A 1Cr17Ni2 stainless steel forging and a manufacturing method thereof

Abstract

The present invention relates to the technical field of stainless steel manufacturing, and specifically to a 1Cr17Ni2 stainless steel forging and a manufacturing method thereof, wherein the manufacturing method comprises blanking, forging, tempering, rough machining, heat treatment, physical and chemical testing, and warehousing. The present invention can effectively improve the forging quality and forging efficiency by optimizing the heating temperature, forging time, holding time, tempering temperature, etc. of the forging process; by optimizing and improving the quenching temperature and time, tempering temperature and time of the heat treatment process, the obtained forging can not only meet the size requirements, but also its mechanical properties, hardness and impact properties are guaranteed, and the qualified rate is high.

Description

Technical Field

[0001] The invention relates to the technical field of stainless steel manufacturing, in particular to a 1Cr17Ni2 stainless steel forging and a manufacturing method thereof. Background Art

[0002] 1Cr17Ni2 is a martensitic stainless steel with good strength and toughness, good corrosion resistance, strength and hardness. It is mainly used in parts such as shafts, piston rods, pumps, etc. that require both toughness and corrosion resistance. At present, steel manufacturers generally deliver finished products in round bars or hexagonal bars. There is a set of standard specifications (GJB5040) for the manufacture of 1Cr17Ni2 stainless steel forgings, but not all forgings can be manufactured according to this specification. Therefore, in the manufacturing process, a certain process is generally studied, but generally only the research focuses on the influence of quenching and tempering or surface heat treatment on performance. For example, when making casing / casing assembly forgings, according to the requirements of GJB5040, although the inventor adjusted the quenching temperature in the heat treatment scheme, there is still a problem of unqualified impact performance, so that the finished product does not meet the requirements. Therefore, it is necessary to provide a qualified 1Cr17Ni2 stainless steel forging that can be used for casing / casing assembly by systematically studying the overall process. Summary of the invention

[0003] In view of the above defects or improvement needs of the prior art, the present invention provides a 1Cr17Ni2 stainless steel forging and a manufacturing method thereof. The manufacturing method optimizes the forging process and the heat treatment process at the same time, so that the 1Cr17Ni2 stainless steel forging not only has qualified dimensions, but also meets the requirements of various performance indicators and has a high pass rate.

[0004] In order to achieve the above object, the present invention provides a method for manufacturing a 1Cr17Ni2 stainless steel forging, comprising the following steps:

[0005] (1) Cutting: Use a band saw to cut the raw materials according to size and remove burrs to obtain rod segments. Specifically, the size of the rod segment is φ150×408±1. For the obtained rod segment, a lathe can be used to chamfer the end to improve the size accuracy and surface quality of the blank.

[0006] (2) Forging: The billet is placed in a gas furnace for heating. After entering the furnace, it is heated to 850℃ for 120±10min, and then heated to 1120±10℃ for 120min. Then, a 3T free hammer is used for forging, wherein the initial temperature is 1120℃ and the final forging temperature is ≥900℃. After forging, it is covered with asbestos and cooled to room temperature. Specifically, before opening the section, auxiliary tools such as hammer drills are fully preheated at 350℃ for more than 3h to improve forging efficiency and quality. When double bulging occurs, it can be returned to the furnace for reheating. By controlling the initial forging temperature and the final forging temperature, the quality of the forging can be effectively improved. After forging, the stainless steel forgings are polished and cleaned to remove surface defects such as folds, cracks, and pinch marks.

[0007] (3) Tempering: After forging, tempering is performed at 680°C for 360 minutes. After air cooling, external and internal rough machining is performed. In this step, by controlling the tempering temperature, the internal stress of the forging can be reduced, the hardness of the forging can be reduced, and machining is facilitated.

[0008] (4) Rough machining: Use a lathe to machine the forgings to a size of φ258±1 for the outer diameter and φ185±1 for the inner diameter. The inner and outer circles have the same center and the height is φ164±1.

