Popularization and application of stainless steel argon arc welding without argon in the tube
Summary:
The use of flux-cored wire, the back of the argon-free tungsten argon arc welding stainless steel pipe, is a simple and easy process, but also to ensure the quality of the weld and welding process, saving a lot of argon-filled protection, labor, cost Low, high efficiency, and remarkable superiority, it is worthy of installation and promotion.
Overview
Welding equipment selection
Welding quality
When welding stainless steel, because of the great affinity of stainless steel and oxygen, if the back surface is not protected by argon, the molten metal is easily oxidized during the welding process, causing welding defects. Therefore, in the argon arc welding of stainless steel pipes, in order to ensure the welding quality of the back side of the weld, the argon protection measures in the pipe are usually adopted. There are several ways to fill argon:
1.1 Small diameter tube filling argon method
For small diameter pipes, a full tube inflation method can be used. This method of aeration is relatively simple, but as the length of the line increases, argon is wasted. Under normal circumstances, using segmented group welding, a small amount of intermediate joint welding uses soluble paper to block both sides of the welded pipe mouth.
The specific method of filling the whole tube with argon: plug one end of the tube with a cork stopper (the cork center should be marked
1.2 Large diameter pipe filling method
For diameters greater than
Local inflation method should be before welding
1.3 Reverse sliding mode filled with argon and placed soluble paper
For large-diameter pipes and vessels, as long as one can enter the sliding mode to fill the argon, the back-sliding mode is argon-filled in synchronization with the front welding. The reverse side can not use the sliding mode to synchronously fill the argon-filled pipe. The soluble paper can be used to place the soluble paper in the position of the blocking plate, and the argon is filled from the gap of the welding buckle (the gap is affixed with tape, the edge is welded, the tape is removed, and the welding is completed. Welded. The soluble paper is automatically melted during the hydrostatic test.)
The various argon-filled protection methods described above have a long auxiliary time for welding and waste argon gas, which causes many difficulties in field welding. use
Dedicated
Select the Great Wall brand produced by Beijing Electric Welding Rod Factory
C≤0.08 Mn1.0~2.5 Si≤1.0 Cr18~21 Ni9~11 S≤0.03 P≤0.04 σb≥515 MPa δ5≥30% Welding process
4.1 Preparation before welding
4.1.1 Stainless steel nozzle
4.1.2 Angle between welding torch, welding wire and weldment
The angle between the back of the welding torch and the surface of the weldment is too small, which will reduce the argon protection effect. The angle is too large, the visibility is small, and the operation is difficult. The ideal torch nozzle tilt angle is
4.2 Operation points
Horizontal fixed tube welding
During the welding process, the welding gun is slightly oscillated to accelerate the separation of the molten iron and the molten core, which is convenient for observing the molten pool and controlling penetration. When filling the wire, it is best to send it to the molten pool.
Overlap welds are required when changing the wire and grinding the tungsten rod or weld joint
If the arc is improperly closed, it is easy to produce defects such as arc pits and shrinkage holes. Therefore, it is very important to close the arc during operation. When the above defects are found, the defects should be removed and then welded.
The usual argon arc welding equipment has an "attenuation" device. When the arc is closed, the "attenuation button" should be pressed, and the wire feeding amount should be increased. After the welding current is gradually reduced until the arc is extinguished, the welding torch protects the arc for a period of time to make the welding. The seam is not oxidized. If a welder without a "attenuation" device is used, the welding speed is appropriately slowed down when the arc is closed. Immediately after filling the molten pool, the arc is moved to the groove surface, and finally the arc is extinguished.
Achieving a uniform, aesthetic weld depends largely on the correct temperature of the weld pool. When it is found that the molten pool is enlarged and the concave is formed, it indicates that the temperature of the molten pool is too high, and the angle between the welding torch and the workpiece should be rapidly reduced, and the welding speed should be accelerated. When the weld pool is small and the weld is narrow and high, the temperature of the weld pool is low. This is to slightly increase the angle between the welding torch and the workpiece, slow down the welding speed and reduce the amount of wire added.
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