High-flow impeller heat treatment method

Abstract

The invention relates to a high-flow impeller heat treatment method which comprises the following steps that before welding, a cover disc and a shaft disc are subjected to heat treatment, specifically, the cover disc and the shaft disc are subjected to normalizing treatment, quenching treatment and tempering treatment in sequence, an impeller is made of martensitic steel, and when the yield strength Re of the impeller material is required to be larger than or equal to 515 and smaller than 700 MPa, and the yield strength of a welding seam is larger than or equal to 420 MPa, the impeller is subjected to heat treatment; the quenching treatment on the cover disc and the shaft disc comprises primary quenching treatment and secondary quenching treatment, and the heating temperature of the secondary quenching treatment is lower than that of the primary quenching treatment; when the yield strength of the impeller material is required to be greater than or equal to 700MPa and the yield strength of the welding seam is required to be greater than or equal to 420MPa, quenching treatment is only performed on the cover disc and the shaft disc once; welding by using a welding rod to obtain an impeller; and the impeller is subjected to stress relief treatment and performance heat treatment. The heat treatment method solves the problem that the large-flow impeller is not easy to carry out thermal treatment such as thermal refining.

Description

Technical Field

[0001] The present application relates to the technical field of material heat treatment, and in particular to a heat treatment method for a large flow impeller. Background Art

[0002] The impeller is the heart of the cryogenic centrifugal compressor. It has harsh working conditions and is affected not only by centrifugal force but also by low temperature conditions. The impeller is usually welded from a cover plate and a shaft plate. Martensitic steel is used as the material for the cover plate and shaft plate of the impeller to meet the high strength requirements. In order to ensure the safe operation of the impeller, the performance heat treatment of the impeller is generally carried out after the impeller is welded, which not only ensures the mechanical properties of the parent material, but also ensures the quality of the weld. However, due to the large difference in chemical composition between the welding material and the parent material used in the large flow impeller, especially the austenitic welding rod, it is not easy to perform quenching and tempering treatment on the parent material after the impeller is welded. Summary of the invention

[0003] The purpose of this application is to provide a large flow impeller heat treatment method to solve the above technical problems and improve the impeller heat treatment method according to different requirements for impeller materials.

[0004] This application adopts the following technical solutions:

[0005] A large flow impeller heat treatment method comprises the following steps:

[0006] The cover plate and the shaft plate are heat treated before welding: the cover plate and the shaft plate are subjected to normalizing treatment, quenching treatment and tempering treatment in sequence.

[0007] Wherein, the material of the impeller is martensitic steel, and when the yield strength Re of the impeller material is required to be 515≤Re<700MPa, and the yield strength of the weld is ≥420MPa, the quenching treatment performed on the cover disc and the shaft disc includes a first quenching treatment and a second quenching treatment, and the heating temperature of the second quenching treatment is lower than the heating temperature of the first quenching treatment; when the yield strength of the impeller material is required to be ≥700MPa, and the yield strength of the weld is ≥420MPa, the cover disc and the shaft disc are only quenched once;

[0008] Using welding rod to weld to obtain the impeller;

[0009] The impeller is subjected to stress relief treatment and performance heat treatment.

[0010] In the above technical solution, when the yield strength Re of the impeller material is required to be 515≤Re<700MPa, and the yield strength of the weld is ≥420MPa, the cover disc and the shaft disc are subjected to the first quenching treatment: the cover disc and the shaft disc are heated to 800-850°C and kept warm, and then taken out of the furnace and cooled;

[0011] And the second quenching treatment: heating the cover plate and the shaft plate to 670-700° C. and keeping the temperature, then taking them out of the furnace and cooling them with water.

[0012] In the above technical solution, the heating rate of the first quenching treatment is ≤100°C / h, and the holding time is ≥2.5h.

[0013] In the above technical solution, the heating rate of the second quenching treatment is ≤100°C / h, and the holding time is ≥3h.