[0009] (5) Heat treatment: The stainless steel forgings after rough processing are sent to the heat treatment plant for quenching at 980±10℃, keeping warm for 85-95min, and oil cooling for 10-20min. Then, they are tempered at 620±5℃, keeping warm for 35-40min, and water cooling for 5-10min. Finally, they are tempered at 620±5℃, keeping warm for 30min, and water cooling for 5-10min. In this step, the martensite in the stainless steel is first transformed into tempered martensite through quenching once and tempering twice. Transformed into tempered bainite; the purpose of secondary tempering is that when there is residual austenite in the quenched 1Cr17Ni2 stainless steel, it is impossible for them to be completely isothermally decomposed during the high-temperature tempering process. Instead, the stability of the residual austenite is reduced after some carbides are precipitated, and it is transformed into martensite during the tempering process. Therefore, after one tempering, when the strength of the stainless steel increases and the plasticity and toughness decrease, tempering is performed again at the original tempering temperature to decompose the newly formed martensite into tempered bainite, thereby reducing the strength and improving the plasticity and toughness to meet the requirements.

[0010] (5) Physical and chemical testing: The various properties of stainless steel forgings after heat treatment are tested and ultrasonic flaw detection is used. After passing the test, they can be put into storage.

[0011] The 1Cr17Ni2 stainless steel forging of the present invention is a cylindrical hollow forging. Due to the requirements of its mechanical properties, the inventor only improved its heat treatment process in the early stage, but it is still difficult to meet the requirements. For example, according to the standard, the tempering temperature is 500-540°C. By reducing the quenching temperature to 980°C, although the mechanical properties can meet the requirements, the 1Cr17Ni2 stainless steel forging has obvious tempering brittleness, and the impact value also decreases with the extension of tempering time or the increase of tempering temperature; in addition, it is found through research that although the quenching temperature has little effect on the impact, as the quenching temperature increases, the ferrite in the forging structure increases and residual austenite appears at the same time, affecting the side size and mechanical properties of the forging. In this regard, the inventor has gone beyond the requirements of the GJB5040 standard through a large number of experimental studies, and optimizes and improves the heating temperature, time and tempering temperature of the forging process and the quenching, tempering times, temperature and time of the heat treatment process. The obtained forging can not only meet the product size requirements, but also its mechanical properties, hardness and impact properties are guaranteed, and the qualified rate is greatly improved.

[0012] Furthermore, in the above technical solution, the weight percentage of each chemical element in the 1Cr17Ni2 stainless steel rod segment is: C 0.11-0.17%, Si≤0.80%, Mn≤0.80%, P≤0.030%, S≤0.025%, Cr 16.00-18.00%, Ni 1.50-2.50%, and the balance is Fe and unavoidable impurities.

[0013] Furthermore, in the above technical solution, the weight percentage of each chemical element in the 1Cr17Ni2 stainless steel forging is: C 0.16%, Si 0.23%, Mn 0.42%, P 0.019%, S 0.005%, Cr 16.32%, Ni2.06%, and the remainder is Fe and unavoidable impurities.

[0014] Furthermore, in the above technical solution, the 1Cr17Ni2 stainless steel forging has a chord-direction room temperature performance of tensile strength ≥978.5MPa, yield strength ≥793.25MPa, elongation ≥6.75%, cross-sectional shrinkage ≥36%, impact energy ≥29.25J, and hardness of 321-375HB.

[0015] Furthermore, in the above technical solution, the size of the 1Cr17Ni2 stainless steel forging is φ265×φ174×170.

[0016] Furthermore, in step (2) of the above technical solution, the heating coefficient is 0.7-0.9 mm / min, the time from secondary heating to forging completion does not exceed 300 min, and the holding time is 0.8 min / mm. In this technical solution, by controlling the heating coefficient, forging time and holding time, the number of times the forging fuel is returned to the furnace can be effectively reduced, and the forging efficiency can be improved.

