A forging and heat treatment process for TiB-reinforced Ti175 alloy ring

Abstract

A forging and heat treatment process for a TiB-reinforced Ti175 alloy ring comprises the following steps: Step 1: Heating a TiB-reinforced Ti175 ingot to a temperature 10°C to 150°C above the β transformation point, followed by forging and roll forming; Step 2: After the ring is formed, solution treatment is performed at a temperature 10°C to 50°C above the β transformation point; Step 3: Aging and surface oxygenation treatment are performed on the solution-treated ring at a temperature between 500°C and 600°C. In the present invention, an oxygen-infiltrated layer is formed on the surface of the TiB / Ti65 alloy ring after surface oxygenation treatment, thereby improving both the room temperature and high-temperature fatigue properties of the alloy.

Description

Technical Field

[0001] The invention belongs to the field of titanium and titanium alloy processing, and particularly relates to a forging and heat treatment process of a TiB reinforced Ti175 alloy ring. Background Art

[0002] Ti175 alloy is a high-temperature titanium alloy independently improved by the Institute of Metal Research, Chinese Academy of Sciences, which can be used for a long time at 550°C. Compared with other alloys, this alloy has obvious comprehensive advantages. For example, compared with TA15, the alloy has obvious advantages in all aspects of performance; compared with TC4 and TC11 alloys, the mechanical properties in the high temperature range are better than TC4 and TC11 alloys, and its performance advantages become more obvious as the temperature increases. However, with the rapid development of the aerospace field, Ti175 alloy has gradually become unable to meet the higher requirements for component performance. Therefore, a small amount of TiB is added to it to improve the material strength. Although the introduction of TiB can greatly improve the strength of the material, it can also easily act as a fatigue crack source and cause fatigue fracture of the material. At the same time, it also leads to the weakening of the processability of TiB-enhanced Ti175 alloy, making it prone to cracking during deformation. Therefore, the traditional Ti175 alloy hot working process is no longer applicable. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to address the shortcomings of the above-mentioned existing technologies and provide a forging and heat treatment process for TiB-reinforced Ti175 alloy rings. The rings produced by this process have good batch stability and high strength and fatigue performance. The specific process steps are as follows:

[0004] A forging and heat treatment process for a TiB-reinforced Ti175 alloy ring comprises the following steps: heating a TiB-reinforced Ti175 ingot to a temperature 10° C. to 150° C. above a β-transformation point, forging, and rolling the ingot;

[0005] Step 2: After the ring is formed, solution treatment is performed at 10℃ to 50℃ above the β phase transformation point;

[0006] Step 3: The ring after solution treatment is aged and surface oxygenated at 500℃~600℃.

[0007] The forging and heat treatment process of the TiB-reinforced Ti175 alloy ring is preferably as follows: in step 1, the forging and rolling process of the TiB-reinforced Ti175 ingot is as follows: first, the alloy ingot is subjected to 2 to 6 fires of upsetting deformation at 10°C to 150°C above the β transformation point, with the total forging ratio of each fire being not less than 3 and the final forging temperature being not less than 900°C, to obtain a TiB-reinforced Ti175 alloy billet;

[0008] The TiB reinforced Ti175 alloy billet is heated to 10°C to 150°C above the β phase transformation point, punched after upsetting, and the inner diameter of the ring billet is 25% to 40% of its outer diameter; then the hole is expanded using a horse frame to 50% to 70% of its outer diameter; finally, a ring rolling machine is used for rolling, and the inner diameter of the ring after rolling is 60% to 80% of its outer diameter.

[0009] The preferred embodiment of the forging and heat treatment process of the TiB-reinforced Ti175 alloy ring is as follows: in step 1, the size of the original β grains in the microstructure of the TiB-reinforced Ti175 alloy ring after forging and rolling is no more than 500 μm.

[0010] The forging and heat treatment process of the TiB-reinforced Ti175 alloy ring is preferably as follows: the heat treatment process of the TiB-reinforced Ti175 alloy ring is as follows: after the ring is formed, it is subjected to a solid solution heat treatment in the β phase region, the solid solution temperature is 10°C to 50°C above the β phase transformation point, and is kept warm for 1h to 4h before air cooling or wind cooling; the ring is then subjected to an aging heat treatment at 500°C to 600°C, kept warm for 4h to 12h, and air cooling; finally, the TiB-reinforced Ti175 alloy ring is placed in an oxygen atmosphere at 0.2 to 1.5 times the standard atmospheric pressure or a mixed atmosphere with an oxygen concentration equivalent thereto, heated to 500 to 600°C and not higher than the aging temperature, kept warm for 50h to 150h, and air cooling.

