氮气对SAF2507双相不锈钢GTAW焊接接头组织与性能影响

采用GTAW焊接SAF2507双相不锈钢,焊丝为ER2594,保护气体为Ar+N2。研究了保护气体中氮气(φ(N2)=0~5%)比例对SAF2507 GTAW焊接接头组织和性能的影响。结果表明,随着保护气体中N2含量的增加,焊缝组织中奥氏体相增多,硬度下降,耐点腐蚀性能增强;当N2含量到达5%时,产生焊接飞溅和焊接气孔,接头焊缝冲击功降低;采用φ(Ar)+φ(N2)2%~3%保护的焊接工艺,焊接接头能保持较好的相比例,焊接接头的组织、力学和点腐蚀等综合性能更优。     

氮气比例对混凝土桥梁中钢筋焊接性能的影响

通过改变焊接保护气氛中氮气的含量,研究氮气比例对钢筋焊接接头组织与性能的影响。结果表明,随着N2比例从0%上升至5%,焊缝区的奥氏体含量从45%上升至62%,热影响区的奥氏体含量从44%上升至57%。随着N2含量的增加,焊缝区和热影响区的冲击功都表现为先增加而后降低的趋势,在氮气含量为3%时取得冲击功的最大值。随着N2含量的增加,焊缝区和热影响区的显微硬度都表现为逐渐降低,而在N2比例从1%增加至3%时降低幅度较小。     

保护气体中氮气比例对高氮钢双面同轴TIG焊接工艺性的影响

针对高氮低镍奥氏体不锈钢开展了双面同轴TIG自熔焊试验，分析了保护气体成分对电弧电压、电弧形态、钨极形貌、焊缝气孔与含氮量的影响规律. 结果表明，随着保护气体中氮气比例的提高，平均弧压以三次函数的速度增大，波动程度亦随之呈增大趋势；氮气的加入导致电弧显著收缩，焊后钨极表面覆盖棕褐色氮化钨薄层，同时焊接飞溅增大，电弧出现周期性“尾焰反射”现象，焊接稳定性随氮气比例提高而变差；随保护气体中氮气比例的提高，焊缝气孔数量和最大气孔尺寸同时增加，焊缝含氮量先增大后趋于稳定；为了降低焊接不稳定和焊缝气孔的不利影响，保护气体中氮气的比例应低于20%.     

低镍含氮奥氏体不锈钢激光-电弧焊电弧特性及组织性能

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...     

低镍不锈钢激光-电弧复合焊接头组织性能研究

低镍含氮奥氏体不锈钢强度高,韧性佳,在化工装备及建筑装饰等领域广泛应用。为揭示保护气体对低镍含氮奥氏体不锈钢焊接接头微观组织和力学性能的影响机制,分别采用92%Ar+8%N2与95%Ar+5%CO2两种混合比例的保护气体对08Cr19Mn6Ni3Cu2N低镍含氮奥氏体不锈钢进行了激光-MAG电弧复合焊。研究表明：氮气的加入使焊接接头平均显微硬度有所下降;电弧收缩明显,焊接飞溅增加且体积增大,电弧稳定性变差;焊缝中奥氏体含量增加约20%,而铁素体枝晶变细,二次枝晶臂变短。焊缝组织中未发现σ相及氮化物析出;从四个晶面观察奥氏体晶粒尺寸也是由于氮气的加入而减小;焊接接头拉伸性能略微下降,但耐腐蚀性能提高。     

1Cr22Mn16N高氮钢激光焊接II.焊缝组织与性能

为了研究高氮钢激光焊接接头焊缝区组织、性能特性，利用CO2激光对1Cr22Mn16N高氮钢进行了焊接，研究了焊接热输入和保护气体组成对焊缝组织、性能的影响。结果表明，高氮钢激光焊接焊缝组织均为奥氏体和少量的占铁素体。当焊接热输入增大时，占铁素体的尺寸显著增大。高氮钢激光焊接接头均没有出现软化区。随着热输入的减小，焊缝区的平均硬度升高；随着保护气体中氮气比例增大，焊缝区的硬度增加。当热输入减小时，焊缝韧性上升，而保护气体的组成对焊缝冲击吸收功的影响不大。     

工艺参数对304L不锈钢GTAW熔覆金属中铁素体含量的影响

奥氏体不锈钢焊缝金属的铁素体含量和形态会显著影响其性能,为探究焊接工艺参数对焊缝内铁素体数的影响规律,文中对304L不锈钢在氩氮混合气体保护下进行了GTAW工艺试验,研究了保护气中的氮气含量、电弧电压和焊接速度三个主要工艺参数对熔覆金属中铁素体含量及微观组织的影响规律。结果表明,增大混合保护气中氮气百分比或增大电弧电压均可使熔覆金属铁素体数减小,而增大焊接速度可使熔覆金属铁素体数增大;在多层多道焊情况下,由于存在层间的焊接热循环影响,熔覆金属平均铁素体数的实测值要低于WRC-1992的预测结果;基于磁测量原理的铁素体检测仪在测量薄板熔覆金属铁素体数时,测量结果会低于实际铁素体数,并且测量值会随焊缝金属截面积减小而减小。     