[0017] Furthermore, in step (2) of the above technical solution, the thickness of the forging after forging is 35±1 mm.

[0018] Furthermore, in step (4) of the above technical solution, the oil cooling time is 10-20 minutes, and the water cooling time is 5-10 minutes.

[0019] The present invention also provides a 1Cr17Ni2 stainless steel forging manufactured by the manufacturing method, and the forging can be used in a casing / casing assembly.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention can effectively improve the forging quality and forging efficiency by optimizing the heating temperature, forging time, holding time, tempering temperature, etc. of the forging process; by optimizing and improving the quenching temperature and time, tempering temperature and time of the heat treatment process, the obtained forgings can not only meet the size requirements, but also have guaranteed mechanical properties, hardness and impact properties, and can be used for the manufacture of casings / casing components with a high pass rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the microstructure of the forging after forging in Example 1 of the present invention;

[0023] Figure 2 Schematic diagram of the microstructure of the forging after heat treatment in Example 1 of the present invention;

[0024] Figure 3 Schematic diagram of the microstructure of the forging after forging in Comparative Example 2 of the present invention;

[0025] Figure 4 Schematic diagram of the microstructure of the forging after heat treatment in Comparative Example 3 of the present invention;

[0026] Figure 5 Schematic diagram of the microstructure of the forging after heat treatment in Comparative Example 5 of the present invention;

[0027] Figure 6 Schematic diagram of the microstructure of the forging after heat treatment in Comparative Example 6 of the present invention. DETAILED DESCRIPTION

[0028] The experimental methods in the following examples are conventional methods unless otherwise specified. The raw materials involved in the following examples are common commercial products and can be purchased from the market unless otherwise specified.

[0029] The above-mentioned technical features of the present invention and the technical features specifically described below (such as implementation cases) can be combined with each other to form a new or preferred technical solution.

[0030] The chemical element composition indicators in the raw materials are shown in Table 1 (%):

[0031] Table 1

[0032] C Si Mn P S Cr Ni Fe and inevitable impurities 0.16％ 0.23％ 0.42％ 0.019％ 0.005％ 16.32％ 2.06％ margin

[0033] Example 1

[0034] A method for manufacturing a 1Cr17Ni2 stainless steel forging comprises the following specific steps:

[0035] (1) Cutting: Use a band saw to cut the raw materials into the size of φ150×408±1, remove the burrs, and obtain rod segments;

[0036] (2) Forging: The rod segments are placed in a gas furnace for heating. After entering the furnace, they are heated to 850°C for the first time and kept warm for 120 min. They are then heated to 1120°C for the second time and kept warm for 120 min. Then they are forged using a 3T free hammer. The initial segment temperature is 1120°C, the final forging temperature is ≥900°C, and the time from the second heating to the completion of forging is controlled within 300 min.

[0037] (3) Tempering: After forging, tempering is carried out at 680℃, and the temperature is kept for 360 minutes. After air cooling, the outer and inner circles are rough-machined. The thickness of the forging after forging is 35mm, and it is covered with asbestos and cooled to room temperature. The temperature is kept at 0.8min / mm. The microstructure of the forging after forging is shown in 100 times. Figure 1 As shown;

[0038] (4) Rough machining: Use a lathe to machine the forgings to a size of φ258±1 for the outer diameter and φ185±1 for the inner diameter. The inner and outer circles have the same center and the height is φ164±1.

[0039] (5) Heat treatment: The stainless steel forgings after rough processing are sent to the heat treatment plant for quenching at 980℃, holding for 90min, and oil cooling for 10min. Then, they are tempered at 620℃, holding for 40min, and water cooling for 10min. Finally, they are tempered at 620℃, holding for 30min, and water cooling for 10min. The microstructure of the forgings after heat treatment is shown in 100 times. Figure 2 As shown;

[0040] (6) Physical and chemical testing: The various properties of stainless steel forgings after heat treatment are tested and ultrasonic flaw detection is used. After passing the test, they can be put into storage.

