The straight seam welded pipe needs to be carried out according to the strict production process in the production process. If the production process is unreasonable or the production equipment is used improperly, deviation will occur, which is called "wrong side". The wrong side is the most common problem in pre-welding, and the wrong side is out of tolerance, which directly leads to the degradation or scrapping of the steel pipe. Therefore, it is required to strictly control the amount of misalignment during pre-welding. When the whole or most of the steel tube billets are out of tolerance, it is generally due to:
1) The adjustment of the opening seam is not in place (the seam is biased to one side);
2) The seam pressure roller is not adjusted properly (the circumferential angle of the pressure roller is wrong, or the center line of the tube blank is the axis, the left and right pressure rollers are asymmetric, or the radial elongation of the opposite pressure roller is inconsistent), there is no pressure round ;
3) The pre-bending edge is not pre-bent in place, and the plate edge has a straight edge phenomenon.
When the head or tail of the tube blank is out of tolerance, it is generally due to:
1) The position of the import and export roller table is wrong;
2) The center of the ring frame is wrong;
3) The seam pressure roller is not well rounded, and the position of individual pressure rollers is deviated;
4) The forming is not good (the height difference between the two sides of the formed tube blank is large);
5) The width of the opening seam is more than 150mm;
6) Caused by the pressure fluctuation of the hydraulic system.
In recent years, due to the high yield, low price and gradual improvement of performance of straight seam welded pipes, more and more straight seam welded pipes are used instead of seamless steel pipes in industrial production. Straight seam welded pipe refers to the steel pipe obtained by straight seam welding of hot-rolled or cold-rolled steel plate or steel strip coil welding on welding equipment. It is widely used in water engineering, petrochemical industry, chemical industry, electric power industry, and agricultural irrigation. , urban construction, etc.