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Heat treatment method for strength of 28CrMoNiV steel capable of improving industrial steam turbine rotor forge piece

A heat treatment method and technology of industrial steam turbines, applied in the field of production of industrial steam turbine steel forgings, can solve problems such as insufficient strength and unsatisfactory use, and achieve the effect of reducing residual stress

Inactive Publication Date: 2015-09-30
HANGZHOU TURBINE POWER GRP +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

After heat treatment of 28CrMoNiV steel forging products according to the conventional process, the toughness can be guaranteed, but the strength is not enough to meet the requirements of the application.

Method used

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  • Heat treatment method for strength of 28CrMoNiV steel capable of improving industrial steam turbine rotor forge piece
  • Heat treatment method for strength of 28CrMoNiV steel capable of improving industrial steam turbine rotor forge piece
  • Heat treatment method for strength of 28CrMoNiV steel capable of improving industrial steam turbine rotor forge piece

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0018] Embodiment 1: as figure 1 As shown, the heat treatment method described in this example to improve the strength of 28CrMoNiV steel for industrial steam turbine rotor forgings uses a shaft diameter of 400 mm, a chemical composition of C: 0.25-0.30%, Si: ≤0.30%, Mn: 0.30-0.80%, P: ≤0.012%, S: ≤0.012%, Cr: 1.10~1.40%, Ni: 0.50~0.75%, Mo: 0.80~1.00%, V0.25~0.35%, Cu: ≤0.20%, Al: ≤0.01 %, the rest is Fe; the steel type is a forging of 28CrMoNiV. The heat treatment process is carried out by normalizing + tempering + quenching and tempering, such as figure 2 As shown, normalize first, and preheat for 10 hours at a preheating temperature of 250-320°C. Normalizing heating adopts a staged heating method, and the first stage is from 250-320°C to no more than 60°C / h Heating to a temperature of 700-750°C, holding for 3 hours after reaching the temperature, heating to 900-920°C in the second stage, holding time for 8 hours, and air-cooling to 320-380°C when out of the furnace; At...

Embodiment 2

[0019] Example 2: The heat treatment method described in this example to improve the strength of 28CrMoNiV steel for industrial steam turbine rotor forgings, the shaft diameter is 500mm, the chemical composition is C: 0.25-0.30%, Si: ≤0.30%, Mn: 0.30-0.80% , P: ≤0.012%, S: ≤0.012%, Cr: 1.10~1.40%, Ni: 0.50~0.75%, Mo: 0.80~1.00%, V0.25~0.35%, Cu: ≤0.20%, Al: ≤ 0.01%, the rest is Fe; the steel type is 28CrMoNiV forgings. The heat treatment process is carried out by normalizing + tempering + quenching and tempering, such as figure 2 As shown, normalize first, and preheat for 10 hours at a preheating temperature of 250-320°C. Normalizing heating adopts a staged heating method, and the first stage is from 250-320°C to no more than 60°C / h Heating to a temperature of 700-750°C, and keeping it warm for 3 hours after reaching the temperature, the second stage is rapidly heated to 900-920°C, the holding time is 10 hours, and air-cooled to 320-380°C after being out of the furnace; At ...

Embodiment 3

[0020] Example 3: The heat treatment method described in this example to improve the strength of 28CrMoNiV steel for industrial steam turbine rotor forgings uses a shaft diameter of 600 mm and a chemical composition of C: 0.25-0.30%, Si: ≤0.30%, Mn: 0.30-0.80% , P: ≤0.012%, S: ≤0.012%, Cr: 1.10~1.40%, Ni: 0.50~0.75%, Mo: 0.80~1.00%, V0.25~0.35%, Cu: ≤0.20%, Al: ≤ 0.01%, the rest is Fe; the steel type is 28CrMoNiV forgings. The heat treatment process is carried out by normalizing + tempering + quenching and tempering, such as figure 2As shown, normalize first, and preheat for 10 hours at a preheating temperature of 250-320°C. Normalizing heating adopts a staged heating method, and the first stage is from 250-320°C to no more than 60°C / h Heating to a temperature of 700-750°C, and keeping it warm for 3 hours after reaching the temperature, the second stage is rapidly heated to 900-920°C, and the holding time is 12 hours, and air-cooled to 320-380°C after being out of the furnac...

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Abstract

A heat treatment method for strength of 28CrMoNiV steel capable of improving an industrial steam turbine rotor forge piece. The technology comprises the steps that (1), a normalizing and tempering manner is adopted in a preparation heat treatment technology and is used for refining crystalline grains and improving a material internal tissue, residual stress is reduced, and the good foundation is laid for conditioning heat treatment; a ladder heating manner is adopted in heating of normalizing and quenching, and fast heating is avoided; in the rising process, if the heating speed is too high, residual stress obtained after quenching is overlapped, and the problems that the defect of the forge piece is expanded, and even, the forge piece is cracked are possibly caused; in a quenching cooling process, a water quenching oil cooling manner is adopted, the cooling speed of a workpiece in the high-temperature stage is improved, and meanwhile, the cooling speed of a Martensite transition zone is reduced; in the water cooling initial stage, the workpiece vertically moves in a front-and-back manner in water, the quenching effect of the workpiece is fully ensured, and meanwhile, the structural stress and heat stress are reduced; in the medium heat treatment, the tempering temperature is properly reduced, impact toughness is ensured, and meanwhile, the strength of the force piece is improved.

Description

technical field [0001] The invention belongs to the technical field of production of industrial steam turbine steel forgings, and in particular relates to a heat treatment process with high strength requirements, in particular to a heat treatment process for improving the strength of 28CrMoNiV steel for industrial steam turbine rotor forgings. Background technique [0002] Industrial steam turbine rotors work at high speeds, complex stress conditions, and harsh working environments. The quality requirements for rotor forgings are high, and good toughness and toughness are required. If the rotor forgings are not strong enough but tough enough, the efficiency of industrial steam turbines will be low, which is not conducive to market competition. In order to adapt to market competition, realize cost reduction and increase efficiency, and improve unit efficiency, for units with low inlet steam temperature (less than 450°C), its strength is improved under the condition of ensurin...

Claims

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Application Information

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IPC IPC(8): C21D6/00C22C38/46
Inventor 刘中华徐伟黄淑秋何成郝明闪叶伟宋思远
Owner HANGZHOU TURBINE POWER GRP
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