STEEL FOR CARBURIZING AND CARBO-NITRIDING

PROBLEM TO BE SOLVED: To improve the impact strength of steel as well as its pitting fatigue strength for the requirements to the miniaturization and lightening of machine parts and the load of high stress. SOLUTION: This steel for carburizing and carbo-nitriding contains, by mass, 0.10 to 0.30% C, 0.40 to 1.00% Si and 0.30 to 1.50% Mn, and moreover, P, S, Ni, Cr, Cu, Mo, Al, Nb, N and O are controlled. Furthermore, one or more kinds among V, Ti and B may be incorporated into the above steel, and moreover, one or more kinds among Pb, Bi, Te, Zr and Ca of fixed contents may be incorporated as the elements which further improve its machinability and do not remarkably impede its fatigue characteristics.