Preparation method of TA11 alloy bar with high creep resistance

Abstract

The invention discloses a preparation method of a TA11 alloy bar with high creep resistance. The preparation method comprises the following steps: S1, ingot casting preparation: performing VAR smelting on an alloy for three times to obtain a TA11 alloy ingot with components meeting requirements; s2, intermediate billet forging is conducted, specifically, the qualified cast ingot obtained in the S1 is subjected to two-heating-number forging at the temperature higher than the beta phase transformation point temperature, and an intermediate billet is obtained; s3, multi-heating-number circulating forging is conducted, specifically, the TA11 alloy intermediate blank obtained in the S2 is subjected to five-heating-number forging deformation within the range above and below the beta phase transformation point temperature, and an intermediate precision forging blank which is uniform in structure and high in alpha phase content is obtained; and S4, finish forging machining of a finished product bar is conducted, specifically, finish forging machining is conducted on the TA11 alloy intermediate finish forging blank obtained in the S3 at the temperature below the phase transformation point temperature, and the TA11 alloy bar with the high creep resistance is obtained. The TA11 alloy bar prepared through the method is high in alpha-phase content and stable in control, the structure is uniform and consistent, and the high-temperature creep resistance is stably controlled to be smaller than or equal to 0.15%.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal material processing technology, specifically relating to a method for preparing TA11 alloy bars with high creep resistance. Background Technology

[0002] TA11 alloy, nominally composed of Ti8Al-1Mo-1V, is a near-alpha type titanium alloy with excellent high-temperature strength, oxidation resistance, and creep resistance. It is widely used in compressor blades and rotating components and can operate continuously at 400℃. In practical applications, blades must withstand high temperatures, high pressures, and complex stresses for extended periods, placing stringent demands on the material's microstructure stability and creep resistance. Standards require TA11 alloy bars to have a residual deformation (creep resistance) ≤0.2% after 100 hours at 425℃ and 410MPa stress. Existing TA11 alloy bars are produced using conventional melting and forging processes, which suffer from unstable microstructure control and large fluctuations in alpha phase content, resulting in poor creep resistance stability and instances where creep resistance exceeds standard requirements. This makes it difficult to meet the stability control requirements for TA11 alloy bars used in high-end blades. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing TA11 alloy rods with high creep resistance. The TA11 alloy rods prepared by this method have a high and stable α phase content, uniform microstructure, and stable high-temperature creep resistance controlled at ≤0.15%.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A method for preparing a TA11 alloy rod with high creep resistance, wherein the composition of the TA11 alloy rod is as follows: Al content is 7.70%–8.20%, Mo, V content is 0.90%–1.10%, O content is 0.07%–0.12%, and the balance is Ti and other impurity elements. The preparation method includes the following steps:

[0006] S1, Ingot preparation:

[0007] The alloy underwent three VAR melting processes to obtain TA11 alloy ingots with the required composition.

[0008] S2, intermediate billet forging:

[0009] The qualified ingot obtained from S1 is forged twice at a temperature above the β phase transformation point to obtain an intermediate billet.

[0010] S3, Multi-fire secondary cycle forging:

[0011] The TA11 alloy intermediate billet obtained from S2 was forged and deformed in five passes within the range of the β phase transformation temperature to obtain an intermediate precision forged billet with uniform microstructure and high α phase content.

[0012] S4, Finished bar stock precision forging:

[0013] The TA11 alloy intermediate precision forging billet obtained from S3 is precision forged below the phase transformation temperature to obtain TA11 alloy bars with high creep resistance.

[0014] Preferably, in step S2, the first forging is performed by heating to 100°C to 200°C above the β phase transformation point and holding for 360 to 600 minutes; the second forging is performed by heating to 50°C to 100°C above the β phase transformation point and holding for 60 to 240 minutes, followed by air cooling.

[0015] Preferably, in S2, the rough forging ratio per forging pass is controlled at 1.5 to 1.9, the elongation deformation is controlled at 30% to 50%, and the final forging temperature is not lower than 800°C.

