Effect Mechanism Of Focusing Gas Flow On The Gas Focusing Plasma Arc Welding Process

Plasma arc welding technology has the characteristics of high energy density and low welding cost,so it has been widely concerned in the industrial field.But there are still some disadvantages,such as being extremely sensitive to the change of welding process parameters,insufficient stability of penetration capability in welding medium and thick plates and so on.These shortcomings limit the application of plasma arc welding.Improving arc penetration ability is an important aspect of improving conventional plasma arc welding process.A new technology of gas focusing plasma arc welding was introduced.The arc energy density and arc penetration ability were improved by"secondary compression"of plasma arc with focusing gas.At present,there is little research on the process of gas focusing plasma arc welding,and there is no systematic study on the effect of focusing gas flow on arc behavior and weld formation in gas focusing plasma arc welding.The study of the mechanism of the influence of focusing gas flow on the process of gas focusing plasma arc welding has important theoretical significance and engineering application value for guiding and optimizing the new process of gas focusing plasma arc welding.Design and construct a gas focusing plasma arc welding platform.The welding platform mainly includes plasma arc welding machine and torch system,welding process analysis system,visual inspection system and computer control system.The experimental platform can monitor the welding process electrical signal?such as welding current,arc voltage,etc.?in real-time,take the visual signal such as arc shape,collect the infrared signal such as weld forming temperature-sensitive scanning diagram,realize the automatic control of welding process.It lays a good foundation for researching the plasma arc welding technology of gas recompression.The influence mechanism of focusing gas flow on arc behavior in gas focusing plasma arc welding was studied.The arc morphology and arc voltage of conventional plasma arc and gas focusing plasma arc were compared and analyzed.The results show that under the same welding current,compared with conventional plasma arc,the restraint of plasma arc column is higher,the stiffness of arc is larger,and the arc voltage increases accordingly,so the arc penetration ability is further enhanced.In addition,with the increase of focusing gas flow,the restraint of arc,the arc stiffness and the arc voltage will increase in a certain range,but when the focusing gas flow is too large,it is easy to cause arc warping and arc stability is poor,which is not conducive to weld formation.The mechanism of the effect of focusing gas flow on the weld formation in gas focusing plasma arc welding was studied.it is found that the scanning image of weld temperature sensitivity can directly reflect the quality of weld formation.In this paper,the temperature-sensitive scanning diagram and weld forming characteristics of gas focusing plasma arc welding and conventional plasma arc welding were compared and studied.The results show that when the welding current is 150 A,The penetration ability of gas focusing plasma arc welding is stronger,and it can fully penetrate 304 stainless steel base metal with 8 mm thickness,and the front and back seams are well formed.Under this parameter,the penetration depth of conventional plasma arc welding is only 6.53 mm,and there is gas hole in the root of the weld,so the front of the weld is poorly formed.In addition,when the current is constant and the focusing gas flow rate varies between 0.5-1.5 L·min^-1,the single-side welding and double-side forming are realized,and the forming effect of the front and back seams is good.When the focusing gas flow rate is greater than 2.0 L min^-1,the weld formation begins to deteriorate.That is to say,note that the focusing gas flow is not as large as possible.