Properties Rearch On The Corrosion Resistance Of 316L Stainless Steel Welded Joint By Laser

Laser Semi-Welded Plate Heat Exchangers are widely used in the heat exchange industry,especially in the field of nuclear power,due to its advantages of disassembly,corrosion resistance and other unique.But it is lack of systematic research on the corrosion resistance of the welded joint of the laser welded plate.For that reason,the thesis has been deeply studied on the corrosion resistance of 316 L stainless steel welding by high power YAG laser and inert gas.As a contrast,the thesis also has been deeply studied on the corrosion behavior of 316 L stainless steel welding by YAG laser shielding gas,CO₂ laser shielding gas and Laser shock weld.Providing technical support for safe and sustainable operation in the field of nuclear power Laser Semi-Welded Plate Heat Exchanger.This paper takes 316 L stainless steel which is commonly used in nuclear heat exchanger as the research object,and bases on general industrial high-power YAG and CO₂ laser as the research means.Microstructure of welding seam,grain size,residual stress and the corrosion resistance of welding joint were analyzed by the Metallographic microscope,Scanning electron microscopy?sem?,X-ray residual stress meter,Electrochemical workstation and other equipments.The conclusions are summed up through the data: On the one hand,first of all,the corrosion resistance of the welded joints is more than 90 percent of parent metal's,which are affected by unit line energy and local nonuniform heat input when we adopt the method of YAG laser gas protection welding of which processing parameters are P=1.5kW-2.0kW,v=0.015m/s-0.035m/s and P=3.0kW-3.5kW,v=0.05m/s-0.08m/s,where P and v are the laser power and laser scanning speed.Then,the corrosion resistance of the welded joints is down 23 percent at least under the conditions of the YAG laser gas free welding than to the gas protection welding resulting from the uniformity of the micro-structure decreased and the size of grains and the residual stress increased which are affected by the welding appearance oxidized severely.Lastly,the corrosion resistance of the welded joints is down 16 percent at least resulting from the nonuniform of the micro-structure and residual stress increased affected by the influence of the beam mode and laser wavelength.On the other hand,there is a significant increase in residual compressive stress of which the depth is 100?m to 120-300 MPa and the grains are refined markedly after the technology of the LSP?laser shot peening?,which results in enhancing 2-3 times in the aspect of the corrosion resistance.