Laser-Arc Hybrid Welding Of Stainless Clad Steel Plate

Stainless clad steel plate(SCSP)is a composite structure made by bonding stainless steel(cladding layer)and carbon steel or low alloy steel(base layer),which is the ideal substitution of stainless steel due to the low cost.At present,single-pass welding is hard to meet the requirement of corrosion resistance,and multi-pass welding is with the complicated process and low efficient.Laser-arc hybrid welding would be potential to improve the welding efficiency and the properties of SCSP weld together because it both owns the advantages of the high-energy density of laser welding and the high filling efficiency of arc welding,as well as the laser-arc interaction.However,the relevant study has not been addressed.Therefore,laser-arc hybrid welding of 304 stainless steel/Q235 B carbon steel clad plate was carried out in this study,and the effects of welding parameters on the microstructure,mechanical properties and corrosion resistance of the welds were studied.The main results are listed as follows.Accepted SCSP weld with good surface appearances and the mechanical properties and corrosion resistance equal to or better than the base metal could be obtained by single-pass laser-arc hybrid welding under the optimized welding parameters and appropriate filling wire(ER310),which is laser power of 4 kW,wire filling rate of 4 m/min and welding speed of 2 m/min.With the weld,the microstructure of arc zone(Arc Z)is composed of the dendrites and cellular grains;while that of laser zone is composed of the columnar dendrites and a small amount of fine martensites.The welding parameters almost do not have the effects on the microstructure of cross-ArcZ,but have significant effects that at the top surface of the Arc Z closely related to weld corrosion resistance.For the top surface of the ArcZ,the fraction of cellular grain increases with increasing laser power and wire filling rate,and decreasing welding speed,while the Cr content decreases with increasing laser power,but first increases and then decreases with increasing wire filling rate and welding speed.The change of the Cr content is well corresponding to the dilution rate of cladding layer alloy element.All the welds shows good mechanical properties.Due to the formation of fine martensite,the ultimate tensile strength and the yield strength of the tensile samples are similar with the base metal,about 500 and 300 MPa,respectively,but the elongation decreases from 39% of the base metal to 32% because of the decrease of the ductility.It was found that the weld corrosion resistance decreases with increasing laser power,but first increases and then decreases with increasing wire filling rate and welding speed.Relatively,the laser power shows the greatest impact,but the wire filling rate shows the smallest impact.The charge transfer resistance(Rct)decreases from 2411 to 534 k?·cm2 when the laser power increases from 4 to 6 kW,with the variation of 1877 k?·cm2.However,the Rct variation is only 566 k?·cm2 when the filling rate increases from 2 to 6 m/min.The results showed that the corrosion resistance improvement was attributed to two reasons.Firstly,the increased the Cr content increases the thickness of passive film,and provides a better protection against the corrosion.Secondly,the homogenized microstructure increases the damage difficulty of passive film,and decreases the pit propagating speed.