PURPOSE: To obtain a composite film forming tool for hot working having excellent characteristics in both terms of wear resistance and thermal crack resistance which normally contradict from each other by forming a metal-carbide composite film on the surface of a base material by using carbon particles having a specific average grain size and volumetric ratio.

CONSTITUTION: The metal-carbide composite film contg. the carbide particles having the average grain size of 65 to 135μm at the volumetric ratio of 20 to 50% is formed on the surface of the base material for the composite film forming tool for hot working. This composite film forming tool for hot working has the excellent high-temp. wear resistance and thermal impact resistance in combination. Particularly excellent performance is obtainable therewith by using niobium carbide as the carbide. The tool having an excellent tool life is thus obtd. A plug life is greatly prolonged and a pipe making cost is reduced when this tool is applied particularly to the plug for a plug mill at the time of producing a hot worked seamless steel pipe. In addition, the product having the excellent inside surface quality of the product and dimensional accuracy is obtd.