采用Φ2.0mm焊丝超窄间隙焊接1Cr18Ni9Ti奥氏体不锈钢的焊缝成形及耐蚀性研究

发布时间：2018-03-29 07:39

本文选题：焊缝成形　切入点：晶间腐蚀　出处：《兰州交通大学》2015年硕士论文

【摘要】：奥氏体不锈钢因具有优良的力学性能和耐腐蚀性能,以及突出的焊接性能和生物相容性,在核岛工业、航空航天、生物医学等诸多领域中得到了广泛的应用。然而,在工程应用方面,由于受传统焊接方法在控制线能量方面的局限性,使得奥氏体不锈钢焊接接头极易出现因晶界贫铬而导致的晶间腐蚀,从而显著降低接头的耐蚀性能。超窄间隙焊接方法(UNGW)由于侧壁间距不大于6mm,极大地降低了焊接线能量,在改善奥氏体不锈钢焊接性及接头耐晶间腐蚀具有独特的优势。论文采用Φ2.0mm焊丝,利用超细颗粒焊剂熔化后形成的熔渣壳对焊接电弧的约束作用,进行了一系列超窄间隙焊接1Cr18Ni9Ti奥氏体不锈钢的试验,并分别研究了焊接电流和电弧电压对焊缝成形规律、焊缝组织以及接头耐晶间腐蚀性能的影响。试验结果表明,能够获得成形良好焊缝的电弧电压与焊接电流的匹配区间分别为25V~33V和210A~320A,而在这个范围之外的其它参数匹配情况下,焊缝成形情况分别为“侧壁熔合不良”和“电弧攀升”。观察不同线能量双道焊接头的组织表明,当线能量为0.84kJ/mm时,第一道焊缝的组织为均匀等轴晶,第二道焊缝的组织为方向性很强的粗大柱状晶;当线能量为1.13 kJ/mm时,第一道焊缝的组织同样为等轴晶,而第二道焊缝的柱状晶组织发生细化,且夹杂有少量近似等轴晶的晶粒;当线能量为1.28 kJ/mm时,第一道焊缝组织仍为等轴晶组织,但第二道焊缝的组织由柱状晶向等轴晶过渡。扫描电镜下观察接头的浸泡腐蚀微观形貌表明,随着焊接线能量的增大,试样焊缝区的腐蚀由不均匀腐蚀向均匀腐蚀转变;而相比之下,不同试样焊缝区两侧的热影响过热区的腐蚀形貌无太大差异。计算接头腐蚀速率表明,试验所得接头,其耐蚀性优于母材。综上所述,在匹配合理的焊接参数下,采用Φ2.0mm焊丝在超细颗粒焊剂约束电弧超窄间隙焊接1Cr18Ni9Ti奥氏体不锈钢可获得焊缝成形良好、耐晶间腐蚀和点蚀性能优良的超窄间隙焊接接头。
[Abstract]:Austenitic stainless steel has been widely used in many fields such as nuclear island industry, aerospace, biomedicine and so on because of its excellent mechanical and corrosion resistance, outstanding welding properties and biocompatibility. In engineering application, due to the limitation of conventional welding method in control line energy, austenitic stainless steel welded joints are prone to intergranular corrosion caused by chromium deficiency in grain boundary. Therefore, the corrosion resistance of the joints is significantly reduced. The ultra-narrow gap welding method UNGW has greatly reduced the welding line energy because the side wall spacing is not greater than 6 mm. In order to improve the weldability of austenitic stainless steel and the intergranular corrosion resistance of the joints, 桅 2.0mm wire is used in this paper, and the slag shell formed by the melting of superfine particle flux is used to restrain the welding arc. A series of experiments on ultra-narrow gap welding of 1Cr18Ni9Ti austenitic stainless steel were carried out, and the effects of welding current and arc voltage on weld formation, weld microstructure and intergranular corrosion resistance of joints were studied respectively. The matching ranges of arc voltage and welding current for well-formed weld are 25V~33V and 210A320A, respectively. The weld formation conditions are respectively "bad side wall fusion" and "arc climbing". The microstructure of the double pass welding joint with different wire energy is observed. When the line energy is 0.84kJ/mm, the structure of the first weld is uniform equiaxed crystal. The structure of the second weld is a coarse columnar crystal with strong directionality, and when the linear energy is 1. 13 kJ/mm, the structure of the first weld is equiaxed, while the columnar structure of the second weld is refined, with a small amount of grains approximately equiaxed. When the line energy is 1. 28 kJ/mm, the structure of the first weld is still equiaxed, but the structure of the second weld is transferred from columnar to equiaxed. The corrosion of the weld zone of the specimen changed from non-uniform corrosion to uniform corrosion, but the corrosion morphology of the heat-affected superheated zone on both sides of the weld zone of different specimens was not much different. The calculation of the corrosion rate of the joints showed that the joints obtained from the tests showed that, The corrosion resistance of the stainless steel is superior to that of the base metal. To sum up, under the reasonable welding parameters, 桅 2.0mm wire can be used to weld 1Cr18Ni9Ti austenitic stainless steel in ultra-narrow gap of ultra-narrow arc confined by superfine particle flux. Ultra narrow gap welded joints with excellent resistance to intergranular corrosion and pitting.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG457.11

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