1.1 this code stipulates the welding process requirements, welding parts inspection and operation safety of argon arc welding.

 

1.2 this code is applicable to all personnel engaged in welding of corrugated compensators.

 

2. Welding terminology

 

2.1 base material: the general term for the metal materials to be welded.

 

2.2 weld: the joint part formed after welding of the welding part.

 

2.3 toe welding: junction between weld surface and base material.

 

2.4 weld width: the distance between the welding toes on the weld surface.

 

2.5 weld length: length of weld along the axis direction.

 

2.6 weld pool: the liquid metal part with certain geometric shape formed on the welding part under the action of welding heat source during welding.

 

2.7 deposited metal: weld metal formed by the fusion of filler metal.

 

2.8 melting depth: the melting depth of base metal or previous weld on the cross section of welded joint.

 

2.9 excess height: the maximum height of the weld metal beyond the base metal surface line.

 

2.10 weld bead: a single weld formed by each deposition.

 

3. The material

 

3.1 materials shall meet technical requirements.

 

3.2 the material shall have good surface quality, smooth, smooth, no rust and other defects, and the size and thickness shall meet the requirements.

 

4. Equipment and tools

 

4.1 equipment: argon arc welding machine and argon gas bottle.

 

4.2 tools: steel tape measure, vernier caliper, etc.

 

5. Process preparation

 

5.1 welders shall wear labor protection products as required by the workshop, such as anti-smashing safety shoes, welding leather gloves, masks, masks, etc.

 

5.2 the operator understands the performance and operation requirements of the equipment. Before welding, check whether the equipment, instrument, gas cylinder and other process equipment are normal. The grounding wire of the welding machine is firm and reliable.

 

5.3 argon arc welding adopts the direct current positive connection method, that is, the welding part is connected to the positive pole of the power source and the welding gun is connected to the negative pole of the power source.

 

5.4 the welding parts must be cleaned before welding, strictly remove oil (acetone treatment) and remove oxidation film and impurities (steel wire brush, file, sandpaper polishing).

 

6. Process specification

 

6.1 welding torch

 

The function of the welding gun is to clamp tungsten electrode, conduct welding current, output argon flow and start or stop the working system of the welding machine.

 

The welding gun can be divided into air-cooled type and water-cooled type according to the cooling mode. When the welding current used is less than 150A, choose the air-cooled welding gun

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

6.3 arc voltage

 

Arc voltage is mainly determined by arc length. The increase of arc length is likely to produce defects of incomplete welding and make the protection effect worse. Therefore, the arc length should be controlled as far as possible without short circuit of arc. The general arc length is approximately equal to the tungsten electrode diameter.

 

6.4 welding speed

 

The welding speed is usually adjusted by the welder according to the size and shape of the weld pool and the welding piece fusion status at any time:

 

Too fast welding speed will destroy the gas protection atmosphere, welding seam is easy to produce lack of penetration and porosity;

 

When the welding speed is too slow, the weld will burn through and bite the edge easily.

 

6.5 argon flow and nozzle diameter

 

The size of nozzle diameter directly affects the scope of the protection zone.

 

According to production experience: 2 times tungsten electrode diameter plus 4mm is the selected nozzle diameter.

 

When the flow rate is appropriate, the molten pool is stable, the surface is bright and slag free, no trace of oxidation, and the welding seam is beautiful.

 

Improper flow rate, slag on the surface of molten pool, blackening or oxide skin on the surface of welding seam.

 

The proper flow of argon is 0.8 ~ 1.2 times the nozzle diameter.

 

6.6 distance between nozzle and welding parts

 

The distance between nozzle and welding parts should be 8 ~ 14mm.

 

Too large distance, gas protection effect is poor; If the distance is too small, although it is beneficial for gas protection, the observation range and protection area become smaller.

 

6.7 extension length of tungsten electrode

 

In order to prevent arc heat from burning out the nozzle, the tungsten extreme part should protrude beyond the nozzle, and its extension length is generally 3 ~ 4mm (depending on welding needs).

 

The extension length is too small, the welder is not easy to observe the melting condition, unfavorable to the operation;

 

If the extension length is too large, the gas protection effect will be affected to some extent.

 

7. Process

 

7.1 power on

 

Check whether the operation control board power indication is correct and the cooling fan is running normally.

 

7.2 test gas

 

Put on the test switch to verify whether the protective gas is unblocked;

 

Adjust shielding gas flow to meet welding requirements.

 

7.3 arc

 

Usually the manual argon tungsten arc welding machine itself has an arc ignition device (high voltage pulse generator or high frequency oscillator), the tungsten electrode does not contact with the welding piece to maintain a certain distance, can directly ignite the arc on the welding spot.

 

If there is no arc ignition device, pure copper plate or graphite plate can be used as arc ignition plate to conduct arc ignition on it, so that the tungsten extreme head is heated to a certain temperature (about 1s), and immediately move to the welding site for arc welding. This contact will produce a large short circuit current, which will easily burn the tungsten end.

 

When spot welding is started, the base material is heated by arc first, and welding wires are added immediately after the molten pool is presented.

 

7.4 are-receive

 

Generally, the argon arc welding machine is equipped with automatic current attenuation device, when arc closing, the arc pit is filled by intermittent transmission of electricity through the button on the welding gun handle. If there is no current attenuation device, manual operation can be used to close the arc, the main point is to gradually reduce the heat of the welding parts, such as changing the Angle of the welding gun, slightly elongate the arc, intermittent power transmission, etc. When arc closing, after filling the arc pit, slowly lift the arc until arc extinguishing, do not suddenly pull off the arc.

 

After arc extinguishing, the welding gun should stay for 3 ~ 5 seconds to continue to protect the uncooled welding seam with argon gas and accelerate the cooling to prevent the oxidation of the metal at high temperature.

 

Before the end of welding, a little more wire should be added to prevent weld pits after the end is cooled.

 

8. Quality inspection

 

8.1 welding spot and weld quality inspection

 

Solder joint appearance is round or oval, solder joint is not allowed to crack, burn through and other defects.

 

Weld surface should be smooth, no cracks, slag inclusion, welding burners, holes and other defects are allowed.

 

The shape and size of welding seams should meet the requirements of product drawings and technical documents.

 

8.2 workpiece quality inspection

 

The geometric dimensions of the workpiece after welding should meet the requirements of product drawings and technical documents.

 

Clean the spatter on the workpiece without affecting the later process.

 

The workpiece is solidly welded and not easily deformed.

 

8.3 common welding defects are shown as follows:

 

9. Safety and precautions

 

9.1 the welder shall be installed in a place with low humidity and little dust as far as possible, away from heat source and inflammable explosive materials.

 

9.2 the operator shall strictly comply with the requirements of welder safety technical regulations and wear gloves, masks, masks and other labor protection products.

 

9.3 check the power supply in the operation area regularly. Check whether the wires and switches are damaged or leakage. If there is any, timely report for repair.

 

9.4 before the beginning of welding, argon gas shall be used to blow out the water in the air pipe before welding.

 

9.5 argon pressure shall be set at 0.01 ~ 0.05mpa. Argon gas shall be pumped 3 ~ 5 seconds in advance during arc ignition and stopped 6 ~ 7 seconds after arc quenching.