What are the factors affecting the quality of high frequency welded pipe production line?

What factors affect the quality of high frequency welded pipe production line? First of all, the welded pipe process is an important link in the high-frequency welded pipe production line, which can directly affect the quality of the products produced. The production process depends on the product variety. From raw materials to finished products, a series of processes are required.

To complete these processes, corresponding mechanical equipment and welding, electrical control and detection devices are required. These equipment and devices are different The typical process flow of high frequency welded pipe production line is uncoiling, strip leveling, head and tail shearing, strip butt welding, looper material storage, forming welding Burr – sizing – flaw detection – flying cutting – preliminary inspection – steel pipe straightening – pipe section processing – hydraulic test – flaw detection – printing and coating – finished products, among which, there are many links that affect the quality of products, so attention should be paid to the work of each link of high frequency welded pipe production line.

 

1、 Raw materials are the main factors affecting the welding quality of high frequency welded pipe production line, mainly including the instability of mechanical properties of steel strip, surface defects of steel strip and large deviation of geometric size. Therefore, the key control measures should be taken from these three aspects.

 

1.1. Influence of mechanical properties of steel strip on quality of steel pipe

 

Carbon structural steel is commonly used for welded steel pipe. If the yield point and tensile strength of steel strip are too high, it will be difficult to form the steel strip in the high frequency welded pipe production line. Especially when the pipe wall is thick, the material has large resilience, and the steel pipe has large deformation stress during welding, and the weld seam is easy to crack. When the tensile strength of the steel strip exceeds 635mpa and the elongation is lower than 10%, the weld of the steel strip is easy to crack 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 in the forming process. Therefore, the mechanical properties of the material have a great impact on the quality of the steel pipe. Therefore, attention should be paid to this source link of the high frequency welded pipe production line The quality of steel pipe can be effectively controlled from the aspect of material strength.

 

1.2. Influence of surface defect of steel strip on quality of steel pipe

 

The common surface defects of steel strip include sickle bend, wave shape and longitudinal shear edge gnawing. Sickle bend and wave shape usually appear in the rolling process of cold-rolled steel strip, which is caused by improper reduction control. In the forming process of steel pipe, sickle bend and wave shape will cause deviation or overturning of strip steel, which is easy to cause overlap welding of steel pipe weld and affect the quality of steel pipe. The biting edge of steel strip (i.e. the jagged unevenness on the edge of steel strip) generally occurs on the slitting belt, which is caused by the blunt or unsharp edge of the disc cutter of the slitting machine. Because of the gnawing edge of the steel strip, the local lack of meat often occurs, which makes the steel strip easy to produce cracks and cracks during welding, thus affecting the stability of the weld quality.

 

1.3. Influence of steel strip geometry size on steel pipe quality

 

When the width of the steel strip is less than the allowable deviation, the extrusion force decreases when welding the steel pipe, which makes the welding of the steel pipe not firm and cracks or open pipes appear; when the width of the steel strip is greater than the allowable deviation, the extrusion force increases when welding the steel pipe, and welding defects such as sharp nozzle, overlap welding or burr appear at the weld joint of the steel pipe. Therefore, the fluctuation of the width of the steel strip not only affects the accuracy of the outer diameter of the steel pipe, but also seriously affects the surface quality of the steel pipe.

 

2、 High frequency welding also affects the quality of steel pipe. In the high frequency welding process of high frequency welded pipe production line, the control of welding process and process parameters, the position of induction ring and impedance device have great influence on the welding quality of steel pipe weld.

 

3、 The influence of roll adjustment on the quality of steel pipe in high frequency welded pipe production line can not be ignored. Roll adjustment is a kind of operation technology of steel pipe. In the production process, when the roll is damaged or worn seriously, it is necessary to replace some rolls on the unit, or a certain type of continuous production has enough quantity When changing a complete set of rollers, the roller should be adjusted to obtain good steel pipe quality. If the roller is not adjusted properly, the defects such as torsion of pipe seam, overlap welding, edge wave, bulge, indentation or scratch on the surface of pipe body, and large ovality of steel pipe are easy to cause. Therefore, the skills of roll adjustment should be mastered when changing rolls.