Carbide precipitates and mechanical properties of medium Mn steel joint with metal inert gas welding

Medium Mn steel was metal inert gas(MIG)welded with NiCrMo-3 and 307Si filler wires.The effect of filler wires on the microstructure and mechanical properties of joint was investigated,and the carbide precipitates were contrastively discussed.The results revealed that the microstructure of weld metal,heat-affected zone and base metal are austenite.Obvious grain coarsening occurred in the heat-affected zone(HAZ),and the maximum grain size grew up to 160 pm.In HAZ,C and Cr segregated at grain boundaries,the carbides was identified as Cr7C3.The dispersive(Nb,Mo)C phase was also found in weld metal with NiCrMo-3 filler wire.All the welded joints failed in HAZ during tensile tests.The tensile strength of welded joint with NiCrMo-3 filler wire was 675 MPa,which is much higher than that with 307Si filler wire.In comparison to base metal,higher microhardness and lower impact toughness were obtained in HAZ for these two welded joints,which was attributed to the precipitation of Cr7C3 phase and grain coarsening.The impact toughness around the fusion line is the worst for these two welded joints.     

Effect of the welding mode and filler content on the structure of microalloyed Nb/Ti steel weldments

We describe the changes in the proportions of some microconstituents in the structure of the weld metal and the heat-affected zone and analyze the mechanical and technological properties of the welded joints of high-strength microalloyed Nb/Ti steel made by the E-process and MAG-process of welding with modification of the composition of the filler and welding parameters. The influence of different structures of the filler material and welding parameters on the microstructures of the HAZ and weld metal is studied with an aim to explain the changes in the mechanical and technological properties of the welded joints of microalloyed Nb/Ti steel.     

Weldability and properties of martensitic/austenitic stainless steel joints

Abstract

A series of studies has been carried out to examine the weldability and properties of dissimilar steel joints using martensitic and austenitic stainless steels F6NM (OCr13Ni4Mo) and AISI 347, respectively. This type of joint requires good mechanical properties, corrosion resistance, and a stable magnetic permeability in addition to a good weldability. Weldability tests include weld thermal simulation of the martensitic steel to investigate the influence of weld thermal cycles and post-weld heat treatment (PWHT) on the microstructure and mechanical properties of the heat affected zone (HAZ); implant testing to examine the tendency for cold cracking of martensitic steel; and rigid restraint testing to determine hot crack susceptibility of the multipass dissimilar steel joints. The simulation results indicated that the toughness of the martensitic steel HAZ did not change significantly after the weld thermal cycles. The implant test results indicated that welds produced using nickel based filler show no tendency for cold cracking, whereas welds produced using martensitic or ferritic filler show such a tendency. Based on the weldability tests, a welding procedure (tungsten inert gas welding for root passes with HNiCrMo-2B wire followed by manual metal arc welding using ENiCrFe-3B coated electrode) was developed and a PWHT at 600°C for 2 h was recommended. Joints produced using the developed welding procedure are not susceptible to hot and cold cracking. After PWHT the joints exhibit both satisfactory mechanical properties and stress corrosion cracking resistance.

MST/1955     

NM360钢与Q345钢异种钢焊接接头组织与性能研究

为了解NM360钢与异种钢焊接应用过程中焊接接头的力学性能,本文对NM360调质钢和Q345热轧钢采用气体保护焊进行异种钢焊接,对焊接接头进行了力学性能试验及微观组织观察,并分析了NM360钢ICHAZ的软化机理.研究表明:Q345热轧钢焊接接头CGHAZ组织为贝氏体+魏氏组织,为HAZ硬度值最高的区域,FGHAZ和ICHAZ组织为P+F;NM360调质钢焊接接头CGHAZ组织为低碳马氏体,FGHAZ组织为低碳马氏体+少量的粒状贝氏体,晶粒细小,为HAZ硬度值最高的区域,ICHAZ组织为回火马氏体+铁素体+粒状贝氏体,铁素体组织是造成ICHAZ硬度值大幅度降低的原因.     

铜与奥氏体不锈钢异种材料电子束焊接

目的研究不同参数下铜钢电子束异种焊接以获得符合要求的接头质量。方法以无氧高导热铜(OFHC)和奥氏体不锈钢(304)作为研究对象,控制扫描幅值、焊接速度等工艺参数,采用500 Hz真空电子束偏束"O"形扫描焊接的方式进行焊接。结果在电子束偏钢侧0.2 mm,电子束流为17 mA,聚焦电流为501 mA,焊接速度为600 mm/min的参数下,添加半径为1 mm,频率为500 Hz的圆形扫描波得到了抗拉性能为310.9MPa、硬度大于180 MPa的优质焊接接头。结论不同参数下的接头宏观均出现焊缝上表面下陷缺陷,接头铜侧热影响区存在大量颗粒状、块状、条状的铜钢固溶体析出相,接头钢侧热影响区存在宽度随扫描波幅值减小而减小的黑色过渡带。     

