Patent ID: 9468959
Filing Date: 2016-10-18
CPC Classification: B21B,B22D,C21D,C22C,C22F,Y10T

Claim Text:
1. A production method of a seamless tube with a Mannesmann tube-making process comprising: subjecting a continuously cast slab with a rectangular cross section, and made of high Cr-high Ni alloy containing Cr of 20 to 30 mass %, Ni of 30 to 50 mass %, and at least one of Mo and W as Mo+0.5W of 1.5 to 10 mass % to a blooming and billet-making process to yield a round bar having a diameter of 150 to 400 mm; subjecting the round bar to a piercing-rolling process through a piercing mill to yield a hollow blank; and subjecting the hollow blank to an elongation-rolling process through an elongation-rolling mill; followed by a diameter-adjusting-rolling process through a diameter-adjusting-rolling mill; wherein the blooming and billet-making process is carried out under a condition satisfying a relation of 1.3≦H/D≦1.8 where a short side length of the cross section of the cast slab is defined as H (mm), and the diameter of the round bar is defined as D (mm).