Research Method of ERW Pipe Welding Rod

It is mainly manifested in three aspects: unstable mechanical properties of strip steel, surface defects of strip steel, and large deviation of geometric dimensions. Therefore, focus on control should be carried out from these three aspects.

1) The influence of the mechanical properties of the steel strip on the quality of the steel pipe The commonly used steel grades for welded steel pipes are carbon structural steels, and the main grades are Q195, Q215, Q235 SPCC SS400 SPHC, etc. If the yield point and tensile strength of the steel strip are too high, it will be difficult to form the steel strip, especially if the pipe wall is thick, the material will have a large resilience, and the deformation stress of the steel pipe will be large during processing. Welding, welds are prone to cracks. When the tensile strength of the steel strip exceeds 635MPa and the elongation is lower than 10%, the weld of the steel strip is prone to cracks during welding. When the tensile strength is lower than 300MPa, the surface of the steel strip is easy to wrinkle 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 in terms of material strength.

2) Effect of surface defects of strip steel on steel pipe quality Common surface defects of strip steel include arc, wave, slitting and undercut, etc. Arc bending and wave generally appear in the cold rolling process. The rolled steel strip is caused by improper control of the reduction. During the forming process of the steel pipe, the sickle-shaped bending and wavy shape will cause the strip steel to deviate or turn over, which will easily cause the weld seam of the steel pipe to overlap and affect the quality of the steel pipe. Undercutting of the steel strip (that is, the jagged and uneven phenomenon on the edge of the steel strip) generally occurs on the slitting belt. The reason is that the disc blade of the slitting machine becomes blunt or not sharp. Due to the undercut of the steel strip, local lack of meat occurs from time to time, which makes the steel strip prone to cracks and cracks during welding, which affects the stability of the weld quality.

3) The influence of the steel strip geometry on the steel pipe quality When the steel strip width is less than the allowable deviation, the extrusion force of the steel pipe will decrease during welding, making the welded seam of the steel pipe weak, cracks or open pipe; when the width of the steel strip steel pipe When the deviation is greater than the allowable deviation, the extrusion force of the steel pipe during welding will increase, and welding defects such as cusps, lap welding or burrs will appear at the weld 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 Steel pipe surface quality. For steel pipes that require the wall thickness difference of the same section not to exceed the specified value, that is, steel pipes that require high wall thickness uniformity, the fluctuation of steel strip thickness will transfer the allowable value. . , so that the wall thickness of a large number of steel pipes exceeds the allowable deviation and is scrapped. The fluctuation of the thickness not only affects the thickness accuracy of the finished steel pipe, but at the same time, due to the different thickness of the steel strip, the extrusion force and welding temperature of the steel pipe during welding are unstable, resulting in unstable weld quality during welding of the steel pipe.