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International Journal of Automotive Technology 2009;10(6): 697-702. |
GRAIN REFINEMENT IN BEARING STEELS USING A DOUBLE-QUENCHING HEAT-TREATMENT PROCESS |
K. O. LEE1, S. K. HONG1, Y. K. KANG2, H. J. YOON2, S. S. KANG1 |
1Pusan National University 2ILJIN GLOBAL |
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ABSTRACT |
A double-quenching (D/Q) process is proposed for heat-treating high carbon-chromium bearing steels to improve the fatigue properties through refinement of the microstructure. The new heat treatment method has two steps: The first step is a nitrocarburizing process that results in high surface hardness and lowers the transformation temperature. The second step is the same as in the conventional quenching process but can be conducted at a considerably lower temperature than in conventional quenching. The microstructure in the material that is caused by the D/Q heat treatment is much finer than in the conventional Q/T (quenching and tempering) process. In order to quantify the performance of the proposed heattreatment process, various mechanical property tests are carried out. The rolling contact fatigue life of double-quenched bearing steels was eight times higher than in bearing steels that were treated by conventional Q/T. |
Key Words:
Bearing steel, Double quenching, Grain refinement, Prior austenite, Rolling contact fatigue |
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