1Cr22Mn16N高氮钢激光焊接——Ⅱ.焊缝组织与性能

为了研究高氮钢激光焊接接头焊缝区组织、性能特性,利用CO2激光对1Cr22Mn16N高氮钢进行了焊接,研究了焊接热输入和保护气体组成对焊缝组织、性能的影响.结果表明,高氮钢激光焊接焊缝组织均为奥氏体和少量的δ铁素体.当焊接热输入增大时,δ铁素体的尺寸显著增大.高氮钢激光焊接接头均没有出现软化区.随着热输入的减小,焊缝区的平均硬度升高;随着保护气体中氮气比例增大,焊缝区的硬度增加.当热输入减小时,焊缝韧性上升,而保护气体的组成对焊缝冲击吸收功的影响不大.     

磁场作用下2205双相不锈钢焊缝成形与组织特征

采用摆动电弧GTAW对2205双相不锈钢进行了自熔焊接.研究了不同励磁电流下焊缝截面的特征以及其对焊缝组织的影响.结果表明,摆动电弧可以促进接头的熔合,但随着励磁电流增加,熔合效果逐渐变差.摆动电弧可促进2205双相不锈钢焊缝中奥氏体的析出并可使铁素体得到细化,在励磁电流1 A下,效果最佳.奥氏体含量的增加缓解了由于相比例失衡所致的硬度值升高,使得焊缝硬度更加接近母材.     

高锰奥氏体超低温钢焊接接头的组织和力学性能

用金相、扫描电镜、X射线衍射仪及硬度测试、低温拉伸等方法研究了32Mn-7Cr-0.60Mo-0.3N奥氏体钢TIG焊接接头的组织及低温力学性能，结果表明，采用氮－氩混合气体保护的TIG焊接方法可获得满意的接头组织和性能。接头的金相组织致密、均匀，无裂纹、气孔等缺陷；77K温度拉伸断口为韧窝为主的韧性断裂特征。保护气氛中添加一定比例的氮气可有效抑制焊接中氮含量的降低，保证较高的低温强度，77K温度下光滑试样的拉伸强度为1150MPa。保护气氛中合适的氮气添加比例为4％。接头的组织稳定性很高，焊接前后的焊缝和热影响区以及低温拉伸试样断口变形区均保持全奥氏体组织。     

Effect of nitrogen addition to shielding gas on residual stress of stainless steel weldments

Abstract

The objective of the present study was to investigate the effect of nitrogen additions to the shielding gas on the ferrite content and residual stress in austenitic stainless steels. Autogenous gas tungsten arc (GTA) welding was applied on austenitic stainless steels 304 and 310 to produce a bead on plate weld. The delta ferrite content of the weld metals was measured using a Ferritscope. The residual stress in the weldments was determined using the hole drilling strain gauge method. The present results indicated that the retained delta ferrite content in type 304 stainless steel weld metals decreased rapidly as nitrogen addition to the argon shielding gas was increased. The welding residual stress increased with increasing quantity of added nitrogen in the shielding gas. It was also found that the tensile residual stress zone in austenitic stainless steel weldments was extended as the quantity of added nitrogen gas in the argon shielding gas was increased.     

高氮奥氏体不锈钢氩弧焊的重熔特征

焊接性是影响高氮奥氏体不锈钢(高氮钢)应用的一个重要因素.为了研究高氮钢的焊接特性,对此钢进行氩弧焊重熔试验,分析了熔融时间对焊缝特性的影响.试验结果表明,随着熔融时间的增加,焊缝中铁素体的含量增加.同时发现焊缝中存在热裂纹、气孔等焊接缺陷.低熔点硫化物共晶相是焊缝具有较强裂纹敏感性的主要原因.熔融时间显著影响焊缝中气孔的形成.     

氮对316L不锈钢焊缝凝固模式和组织的影响

采用氮含量不同的三种焊丝分别对316L奥氏体不锈钢进行了TIG焊接,通过金相显微镜和扫描电镜对其焊缝微观组织进行了观察,对比分析了焊缝的凝固模式和焊缝组织的析出行为,研究了氮对焊缝凝固模式和组织的影响.结果表明,焊缝氮含量为0.018%时,焊缝的主要凝固模式为初生相为铁素体的FA模式,δ铁素体以蠕虫状或网状分布于枝晶轴上;氮含量增加到0.088%和0.16%时,焊缝的主要凝固模式转变为初生相为奥氏体的AF模式,δ铁素体以颗粒状分布于初生奥氏体枝晶间,其数目明显减少;焊缝奥氏体组织随着氮含量的增加有明显的粗化趋势.     

