Improvement measures for bending fracture of 316L stainless steel electric heating tube
During the welding and drawing process of 316L stainless steel electric heating tube, due to the uneven stress and grain deformation, the plastic toughness of the material is reduced. The tensile deformation caused by bending stress is greater than the breaking strength of the material, which will cause bending fracture. We can take corresponding countermeasures in welding, heat treatment and bending process to improve the yield of electric heating tube.
(1) 316L stainless steel has low thermal conductivity and large linear expansion coefficient, and a large temperature gradient will be generated during the welding process, thereby forming welding stress within the material; during the welding process, impurities such as P and S contained in the material itself will be in Low melting point eutectic forms in the molten pool, which is more prone to welding hot cracks and reduces the mechanical properties of the material. Within the allowable welding temperature range, the welding temperature can be appropriately reduced to reduce the influence of welding stress on the material properties;
(2) The grains of 316L stainless steel grow excessively during the welding process and generate welding stress inside the material. Annealing treatment can be performed after welding to reduce the welding stress of the joint, reduce the fracture tendency of the heat affected zone, and promote the dissolution of residual carbide Improve the plasticity of the welding zone.After annealing treatment, surface oxidation treatment can be performed to form a dense protective film on the surface of the material to further improve the corrosion resistance of the material;
3) 316L stainless steel has good elongation and toughness, and is not easy to break during stretching. However, the large columnar grains of the weld and the heat-affected zone will cause poor plastic toughness. In the process of bending the pipe, the weld zone should be avoided to be placed outside the bend (tensile deformation side), which can reduce the plasticity of the weld zone Deformation and bending fracture