Cr17型超低碳铁素体不锈钢薄板焊接工艺及接头性能的研究

【作者】 赵利勇；

【导师】 胡明辅；

【作者基本信息】 昆明理工大学 ， 化工过程机械， 2008， 硕士

【摘要】 铁素体不锈钢是一种不含镍或含少量镍的经济型不锈钢,且具有优良的抗应力腐蚀性能,其应用前景十分广阔。深入、系统地研究该类钢的焊接问题,对掌握其基本焊接性、优化焊接工艺、合理匹配焊接材料、获得性能良好的焊接构件具有重要意义和应用价值,同时对推广铁素体不锈钢的应用及促进不锈钢产业的发展具有重要的现实意义。本论文选用超低碳铁素体不锈钢00Cr17Ti（Nb）为试验材料,系统分析了该钢焊接接头的力学性能、接头各区域的显微组织、接头内的夹杂物、接头表面氧化皮的组织结构,研究了焊接工艺参数对该钢焊缝组织和性能的影响,同时对其焊接接头的防腐蚀处理工艺和氧化皮的酸洗钝化机理进行了分析研究,利用均匀设计试验方法和回归分析方法对其焊接接头的酸洗钝化液配方进行了优化。试验表明:在焊接铁素体不锈钢薄板时,应在焊接线能量适当小的基础上,适当增大焊接电流和焊接速度;采用手工氩弧焊时焊接电流在100～110A、焊接电压在16～17V、焊接速度在25～30 cm/min的范围内,采用熔化极气体保护焊时焊接电流在110～120A、焊接电压在17～18V、焊接速度在45～55cm/min的范围内,可以获得力学性能和耐腐蚀性较好的焊接接头;在焊接过程中要防止焊接材料表面和熔池受到污染,采用焊枪后加保护气体罩的方法,可将焊缝高温区全部保护在氩气的笼罩范围内;采用与母材同质焊丝焊接时,焊缝和热影响区组织主要为单相铁素体组织;在焊接接头的焊接热影响区内,从熔合线偏母材的方向上,晶粒尺寸随距熔合线的距离增大而减小;随着焊接线能量的增大,焊缝柱状晶粗化程度增大;焊缝及HAZ区内的点状析出物为Cr、Ti等元素的碳化物,它们对接头的脆化有很大贡献,其存在区域和数量随焊接线能量的增大而增多。对铁素体不锈钢焊接接头氧化皮的组织结构和酸洗钝化机理进行的分析表明:氧化皮的成份主要为FeO、Fe₃D₄、Fe₂O₃、FeO·Cr₂O₃、FeO-Cr₂O₃·Fe₂O₃等致密型氧化物;酸洗过程中氧化皮的内层是靠溶解进行的,而大部分的外层是靠剥离来进行的。通过对酸洗钝化试验数据的分析,建立了配方各组分与腐蚀率的数学关系式,并对酸洗钝化液配方进行了优化。检验表明:利用自配的酸洗钝化剂对铁素体不锈钢表面氧化皮的实际酸洗钝化效果与模拟效果的误差为7%,且工件表面钝化膜保护效果良好,表面无锈蚀痕迹,达到酸洗钝化检验要求。更多还原

【Abstract】 Ferrite stainless steel is an economical stainless steel which doesn’t contain nickel or a little nickel.It has excellent ability of stress corrosion resistance,so it has the broad prospects of application.Studying such steel’s welding problem deeply and systematically is very important and valuable in the application for mastering the basic seal performance. To improve the welding technology and match the welding materials reasonably of this kind of steel,this paper obtains a good performance welding structural part.At the same time,these have important realistic significance for enlarging the application of the ferrite stainless steel and boosting the development of the steel.By using the Ultra-low Carbon Ferrite Stainless Steel 00Cr17Ti（Nb）as test materials, the paper analyses the mechanics performance of the welded joint,the microstructure of the joint,the materials of the welded joint and the microstructure of the oxide skin. Furthermore,the influence of the welding technology to the tissue and performance of the welded joint have been studied.At the same time,this paper researches the anti-corrosion techniques and the acidic washing passivation of the welded joint.At last,this paper makes an improvement for the acidic washing passivation liquid’s formula with the methods of Uniform Experimental Design and the Regression Analysis.The tests indicate that:when welding the ferrite stainless steel,we should increase the welding current and speed on the basis of the welding line’s energy’s low enough.When the welding current is between 100-110A,welding voltage is 16-17V,welding speed is 25-30cm/min,with the way of TIG,the welding current is between 110-120A,welding voltage 17-18V,welding speed between 55-60cm/min,with the MAG,we can get a good welding joint with good Mechanical Properties and Anti-corrosion Property.In the progress of welding,we should avoid the pollution of the welding materials and melting pool.With the way of welding torch and protecting gas cover,we can make the high temperature region be in the region of the protection of the argon gas.When we use the same material for welding,the welded joint and the HAZ are mainly single-ferrite stainless steel.In the HAZ of the welded joint,from the direction of the melting line,the crystal’s size will decrease with the increment of the distance between the melting lines.With the increase of the melting line’s energy,the armoring degree of the weld seam columnar grain will increase.The welding seam and the HAZ precipitate is Cr or Ti,they are the main reasons of the weld joint brittleness,the existing region and the number will increase with the increase of the welding line’s energy.The analysis results to the organization structure of the ferrite stainless steel and the mechanism of the acidic washing passivation technology of the welded joint show that:the main ingredients of the oxide skin are compact type oxides such as FeO、Fe₃O₄、Fe₂O₃、FeO·Cr₂O₃、FeO·Cr₂O₃·Fe₂O₃,etc.The inner layer of the oxide skin is in the dissolving,while the outer surface is in the peeling off.Through the analysis to the acidic washing passivation technology of the welded joint,this paper establishes a mathematical resolution of matching the ingredients and the rate of corrosion,and makes an improvement of the acidic washing passivation liquid.The results shows:the error between the real performance and the simulation results is 7%,the passive film in the surface of workpiece have perfect shielded effect and doesn’t haverusty spots,and the effect is very good when pickling and passivating with the formula.更多还原