[0041] 20 pieces of the finished stainless steel forgings were randomly selected for testing, and the qualified rate reached 100%. The average results of various properties were: tensile strength was 1055MPa, yield strength was 932MPa, elongation was 15.00%, cross-sectional shrinkage was 56.00%, impact energy was 45.00J, and hardness was 334HB.

[0042] Example 2

[0043] A method for manufacturing a 1Cr17Ni2 stainless steel forging comprises the following specific steps:

[0044] (1) Cutting: Use a band saw to cut the raw materials into the size of φ150×408±1, remove the burrs, and obtain rod segments;

[0045] (2) Forging: The rod segments are placed in a gas furnace for heating. After entering the furnace, they are heated to 850°C for the first time and kept warm for 110 min. They are then heated to 1130°C for the second time and kept warm for 120 min. Then they are forged with a 3T free hammer. The thickness of the forged piece is 34 mm. They are covered with asbestos and cooled to room temperature. The insulation is carried out at a rate of 0.8 min / mm. The initial segment temperature is 1120°C, the final forging temperature is ≥900°C, and the time from the second heating to the completion of forging is controlled within 300 min.

[0046] (3) Tempering: After forging, tempering is carried out at 680°C for 360 minutes. After air cooling, external and internal rough machining is carried out.

[0047] (4) Rough machining: Use a lathe to machine the forgings to a size of φ258±1 for the outer diameter and φ185±1 for the inner diameter. The inner and outer circles have the same center and the height is φ164±1.

[0048] (5) Heat treatment: The stainless steel forgings after rough processing are sent to the heat treatment plant for quenching at 990°C, holding for 85 minutes, and oil cooling for 20 minutes. Then, they are tempered at 615°C, holding for 35 minutes, and then water cooling for 5 minutes. Finally, they are tempered at 615°C, holding for 30 minutes, and then water cooling for 5 minutes.

[0049] (6) Physical and chemical testing: The various properties of stainless steel forgings after heat treatment are tested and ultrasonic flaw detection is used. After passing the test, they can be put into storage.

[0050] 20 pieces of the finished stainless steel forgings were randomly selected for testing, and the qualified rate reached 100%. The average results of various properties were: tensile strength was 1053MPa, yield strength was 926MPa, elongation was 14.50%, cross-sectional shrinkage was 52.00%, impact energy was 37.00J, and hardness was 330HB.

[0051] Example 3

[0052] A method for manufacturing a 1Cr17Ni2 stainless steel forging comprises the following specific steps:

[0053] (1) Cutting: Use a band saw to cut the raw materials into the size of φ150×408±1, remove the burrs, and obtain rod segments;

[0054] (2) Forging: The rod segments are placed in a gas furnace for heating. After entering the furnace, they are heated to 850°C for the first time and kept warm for 130 min. They are then heated to 1110°C for the second time and kept warm for 120 min. Then they are forged with a 3T free hammer. The thickness of the forged piece is 36 mm. They are covered with asbestos and cooled to room temperature. The insulation is carried out at a rate of 0.8 min / mm. The initial segment temperature is 1120°C, the final forging temperature is ≥900°C, and the time from the second heating to the completion of forging is controlled within 300 min.

[0055] (3) Tempering: After forging, tempering is carried out at 680°C for 360 minutes. After air cooling, external and internal rough machining is carried out.

[0056] (4) Rough machining: Use a lathe to machine the forgings to a size of φ258±1 for the outer diameter and φ185±1 for the inner diameter. The inner and outer circles have the same center and the height is φ164±1.

