Sumitomo Metal Industries, Inc.

Satoshi Tsuyuguchi

Toshihide Ono

Tomio Yamakawa

Kouichi Kuroda

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 &#x3b7; defined by an equation (1) ranges from 1.0&#xd7;10to 1.5&#xd7;10. The offset amount is set at 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. 

Process for straightening a tube

In the cold rolling process by pilger rolling that holds a mandrel between each of paired roll-dies, by optimizing the side relief rate SR and the pass schedule factors such as the Area Rd, ID Rd and the feed rate F of the workpiece material, and further by properly selecting the taper &#x3b8;in the primary deformation zone of mandrel and the taper &#x3b8;in the final size reduction zone thereof, the dimension-related shape characteristics (near-perfect round shape) of the tube inside surface after the final finishing rolling process by pilger rolling can be ascertained to thereby ensure excellent surface property without requiring a new apparatus, and further without causing the decrease of the product yield and/or the increase of the manufacturing costs. Thus, this can be widely applied for producing steam generator tubes which exhibits high S/N ratio in the inner coil eddy current testing.

Cold rolling process for metal tubes

In the cold rolling process by pilger rolling that holds a mandrel between each of paired roll-dies, by optimizing the side relief rate SR and the mandrel factors like the taper &#x3b8;in the primary deformation zone of the mandrel and the taper &#x3b8;in the final size reduction zone thereof, and the feed rate F of the workpiece material, and at the same time by properly adjusting the relationship between the side relief rate SR and the feed rate F, the dimension-related shape characteristics (near-perfect round shape) of the tube inside surface after the final finishing rolling process by pilger rolling can be ascertained to thereby ensure excellent surface property without requiring a new apparatus, and further without causing the decrease of the product yield and/or the increase of the manufacturing costs. Thus, this can be widely applied for producing steam generator tubes which exhibits high S/N ratio in the inner coil eddy current testing.

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Hyogo, Japan

Satoshi Tsuyuguchi