焊接工艺对TP304/SS400异种钢焊接接头组织和性能的影响

利用扫描电子显微镜并通过常温拉伸弯曲、低温冲击以及显微硬度等试验研究了FCAW，SMAW和GTAW三种不同的焊接工艺对TP304/SS400异种钢焊接接头组织和性能的影响. 结果表明，三种焊接工艺条件下，焊缝金相组织都为δ铁素体+奥氏体，但δ铁素体含量及形态分布有明显差异；FCAW焊缝中蠕虫状δ铁素体和GTAW焊缝中针状δ铁素体可有效提高韧性，故冲击韧性较高，SMAW焊缝中骨骼状δ铁素体对韧性不利，冲击韧性最低，且随冲击吸收能量的降低断口由韧性断裂转变为脆性断裂；三种焊接工艺条件下，焊接接头综合力学性能表现良好，整体显微硬度值变化不大.     

Influence of nitrogen addition on microstructure and pitting corrosion resistance of austenitic weld metals

A study to investigate the role of nitrogen in improving the pitting corrosion resistance of types 316 and 304 stainless steel weld metals has been attempted. Weld metals were prepared by autogenous TIG welding process with argon-nitrogen mixture as the shielding gas. Delta-ferrite measurements, made with Magne-Gage, showed the absence of delta-ferrite in all the samples of type 316 ss weld metal whereas for type 304 ss it decreased from 3.8 to 0 FN with increase in the levels of nitrogen. Potentiodynamic anodic polarization studies carried out on weld metal samples in deaerated neutral chloride medium showed improved resistance to pitting attack with increase in the amount of nitrogen. This improvement in pitting resistance could be due to the dissolution of nitrogen and formation of inhibiting compounds at the pit sites. The ESCA results of the anodically polarized weld metal samples showed the presence of nitrogen in a compound form. SEM and optical microscopic studies of the pitted samples showed that the initiation sites for pitting attack were triple points, austenite centres and delta-ferrite/austenite interfaces.     

焊丝含氮量及焊接电流对高氮钢焊缝组织和性能影响

针对高氮奥氏体不锈钢焊接过程中由于N元素逸出引起气孔、导致力学性能恶化的问题,利用相图计算软件设计并制备了含氮量为0.35%和0.85%两种奥氏体不锈钢焊丝,系统地研究了氮含量和焊接电流对高氮钢焊缝气孔倾向性、微观组织以及力学性能的影响规律. 结果表明,高氮钢焊缝气孔倾向和力学性能与焊接电流、焊丝氮含量密切相关:随着焊接电流增加,氮含量0.35%的高氮钢焊缝抗拉强度和断后伸长率均增加,未出现气孔;而氮含量0.85%的高氮钢焊缝具有很高的气孔倾向,抗拉强度和断后伸长率变化不大,当焊接电流增大到一定值后,气孔倾向性明显降低.     

Effect of activating flux and shielding gas on microstructure of TIG welds in austenitic stainless steel

Abstract

The aim of this research is to study the effect of an activating flux, two shielding gases (100%Ar and 50%Ar z 50%He) and a range of weld currents on the microstructure of autogeneous A-TIG welds on an austenitic stainless steel. Metallographic, Mössbauer, X-ray diffraction and magnetic permeability methods were used in the study to evaluate ferrite content in the welds. The increase in welding current coarsened the microstructure and increased the retained ferrite content in welds made with and without flux. The activating flux increases the ferrite content and changes the distribution of ferrite in the welds. The influence of flux on ferrite content is less significant in Ar/He than in Ar shield welds. The process of filling steel samples, currently used in the Mössbauer method, drastically changes the microstructure of the parent and melted austenitic stainless steels.     

超级双相不锈钢多层多道焊接接头组织及腐蚀性能

选用2507超级双相不锈钢作为研究对象,研究钨极氩弧焊多层多道焊接接头的组织和腐蚀性能.采用两种不同保护气进行钨极氩弧焊,主要讨论焊接道次和氮气添加对组织和腐蚀性能的影响.结果表明,焊缝中心均有较高的奥氏体含量,其腐蚀速率是焊根部位的0.68倍;盖面和焊根奥氏体含量相近,但盖面由于其弥散且尺寸相对较大的晶内奥氏体表现出更好的耐腐蚀性,焊根是焊缝金属的薄弱区域.混合区由于热影响区的存在腐蚀速率最快.保护气中氮气的添加促进了奥氏体的生成,降低了腐蚀电流密度一个数量级,提高了整体的腐蚀性能.     

Effect of shielding gas and activating flux on weld bead geometry in tungsten inert gas welding of austenitic stainless steels

Abstract

The aim of this study was to investigate the influence of three shielding gases (argon and argon–hydrogen and argon–helium mixtures) and two activating fluxes (a commercial flux and a TiO₂ based flux) on the geometry of welds produced by the tungsten inert gas (TIG) welding process on several casts of austenitic stainless steel AISI 316, using currents ranging from 100 to 300 A. Penetration depth increases with increasing current for all shielding gases, but weld depth to width ratio is higher for argon than for argon–hydrogen shielded welds. Both activating fluxes produce a substantial increase in penetration depth and in depth to width ratio of the welds. No correlation was found between penetration depth and oxygen content in the melted material. Some interaction exists between activating fluxes and shielding gases, which can affect the weld geometry and/or the defect formation in the welds.