JPS57106414A - Continuous manufacturing of seamless steel pipe having different wall thickness - Google Patents

Abstract

PURPOSE: To continuously manufacture plural steel pipes having same diam. and different wall thickness from one blank pipe, by changing setting of reduction for a hollow blank pipe on the way to obtain a shell having different wall thickness, and rolling said shell into a pipe having prescribed outer diam. under a constant draft by a sizer.

CONSTITUTION: On the way of rolling of a hollow blank pipe with nearly the uniform outer diam. and wall thickness to be bitten by a steel pipe rolling mill, the setting of rotating speed of a roll and the roll gap of the rolling mill are changed to obtain a shell having a constant internal diam., and a outer diam. being changed on the way of rolling. This shell is rolled into a pipe having a prescribed outer diam. by a sizer under a constant draft to manufacture a steel pipe with same diam. but different in the wall thickness on the way of rolling. In this case, when the tension between the stands is not subjected under reduction of the sizer, the wall thickness equivalent to the half percentage of that of draft for outer diam. is increased, so that the wall thickness of shell is determined under consideration of the increase of said wall thickness for the dimension of wall thickness of the product.

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