Heat treatment method of 9-12% Cr martensite heat-resistant steel forge piece
Through a new heat treatment method, including quenching treatment, two tempering and furnace cooling, the problem of the yield strength and residual stress of 9-12% Cr martensite heat-resistant steel forgings not meeting the standards after heat treatment, achieving a comprehensive effect of high strength, low residual stress and high impact toughness.
Patent Information
- Application Number
- CN202411936772.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-26
- Publication Date
- 2025-04-04
AI Technical Summary
After heat treatment, existing 9-12% Cr martensite heat-resistant steel forgings often have problems such as failure to meet the surface yield strength, failure to meet the standard of surface residual stress, or both, making it difficult to achieve stable engineering manufacturing.
A new heat treatment method is adopted, including quenching treatment, two tempering treatments and furnace cooling. The specific steps are: first perform quenching treatment, then perform the first tempering and air cooling, then perform the second tempering, and control the cooling rate and insulation time, and finally perform the furnace cooling to reduce residual stress.
Through this heat treatment method, the yield strength of the forging reaches no less than 800MPa, the impact force of the room temperature is not less than 15J, the tough brittle transition temperature does not exceed 60℃, and the low residual stress is in the range of -80-20MPa, which meets the requirements of improving impact toughness while high strength and low residual stress.
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Figure CN119753281A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of heat treatment, in particular to a heat treatment method for a 9-12% Cr martensitic heat-resistant steel forging. Background Art
[0002] A heavy-duty gas turbine is a high-speed rotating impeller machine that converts the chemical energy of fuel and the kinetic energy of fluid into power through four thermodynamic processes: compression, heating, expansion, and heat release. It is the core power equipment of the 21st century's energy efficient conversion and clean utilization system. It has strict technical parameters and is difficult to manufacture, and is known as the "crown jewel" of the equipment manufacturing industry.
[0003] The rotor body of a heavy-duty gas turbine mainly consists of two parts: the compressor wheel and the turbine wheel. For high-power and high-parameter heavy-duty gas turbines, the turbine wheel forgings are generally made of 9-12% Cr martensitic heat-resistant steel materials due to the greatly increased turbine inlet temperature. Due to the special working environment, the 9-12% Cr martensitic heat-resistant steel turbine wheel is required to have high strength (yield strength not less than 800MPa), moderate toughness (room temperature impact energy not less than 15J, ductile-brittle transition temperature not exceeding 60°C), and low residual stress (-80~20MPa), and the manufacturing process control is difficult. At present, the turbine wheel forgings made of 9-12% Cr martensitic heat-resistant steel materials are manufactured according to the mature heat treatment method of heat-resistant steel materials (see Figure 1 ) During engineering manufacturing, after tempering, the surface yield strength often fails to meet the standard, the surface residual stress also fails to meet the standard, or the surface yield strength meets the standard, but the surface residual stress fails to meet the standard, making it difficult to achieve stable engineering manufacturing. With the advancement of the development of high-power, high-parameter heavy-duty gas turbines, it is urgent to develop new heat treatment methods to break through the manufacturing difficulties of 9-12% Cr steel forgings with high strength and low residual stress. Summary of the invention
[0004] The technical problem to be solved by the present invention is to provide a heat treatment method for 9-12% Cr martensitic heat-resistant steel forgings, which can make the yield strength of the forgings not less than 800MPa, the impact energy at room temperature not less than 15J, the ductile-brittle transition temperature not more than 60°C and the low residual stress between -80 and 20MPa.
[0005] The technical solution adopted by the present invention to solve the technical problem is: a heat treatment method for a 9-12% Cr martensitic heat-resistant steel forging, comprising the following steps:
[0006] Step 1, quenching treatment: after the forging is loaded into the furnace, the temperature is raised from room temperature to 1050-1110°C at a heating rate not exceeding 50°C / h and kept at this temperature for t1 hour, t1≥1.5B / 100, and then the forging is immersed in oil for oil cooling until the temperature is ≤150°C, where B is the effective thickness of the forging;
[0007] Step 2, first tempering: heating the forging to 550-580°C at a heating rate not exceeding 50°C / h and keeping the temperature for t2 hours, t2≥1.5B / 100, and then air cooling until the temperature is ≤150°C;
[0008] Step 3, second tempering: the forging is heated to 620-660°C at a heating rate not exceeding 50°C / h and kept for t3 hours, t3≥1.5B / 100+2, then cooled to 500-600°C at a cooling rate not exceeding 20°C / h and kept for t4 hours, t4≥1.5B / 100+4, then air-cooled to a temperature of 350-410°C and kept for t5 hours, t5≥1.5B / 100, then cooled to a temperature of ≤250°C at a cooling rate not exceeding 20°C / h, and finally air-cooled to room temperature.