[0057] (5) Heat treatment: The stainless steel forgings after rough processing are sent to the heat treatment plant for quenching at 970°C, holding for 95 minutes, and oil cooling for 15 minutes. Then, they are tempered at 620°C, holding for 40 minutes, and then water cooling for 10 minutes. Finally, they are tempered at 620°C, holding for 30 minutes, and then water cooling for 5 minutes.

[0058] (6) Physical and chemical testing: The various properties of stainless steel forgings after heat treatment are tested and ultrasonic flaw detection is used. After passing the test, they can be put into storage.

[0059] 20 pieces of the finished stainless steel forgings were randomly selected for testing, and the qualified rate reached 100%. The average results of various properties were: tensile strength was 1026MPa, yield strength was 897MPa, elongation was 14.00%, cross-sectional shrinkage was 55.00%, impact energy was 35.00J, and hardness was 326HB.

[0060] Comparative Example 1

[0061] A method for manufacturing a 1Cr17Ni2 stainless steel forging is the same as that of Example 1, except that:

[0062] (2) Forging: The rod segments are placed in a gas furnace for heating. After entering the furnace, they are heated to 850°C for the first time and kept warm for 120 min. They are then heated to 1120°C for the second time and kept warm for 120 min. Then they are forged using a 3T free hammer. The initial temperature is 1120°C and the final forging temperature is ≥ 900°C. The time from the second heating to the completion of forging is 350 min. The microstructure of the forged piece after forging is shown in Figure 100. Figure 3 Shown

[0063] 20 pieces of the finished stainless steel forgings were randomly selected for testing, with a pass rate of 0%. The average results of the properties were as follows: tensile strength was 1125MPa, yield strength was 966MPa, elongation was 12.50%, cross-sectional shrinkage was 49.60%, impact energy was 16.70J, and hardness was 355HB.

[0064] Comparative Example 2

[0065] A method for manufacturing a 1Cr17Ni2 stainless steel forging is the same as that of Example 1, except that:

[0066] (5) Heat treatment: The stainless steel forgings after rough processing are sent to the heat treatment plant for quenching at 1020℃, holding for 90min, oil cooling for 10min, and then tempering at 620℃, holding for 40min, water cooling for 10min, and finally secondary tempering at 620℃, holding for 30min, and water cooling for 10min. The 100x microstructure of the forgings after heat treatment is as follows: Figure 4 shown.

[0067] 20 pieces of the finished stainless steel forgings were randomly selected for testing, with a pass rate of 0%. The average results of the properties were as follows: tensile strength was 137MPa, yield strength was 972MPa, elongation was 12.00%, cross-sectional shrinkage was 46.00%, impact energy was 27.70J, and hardness was 363HB.

[0068] Comparative Example 3

[0069] A method for manufacturing a 1Cr17Ni2 stainless steel forging is the same as that of Example 1, except that:

[0070] (5) Heat treatment: The rough-processed stainless steel forgings are sent to the heat treatment plant for quenching at 980°C for 100 minutes and oil cooling for 10 minutes. Then they are tempered at 620°C for 40 minutes and water cooling for 10 minutes. Finally, they are tempered at 620°C for 30 minutes and water cooling for 10 minutes.

[0071] 20 pieces of the finished stainless steel forgings were randomly selected for testing, with a pass rate of 10%. The average results of the properties were as follows: tensile strength was 1133MPa, yield strength was 1065MPa, elongation was 14.00%, cross-sectional shrinkage was 57.91%, impact energy was 18.47J, and hardness was 376HB.

[0072] Comparative Example 4

[0073] A method for manufacturing a 1Cr17Ni2 stainless steel forging is the same as that of Example 1, except that:

[0074] (5) Heat treatment: The stainless steel forgings after rough processing are sent to the heat treatment plant for quenching at 980℃, heat preservation for 90 minutes, oil cooling for 10 minutes, and then tempering at 540℃, heat preservation for 40 minutes, and water cooling for 10 minutes; finally, secondary tempering at 540℃, heat preservation for 30 minutes, and water cooling for 10 minutes. The microstructure of the forging after heat treatment is shown in 100 times. Figure 5 shown.