[0014] In the above technical solution, when the yield strength of the impeller material is required to be ≥700MPa and the yield strength of the weld is ≥420MPa, the cover plate and the shaft plate are only subjected to one quenching treatment: the cover plate and the shaft plate are heated to 800-850°C and kept warm, and then taken out of the furnace and cooled.

[0015] In the above technical solution, the normalizing treatment includes heating the cover plate and the shaft plate to 890-920° C. and keeping the temperature, and then air cooling them after they are taken out of the furnace.

[0016] In the above technical solution, the tempering treatment includes heating the cover plate and the shaft plate to 530-610° C. and keeping the temperature, and then air cooling them after they are taken out of the furnace.

[0017] In the above technical solution, the welding rod is an austenitic welding material, such as E1Ni9, ENiCrMo-3, etc.

[0018] In the above technical solution, the effective thickness of the cover disc and the shaft disc are both ≤200 mm.

[0019] In the above technical solution, before welding the impeller, a simulated performance test is performed, including simulated stress relief treatment and simulated performance heat treatment. After the simulated performance test is qualified, the impeller is welded, subjected to stress relief treatment, and subjected to performance heat treatment. Since the large-flow impeller of this application includes the situation where the performance of the base material and the performance of the welding material are inconsistent, the process requirements are relatively strict. At present, in production, in order to ensure product quality, a simulated performance test will be added. After the test is qualified, the subsequent steps will be carried out.

[0020] The specific process of simulation performance testing includes:

[0021] Cut mechanical properties test circles from the cover disc and the shaft disc respectively, and weld two weld seam mechanical properties simulation test plates at the same time;

[0022] Conduct mechanical property testing: The mechanical property test rings of the cover plate and the shaft plate and the mechanical property simulation test plates of the welds after welding are subjected to simulated stress relief treatment and simulated performance heat treatment.

[0023] The traditional impeller manufacturing method is a narrow channel welded impeller, and the blades are mostly in the form of a binary structure, generally with slots on the outside of the shaft disc. After the impeller cover and shaft disc are assembled, Tig welding is performed at the slotted position on the outside of the shaft disc using TGS-9N welding consumables. Since the impeller material and the welding consumables are welded joints of the same material, the impeller can be tempered after welding. With the change in product requirements, ordinary binary structure narrow channel welded impellers can no longer meet the needs of all products. Impellers with large flow coefficients and three-dimensional twisted blades are gradually used in low-temperature medium compressors. The impeller with three-dimensional twisted blades is not suitable for welding with slots on the side of the shaft disc due to structural reasons, especially for large flow impellers with higher blades. Therefore, large flow impellers with three-dimensional twisted structures are usually welded using SMAW arc welding, which is not suitable for Tig welding. Therefore, TGS-9N welding consumables are not suitable for this type of impeller structure.

[0024] Compared with the prior art, the beneficial effects of this application are:

[0025] (1) This application solves the problem that large-flow impellers are difficult to temper, and improves the impeller heat treatment method according to the different requirements for the impeller material, and performs targeted heat treatment, welding and subsequent treatment on the material to improve the alloy structure morphology and improve the comprehensive performance of the impeller under low-temperature conditions. Specifically, when the yield strength Re of the impeller material is required to be 515≤Re<700MPa, and the yield strength of the weld is ≥420MPa, this application adopts the scheme of normalizing treatment, bicritical quenching and tempering treatment, which meets the production requirements, and the elongation, cross-sectional shrinkage and impact toughness of the parent material are all good, the impact toughness of the weld is relatively high, and the risk of weld cracking can also be reduced; when the yield strength of the impeller material is required to be ≥700MPa, and the yield strength of the weld is ≥420MPa, the heat treatment method of this application can meet the production requirements while the cross-sectional shrinkage and impact toughness of the parent material are good, and the impact toughness of the weld is relatively high.

