JB/T 8881-2020 Rolling bearings - Parts made from carburizing bearing steels - Specifications for heat treatment
1 Scope
This standard specifies the technical requirements and inspection methods for the rolling bearing parts made from carburizing bearing steels such as G15CrMo, G20CrMo, G20CrNiMo, G20CrNi2Mo, G20Cr2Ni4, G10CrNi3Mo, G20Cr2Mn2Mo, and G23Cr2Ni2Si1Mo that conform to the requirements of GB/T 3203-2016 and GB/T 33161-2016 after undergoing pre-carburization conditioning treatment, and post-carburization primary quenching and tempering + high-temperature tempering, secondary quenching and tempering, and bainite isothermal quenching.
This standard applies to the carburizing heat treatment quality inspection of the above-mentioned rolling bearing parts made from carburizing bearing steels (hereinafter referred to as “bearing parts”) as well as those made from low-carbon alloy steels.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 230.1-2018 Metallic materials - Rockwell hardness test - Part 1: Test method
GB/T 231.1-2018 Metallic materials - Brinell hardness test - Part 1: Test method
GB/T 4340.1-2009 Metallic materials - Vickers hardness test - Part 1: Test method
GB/T 6394-2017 Determination of estimating the average grain size of metal
GB/T 9450-2005 Steels - Determination and verification of the depth of carburized and hardened cases
GB/T 24606-2009 Rolling bearings - Non-destructive testing - Magnetic particle testing
GB/T 34891-2017 Rolling bearings - Parts made from high-carbon chromium bearing steels - Specifications for heat treatment
JB/T 7361-2007 Rolling bearings - Test method for hardness of parts
3 Terms and definitions
3.1
case-hardened depth (of a carburized and hardened case)
vertical distance from the surface of the part to the point where the Vickers hardness value is 550HV1
[GB/T 9450-2005, Clause 3 “Definitions”]
4 Technical requirements
4.1 Technical requirements for pre-carburization conditioning treatment
4.1.1 Bearing parts shall be subjected to conditioning treatment before carburization, and their hardness after conditioning treatment shall not be greater than 229HBW (the indentation diameter shall not be less than 4mm); the hardness of parts made from G20Cr2Ni4 steel after conditioning treatment shall not be greater than 241HBW (the indentation diameter shall not be less than 3.9mm).
4.1.2 The average grain size of bearing parts before carburization shall comply with Grade 5 or finer grain size grade stipulated in GB/T 6394-2017.
4.2 Technical requirements for carburizing heat treatment
4.2.1 Case-hardened depth
The case-hardened depth of finished parts after carburizing heat treatment shall meet those specified in Table 1.
Table 1 Case-hardened depth
Foreword II
1 Scope
2 Normative references
3 Terms and definitions
4 Technical requirements
4.1 Technical requirements for pre-carburization conditioning treatment
4.2 Technical requirements for carburizing heat treatment
5 Inspection methods
Annex A (Normative) Methods for measuring case-hardened depth
A.1 Hardness method
A.2 Macro-fracture method
A.3 Micro-structure analysis method
Annex B (Normative) Procedure for dye penetrant testing
B.1 Scope
B.2 Defect display and determination
B.3 Materials for testing and sensitivity verification
B.4 Requirements for testing surface of bearing parts
B.5 Operating method
B.6 Inspection
Bibliography
Figure 1 Diagram for measuring the depth of coarse carbides in carburized surface layer
Figure 2 First-rating diagram (coarse carbides in carburized surface layer)
Figure 3 Second-rating diagram (network carbides in carburized case)
Figure 4 Third-rating diagram (micro-structure of carburized case after post-carburization primary quenching + high-temperature tempering)
Figure 5 Fourth-rating diagram (micro-structure of carburized surface layer after post-carburization primary quenching and tempering)
Figure 6 Fifth-rating diagram (micro-structure of carburized surface layer after post-carburization secondary quenching and tempering)
Figure 7 Sixth-rating diagram (core micro-structure)
Table 1 Case-hardened depth
Table 2 Surface hardness and surface layer micro-structure
Table 3 Core hardness and core micro-structure
Table 4 Permissible deformation of bearing rings after carburizing heat treatment
Table 5 Inspection methods
Figure 1 Diagram for measuring the depth of coarse carbides in carburized surface layer
Figure 2 First-rating diagram (coarse carbides in carburized surface layer)
Figure 3 Second-rating diagram (network carbides in carburized case)
Figure 4 Third-rating diagram (micro-structure of carburized case after post-carburization primary quenching + high-temperature tempering)
Figure 5 Fourth-rating diagram (micro-structure of carburized surface layer after post-carburization primary quenching and tempering)
Figure 6 Fifth-rating diagram (micro-structure of carburized surface layer after post-carburization secondary quenching and tempering)
Figure 7 Sixth-rating diagram (core micro-structure)
Table 1 Case-hardened depth
Table 2 Surface hardness and surface layer micro-structure
Table 3 Core hardness and core micro-structure
Table 4 Permissible deformation of bearing rings after carburizing heat treatment
Table 5 Inspection methods
