precision electric furnace, high-speed forging machine, die forging press;

[0043] (1) Bar preparation: Flatten and chamfer the bar with a specification of φ300×260mm.

[0044] (2) Heating of billet: Heating in an electric furnace with heating accuracy of ±10℃ or better, heating temperature of 940℃, holding time of 130min.

[0045] (3) Billet forging: After the billet is fully heated, it is taken out of the furnace and drawn into a billet on a high-speed forging machine. The cross-sectional dimensions of the small end of the test piece per forging are controlled as follows: 300×220mm, 280×190mm, 200×190mm, 200×140mm, 180×115mm, 180×90mm; the dimensions of the large end of the test piece per forging are controlled as follows: 410×220mm, 460×190mm, 460×190mm, 480×140mm, 480×140mm, 480×140mm. The deformation amount per forging is 0% or 10%-40%. If the surface temperature inside the forging is lower than the final forging temperature, i.e. 940℃, the inner surface temperature is kept in the furnace for 25 minutes inside the forging.

[0046] (4) Forging heating: A ±10℃ precision electric furnace is used to heat through at 960℃.

[0047] (5) Die forging: After the billet is heated through, it is taken out of the furnace and die forged on a die forging press. The deformation amount is controlled at 50% and the deformation rate is 5mm / s.

[0048] (6) Post-forging treatment: Cool the forging to 600°C at a rate of 45°C / min, and then air cool to room temperature.

[0049] (7) Physicochemical testing: The microstructure, low magnification structure and tensile properties of the forgings are tested.

[0050] Example 3

[0051] TA15 titanium alloy β phase transformation point T β =1000℃;

[0052] Forging structure: small end section 180×90mm (high forging ratio zone), large end section 480×140mm (forging ratio difference 3.2 times);

[0053] Equipment: ±10℃ precision electric furnace, high-speed forging machine, die forging press;

[0054] (1) Bar preparation: Flatten and chamfer the bar with a specification of φ300×260mm.

[0055] (2) Heating of billet: Heating in an electric furnace with heating accuracy of ±10℃ or better, heating temperature of 960℃, holding time of 180min.

[0056] (3) Billet forging: After the billet is fully heated, it is taken out of the furnace and drawn into a billet on a high-speed forging machine. The cross-sectional dimensions of the small end of the test piece per forging are controlled as follows: 300×220mm, 280×200mm, 220×190mm, 200×140mm, 180×100mm, 180×90mm; the dimensions of the large end of the test piece per forging are controlled as follows: 400×220mm, 450×190mm, 460×190mm, 480×140mm, 480×140mm, 480×140mm. The deformation amount per forging is 0% or 10%-40%. If the surface temperature inside the forging is lower than the final forging temperature, i.e., 960℃, the billet is held in the furnace for 30 minutes inside the forging.

[0057] (4) Forging heating: A ±10℃ precision electric furnace is used to heat through at 965℃.

[0058] (5) Die forging: After the billet is heated through, it is taken out of the furnace and die forged on a die forging press. The deformation amount is controlled at 25% and the deformation rate is 10mm / s.

[0059] (6) Post-forging treatment: Cool the forging to 600°C at a rate of 45°C / min, and then air cool to room temperature.

[0060] (7) Physicochemical testing: The microstructure, low magnification structure and tensile properties of the forgings are tested.

[0061] Comparative Example 1

[0062] TA15 titanium alloy β phase transformation point T β =1000℃;

[0063] Forging structure: small end section 180×90mm (high forging ratio zone), large end section 480×140mm (forging ratio difference 3.2 times);

[0064] Equipment: ±10℃ precision electric furnace, high-speed forging machine, die forging press

[0065] (1) Bar preparation: Flatten and chamfer the bar with a specification of φ300×260mm.

[0066] (2) Heating of billet: Heating in an electric furnace with heating accuracy of ±10℃ or better, heating temperature of 980℃, holding time of 180min.

[0067] (3) Billet forging: Forging is carried out using a high-speed forging machine to form an intermediate billet. The deformation at both ends of the intermediate billet is the same.

[0068] (5) Die forging: After the billet is heated through, it is taken out of the furnace and die forged on a die forging press. The deformation is controlled at 35% to obtain the final forging. Then it is air-cooled to room temperature.

[0069] (6) Physicochemical testing: Microstructure, low magnification structure and tensile properties of experimental forgings are tested.

[0070] Longitudinal performance data of the test piece

[0071]

[0072] As shown in the table above, the mechanical properties of the core of TA15 titanium alloy components treated with this method are significantly improved.

[0073] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for controlling the microstructure and properties of TA15 titanium alloy components with high forging ratio difference, characterized in that, Includes the following steps: S1: Billet heating. The billet is placed in a heating furnace and heated to temperature T1 and held at that temperature until fully heated. (T...) β -60℃)≤T1≤(T β -40℃); T β This refers to the β-phase transformation temperature of titanium alloys. S2: Billet fast forging. After the billet is fully heated, it is taken out of the furnace and forged in multiple passes on a fast forging mill to obtain an intermediate billet. The overall deformation of one end of the intermediate billet is ε1, and the overall deformation of the other end of the intermediate billet is ε2. The intermediate billet smoothly transitions from the end with deformation ε1 to the other end with deformation ε2, where ε1 < ε2. When forging on the fast forging mill, the deformation of each pass at both ends of the intermediate billet is 0% or 10%-40%. S3: Heating of intermediate billet. The intermediate billet is placed in a heating furnace and heated to temperature T2 and kept at that temperature until fully heated. Where (T1+5℃)≤T2≤(T1+20℃). S4: Die forging. After the intermediate billet is fully heated, it is taken out of the furnace and die forged on a die forging press. The deformation of the intermediate billet is ε3, where 25%≤ε3≤50%, to obtain the final forging. S5: Post-forging treatment, cooling the final forging to 600°C at a rate of 30°C / min or higher, followed by air cooling to room temperature.

2. The method for controlling the microstructure and properties of TA15 titanium alloy components with high forging ratio difference as described in claim 1, characterized in that, In step S2, if the surface temperature of the billet is lower than the final forging temperature during the second forging, it needs to be kept in the furnace for 15-30 minutes to achieve uniform temperature.

3. The method for controlling the microstructure and properties of TA15 titanium alloy components with high forging ratio difference as described in claim 1, characterized in that, In step S1, the holding time of the billet is (0.5-1)*d minutes, where d is the minimum thickness of the maximum cross section of the billet, in mm.

4. The method for controlling the microstructure and properties of TA15 titanium alloy components with high forging ratio difference as described in claim 1, characterized in that, In step S4, the forging deformation rate is controlled to be 1-10 mm / s.

5. The method for controlling the microstructure and properties of TA15 titanium alloy components with high forging ratio difference as described in claim 1, characterized in that, The heating furnace is an electric furnace with a heating accuracy of ±10℃ or better.

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