[0026] (2) The present application is also applicable to situations where the performance of the impeller base material and the performance of the welding material are inconsistent. Normally, when the impeller material is martensitic steel and the welding material is austenite, precipitation phases are likely to appear at the weld position, reducing the toughness and corrosion resistance at the weld position. The present application performs tempering treatment before impeller welding and stress relief treatment and performance heat treatment including cold treatment after impeller welding. This can ensure that the strength of the impeller material is not reduced and the toughness of the welding material is ensured. At the same time, the stress relief and performance heat treatment after welding ensure the quality of the impeller weld. It is well suitable for impellers that require high strength of the base material but lower strength requirements of the weld. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the test circle position of the cover plate of Example 1.

[0028] Figure 2 Schematic diagram of the test circle position of the cover plate of Example 5. DETAILED DESCRIPTION

[0029] The technical scheme of the present application will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be appreciated by those skilled in the art that the following described embodiments are part of the present application embodiments, rather than all embodiments, and are only used to illustrate the present application, and should not be considered as limiting the scope of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative work, all belong to the scope of protection of the present application. Those who do not specify specific conditions in the embodiments are carried out according to normal conditions or conditions recommended by the manufacturer. Those who do not specify the manufacturer for the reagents or instruments used are all conventional products that can be purchased commercially.

[0030] A large flow impeller heat treatment method comprises the following steps:

[0031] (1) Heat treatment of the cover disc and the shaft disc before welding: normalizing, quenching and tempering of the cover disc and the shaft disc in sequence.

[0032] The normalizing treatment includes heating the cover plate and the shaft plate to 890-920°C and keeping them warm, and then air cooling them after they are taken out of the furnace.

[0033] The material of the impeller is martensitic steel, which may be 1Ni9 steel, ASTM A522 Type 1, ASTM A522 Type 2, etc., preferably 1Ni9 steel.

[0034] When the yield strength Re of the impeller material is required to be 515≤Re<700MPa, and the yield strength of the weld is ≥420MPa, the quenching treatment of the cover disc and the shaft disc in this application includes the first quenching treatment and the second quenching treatment, which can further improve the toughness of the parent material. The first quenching treatment: the cover disc and the shaft disc are charged into the furnace below 500°C, heated to 800-850°C for insulation, and then taken out of the furnace for cooling. The heating rate is ≤100°C / h, and the insulation time is ≥2.5h. The second quenching treatment: the cover disc and the shaft disc after the first quenching treatment are charged into the furnace below 500°C, heated to 670-700°C for insulation, and then taken out of the furnace for water cooling. The heating rate is ≤100°C / h, and the insulation time is ≥3h. After double critical quenching, it not only meets the production requirements, but also has good effects on the elongation, cross-sectional shrinkage and impact toughness of the parent material. The impact toughness of the weld is also improved, and the risk of weld cracking can also be reduced.

[0035] When the yield strength of the impeller material is required to be ≥700MPa and the yield strength of the weld is ≥420MPa, the cover plate and the shaft plate are only subjected to one quenching treatment: the cover plate and the shaft plate are loaded into the furnace below 500℃, heated to 800-850℃ at a heating rate of ≤100℃ / h and kept warm for not less than 2.5 hours, and then taken out of the furnace and cooled. The cooling method can be no less than oil cooling, that is, water-based quenching agent cooling, water cooling, alkaline water cooling, etc. can be used.

[0036] The tempering treatment includes heating the cover plate and the shaft plate to 530-610°C at a heating rate of ≤70°C / h, keeping the temperature, and air cooling after taking out of the furnace.

[0037] (2) Using austenitic welding materials for SMAW welding to obtain an impeller. Austenitic welding materials can be E1Ni9 welding rods, ENiCrMo-3 welding rods, etc., preferably E1Ni9 welding rods.

[0038] (3) Perform stress relief treatment and performance heat treatment on the impeller.

[0039] Stress relief treatment: Heat the impeller to 540-570℃ at a heating rate of ≤70℃ / h, keep it warm for not less than 4 hours, and then cool it down after removing it from the furnace.

[0040] Performance heat treatment includes cold treatment and final tempering.