[0075] 20 pieces of the finished stainless steel forgings were randomly selected for testing, with a pass rate of 0%. The average results of the properties were as follows: tensile strength was 1261MPa, yield strength was 1103MPa, elongation was 10.50%, cross-sectional shrinkage was 53.20%, impact energy was 11.80J, and hardness was 378HB.

[0076] Comparative Example 5

[0077] A method for manufacturing a 1Cr17Ni2 stainless steel forging is the same as that of Example 1, except that:

[0078] (5) Heat treatment: The stainless steel forgings after rough processing are sent to the heat treatment plant for quenching at 980℃, heat preservation for 90min, oil cooling for 10min, and then tempering at 620℃, heat preservation for 120min, and water cooling for 10min; finally, secondary tempering at 620℃, heat preservation for 120min, and water cooling for 10min. The microstructure of the forging after heat treatment is shown in 100 times. Figure 6 shown.

[0079] 20 pieces of the finished stainless steel forgings were randomly selected for testing, with a pass rate of 10%. The average results of the properties were as follows: tensile strength was 956MPa, yield strength was 821MPa, elongation was 18.00%, cross-sectional shrinkage was 58.20%, impact energy was 15.00J, and hardness was 309HB.

[0080] Comparative Example 6

[0081] A method for manufacturing a 1Cr17Ni2 stainless steel forging is the same as that of Example 1, except that:

[0082] (5) Heat treatment: The rough-processed stainless steel forgings are sent to the heat treatment plant for quenching at 980°C, kept at this temperature for 90 minutes, and then oil-cooled for 10 minutes. They are then tempered at 620°C, kept at this temperature for 40 minutes, and then water-cooled for 10 minutes.

[0083] 20 pieces of the finished stainless steel forgings were randomly selected for testing, with a pass rate of 20%. The average results of the properties were as follows: tensile strength was 1067MPa, yield strength was 903MPa, elongation was 13.50%, cross-sectional shrinkage was 48.00%, impact energy was 28.00J, and hardness was 331HB.

[0084] in conclusion:

[0085] It can be seen from the performance test results of Examples 1 to 3 that the 1Cr17Ni2 stainless steel forgings obtained by the manufacturing method of the present invention have a tensile strength of ≥978.5MPa, a yield strength of ≥793.25MPa, an elongation of ≥6.75%, a cross-sectional shrinkage of ≥36%, an impact energy of ≥29.25J, a hardness of 321-375HB, excellent performance, all of which can meet the performance requirements and have a high pass rate.

[0086] Comparing Example 1 with Comparative Example 1, the forging holding time in Comparative Example 1 is too long, and the overall performance of the stainless steel forgings obtained is poor, especially the impact energy cannot meet the requirements. This is mainly because the forging time is too long, which makes the forgings tend to be over-burned, resulting in low overall performance of the forgings after heat treatment. Figure 1 and Figure 3 It can also be seen.

[0087] Comparing Example 1 with Comparative Examples 2-3, the overall performance of the stainless steel forging obtained in Comparative Example 2 using a higher quenching temperature is worse than that in Example 1, especially the impact energy, indicating that the quenching temperature has a greater influence on the impact energy. Figure 2 and Figure 4 It can be seen that Figure 4 As the quenching temperature increases, the ferrite in the structure will increase and residual austenite will appear; in Comparative Example 3, extending the quenching time is not conducive to the improvement of impact energy and hardness.

[0088] Comparing Example 1 with Comparative Examples 4-5, the tempering temperature in Comparative Example 4 is carried out according to the GJB5040 standard, and the performance of the obtained stainless steel forgings cannot meet the requirements, especially the impact work and hardness. This is probably because 1Cr17Ni2 has obvious temper brittleness at this temperature, which significantly reduces the impact performance; in Comparative Example 5, a longer tempering time is used. Although other properties are relatively good, the impact performance is significantly reduced. It can be seen that the impact value of the stainless steel forging will decrease with the extension of the tempering time, and its hardness is also affected.

