1. In the production process of ERW steel pipe, how to ensure that the product quality meets the requirements of technical standards and the needs of customers? An analysis of the factors that affect the product quality during the production of steel pipes. According to the statistics of non-conforming products of Φ76mm high-frequency welded steel pipe unit in a certain month, it is believed that the factors that affect the quality of steel pipe products during the production process are raw materials, welding process, roll adjustment, roll material, equipment failure, production environment, and other reasons. aspect. Raw materials accounted for 32 .44%, below will introduce the infect of material to ERW steel pipe.
The influence of raw materials on the ERW steel pipes. The factors that affect the quality of raw materials are mainly the three aspects of the unstable mechanical properties of the steel strip, the surface defects of the steel strip and the large deviations in geometric dimensions. Therefore, we should focus on these three aspects.
1. The influence of the mechanical properties of steel strips on the quality of steel pipes. The common steel used for welded steel pipes is carbon. The main brands of structural steel are Q195, Q215, Q235 SPCC SS400 SPHC, etc. The high yield point and tensile strength of the steel strip will make it difficult to form the steel strip, especially when the pipe wall is thick, the material has a large rebound force, the steel pipe has a large deformation stress during the welding process, and the weld seam is prone to cracks. When the tensile strength of the steel strip is greater than 635 MPa and the elongation is less than 10%, the weld seam is liable to crack during the welding process. When the tensile strength is lower than 30 MPa, the surface of the steel strip is easily wrinkled due to the soft material during the forming process. It can be seen that the mechanical properties of materials have a great influence on the quality of steel pipes, and the quality of steel pipes should be effectively controlled from the perspective of material strength.
2) The influence of surface defects of steel plates on the quality of steel pipes
Common surface defects of steel strips include sickle bending, wave shape, longitudinal shear bite, etc. The sickle bending and wave shape usually appear during the rolling of cold-rolled strip, which is caused by improper reduction control. During the steel tube forming process, sickle-shaped bending and wave deformation will cause the steel plate to deflect or overturn, which may easily cause overlap welding of steel pipes and affect the quality of steel pipes. Edge banding of steel strips usually occurs on longitudinal shear bands, which are caused by blunt or sharp disc blades for longitudinal shear. Due to the bite of the edges of the steel strip, this makes the steel strip easy to crack and crack during the welding process, and affects the stability of the welding quality.
3) When the width of the steel strip is less than the allowable deviation, the influence of the geometrical dimensions of the steel strip on the quality of the steel pipe reduces the extrusion pressure during welding of the steel pipe, which makes the welding of the steel pipe unstable, cracks or openings appear; When the tolerance is allowed, the extrusion pressure during the welding of the steel pipe will increase, and sharp nozzles, welding defects such as lap welding or burrs will appear at the welding place of the steel pipe. Therefore, the fluctuation of the steel strip width not only affects the accuracy of the outer diameter of the steel pipe, but also seriously affects the surface quality of the steel pipe. Before welding, the surface quality and geometric dimensions of each coil shall be checked. If the quality of the steel strip does not meet the standard requirements, production shall not be carried out to avoid unnecessary losses.
