Blanking and forging method of TC4-DT titanium alloy

Abstract

The invention discloses a TC4-DT titanium alloy cogging forging method which is characterized by comprising the following steps: carrying out cogging forging on a TC4-DT titanium alloy cast ingot to obtain a first forging stock; performing intermediate forging on the first forging stock to obtain a second forging stock; the second forging stock is subjected to forming forging, and a bar blank is obtained; and the bar blank is subjected to heat treatment, and the TC4-DT titanium alloy bar is obtained. By the adoption of the cogging forging method of the TC4-DT titanium alloy, the overall performance of the TC4-DT titanium alloy is obviously improved, the ductility can be improved by 50% or above compared with a traditional bar, the fracture toughness can be improved by 15% or above compared with the traditional bar, and good matching of the TC4-DT titanium alloy material in the aspects of strength, plasticity and toughness can be better achieved.

Description

Technical Field

[0001] The present invention relates to an ingot forging method, and particularly to an ingot forging method for TC4-DT titanium alloy. Background Art

[0002] The development of the aerospace industry must rely on the promotion of advanced materials. In recent years, with the development of fracture mechanics and damage tolerance theory, the design criteria of aircraft components have changed. Currently, high damage tolerance titanium alloys have become a research field of titanium alloys. Numerous studies have shown that titanium alloys can obtain high damage tolerance performance through β forging or β heat treatment, that is, the lamellar structure of titanium alloys has high fracture toughness and low crack propagation rate. However, β forging or β heat treatment results in obvious reduction of the plasticity of the material due to the formation of coarse lamellar structure. Therefore, in order to improve the damage tolerance performance of titanium alloys without reducing the plasticity of the material, it is urgent to design a processing method suitable for two-phase titanium alloys.

[0003] The traditional processing method of high damage tolerance TC4-DT titanium alloy bars is mainly to perform ingot forging in the β phase region, finally forge into bars in the two-phase region, and then obtain the lamellar structure through heat treatment in the β phase region, or to perform ingot forging in the β phase region and finally forge into bars in the β phase region, and then obtain the lamellar structure through heat treatment in the β phase region. The TC4-DT titanium alloy bars obtained by the traditional process can obtain high strength, fracture toughness and crack propagation rate, but the plasticity of the alloy is poor, which is not conducive to the comprehensive matching of the strength, plasticity and toughness of the alloy. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an ingot forging method for TC4-DT titanium alloy, which can improve the overall performance and better realize the good matching of TC4-DT titanium alloy material in terms of strength, plasticity and toughness.

[0005] In order to solve the above problems, the technical solution of the ingot forging method for TC4-DT titanium alloy of the present invention includes the following steps:

[0006] Step 1: Perform ingot forging on the TC4-DT titanium alloy ingot to obtain the first forging blank; the ingot forging adopts the forging method of repeated upsetting and drawing, and is completed in 1 to 3 heating times. The starting forging temperature of each heating time of ingot forging is 100°C to 200°C above the β phase transformation point, and the final forging temperature of each heating time of ingot forging is 50°C to 100°C below the β phase transformation point. The cumulative deformation amount of the ingot forging is 60% to 80%;

[0007] Step 2: Intermediate forging is performed on the first forging blank described in Step 1 to obtain a second forging blank; the intermediate forging is carried out by means of repeated upsetting and drawing, and is completed in 2 to 3 heating times. The starting forging temperature for each heating time of the intermediate forging is 50°C to 100°C above the β phase transformation point, and the final forging temperature for each heating time of the intermediate forging is 50°C to 100°C below the β phase transformation point. The cumulative deformation amount of the intermediate forging is 50% to 70%;

[0008] Step 3: Forming forging is performed on the second forging blank described in Step 2 to obtain a bar blank; the forming forging is carried out by means of repeated upsetting and drawing, and is completed in 1 to 2 heating times. The starting forging temperature for each heating time of the forming forging is 5°C to 50°C above the β phase transformation point, and the final forging temperature for each heating time of the forming forging is 50°C to 80°C below the β phase transformation point. The cumulative deformation amount of the forming forging is 60% to 75%;

[0009] Step 4: The bar blank described in Step 3 is heat-treated to obtain a TC4-DT titanium alloy bar; the specific process of the heat treatment is as follows: the bar blank is first held at a temperature of 5°C to 20°C below the β phase transformation point for 30 min to 90 min and then air-cooled, and then held at a temperature of 500°C to 600°C for 4 h to 8 h and then air-cooled.

[0010] Preferably, the starting forging temperature for each heating time of the forming forging in Step 3 is 10°C to 30°C above the β phase transformation point.

