| 摘要 |
<p>PROBLEM TO BE SOLVED: To prevent an occurrence of fin flaws of a material in an outside diameter contracting stand by measuring an outside diameter in each position in the axial length direction of a hollow tube stock on the inlet side of the outside diameter contracting stand, and adjusting the roll gap of the outside diameter contracting stand according to measured result. SOLUTION: The outside diameter in each position in the axial length direction of the hollow tube stock obtained by piercing with a piercer 1, is continuously measured by an outside diameter measuring equipment 2, and measured results are inputted to a computing element 4. A draft in the outside diameter contracting stand 3 in each position in the axial length direction of the hollow tube stock, is calculated by the computing element 4 according to the inputted outside diameters and a finish target outside diameter in the outside diameter contracting stand 3. Also, the computed result of the draft and a critical draft by which the fin flaws of the material, which have been obtained preliminarily by an experiment, do not occur, are compared by the computing element 4, and a roll gap adjustment quantity is obtained. A diameter is contracted while adjusting and controlling to the critical draft or below by which the fin flaws of the material do not occur. Consequently, the draft does not become excessive, and the fin flaws of the material to the gap of rolls are prevented.</p> |
