Patent ID: 8663550

Claim:
A steel, for a hot work tool steel, having the following composition, all percentages being in weight percent: % Ceq = 0.26-0.55 % C = 0.20-0.55 % N = 0-0.6 % B = 0-0.45 % Cr < 1.5 % Ni = 1.0-9 % Si < 0.4 % Mn = 0-3 % Al = 0-2.5 % Mo = 0-10 % W = 0-15 % Ti = 0-3 % Ta = 0-3 % Zr = 0-3 % Hf = 0-3, % V = 0-4 % Nb = 0-3 % Cu = 0-4 % Co = 0-6, % S = 0-1 % Se = 0-1 % Te = 0-1 % Bi = 0-1 % As = 0-1 % Sb = 0-1 % Ca = 0-1, the rest consisting of iron and unavoidable impurities, wherein % C eq =% C+0.86*% N+1.2*% B, % Ni+9*% Mn+5*% Si<8, and % Mo+½% W>1.2, said steel having a low scattering structure permitting a thermal diffusivity higher than 8 mm 2 /s and wherein: x C eq *( x Mo+0.5* x W)/( x Cr+ x V+ x Nb)>8 where: xCeq—weight percent Carbon; xMo—weight percent Molybdenum: xW—weight percent Tungsten; xV—weight percent Vanadium; xNb—weight percent Niobium; where xCr, xV and xNb are the real weight percents even if present at concentrations lower than 0.05%.