Preparation method of cold-rolled sheet of Alloy 90 high-temperature alloy

Abstract

The invention belongs to the technical field of preparation of high-temperature alloy cold-rolled sheets, and particularly relates to a preparation method of an Alloy 90 high-temperature alloy cold-rolled sheet, which comprises the steps of vacuum induction melting, air consumable melting, forging, hot rolling and cold rolling. According to the method, an element material with the purity larger than or equal to 99.95% is used, vacuum induction melting is carried out under high vacuum in the whole process, a high-purity alloy ingot is obtained, after the surface is turned by at least 20 mm, vacuum consumable melting is carried out under high vacuum and low current voltage, then the surface is turned by at least 30 mm, forging is carried out, high-temperature heating and small deformation are required for forging, and it is guaranteed that a forging stock with the surface free of cracks is obtained; and surface polishing is not needed, hot rolling is directly conducted, and the yield can be increased by 3%-5%. Hot rolling follows the high-temperature small deformation principle, it is ensured that a hot-rolled blank without cracks on the surface is obtained, cold rolling follows the large deformation principle, the number of times of the rolling process is reduced, the cost is reduced, the yield is increased, and finally a high-quality Alloy 90 high-temperature alloy cold-rolled sheet finished product is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of cold-rolled thin plates of high-temperature alloys, and in particular relates to a preparation method of a cold-rolled thin plate of Alloy 90 high-temperature alloy. Background Art

[0002] Alloy 90 high temperature alloy is an aging-strengthened nickel-based deformable high temperature alloy composed of nickel, chromium, cobalt, iron and other elements. Alloy 90 high temperature alloy replaces part of the Ni element in the matrix with 15% (mass fraction) Co element and reduces the content of Fe element. The addition of Co element can reduce the stacking fault energy of the matrix, play the effect of strengthening the matrix, and increase the dissolution temperature and high temperature resistance of the γ' phase, inhibit the precipitation of carbides, and the reduction of Fe element content reduces the precipitation of harmful phases and improves the oxidation resistance. Due to the above strengthening mechanism, Alloy 90 high temperature alloy has excellent high temperature strength, oxidation resistance and creep resistance. It is often used in turbine disks, turbine blades, high temperature fasteners, seals and high temperature springs, and is used in the energy industry for the manufacture of gas turbine blades, burner parts, etc. In high temperature and high pressure working environments, Alloy 90 high temperature alloy can maintain its stable performance and improve the working efficiency and reliability of equipment.

[0003] At present, the cold-rolled thin plate products made of Alloy 90 high-temperature alloy in the industry often have uneven thickness control due to their high hardness, high strength and large work hardening rate. That is, the thickness tolerance of the whole plate is large, and defects such as pits, pitting, small cracks, and oxide scale that is not completely pickled clean often appear on the surface, which seriously affects the subsequent deep processing of customers. In addition, the above defects often cause the finished cold-rolled plates to be scrapped or downgraded, which greatly reduces the yield rate and increases the processing cost of manufacturers. Summary of the invention

[0004] The purpose of the present invention is to solve the quality problem of the cold-rolled sheet product of Alloy 90 high-temperature alloy, and to develop a method for preparing the cold-rolled sheet of Alloy 90 high-temperature alloy. The present invention obtains a cold-rolled sheet product with uniform thickness, high performance and high surface quality by comprehensively developing vacuum induction melting, vacuum consumable melting, forging, hot rolling, cold rolling and semi-finished product processing between processes, and strictly and stably controlling key process parameters, materials and processing tools.

