Hot work tool steel, for hot working tool and a seamless pipe manufacturing plug

Adhesion and lubricity of oxide scale that formed on the surface is good, a hot working tool steel of a high strength. The tool steel, C: 0.05~0.5%, Si: 0.1~1%, Mn: 1.6~3.5%, Ni: 0.05~0.5%, Mo: 2 ~5%, W: 2~5%, Cu: includes 0.05% to 0.5%, the balance being substantially Fe. Further, Cr, Co, REM, Ti, Nb, V, may contain one or more of ZR and B. Tool made from this steel, is covered with oxide scale thickness 50~1500μm its surface. Representative examples of the tool is a drilling plug for seamless pipe production.