[0009] Furthermore, the forging is cooled by furnace cooling at a temperature reduction rate not exceeding 20° C. / h.
[0010] Furthermore, the forging is a disc-shaped structure.
[0011] Furthermore, the forging is provided with a center hole. During oil cooling, the forging is suspended upright and immersed in oil for oil cooling through a pin shaft passing through the center hole of the forging, and the forging is moved along the axial direction of the pin shaft during oil cooling. The diameter of the pin shaft is φ2, φ2<φ1-50, and φ1 is the diameter of the center hole of the forging.
[0012] Furthermore, when heating, the forging is heated by being placed upright in a heating furnace.
[0013] Furthermore, the room temperature is 10-35°C.
[0014] Furthermore, the material composition of the forging is, in terms of weight percentage, C: 0.18-0.21wt%, Si≤0.12wt%, Mn: 0.10-0.30wt%, P≤0.012wt%, S≤0.007wt%, Cr: 8.95-9.50wt%, Ni: 0.25-0.45wt%, Mo: 1.40-1.60wt%, V: 0.27-0.40wt%, Co: 1.08~1.32wt%, Cu≤0.10wt%, Al≤0.012wt%, Nb: 0.04~0.06wt%, B: 0.004~0.007wt%, N: 0.020~0.045wt%, As≤0.010wt%, Sn≤0.010wt%, Sb≤0.010wt%, H≤0.00015wt%, O≤0.0035wt%, and the balance is iron.
[0015] The beneficial effects of the present invention are as follows: the heat treatment method of the 9-12% Cr martensitic heat-resistant steel forging of the present invention firstly improves the quenching cooling strength of the forging by oil cooling, laying a foundation for the forging to obtain high-strength performance, and then changes the tempering process. The changed two tempering processes effectively reduce the residual stress of the forging, improve the impact toughness, so that the yield strength is not less than 800MPa, the room temperature impact energy is not less than 15J, the ductile-brittle transition temperature does not exceed 60°C, and the low residual stress is -80 to 20MPa. The use requirements improve the mechanical properties of the 9-12% Cr martensitic heat-resistant steel forging. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 This is the heat treatment process diagram of the existing 9-12% Cr martensitic heat-resistant steel material;
[0017] Figure 2 It is the heat treatment process diagram of the present invention:
[0018] Figure 3 It is a schematic diagram of oil cooling of forgings;
[0019] Shown in the figure: forging 1, pin 2. DETAILED DESCRIPTION
[0020] The present invention is further described below in conjunction with the accompanying drawings and embodiments.
[0021] like Figure 2 As shown, a heat treatment method of a 9-12% Cr martensitic heat-resistant steel forging of the present invention comprises the following steps:
[0022] Step 1, quenching treatment: after the forging is loaded into the furnace, it is heated from room temperature to 1050-1110°C at a heating rate not exceeding 50°C / h and kept warm for t1 hours, t1≥1.5B / 100, to ensure that the material is completely austenitic and homogenized, and the carbides and nitrides are fully dissolved back, and then the forging is immersed in oil and oil-cooled until its temperature is ≤150°C, where B is the effective thickness of the forging, in mm;
[0023] Step 2, first tempering: heating the forging to 550-580°C at a heating rate not exceeding 50°C / h and keeping the temperature for t2 hours, t2≥1.5B / 100, so as to eliminate the martensite formed during quenching, and then air-cooling until its temperature is ≤150°C;
[0024] Step 3, second tempering: the forging is heated to 620-660°C at a heating rate not exceeding 50°C / h and kept for t3 hours, t3≥1.5B / 100+2, then cooled to 500-600°C at a cooling rate not exceeding 20°C / h and kept for t4 hours, t4≥1.5B / 100+4, then air-cooled to a temperature of 350-410°C and kept for t5 hours, t5≥1.5B / 100, then cooled to a temperature of ≤250°C at a cooling rate not exceeding 20°C / h, and finally air-cooled to room temperature.