[0016] Preferably, in step S3, the first heating is performed at 20°C to 50°C below the phase transformation point temperature, held for 180 min to 420 min, and then drawn. The furnace is then returned to the furnace at 20°C to 70°C above the phase transformation point temperature, held for 120 min to 300 min, and then forged. After forging, the furnace is air-cooled.

[0017] Preferably, in S3, the first upsetting ratio is controlled at 1.4 to 1.9, the elongation deformation is controlled at 30% to 50%, and the final forging temperature is not lower than 700°C.

[0018] Preferably, in step S3, the second to fifth firings are performed by heating to 20°C to 60°C below the phase transformation temperature, holding the temperature for 120 to 360 minutes, and then air-cooling the product.

[0019] Preferably, in S3, the upsetting ratio is controlled at 1.2 to 1.8 in the second to fifth forging passes, the elongation deformation is controlled at 20% to 50%, and the final forging temperature is not lower than 700℃.

[0020] Preferably, in step S4, the intermediate precision forging billet is heated to 50°C to 80°C below the phase transformation point temperature, held at that temperature for 60 to 180 minutes, and then precision forged, followed by air cooling.

[0021] Preferably, in S4, the deformation amount per forging pass is 10-25%, the cumulative deformation amount per forging pass is 50%-80%, and the final forging temperature is not lower than 700℃.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. By precisely controlling the Al content within the upper limit of the standard, the proportion of α phase in the alloy bar can be increased and its stability improved; precise control of O content can improve strength through interstitial strengthening while avoiding abnormal reduction in plasticity, thus achieving a balance between strength and plasticity.

[0024] 2. By employing multi-cycle forging deformation around the phase transformation point temperature, a refined and uniform intermediate precision forging billet is prepared. After precision forging of the finished product, the microstructure is further refined and optimized by controlling the heating temperature, deformation per pass, and processing temperature. Finally, bar stock with a specification of 25mm≤Φ≤60mm has an α phase content of >70% and a creep resistance value of ≤0.15% under 425℃ and 410MPa stress conditions for 100h, meeting the requirements for high-end aero-engine blades.

[0025] 3. Compared with traditional preparation methods, the method of the present invention requires fewer forging passes for the intermediate billet, has a shorter production cycle, uses precision forging for finished product processing, has a high degree of automation, and ensures stable production. Attached Figure Description

[0026] Figure 1 This is a flowchart of the method of the present invention.

[0027] Figure 2 This is the microstructure of a 60mm TA11 alloy bar prepared by the method of this invention.

[0028] Figure 3 This is the microstructure of a 40mm TA11 alloy bar prepared by the method of this invention.

[0029] Figure 4 This is the microstructure of a 30mm TA11 alloy bar prepared by the method of this invention.

[0030] Figure 5 This is the microstructure of a 25mm TA11 alloy bar prepared by the method of this invention. Detailed Implementation

[0031] To make the purpose of the invention clearer, the invention will be described clearly and completely below with reference to the accompanying drawings and embodiments.

[0032] The composition range of a TA11 alloy bar with high creep resistance is as follows: Al content is 7.70% to 8.20%, Mo, V content is 0.90% to 1.10%, O content is 0.07% to 0.12%, and the balance is Ti and other impurity elements.

[0033] like Figure 1The method for preparing a TA11 alloy bar with high creep resistance involves first obtaining a TA11 alloy ingot that meets the Al, Mo, V, and O content requirements through three VAR melting processes, then performing two-stage forging and multi-stage cyclic forging to obtain an intermediate precision forging billet with the target microstructure and phase content, followed by precision forging deformation to obtain a TA11 alloy finished bar with uniform microstructure, high α phase content, and high creep resistance.

[0034] The preparation method specifically includes the following steps:

[0035] S1, Ingot preparation:

[0036] The alloy was smelted three times by VAR to obtain Φ640mm TA11 alloy ingots with the required composition. The content of the main chemical element Al was controlled at 7.70% to 8.20%, V and Mo were controlled at 0.90% to 1.10% according to the standard, O was controlled at 0.07% to 0.12%, and the balance was Ti and other impurity elements.