[0005] To achieve the above technical objectives, the technical solution adopted in the embodiment of the present invention is: a method for preparing a cold-rolled sheet of Alloy 90 high-temperature alloy, comprising the following steps:

[0006] (1) Vacuum induction melting: Alloy 90 high temperature alloy raw material is subjected to vacuum induction melting, and the vacuum degree of the whole process of vacuum induction melting is ≤0.1Pa;

[0007] (2) Vacuum consumable melting: The alloy liquid in step (1) is subjected to vacuum consumable melting. After the melting is completed, it is cooled in a crystallizer for at least 7 hours and demolded;

[0008] (3) Forging: The surface of the vacuum consumable ingot obtained in step (2) is polished by at least 30 mm, and then forged into a slab. During the forging process, the deformation amount of each fire is not higher than 40%, and the final forging temperature is not lower than 1000° C., so as to obtain a slab without surface cracks;

[0009] (4) Hot rolling: The hot rolling heating system adopts a furnace loading temperature of ≤550℃, a heating rate of ≤40℃ / min, and the temperature is kept at 1170-1200℃, and two hot rollings are performed;

[0010] (5) Cold rolling: Cold rolling is carried out using high-speed steel rollers with a convexity specification of 0.12-0.16mm W18Cr4V. The thickness tolerance of the cold-rolled plate with a thickness of 1.6-2.5mm is within ±0.07mm, the grain size is better than grade 4, and the surface of the finished plate is basically free of surface defects such as pits, oxide scale, and cracks.

[0011] Furthermore, during the vacuum consumable melting in step (2), the surface of the vacuum induction electrode is polished by at least 20 mm, the vacuum consumable melting speed is controlled at 5-9 kg / min, the melting current is 5000-6000 A, the melting voltage is 18-25 V, and the cooling water temperature shall not be higher than 30°C.

[0012] Furthermore, in step (3), the heating system when forging into a slab is: charging temperature ≤ 550°C, heating rate ≤ 40°C / min, and keeping at 1160-1200°C for 5-10h.

[0013] Furthermore, in step (4), during hot rolling, the first rolling is performed to a thickness of 7-9 mm, the final rolling temperature is not less than 1000° C., and the steel is returned to the furnace for heat preservation; the second rolling is performed to a thickness of 3.3-4.2 mm, and the steel is returned to the furnace for heat preservation;

[0014] The temperature of the first hot rolling and the second hot rolling is 1170-1200°C, and the insulation time t=thickness h×3, wherein the unit of the insulation time t is min, and the unit of the thickness h is mm.

[0015] Furthermore, in step (5), when cold rolling is performed, the first cold rolling is performed from 3.3-4.2 mm to 2.4-2.8 mm, annealed at 1150-1170° C. for 3-5 min, air-cooled, pickled with a mixed acid of 40%-50% sulfuric acid and 50%-60% hydrochloric acid at 60-80° C., and soaked for 50-80 min;

[0016] The second cold rolling is from 2.4-2.8mm to the target thickness of 1.6-2.5mm, annealing and heat preservation at 1140-1160℃ for 3-5min, water cooling, pickling with a mixed acid of 40%-50% sulfuric acid and 50%-60% hydrochloric acid at 60-80℃, and soaking for 50-80min.

[0017] Furthermore, the elemental composition of the cold-rolled sheet of Alloy 90 high-temperature alloy obtained in step (5) is as follows: C 0.02wt%-0.07wt%, Cr 20wt%-21wt%, Co 15wt%-20wt%, Ti 2.1wt%-3.1wt%, Al 0.9wt%-2.0wt%, B 0.005wt%-0.025wt%, Zr 0.01wt%-0.06wt%, Fe≤0.2wt%, Cu≤0.25wt%, the balance is Ni, and the total content of impurity elements including O, N, Pb, Bi, Sn, As, Se and Sb is ≤50ppm.

[0018] The technical solution provided by the embodiment of the present invention has the following beneficial effects:

[0019] (1) The present invention strictly controls the content of impurity elements that affect hot working properties in the smelting element material, and combines the high heating temperature, small deformation amount and high final forging temperature of the forging and hot rolling hot working processes to obtain an intermediate semi-finished slab with no surface cracks, thereby eliminating the surface grinding process and increasing the yield rate by 3%-5%.

