Quality Control of ERW Pipe in Production Process

Statistics show that in the production process, the main factors that affect the quality of erw pipe products are raw materials, welding technology and roll adjustment. The sum of the three effects on the quality of steel pipe products accounts for 80.01%. The roll material, equipment failure, the production environment and other factors in four aspects, the impact on the quality of steel products accounted for 19.99%, belonging to a relatively minor link. Therefore, in the steel pipe production process, the raw materials, welding process and roll adjustment of the three aspects of key control.

1. Raw materials on the quality of steel welding
Causal analysis results of steel pipe scrap show that the main factors that affect the quality of raw materials are the mechanical properties of steel strip instability, steel strip surface defects and large geometric deviation of the three aspects, therefore, should focus on control from these three aspects. Strip surface defects are common sickle bend, wave-shaped, longitudinal nibbling and so on, sickle bend and wavy generally appear in the cold-rolled strip rolling process, is caused by the control of the amount of reduction. In the pipe forming process, the sickle bend and wavy strip will lead to the deviation or overturning, easy to produce welded steel pipe weld, affecting the quality of steel. The bite edge of the strip (ie, the jagged edges of the strip appear to be uneven), usually appear in the slitting belt, resulting from the blunt or sharp edge of the slitting disk blade. Due to the bite of the steel strip, there are local lack of meat from time to time, so that when the strip is easy to produce cracks in the welding, cracks and affect the stability of the weld quality. When the width of the strip is less than the allowable deviation, the squeezing force decreases when the steel pipe is welded, so that the welding of the steel pipe weld.

When the width of the steel strip is larger than the allowable deviation, the extrusion force increases when the steel pipe is welded, and weld defects such as sharp beak, lap or burr appear in the weld of the steel pipe. Therefore, the fluctuation of the 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. For the requirements of the same section wall thickness difference does not exceed the specified value of the steel pipe, which requires a high degree of uniform thickness of the steel pipe, strip thickness fluctuations will be the same volume of steel strip thickness difference exceeds allowable value transferred to the finished steel pipe wall thickness difference, so that a large number of pipe thickness beyond the allowable deviation and sentenced to waste. The fluctuation of the thickness not only affects the thickness accuracy of the finished steel pipe, but also makes the quality of the weld unstable when the steel pipe is welded, because the thickness of the steel strip is different, which causes the steel pipe to be unstable in the welding, the pressing force and the welding temperature.

In addition, due to the existence of steel sandwich, impurities, trachoma and other material defects, but also affect the quality of steel is an important factor. Therefore, before the welding of the steel strip, the surface quality and the geometric dimension of each steel strip should be checked. If the quality of the steel strip does not meet the standard requirements, do not conduct the production so as to avoid unnecessary losses.

2. High-frequency welding on the quality of the pipe
In the process of high-frequency welding of steel pipes, the welding process and process parameters control, the placement of induction coils and the position of the impellers have a great influence on the welding quality of the steel pipe welds. Steel pipe weld gap control steel strip into the welded pipe unit forming roll forming, the orientation of the guide roller, the formation of a circular gap with the open pipe, adjust the squeeze squeeze the amount of rollers, making the weld gap control in 1 ~ 3mm, and the weld two Keep it flat. Weld gap control is too large, will make the welding seam bad fusion and cracking; weld gap control is too small, due to heat is too large, causing the weld burning, molten metal splash, affecting the welding quality of the weld.

3. Roll adjustment of the impact on the quality of steel
Causal analysis of pipe scrap from the figure can be seen, the roller adjustment is a steel pipe operating process. In the production process, the roll damaged or worn serious, the need to replace part of the roll on the unit, or a continuous production of a sufficient number of species, the need to replace the entire roll. At this time should be adjusted roll in order to obtain a good quality steel. Such as the roll is not well adjusted, easily lead to the seam of steel pipe joints, lap welding, edge waves, drum kits and pipe body surface with indentation or scratches, steel ovality and other defects, therefore, roll change should master roll adjustment skill.