铜/钢异种材料等离子弧焊接头显微组织分析

为实现铜/钢异种材料的优质连接,研究了铜/钢焊接接头的显微组织特点及其组成,试验采用LHM-200等离子弧焊系统对紫铜(T2)与不锈钢(304)异种材料进行焊接,然后通过光学金相显微镜及能谱分析仪,观察分析接头显微组织,研究其接头组织结构及组成.研究结果表明:铜/钢异种材料的等离子弧焊焊缝在铜一侧为平直的,而在钢一侧则为半χ型,在铜侧界面形成漩涡状;在焊接接头的形成过程中铜元素的迁移和扩散主要依靠钢液的流动所带动;焊接接头显微组织主要为奥氏体组织,弥散分布着块状和粒状的铜和钢的固溶体组织,和黑色鱼骨状的α相铁素体组织;焊缝区组织主要是以α、γ富铁相和ε富铜相固溶体组织的形式存在.通过实现发现最佳的焊接参数为:保护气流量与离子气流量分别为0.25 L/min和0.75 L/min,焊接电流为65 A,焊接速度为4 mm/s,焊接后的接头抗拉强度能达到174 MPa.     

不同填充材料下316LN/Inconel 718异种激光焊接头的显微组织与力学性能

目的研究不同填充材料下316LN/Inconel 718异种激光焊接接头的显微组织、显微硬度及室温拉伸性能。方法分别对316LN/Inconel 718异种材料在不填充焊丝、填充ER316LMn焊丝和填充HGH4169焊丝的情况下进行激光对接试验。采用XJP-2C型倒置光学显微镜观察不同填充材料下接头的显微组织,401MVD型数显显微硬度计测量不同填充材料下接头显微硬度,WDW-100型万能电子试验机测量不同填充材料下接头的室温拉伸抗拉强度,最终,对不同填充材料下316LN/Inconel718激光焊接接头的显微组织和力学性能进行对比分析。结果不填充焊丝与填充ER316LMn焊丝时,可获得外观成形良好的焊接接头;填充HGH4169焊丝时,接头外观成形稍差,但力学性能较好;不填充焊丝时,焊缝组织主要为柱状树枝晶、胞状晶和等轴树枝晶,填充焊丝时,焊缝组织主要为柱状树枝晶和胞状晶。填充焊丝和不填充焊丝情况下,316LN侧熔合区均会产生分层现象,而Inconel 718侧熔合区分层现象则不明显;当填充HGH4169焊丝时,焊缝的显微硬度值与抗拉强度值最大,焊缝填充ER316LMn焊丝时次之,不填充焊丝时最小。接头抗拉强度最大值为764.59 MPa,接头断裂方式为典型的韧性断裂。结论填充焊丝较不填充焊丝时,接头的力学性能有所提高,且填充HGH4169焊丝时,接头的力学性能达到最佳,但焊缝的宏观成形难以控制。     

不同强度级别双相不锈钢激光焊接头的组织与力学性能

目的 为了合理制定不同强度等级DP钢同种和异种接头的激光焊接工艺,研究激光焊接工艺对接头组织性能的影响。方法 采用SEM、硬度试验、拉伸试验等手段,研究不同强度等级DP钢同种和异种激光焊接接头的微观组织和力学性能。结果 对于同种DP钢激光焊接,由于接头各个区域经历的热循环不同,因此其马氏体体积分数和形态、含碳量等存在明显差异。在焊缝熔合区,由于冷却速度较高,因此马氏体体积分数较高且为细条状,硬度高于母材硬度。在热影响区,由于马氏体发生了回火分解,因此其硬度值低于母材硬度,且软化的程度和范围大小与DP钢的强度级别相关。软化的热影响区成为接头的薄弱区域,降低了接头的拉伸性能。在异种DP钢激光焊接接头中,焊缝熔合区的硬度也明显高于母材硬度。靠近高强度级别母材侧的热影响区范围更大,软化程度更明显,接头硬度分布不再对称。接头的抗拉强度与低等级DP钢母材的抗拉强度基本一致。结论 激光焊接工艺对不同强度等级DP钢同种和异种接头组织性能的影响存在较大的差异,DP钢强度级别越高,接头或接头对应侧的热影响区软化程度越明显,这在制定焊接工艺以及焊后处理工艺过程中需要予以考虑。     

