GB/T 38885-2020General specification for ultra-high cleanliness of high carbon chromium bearing steel (English PDF)

5.15 Contact fatigue life

The rated life L10 of the steel under the maximum contact stress of 4500 GPa shall not be less than 1 x 10^7 times.

6.1 Dimensions and appearance

Steel size measurement is carried out by a caliper or template that can ensure the necessary accuracy.

6.2 Chemical composition

6.2.1 The analysis method of chemical composition shall be carried out according to the general methods such as GB/T 4336, GB/T 20123, GB/T 20125, GB/T 32548. For arbitration, it shall be according to the provisions of GB/T 223.5, GB/T 223.9, GB/T 223.11, GB/T 223.23, GB/T 223.26, GB/T 223.29, GB/T 223.31, GB/T 223.47. GB/T 223.50, GB/T 223.53, GB/T 223.62,

GB/T 223.63, GB/T 223.77, GB/T 223.85, GB/T 223.86.

6.2.2 The oxygen content specimen shall be tested after fully removing the decarburized layer. Its analysis method shall be carried out according to GB/T 11261.

6.2.3 The analysis method of titanium content shall be determined by the supplier and the buyer through negotiation.

6.3 Mechanical properties

The test method of Brinell hardness is in accordance with the provisions of GB/T 231.1. The tensile test method is in accordance with GB/T 228.1.

6.4 Macroscopic

The macroscopic acid leaching test method is carried out according to GB/T 226. The rating diagram is carried out according to Appendix A in GB/T 18254-2016.

6.5 Macroscopic inclusions

Macroscopic inclusions shall be carried out according to the requirements of GB/T 38683-2020.

6.6 Microscopic inclusions

Specimens of non-metallic inclusions are quenched and tempered in accordance with 6.15 and observed at a magnification of 100 times. The evaluation method and rating diagram are performed in accordance with the method A in GB/T 10561-2005.

6.7 Decarburization layer

The measurement of the depth of the total decarburization layer is carried out in accordance with the metallographic method in GB/T 224-2019.

6.8 Microstructure

For microstructure testing, a transverse sample is taken. The polished surface is etched with a 2% nitric acid alcohol solution and observed at a magnification of 1000 times. It is rated according to the level 5 rating diagram in Appendix A of GB/T 18254-2016.

6.9 Carbide inhomogeneity

6.9.1 For the testing of carbide network, take transverse specimens; quench and temper it according to 6.15; use 4% nitric acid alcohol solution to etch it after polishing. The spheroidizing annealing steel is rated according to the level 6 rating diagram in Appendix A of GB/T 18254-2016 at a magnification of 500 times. The supplier can also evaluate the carbide network on the longitudinal specimen, but the transverse direction shall prevail.

6.9.2 For the testing of carbide strip, take longitudinal specimens. Quench and temper it according to 6.15 in the annealed state; use the 4% nitric acid alcohol solution to etch it after polishing. Make evaluation at the magnification of 100 times and 500 times. Follow the level 8 rating diagram in Appendix A of GB/T 18254-2016 to evaluate the degree, size and shape of carbide aggregation.

6.9.3 For the testing of carbide liquid precipitation, take the longitudinal specimen. Follow the requirements of 6.15 to perform quenching and tempering.

After polishing, use the 4% nitric acid alcohol solution to etch it. Evaluate it according to the level 9 rating diagram in Appendix A of GB/T 18254-2016 at the magnification of 100 times.

6.10 Microscopic porosity

For the testing, take the longitudinal specimen for quenching and tempering according to 6.15. Evaluate it according to the level 10 rating diagram in Appendix A of GB/T 18254-2016 at the magnification of 100 times.

6.11 Grain size

right to conduct inspection and acceptance in accordance with the provisions of this standard.

7.2 Inspection classification

7.2.1 Type inspection

7.2.1.1 In one of the following situations, the manufacturer shall conduct type inspection:

a) Trial type identification of new product or the trans-plant production of old products;

b) After normal production, if there are major changes in materials, processes, and equipment that may affect product performance;

c) When the production is restored after suspension for more than 1 year;

d) When there is a big difference between the exit-factory inspection result and the last type inspection result;

e) During normal production, inspection shall be carried out every 1 year;

f) When the contract requires type inspection.

7.2.1.2 See Table 14 for type inspection items, sampling quantity and sampling locations.

7.2.1.3 When one of the inspection items is unqualified, the type inspection fails.

7.2.2 Exit-factory inspection

7.2.2.1 Group-batching rules

The steel shall be inspected and accepted by batch. Each batch shall be composed of steel with the same heat number, the same designation, the same size, the same delivery status, the same heat treatment furnace batch.

7.2.2.2 Sampling quantity and sampling location

7.2.2.2.1 See Table 14 for the sampling quantity and sampling location of each batch of steel. […]