Experimental study of magnetic arc blow for plasma arc cutting

Abstract

Oxygen plasma arc cutting (PAC) is widely used in various industrial fields. In the case of cutting magnetized plates, the magnetic field is concentrated around the cutting front according to the progress of the cutting, and the electromagnetic force induced by leakage magnetic field deflects the plasma jet. The deflected plasma jet causes poor cutting quality and sometimes causes fatal damage on the electrode and the nozzle by a double arc as abnormal discharge. This phenomenon is called magnetic arc blow, and it is a critical issue of applying plasma cutting on magnetized plates. The purpose of this study is to investigate the arc blow behaviour and to devise a method to prevent it. We examined the relationship between operating conditions and double arc with external magnetic fields on the plasma jet. We found criteria of operation conditions that induce the arc blow. In addition, we have succeeded in suppressing the double arc generation attributed to the external magnetic field with a mild steel shield cap attachment around the nozzle tip.

Keywords::

• plasma arc cutting
• magnetic arc blow
• double arc
• magnetic shield

Acknowledgements

This study was a joint project carried out by Komatsu and Kanazawa University. The authors would like to express their appreciation of the discussions and advice kindly supplied by members of the Environmental Power Engineering Group of Kanazawa University during the study and the valuable help in part design and fabrication for experiments supplied by members of Komatsu's Twister Group, Development Department, Sakagane Operating Division.

Notes

Presented at the Autumn National Conference 2012.