Fine carbides in the original tissue, due to the carbide easy integration into the austenite, so the hardness after quenching peak toward lower temperatures and appeared in a short austenitizing time
Obtained in order to make the material factors of these effects ina bearing life at its best, you first need to control the quenching of steel before the original organization, technical measures can be taken are: high temperature (1050 ° C) austenitic-speed cooling to 630 ℃ temperature normalizing pseudo-eutectoid fine pearlite, or cold to 420 ° C, such as processing temperature, bainite can be forged waste heat rapid thermal annealing, the fine granular pearlite to ensure that the carbide steel fine and uniform distribution of this the original organization of the state in the quenching of austenitizing, in addition to integration into the carbide in austenite, undissolved carbides, will gather into a fine granular
Overall eccentric bearing in tensile, compression, bent, cut, alternating under the value of the complex stress state and high stress, high-speed, work long hours. Therefore, in the production process, bearing steel quality control test items, the control range is narrow, strict and complex production process requires a certain tooling equipment, testing instruments, and a certain level of villain character technology. In order to ensure the bearing has good performance and high life expectancy, the quality of bearing steel requirements are as follows:
(1) Chemical composition: The chemical composition is the most essential factors bearing steel. Steel physics, chemistry, mechanical properties and microstructure are determined by the chemical composition, change the chemical composition, change the basic nature of the steel. Therefore, the chemical composition of bearing steel must conform to the standards the allowable range.
(2) internal quality: can be divided into macro quality and microstructure quality.
The quality of the macro: requirements within the bearing steel is not allowed to have white spots, shrinkage, slag, China metal, cracks, over-burning, subcutaneous bubbles and other defects. Requirements within the overall eccentric bearing steel segregation, porosity is controlled within a certain range. In short, bearing steel internal dense, does not allow any visible defects in the fragmented steel substrate.
(3) Surface quality: ina bearing parts of the molding method, there are currently forging, turning and cold punch and so on. Steel surface quality requirements of the different levels of different molding methods. In general, the surface of the bearing steel shall not crack, folding, fracturing, scarring, and slag. Washed with cold cold drawn steel, with the exception does not allow the above defects, the surface should be clean, no rust, Ma concave defects. Bearing steel surface may not have serious decarburization phenomenon, according to the different requirements of the molding process of the overall eccentric bearing parts in the standard, the depth of decarburization of the steel surface of the different varieties have different restrictions.
To sum up, the undissolved carbides gcrl5 steel after quenching at about 7% of retained austenite in 9%, the average carbon content of (hidden martensite of about 0.55%) is the best organization and, when carbide in the original organization is small, evenly distributed, reliable control of the level of microstructure, high mechanical properties, which has a high service life should be pointed out that, with a small dispersion of the original distribution of carbide organizations, to quench the heat insulation, the undissolved fine carbides gathered grew, so coarsening Therefore, with this original organization ina bearing parts quenching time not too long, using the process of rapid heating, quenching austenite will receive the higher mechanical properties