Causes of porosity

1. Base metal is dirty, the groove edge is not cleaned

2. The composition and properties of the welding materials used are quite different from those of the base metal

3. Welding shielding gas problem

a) Insufficient argon pressure in the cylinder;

b) Excessive adjustment of welding gas flow;

c) Air leakage of air supply pipe;

d) The purity of argon is not enough, resulting in harmful gas mixing into the molten pool;

e) The welding arc is too long, resulting in insufficient effective distance of protective gas hood;

f) The tungsten electrode extends too long, resulting in insufficient effective distance of the protective gas hood;

g) Tungsten electrode rolling head or rolling head sleeve is burned by electric arc, resulting in disturbance of protective air flow;

h) The gas outlet of the welding gun is blocked by foreign matters, and the air flow is not smooth, resulting in the decrease of the protective gas flow;

i) Improper wind protection measures, such as ventilation at the welding site, damaging the protective airflow hood.

4. Welding operation problems

a) Welding gun angle is too large;

b) During operation, when using the argon arc welding gun with control button, the gas is not bled before welding, resulting in instantaneous excessive gas flow during arc striking.

5. Welding process problems

a) Welding speed is too fast;

b) Incorrect arc extinguishing method;

c) Improper welding current.

Preventive measures

1.Clean the base metal surface, residual oil, water and rust on the surface, and polish the groove surface and 10mm on both sides of the groove

2. Select the matching welding materials

3. Welding shielding gas problem

a) Check whether the bottle valve is fully opened. If it is fully opened, it means that the argon in the bottle is insufficient and the bottle needs to be replaced.;

b) Readjust the protective gas flow;

c) Check whether there is air leakage in the air supply pipe;

d) When welding carbon steel, the purity of argon shall not be less than 99.7%, when welding aluminum, it shall not be less than 99.9%, and the purity of argon used for welding titanium and titanium alloy shall be as high as 99.99%.;

e) Adjust proper welding arc;

f) Adjust the extension length of tungsten electrode;

g) Timely replace the tungsten electrode rolling head or rolling head sleeve;

h) Clean the air outlet of the welding gun in time;

i) When the wind speed >2m/s, wind proof measures shall be taken. When welding the pipe, the pipe orifice shall be blocked to avoid the formation of ventilation in the pipe.

4. Welding operation problems

a) Adjust the welding gun angle;

b) During operation, when argon arc welding gun with control button is used, gas shall be released before welding.

5. Welding process problems

a) Adjust proper welding speed;

b) During arc extinguishing, the arc extinguishing method of reducing current or adding welding wire, bringing the arc to the groove side and lowering the arc shall be adopted. Do not stop the arc suddenly, which will cause the high-temperature

molten pool to be separated from the effective protection of argon gas flow, and avoid the occurrence of pores or shrinkage cavities in the arc pit.

c) Adjust the welding current to appropriate parameters. If the welding current is too small, the arc is unstable, the arc drift at the end of the tungsten electrode is unstable, damaging the protection zone, and the welding current is too large, the arc

disturbs the air flow, and the protection effect becomes worse.