GH4065A alloy uniform fine-grain bar and preparation method thereof

Abstract

The invention belongs to the technical field of high-temperature alloys, and particularly relates to a GH4065A alloy uniform fine-grain bar and a preparation method thereof. The preparation method comprises the following steps: carrying out vacuum induction melting, electroslag remelting and vacuum consumable remelting on required raw materials to obtain an alloy ingot; the alloy ingot is placed in a heating furnace for uniform diffusion; after the diffused cast ingot is subjected to circumferential face barreling, repeated upsetting and drawing cogging is adopted, and then the cast ingot is drawn to be in a black skin state; and the black-skin-state bar is turned to the required specification, and the bar is put into storage after being qualified through flaw detection. The grain size of the prepared GH4065A alloy uniform fine grain bar is larger than or equal to grade 8, the tensile strength at the temperature of 400 DEG C is larger than or equal to 1455 MPa, the yield strength is 1034-1268 MPa, the tensile strength at the temperature of 650 DEG C is larger than or equal to 1324 MPa, the yield strength is 979-1213 MPa, and the lasting time at the temperature of 650 DEG C and 950 MPa is larger than or equal to 50 h.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature alloy technology, specifically relating to a GH4065A alloy uniform fine-grained rod and its preparation method. Background Technology

[0002] GH4065A alloy is a novel wrought high-temperature alloy for turbine disks developed and applied domestically. Its chemical composition is an improvement on René 88DT alloy. This alloy retains excellent strength, creep resistance, and oxidation resistance even at 700℃. However, due to the high alloying degree of GH4065A, metallurgical defects are easily formed during the smelting process; the γ' phase accounts for as much as 42%, increasing the alloy's strength but decreasing its plasticity, thus increasing the difficulty of the alloy deformation process. Furthermore, the second-phase precipitation behavior of GH4065A is complex, and its narrow hot working temperature range makes it prone to cracking. Therefore, the process parameters for preparing high-quality GH4065A uniform fine-grained rods are stringent, resulting in high production difficulty. Summary of the Invention

[0003] The purpose of this invention is to overcome technical bottlenecks and supplement the deficiencies in existing technologies based on the intrinsic properties of GH4065A alloy. This invention proposes a uniform fine-grained bar of GH4065A alloy and its preparation method. Through a three-stage purification smelting + homogenization diffusion + fine-grain forging process, a GH4065A non-segregated fine-grained bar is prepared. The obtained bar has uniform microstructure and grain size ≥ 8 at all positions, and has excellent high-temperature tensile properties.

[0004] The technical solution adopted in the embodiments of the present invention is as follows: In a first aspect, embodiments of the present invention provide a method for preparing a uniform fine-grained GH4065A alloy rod, comprising the following steps: Step S1: According to the composition of GH4065A alloy, weigh the required amounts of Cr, Ni, Mo, Al, Nb, W, Co, Ti, Zr, Fe, graphite, and Ni-B, and add the above raw materials to a vacuum induction melting furnace for melting and vacuuming. After three stages—melting, refining, and casting—an electroslag remelting electrode rod is obtained after casting. The bottom of the electroslag remelting electrode rod is welded to a dummy electrode and placed in an electroslag remelting furnace for arc initiation, steady-state operation, and hot sealing to obtain a consumable remelting electrode. The bottom of the consumable remelting electrode is welded to a dummy electrode and placed in a vacuum consumable remelting furnace for arc initiation, steady-state operation, and hot sealing to obtain an alloy ingot. Step S2: Place the alloy ingot obtained in S1 after vacuum induction melting + electroslag remelting + vacuum consumable remelting into a gas-fired heating furnace for high-temperature homogenization diffusion annealing. Step S3: The alloy ingot that has undergone high-temperature homogenization and diffusion in step S2 is circumferentially rolled, and the rolled alloy ingot is preheated in a heating furnace. The preheating process adopts a two-stage heating method: first, the temperature is raised to 750±10℃ for preheating, and then the temperature is raised to 1130~1150℃ and held for more than 4 hours before forging. The forging process adopts multiple upsetting and drawing to open the billet, and then drawing it to the required forging size. Step S4: Machine the black-skinned bars to the required specifications, and put them into storage after passing the water immersion flaw detection.

[0005] Furthermore, in step S1, the temperatures of the three stages of vacuum induction melting—melting, refining, and casting—are as follows: melting stage full melting temperature 1440–1470℃, refining stage refining temperature 1500–1530℃, and casting stage casting temperature 1470–1490℃.

