CN114836702B - Heat treatment process for improving performance stability of TC25G alloy forging with thick section or variable section - Google Patents

Abstract

The invention discloses a heat treatment process for improving the performance stability of thick-section or variable-section TC25G alloy forgings. Heat the forging to 870-890°C, heat it through, keep it warm for 8-16 hours, and then take it out of the furnace and air cool it. Finally, heat the forging to 530-570° C. When the maximum thickness of the forging does not exceed 180mm, the difference between the maximum and minimum tensile strength at any position at room temperature does not exceed 80MPa; when the maximum thickness of the forging does not exceed 90mm, the difference between the maximum and minimum tensile strength at any position does not exceed 50MPa.

Description

A Heat Treatment Process for Improving the Performance Stability of Thick Section or Variable Section TC25G Alloy Forgings

technical field

The invention belongs to the technical field of titanium alloys, and in particular relates to a heat treatment process for improving the performance stability of thick-section or variable-section TC25G alloy forgings.

Background technique

Titanium alloy has the characteristics of low density, high strength and corrosion resistance, and is widely used in the fields of aviation, aerospace, navigation and chemical industry. Large-scale titanium alloy structural parts require materials to have good uniformity in structure and mechanical properties, so the requirements for material selection and material processing technology are relatively high.

TC25G alloy is an α+β state alloy developed on the basis of Russian BT25 alloy by adding Mo and Zr elements. This alloy has the characteristics of high temperature resistance, high strength and high toughness. A high-pressure compressor blisk applied to an aero-engine. However, due to the problem of hardenability, when the TC25G alloy forging is a thick section forging or a variable section forging, during the quenching process, due to the difference in the surface cooling rate and the center cooling rate, there are differences in the structure of the surface and center of the forging, resulting in different positions of the forging. performance. Therefore, it is necessary to design a new heat treatment system to ensure the balance of mechanical properties of forgings at different positions and improve the reliability and life of forgings.

Contents of the invention

In order to solve the problems of increased performance difference in different parts of large-scale forgings of thick or variable cross-section TC25G alloys, low strength at the center of the forgings, etc., the present invention is designed in combination with the characteristics of TC25G alloy composition, phase transformation and grain growth law of α-phase lath , provides a heat treatment process to improve the performance stability of thick section or variable section TC25G alloy forgings, the specific technical scheme is as follows:

A heat treatment process for improving the performance stability of thick section or variable section TC25G forgings, comprising the following steps:

Step 1) TC25G alloy forgings are subjected to solution treatment at 15-25°C below the β transformation temperature, and oil-cooled after being released from the furnace;

Step 2) Then heat the forging at 870-910° C. and keep it warm for 2-5 hours, then air-cool it;

Step 3) Finally, the forging is heated thoroughly at 530-630° C., then kept warm for 6-8 hours, and then air-cooled.

The heat treatment process for improving the performance stability of thick section or variable section TC25G forgings is characterized in that: the TC25G alloy forgings are hot-worked forgings in the two-phase zone, and the maximum thickness of the forgings does not exceed 180mm.

The heat treatment process for improving the performance stability of a thick-section or variable-section TC25G alloy forging, the preferred solution is that the TC25G alloy forging is a two-phase hot-worked forging, and when the maximum thickness of the forging does not exceed 180mm, any position of the forging The difference between the maximum and minimum tensile strength at room temperature shall not exceed 80MPa; when the maximum thickness of the forging does not exceed 90mm, the difference between the maximum and minimum tensile strength at room temperature at any position of the forging shall not exceed 50MPa.

The heat treatment process for improving the performance stability of thick section or variable section TC25G alloy forgings, the preferred solution is that the composition of the TC25G alloy forgings is: Al: 6.0-7.0; Mo: 3.5-4.5; Zr: 3.0-4.5 ; Sn: 1.0-2.5; W: 0.4-1.5; Si: 0.1-0.3, and the rest are Ti and unavoidable impurity elements.

Beneficial effects of the present invention:

The invention helps to reduce the structure difference at different positions of large-size thick-section or variable-section TC25G titanium alloy forgings. When the thickness of the forging does not exceed 180mm, the room temperature tensile strength difference at any position of the forging does not exceed 80MPa, which is the same as that under the traditional heat treatment process. Compared with forgings, the performance stability and consistency of forgings have been significantly improved; when the maximum thickness of forgings does not exceed 90mm, the difference between the maximum and minimum tensile strength at room temperature at any position of the forgings does not exceed 50MPa. The present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments.

Description of drawings

Fig. 1 is a schematic cross-sectional view of a forging in Example 1 of the present invention;

Fig. 2 is the photo of surface microstructure after heat treatment of the forging of Example 1 of the present invention;

Fig. 3 is the photo of central microstructure after heat treatment of the forging of Example 1 of the present invention;

Fig. 4 is a schematic cross-sectional view of a forging in Example 2 of the present invention;

Fig. 5 is the photo of surface microstructure after heat treatment of the forging of Example 2 of the present invention;

Fig. 6 is the central microstructure photo of the forging of Example 2 of the present invention after heat treatment;

Figure 7 is a schematic cross-sectional view of a forging in Example 3 of the present invention;

Figure 8 is a photo of the microstructure of the center of the hub after heat treatment of the forging in Example 2 of the present invention;

Fig. 9 is a photo of the microstructure of the center of the web plate after heat treatment of the forging in Example 2 of the present invention;

Fig. 10 is a photograph of the microstructure of the center of the rim of the forging in Example 2 of the present invention after heat treatment.

