This Standard specifies technical requirements, inspection methods, pickling inspection regulations, steel ball crushing load values of rolling bearing parts made from Cr4Mo4V bearing steel elevated temperature after annealing, quenching and tempering.
This Standard is applicable to heat treatment quality inspection for above-mentioned steel rolling bearing parts interprocess and finished parts. The bearing parts with special requirements shall be in accordance with the corresponding standards and product drawings.
2. Normative References
The following standards contain provisions which, through reference in this text, constitute provisions of this standard. For dated reference, subsequent amendments to (excluding correction to), or revisions of, any of these publications do not apply. However, the parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the standards. For undated references, the latest edition of the normative document referred to applies.
GB/T 2301-2004 Metallic Materials - Rockwell Hardness Test - Part 1: Test Method (Scales A, B, C, D, E, F, G, H, K, N, T) (ISO 6508-1: 1999, MOD)
GB/T 231.1-2002 Metallic Materials-Brinell Hardness Test-Part 1: Test Method (eqv ISO 6506-1: 1999)
GB/T 4340.1-1999 Metallic Materials-Vickers Hardness Test -Part 1: Test Method (eqv ISO 6507-1: 1997)
GB/T 6394-2002 Metal-Methods for Estimating the Average Grain Size (ASTME 112: 1996, MOD)
JB/T 1255-2001 Specification for Heat-treatment of Rolling Bearing Parts Made from High Carbon Chromium Steel
JB/T 7361-2007 Rolling Bearings-Test Method for Hardness of Parts
JB/T 7362-2007 Rolling Bearings-Determination of Decarburized Depth for Parts
3. Technical Requirements
3.1 Technical requirements for bearing parts after annealing
3.1.1 Hardness
Hardness of bearing parts after annealing is 197HB~241HB (impression diameter is 4.3mm~3.9mm) or 94HRB~100HRB.
3.1.2 Decarburized layer
The decarburized layer of bearing parts shall be measured at the deepest point and its depth shall not exceed two-thirds of the minimum machining allowance on each side before quenching.
3.2 Technical requirements for bearing parts after quenching and tempering
3.2.1 Hardness
3.2.1.1 Hardness after quenching and tempering
Hardness of ferrule and rolling element after quenching shall generally not be less than 63HRC.Post-tempering hardness: 60HRC~65HRC for ferrule and 61HRC~66HRC for rolling element.
3.2.1.2 Hardness difference of the same part
Hardness difference of the same part after quenching and tempering:
a) Where the outside diameter of ferrule is not greater than 100mm and the diameter of rolling element is not greater than 22mm, hardness difference of the same part shall not be greater than 1HRC;
b) Where the outside diameter of ferrule is greater than 100mm and the diameter of rolling element is greater than 22mm, hardness difference of the same part shall not be greater than 2HRC;
c) Hardness difference of the same part is not inspected where steel ball diameter is not greater than 1.588mm (1/16m).
Note: tapered roller diameter shall be calculated by the small end.
3.2.2 Grain size of quenched structure
Grain size of quenched structure of bearing parts shall be evaluated by the comparison method according to the first-order pictures:
a) Hardness of first-order structure grain size after tempering shall be regarded as qualified if it meets the requirements;
b) Second-order ~ fourth-order structure grain size shall be regarded as qualified;
c) The structure with more than fourth-order grain size shall be observed under 100 times of magnification factor from the worst view field according to the requirements of 5.1.2.a) of GB/T 6394-2002. The structure containing grains of fifth-order grain size exceeding 15% of this view field area is unqualified.
3.2.3 Microscopic structure
Microscopic structures of bearing parts after quenching and tempering shall be composed of martensite, primary carbide, secondary carbide and retained austenite.
The microscopic structure after tempering shall be evaluated based on thickness of martensite matrix structure and dissolution of carbide according to second-order pictures:
a) First-order is underheating structure, and its hardness shall be regarded as qualified if it meets the requirements;
b) Second-order ~ fourth-order structure shall be regarded as qualified;
c) The structure above fourth-order one is overheated and unqualified.
3.2.4 Tempering stability
Where retempering is carried out for 2h according to the normal tempering temperature of the parts and hardness is measured at the corresponding point in the same position, the maximum hardness difference of the corresponding point shall not exceed 1 HRC.
3.2.5 Crack and soft spot
Bearing parts shall be free from cracks or soft spots after quenching and tempering or during grinding and manufacturing process.
3.2.6 Decarburized layer and other surface defects
Surface decarburized layers, corrosion pits, scale and other defects that are generated on the bearing parts after quenching and tempering shall be removed during grinding and manufacturing process. The finished bearing parts shall be free from decarburized layer and other surface defect.
3.2.7 Crushing load of steel ball
Crushing load test shall be carried out for 3mm~50.8mm (2in) steel ball and the crushing load value shall not be less than the requirements of Appendix F.
3.2.8 Ferrule deformation amount
Deformation amount of bearing ring after quenching and tempering shall be in accordance with the requirements of Appendix F of JB/T 1255-2001.
3.2.9 Mixing
Bearing parts shall not be mixed into other materials.
4. Inspection Methods
Contents
Foreword i
1. Scope
2. Normative References
3. Technical Requirements
4. Inspection Methods
Appendix A (Normative) Correction Value of Steel Ball Hardness
Appendix B (Normative) Correction Value of Roller Hardness
Appendix C (Normative) Pickling Inspection Regulation
Appendix D (Normative) Inspection Regulation for Surface Defects of Bearing Parts
Appendix E (Normative) Inspection Regulation for Mixing of Different Steel Grades
Appendix F (Normative) Steel Ball Crushing Load Value