[0041] Cold treatment: cool the impeller to -115 to -196°C at a rate of ≤2°C / min, keep warm for at least 2.5 hours, take out the impeller and naturally heat it to room temperature in the air;

[0042] Final tempering treatment: heat the impeller to 500-540℃ at a heating rate of ≤70℃ / h, keep it warm for not less than 5 hours, and cool it out of the furnace.

[0043] In this application, the effective thickness of the cover plate and the shaft plate is ≤200mm. The effective thickness refers to the maximum circle diameter that can be drawn in the cover plate and the shaft plate. If the raw material thickness exceeds 200mm, a step can be processed before heat treatment to make the effective thickness φ≤200mm.

[0044] Before welding the impeller, a simulated performance test is carried out, including simulated stress relief treatment and simulated performance heat treatment. After the simulated performance test is qualified, the impeller is welded, subjected to stress relief treatment, and subjected to performance heat treatment.

[0045] The specific process of simulation performance testing includes:

[0046] Cut mechanical properties test circles from the cover disc and the shaft disc respectively, and weld two weld mechanical properties simulation test plates (150*300*20mm) at the same time;

[0047] Conduct mechanical property testing: The mechanical property test rings of the cover plate and the shaft plate and the mechanical property simulation test plates of the welds after welding are subjected to simulated stress relief treatment and simulated performance heat treatment.

[0048] Among them, simulated stress relief treatment: the test ring and weld mechanical properties simulation test plate are heated to 500-570℃ for insulation, and then air-cooled after being taken out of the furnace;

[0049] Simulated cold treatment: the test ring and the weld mechanical properties simulation test plate are cooled to -115 to -196°C for insulation, and then naturally heated to room temperature in the air.

[0050] Simulated tempering treatment: the test ring and the weld mechanical properties simulation test plate are heated to 480-540°C for insulation, and then taken out of the furnace for air cooling.

[0051] Example 1

[0052] This embodiment requires that the yield strength Re of the impeller material is 515≤Re<700MPa, and the yield strength of the weld is ≥420MPa.

[0053] The effective thickness of the cover plate and the shaft plate made of 1Ni9 steel selected in this embodiment is 200 mm.

[0054] This embodiment provides a method for heat treatment of a high-flow impeller of a low-temperature compressor, comprising the following steps:

[0055] (1) Before welding, the cover plate, shaft plate and weld simulation mechanical properties test plate (size 150*300*20mm) customized in the same batch as the cover plate and shaft plate are heat treated: the above materials are subjected to normalizing treatment, quenching treatment and tempering treatment in sequence.

[0056] The normalizing treatment includes charging the above materials into a furnace at 230°C, heating them to 900°C at a heating rate of 80°C / h and keeping the temperature for 2h, and then air cooling them out of the furnace.

[0057] First quenching treatment: the above materials are charged into a furnace at 200℃, heated to 800℃ and kept warm, and then cooled with oil after being taken out of the furnace. The heating rate is 60℃ / h and the holding time is 2.5h. Second quenching treatment: the above materials after the first quenching treatment are charged into a furnace at 220℃, heated to 680℃ and kept warm, and then cooled with water after being taken out of the furnace. The heating rate is 85℃ / h and the holding time is 3h.

[0058] The tempering treatment includes charging the above materials into a furnace at 210°C, heating them to 590°C at a heating rate of 40°C / h, keeping the temperature for 5h, and then air cooling them after they are taken out of the furnace.

[0059] (2) Cut mechanical properties test rings from the cover plate and the shaft plate and test them. The test ring is located 10 mm below the end surface and 10 mm from the outer surface. Figure 1At the same time, two weld mechanical properties simulation test plates were welded using E1Ni9 welding rods, and the size after welding was 300*300*20mm.

[0060] The test ring and weld mechanical properties simulation test plate are simultaneously subjected to simulated stress relief, simulated performance heat treatment and mechanical properties testing. The specific procedures are as follows:

[0061] Simulated stress relief treatment: the test ring and weld mechanical properties simulation test plate are placed in a furnace at 200°C, heated to 560°C at a heating rate of 50°C / h, kept at this temperature for 4 hours, and then taken out of the furnace and air-cooled.

