Wear resistant steel sheet excellent in low temperature toughness and resistance to low temperature tempering embrittlement cracking and its production method

摘要

PROBLEM TO BE SOLVED: To provide a wear-resistant steel sheet which is excellent in suppression of occurrence of cracks in parts heated to a low-temperature toughness temperature region and a low-temperature tempering embrittlement temperature region and its production method.SOLUTION: A wear-resistant steel sheet comprises, by mass%, 0.175% or more and less than 0.250% of C, 0.05-1.00% of Si, 0.35-1.50% of Mn, less than 0.006% of P, 0.005% or less of S, 0.005-0.100% of Al, 0.10-1.00% of Cr, 0.005-0.024% of Nb, 0.005-0.050% of Ti, 0.0003-0.0030% of B and 0.0010-0.0080% of N, meets specified equations 1 and 2, and, if necessary, has a component composition comprising one or more of Mo, V, Cu, Ni, Ca, Mg and REM and includes a micro-structure, at a position of 1/4 to 3/4 of the sheet thickness, composed of a martensite single phase of an average particle size of former austenite of 20-60 μm or a martensite/bentonite mixed structure with an area fraction of island martensite of lower than 5% relative to the whole of the structure. Its production method comprises hardening the steel of the above composition directly after hot rolling.