The annealing of the steel pipe is heated to the phase transition temperature of the phase transition or in part, after heat treatment method of slow cooling after incubation. The purpose of annealing is to eliminate the organizational defects, improving the organization to make the uniform composition and grain refinement to improve the mechanical properties of the steel pipe to reduce the residual stress; can reduce hardness and improve ductility and toughness, and to improve the cutting performance.
So annealing both in order to eliminate and improve organizational defects and internal stress left over from the previous process, to prepare for the follow-up process, so annealing is a semi-finished heat treatment, also known as pre-heat treatment.