Patent ID: 7325429

Claim:
A method for manufacturing a high-Cr seamless steel pipe or tube, comprised by heating a round billet in a heating furnace followed by piercing and rolling with an inclined roll type piercing mill, the said round billet containing, by mass %, 10.50 to 14.00% of Cr, with a value of Cr* represented by the following equation (1) of not more than 9.0%; the said heating furnace being set so that an in-furnace time from the charging of the round billet into the heating furnace to the discharging therefrom satisfies the following equation (2) at a soaking temperature of 1100 to 1250° C.; and the said inclined roll type piercing mill having a piercing efficiency of not less than 50% and a plug tip draft rate represented by the following equation (3) of not more than 8.0% as the piercing and rolling conditions thereby: Cr*=Cr+4Si−(22C+0.5Mn+1.5Ni+30N) (1), In-furnace time (min)≧0.5×Diameter of the round billet (mm) (2), Plug tip draft rate (%)={(Diameter of the round billet (mm)−Roll gap at the foremost end of the plug (mm))/Diameter of the round billet (mm)}×100 (3), wherein, in the above equation (1), the symbols of the elements represent the contents, by mass %, of the elements in the high-Cr steel.