[0037] S2, intermediate billet forging:

[0038] The qualified ingot obtained from S1 is subjected to two forging processes to obtain an intermediate billet. The first forging process involves heating to 100℃–200℃ above the β-phase transformation point and holding for 360–600 min. The second forging process involves heating to 50℃–100℃ above the β-phase transformation point and holding for 60–240 min, followed by air cooling. The roughing ratio for each forging process is controlled at 1.5–1.9, the elongation deformation is controlled at 30%–50%, and the final forging temperature is not lower than 800℃. After two forging processes, an intermediate billet with a fully fragmented and refined as-cast microstructure is obtained.

[0039] S3, Multi-fire secondary cycle forging:

[0040] The TA11 alloy intermediate billet obtained from S2 was forged in five passes within the range above and below the β phase transformation temperature to obtain an intermediate precision forged billet with uniform microstructure and high α phase content. The first pass was heated to 20℃~50℃ below the phase transformation temperature and held for 180min~420min for upsetting and drawing. Then it was returned to the furnace to 20℃~70℃ above the phase transformation temperature and held for 120min~300min for forging. The upsetting-to-roughing ratio was controlled at 1.4~1.9, the drawing deformation was controlled at 30%~50%, and the final forging temperature was not lower than 700℃. After forging, it was air-cooled. From the second to the fifth forging, the cold material is heated to 20°C to 60°C below the phase transformation temperature and held for 120 to 360 minutes before forging. The upsetting ratio is controlled at 1.2 to 1.8, the elongation deformation is controlled at 20% to 50%, and the final forging temperature is not lower than 700°C. After forging, the material is air-cooled to obtain a uniform, near-equiaxed TA11 alloy intermediate precision forging billet.

[0041] S4, Finished bar stock precision forging:

[0042] The TA11 alloy intermediate precision forging billet obtained from S3 is heated to 50℃~80℃ below the phase transformation temperature and held for 60min~180min. After precision forging, it is peeled and polished to obtain TA11 alloy bars with uniform microstructure and high α phase content, conforming to specifications of 25mm≤Φ≤60mm and high creep resistance for blades. The deformation per precision forging pass is 10~25%, the cumulative deformation per single forging pass is 50%~80%, the final forging temperature is not lower than 700℃, and it is air-cooled after forging. The primary α phase content of the finished precision forged bar is >70%.

[0043] The present invention will be further described in detail below with reference to specific embodiments.

[0044] Example 1

[0045] A method for preparing 60mm TA11 alloy bars with high creep resistance, the specific steps of which are as follows:

[0046] S1, Ingot Preparation. A Φ640mm ingot was obtained by three VAR melting processes, with an Al content of 7.90%–8.20%, a Mo content of 0.90%–1.10%, a V content of 0.90%–1.10%, an O content of 0.07%–0.12%, and a β phase transformation temperature of 1040℃–1045℃.

[0047] S2, Initial Forging. Selected qualified TA11 ingots are forged in two passes above the phase transformation point. First, the ingot is heated to 200°C above the phase transformation point and held for 360 minutes for the first forging pass (upsetting and drawing). The second forging pass involves heating to 100°C above the phase transformation point and holding for 60 minutes, followed by air cooling. The rough forging ratio for each pass is controlled at 1.9, the drawing deformation is controlled at 50%, and the final forging temperature is not lower than 800°C. After two passes, a fully fragmented and refined intermediate billet is obtained.

[0048] S3, multi-stage cyclic forging. The intermediate billet is forged five times within the range of the β phase transformation temperature to refine the microstructure. In the first stage, the billet is heated to 50°C below the phase transformation temperature, held for 180 min, and then upsetting and drawing. It is then returned to the furnace to 20°C above the phase transformation temperature, held for 300 min, and forged again. The upsetting-to-forging ratio is controlled at 1.4, the elongation deformation is controlled at 30%, and the final forging temperature is not lower than 700°C. In the second to fifth stages, the billet is heated to 20°C below the phase transformation temperature, held for 120 min, and forged again. The upsetting-to-forging ratio is controlled at 1.8, the elongation deformation is controlled at 50%, and the final forging temperature is not lower than 700°C. After forging, the billet is air-cooled.

