The influence of raw materials on welding quality in ERW steel pipe production mainly includes three aspects: unstable mechanical properties of steel strip, surface defects of steel strip and large deviation of geometric dimensions. Therefore, it is necessary to control the key from these three aspects.
1) The influence of mechanical properties of steel strip on the quality of steel pipe. The common steel used in welded steel pipe is carbon structural steel. The main grades are Q195, Q215, Q235 SPCC SS400 SPHC, etc. The yield point and tensile strength of steel strip are too high, which will lead to the difficulty of forming steel strip. Especially when the pipe wall is thicker, the elasticity of the material is bigger, the deformation stress of the pipe is bigger in the welding process, and the weld is prone to crack. When the tensile strength of steel strip exceeds 635 MPa and the elongation is less than 10%, the weld is easy to crack during welding. When the tensile strength is less than 300 MPa, the steel strip is easy to wrinkle because of the soft material in the forming process. It can be seen that the mechanical properties of materials have a great impact on the quality of steel pipes, and the quality of steel pipes should be effectively controlled from the aspect of material strength.


2) The influence of surface defects on steel tube quality There are several types of surface defects of steel strip, such as sickle bending, wave shape, longitudinal shear edge, etc. Document bending and waveform usually occur in cold strip rolling process. The reduction of control leads to improper control. In the process of steel tube forming, drilling and wave shape will lead to strip falling off or overturning, easy to cause lap welding of steel tube weld, and affect the quality of steel tube.  The edge of the strip (i.e., the edge of the strip is serrated and uneven), which usually occurs on the longitudinal cutting strip and is caused by the blunt or non-sharp edges of the cutter head. Because of the edge of the steel strip, the local shortage of meat occurs from time to time, which makes the steel strip prone to cracks and cracks in the welding process, and affects the stability of welding quality.


3) The influence of strip geometry size on the quality of steel pipe. When the width of steel band is less than the allowable deviation, the pressure of welded steel pipe decreases. Therefore, the welded joint steel pipe is not firm and the cracked or open pipe is steel strip. When the width is larger than the allowable deviation, the pressure increases when the steel pipe is welded, and welding defects such as overturning, lap welding or burr appear at the welded joint of the steel pipe. Therefore, the fluctuation of steel bandwidth not only affects the accuracy of steel tube outer diameter, but also seriously affects the surface quality of steel tube.