[0020] (2) The present invention has developed a mixed acid of 40%-50% sulfuric acid and 50%-60% hydrochloric acid in a specific ratio, and experimentally found that the optimal pickling conditions for Alloy 90 high-temperature alloy are a temperature of 60-80°C and an immersion time of 50-80 minutes. This pickling process and parameters can obtain a pickled semi-finished slab with substantially no oxide scale on the surface, which can prevent the surface defect problem caused by the pressing of oxide scale on the surface of the hot-rolled raw material slab during the cold rolling stage.

[0021] (3) Alloy 90 high-temperature alloy is cold rolled using W18Cr4V high-speed steel rollers with a convexity of 0.12-0.16 mm. W18Cr4V high-speed steel has the characteristics of high strength, rigidity and toughness. When cold rolling Alloy 90 high-temperature alloy, its elastic rebound is small. Compared with rollers made of other materials, it can obtain excellent thickness uniformity of cold-rolled thin plates. The mass production results confirm that the thickness uniformity of 1.6 mm, 2.0 mm and 2.5 mm thin plates is 1.6±0.03 mm, 2.0±0.05 mm and 2.5±0.06 mm, respectively.

[0022] (4) The present invention uses element materials with a purity of ≥99.95% and performs vacuum induction melting under high vacuum throughout the process to obtain an alloy ingot with high purity. After the surface is polished to at least 20 mm, vacuum consumable melting is performed under high vacuum and low current voltage, and then the surface is polished to at least 30 mm, and then forging is performed. Forging requires high temperature heating and small deformation to ensure that a forging billet with no surface cracks is obtained. Then, hot rolling is directly performed without surface polishing, which can increase the yield rate by 3%-5%. Hot rolling follows the principle of high temperature and small deformation to ensure that a hot-rolled billet with no surface cracks is obtained. Cold rolling follows the principle of large deformation to reduce the number of rolling processes, reduce costs and improve the yield rate, and finally obtain a high-quality Alloy 90 high-temperature alloy cold-rolled thin plate product. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the grain size diagram of the first cold-rolled thin plate sample of Alloy 90 high-temperature alloy in Example 1.

[0024] Figure 2 This is the grain size diagram of the first cold-rolled thin plate sample of Alloy 90 high-temperature alloy in Example 2. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0026] Example 1

[0027] A method for preparing a cold-rolled sheet of Alloy 90 high-temperature alloy comprises the following steps:

[0028] (1) Vacuum induction melting: Alloy 90 high temperature alloy raw material is subjected to vacuum induction melting, and the vacuum degree during the whole process of vacuum induction melting is 0.05-0.1Pa;

[0029] (2) Vacuum consumable melting: The alloy liquid in step (1) is subjected to vacuum consumable melting. During vacuum consumable melting, the surface of the vacuum induction electrode is polished to 26 mm, the vacuum consumable melting speed is controlled at 6.5 kg / min, the melting current is 5600 A, the melting voltage is 21 V, and the cooling water temperature is set to 25 ° C. After the melting is completed, it is cooled in the crystallizer for 9 hours and demolded;

[0030] (3) Forging: The vacuum consumable ingot obtained in step (2) is polished by 30 mm on the surface, and then put into a furnace. The heating system adopts a furnace loading temperature of 350°C, a heating rate of 40°C / min, and a heat preservation temperature of 1170°C for 8 hours to forge into a 80 mm slab. The deformation amount of each fire during the forging process is 35%. The final forging temperature is 1000°C to obtain a slab with no surface cracks. The slab surface is not ground and directly enters the hot rolling process;

[0031] (4) Hot rolling: The hot rolling heating system adopts 500℃ charging, heating rate 40℃ / min, heating to 1200℃, keeping temperature for 240min, and performing two hot rolling;

