Measures to deal with common problems of straight seam steel pipe pre-welding

1. Wrong side.
This is a common problem in pre-welding. Misalignment of edges will directly lead to the downgrading or scrapping of steel pipes. Therefore, it is required to strictly control the amount of edge deviation during pre-welding. When the entire or more than half of the steel pipe blank appears to be out of tolerance, it is usually due to:
1) The opening seam is not adjusted in place;
2) The seaming pressure roller is not adjusted in place (the circumferential angle of the pressure roller is wrong, or the center line of the tube blank is used as the axis, the left and right pressure rollers are asymmetrical, or the radial elongation of the opposite pressure rollers is inconsistent), and there is no rounding. ;
3) The pre-bent edge is not pre-bent in place, which is caused by the phenomenon that the edge of the board is full of the straight edge. When the head or tail of the tube blank is out of tolerance, it is usually due to;
1) The position of the inlet and outlet rollers is wrong;
2) The center of the ring frame is wrong;
3) The seam-joining pressure roller is not rounded well, and the position of individual pressure rollers is deviated;
4) Poor forming (the height difference between the two sides of the formed tube blank is large;
5) The opening seam width is more than 150mm);
6) Caused by pressure fluctuations in the hydraulic system;

2. Welding blemishes and burn-through on the back.
The welding burr on the back side affects the normal production process; it affects the welding shape of the internal welding and the tracking of the internal welding seam. Burn-through affects internal and external welding and needs to be filled. The causes of welding spatter and burn-through on the back are generally ① the joint is not tight, or the pressure of the hydraulic system is too low; ② the molding is not good and the roundness deviation is large; ③ the pre-welding process parameters are improperly selected. The welding current and arc voltage must be matched with an appropriate welding speed. If the line energy is too high or the welding speed is too low, it is easy to produce back welding nodules and burn-through.

3. Stomata.
Pre-weld weld porosity causes internal defects in both internal and external welds. The pores produced in pre-welded welds are generally due to ① poor shielding gas, such as containing moisture, insufficient pressure and flow, etc.; ② partial blockage of the welding gun, resulting in an uneven gas mask formed by the shielding gas, and harmful gases disturbing people; ③ rust, Caused by oil pollution, etc.

4. Poor weld formation.
Poor welding seam formation affects the subsequent internal and external welding tracking, affects the stability of the welding process, and thus affects the welding. Welding seam formation is closely related to line energy. As welding current, arc voltage, and welding speed increase, welding seam penetration depth and width decrease, resulting in poor welding seam formation. When pores occur in the weld, poor weld formation often occurs.

5. Splash.
Spatter during pre-welding can easily burn the surface or groove of the steel pipe and is not easy, thus affecting the welding and outer surface of the steel pipe. The main reason for splashing is that the protective gas composition is incorrect or the process parameters are incorrect. The proportion of argon in the protective gas should be adjusted.