[0011] Preferably, the specific process of the heat treatment in Step 4 is as follows: the bar blank is first held at a temperature of 10°C below the β phase transformation point for 60 min and then air-cooled, and then held at a temperature of 550°C for 6 h and then air-cooled.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0013] In the method for open-die forging of the TC4-DT titanium alloy of the present invention, first, the starting forging temperature of the forming forging is controlled within the range of 5 to 50°C above the β phase transformation point, and the final forging temperature is controlled within the range of 50 to 80°C below the β phase transformation point. Subsequently, solution treatment within the range of 5 to 20°C below the β phase transformation point and aging treatment within the temperature range of 500 to 600°C are carried out on the bar blank. Through the above forging process, the present invention can retain the Widmanstätten structure forged above a certain β phase transformation point. Combining the solution aging treatment below the β phase transformation point can coarsen the lamellar α inside the β grains and have a certain basket-weave structure. This structure can obtain good plasticity while ensuring high strength and high fracture toughness, and has better comprehensive performance than the Widmanstätten structure obtained by the traditional process, further improving the plasticity of the alloy while ensuring the strength and toughness of the alloy. Specific Embodiments

[0014] To implement the cogging forging method of TC4-DT titanium alloy described in the present invention, equipment such as a forging press, a high-temperature electric furnace, and an manipulator is required. The specific implementation manners of this method are as follows:

[0015] Step 1: Use a 2000-ton quick forging machine to perform cogging forging on a TC4-DT titanium alloy ingot with a specification of Ф320mm, and obtain a first forging blank after air cooling; the cogging forging adopts a forging method of repeated upsetting and drawing, and is completed in one heat treatment. The starting forging temperature of the cogging forging is 165°C above the β phase transformation point, the final forging temperature of the cogging forging is 70°C below the β phase transformation point, and the cumulative deformation amount of the cogging forging is 70%; the first forging blank obtained by processing is a round blank with a cross-sectional diameter of 175mm;

[0016] Step 2: Use a 2000-ton quick forging machine to perform intermediate forging on the first forging blank described in Step 1, and obtain a second forging blank after air cooling; the intermediate forging adopts a forging method of repeated upsetting and drawing, and is completed in two heat treatments. The starting forging temperature of each heat treatment of the intermediate forging is 75°C above the β phase transformation point, the final forging temperature of each heat treatment of the intermediate forging is 70°C below the β phase transformation point, and the cumulative deformation amount of the intermediate forging is 50%; the second forging blank obtained by processing in this embodiment is a square blank with a cross-sectional side length of 110mm;

[0017] Step 3: Use a 2000-ton quick forging machine to perform shaping forging on the second forging blank described in Step 2 to obtain a bar blank; the shaping forging adopts a forging method of repeated upsetting and drawing, and is completed in one heat treatment. The starting forging temperature of the shaping forging is 10°C above the β phase transformation point, the final forging temperature of the shaping forging is 80°C below the β phase transformation point, and the cumulative deformation amount of the shaping forging is 65%; the third forging blank obtained by processing in this embodiment is a square blank with a cross-sectional side length of 65mm;

[0018] Step 4: Heat-treat the bar blank described in Step 3 to obtain TC4-DT titanium alloy bars; the specific process of the heat treatment is: first keep the bar blank at a temperature of 10°C below the β phase transformation point for 40 minutes and then air cool it, and then keep it at a temperature of 550°C for 6 hours and then air cool it.

Claims

1. A blooming forging method for TC4-DT titanium alloy, characterized in that, The steps are as follows: Step 1: Perform cogging forging on a TC4-DT titanium alloy ingot to obtain a first forging blank; the cogging forging adopts a forging method of repeated upsetting and drawing, and is completed in 1 to 3 heating passes. The starting forging temperature for each heating pass of cogging forging is 100°C to 200°C above the β transformation point, and the final forging temperature for each heating pass of cogging forging is 50°C to 100°C below the β transformation point. The cumulative deformation amount of the cogging forging is 60% to 80%; Step 2: Perform intermediate forging on the first forging blank in Step 1 to obtain a second forging blank; the intermediate forging adopts a forging method of repeated upsetting and drawing, and is completed in 2 to 3 heating passes. The starting forging temperature for each heating pass of intermediate forging is 50°C to 100°C above the β transformation point, and the final forging temperature for each heating pass of intermediate forging is 50°C to 100°C below the β transformation point. The cumulative deformation amount of the intermediate forging is 50% to 70%; Step 3: Perform shaping forging on the second forging blank in Step 2 to obtain a bar blank; the shaping forging adopts a forging method of repeated upsetting and drawing, and is completed in 1 to 2 heating passes. The starting forging temperature for each heating pass of shaping forging is 5°C to 50°C above the β transformation point, and the final forging temperature for each heating pass of shaping forging is 50°C to 80°C below the β transformation point. The cumulative deformation amount of the shaping forging is 60% to 75%; Step 4: Heat-treat the bar blank in Step 3 to obtain a TC4-DT titanium alloy bar; the specific process of the heat treatment is: first, keep the bar blank at a temperature of 5°C to 20°C below the β transformation point for 30 min to 90 min and then air-cool, and then keep it at a temperature of 500°C to 600°C for 4 h to 8 h and then air-cool.

2. The cogging forging method of TC4-DT titanium alloy according to claim 1, characterized in that, The starting forging temperature for each heating pass of the shaping forging in Step 3 is 10°C to 30°C above the β transformation point.

3. The cogging forging method of TC4-DT titanium alloy according to claim 1, characterized in that The specific process of the heat treatment in Step 4 is: first, keep the bar blank at a temperature of 10°C below the β transformation point for 60 min and then air-cool, and then keep it at a temperature of 550°C for 6 h and then air-cool.