低镍含氮奥氏体不锈钢脉冲TIG焊接接头组织性能研究

Study on Microstructure and Properties of Pulsed TIG Welded Joints of Austenitic Stainless Steel with Nitrogen and Low Nickel

QN1803作为一种低镍含氮奥氏体不锈钢,相对于传统304奥氏体不锈钢减少了60%Ni含量,具有更优异的力学性能与耐腐蚀性能,同时节约了成本,目前广泛应用于建筑装饰、医疗器械、家电制品等领域。以低镍含氮奥氏体不锈钢QN1803为研究对象,采用脉冲TIG焊,借助SEM、OM、HV等测试手段研究焊接热输入对焊接接头的微观组织、力学性能、腐蚀性能的影响。结果表明,QN1803室温组织由铁素体和奥氏体组成,HAZ区晶粒与母材相比未见明显长大,接头熔合良好;焊接接头抗拉强度为650~700 MPa,焊缝组织硬度为240~260 HV。随着热输入的增加,焊缝点蚀电位由340 mV下降至290 mV,晶间腐蚀速率由455.3 g/(m^(2)·h)提升至570.6 g/(m^(2)·h),表明焊接接头耐腐蚀性能随着热输入的增加而下降;应用有限元软件MSC.Marc对不同焊接热输入条件下的焊接温度场及残余应力场进行模拟。结果表明,焊后残余应力集中分布于PMZ区及HAZ区;且残余应力峰值随焊接热输入增加呈上升趋势。

As a kind of low nickel nitrogen austenitic stainless steel,QN1803 reduces the Ni content by 60%compared with the traditional 304 austenitic stainless steel,and has better mechanical properties and corrosion resistance while saving cost.At present,it is widely used in architectural decoration,medical devices,household appliances and other fields.In this paper,the low nickel nitrogen austenitic stainless steel QN1803 was welded by pulsed TIG welding.The effects of welding heat input on the microstructure,mechanical properties and corrosion properties of welded joints were studied by means of SEM,OM,HV and so on.The results show that the microstructure of QN1803 at room temperature is composed of ferrite and austenite,the grain in HAZ zone does not grow obviously compared with the base metal,and the joint fuses well,the tensile strength of the welded joint is between 650~700 MPa and the hardness of the weld is between 240~260 HV.With the increase of heat input,the pitting potential of weld decreased from 340 mV to 290 mV,the intergranular corrosion rate increased from 455.3 g/(m^(2)·h)to 570.6 g/(m^(2)·h),and the corrosion resistance of welded joint decreased with the increase of heat input.The finite element software MSC.Marc is used to simulate the welding temperature field and residual stress field under different welding heat input conditions.The results show that the residual stress after welding is concentrated in PMZ zone and HAZ zone,and the peak value of residual stress increases with the increase of welding heat input.