The Analysis Of Laser Welding Process Based On Plasma Electrical Signal

With the development of laser welding technology, the detection is becoming more and more important. The usual method includes acoustic signal?optical signal?high speed photography and electrical signal. The paper provides a new detection method—Passive electric probe. The theoretical basis?detection system and analytic system will be introduced in this paper.The laser surface melting experiment was done with the 304 stainless steel. Laser plasma electrical signal was collected during the welding process, and then statistic and frequency analysis were done with the signal.The laser weld mode of 304 stainless steel can be distinguished by probability density analysis: when in deep penetration welding, there is a peak in a negative voltage amplitude; when in thermal conductivity welding, there is a peak both in negative and zero voltage amplitude. However, there isn't this kind of phenomenon for 430 stainless steel and Q235 carbon steel.The laser weld mode of 304 stainless steel can also be distinguished by standard deviation analysis: when in deep penetration welding, the standard deviation is less than a certain value; when in thermal conductivity welding, the standard deviation is more than a certain value. However, there isn't this kind of phenomenon for 430 stainless steel and Q235 carbon steel.Besides, frequency analysis was also done with the signal: when in deep penetration welding, there is a peak in certain frequency, and the range is about 1200~1400Hz; when in thermal conductivity welding, there isn't. However, there isn't this kind of phenomenon for Q235 carbon steel.