The common problems of pre-welding of welded steel tubes, such as erroneous edges, directly lead to the degradation of welded steel tubes or waste materials. Therefore, pre-welding must strictly control the wrong side. When the entire or most of the welded blanks have the wrong edges, the difference is generally due to:
(1) Slit adjustment is not in place;
(2) Joiner rolls (roller adjustment is not on the right side of the circumferential angle, or on the centerline of the tube, the radial roll stretch is approximately asymmetric, or the pressure roll is inconsistent, no pressure circle); Prebend without pre-bend plate in place Feng caused a straight edge phenomenon. When the wrong lateral deviation occurs at the head or tail of the tube blank, it is usually due to the incorrect position of the import/export roller table; the center of the ring is wrong;
(3) Joint pressure rolling circle is not good, individual roller position deviation;
(4) Poor molding (the height of the blank on both sides after forming);
(5) The opening width exceeds 150mm.
(6) Hydraulic system pressure fluctuations. Open slot adjustment is not in place;
2, In the back of the over, after burning and welding if clear and time-consuming, affecting the normal production process; is not clear, steel pipe welding and internal weld tracking welding. Burning, affecting the quality of welding inside and outside, need to be filled. The reasons behind overlap and burning are generally:
(1) The joint is not tight, there may be a low pressure hydraulic system;
(2) Poor molding, large roundness deviation;
(3) Improper selection of pre-welding process parameters. Welding current and arc voltage have proper welding speed, welding speed and line energy are too high or too low, easy to burn and flash back.
3, Stoma
Pre-weld porosity causes internal defects in internal and external welds. The formation of porosity in the pre-weld is generally due to:
(1) Poor protection gas quality, such as insufficient water, pressure and flow;
(2) Part of the welding torch is blocked, the hood formed by the shielding gas is not uniform, and the harmful gas is stirred
(3) There are rust and oil contamination on the tank.
4, Poor formation of welds.
Welded steel pipe welding seam shape is poor, affecting the internal and external welding tracking, affecting the stability of the welding process, thus affecting the welding quality. Welding formation is closely related to the line. Welding current, constant arc voltage, increased welding speed, weld penetration and weld width decrease, resulting in poor weld formation. When air holes are created in the weld, weld formation is generally poor.
