Sumitomo Metal Industries, Inc.

Junji Nakata

Tetsuya Nakanishi

Kouji Nakaike

A round billet containing, by mass %, 10.50 to 14.00% of Cr with a value represented by the equation of 'Cr+4Si&#x2212;(22C+0.5Mn+1.5Ni+30N)' of not more than 9.0%, wherein the symbols of the elements represent the contents, by mass %, of the elements in the steel, is heated at a soaking temperature of 1100 to 1250 &#xb0; C. so that an in-furnace time (min) is not less than '0.5&#xd7;Diameter of the round billet (mm)', and then pierced and rolled with a piercing efficiency by a piercing mill of not less than 50%, a value regulated by the equation: &#x201c;{(Diameter of the round billet&#x2212;Roll gap at the foremost end of the plug)/Diameter of the round billet}&#xd7;100&#x201d; of not more than 8.0, and a plug shape represented by the equation: &#x201c;Radius of foremost end of the plug (mm)/Diameter of the round billet (mm)&#x201d; of 0.06 to 0.17. The thus-manufactured high-Cr seamless steel pipe or tube has excellent internal surface properties with minimized internal surface defects.

Growing community of inventors

Wakayama, Japan

Junji Nakata