[0025] Specifically, the present invention adopts furnace cooling to cool the forging at a temperature reduction rate not exceeding 20° C. / h.
[0026] The room temperature in the present invention is 10-35°C.
[0027] The heat treatment method of the 9-12% Cr martensitic heat-resistant steel forging of the present invention first improves the quenching cooling strength of the forging by oil cooling, laying a foundation for the forging to obtain high-strength performance, and then changes the tempering process. The changed two tempering processes effectively reduce the residual stress of the forging and improve the impact toughness, so that the yield strength is not less than 800MPa, the room temperature impact energy is not less than 15J, the ductile-brittle transition temperature does not exceed 60°C, and the low residual stress is -80-20MPa. Specifically, the second tempering temperature of the forging is controlled at 620-660℃ and kept for t3 time, and then cooled to 500-600℃ at a cooling rate not exceeding 20℃ / h and kept for t4 time, ensuring the high strength of the forging while reducing the residual stress of the forging; the forging is kept at 500-600℃ for t4 time and then air-cooled to a temperature range of 350-410℃, effectively controlling the thermal stress of the forging while improving the impact toughness; the forging is air-cooled to a temperature range of 350-410℃ and kept, then cooled to a temperature ≤250℃ at a cooling rate not exceeding 20℃ / h and then air-cooled to further reduce the residual stress of the forging.
[0028] The forging can be of various shapes and structures. In the embodiment of the present invention, the forging is a disc-shaped structure. When the forging is a disc-shaped structure, the forging can be immersed in the oil in various ways. Figure 3As shown, in the embodiment of the present invention, when the forging is oil-cooled, the forging is suspended upright and immersed in oil by the pin 2 inserted in the center hole of the forging 1 for oil cooling, and the forging is moved along the axial direction of the pin 2 during oil cooling, and the diameter of the pin 2 is φ2, φ2<φ1-50, φ1 is the diameter of the center hole of the forging 1. The diameter of the pin 2 is φ2, φ2<φ1-50, which can reduce the contact area between the pin and the center hole of the forging, which is beneficial to uniform cooling of the forging. The present invention uses the pin to immerse the forging upright in oil for oil cooling, and moves the forging along the axial direction of the pin 2 during oil cooling, so that the forging is more fully in contact with the oil, the cooling speed of the forging is faster, and the cooling of various parts of the forging can be more uniform, which is beneficial to ensure the high performance of the forging.
[0029] In order to ensure that the forgings are heated more evenly, the forgings are preferably placed upright in a heating furnace for heating.
[0030] The 9-12% Cr martensitic heat-resistant steel in this application includes 10Cr9MO1VNbN, 10C9MOW2VNbBN, 11Cr9MO1WIVNbBN, 10Cr11MoW2VNbCu1BN and other steels that comply with GB5310, and also includes T / P91, T / P92, T / P911, T / P122 steels that comply with ASME regulations.
[0031] Example:
[0032] Example 1: The forging is disc-shaped, with a diameter of 2167 mm, a center hole diameter of 205 mm, an effective thickness of the forging of 390 mm, and the material composition includes: C: 0.18-0.21wt%, Si≤0.12wt%, Mn: 0.10-0.30wt%, P≤0.012wt%, S≤0.007wt%, Cr: 8.95-9.50wt%, Ni: 0.25-0.45wt%, Mo: 1.40-1.60wt%, V: 0.27~0.40wt%, Co: 1.08~1.32wt%, Cu≤0.10wt%, Al≤0.012wt%, Nb: 0.04~0.06wt%, B: 0.004~0.007wt%, N: 0.020~0.045wt%, As≤0.010wt%, Sn≤0.010wt%, Sb≤0.010wt%, H≤0.00015wt%, O≤0.0035wt%, and the balance is iron.
