When manufacturing welded pipes for used welded pipe units, judging that the quality of the welded pipes meets the standard depends on the quality of the welds. Therefore, the quality of the weld is very important, so sometimes it is necessary to rule out the quality of the weld. We perform analyses to understand weld quality failures.

These weld quality failures will occur when the used welded pipe units is making pipes: ① through-length lap welding. ② Periodic lap welding. ③ Open the seam. ④ Trachoma. ⑤ Peach-shaped tube. ⑥ Weld seam gnawed. ⑦Outer burr planing. ⑧ Heating. ⑨ The current is small. ⑩ Melting of induction coils and electrodes. ⑪ Fire. ⑫ "No high pressure" phenomenon. We can summarize 12 causes of weld quality failures.

Periodic lap welding

Lap welding occurs intermittently, sometimes absent, sometimes the length of lap welding is slightly longer, a few centimeters or even tens of centimeters, and sometimes it is slightly shorter, ranging from one or two centimeters below. Sometimes the lap welding appears as a relatively regular equidistant, and sometimes it appears irregularly. These lap welding phenomena are collectively referred to as periodic lap welding. Periodic lap welding generally occurs in the middle and late stages of production, mainly due to the following reasons:

(1) The guide ring is broken. When the closed hole pattern is worn, the normal operation of the tube blank cannot be effectively controlled, so that the tube blank swings back and forth in the hole pattern. At this time, after the guide ring is broken and a gap appears, during the operation of the tube blank, the edge will be depressed by the gap of the guide ring, thereby forming the lap welded pipe. The characteristics of this lap welded pipe are that the length of the lap welding cycle is the same, the regularity is strong, and it is relatively easy to judge. Generally, with the rotation of the cracked guide ring, the traces of depression can be found.

(2) The hole type is worn. Mainly refers to the step-like appearance of the bottom diameter of the upper roller of the closed hole type (Figure 21),

And the upper edge of the vertical roll pass of the open pass is stepped (Figure 22).

When the tube blank swings in the hole pattern and slides to the boss of the hole pattern, the edge of the tube blank will produce indentation marks to form lap welding. If it slides in and out instantly, the lap weld will be smaller, and vice versa, the lap weld will be longer. The best way to eliminate this kind of lap welded pipe is to pay attention to reasonable adjustments in normal production, so that the hole pattern wears evenly and avoids the appearance of steps. To completely eliminate the occurrence of lap welding.

(3) Hole-shaped cambered foreign body.Sometimes on the arc surface of the hole type, when other metal foreign objects are adhered to the surface of the tube blank for some reason, indentation scars will appear on the surface of the tube blank. , it will cause short equidistant periodic lap welding. In general, this phenomenon is rare.

(4) Swing seam.In the later stage of production, the wear of the pass is more serious, the control ability of the tube blank is gradually reduced, and the center position of each pass is damaged to varying degrees. Therefore, from forming to welding, there will be a swinging seam phenomenon that the tube blank runs erratically. The lap welding caused by the swing seam is mostly caused by the vertical roll, and the flat roll sometimes also causes some lap welding pipes, but the probability is smaller in comparison. When checking the edge condition of the tube blank, it is also difficult to find any abnormal and obvious pressing defects, and it is not until the extrusion roller that the two edge heights of the tube blank can be felt slightly different. At this time, attention should be paid to the shape of the upper edge of the vertical roll pass. If it is ideal, the shrinkage of the vertical roll can be increased to obtain a perfect tube blank edge deformation effect. If the upper edge of the vertical roll pass is not too good When it is good, it is necessary to reduce the shrinkage of the vertical roller to prevent bad deformation.

(5) The bearing is damaged. After the bearing of the closed hole type is damaged, the smooth operation of the tube blank cannot be well controlled, and the phenomenon of swinging seam is easy to occur, and the possibility of lap welding also follows. Especially after the multi-pass closed-pass bearing is damaged, the problem of lap welding will be more serious. Of course, this phenomenon rarely occurs. Even if it happens, this kind of lap welding is irregular lap welding. The problem cannot be solved by adjustment.

The above is one of the reasons for the quality failure of the weld seam when the used welded pipe units is making pipes, periodic lap welding. The main reasons for the formation of periodic lap welding are (1) the rupture of the guide ring. (2) The hole type is worn. (3) Hole-shaped cambered foreign body. (4) Swing seam. (5) The bearing is damaged.