[0032] The first rolling process is to roll the steel to a thickness of 9 mm, the final rolling temperature is 1000°C, and the steel is returned to the furnace for heat preservation at 1200°C for 27 minutes; the second rolling process is to roll the steel to a thickness of 4±0.2 mm, return to the furnace for heat preservation at 1180°C for 12 minutes, and then water-cooled after exiting the furnace;

[0033] (5) Cold rolling: cold rolling was performed using a high-speed steel roll of 0.15 mm convexity W18Cr4V. The first cold rolling was performed from 4.2 mm to 2.8 mm, annealed at 1170°C for 4 min, air cooled, pickled with 50% sulfuric acid and 50% hydrochloric acid at 80°C, and soaked for 60 min; the second cold rolling was performed from 2.8 mm to 2.5 mm (the final product size was 2.5*1000*2000 mm), 1150 Annealing and heat preservation at ℃ for 4min, water cooling, pickling with 40% sulfuric acid and 60% hydrochloric acid at 80℃, soaking for 50min; after these two rolling processes of cold rolling, the thickness tolerance of the obtained cold-rolled plate can reach within 2.5±0.06mm, the grain size is 4-4.5, and the surface of the finished plate is basically free of pits, oxide scale, cracks and other surface defects. The yield rate is increased by 4% compared with the existing "forging-grinding-hot rolling" process.

[0034] The element composition of the cold-rolled sheet of Alloy 90 high-temperature alloy obtained in step (5) is as follows: C 0.06wt%, Cr20.5wt%, Co 18wt%, Ti 2.7wt%, Al 1.68wt%, B 0.01wt%, Zr 0.02wt%, Fe 0.15wt%, Cu 0.2wt%, the balance is Ni, and the total content of impurity elements including O, N, Pb, Bi, Sn, As, Se and Sb is 50ppm.

[0035] The properties of the cold-rolled thin plate obtained in Example 1 (after aging at 925°C ± 10°C / 1h and 750°C ± 10°C / 4h) and the thickness tolerance are shown in Tables 1 and 2:

[0036] Table 1 Related properties of Alloy 90 high temperature alloy sheet products prepared in Example 1

[0037]

[0038] From the results in Table 1, it can be seen that 3 samples were randomly selected from Example 1 for mechanical property testing, and it was found that their mechanical properties and microstructure had good uniformity, grain size 5-5.5, hardness 215-220HV, tensile strength 1245-1265MPa, yield strength 830-853MPa, elongation 30%-35%, and cross-sectional shrinkage 32%-40%.

[0039] The thickness tolerance of the 5 cold-rolled thin plates prepared in Example 1 was measured, and the results are shown in Table 2.

[0040] Table 2 Thickness tolerance measurement results of 5 cold-rolled sheets prepared in Example 1

[0041]

[0042] From the results in Table 3, it can be seen that 5 samples were randomly selected from Example 1 for thickness uniformity detection, wherein 12 points of each sample were randomly measured. It can be seen that the cold-rolled thin plate rolled by the technical method of the present invention has very excellent thickness uniformity, reaching 2.5±0.06mm, which is better than the commonly used EN 10259 standard of 2.5±0.09mm.

[0043] Example 2

[0044] A method for preparing a cold-rolled sheet of Alloy 90 high-temperature alloy comprises the following steps:

[0045] (1) Vacuum induction melting: Alloy 90 high temperature alloy raw material is subjected to vacuum induction melting, and the vacuum degree during the whole process of vacuum induction melting is 0.05-0.1Pa;

[0046] (2) Vacuum consumable melting: The alloy liquid in step (1) is subjected to vacuum consumable melting. During vacuum consumable melting, the surface of the vacuum induction electrode is polished to 22 mm. The vacuum consumable melting speed is controlled at 7 kg / min, the melting current is 5800 A, the melting voltage is 22 V, and the cooling water temperature is set to 27 ° C. After the melting is completed, it is cooled in the crystallizer for 7 hours and demolded;

