During CO2 welding, the following three types of pores may be produced

(1) CO porosity. The reason is that the welding wire deoxygenation is insufficient, so that a large number of FeO can not be reduced and melted in the metal pool, solidification and C react to generate Fe and CO,CO gas too late to escape, forming pores. Ensure that the welding wire has enough deoxidized elements, strictly control the carbon content of the welding wire, can reduce CO pores.

    (2) Nitrogen pores are caused by poor protection of CO2 airflow or low purity of CO2 gas (containing a certain amount of air). When a large amount of nitrogen is melted in the metal pool and the weld metal crystallizes and solidifies, the melting degree of nitrogen in the metal suddenly decreases and there is no time for it to escape, thus forming pores. The factors affecting the poor CO2 protection are too small CO2 gas flow, too fast welding speed, wind in the welding site, etc. Effective measures can be taken to prevent the formation of nitrogen pores.

    (3) The formation process of hydrogen stomata is the same as that of nitrogen stomata. The source of hydrogen is related to the rust, moisture, oil and other sundries on the surface of weldment, wire, CO2 gas and water content. Strictly clean up the debris on the surface of welding parts and wires, and use CO2 gas after purification, which can effectively prevent the generation of hydrogen pores.

The causes of air holes are generally: welding process, welding torch is too high; Welding torch nozzle splash plug; The distributor valve is damaged or not installed; Insufficient gas flow and pressure; Gas mismatch; Material water, rust, oil and other sundries; The welding environment is windy; Welding gun aging damage leakage; Personnel skills are insufficient, the above is caused by pores.

Measures to prevent pores:

 1.Select appropriate welding parameters according to material characteristics, plate thickness and groove type to maintain the stability of welding process and reduce the generation of pores.

 2.Select wire, flux and protective gas suitable for the base metal, clean up oil, rust and oxide and other sundries within 20 ~ 30mm on the groove and both sides before welding, to ensure smooth air path and wire feed structure.

 3.According to the actual situation, preheat the workpiece before welding, select the appropriate welding speed, at the end of welding and welding stop, should be slowly withdrawn from the welding pool, so that the pool slowly cooling, so that gas fully escape from the pool, reduce the generation of pores.

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