PURPOSE: To produce a nonmagnetic roller bearing excellent in rolling life by subjecting roller bearing parts made of nonmagnetic steel with specific composition to electric discharge carburizing treatment and providing a surface hardened layer with specific surface hardness and also a specific magnetic permeability.
CONSTITUTION: The roller bearing parts are formed by using a nonmagnetic Mn-Cr austenitic steel having a composition consisting of 0.1-0.7% C, ≤1% Si, 12-20% Mn, ≤5% Ni, 10-18% Cr, ≤0.50% N, and the balance Fe with inevitable impurities. The parts are heated and held at about 950-1200°C and subjected to electric discharge carburizing treatment in a hydrocarbon gas atmosphere of about 1-50mmHg for 2-3hr, followed by air cooling. By this method, the rolling bearing parts having a surface hardened layer with a surface hardness of ≥HRC55 Rockwell C hardness and also having ≤1.1% magnetic permeability can be obtained, and rolling life can be improved.
NAKAJIMA HIROKAZU
UEDA AKIFUMI
