提高444不锈钢焊接接头耐蚀性能的接头设计及工艺研究

发布时间：2018-06-16 18:14

本文选题：钨极氩弧焊 + 444铁素体不锈钢　；参考：《山东建筑大学》2017年硕士论文

【摘要】：由于我国镍金属资源较匮乏以及国际上镍金属的价格波动较大,导致含镍不锈钢成本较高。随着冶炼技术的发展,低镍甚至不含有镍的铁素体不锈钢得到迅速发展,由于其价格较低,具有良好的耐腐蚀能力,尤其是耐氯离子腐蚀能力强,热膨胀系数低,传热性能好等特点,已成功用于换热设备、家用电器、船舶、汽车等行业。但是铁素体不锈钢经过焊接加工后容易出现较多问题,例如接头组织粗大,耐蚀性降低等问题。本文以444铁素体不锈钢为母材,对不同焊接工艺形成的焊接接头性能进行研究,研究结果对推广铁素体不锈钢的应用具有重要现实意义。选用1.5mm厚的444铁素体不锈钢薄板,分别按不采用填充材料、填充材料为母材金属以及填充材料为ER316L奥氏体焊丝进行手工TIG焊对接实验,制取接头试样进行组织观察实验、XRD实验、显微硬度测试实验、拉伸实验、断口扫描实验(SEM)、电化学实验、浸泡实验。通过以上实验结果对比分析不同填充材料对焊接接头性能的影响。通过焊接接头的金相实验得出,焊接接头包括热影响区、熔合区、焊缝区三部分。不采用填充材料、填充材料为母材金属的焊缝区没有发生组织变化,为单一的铁素体组织,并且铁素体呈现柱状晶分布;填充材料为ER316L焊丝的焊缝区组织为奥氏体和针状铁素体组织。显微硬度测试实验结果表明采用ER316L不锈钢焊丝作为填充材料得到的焊接接头焊缝区硬度最高,为220HV,不采用填充材料的焊缝区硬度为172.5HV,填充材料为母材金属的焊缝区硬度为179HV。通过拉伸实验以及断口扫描实验表明三组焊接接头断裂均为韧性断裂,抗拉强度分别为430.54MPa、447.82MPa、476.87MPa,焊接接头伸长率分别为17.12%、22.38%、26.93%,三组接头断裂位置分别为焊缝区、热影响区、母材区。电化学测试结果表明在3.5%的氯化钠溶液中,采用ER316L焊丝为填充材料的焊接接头耐腐蚀能力最优异,其次为采用母材金属为填充材料的焊接接头,最后为不采用填充材料的焊接接头。在6%FeCl3溶液中的浸泡实验中,三组焊接接头浸泡8h,腐蚀速率分别为3.152 g·m-2·h-1、1.243g·m-2·h-1、0.125g·m-2·h-1,通过对腐蚀试样进行观察,三组浸泡试样点蚀坑大小依次为:不采用填充材料的焊接试样、采用母材材料为填充材料的焊接试样、采用ER316L为填充材料的焊接试样。本文在444不锈钢角接实验中,选用ER316L不锈钢焊丝为填充材料进行角接角度分别为10°、16°、20°、28°、40°、50°的六组手工TIG焊接实验。通过焊接接头宏观结构观察,角接角度为10°、16°、20°的接头成型性好,角接角度为28°、40°、50°的接头成型性差,接头出现未焊透以及焊接氧化皮严重等缺陷。角接接头微观组织由奥氏体和针状铁素体组成。在3.5%的氯化钠溶液中进行电化学实验表明接头耐腐蚀能力由强到弱的接头角度依次为:20°、16°、10°、28°、40°、50°。针对焊缝内表面出现氧化皮严重等问题进行焊接工艺改进,焊接过程中利用保护气体进行双面保护,结果表明角接接头耐蚀性得到提高。
[Abstract]:Because of the lack of nickel metal resources in China and the high price fluctuation of nickel metal in the world, the cost of nickel containing stainless steel is higher. With the development of smelting technology, the low nickel or no nickel ferrite stainless steel has been developed rapidly. Because of its low price, it has good corrosion resistance, especially the corrosion resistance of chloride ion. The thermal expansion coefficient is low, the heat transfer performance is good and so on. It has been successfully used in heat exchange equipment, household appliances, ships, automobile and other industries. But after welding, the ferritic stainless steel is easy to have many problems, such as the large joint structure and the corrosion resistance. This paper takes 444 ferritic stainless steel as the parent material and forms the different welding process. The performance of the welded joint is studied. The results are of great practical significance for the application of the application of the ferritic stainless steel. The 1.5mm thick 444 ferritic stainless steel sheet is selected, and the joint test is made by manual TIG welding for the ER316L austenitic welding wire without filling material, filling material and filler material for the austenitic welding wire. Organize observation experiment, XRD experiment, microhardness test, tensile test, fracture scanning experiment (SEM), electrochemistry experiment and soaking experiment. Through the above experimental results, the effects of different filler materials on the performance of welded joint are compared and analyzed. Through metallographic experiment of welding joint, the welding joints include heat affected zone, fusion zone and weld seam. The three part of the area. There is no tissue change in the weld zone without filling material and the filler material is metal metal. It is a single ferrite, and the ferrite presents columnar crystal distribution. The filler material is the weld zone of ER316L welding wire as austenite and acicular ferrite. The microhardness test results show that ER316L is not used. The hardness of weld zone in welded joint of rust steel wire as filling material is the highest, it is 220HV, the hardness of weld zone without filling material is 172.5HV. The hardness of weld zone of the filler metal is 179HV.. The tensile test and fracture scanning experiment show that the fracture of three groups of welded joints are ductile fracture and tensile strength is 4, respectively. 30.54MPa, 447.82MPa, 476.87MPa, the elongation at weld joint is 17.12%, 22.38%, 26.93%, respectively. The fracture location of the three joint is the weld zone, the heat affected zone and the base material area respectively. The electrochemical test results show that in 3.5% Sodium Chloride Solution, the welding joint with ER316L welding wire is the best corrosion resistance, followed by the parent metal gold. In the 6%FeCl3 solution, three groups of welded joints were soaked in 8h, and the corrosion rate was 3.152 G. M-2. H-1,1.243g. M-2. H-1,0.125g. M-2. H-1 respectively. By observing the corrosion specimens, the size of the pitting pit of the three groups of soaked samples was in turn: no The welded specimens with filler materials are used to weld samples with material material as filler materials and ER316L is used as filler. In the 444 stainless steel corner connection experiment, the ER316L stainless steel wire was selected as the filling material to carry out the manual TIG welding experiments of six groups of manual TIG welding with angle angle of 10 degrees, 16 degrees, 28 degrees, 40 degrees, 50 degrees respectively. The welding joint macroscopic structure observation, the angle joint angle is 10 degrees, 16 degrees, 20 degree joint forming good, the angle connection angle is 28 degrees, 40 degrees, 50 degree joint formability is poor, the joint appears not soldering and the welding oxide skin serious and so on. The angle joint microstructure is composed of austenite and acicular ferrite. In 3.5% Sodium Chloride Solution, the electrochemical solid is carried out. The results show that the joint angle of the joint corrosion resistance from strong to weak is 20, 16, 10, 28, 40, 50. The welding process is improved for the serious oxidation skin of the inner surface of the weld, and the protective gas is protected by two sides in the welding process. The results show that the corrosion resistance of the joint is improved.
【学位授予单位】：山东建筑大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG407

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