[0033] The heat treatment steps of forgings are:
[0034] Step 1: Quenching treatment: After the forging is completed, the temperature is raised from room temperature to 1050°C at a heating rate of 10°C / h and kept warm for 5.85h, and then the forging is immersed in oil and cooled until its temperature reaches 150°C;
[0035] Step 2, first tempering: heating the forging to 550°C at a heating rate of 10°C / h and keeping the temperature for 5.85h, and then air cooling until the temperature reaches 150°C;
[0036] Step 3, second tempering: the forging is heated to 620°C at a heating rate of 10°C / h and kept warm for 7.85h, then cooled to 600°C at a cooling rate of 5°C / h and kept warm for 9.85h, then air-cooled to 410°C and kept warm for 5.85h, then cooled to 250°C at a cooling rate of 5°C / h, and finally air-cooled to room temperature.
[0037] Embodiment 2: The forging is disc-shaped, with a diameter of 2159 mm, a center hole diameter of 215 mm, an effective thickness of the forging of 396 mm, and the material composition comprises: C: 0.18-0.21wt%, Si≤0.12wt%, Mn: 0.10-0.30wt%, P≤0.012wt%, S≤0.007wt%, Cr: 8.95-9.50wt%, Ni: 0.25-0.45wt%, Mo: 1.40-1.60wt%, V: 0.27~0.40wt%, Co: 1.08~1.32wt%, Cu≤0.10wt%, Al≤0.012wt%, Nb: 0.04~0.06wt%, B: 0.004~0.007wt%, N: 0.020~0.045wt%, As≤0.010wt%, Sn≤0.010wt%, Sb≤0.010wt%, H≤0.00015wt%, O≤0.0035wt%, and the balance is iron.
[0038] The heat treatment steps of forgings are:
[0039] Step 1: Quenching treatment: After the forging is completed, the temperature is raised from room temperature to 1070°C at a heating rate of 30°C / h and kept warm for 6.5 hours, and then the forging is immersed in oil and cooled until its temperature reaches 130°C;
[0040] Step 2, first tempering: heating the forging to 570°C at a heating rate of 30°C / h and keeping the temperature for 6.5h, and then air cooling until the temperature reaches 130°C;
[0041] Step 3, second tempering: the forging is heated to 640°C at a heating rate of 30°C / h and kept warm for 8.5h, then cooled to 550°C at a cooling rate of 15°C / h and kept warm for 10.5h, then air-cooled to 380°C and kept warm for 7h, then cooled to 200°C at a cooling rate of 15°C / h, and finally air-cooled to room temperature.
[0042] Embodiment 3: The forging is disc-shaped, with a diameter of 2151 mm, a center hole diameter of 220 mm, an effective thickness of the forging of 394 mm, and the material composition comprises: C: 0.18-0.21wt%, Si≤0.12wt%, Mn: 0.10-0.30wt%, P≤0.012wt%, S≤0.007wt%, Cr: 8.95-9.50wt%, Ni: 0.25-0.45wt%, Mo: 1.40-1.60wt%, V: 0.27~0.40wt%, Co: 1.08~1.32wt%, Cu≤0.10wt%, Al≤0.012wt%, Nb: 0.04~0.06wt%, B: 0.004~0.007wt%, N: 0.020~0.045wt%, As≤0.010wt%, Sn≤0.010wt%, Sb≤0.010wt%, H≤0.00015wt%, O≤0.0035wt%, and the balance is iron.
[0043] The heat treatment steps of forgings are:
[0044] Step 1: Quenching treatment: After the forging is completed, the temperature is raised from room temperature to 1100°C at a heating rate of 50°C / h and kept warm for 7.5 hours, and then the forging is immersed in oil and cooled until its temperature reaches 100°C;
[0045] Step 2, first tempering: heating the forging to 580°C at a heating rate of 50°C / h and keeping the temperature for 7.5h, and then air cooling until the temperature reaches 100°C;
[0046] Step 3, second tempering: the forging is heated to 660°C at a heating rate of 50°C / h and kept warm for 8 hours, then cooled to 500°C at a cooling rate of 20°C / h and kept warm for 10 hours, then air-cooled to 350°C and kept warm for 8 hours, then cooled to 150°C at a cooling rate of 20°C / h, and finally air-cooled to room temperature.