[0062] Simulated performance heat treatment includes simulated cold treatment and simulated tempering treatment.

[0063] Simulated cold treatment: cool the test ring and weld mechanical properties simulation test plate to -115℃ at a rate of 2℃ / min and keep it warm for 2.5 hours. Take out the test ring and weld mechanical properties simulation test plate and naturally heat it up to room temperature in the air.

[0064] Simulated tempering treatment: the test ring and weld mechanical properties simulation test plate are placed in a furnace at 220°C, heated to 520°C at a heating rate of 40°C / h, kept at this temperature for 5 hours, and then taken out of the furnace and air-cooled.

[0065] Mechanical properties testing: The test ring and weld mechanical properties simulation test plate were processed into mechanical properties specimens for mechanical properties testing, and the results are shown in Tables 1 to 3.

[0066] Table 1 Test results of mechanical properties of parent material

[0067]

[0068] Table 2 Weld tensile properties test results

[0069]

[0070] *According to ASME standard requirements, 2 tensile specimens are taken from the weld for testing.

[0071] Table 3 Weld impact toughness test results

[0072]

[0073] All tests meet the production requirements, and the elongation, cross-sectional shrinkage and impact toughness of the base material all have good results. The impact toughness of the weld in this application is relatively high, the weld quality is good, and no defects such as cracking are displayed.

[0074] (3) The cover plate and the shaft plate are SMAW welded using E1Ni9 welding rod to obtain an impeller.

[0075] (4) Perform stress relief treatment and performance heat treatment on the impeller.

[0076] Stress relief treatment: The impeller is placed in a furnace at 200°C, heated to 560°C at a heating rate of 50°C / h and kept at that temperature for 4 hours, then taken out of the furnace and air-cooled.

[0077] Performance heat treatment includes cold treatment and final tempering.

[0078] Cold treatment: cool the impeller to -115℃ at a rate of 2℃ / min and keep it warm for 2.5 hours. Take out the impeller and naturally heat it to room temperature in the air.

[0079] Final tempering treatment: The impeller is placed in a furnace at 220°C, heated to 520°C at a heating rate of 40°C / h and kept at that temperature for 5 hours, then removed from the furnace and air-cooled. The impeller heat treatment process is completed.

[0080] Example 2

[0081] The requirements and selected components of this embodiment are the same as those of Embodiment 1.

[0082] This embodiment provides a large flow impeller heat treatment method, comprising the following steps:

[0083] (1) Before welding, the cover plate, shaft plate and weld simulation mechanical property test plate (size 150*300*20mm) customized in the same batch as the cover plate and shaft plate are heat treated: the above materials are subjected to normalizing treatment, quenching treatment and tempering treatment in sequence. Normalizing treatment is the same as Example 1. First quenching treatment: the material is charged into a furnace at 200°C, heated to 850°C and kept warm, and then taken out of the furnace and oil-cooled. The heating rate is 100°C / h, and the holding time is 3h. Second quenching treatment: the material after the first quenching treatment is charged into a furnace at 220°C, heated to 690°C and kept warm, and then taken out of the furnace and water-cooled. The heating rate is 100°C / h, and the holding time is 3h. Tempering treatment is the same as Example 1.

[0084] Step (2) is the same as in Example 1. The mechanical properties test results are shown in Tables 4 to 6.

[0085] Table 4 Test results of mechanical properties of parent material

[0086]

[0087] Table 5 Weld tensile properties test results

[0088]

[0089] Table 6 Weld impact toughness test results

[0090]

[0091] All tests are in line with production requirements, and the elongation, cross-sectional shrinkage and impact toughness of the base material have good results. The impact toughness of the weld is relatively high, the weld quality is good, and no defects such as cracks are shown.

[0092] Step (3) and step (4) are the same as in Example 1.

