Isothermal quenching method of bearing steel G55SiMoV

A technology of austempering and bearing steel, applied in the field of warm quenching technology, can solve the problems of affecting performance, early fracture, lack of systematic research on 55SiMoV steel, etc.

Inactive Publication Date: 2012-01-11
董吉广
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0006] At present, there is still a lack of systematic research on the heat treatment process of 55SiMoV steel and its relationship with the structure and performance. Conventional

Method used

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  • Isothermal quenching method of bearing steel G55SiMoV
  • Isothermal quenching method of bearing steel G55SiMoV
  • Isothermal quenching method of bearing steel G55SiMoV

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0042] The austempering method of G55SiMoV bearing steel includes the following steps in sequence:

[0043] The sample is kept at the austenitizing temperature of 890℃ for 30 minutes; then in KNO 3 +NaNO 2 Quenching in medium; cooling, when the temperature drops to 270℃, isothermal for 15min. Then it is gradually cooled, and finally tempered at 170°C for 2h; G55SiMoV steel obtains a mixed structure of lower bainite / martensite, and the lower bainite content is 15%-25%.

Embodiment 2-9

[0045] The steps are the same as in Example 1. The technical parameters are shown in Table 2.

[0046] Table 2 Example 1-9 Austempering test technical parameters

[0047]

[0048] Table 3 Analysis of Austempering Test Results of Examples 1-9

[0049]

[0050]

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PUM

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Abstract

The invention discloses an isothermal quenching method of bearing steel G55SiMoV. The isothermal quenching method is characterized in that bainitic bearing steel G55SiMoV is subjected to isothermal quenching and a quenched microstructure is a bainite/martensite mixed microstructure. The isothermal quenching method comprises the following steps of 1, keeping a sample at an austenitizing temperature of 890 to 920 DEG C for 20 to 30 minutes, 2, carrying out quenching in a medium containing KNO3 and NaNO2, 3, cooling to a temperature of 270 to 290 DEG C and keeping the temperature for 15 to 45 minutes, and 4, cooling gradually to a temperature of 170 to 190 DEG C and carrying out tempering thermal insulation for 1 to 2 hours, wherein the steel G55SiMoV treated by the above steps has a lower bainite/martensite mixed microstructure and the content of lower bainite is in a range of 15 to 25%. A workpiece treated by the isothermal quenching method has the advantages of small deformation, good size stability, generation of a surface stress state, difficult generation of grinding cracks, and high impact toughness and fracture toughness. Therefore, the isothermal quenching method can improve steel performances greatly.

Description

Technical field: [0001] The invention belongs to the field of metal material heat treatment, and relates to a bearing steel quenching process, in particular to a G55SiMoV bearing steel bainite austempering process. Background technique: [0002] At present, domestic rolling mill bearings mostly use chromium bearing steels GCr15 and GCr15SiMn, using conventional martensitic quenching and low temperature tempering processes. The steps are: [0003] The quenching heating temperature is 850±5℃ for 20 minutes after austenitizing, and then cooling by two methods: (1) directly quench into spindle oil at 25℃ (room temperature), followed by tempering at 160℃ for 2 hours; (2) respectively Quench into an isothermal bath at 160°C, 200°C, 220°C and 240°C. The isothermal residence time is 10 minutes, 30 minutes, 60 minutes and 90 minutes, respectively, and then cooled to room temperature, followed by tempering at 160°C. 2 hours. [0004] This kind of process causes part of the subcooled austenit...

Claims

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Application Information

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IPC IPC(8): C21D1/20
Inventor 董吉广
Owner 董吉广
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