PURPOSE: To provide a plug material excellent in erosion resistance and crack resistance for obtaining stably and efficiently the excellent quality of a product pipe in the manufacture of a high alloy seamless steel pipe, and to provide a rolling method by which the plug is effectively applied.
CONSTITUTION: By using a plug with the layer of a high-heat strength material, whose depth from a surface is 1mm or over and 4mm or below and whose tensile strength is 15kg/mm2 or over and 50kg/mm2 or below at 1000°C in an area where at leas a damage occurs on the surface and a plug, and by rolling while supplying lubricant in the inside surface of a tube stock before rolling or during rolling, erosion and crack caused by thermal shock of the plug is prevented, and as a result, an excellent quality on the inside surface of a pipe can be attained.
YAMAMOTO SHUJI
TSURU EIJI
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