Stress relief annealing of seamless steel pipe

Stress relief annealing of seamless steel pipe: annealed to remove stress and residual stress in the casting of memory due to plastic deformation processing, welding, etc. caused by the conduct referred to as stress relief annealing.

Cold drawn seamless steel pipe deformation (stress relief annealing phase transition does not occur), can not reach the surface finish and dimensional accuracy requirements, they can not achieve strength index components; deformation is too large, seamless steel ductility, toughness reduce excessive Moreover, elongated grains excessively pulled, the formation of fibrous tissue, metals having a significant anisotropy. Cold drawn seamless steel tube axially parallel to the elongated direction of the grain, increased strength; cold drawn seamless steel pipe radially, perpendicular to the elongated direction of the grain, but lower strength, maximum stress and the hydraulic cylinder being present in the radial direction of seamless steel tubes on, so much to give full play to the deformation properties of cold drawn tubes unfavorable. For the fibrous tissue that appears in the steel and dislocations, vacancies and other crystal defects are generally taken annealing or normalizing heat treatment methods to eliminate them. The purpose is to refine the grain annealing, eliminating tissue defects, reduced hardness, improved ductility, but also facilitate cold.

Process of stress relief annealing: the workpiece was slowly heated to Ac 1 or less 100 ~ 200 ℃ (500 ~ 600 ℃) holding a certain time (1 ~ 3h) followed by slow furnace cooling to 200 ℃, baked and then cooled. Steel is generally 500 ~ 600 ℃,Iron is generally 500 ~ 550 ℃ likely to cause pearlite graphitization than 550. Weldment generally 500 ~ 600 ℃.

Scope: the elimination of casting, forging, welding parts, cold stamping and machining the workpiece residual stress in order to stabilize the size of steel, reducing distortion and prevent cracking.

Purpose: cold drawn seamless steel pipe were needed after stress relief annealing, to eliminate the residual stress of the material, improve the organization of materials, improved plastic material, so as to achieve the purpose of preventing seamless steel pipe fracture failure occurs.

Seamless pipe Specification, standard and identification

Seamless pipes are extensively applied for the nuclear device, gas, petrochemical, ship building and boiler industries. Seamless pipes dominates 65% of market share in Chinese boiler industry.