How to weld pipes by argon arc welding

1. welding example: the material of economizer, evaporation section tube bundle, water wall and low-temperature superheater is 20 steel, and the material of high-temperature superheater tube is 12Cr 1MoV.

2. Pre-welding preparation: Before welding, the nozzle should be bevelled by 30, and the inside and outside of the pipe end should be polished within 15mm. The pipe butt clearance is 1~3mm. When the actual butt joint gap is too large, it is necessary to establish a transition layer on one side of the pipe groove first. Set up temporary shelter facilities and strictly control the wind speed in the welding workplace, because the wind speed exceeds a certain range, which is easy to produce blowholes.

3. operation: WST3 15 manual TIG welding machine, which is equipped with high-frequency arc ignition device and can be used. Arc extinguishing is different from covered electrode arc welding. If the arc extinguishing is too fast, it is easy to produce arc pit cracks. Therefore, when operating, lead the molten pool to the edge or thick base material, then gradually reduce the molten pool and slowly extinguish the arc, and finally turn off the shielding gas.

For No.20 steel pipe with a wall thickness of 3~4mm, the filler material can be TIGJ50 (suitable for 12Cr 1 MoV, 08CrMoV), the tungsten electrode diameter is 2mm, the welding current is 75~ 100A and the arc voltage is12 ~/kloc-0.

Extended data

safety regulations

1, the welding site must be equipped with fire prevention equipment, such as sandbox, fire extinguisher, fire hydrant, bucket, etc. Flammable articles shall not be less than 5m away from the welding site. If the specified distance cannot be reached, it can be properly covered with asbestos board and asbestos cloth to prevent Mars from falling into flammable materials.

The distance between the explosive and the welding site shall not be less than 10m. The argon arc welding operation site should have good natural ventilation and fixed mechanical ventilation device to reduce the harm of harmful gas and metal dust in argon arc welding.

2. The manual TIG welding machine should be placed in a dry and ventilated place and operated in strict accordance with the instructions. Before use, the welder should be thoroughly inspected. Make sure there are no hidden dangers before turning on the power. Welding can only be carried out after no-load operation is normal.

In order to ensure the welding machine wiring is correct, there must be a good and firm grounding to ensure safety. On/off of the welding machine power supply is controlled by the switch on the power supply board. It is forbidden to pull the switch by load, so as not to burn the shape contact.

3, should always check the working condition of argon arc welding gun cooling water system, found that the blockage or leakage should be solved immediately, in case of burning torch and affect the welding quality.

4, welding personnel leave the workplace or welding machine when not in use, must cut off the power supply. If the welding machine fails, it should be repaired by professionals, and safety measures such as electric shock prevention should be taken during maintenance. Welding machine should be cleaned at least once a year.

Baidu encyclopedia-argon arc welding