| 摘要 |
<p>In straightening a tube using a roll straightening machine provided with drum type straightening roll pairs vertically opposingly disposed, at least an outer layer portion of a roll main body is made of elastic material having spring type hardness Hs (JIS K 6301 A type) of 50 to 100 in at least three pairs of straightening rolls on an outlet side of the roll straightening machine, and an offset amount is imparted to a tube engaged in the three pairs, at least, of straightening opposing rolls such that · defined by an equation (1) ranges from 1.0×10 -3 to 1.5×10 -3 . The offset amount is set at each of three positions along a tube axis where the upper and lower rolls of each pair horizontally cross. Therefore, an S/N ratio can be enhanced in an eddy current test from inside of the tube to improve inspection efficiency, and excellent quality accuracy can be ensured in a heat transfer tube used in a steam generator and the like.
where a relationship of R= (´ 2 +L 2 ) /2´ holds, assuming that d (mm) is a tube outside diameter, L (mm) is a roll stand span of the roll straightening machine, and ´ (mm) is an offset amount.</p> |
