The High Frequency Welding Machine process of galvanized steel

Posted by davisonmachinery on December 12th, 2016

The High Frequency Welding Machine process of galvanized steel always makes us headache. For example, one of companies's air outlet of the coolers is made by welding 2mm-thickness galvanized steel sheets.

Because the Galvanized steel sheet was welded by SMAW (shielded metal arc welding), the Sheet is not only burning through but also bad fusion. It is very easy to generate a lot of sand porosity. Therefore, this article will introduce how to improve the welding process of galvanized steel.

Original process flow:

First step is to butt welding and fixing the welding line. Second step is to weld by shielded metal arc welding. The DIA of electrode is 2.5mm with the grade: J422. The welding electricity is 40-80A. Arc voltage is 14-20V. The weld speed is 18-25cm/min.

The cause of defect:

There is a layer of Zinc on the surface of galvanized Steel Sheet, so some small explosion would be occurred during the welding process. Once the shape of welding line is bad after explosion, there will be a lot of sand porosities after cleaning the weld line.

If the electrical current is strong, the 2mm-thickness galvanized sheet will be penetrated, which leave the galvanized sheets with different big or small welding overlaps. If the electrical current is soft, the welding place of the sheet would not be burned thoroughly.

The fusion is bad, so the weld line is easily fall off.

After above analysis, the welding defect is mainly caused by the following points:

First of all, SMAW is very difficult to control for the Electrical Current, Arc Voltage and the distance between electrode and sheets.

Secondly, the welding part is galvanized steel sheet which own zinc layer. During the weld process, it is very easy to cause explosive melt, which makes a lot of sand porosities.

Finally, Zinc is very easily oxidized during the HF Welding  process, which will generate harmful gas for human being. The gas will affect the health of workers. Besides it pollutes the environment.