GALLING RESISTANT STEEL PLATES DEMONSTRATING EXCELLENT IMPACT TOUGHNESS OF WELD AND EXCELLENT RESIST

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FIELD : metallurgy. SUBSTANCE : invention relates to metallurgy, namely to galling resistant steel plates used in construction, machines manufacturing, shipbuilding, for pipes manufacturing. Steel contains wt % : from 0.20 to 0.30 C, from 0.05 to 1.0 Si, from 0.40 to 1.2 Mn, 0.010 or below P, 0.005 or below S, from 0.40 to 1.5 Cr, from 0.05 to 1.0 Mo, from 0.005 to 0.025 Nb, from 0.005 to 0.03 Ti, 0.1 or below Al, from 0.0015 to 0.0060 N, from 0.0003 to 0.0020 B, Fe and inevitable admixtures - rest. Steel can additionally contain one or several components selected from the group containing W, Ci, Ni, V, rare earth elements, Ca and Mg, and has quenching coefficient determined as follows : DI*=33.85×(0.1×C)0.5×(0.7×Si+1)×(3.33×Mn+1)×(0.35×Cu+1)×(0.36×Ni+1)×(2.16×Cr+1)×(3×Mo+1)× (1.75×V+1)× (1.5×W+1), equal to 45 to 180. Steel has microstructure, its main phase is created by martensite, and particles of Nb and Ti carbonitrides having average size 1 micron or below, in quantity 1000 pc./mm2 or over, and average size of particles of preceeding austenite below 200 microns. EFFECT : steel use ensures required impact toughness and resistance to delayed fracture of the multipassed weld. 14 cl, 2 dwg, 6 tbl