Submerged arc welding is an important welding method. Its inherent advantages of stable welding quality, high welding productivity, no arc and little smoke make it an important steel structure in the production of pressure vessels, pipe sections, box beams and columns. the main welding method.In recent years, although many new welding methods with high efficiency and high quality have appeared successively, the application field of submerged arc welding has not been affected in any way. From the perspective of the weight share of deposited metal for various fusion welding methods, submerged arc welding accounts for about 10% and has not changed much over the years.
Therefore, in the production process of SSAW steel pipe, the following three process defects often occur.
1)Defects in the handling of heated parts.In the thermal process, proper and effective heat treatment heating equipment and heating medium must be selected. If the heating temperature exceeds the process requirements, the surface of the parts will be affected by the oxidizing heating medium, which will easily cause product defects.In addition, problems such as excessively coarse grains and even melting of grain boundaries during the heating process of parts will seriously affect the appearance and internal quality of the steel pipe.
2)The case hardening defect is the overall heat treatment of the part, and the required hardness and requirements can be obtained both inside and outside the part. Case hardening is only used for surface hardening of the part, the core is still in its structural state before treatment.Therefore, attention should be paid to factors such as surface quenching temperature, heating time, and depth of hardened layer, which will greatly affect the characteristics of the spiral steel pipe and reduce its service life.
3)Defects in chemical heat treatment of diameter helical tubes. The chemical heat treatment of the spiral tube is a heat treatment process in which the metal or non-metallic atoms on the surface of the part penetrate to obtain the desired surface properties (such as high wear), which endows the part with dual functions and roles.However, if the process formula and process parameters are changed improperly, the parts will be deformed and cracked, and the structure and hardness will be unqualified. Therefore, full attention should be paid to the chemical heat treatment of parts, otherwise the significance of chemical heat treatment of parts will disappear completely.