| 摘要 |
PROBLEM TO BE SOLVED: To manufacture a seamless steel tube of a high-load material by a line for mainly manufacturing medium/small-diameter size seamless steel tube using an inclined piercer. SOLUTION: After piercing a billet 1 with the inclined piercer 2, a roll gap and guide shoes are opened larger than the outside diameter of a hollow tube stock 7 and the hollow tube stock 7 is moved to an inlet-side position from an outlet-side position with return rolls 6. After changing an piercing plug 5 at the tip of a mandrel bar 4 into a plug 8 at the 2nd piercing and changing the roll gap and the guide shoes into the 2nd piercing condition, the 2nd piercing is performed. Like this, piercing is performed several times with the same inclined piercer 2.
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