Method for refining grains of large medium high alloy steel forgings

A technology for large-scale forgings and high-alloy steel, applied in heat treatment equipment, heat treatment process control, manufacturing tools, etc., can solve problems such as coarse grains and mixed grains, and unstable grain refinement effect of large forgings, and achieve simple and easy operation process line, reduce energy and time cost consumption, and reduce the effect of tissue inheritance

Inactive Publication Date: 2011-07-27
SHANGHAI JIAO TONG UNIV
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  • Abstract
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Problems solved by technology

[0008] Aiming at the above-mentioned deficiencies in the prior art, the present invention provides a grain refinement method for large-scale forgings of medium-high alloy steel, which solves the problem of unstable grain refinement effect of large-scale forgings caused by traditional multiple normalizing processes in actual production, and coarse grains. and the serious problem of mixed crystal phenomenon

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  • Method for refining grains of large medium high alloy steel forgings
  • Method for refining grains of large medium high alloy steel forgings
  • Method for refining grains of large medium high alloy steel forgings

Examples

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Effect test

Embodiment 1

[0032] The test adopts 30Cr2Ni4MoV steel commonly used in large forgings of low-pressure rotors, and its original grain size is about ASTM No.1.0 grade, see figure 1 As shown, its chemical composition is shown in Table 1, and the test material was processed into a 15mm×15mm×15mm sample. Firstly, heat the sample from room temperature to 840°C at a heating rate of 30°C / h and keep it warm for 3 hours; then cool the sample at a rate of 50°C / h to the pearlite transition nose temperature of 600°C and keep it warm for 120 hours to form a certain amount of Pearlite structure distributed in a network (such as figure 2 shown), so as to eliminate tissue genetics, and then cool to room temperature; then, heat the sample to 870°C at a heating rate of 30°C / h, and keep it for 3h to make the austenitization uniform, and the austenitization recrystallization is fine crystallization, then cooled to room temperature, the grain size see image 3 shown. The test results show that this method m...

Embodiment 2

[0036] The test adopts 30Cr2Ni4MoV steel commonly used in large forgings of low-pressure rotors, and its original grain size is about ASTM No.1.0 grade, see figure 1 As shown, its chemical composition is shown in Table 1, and the test material was processed into a 15mm×15mm×15mm sample. First, heat the sample from room temperature to 840°C at a heating rate of 30°C / h, and keep it warm for 3 hours; then cool the sample at a rate of 50°C / h to the pearlite transition nose temperature of 600°C, and keep it warm for 240 hours to form a certain amount of Pearlite structure distributed in a network (such as Figure 4 shown), so as to eliminate tissue genetics, and then cool to room temperature; then, heat the sample to 870°C at a heating rate of 30°C / h, and keep it for 3h to make the austenitization uniform, and the austenitization recrystallization is fine crystallization, then cooled to room temperature, the grain size see Figure 5 shown. The test results show that this method ...

Embodiment 3

[0038] The test adopts 30Cr2Ni4MoV steel commonly used in large forgings of low-pressure rotors, and its original grain size is about ASTM No.1.0 grade, see figure 1 As shown, its chemical composition is shown in Table 1, and the test material was processed into a 15mm×15mm×15mm sample. First, heat the sample from room temperature to 840°C at a heating rate of 30°C / h and keep it warm for 3 hours; then cool the sample at a rate of 50°C / h to the pearlite transition nose temperature of 600°C and keep it warm for 360 hours to generate a certain amount of Pearlite structure distributed in a network (such as Figure 6 shown), so as to eliminate tissue genetics, and then cool to room temperature; then, heat the sample to 870°C at a heating rate of 30°C / h, and keep it for 3h to make the austenitization uniform, and the austenitization recrystallization is fine crystallization, then cooled to room temperature, the grain size see Figure 7 shown. The test results show that this metho...

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Abstract

The invention discloses a method for refining grains of large medium high alloy steel forgings in the technical field of metal heat treatment. The method comprises the following steps of: austenitizing the forged forgings, cooling to tip temperature of a perlitic transformation area, and isothermally keeping temperature or fluctuantly keeping temperature to realizing isothermal decomposition of pearlite; and cooling to room temperature, and performing the secondary austenitizing process to realize recrystallization to refine the grains again. The method solves the problem that the traditional multiple normalizing process in actual production has instable effect of refining the grains of the large forgings, and a serious phenomena of coarse grains and mixed grains. By incomplete isothermal balanced decomposition of austenite, structure inheritance is cut off and eliminated, average austenite grain size above ASTM No.5 grade is achieved, the structure state of the large forgings is improved, the ultrasonic inspectability of the large forgings is improved; meanwhile, working hours are greatly shortened, the energy consumption is reduced, and the cost is saved.

Description

technical field [0001] The invention relates to a method in the technical field of metal heat treatment, in particular to a method for refining grains of medium-high alloy steel large forgings. Background technique [0002] Large-scale forgings are the load-bearing and transmission structural components of nuclear power, thermal power and other power station equipment and large-scale metallurgy, mining and transportation equipment. They are core components and the basis for reliable operation of equipment. The large-scale equipment also makes the forging large-scale, especially under the guidance of the design idea of ​​improving efficiency, reducing consumption, and safety and reliability. In addition to using a large amount of high-alloy steel, it also integrates the original combined parts through subsequent assembly. The size and weight of the single forging are increased dramatically. In the main equipment of nuclear power, thermal power, hydropower and gas power gener...

Claims

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Application Information

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IPC IPC(8): C21D11/00C21D1/18
Inventor 顾剑锋陈睿恺韩利战潘健生
Owner SHANGHAI JIAO TONG UNIV
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