Why are some argon arc welding primers used in the welding process?

                        There is no difference between the process of complete argon arc welding and argon arc welding. Full argon arc welding is suitable for thin-wall small-diameter pipes (usually DN60 and below, wall thickness 4mm).

                        When the diameter of the pipe is large and the wall thickness is thick, the cover surface should be welded manually by argon arc welding. The purpose of using manual welding to cover the surface is that the pipe diameter is larger. Manual welding can ensure the appearance quality, and the working efficiency is higher than that of argon arc welding. Lower than argon arc welding.

                        The welding process of argon arc welding is used for the welding of water-cooled walls such as boilers, superheaters and economizers. The joint quality is excellent. After radiographic inspection, the height of the weld is above grade Ⅱ.

                        Advantages of argon arc welding


                        (1) Good quality

                        As long as the proper welding wire, welding process parameters and good gas protection are selected, the root can obtain a good penetration, with a uniform penetration and a smooth and clean surface. In the arc welding process of ordinary electrodes, there will be no defects such as solder bumps, insufficient welds, dents, pores and slag inclusions.

                        (2) High efficiency

                        In the first layer of pipeline welding, manual argon arc welding is continuous arc welding. Electrode arc welding is broken arc welding, so manual argon arc welding can increase the efficiency by 2 to 4 times. Since argon arc welding does not produce welding slag, there is no need to clean the welding slag and repair the weld bead, and the speed will be faster. On the surface of the second layer of arc welding protective layer, smooth and tidy argon arc welding is very beneficial to the surface of the arc welding protective layer, which can ensure good fusion between the layers, especially in the welding of small diameter tubes, the efficiency is more obvious With.

                        (3) Easy to master

                        Welding of the root seam of manual arc welding must be carried out by experienced and skilled welders. With manual argon arc welding as the primer, workers who are usually engaged in welding work can master it after a short period of practice.

                        (4) Small deformation

                        In argon arc welding, the heat affected zone is much smaller, so the deformation of the welded joint is small, and the residual stress is also small.

                        Process introduction

                        (1) Welding example

                        The material of the economizer, the tube bundle of the evaporation section, the water cooling wall and the low-temperature superheater is No. 20 steel, and the tube of the high-temperature superheater is 12Cr1MoV.

                        (2) Preparation before welding

                        Before welding, the groove should be grooved at 30°, and the true color of the metal should be polished 15 mm away from the inside and outside of the pipe end. The gap between the pipes is 1~3mm. When the actual gap is too large, the transition layer should first be welded to the side of the pipe groove. The temporary windshield is used to strictly control the wind speed during the welding process. Because the wind speed exceeds a certain range, it is easy to generate stomata.

                        (3) Operation

                        Please use a manual tungsten argon arc welding machine equipped with a high-frequency arc starting device, which can use a high-frequency arc starting device. Arc extinguishing is different from electrode arc welding. If the arc is extinguished too quickly, crater cracks are likely to occur, so during the operation, the molten pool should be led to the edge or the substrate is thick, and then gradually reduce the molten pool and extinguish the arc slowly. Protective gas.

                        For No. 20 steel pipes with a wall thickness of 3 to 4 mm, TIGJ50 filler (08CrMoV for 12Cr1 MoV), tungsten rod diameter of 2 mm, welding current of 75 to 100 A, arc voltage of 12 to 14 V, and shielding gas flow of 8 to 10 L/ min, the power supply type is DC positive connection.