[0049] S4, Finished bar forging. The intermediate forged billet obtained through multi-stage forging is heated to 50°C below the phase transformation temperature and held for 180 minutes. This process yields a Φ62mm bar, which, after peeling and polishing, becomes a Φ60mm finished bar (the Φ60mm specification conforms to the "25mm≤Φ≤60mm" finished size range in the technical solution). The deformation per forging pass is 10-25%, the cumulative deformation per single forging pass is 60%, the final forging temperature is not lower than 700°C, and the bar is air-cooled after forging.

[0050] Example 2

[0051] A method for preparing 40mm TA11 alloy bars with high creep resistance, the specific steps of which are as follows:

[0052] S1, Ingot preparation. A Φ640mm ingot was obtained by three VAR melting processes, with an Al content of 7.90%–8.20%, a Mo content of 0.90%–1.10%, a V content of 0.90%–1.10%, an O content of 0.07%–0.12%, and a β phase transformation temperature of 1040℃–1045℃.

[0053] S2, Initial Forging. Selected qualified TA11 ingots are forged in two passes above the phase transformation point. First, the ingot is heated to 100°C above the phase transformation point and held for 600 minutes for the first forging pass (upsetting and drawing). Second, the ingot is heated to 50°C above the phase transformation point and held for 240 minutes for the second forging pass, followed by air cooling. The rough forging ratio for each pass is controlled at 1.5, the drawing deformation is controlled at 30%, and the final forging temperature is not lower than 800°C. After two passes, a fully fragmented and refined intermediate billet is obtained.

[0054] S3, multi-stage cyclic forging. The intermediate billet is forged five times within the range of the β phase transformation temperature to refine the microstructure. In the first stage, the billet is heated to 50°C below the phase transformation temperature, held for 420 min, and then upsetting and drawing. It is then returned to the furnace to 70°C above the phase transformation temperature, held for 120 min, and forged again. The upsetting-to-forging ratio is controlled at 1.9, the elongation deformation is controlled at 50%, and the final forging temperature is not lower than 700°C. In the second to fifth stages, the billet is heated to 50°C below the phase transformation temperature, held for 300 min, and forged again. The upsetting-to-forging ratio is controlled at 1.2, the elongation deformation is controlled at 30%, and the final forging temperature is not lower than 700°C. After forging, the billet is air-cooled.

[0055] S4, Finished bar forging. The intermediate forged billet obtained through multi-stage forging is heated to 80°C below the phase transformation temperature and held for 120 minutes. This process yields a Φ42mm bar, which, after peeling and polishing, becomes a Φ40mm finished bar (the Φ40mm specification conforms to the "25mm≤Φ≤60mm" finished size range in the technical solution). The deformation per forging pass is 10-25%, the cumulative deformation per single forging pass is 60%, the final forging temperature is not lower than 700°C, and the bar is air-cooled after forging.

[0056] Example 3

[0057] A method for preparing TA11 alloy bars with high creep resistance (Φ30mm) includes the following steps:

[0058] S1, Ingot Preparation. A Φ640mm ingot was obtained by three VAR melting processes, with an Al content of 7.70%–8.10%, a Mo content of 0.90%–1.10%, a V content of 0.90%–1.10%, an O content of 0.07%–0.12%, and a β phase transformation temperature of 1035℃–1040℃.

[0059] S2, Initial Forging. Selected qualified TA11 ingots are forged in two passes above their phase transformation point. First, the ingot is heated to 150°C above the phase transformation point and held for 480 minutes for the first forging pass (upsetting and drawing). The second forging pass involves heating to 100°C above the phase transformation point and holding for 120 minutes, followed by air cooling. The rough forging ratio for each pass is controlled at 1.9, the drawing deformation is controlled at 50%, and the final forging temperature is not lower than 800°C. After two passes, a fully fragmented and refined intermediate billet is obtained.