[0006] Further, in step S1, the electroslag remelting electrode rod is subjected to electroslag remelting to obtain a consumable remelting electrode. The slag system selected in the electroslag remelting process includes CaF2, Al2O3, CaO, MgO and TiO2. The weight ratio of CaF2, Al2O3, CaO, MgO and TiO2 in the slag system is 50±3%:20±2%:20±2%:5±0.8%:3±0.6%, and the steady-state melting rate is 4.8 to 5.2 kg / min.

[0007] Furthermore, in step S1, during the vacuum self-consumption remelting process, the vacuum degree is less than 1.0 Pa, and the steady-state melting rate is 2.8–3.2 kg / min.

[0008] Furthermore, in step S2, the annealing temperature of the high-temperature homogenization diffusion annealing is 1160–1180°C, and the holding time is 70–90 h.

[0009] Furthermore, in step S3, the forging process of the alloy ingot adopts multiple upsetting and drawing processes, with more than 5 upsetting times, and the deformation amount per upsetting process is controlled at 40% to 50%.

[0010] Furthermore, in step S3, the forging process of the alloy ingot is carried out n times in total; The first firing produces a perfectly round surface; The pre-forging temperature for each of the 2nd to 6th forging passes is 1130–1150℃, the holding time for each pass is 120–240 min, and the elongation deformation per pass is controlled at 20%–35%. The preheating temperature for the 7th to n-4th forging passes is reduced to 1095-1125℃, the holding time for each pass is 120-240 min, and the elongation deformation per pass is controlled at 25%-35%. To obtain a uniform fine-grained structure, starting from the (n-3)th forging pass, the pre-forging heating temperature is controlled at 1070–1095℃, the holding time for each pass is 120–240 min, and the elongation deformation per pass is controlled at 30%–45%. The nth firing process employs a deformation and rounding forging method, controlling the deformation amount to be 25%–35%, and the holding time for each firing is 120–240 minutes.

[0011] Furthermore, in step S3, cotton is wrapped around the metal during each forging process, and the holding time after wrapping the metal is not less than the holding time before wrapping the metal.

[0012] Furthermore, in step S4, the machining process is controlled until the surface is free of cracks, and the surface roughness of the machined alloy bar is ≤1.6μm.

[0013] Secondly, embodiments of the present invention provide a GH4065A alloy uniform fine-grained rod, prepared using the method described in the first aspect. By weight fraction, the GH4065A alloy uniform fine-grained rod comprises the following components: C 0.005%–0.008%, Cr 15.5%–16.5%, Mo 3.80%–4.20%, Ti 3.55%–3.90%, Al 1.95%–2.30%, Nb 0.60%–0.80%, B 0.012%–0.02%, W 3.80%–4.20%, Co 12.5%–13.5%, Zr 0.03%~0.06%, Si≤0.35%, Cu≤0.30%, Mn≤0.15%, Mg≤0.005%, Pb≤0.0005%, Ag≤0.0005%, Bi≤0.00003%, Ca≤0.005%, O≤0.003%, Fe≤1.20%, Se≤0.0003%, Sn≤0.005%, Ta≤0.1%, V≤0.08%, N≤0.0025%, P≤0.015%, S≤0.0008%, balance Ni.

[0014] The technical solutions of the embodiments of the present invention have the following beneficial effects: (1) The present invention optimizes the composition range of elements such as C, O, N and S in GH4065A alloy. On the other hand, it further optimizes the high-temperature homogenization diffusion process of alloy ingots, reduces element segregation in ingots, and the residual segregation index of main elements in the self-consumable ingot after adjustment is less than 0.1.

[0015] (2) The present invention adopts a fine-grained forging process of repeated upsetting and drawing of billets and drawing. No metallurgical defects such as black spots were found in the obtained bar material at low magnification and there was no abnormal inclusion aggregation. The obtained bar material has a uniform structure and a grain size ≥ 8.

[0016] (3) By increasing the number of upsetting and drawing cycles and controlling the deformation temperature, holding time and deformation amount during the upsetting and drawing process, the GH4065A alloy homogenized fine-grained rod prepared by this invention meets the following conditions: tensile strength ≥1455 MPa at 400℃, yield strength 1034~1268 MPa, tensile strength ≥1324 MPa at 650℃, yield strength 979~1213 MPa, and creep time ≥50 h at 650℃ and 950 MPa.

[0017] (4) For the first time, GH4065A high-quality uniform fine-grained bar was prepared using a 45MN fast forging machine. Its microstructure uniformity and mechanical properties meet the requirements of relevant agreements and satisfy the application requirements of high-quality GH4065A alloy bars for aero-engine turbine disks. Attached Figure Description

[0018] Figure 1 This is a grain size test diagram of the uniform fine-grained rod of GH4065A alloy in Example 1 of the present invention.

