Rasearch On Weld's Structure And Property Of High Nitrogen Stainless Steel Sheet

Porosity,nitrogen loss and other problems often occur in the traditional fusion welding of high nitrogen stainless steel.To overcome the difficulties,the paper made experiments on 1.45mm-thick nitrogen steel by TIG,TIG with filler metal and electron beam welding and explored the influence of welding parameters on the quality of weld appearance.Also,the paper analyzed the microstructure and mechanical property of weld.The paper researched the regular pattern of welding process parameters on the forming and quality of the weld.The weld width of TIG weld without filler metal is larger than the weld width of electron beam weld,and there is no porosity in the weld bead of electron beam weld,contrary to the TIG weld without filler metal.The scale of TIG with filler metal welding bead is in the middle of the other two and have excessive penetration of weld bead.welding current is one of the most important factor.The rational current range is 85-100A.Welding speed mainly influences the penetration and weld width while wire feed rate mainly affects excessive penetration of weld bead.The weld beam has little cracks,porosities and other defects by x-ray flaw detection.The paper analyzed the microstructure of weld by SEM,EDS,XRD and other tests.The microstructure of TIG without filler metal and electron beam welding is single dendrite phase austenite.The microstructure of TIG with filler metal is influenced by nitrogen content and solidification mode of weld metal,the microstructure is austenite and ferrite when the nitrogen content reaches 0.5%with AF solidification.The microstructure is austenite when nitrogen content of weld reaches 0.72%;Weld bead only have coarsening austenite when nitrogen content of weld reaches 0.79%with A solidification.There are no nitrides in all three kinds of weld.Different weld bead has different mechanical properties.The tensile strength of TIG without filler metal is 900MPa,the minimum of the three kinds of weld.The tensile strength of TIG with filler metal can reach 995MPa,up to 98%of base metal when the nitrogen content of weld has 0.79%.and the hardness of weld bead can reach 320HV.The tensile strength of electron beam weld reaches 985 MPa while the hardness is 300HV.The mechanical properties of TIG with filler metal and electron beam weld is closely equal to base material.The article also explored the safeguarding products made of high nitrogen steel and has many application fields.The product has great ability of defending bullets,long service life and other merits.