[0089] Compared with Example 1 and Comparative Example 6, in Comparative Example 6, only one tempering was performed. Although other performance indicators were good, the impact work did not meet the requirements, indicating that the impact toughness of the stainless steel forging can be effectively improved through secondary tempering.

[0090] Finally, it should be emphasized that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various changes and modifications. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for manufacturing a 1Cr17Ni2 stainless steel forging for a casing, characterized in that: The 1Cr17Ni2 stainless steel forging has a chord-direction room temperature tensile strength of ≥978.5MPa, a yield strength of ≥793.25MPa, an elongation of ≥6.75%, a cross-sectional shrinkage of ≥36%, an impact energy of ≥29.25J, and a hardness of 321-375HB; The manufacturing method thereof comprises the following steps: (1) Cutting: Use a band saw to cut the raw materials into the size of φ150×408±1mm and remove the burrs to obtain rod segments; (2) Forging: Place the rod segments in a gas furnace for heating. After entering the furnace, heat to 850°C for the first time and keep warm for 120±10min. Heat to 1120±10°C for the second time and keep warm for 120min. Then use a 3T free hammer for forging. The initial temperature is 1120°C and the final forging temperature is ≥900°C. After forging, cover with asbestos and cool to room temperature. The heating coefficient is 0.7-0.9mm / min. The time from the second heating to the completion of forging does not exceed 300min. (3) Tempering: After forging, tempering is carried out at 680°C for 360 minutes. After air cooling, external and internal rough machining is performed. (4) Rough machining: Use a lathe to machine the forging to an outer diameter of φ258±1mm, an inner diameter of φ185±1mm, with the inner and outer circles sharing the same center and a height of 164±1mm; (5) Heat treatment: The stainless steel forgings after rough processing are sent to the heat treatment plant for quenching at 980±10℃, keeping warm for 85-95min, oil cooling, and then tempering at 620±5℃, keeping warm for 35-40min, and then water cooling; finally, secondary tempering at 620±5℃, keeping warm for 30min, and then water cooling; (6) Physical and chemical testing: The various properties of stainless steel forgings after heat treatment are tested and ultrasonic flaw detection is used. After passing the test, they can be put into storage.

2. The method for manufacturing a 1Cr17Ni2 stainless steel forging for a casing according to claim 1, characterized in that: The weight percentages of the chemical elements in the 1Cr17Ni2 stainless steel rod segment are: C 0.11-0.17%, Si≤0.80%, Mn≤0.80%, P≤0.030%, S≤0.025%, Cr 16.00-18.00%, Ni 1.50-2.50%, and the remainder is Fe and unavoidable impurities.

3. The method for manufacturing a 1Cr17Ni2 stainless steel forging for a casing according to claim 2, characterized in that: The weight percentages of the chemical elements in the 1Cr17Ni2 stainless steel forging are: C 0.16%, Si 0.23%, Mn 0.42%, P 0.019%, S 0.005%, Cr 16.32%, Ni 2.06%, and the remainder is Fe and unavoidable impurities.

4. The method for manufacturing a 1Cr17Ni2 stainless steel forging for a casing according to claim 1, characterized in that: In step (2), the holding time is 0.8 min / mm.

5. The method for manufacturing a 1Cr17Ni2 stainless steel forging for a casing according to claim 1, characterized in that: In step (5), the oil cooling time is 10-20 minutes, and the water cooling time is 5-10 minutes.

6. The method for manufacturing a 1Cr17Ni2 stainless steel forging for a casing according to claim 1, characterized in that: Before forging in step (2), the auxiliary tool is preheated at 350°C for more than 3 hours.

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