[0093] Example 3

[0094] The requirements and selected components of this embodiment are the same as those of Embodiment 1.

[0095] This embodiment provides a large flow impeller heat treatment method, comprising the following steps:

[0096] (1) Before welding, the cover plate, shaft plate and weld simulation mechanical property test plate (size 150*300*20mm) customized in the same batch as the cover plate and shaft plate are heat treated: the above materials are subjected to normalizing treatment, quenching treatment and tempering treatment in sequence. Normalizing treatment and the first quenching treatment are the same as in Example 1. Second quenching treatment: the material after the first quenching treatment is charged into a furnace at 220°C, heated to 750°C and kept warm, and then taken out of the furnace and water-cooled. The heating rate is 100°C / h and the holding time is 3h. Tempering treatment is the same as in Example 1.

[0097] Step (2) is the same as in Example 1. The mechanical properties test results are shown in Tables 7 to 9.

[0098] Table 7 Test results of mechanical properties of parent material

[0099]

[0100] Table 8 Weld tensile properties test results

[0101]

[0102] Table 9 Weld impact toughness test results

[0103]

[0104] All tests meet the production requirements, and the base material has good tensile strength and yield strength, and its plasticity and toughness are lower than those of Example 1 and Example 2. The weld quality is intact, and no cracking is shown.

[0105] Step (3) and step (4) are the same as in Example 1.

[0106] Example 4

[0107] The requirements and selected components of this embodiment are the same as those of Embodiment 1.

[0108] This embodiment provides a large flow impeller heat treatment method, comprising the following steps:

[0109] (1) Before welding, the cover plate, shaft plate and weld simulation mechanical properties test plate (size 150*300*20mm) customized in the same batch as the cover plate and shaft plate are heat treated: the above materials are subjected to normalizing treatment, quenching treatment and tempering treatment in sequence.

[0110] The normalizing treatment includes charging the above materials into a furnace at 230°C, heating them to 940°C at a heating rate of 100°C / h, keeping the temperature for 2h, and then air cooling them after they are taken out of the furnace.

[0111] First quenching treatment: the above materials are charged into the furnace at 200℃, heated to 770℃ and kept warm, and then cooled with oil after being taken out of the furnace. The heating rate is 100℃ / h and the holding time is 2.5h. Second quenching treatment: the above materials after the first quenching treatment are charged into the furnace at 220℃, heated to 650℃ and kept warm, and then cooled with water after being taken out of the furnace. The heating rate is 100℃ / h and the holding time is 3h.

[0112] The tempering treatment includes charging the above materials into a furnace at 210°C, heating them to 610°C at a heating rate of 70°C / h, keeping the temperature for 5h, and then air cooling them after they are taken out of the furnace.

[0113] Step (2) is the same as in Example 1. The mechanical properties test results are shown in Tables 10 to 12.

[0114] Table 10 Test results of mechanical properties of parent material

[0115]

[0116] Table 11 Weld tensile properties test results

[0117]

[0118] Table 12 Weld impact toughness test results

[0119]

[0120] All tests meet production requirements, and the plasticity and toughness of the base material have good results, and the yield strength is only slightly higher than the required value of 515MPa. The impact toughness of the weld is high, the yield strength is close to 420MPa, the welding quality is intact, and there is no cracking.

[0121] Step (3) and step (4) are the same as in Example 1.

[0122] Example 5

[0123] This embodiment requires that the yield strength of the impeller material is ≥700 MPa, and the yield strength of the weld is ≥420 MPa.

[0124] The effective thickness of the cover plate and the shaft plate made of 1Ni9 steel selected in this embodiment is 200 mm.

[0125] This embodiment provides a large flow impeller heat treatment method, comprising the following steps:

[0126] (1) Before welding, the cover plate, shaft plate and weld simulation mechanical properties test plate (size 150*300*20mm) customized in the same batch as the cover plate and shaft plate are heat treated: the above materials are subjected to normalizing treatment, quenching treatment and tempering treatment in sequence.

