ROTATIONAL STRAIGHTENING METHOD FOR STEEL PIPE

PROBLEM TO BE SOLVED: To provide a rotational straightening method for a steel pipe by which the bend of the steel pipe is straightened economically while visually observable concave strain figures are prevented from occurring on the inner surface of the steel pipe. SOLUTION: During or before rotational straightening of the bend, even strain is imparted to the inner surface of the pipe. Favorably, (1) a deformation restraining bar is inserted into the inner surface of the steel pipe before the rotational straightening of the bend, then bending and unbending are applied to the steel pipe with a rotational straightening machine. (2) Surface strain is evenly imparted to the inner surface of the steel pipe before the rotational straightening of the bend by blasting processing and, after that, the bending and unbending are applied to the steel pipe with the rotational straightening machine. COPYRIGHT: (C)2010,JPO&INPIT