News - Yooheart robot tell notices of the protective gas welding

Gas shielded welding refers to the welding method protected by carbon dioxide or argon, without the use of welding wire. The gas shielded welding process is suitable for the welding of various large-scale steel structure projects such as low-carbon steel and low-alloy high-strength steel. It has high welding productivity, good crack resistance, small welding deformation, and a large deformation range. Welding of thin plates and medium and thick plates is possible.

Various welding methods of gas shielded welding

1. vertical up welding

The position of the welding torch is very important when welding vertically, and the welding torch should be roughly perpendicular to the workpiece. During straight-line welding, the weld bead tends to be convex, and the appearance of the weld bead is poor and easy to undercut.

During multi-layer welding, the back fill bead is easy to be impervious to welding, so it is generally not used. Therefore, the upward vertical welding usually swings, and the swing method is a small swing. Since the heat is concentrated at this time, the weld bead is easy to bulge, so it should move up quickly under the condition of uniform swing.

If a larger welding leg is required, the crescent swinging method should be used to move quickly in the center of the weld bead and stay a little on both sides to prevent undercut. However, care should be taken not to use a downwardly curved crescent swing.

2. vertical down welding

In the downward vertical welding, in order to maintain the molten pool, the welding torch should point diagonally downward to the molten pool and maintain a certain angle. The arc should always be aimed at the front of the molten pool, otherwise, once the molten iron flows to the front of the arc, it is easy to cause welding lumps and non-penetration. Pool metal pushed up.

Causes of porosity in gas shielded welding

Bad protective gas

1. The quality of the gas in the gas cylinder is not good, and it does not have a purity of more than 98%. It contains harmful gases such as nitrogen, which cause pores after welding.

2. The gas pipeline from the gas cylinder to the welding torch is not tight, and the air is brought in to produce pores.

3. Air turbulence produces stomata

a. The wind in the external environment disturbs the protective airflow around the molten pool

b. Low gas flow or splatter clogging the nozzle

c. The angle of the welding torch is too large or the welding torch is too far from the workpiece

d. The gas shunt ceramic guide ring of the torch nozzle is damaged and has not been removed or replaced

4. Welding machine control air valve opens lag, closes early, or is in poor contact intermittently

Defects in welding wire and base metal itself

1. The solid core welding wire is rusted, oily, etc.

2. The inner powder of the flux-cored welding wire is damp, and the outside is rusted.

3. There are pores in the base metal itself, or there is a lot of oil pollution inside, or the metal quality changes caused by long-term use in chemical environments, such as chemical pipelines, machine tool cast iron and cast steel parts.

4. There are pollutants or water that produce harmful gases in the welding area, and they are not cleaned up

Unreasonable welding parameters

If the current and voltage configuration is too large, it is easy to decompose carbon dioxide into carbon monoxide in a high heat and high ionization environment when the heat input is large, and carbon monoxide pores will be generated when the weldment cools quickly.

Solution suggestion

1. Add argon or carbon dioxide mixed gas to test whether the carbon dioxide gas is impure, and observe whether the mixed gas has a better protective effect. If yes, change the gas supply unit with good quality.

2. Under the protection of mixed gas, there are still pores to eliminate the cause of the gas, and other reasons can be checked visually.

3. It is best not to ignore the problems of the base metal and the welding wire itself.

Post time: Nov-01-2022