[0127] The normalizing treatment includes charging the above materials into a furnace at 300°C, heating them to 910°C at a heating rate of 70°C / h, keeping the temperature for 2.5h, and then air cooling them after they are taken out of the furnace.

[0128] Quenching treatment: the above materials are placed in a furnace at 240℃, heated to 810℃ and kept warm, and then cooled with water after being taken out of the furnace. The heating rate is 60℃ / h and the holding time is 3h.

[0129] The tempering treatment includes charging the above materials into a furnace at 210°C, heating them to 560°C at a heating rate of 30°C / h, keeping the temperature for 3h, and then cooling them in air after they are taken out of the furnace.

[0130] (2) Cut mechanical properties test circles from the cover disc and the shaft disc and test them. Figure 2 At the same time, two weld mechanical properties simulation test plates were welded using E1Ni9 welding rods, and the size after welding was 300*300*20mm.

[0131] The test ring and weld mechanical properties simulation test plate are simultaneously subjected to simulated stress relief, simulated performance heat treatment and mechanical properties testing. The specific procedures are as follows:

[0132] Simulated stress relief treatment: the test ring and weld mechanical properties simulation test plate were placed in a furnace at 230°C, heated to 530°C at a heating rate of 40°C / h, kept warm for 5 hours, and then taken out of the furnace and air-cooled.

[0133] Simulated performance heat treatment includes simulated cold treatment and simulated tempering treatment.

[0134] Simulated cold treatment: cool the test ring and weld mechanical properties simulation test plate to -196℃ at a rate of 1℃ / min and keep it warm for 3 hours. Take out the test ring and weld mechanical properties simulation test plate and naturally heat it to room temperature in the air.

[0135] Simulated tempering treatment: the test ring and weld mechanical properties simulation test plate were placed in a furnace at 240°C, heated to 500°C at a heating rate of 35°C / h, kept at that temperature for 6 hours, and then taken out of the furnace and air-cooled.

[0136] Mechanical properties testing: The test ring and weld mechanical properties simulation test plate were processed into mechanical properties specimens for mechanical properties testing. The results are shown in Tables 13 to 15.

[0137] Table 13 Test results of mechanical properties of parent material

[0138]

[0139] Table 14 Weld tensile properties test results

[0140]

[0141] Table 15 Weld impact toughness test results

[0142]

[0143] All tests meet the production requirements, and the base material has good tensile strength, cross-sectional shrinkage and impact toughness. The impact toughness of the weld in this application is relatively high, the weld quality is good, and no defects such as cracking are shown.

[0144] (3) The cover plate and the shaft plate are SMAW welded using E1Ni9 welding rod to obtain an impeller.

[0145] (4) Perform stress relief treatment and performance heat treatment on the impeller.

[0146] Stress relief treatment: The impeller is placed in a furnace at 200°C, heated to 530°C at a heating rate of 70°C / h and kept at that temperature for 4 hours, then taken out of the furnace and air-cooled.

[0147] Performance heat treatment includes cold treatment and final tempering.

[0148] Cold treatment: cool the impeller to -196℃ at a rate of 2℃ / min and keep it warm for 2.5 hours. Take out the impeller and naturally heat it to room temperature in the air.

[0149] Final tempering treatment: The impeller is placed in a furnace at 220°C, heated to 500°C at a heating rate of 70°C / h and kept at that temperature for 5 hours, then removed from the furnace and air-cooled. The impeller heat treatment process is completed.

[0150] Example 6

[0151] The requirements and selected components of this embodiment are the same as those of Embodiment 5.

[0152] This embodiment provides a large flow impeller heat treatment method, comprising the following steps:

[0153] (1) Before welding, the cover plate, shaft plate and weld seam simulation mechanical properties test plate (size 150*300*20mm) customized in the same batch as the cover plate and shaft plate are heat treated: the above materials are subjected to normalizing treatment, quenching treatment and tempering treatment in sequence. Normalizing treatment is the same as in Example 5. Quenching treatment: the above materials are charged into a furnace at 240°C, heated to 850°C and kept warm, and then taken out of the furnace and water-cooled. The heating rate is 100°C / h and the holding time is 2.5h. Tempering treatment is the same as in Example 5.