[0019] Figure 2 This is a grain size test diagram of the GH4065A alloy uniform fine-grained rod in Example 2 of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] Example 1 A method for preparing a uniform fine-grained GH4065A alloy rod includes the following steps: Step S1: According to the composition of GH4065A alloy, weigh Cr, Ni, Mo, Al, Nb, W, Co, Ti, Zr, Fe, graphite, and Ni-B, wherein the purity of Ni is >99.96%, the purity of Cr is >99.0%, and the purity of Al is >99.0%. Add the above raw materials to a vacuum melting furnace for melting and vacuuming, and proceed through three stages: melting period, refining period, and casting period (the full melting temperature during the melting period is 1445℃, the refining temperature during the refining period is 1520℃, and the casting temperature during the casting period is 1520℃). The casting temperature was 1480℃. After casting, an electroslag remelting electrode rod was obtained. The bottom of the electroslag remelting electrode rod was welded to a dummy electrode and placed in an electroslag remelting furnace. After arc initiation, steady state, and hot capping, a consumable remelting electrode was obtained. The slag system selected for electroslag remelting included CaF2, Al2O3, CaO, MgO, and TiO2. The weight ratio of CaF2:Al2O3:CaO:MgO:TiO2 in the slag system was 50:20:20:5:3. The steady-state melting rate of the electroslag process was controlled at 5.1 kg / min. Then, the bottom of the consumable remelting electrode was welded to a dummy electrode and placed in a vacuum consumable remelting furnace. After arc initiation, steady state, and hot capping, an alloy ingot was obtained. During the vacuum consumable remelting process, the vacuum degree was less than 1.0 Pa, and the steady-state melting rate was 3.1 kg / min. Step S2: Place the alloy ingot obtained in step S1 after vacuum induction melting + electroslag remelting + vacuum consumable remelting into a gas-fired heating furnace for high-temperature homogenization diffusion. The annealing temperature is 1175℃ and the holding time is 80h. Step S3: The alloy ingot after homogenization and diffusion in step S2 is circumferentially rolled, and the rolled alloy ingot is preheated in a heating furnace. The preheating process adopts a two-stage heating method: first, the temperature is raised to 750±10℃ for preheating, and then the temperature is raised to 1150℃ and held for 4 hours before forging using a 45MN fast forging machine. The forging process employs multiple upsetting and drawing operations for initial blanking, followed by drawing to the desired forging dimensions. A total of 16 forging passes are performed. The first pass rounds the surface, resulting in a denser surface microstructure and a 3% deformation. A six-upsetting multi-drawing process is then used for blanking. Passes 2, 4, 6, 8, 10, and 12 involve upsetting. For passes 2-6, the pre-forging temperature is 1145℃, with a holding time of 210±30 min, and each upsetting deformation is 41%. Passes 3 and 5 have a single-pass deformation of 23±3%. For passes 7-12, the pre-forging temperature is reduced to 11℃. The temperature is 10℃, and the holding time is 210±30min. The 7th, 9th, and 11th heating cycles are for drawing, with a single heating cycle drawing deformation of 30±4%. Starting from the 13th heating cycle, the pre-forging heating temperature is further reduced to 1090℃. The holding time for the 13th to 15th heating cycles is 210±30min, with a single heating cycle drawing deformation of 31±2%. The 16th heating cycle involves deformation and rounding, with a deformation of 26% and a holding time of 210±30min. After holding for 1.5 to 2 hours after each heating cycle, the furnace is wrapped with cotton, and after reaching the furnace temperature, it is held for another 2 hours. Step S4: Machine the black-skinned bars to Φ250 mm, ensuring the surface is free of cracks. The surface roughness of the machined alloy bars should be ≤1.6μm. After passing water immersion testing, they are put into storage.

[0022] The grain size of the GH4065A alloy uniform fine-grained rods obtained above was tested, see [see details]. Figure 1 As shown.