Detailed ways

Example 1:

The material used in this embodiment is a TC25G alloy disc forging with a diameter of 900 mm and a thickness of 180 mm. Its composition is Ti-6.37Al-1.80Zr-4.12Mo-0.24Si-0.78W, and the rest are Ti and unavoidable impurity elements. The metallographic method detects that the alloy phase transition point is 985°C;

1) First, heat the TC25G alloy forging to 965°C for 2 hours and then take it out of the furnace for oil cooling;

2) Insulate the forging obtained in step 1) at 890° C. for 4 hours, and then take it out of the furnace and air-cool it;

3) Finally, the forging obtained in step 2) was kept at 540° C. for 6 hours, and then it was taken out of the furnace and air-cooled.

The microstructure analysis results of the forging after heat treatment show that the microstructure of the forging is a two-state structure, the primary α content is about 20%, and the rest is β transformation structure. There is no obvious difference in the microstructure between the surface and center of the forging. The room temperature tensile performance test was carried out on the forging, and the test results were compared with the forgings under the traditional heat treatment process. The results are shown in Table 1. The highest strength value is 1148 MPa on the surface of the forging, and the lowest strength value is 1098 MPa on the center of the forging. The difference between the highest value and the lowest value is 50MPa. The room temperature tensile strength difference of the forging under the traditional heat treatment process exceeds 100MPa, so it can be seen that the new heat treatment process can significantly reduce the room temperature tensile strength difference at different positions of the forging, and improve the consistency of structure and performance.

Table 1 Example 1 forging room temperature tensile properties

Example 2:

The material used in this embodiment is a disc forging with a diameter of 850 mm and a thickness of 90 mm. The alloy composition is Ti-6.39Al-1.80Zr-3.98Mo-0.19Si-0.81W, and the rest are unavoidable impurity elements. The metallographic method detects that the alloy phase transition point is 983°C;

1) First, heat the TC25G alloy forging to 960°C for 2 hours and then take it out of the furnace for oil cooling;

2) heat the forging obtained in step 1) at 890°C for 4 hours, and then take it out of the furnace and air cool;

3) Finally, the forging obtained in step 2) was kept at 540° C. for 6 hours, and then it was taken out of the furnace and air-cooled.

The microstructure of the forging after heat treatment is a typical two-state microstructure, the primary α content is about 20%, and the rest is β transformation microstructure. The surface and center structures of the forgings are similar, and there is no obvious difference. The test results of tensile properties at room temperature (Table 2) show that the highest value of the forging strength is 1151MPa, and the lowest value is 1118MPa, with a difference of 33MPa, while the difference in room temperature tensile properties of the comparative forgings after heat treatment by the traditional process is 100MPa. It can be seen that the new heat treatment process can Significantly improve the overall performance stability of forgings.

Table 2 Example 2 Forgings Tensile Properties at Room Temperature

Example 3:

The material used in this embodiment is a TC25G alloy disc forging with a diameter of 950 mm, which has a different thickness at different positions; the thickness at different positions is as follows: the hub is 70 mm, the web is 40 mm, and the rim is 110 mm; the composition of the TC25G alloy disc forging is Ti-6.42Al-1.83Zr-4.06Mo-0.21Si-0.79W, the rest are Ti and unavoidable impurity elements, and the metallographic method detects that the alloy phase transition point is 988°C;

1) First, heat the TC25G alloy forging to 968°C for 2 hours and then take it out of the furnace for oil cooling;

2) heat the forging obtained in step 1) at 895°C for 4 hours, and then take it out of the furnace and air cool;

3) Finally, the forging obtained in step 2) was kept at 540° C. for 6 hours, and then it was taken out of the furnace and air-cooled.

The microstructure after heat treatment of the forging is a two-state microstructure, the primary α content is about 20%, and the rest is β transformation microstructure. The structure of the forged hub, spoke plate and rim is similar, and the structure consistency is high. The room temperature tensile performance test results (Table 3) show that the highest value of the forging strength is 1151MPa, the lowest value is 1102MPa, a difference of 43MPa, and the performance difference of the forging under the traditional process is 87MPa, which shows that the performance consistency of the whole forging of the embodiment is far Higher than forgings under traditional heat treatment process.

Table 3 Example 3 Forgings Tensile Properties at Room Temperature

The above-mentioned embodiments are only to illustrate the technical concept and characteristics of the present invention, and the purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and not to limit the protection scope of the present invention. All equivalent changes or modifications made according to the spirit of the present invention shall fall within the protection scope of the present invention.

Claims (3)

1. A heat treatment process for improving performance stability of a TC25G alloy forging with a thick section or a variable section is characterized by comprising the following steps:

step 1), carrying out solution treatment on a TC25G alloy forging at a temperature of 15-25 ℃ below the beta transformation temperature, and cooling oil after discharging;

step 2), the forging is subjected to heat penetration at 870-910 ℃ and then heat preservation for 2-5 hours for air cooling;

and 3) finally, preserving heat for 6-8 hours after the forge piece is heated to 530-630 ℃ for air cooling.

2. The heat treatment process for improving the performance stability of a thick-section or variable-section TC25G alloy forging according to claim 1, wherein the heat treatment process comprises the following steps of: the TC25G alloy forging is a two-phase region hot-working forging, and when the maximum thickness of the forging is not more than 180mm, the difference between the maximum value and the minimum value of the room-temperature tensile strength of any position of the forging is not more than 80MPa; when the maximum thickness of the forging piece is not more than 90 mm; the maximum and minimum values of tensile strength of the forge piece at room temperature are not more than 50MPa.

3. The heat treatment process for improving the performance stability of a thick-section or variable-section TC25G alloy forging according to claim 1, wherein the heat treatment process comprises the following steps of: the TC25G alloy forging comprises the following components: al:6.0 to 7.0; mo:3.5 to 4.5; zr:3.0 to 4.5; sn:1.0 to 2.5; w:0.4 to 1.5; si:0.1 to 0.3, and the balance of Ti and unavoidable impurity elements.

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