| 摘要 |
<p>PROBLEM TO BE SOLVED: To highly efficiently manufacture a thick-wall seamless steel tube having the highly precise dimension of an outside diameter by restricting the variation of outside diameter by a plug mill, controlling the temp. of a stock tube to a prescribed range at the front of a sizer mill and reducing the total draft by a sizer mill. SOLUTION: A cast slab 7 is heated in a heating furnace 1, formed into a hollow stock tube by a piercer mill (piercer) and reduction of thickness and expansion of the outside diameter are executed by an elongator mill 3. Rolling of prescribed passes is executed at the draft to the outside diameter within the range of 1-1.5% per pass by a plug mill 4 and rolling is executed at the total draft to the outside diameter within the range of 1-3% by a sizer mill 6. Then, at the front of the sizer mill 6, the temp. of the tube stock is kept at the range of 900-950 deg.C. In this way, the thick-wall seamless steel tube is manufactured highly precisely in high yield.</p> |
