METHOD FOR PREVENTING LONGITUDINAL BEND OF SMALL-DIAMETER PIPE MATERIAL

摘要

PURPOSE:To prevent the generation of a bend in the longitudinal direction of a small-diameter pipe material in the stage of a hardening treatment by subjecting the small-diameter pipe material to a normalizing treatment after rolling then to cold leveling prior to hardening in the stage of producing the small-diameter pipe material of a component system having low hardenability. CONSTITUTION:After the small-diameter pipe material consisting of the component system having the low hardenability is rolled, the material is heated to an adequate temp. above the transformation point such as Ac3 point or Acm point and is held for about >=5min. The heated material is cooled in air to form the finer and more uniform crystal grain sizes. The pipe material is then subjected to leveling in a cold leveling stage prior to hardening to strip and remove the scale generated in the normalizing treatment. The generation of the bend in the longitudinal direction of the pipe is thereby prevented in the stage of hardening the pipe material having a small diametral size.