Main method for preventing air holes in welding process of pressure vessel

1. Technological measures

(1) Eliminate the sources of various gases. Remove oxide film or rust, dry electrode and flux according to regulations and keep it reasonably, remove oxygen, hydrogen and nitrogen in protective gas.

(2) Strengthen protection. Electrode coating should not fall off, flux or protective gas can not be interrupted, arc should not be arbitrarily stretched, the assembly gap should not be too large, with low hydrogen electrode to use short arc, DC reverse connection.

(3) Correctly master welding operation technology. Create favorable conditions for gas to surface in the molten pool and preheat if necessary.

2, metallurgical measures to choose suitable for the base metal electrode flux.

(1) The oxidant and deoxidizer in the flux are properly coordinated. When welding low carbon steel, the porosity caused by hydrogen can be reduced by increasing oxidation property. When welding high carbon steel, increasing the deoxidization property can reduce the porosity produced by CO.

(2) Proper addition of alloy agent and slag agent in flux can reduce porosity. For example, proper addition of SiO2, MnO and MgO can reduce porosity. (3) Adjust the flux viscosity.