高氮奥氏体不锈钢薄板焊接成形及组织性能控制研究

发布时间：2018-03-08 06:07

本文选题：高氮钢　切入点：薄板　出处：《南京理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：高氮奥氏体不锈钢焊缝容易出现气孔、氮化物析出、裂纹等问题,针对这一技术难点,本文采用自制高氮钢焊丝,对1.45mm的高氮钢薄板进行无填丝TIG焊、填丝TIG焊以及电子束焊的零间隙对接工艺试验研究,探究了个工艺参数对焊缝成型质量的影响,并对其微观组织与力学性能进行研究。分析了高氮钢薄板焊缝成型及质量的规律。无填丝TIG焊焊缝较宽,焊缝气孔缺陷较多,电子束焊缝则较窄,无气孔缺陷,两者皆无余高。填丝TIG焊焊缝尺寸在两者之间并又存在余高,焊接电流会影响焊缝的各个尺寸参数,合理的电流范围在85～100A之间;焊接速度影响焊缝的熔深熔宽;送丝速度则影响焊缝的余高,焊缝中气孔、裂纹明显减少。通过SEM、EDS、XRD、元素含量检测等方法,分析了高氮钢焊缝微观组织,发现高氮钢无填丝TIG焊焊缝组织是单相奥氏体。填丝TIG焊焊缝组织与氮含量有关,当焊缝氮含量为0.5%时,组织为奥氏体+骨架状铁素体,此时为AF凝固模式;当焊缝氮含量逐渐升高,为0.72%时组织为奥氏体,奥氏体枝晶方向性明显;当焊缝氮含量为0.79%时,组织为单相奥氏体且晶粒粗化,为A凝固模式。而高氮钢电子束焊缝组织是单相奥氏体。上述三种焊缝中均未出现氮化物的析出。探究了高氮钢接头的力学性能。无填丝TIG焊抗拉强度为900MPa;填丝TIG焊接头抗拉强最高达到995MPa,可达到母材的98%,与母材近等强,焊缝区硬度最高值为320HV;电子束接头抗拉强度可达到985MPa,同样与母材近等强,焊缝区硬度最高值为 300HV。初步探索了高氮钢的防护应用,有较多的应用领域,具有抗弹性能较好,使用寿命长以及其他优点。
[Abstract]:The weld seam of high nitrogen austenitic stainless steel is easy to appear porosity, nitride precipitation, crack and so on. In view of this technical difficulty, this paper adopts self-made high nitrogen steel welding wire, carries on the TIG welding of 1.45mm high nitrogen steel sheet without filler wire. The experimental study on the zero-gap butt joint process of wire filling TIG welding and electron beam welding is carried out, and the influence of a process parameter on the weld forming quality is explored. The microstructure and mechanical properties of the weld were studied. The rules of weld forming and quality of high nitrogen steel sheet were analyzed. The weld seam of TIG welding without filler wire was wider, the weld hole defects were more, and the electron beam weld seam was narrower and no porosity defect. The weld size of filler wire TIG welding is between them and there is surplus height, the welding current will affect the weld parameters, the reasonable current range is between 85 and 100A, the welding speed will affect the weld penetration width. The feeding speed of wire affects the residual height of the weld, and the porosity and crack in the weld are obviously reduced. The microstructure of weld seam of high nitrogen steel is analyzed by means of SEMMA-EDSX XRD, element content detection and so on. It is found that the microstructure of TIG welding weld of high nitrogen steel is single phase austenite. The microstructure of TIG welding weld is related to nitrogen content. When the nitrogen content of weld is 0.5, the microstructure is austenitic skeleton ferrite, which is AF solidification mode. When the nitrogen content of the weld increases gradually, the microstructure is austenite and the austenite dendrite directivity is obvious when the nitrogen content of the weld is 0.72, and when the nitrogen content of the weld is 0.79, the microstructure is single-phase austenite and the grain is coarser. The microstructure of electron beam weld of high nitrogen steel is single phase austenite. There is no precipitation of nitride in the above three welds. The mechanical properties of high nitrogen steel joint are investigated. The tensile strength of TIG welding without filler wire is 900MPa; the tensile strength of filler wire welding is 900MPa; The tensile strength of TIG welding joint is up to 995MPa, which can reach 98% of the base metal, and is nearly as strong as the base metal. The maximum hardness of weld zone is 320HV.The tensile strength of electron beam joint can reach 985 MPA, which is nearly equal to that of base metal, and the highest value of weld zone hardness is 300 HV. The protective application of high nitrogen steel has been preliminarily explored. Long service life and other advantages.
【学位授予单位】：南京理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG457.11

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