[0047] The forgings of Examples 1 to 3 were sampled and tested. The sampling points of each forging were the same, and a test ring was taken from the outer circle and the inner hole of the forging. The specific yield strength, room temperature impact energy and ductile-brittle transition temperature test results of each forging are shown in Table 1.
[0048] Table 1: Test results of forging yield strength, room temperature impact energy and ductile-brittle transition temperature
[0049]
[0050] Residual stress detection was performed on the 1 / 2 radius position of the end faces of the forgings of Examples 1 to 3 at intervals of 120° in the circumferential direction. The detection results are shown in Table 2.
[0051] Table 2: Residual stress test results
[0052]
[0053]
[0054] From the above test results, it can be seen that the method of the present invention makes the yield strength of 9-12%Cr martensitic heat-resistant steel forgings not less than 800MPa, the room temperature impact energy not less than 15J, the ductile-brittle transition temperature not more than 60°C and the low residual stress between -80 and 20MPa, which meets the requirements.
Claims
1. A heat treatment method for 9-12% Cr martensitic heat-resistant steel forgings, characterized in that: The following steps are involved: Step 1, quenching treatment: after the forging is loaded into the furnace, the temperature is raised from room temperature to 1050-1110°C at a heating rate not exceeding 50°C / h and kept at this temperature for t1 hour, t1≥1.5B / 100, and then the forging is immersed in oil for oil cooling until the temperature is ≤150°C, where B is the effective thickness of the forging; Step 2, first tempering: heating the forging to 550-580°C at a heating rate not exceeding 50°C / h and keeping the temperature for t2 hours, t2≥1.5B / 100, and then air cooling until the temperature is ≤150°C; Step 3, second tempering: the forging is heated to 620-660°C at a heating rate not exceeding 50°C / h and kept for t3 hours, t3≥1.5B / 100+2, then cooled to 500-600°C at a cooling rate not exceeding 20°C / h and kept for t4 hours, t4≥1.5B / 100+4, then air-cooled to a temperature of 350-410°C and kept for t5 hours, t5≥1.5B / 100, then cooled to a temperature of ≤250°C at a cooling rate not exceeding 20°C / h, and finally air-cooled to room temperature.
2. A heat treatment method for a 9-12% Cr martensitic heat-resistant steel forging according to claim 1, characterized in that: The forgings are cooled by furnace cooling at a temperature drop rate not exceeding 20°C / h.
3. A heat treatment method for a 9-12% Cr martensitic heat-resistant steel forging according to claim 1, characterized in that: The forging is a disc-shaped structure.
4. A heat treatment method for a 9-12% Cr martensitic heat-resistant steel forging according to claim 3, characterized in that: The forging is provided with a center hole. During oil cooling, the forging is suspended upright and immersed in oil through a pin shaft inserted in the center hole of the forging for oil cooling. During oil cooling, the forging is moved along the axis direction of the pin shaft. The diameter of the pin shaft (2) is φ2, φ2<φ1-50, and φ1 is the diameter of the center hole of the forging.
5. A heat treatment method for a 9-12% Cr martensitic heat-resistant steel forging according to claim 3, characterized in that: When heating, the forging is heated by being placed upright in a heating furnace.
6. A heat treatment method for a 9-12% Cr martensitic heat-resistant steel forging according to claim 1, characterized in that: The room temperature is 10-35°C.
7. A heat treatment method for a 9-12% Cr martensitic heat-resistant steel forging according to claim 1, characterized in that: The material composition of the forging is, in terms of weight percentage, C: 0.18-0.21wt%, Si≤0.12wt%, Mn: 0.10-0.30wt%, P≤0.012wt%, S≤0.007wt%, Cr: 8.95-9.50wt%, Ni: 0.25-0.45wt%, Mo: 1.40-1.60wt%, V: 0.27-0.40wt%, Co : 1.08~1.32wt%, Cu≤0.10wt%, Al≤0.012wt%, Nb: 0.04~0.06wt%, B: 0.004~0.007wt%, N: 0.020~0.045wt%, As≤0.010wt%, Sn≤0.010wt%, Sb≤0.010wt%, H≤0.00015wt%, O≤0.0035wt%, and the balance is iron.