Preheating Technology of DSAW Pipe

Pre - welding technology status
In the early dsaw pipe production was not pre-welded until the second generation of UOE pipe unit began to show a pre-welder, but the moment of pre-welding for the joint welding, the distance of about 300mm, to the UOE pipe unit of the third generation (1968 ~ 1979), pre-welding has been a great focus on and carried out, has not been connected to a series of methods, this period of pre-welding technology for modern pre-welding skills laid the foundation. Modern pre-welding technology selection of a series of high-speed gas maintenance welding (MAG) approach and weld laser stalk, welding speed can reach 7 m / min, bead shape straight and beautiful.

Pre-soldering process
Pre-welding, the first pipe billet joint, followed by a series of gas maintenance welding, welding together with the welding conditions and welding quality monitoring and response. The details of the process are: the import of the roller to withstand the tube - to adjust the direction of the opening of the tube - transport equipment delivery tube blank pipe billet joint - to recognize the quality of joint - welding gun to reduce the preparation of welding - launch laser stalker stalking - open the maintenance of gas and cooling water valve - start welding (tube to the welding speed feed) _ - to the end of the arc quenching - hysteresis off the maintenance of gas - welding gun rise back - tube down the way. At this point, a pre-welding cycle is over. In the above process, adjust the opening orientation of the tube, refers to the opening seam adjustment to the demand direction, usually 12 o'clock position, this work can be controlled by electronic control system in the system. Recognize the quality of joint, that is, the amount of the wrong side of the joint, fit the gap, etc., as long as the recognition can be completed after the stitching and welding. In order to ensure the quality of welding, in the welding before the start, see the special welding torch, timely finishing torch on the splash, may be appropriate spray some anti-splash agent. Pre-welding arc and arc extinguishing are usually carried out on the start-up plate and the extinguishing plate. Pipe length of about 80mm within the shape of the seam in the pre-welding after welding through the technical gas welding.

Pre-welding quality includes seam quality and weld quality.
(1) Joint (that is, forming seam) error-free side or wrong side is less than the rule value, through the conventional error ≤ thickness ≤ 8% of the thickness, the maximum does not exceed 1.5mm.
(2) To ensure that the weld has a suitable penetration depth and welding volume, it is necessary to ensure that after welding does not crack, does not occur burning wear appearance, but also to control the weld height, the weld is not affected.
(3) Welds, forming outstanding, in order to ensure the ultimate quality of the external welding.
(4) Weld does not exist welding bias, pores, cracks, slag, burning and reverse welding and other shortcomings, the need for welding the middle of the error ≤ 1 mm.
(5) No arc burns, small splash, does not affect the tube end groove and appearance quality.
(6) Weld and base metal match, weld metal physical and chemical functions to meet the quality requirements.