Seamless pipe manufacturing method

Abstract

There is provided a method for manufacturing a seamless pipe or tube that is capable of making more uniform the wall thickness distribution of a pipe or tube along the longitudinal direction of the pipe or tube than the prior art. The method for manufacturing a seamless pipe or tube according to the present invention comprises a first step of measuring the outside diameter distribution of thg mandrel bar B along the longitudinal direction of the mandrel bar at normal temperature; a second step of measuring the temperature distribution of the mandrel bar along the longitudinal direction of themandrel bar in the mandrel bar after it being used for a drawing and rolling step in a mandrel mill M; and a third step of measuring the wall thickness distribution of the pipe or tube in the hot state after it being subjected to drawing and rolling with the mandrel bar being inserted thereinto, along the longitudinal direction of the pipe or tube. And the method comprises a fourth step of calculating the outside diameter distribution of the mandrel bar along the longitudinal direction of the mandrel bar at the time of being used for drawing and rolling on the basis of the respective parameters which have been obtained at the first to third steps, and a fifth step of adjusting the setting position of the grooved roll R in the rolling direction on the basis of the outside diameter distribution of the mandrel bar along the longitudinal direction of the mandrel bar when the mandrel bar is inserted into the inside of a pipr or tube at the next timing for being used for drawing and rolling.

Description

technical field [0001] The present invention relates to a method for manufacturing seamless pipes. In particular, the present invention relates to a method for manufacturing a seamless pipe capable of uniformizing the thickness distribution in the longitudinal direction of the pipe. Background technique [0002] As the mandrel mill, the two-roll mandrel mill and the three-roll mandrel mill have been used in the past, and the two-roll mandrel mill will be relatively The two grooved rolls are arranged on each rolling mill, and the rolling direction of the grooved rolls is alternately arranged by staggering 90° between adjacent rolling mills. The three-roller mandrel seamless pipe Three grooved rolls are arranged on each rolling mill so that the angle formed by the rolling direction is 120°, and the rolling direction of the grooved rolls is alternately shifted by 60° between adjacent rolling mills. to configure. In addition, a four-high type mandrel mill in which four groove...

AI Technical Summary

Problems solved by technology

[0004] As mentioned above, since each mandrel is recycled, it tends to wear unevenly along its length

In addition, the mandrel thermally expands unevenly in its longitudinal direction due to heat generated from heat conduction from the portion in contact with the pipe during elongation and rolling, and heat generated by processing due to elongation and rolling.

Therefore, there is a problem that the wall thickness distribution in the longitudinal direction of the pipe after elongation and rolling tends to become non-uniform.

Therefore, in the method described in Patent Document 3, the wall thickness distribution in the longitudinal direction of the pipe after elongation and rolling cannot be sufficiently uniformed.

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