Patent ID: 9469895
Filing Date: 2016-10-18
CPC Classification: C21D,C22C,C23C

Claim Text:
1. A surface treatment method for a steel material consisting of, by weight %, 0.27 to 0.48% of C, 0.01 to 2.2% of Si, 0.30 to 1.0% of Mn, not more than 0.035% of P, not more than 0.035% of S, and the balance of Fe and inevitable impurities, the method comprising, in this order: a step of carbonitriding the steel by heating at a temperature of not less than the A a step of quenching the steel to room temperature at a rate of not less than 20° C./second; and a step of tempering the steel at a temperature of 100 to 400° C.