Control Of Heat Input In Continuous Welding Of Mesh Wire By Microplasmaarc Welding

Ultra-fine wire mesh,because of its special retiform permeability,large tensile,high temperature and corrosion resistance,has been widely used for separation and filtration of water,gas,oil and other medium in aviation,petrochemical,mechatronic and textile printing.However,it is extremely sensitive to the change of heat input during welding because of its special layering and alternating distribution geometry structure.Burn-through or incomplete fusion will occur when the heat input is too large or too small and affect the quality of welding joints seriously.Therefore,accurate control of the heat input in continuous welding of wire mesh is the key to ensure the quality of welding joints.In order to accurately control the heat input in continuous welding of wire mesh,based on the special structure of wire mesh,special heat dissipation effect and special requirements for heat input in welding process,firstly,,the relationship between heat input characteristics of continuous welding of wire mesh by microplasma arc welding(MPAW)and welds forming in “pulse” mode was studied.Based on three different matching relationships between wire mesh structure parameters,pulse current parameters and welding process parameters,three different matching relations of “one pulse current on one wire”,“one pulse current on multi-wires” and “multi-pulse currents on one wire” were proposed.The forming mechanism of welds under three different welding heat input modes was further studied.Secondly,three different welding heat input modes in continuous welding of wire mesh by MPAW in pulse current welding experiment with 16×16 mesh number and0.35 mm wire diameter was used to study the effect of pulse current parameters on the relationship between “wire number” and “pulse number” in continuous welding of wire mesh by MPAW.The effects of the changes of pulse current parameters on the welding spots forming characteristics and welding heat input on the welding process were in-depth studied.On the basis of studying the effects of the changes of pulse current parameters on thewelds forming and welding heat input,microstructure and mechanical properties of weldspots by super depth of field microscope,tensile strength and hardness testing in different pulse current parameters were also studied.From this perspective,welds performance under different pulse current parameterswas analyzed in wire mesh continuous welding process.The effect of controlling different welding heat input on the microstructure and mechanical properties of welding spots during continuous welding of wire mesh was pointed out subsequently.At last,ANSYS finite element analysis was used to establish wire mesh geometric modeland dynamic welding process under three different welding heat input models was further studied.Control mechanism of heat input in continuous welding of wire mesh by MPAW with pulse current was studied and the numerical simulation results were compared with welding process experiment data subsequently.Some Results were obtained in the study.“One pulse current on one wire” was formed when the ratio of welding speed to the distance between two adjacent longitude wires was exactly equal to the pulse current frequency.Zoom in base current and peak current and avoid high duty cycle was an effective way to achieve stable control of heat input,small welds grain size and good joint mechanical properties in continuous welding of wire mesh by MPAW.“One pulse current on multi-wires” was formed when the ratio of welding speed to the distance between two adjacent longitude wires was greater than the pulse current frequency.Zoom in base current and peak current and avoid high duty cycle was the basic condition to achieve stable control of heat input,small welds grain size and good joint mechanical properties in continuous welding of wire mesh by MPAW.“Multi-pulse currents on one wire” was formed when the ratio of welding speed to the distance between two adjacent longitude wires was less than the pulse current frequency.Avoid excessively high base current and peak current,adopt high pulse frequency was the best way to achieve stable control of heat input,small welds grain size and good joint mechanical properties in continuous welding of wire mesh by MPAW.