[0011] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0012] 1) By adopting the forging forming method of the present invention, the forging forming process of the TiB reinforced Ti175 alloy ring is completed in the β phase region, which has good forming ability and greatly simplifies the hot working process;

[0013] 2) The matrix microstructure of the TiB-reinforced Ti175 alloy ring prepared by the present invention is a basketweave structure, which has high room temperature and high temperature strength;

[0014] 3) In the present invention, an oxygen permeation layer is formed on the surface of the TiB / Ti65 alloy ring after surface oxygen permeation treatment, which can simultaneously improve the room temperature and high temperature fatigue properties of the alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a microstructure photograph of the TiB reinforced Ti175 alloy ring prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0016] Example 1:

[0017] like Figure 1As shown, a TiB-reinforced Ti175 alloy ingot with a diameter of 480 mm was used, and the alloy composition by mass percentage was Ti-6.3Al-2.1Sn-3.2Zr-3.5Mo--0.3Si-0.9W-0.5B. The β-transus temperature of the alloy ingot detected by metallographic method was 1000℃.

[0018] The TiB reinforced Ti175 alloy ingot was heated to 1100℃, kept warm for 16 hours and then taken out of the furnace. It was subjected to two upsetting and drawing deformations on a hydraulic press, with the upsetting and drawing forging ratios of both being 3. It was air-cooled after forging to complete the blanking of the TiB reinforced Ti175 alloy ingot. The billet was heated to 1050℃, kept warm for 6 hours and then subjected to one upsetting and drawing deformation, with the upsetting and drawing forging ratios of both being 2. It was air-cooled after forging. The billet was then heated to 1050℃ and subjected to one upsetting and drawing deformation, with the upsetting forging ratio being 2 and the drawing forging ratio being 1.5. It was air-cooled after forging.

[0019] The forging blank is heated to 1050°C, held at that temperature for 6 hours, and then punched on a hydraulic press. After shaping, the blank is returned to the furnace for holding, then expanded and shaped using a rack to produce a pre-rolled blank. Finally, the pre-rolled blank is heated to 1050°C and formed on a ring rolling mill to produce a Ø610×Ø520×200mm ring blank. After shaping, the ring undergoes heat treatment at 1030°C / 2h / AC followed by 560°C / 6h / AC. After heat treatment, the ring is placed in an oxygen atmosphere at 1.2 times standard atmospheric pressure, held at 610°C for 100h, and then subjected to surface oxygen permeation treatment. After grinding and polishing, the resulting TiB-reinforced Ti175 alloy ring measures Ø600×Ø530×200mm.

[0020] Table 1 Tensile properties of TiB reinforced Ti175 alloy in Example 1

[0021]

[0022] Table 2 Fatigue properties of TiB reinforced Ti175 alloy in Example 1

[0023]

[0024] As can be seen from the above examples, the TiB-reinforced Ti175 alloy rings prepared by the present invention not only have high room temperature and high temperature strength, with room temperature strength exceeding 1200 MPa and high temperature strength of 900 MPa at 550°C, but also maintain high fatigue resistance, with room temperature fatigue limits exceeding 630 MPa and high temperature fatigue limits exceeding 550 MPa at 550°C.

Claims

1. A forging and heat treatment process for a TiB-reinforced Ti175 alloy ring, characterized in that: Step 1: heating the TiB reinforced Ti175 ingot to 10°C to 150°C above the β transformation point for forging and rolling; Step 2: After the ring is formed, solution treatment is performed at 10℃ to 50℃ above the β phase transformation point; Step 3: subjecting the ring after solution treatment to aging and surface oxygen permeation treatment at a temperature between 500°C and 600°C; In step 1, the enhanced forging and rolling forming process of the TiB-reinforced Ti175 ingot is as follows: first, the alloy ingot is subjected to 2-6 fires of upsetting deformation at 10°C to 150°C above the β transformation point, with the total forging ratio of each fire being not less than 3 and the final forging temperature being not less than 900°C, to obtain a TiB-reinforced Ti175 alloy billet; The TiB reinforced Ti175 alloy billet is heated to 10°C to 150°C above the β phase transformation point, punched after upsetting, and the inner diameter of the ring billet is 25% to 40% of its outer diameter; then the hole is expanded using a horse frame to 50% to 70% of its outer diameter; finally, a ring rolling machine is used for rolling, and the inner diameter of the ring after rolling is 60% to 80% of its outer diameter.

2. The forging and heat treatment process for a TiB-reinforced Ti175 alloy ring according to claim 1, characterized in that: In step 1, the size of the original β grains in the microstructure of the TiB reinforced Ti175 alloy ring after forging and rolling is no more than 500 μm.

3. The forging and heat treatment process for a TiB-reinforced Ti175 alloy ring according to claim 1, characterized in that: The heat treatment process of the TiB-reinforced Ti175 alloy ring is as follows: after the ring is shaped, it is subjected to a solid solution heat treatment in the β phase region, the solid solution temperature is 10°C to 50°C above the β phase transformation point, and the ring is kept warm for 1h to 4h before air cooling or wind cooling; then the ring is subjected to an aging heat treatment at 500°C to 600°C, kept warm for 4h to 12h, and air cooling; finally, the TiB-reinforced Ti175 alloy ring is placed in an oxygen atmosphere at 0.2 to 1.5 times the standard atmospheric pressure or a mixed atmosphere with an oxygen concentration equivalent thereto, heated to 500 to 600°C and not higher than the aging temperature, kept warm for 50h to 150h, and air cooling.

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