PURPOSE: To obtain carburized parts having moderate internal hardness and small heat treatment strain in a short carburizing time by reducing the amount of C in a high C carburizing steel having a specified composition for a gear, bearings, etc., restricting the amounts of Al and O, and adding Nb, V or Ti.
CONSTITUTION: This carburizing steel consists of, by weight, 0.26W0.33% C, 0.50W1.50% Si, 0.50W1.50% Mn, 0.50W1.50% Cr, 0.020W0.050% Al, ≤0.0025% O, one or more among ≤0.25% each of Nb, V and Ti, and the balance Fe or further contains 0.05W0.30% Mo. When the steel is carburized, the carburizing time can be shortened, moderate internal hardness required by carburized parts such as a gear and roller bearings is provided, and the heat treatment strain is small. The steel has superior strength and a long fatigue life.
KUMAGAI KENICHI
WAKIKADO SHIGEHIRO