[0060] S3, multi-stage cyclic forging. The intermediate billet is forged five times within the range of the β phase transformation temperature to refine the microstructure. In the first stage, the billet is heated to 30°C below the phase transformation temperature, held for 360 min, and then upsetting and drawing. It is then returned to the furnace to 50°C above the phase transformation temperature, held for 240 min, and forged again. The upsetting-to-forging ratio is controlled at 1.6, the elongation deformation is controlled at 40%, and the final forging temperature is not lower than 700°C. In the second to fifth stages, the billet is heated to 60°C below the phase transformation temperature, held for 360 min, and forged again. The upsetting-to-forging ratio is controlled at 1.2, the elongation deformation is controlled at 20%, and the final forging temperature is not lower than 700°C. After forging, the billet is air-cooled.

[0061] S4, Finished bar forging. The intermediate forged billet obtained through multi-stage forging is heated to 60°C below the phase transformation temperature and held for 180 minutes. This process yields a Φ32mm bar, which, after peeling and polishing, becomes a Φ30mm finished bar (the Φ30mm specification conforms to the "25mm≤Φ≤60mm" finished size range in the technical solution). The deformation per forging pass is 10-25%, the cumulative deformation per single forging pass is 70%, the final forging temperature is not lower than 700°C, and the bar is air-cooled after forging.

[0062] Example 4

[0063] A method for preparing TA11 alloy bars with high creep resistance (Φ25mm) includes the following steps:

[0064] S1, Ingot Preparation. A Φ640mm ingot was obtained by three VAR melting processes, with an Al content of 7.70%–8.10%, a Mo content of 0.90%–1.10%, a V content of 0.90%–1.10%, an O content of 0.07%–0.12%, and a β phase transformation temperature of 1035℃–1040℃.

[0065] S2, Initial Forging. Selected qualified TA11 ingots are forged in two passes above the phase transformation point. First, the ingot is heated to 150°C above the phase transformation point and held for 600 minutes for the first forging pass (upsetting and drawing). Second, the ingot is heated to 80°C above the phase transformation point and held for 180 minutes for the second forging pass, followed by air cooling. The rough forging ratio for each pass is controlled at 1.5, the drawing deformation is controlled at 30%, and the final forging temperature is not lower than 800°C. After two passes, a fully fragmented and refined intermediate billet is obtained.

[0066] S3, multi-stage cyclic forging. The intermediate billet is forged five times within the range of the β phase transformation temperature to refine the microstructure. In the first stage, the billet is heated to 20°C below the phase transformation temperature, held for 180 min, and then upsetting and drawing. It is then returned to the furnace to 20°C above the phase transformation temperature, held for 300 min, and forged again. The upsetting-to-forging ratio is controlled at 1.6, the elongation deformation is controlled at 40%, and the final forging temperature is not lower than 700°C. In the second to fifth stages, the billet is heated to 50°C below the phase transformation temperature, held for 300 min, and forged again. The upsetting-to-forging ratio is controlled at 1.5, the elongation deformation is controlled at 40%, and the final forging temperature is not lower than 700°C. After forging, the billet is air-cooled.

[0067] S4, Finished bar forging. The intermediate forged billet obtained through multi-stage forging is heated to 50°C below the phase transformation temperature and held for 60 minutes. This results in a Φ27mm bar, which, after peeling and polishing, yields a Φ25mm finished bar (Φ25mm conforms to the "25mm≤Φ≤60mm" finished size range in the technical specifications). The deformation per forging pass is 10-25%, the cumulative deformation per single forging pass is 80%, the final forging temperature is not lower than 700°C, and the bar is air-cooled after forging.

[0068] The transverse metallographic microstructure of the TA11 bars with high creep resistance prepared according to Examples 1-4 is as follows: Figures 2-5 As shown. From metallography Figures 2-5 It can be seen that the obtained TA11 titanium alloy bar has a high magnification structure consisting of a large number of equiaxed and elongated α phases distributed on a β matrix, with an α phase content of more than 70%.

