DSAW Steel Pipe Prewelding

Pre-welding common problems and disposal methods in pre-welding operations often appear wrong side, the opposite welding tumor, burn through, stomata, splash, poor welding and other shortcomings.
(1) Wrong side
This is the most common pre-welding problems, the wrong side of the tolerance, directly lead to the degradation or obsolete steel. Therefore, pre-welding required to strictly control the amount of wrong side. When the whole or more of the root steel billet shows the wrong side of the tolerance, usually because: a. Open seam adjustment is not in place (joint tendency side); b. Joint pressure roller adjustment is not in place (pressure roller circumferential view Or the diameter of the structural steel pipe is not symmetrical, or the relative diameter of the roller is not consistent), there is no crimping; c. Pre-curved edge is not pre-bending in place, there is a straight edge edge Appearance caused by. When the head or tail of the tube is misaligned, it is usually because of: a. The orientation of the inlet and outlet roller is not right; b. The center of the ring is not right; c. Error; d. Forming is not good (after forming the two corners of the bulb difference between the larger; e. Open slot width above 150mill); f. Hydraulic system caused by the pressure swing.

(2) The opposite welding tumor, burn through
The reverse welding, if the eradication, time-consuming, affecting the production process of the normal; do not eradicate the impact of welding and welding within the welding seam stalk. Burned, affecting the surface welding quality, need to add. The occurrence of negative welding and burn the reason, usually: a. Joint is not tight, there may be hydraulic system pressure is too low; b. Molding is not good, roundness error;c. Pre-welding process parameters are not selected. The welding current and arc voltage must be accompanied by the appropriate welding speed, the line energy is too large or the welding speed is too low, are prone to reverse welding and burn.

(3) Stomata
Pre-weld weld gas larvae L lead to internal defects in the surface welding of DSAW steel pipe. Pre-weld welds are usually due to: a. Maintenance of gas quality is not safe, such as rich in water, pressure flow is not enough, etc.; welding guns show some obstruction, maintenance of gas composition hood uneven, harmful gas into; b The corners are rusty, greasy, etc.

(4) Poor weld forming
Weld forming poor, affecting the sequence of the internal seal function, to ensure that the pipe and pipe fittings will not cause leakage between the loose. DNl25 ~ DN600 of lined plastic composite pipe because of the larger diameter, tighten the thread more difficult, so the use of groove-type pipe joints connected to fulfill the CJ / T156 specification. I produced the trench-type carbon steel pipe joints, the factory had to withstand the 3.75MPa pressure test, 0.08MPa vacuum test and the use of pressure 1.5 times the pressure experiment.