[0047] (3) Forging: The surface of the vacuum consumable ingot obtained in step (2) is polished by 30 mm, and then put into a furnace. The heating system adopts a furnace loading temperature of 450°C, a heating rate of 35°C / min, and a heat preservation temperature of 1170°C for 7 hours to forge a slab with a thickness of 80 mm. During the forging process, the deformation amount of each fire is 30%, and the final forging temperature is 1020°C to obtain an intermediate slab with no surface cracks. The slab does not need to be surface ground and directly enters hot rolling;

[0048] (4) Hot rolling: The hot rolling heating system adopts 550℃ charging, heating rate 30℃ / min, heating to 1200℃, and keeping temperature for 240min;

[0049] The first heat rolling was to 9mm, the final rolling temperature was 1030℃, and the furnace was returned to keep warm, and kept warm at 1200℃ for 27min;

[0050] The steel is rolled for the second time to a thickness of 4±0.2 mm, returned to the furnace for heat preservation at 1180°C for 12 min, and then water-cooled after being taken out of the furnace;

[0051] (5) Cold rolling: cold rolling was performed using a high-speed steel roll of 0.14 mm crown specification W18Cr4V. The first cold rolling was performed from 3.4 mm to 2.6 mm. Annealing was performed at 1170°C for 4 min, followed by air cooling. Pickling was performed using 40% sulfuric acid and 60% hydrochloric acid at 80°C, and soaking was performed for 50 min.

[0052] The second cold rolling is from 2.6mm to 2.0mm (the final finished product size is 2.0*1000*2000mm), annealed at 1150℃ for 4min, water-cooled, pickled with 40% sulfuric acid and 60% hydrochloric acid at 80℃, and soaked for 50min; after these two cold rolling processes, the thickness tolerance of the obtained cold-rolled plate can reach within 2.0±0.05mm, the grain size is better than grade 4, and the surface of the finished plate is basically free of surface defects such as pits, oxide scale, cracks, etc., which is a high-quality cold-rolled plate.

[0053] The element composition of the cold-rolled sheet of Alloy 90 high-temperature alloy obtained in step (5) is as follows: C 0.062wt%, Cr20wt%, Co 19wt%, Ti 2.65wt%, Al 1.65wt%, B 0.019wt%, Zr 0.05wt%, Fe 0.1wt%, Cu 0.15wt%, the balance is Ni, and the total content of impurity elements including O, N, Pb, Bi, Sn, As, Se and Sb is 45ppm.

[0054] After the above process steps, the cold-rolled sheet properties (after aging at 925℃±10℃ / 1h and 750℃±10℃ / 4h) and sheet thickness tolerance of the obtained Alloy 90 high-temperature alloy are shown in Table 3 and Table 4:

[0055] Table 3 Relevant properties of Alloy 90 high temperature alloy sheet products prepared in Example 2

[0056]

[0057] From the results in Table 3, it can be seen that 3 samples were randomly selected from Example 2 for mechanical property and microstructure testing, and it can be found that their mechanical properties and microstructure have good uniformity, grain size 5-5.5, hardness 209-215HV, tensile strength 1245-1259MPa, yield strength 833-849MPa, elongation 36%-38%, and cross-sectional shrinkage 39%-42%.

[0058] Table 4 Thickness tolerance measurement results of 5 cold-rolled sheets prepared in Example 2

[0059]

[0060] From the results in Table 4, it can be seen that 5 samples were randomly selected from Example 1 for thickness uniformity testing, wherein 12 points of each sample were randomly measured. It can be seen that the cold-rolled thin plate rolled using the technical method of the present invention has very excellent thickness uniformity, reaching 2.0±0.05mm.

