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低镍含氮奥氏体不锈钢激光-电弧焊电弧特性及组织性能

Effect of welding heatinput on microstructure and properties of MAG welded joint for low nickel high nitrogen austenitic stainless steel

  • 摘要: 采用100%Ar2,98%Ar + 2%N2,92%Ar + 8%N2,85%Ar + 15%N2四种混合比例的保护气体对08Cr19MnNi3Cu2N低镍含氮奥氏体不锈钢进行激光-脉冲MAG电弧复合焊接,研究保护气体中氮气比例对焊缝中气孔数量、焊缝熔深和熔宽、电弧形态、微观组织及铁素体含量等影响机制. 结果表明,随着保护气体中氮气比例的增加,焊缝气孔数量增多,气孔的体积也随之增大;焊缝熔深显著增加,而焊缝熔宽变窄,焊缝平均硬度有所下降,电弧收缩明显,电弧弧柱宽度随着氮气比例的增加而减小,焊接飞溅数量随之增加且体积增大,电弧稳定性变差;焊缝中铁素体含量由6.91%,6.80%减少至5.38%和4.62%,铁素体枝晶也逐渐变细,二次枝晶臂变短. 焊缝组织中只仅存在少量δ和γ两相;从4个晶面观察奥氏体晶粒的尺寸也随着氮气比例的增加而逐渐减小.

     

    Abstract: The laser-pulsed hybrid welding of 08Cr19MnNi3Cu2N austenitic stainless steel with low nickel and nitrogen content was carried out by using four kinds of shielding gases: 100% Ar, 98% Ar + 2% N2, 92% Ar + 8% N2 and 85% Ar + 15% N2. The effects of nitrogen proportion in the shielding gas on the weld penetration width, microhardness, microstructure, arc characteristics and ferrite content were studied. The results shows that with the increase of nitrogen ratio, the number and volume of porosity increase, and which also can induced that the weld penetration become deeper remarkably and the weld width become narrower. The average microhardness of weld decreases and the arc column width decreases with the increase of nitrogen ratio. The weld spatter increases in number an volume, and the amount of welding fume increases gradually. The arc stability becomes poor with the increase of nitrogen content in the shielding gas. In addition, the ferrite content in the weld metal decreased from 6.91%, 6.80% to 5.38% and 4.62%, the ferrite dendrites also gradually became smaller, and the secondary dendrite arm became shorter. Only a small amount of δ and γ phases were found in the weld metal, and no σ phase and nitride were found to precipitate. The austenite grain size also decreased with the increase of nitrogen ratio from the four crystal planes.

     

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