[0069] The creep resistance of the TA11 alloy bars obtained in Examples 1-4 was tested after being heat-treated according to the standard and held at 425℃ and 410MPa stress for 100h. The test results are shown in Table 1.

[0070] Table 1. Results of room temperature tensile properties

[0071]

[0072] Table 1 shows that the TA11 alloy rods prepared by the method of the present invention, after heat treatment and holding at 425℃ and 410MPa stress for 100h, have residual deformation (creep resistance) of <0.15%, which is a large margin from the standard creep resistance requirement of ≤0.2%, and can stably meet the usage requirements for stability control of high-end blade rods.

Claims

1. A method for preparing TA11 alloy rods with high creep resistance, characterized in that, The composition range of the TA11 alloy rod is: Al content 7.70%–8.20%, Mo, V content 0.90%–1.10%, O content 0.07%–0.12%, with the balance being Ti and other impurity elements. Its preparation method includes the following steps: S1, Ingot preparation: The alloy underwent three VAR melting processes to obtain TA11 alloy ingots with the required composition. S2, intermediate billet forging: The qualified ingot obtained from S1 is forged twice at a temperature above the β phase transformation point to obtain an intermediate billet. S3, Multi-fire secondary cycle forging: The TA11 alloy intermediate billet obtained from S2 was forged and deformed in five passes within the range of the β phase transformation temperature to obtain an intermediate precision forged billet with uniform microstructure and high α phase content. S4, Finished bar stock precision forging: The TA11 alloy intermediate precision forging billet obtained from S3 is precision forged below the phase transformation temperature to obtain TA11 alloy bars with high creep resistance.

2. The method for preparing TA11 alloy rods with high creep resistance according to claim 1, characterized in that, In S2, the first forging is performed by heating to 100°C to 200°C above the β phase transformation point and holding for 360 to 600 minutes; the second forging is performed by heating to 50°C to 100°C above the β phase transformation point and holding for 60 to 240 minutes, followed by air cooling.

3. The method for preparing TA11 alloy rods with high creep resistance according to claim 2, characterized in that, In S2, the rough forging ratio per forging pass is controlled at 1.5 to 1.9, the elongation deformation is controlled at 30% to 50%, and the final forging temperature is not lower than 800℃.

4. The method for preparing TA11 alloy rods with high creep resistance according to claim 1, characterized in that, In S3, the first heating is carried out at 20°C to 50°C below the phase transformation point temperature, held for 180 min to 420 min, and then drawn. The furnace is then returned to the furnace at 20°C to 70°C above the phase transformation point temperature, held for 120 min to 300 min, and then forged. After forging, the furnace is air-cooled.

5. The method for preparing TA11 alloy rods with high creep resistance according to claim 4, characterized in that, In S3, the ratio of the first upsetting to rough forging is controlled at 1.4 to 1.9, the elongation deformation is controlled at 30% to 50%, and the final forging temperature is not lower than 700℃.

6. The method for preparing TA11 alloy rods with high creep resistance according to claim 4, characterized in that, In S3, the second to fifth firings involve heating to 20°C to 60°C below the phase transformation temperature, holding at that temperature for 120 to 360 minutes, and then forging, followed by air cooling.

7. The method for preparing TA11 alloy rods with high creep resistance according to claim 6, characterized in that, In S3, the upsetting ratio is controlled between 1.2 and 1.8 in the second to fifth forging passes, the elongation deformation is controlled between 20% and 50%, and the final forging temperature is not lower than 700℃.

8. The method for preparing TA11 alloy rods with high creep resistance according to claim 1, characterized in that, In S4, the intermediate precision forging billet is heated to 50°C to 80°C below the phase transformation point temperature, held for 60 to 180 minutes, and then precision forged and air-cooled.

9. The method for preparing TA11 alloy rods with high creep resistance according to claim 8, characterized in that, In S4, the deformation amount per forging pass is 10-25%, the cumulative deformation amount per forging pass is 50%-80%, and the final forging temperature is not lower than 700℃.

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