[0154] Step (2) is the same as in Example 5. The mechanical properties test results are shown in Tables 16 to 18.

[0155] Table 16 Test results of mechanical properties of parent material

[0156]

[0157] Table 17 Weld tensile properties test results

[0158]

[0159] Table 18 Weld impact toughness test results

[0160]

[0161] All tests meet the production requirements, and the parent material strength and plasticity have good results, the weld impact toughness is relatively high, and the heat affected zone impact toughness is lower than that of Example 5. The weld quality is intact, and no cracking is shown.

[0162] Step (3) and step (4) are the same as in Example 5.

[0163] Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein, and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A heat treatment method for a large flow impeller, characterized in that: The steps include: The cover plate and the shaft plate are heat treated before welding: the cover plate and the shaft plate are subjected to normalizing treatment, quenching treatment and tempering treatment in sequence. Wherein, the material of the impeller is martensitic steel, and when the yield strength Re of the impeller material is required to be 515≤Re<700MPa, and the yield strength of the weld is ≥420MPa, the quenching treatment performed on the cover disc and the shaft disc includes a first quenching treatment and a second quenching treatment, and the heating temperature of the second quenching treatment is lower than the heating temperature of the first quenching treatment; when the yield strength of the impeller material is required to be ≥700MPa, and the yield strength of the weld is ≥420MPa, the cover disc and the shaft disc are only quenched once; Using welding rod to weld to obtain the impeller; The impeller is subjected to stress relief treatment and performance heat treatment.

2. A large flow impeller heat treatment method according to claim 1, characterized in that: When the yield strength Re of the impeller material is required to be 515≤Re<700MPa, and the yield strength of the weld is ≥420MPa, the cover disc and the shaft disc are subjected to the first quenching treatment: the cover disc and the shaft disc are heated to 800-850°C and kept warm, and then taken out of the furnace and cooled; And the second quenching treatment: heating the cover plate and the shaft plate to 670-700° C. and keeping the temperature, then taking them out of the furnace and cooling them with water.

3. A large flow impeller heat treatment method according to claim 2, characterized in that: The heating rate of the first quenching treatment is ≤100°C / h, and the holding time is ≥2.5h.

4. A large flow impeller heat treatment method according to claim 2, characterized in that: The heating rate of the second quenching treatment is ≤100°C / h, and the holding time is ≥3h.

5. A large flow impeller heat treatment method according to claim 1, characterized in that: When the yield strength of the impeller material is required to be ≥700MPa and the yield strength of the weld is ≥420MPa, the cover disc and the shaft disc are subjected to only one quenching treatment: the cover disc and the shaft disc are heated to 800-850°C and kept warm, and then taken out of the furnace and cooled.

6. A large flow impeller heat treatment method according to claim 1, characterized in that: The normalizing treatment includes heating the cover plate and the shaft plate to 890-920° C., keeping the temperature, and air cooling after taking out of the furnace.

7. A large flow impeller heat treatment method according to claim 1, characterized in that: The tempering treatment includes heating the cover plate and the shaft plate to 530-610° C. and keeping the temperature, and then taking the plate out of the furnace and air cooling the plate.

8. A large flow impeller heat treatment method according to claim 1, characterized in that: The welding rod is an austenitic welding material.

9. A large flow impeller heat treatment method according to claim 1, characterized in that: The effective thickness of the cover disc and the shaft disc is ≤200 mm.

10. A heat treatment method for a large flow impeller according to any one of claims 1 to 9, characterized in that: Before welding the impeller, a simulated performance test is performed, including a simulated stress relief treatment and a simulated performance heat treatment. After the simulated performance test is qualified, the impeller is welded, subjected to stress relief treatment, and subjected to performance heat treatment.

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