[0023] Example 2 A method for preparing a uniform fine-grained GH4065A alloy rod includes the following steps: Step S1: According to the composition of GH4065A alloy, weigh Cr, Ni, Mo, Al, Nb, W, Co, Ti, Zr, Fe, graphite, and Ni-B, wherein Ni purity > 99.96%, Cr purity > 99.0%, and Al purity > 99.0%. Add the above raw materials to the melting furnace for melting and vacuuming, and proceed through three stages: melting period, refining period, and casting period (melting period full melting temperature 1455℃, refining period refining temperature 1515℃, casting period casting). The temperature was 1485℃. After casting, an electroslag remelting electrode rod was obtained. The bottom of the electroslag remelting electrode rod was welded to a dummy electrode and placed in an electroslag remelting furnace. After arc initiation, steady state, and hot capping, a consumable remelting electrode was obtained. The slag system selected for electroslag remelting included CaF2, Al2O3, CaO, MgO, and TiO2. The weight ratio of CaF2:Al2O3:CaO:MgO:TiO2 in the slag system was 50:20:20:5:3. The steady-state melting rate of the electroslag process was controlled at 4.90 kg / min. Then, the bottom of the consumable remelting electrode was welded to a dummy electrode and placed in a vacuum consumable remelting furnace. After arc initiation, steady state, and hot capping, an alloy ingot was obtained. During the vacuum consumable remelting process, the vacuum degree was less than 1.0 Pa, and the steady-state melting rate was 2.80 kg / min. Step S2: Place the alloy ingot obtained in S1 after vacuum induction melting + electroslag remelting + vacuum consumable remelting into a gas-fired heating furnace for high-temperature homogenization diffusion. The annealing temperature is 1170 ℃ and the holding time is 80 h. Step S3: The alloy ingot after homogenization and diffusion in step S2 is circumferentially rolled, and the rolled alloy ingot is preheated in a heating furnace. The preheating process adopts a two-stage heating method: first, the temperature is raised to 750±10℃ for preheating, and then the temperature is raised to 1140℃ and held for 4 hours before forging using a 45MN fast forging machine. The forging process involves multiple upsetting and drawing operations to open the blank, followed by drawing it to the required forging dimensions. The forging process consisted of 14 passes. The first pass rounded the surface, resulting in a denser surface structure, with a deformation of 3%. A five-upsetting and multi-drawing process was then used for blanking. Passes 2, 4, 6, 8, and 10 involved upsetting. Passes 2-6 had a pre-forging temperature of 1140℃ and a holding time of 210±30 min, with an upsetting deformation of 43% per pass. Passes 3 and 5 had a single-pass deformation of 22±2%. Passes 7-10 reduced the pre-forging temperature to 1100℃ and held for 210±30 min. Passes 7 and 9 involved drawing, with a single-pass drawing deformation of 31±3%. From the 11th pass onwards, the pre-forging temperature further decreased to 1085℃, with a deformation of 35±5% per pass from the 11th to 13th passes. The 14th pass involved deformation and rounding, resulting in a deformation of 28%, with a holding time of 210±30 min. After each firing, the furnace is kept warm for 1.5 to 2.0 hours, then wrapped with cotton. After the furnace reaches the set temperature, it is kept warm for another 2 hours. Step S4: Machine the black-skinned bars to Φ250 mm, ensuring the surface is free of cracks. The surface roughness of the machined alloy bars should be ≤1.6μm. After passing water immersion testing, they are put into storage.

[0024] The grain size of the GH4065A alloy uniform fine-grained rods obtained above was tested, see [see details]. Figure 2 As shown.

[0025] The chemical composition of the GH4065A alloy bars in Examples 1-2 is shown in Table 1.

[0026] Table 1

[0027] The grain size and mechanical properties of the GH4065A alloy bars in Examples 1-2 are shown in Table 2.

[0028] Table 2

[0029] As can be seen from Table 2, the GH4065A alloy uniform fine-grained rods prepared by this invention meet common industry standards, have good performance in various indicators, and are highly competitive in the market.

[0030] Finally, it should be noted that the above specific embodiments are merely explanations of this application and are not intended to limit this application. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a uniform fine-grained rod of GH4065A alloy, characterized in that, Includes the following steps: Step S1: According to the composition of GH4065A alloy, weigh the required amounts of Cr, Ni, Mo, Al, Nb, W, Co, Ti, Zr, Fe, graphite, and Ni-B, and add the above raw materials to a vacuum induction melting furnace for melting and vacuuming. After three stages—melting, refining, and casting—an electroslag remelting electrode rod is obtained after casting. The bottom of the electroslag remelting electrode rod is welded to a dummy electrode and placed in an electroslag remelting furnace for arc initiation, steady-state operation, and hot sealing to obtain a consumable remelting electrode. The bottom of the consumable remelting electrode is welded to a dummy electrode and placed in a vacuum consumable remelting furnace for arc initiation, steady-state operation, and hot sealing to obtain an alloy ingot. Step S2: Place the alloy ingot obtained in S1 after vacuum induction melting + electroslag remelting + vacuum consumable remelting into a gas-fired heating furnace for high-temperature homogenization diffusion annealing. Step S3: The alloy ingot that has undergone high-temperature homogenization and diffusion in step S2 is circumferentially rolled, and the rolled alloy ingot is preheated in a heating furnace. The preheating process adopts a two-stage heating method: first, the temperature is raised to 750±10℃ for preheating, and then the temperature is raised to 1130~1150℃ and held for more than 4 hours before forging. The forging process adopts multiple upsetting and drawing to open the billet, and then drawing it to the required forging size. Step S4: Machine the black-skinned bars to the required specifications, and put them into storage after passing the water immersion flaw detection.

