HIGH-CONCENTRATION CARBURIZED/LOW-STRAIN QUENCHED MEMBER AND PROCESS FOR PRODUCING THE SAME

摘要

The present invention can provide a super carburized, low-distortion quenched member with both higher performance and minimized heat-treatment distortion attained in the field of super carburized quenching which features high strength, high contact pressure and the like. A process for the production of the super carburized low-distortion quenched member includes a primary treatment and a secondary treatment. The primary treatment comprises heating a steel member for a machine structure to a temperature within an austenite region by vacuum carburizing (low-pressure carburizing) to have carbon dissolved at least at a eutectoid carbon concentration of a surface layer portion of the member and then quenching the member at a cooling rate of from 3 to 15°C/sec from the temperature within the austenite region to a temperature not higher than an A1 transformation point to have at least one of ultrafine carbide and nuclei of the carbide formed in the surface layer portion of the member. The secondary treatment comprises subsequently heating and soaking the member to a temperature within the austenite region and then conducting rapid quenching to have ultrafine carbide precipitated in a range of from 10 to 30% in terms of effective case depth percentage in an outermost surface layer portion.