Why should argon arc welding be used for plate and steel structure welding in CNC cutting?

There is no difference between all argon arc welding and argon arc welding in the process of backing.All argon arc welding is suitable for thin-walled and small-diameter pipes to ensure the quality and beauty of weld root.

When the pipe diameter is larger and the wall thickness is thicker,the argon arc welding should be used for backing and covering.The purpose of manual welding is to ensure the appearance quality and the work efficiency is higher than that of argon arc welding,and the cost is lower than that of argon arc welding.

In the welding of water wall,superheater and economizer of boiler by argon arc welding,the quality of joints is excellent,and the grade of welding seam is above grade II after radiographic inspection.

The advantages of argon arc welding backing 

As long as the appropriate welding wire,welding parameters and good gas protection can make the root get good penetration, and the penetration is uniform,and the surface is smooth and neat.There is no weld bead, incomplete penetration,depression,air hole and slag inclusion which are easy to produce in general electrode arc welding.

In the first layer welding of pipeline,manual argon arc welding is continuous arc welding.The efficiency of manual argon arc welding can be increased by 2~4 times.Since no slag will be produced in argon arc welding,it is not necessary to clean up the slag and repair the weld bead,so the speed can be increased faster.In the second layer of arc welding cover, smooth and neat argon arc welding bottom layer is very conducive to arc welding cover,which can ensure good fusion between layers,especially in the welding of small diameter pipe,the efficiency is more significant.

The welding of root weld of manual arc welding must be performed by experienced and highly skilled welders.Manual argon arc welding is used for backing,which can be mastered by workers engaged in welding after a short period of practice.

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

Process introduction

The economizer,evaporation section tube bundle,water wall and low temperature superheater are made of 20 steel, and the high temperature superheater tube is 12Cr1MoV.

Before welding,30° groove shall be made at the pipe orifice,and the metal color shall be polished within 15mm inside and outside the pipe end.The gap between pipes is 1~3mm.When the actual butt gap is too large,it is necessary to weld the transition layer on one side of the pipe groove.Set up temporary wind shelter facilities and strictly control the wind speed at the welding operation site.As the wind speed exceeds a certain range,it is easy to produce air holes.

Manual TIG welding machine is used.The welder is equipped with high frequency arc starting device,which can be used.Arc extinguishing is different from shielded metal arc welding.If the arc is extinguished too fast,it is easy to produce crater cracks. Therefore,during operation,the molten pool should be led to the edge or the thicker base metal, and then the molten pool should be gradually reduced to slowly extinguish the arc,and finally the protective gas should be turned off.
For 20 steel pipe with wall thickness of 3 ~ 4mm, tigj50 (08crmov for 12cr1 mov) can be used as filling material, the diameter of tungsten electrode is 2mm, the welding current is 75 ~ 100A, the arc voltage is 12 ~ 14V, the flow rate of shielding gas is 8 ~ 10L / min, and the power supply type is DC positive connection.