[0061] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a cold-rolled sheet of Alloy 90 high-temperature alloy, characterized in that: The steps include: (1) Vacuum induction melting: Alloy 90 high temperature alloy raw material is subjected to vacuum induction melting, and the vacuum degree of the whole process of vacuum induction melting is ≤0.1Pa; (2) Vacuum consumable melting: The alloy liquid in step (1) is subjected to vacuum consumable melting. After melting, it is cooled in a crystallizer for at least 7 hours and demolded; (3) Forging: The surface of the vacuum consumable ingot obtained in step (2) is polished by at least 30 mm, and then forged into a slab. During the forging process, the deformation amount of each fire is not higher than 40%, and the final forging temperature is not lower than 1000°C, so as to obtain a slab with no surface cracks; (4) Hot rolling: The hot rolling heating system adopts a furnace loading temperature of ≤550℃, a heating rate of ≤40℃ / min, and after heating to 1170-1200℃, the temperature is kept constant and two hot rollings are performed; (5) Cold rolling: Use high-speed steel rollers with a convexity of 0.12-0.16mm W18Cr4V for cold rolling. The thickness tolerance of the cold-rolled plate with a thickness of 1.6-2.5mm is within ±0.07mm, the grain size is better than grade 4, and the surface of the finished plate is basically free of surface defects such as pits, oxide scale, and cracks.

2. The method for preparing the cold-rolled sheet of Alloy 90 high-temperature alloy according to claim 1, characterized in that: During the vacuum consumable melting in step (2), the surface of the vacuum induction electrode is polished by at least 20 mm, the vacuum consumable melting speed is controlled at 5-9 kg / min, the melting current is 5000-6000 A, the melting voltage is 18-25 V, and the cooling water temperature shall not be higher than 30°C.

3. The method for preparing the cold-rolled sheet of Alloy 90 high-temperature alloy according to claim 1, characterized in that: In step (3), the heating system when forging into a slab is: charging temperature ≤ 550°C, heating rate ≤ 40°C / min, and keeping at 1160-1200°C for 5-10h.

4. The method for preparing the cold-rolled sheet of Alloy 90 high-temperature alloy according to claim 1, characterized in that: In step (4), during hot rolling, the first rolling is performed to a thickness of 7-9 mm, the final rolling temperature is not less than 1000°C, and the steel is returned to the furnace for heat preservation; the second rolling is performed to a thickness of 3.3-4.2 mm, and the steel is returned to the furnace for heat preservation; The temperature of the first hot rolling and the second hot rolling is 1170-1200℃, and the holding time t=thickness h×3, where the unit of the holding time t is min and the unit of the thickness h is mm.

5. The method for preparing the cold-rolled sheet of Alloy 90 high-temperature alloy according to claim 1, characterized in that: In step (5), during the cold rolling, the first cold rolling is performed from 3.3-4.2 mm to 2.4-2.8 mm, annealed at 1150-1170° C. for 3-5 min, air-cooled, pickled with a mixed acid of 40%-50% sulfuric acid and 50%-60% hydrochloric acid at 60-80° C., and soaked for 50-80 min; The second cold rolling is from 2.4-2.8mm to the target thickness of 1.6-2.5mm, annealed at 1140-1160℃ for 3-5min, water-cooled, pickled with a mixed acid of 40%-50% sulfuric acid and 50%-60% hydrochloric acid at 60-80℃, and soaked for 50-80min.

6. The method for preparing the cold-rolled sheet of Alloy 90 high-temperature alloy according to claim 1, characterized in that: The element composition of the cold-rolled sheet of Alloy 90 high-temperature alloy obtained in step (5) is as follows: C 0.02wt%-0.07wt%, Cr 20wt%-21wt%, Co 15wt%-20wt%, Ti 2.1wt%-3.1wt%, Al 0.9wt%-2.0wt%, B 0.005wt%-0.025wt%, Zr0.01wt%-0.06wt%, Fe≤0.2wt%, Cu≤0.25wt%, the balance is Ni, and the total content of impurity elements including O, N, Pb, Bi, Sn, As, Se and Sb is ≤50ppm.

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