| 摘要 |
PURPOSE:To develop tool steel materials for hot working having excellent characteristics as the material for various hot working dies by decreasing the impurities in a low-alloy steel contg. specific ratios of Cr, Mo, W, V, Co, Ni, N, etc., as best as possible. CONSTITUTION:This steel contains, by weight%, 0.10-0.70% C and <1.50% Mn, contains a specific ratio of 1 or 2 kinds of Cr, Mo and W and further Co in addition thereto or contains specific ratios of 1 or 2 kinds of Ni, W and Mo or 1 or 2 kinds of Cr, Mo and W and V, Co and a specific ratio of N in addition to C and Mn. Si, P, S, and O as the impurities contained in such steel are confined to specific values of below and further the total content of As, Sn, Sb, Cu, B, Pb, and Bi is confined to <=0.13%. The steel materials having <1.30 microsegregation degree in structure, <=0.010% TISdA cleanliness of nonmetallic inclusions, <=0.020% d(B+C) and isotropy of >=0.75 toughness value in the extend forging direction/the toughness value in the direction perpendicular thereto are used as the tool steel for hot working.
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