2. The method for preparing GH4065A alloy uniform fine-grained rods according to claim 1, characterized in that, In step S1, the temperatures of the three stages of vacuum induction melting—melting, refining, and casting—are as follows: melting stage full melting temperature 1440–1470℃, refining stage refining temperature 1500–1530℃, and casting stage casting temperature 1470–1490℃.

3. The method for preparing GH4065A alloy uniform fine-grained rods according to claim 1, characterized in that, In step S1, the electroslag remelting electrode rod is subjected to electroslag remelting to obtain a consumable remelting electrode. The slag system selected in the electroslag remelting process includes CaF2, Al2O3, CaO, MgO and TiO2. The weight ratio of CaF2, Al2O3, CaO, MgO and TiO2 in the slag system is 50±3%:20±2%:20±2%:5±0.8%:3±0.6%, and the steady-state melting rate is 4.8 to 5.2 kg / min.

4. The method for preparing GH4065A alloy uniform fine-grained rods according to claim 1, characterized in that, In step S1, during the vacuum self-consumption remelting process, the vacuum degree is less than 1.0 Pa, and the steady-state melting rate is 2.8 to 3.2 kg / min.

5. The method for preparing GH4065A alloy uniform fine-grained rods according to claim 1, characterized in that, In step S2, the annealing temperature of the high-temperature homogenization diffusion annealing is 1160-1180℃, and the holding time is 70-90 h.

6. The method for preparing GH4065A alloy uniform fine-grained rods according to claim 1, characterized in that, In step S3, the forging process of the alloy ingot adopts multiple upsetting and drawing processes, with more than 5 upsetting times, and the deformation amount per upsetting process is controlled at 40% to 50%.

7. The method for preparing GH4065A alloy uniform fine-grained rods according to claim 1 or 6, characterized in that, In step S3, the forging process of the alloy ingot involves a total of n firings; The first firing produces a perfectly round surface; The pre-forging temperature for each of the 2nd to 6th forging passes is 1130–1150℃, the holding time for each pass is 120–240 min, and the elongation deformation per pass is controlled at 20%–35%. The preheating temperature for the 7th to n-4th forging passes is reduced to 1095-1125℃, the holding time for each pass is 120-240 min, and the elongation deformation per pass is controlled at 25%-35%. To obtain a uniform fine-grained structure, starting from the (n-3)th forging pass, the pre-forging heating temperature is controlled at 1070–1095℃, the holding time for each pass is 120–240 min, and the elongation deformation per pass is controlled at 30%–45%. The nth firing process employs a deformation and rounding forging method, controlling the deformation amount to be 25%–35%, and the holding time for each firing is 120–240 minutes.

8. The method for preparing GH4065A alloy uniform fine-grained rods according to claim 1, characterized in that, In step S3, cotton is wrapped around the metal during each forging process, and the holding time after wrapping the metal is not less than the holding time before wrapping the metal.

9. The method for preparing GH4065A alloy uniform fine-grained rods according to claim 1, characterized in that, In step S4, the machining process is controlled until the surface is free of cracks, and the surface roughness of the machined alloy bar is ≤1.6μm.

10. A GH4065A alloy uniform fine-grained rod, characterized in that, Prepared by the preparation method according to any one of claims 1-9, the GH4065A alloy uniform fine-grained rod, by weight fraction, comprises the following components: C 0.005%–0.008%, Cr 15.5%–16.5%, Mo 3.80%–4.20%, Ti 3.55%–3.90%, Al 1.95%–2.30%, Nb 0.60%–0.80%, B 0.012%–0.02%, W 3.80%–4.20%, Co 12.5%–13.5%, Zr 0.03%~0.06%, Si≤0.35%, Cu≤0.30%, Mn≤0.15%, Mg≤0.005%, Pb≤0.0005%, Ag≤0.0005%, Bi≤0.00003%, Ca≤0.005%, O≤0.003%, Fe≤1.20%, Se≤0.0003%, Sn≤0.005%, Ta≤0.1%, V≤0.08%, N≤0.0025%, P≤0.015%, S≤0.0008%, balance Ni.

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