焊接参数对铁素体不锈钢搅拌摩擦焊接头组织及性能的影响

对4mm厚T4003铁素体不锈钢进行搅拌摩擦焊接工艺实验,研究焊接参数对接头组织特征、硬度分布及常温和低温冲击韧性的影响。结果表明:接头搅拌区和热力影响区由铁素体和马氏体双相组织构成;接头搅拌区组织沿试样厚度方向存在非均质性,且随转速的降低及焊接速率的增加越发显著;转速从150r/min增加至250r/min,前进侧热力影响区组织呈现小梯度过渡趋势,无明显变形拉长特征。焊缝硬度分布相对均匀,其最高硬度为290HV,约为母材的1.87倍。焊接参数和温度对接头的冲击吸收功有较大影响:常温(20℃)下,热影响区为母材的90%～92%,搅拌区为母材的85%～103%;低温(-20℃)下,热影响区为母材的87%～97%,搅拌区为母材的82%～95%,表明焊缝区仍具有较好强韧匹配。     

An improvement in creep strength of thermo-mechanical treated modified 9Cr-1Mo steel weld joint

Modified 9Cr-1Mo steel weld joints generally experience the type IV premature failure in the intercritical region (ICR) of HAZ under long term creep exposure at high temperature. Possibility of improving the resistance of this joint to type IV cracking through thermo-mechanical treatment (TMT) of the steel has been explored. Weld joints have been fabricated from the TMT and conventional normalized and tempered (NT) steels using electron beam (EB) welding process. Creep tests have been carried out on NT and TMT steels joint at 923 K (650°C) and 110–100 MPa applied stress. Creep rupture life of the TMT weld joint was significantly higher than the NT steel weld joint. Significant variations of microstructural constituents such as M₂₃C₆ precipitate; lath structure and hardness across the joint have been examined in both the joints. The coarser M₂₃C₆ precipitate and lath, and subgrain formation in the ICR resulted in the soft zone formation and was predominant in the ICR of NT steel joint. The enhanced MX precipitation through TMT processing and reduction in coarsening of M₂₃C₆ precipitate under thermal cycle resulted in improved creep rupture strength of TMT steel weld joint.     

Creep resistance of similar and dissimilar weld joints of P91 steel

Abstract

Two experimental weld joints, a similar weld joint of 9Cr–1Mo steel and a dissimilar weld joint of 9Cr–1Mo and 2.25Cr–1Mo steels, were fabricated by the TIG+E method and post-weld heating was applied. Creep testing was carried out at temperatures ranging from 525 to 625°C in the stress range 40–240 MPa. Creep rupture strength was evaluated using the Larson–Miller parameter. Extended metallography including transmission electron microscopy was performed and critical zones were indicated where fractures were concentrated during the creep exposure. At high temperatures rupture of the dissimilar weldment occurred in the heat affected zone (HAZ) of the weld metal while rupture of the similar weldment was located in the HAZ of the parent material. The processes of recovery seem to be the main causes of decrease in creep rupture strength of both weld joints in comparison to the parent materials.     

铁路钢轨与辙叉过渡层焊接的研究

钢轨与辙叉的焊接 ,属于高碳钢和高锰钢异种金属材料的焊接 .由于二者材料本身的焊接性都较差 ,而且所要求的焊接工艺差异很大 ,再加上钢轨的被焊截面形状不规则 ,所以给焊接带来很大的难度 .采用手工电弧焊的方法 ,通过增加过渡层可降低焊接难度 ,简化焊接工艺 .对 60 0mm长的钢轨与辙叉试件进行了实焊 ,其结果达到或超过了相关标准的技术要求 ,从而证明采用增加过渡层的办法来解决高碳钢和高锰钢焊接是一种可行的办法 .     

SiCp/Al复合材料焊接综述

为实现SiCp/Al复合材料的高质量可靠焊接,推广SiCp/Al复合材料在各领域的应用,调研了国内外SiCp/Al复合材料不同焊接方法的研究现状。在熔化焊方面,国内外学者通过调整工艺参数、在焊缝中加入Ti元素发生诱发反应等方法,抑制了焊缝中Al4C3针状脆性相的形成,从而提高了焊接接头的力学性能。在搅拌摩擦焊方面,国内外学者针对不同材料设计了专用的焊接搅拌头,以保证它们具备高耐磨性与足够的冲击韧性,在焊接过程中不出现破损情况;关注了焊接过程中焊接头转速、焊接速度、轴向力与热输入等因素,以获得力学性能优秀、晶粒细小均匀的焊接接头。在扩散焊方面,国内外学者探究了中间夹层对焊缝界面间原子相互扩散的促进作用;采取不同工艺参数,以外加超声或电子束表面加热等方式促进了原子间的相互扩散,以获得力学性能优异的焊接接头,提高焊接效率。在钎焊方面,国内外学者通过探究钎料与SiCp/Al复合材料之间的润湿性来组合钎料与钎剂,通过化学腐蚀处理表面暴露颗粒增强相、在复合材料表面电镀金属等方法来增大钎料与增强相的润湿性、解决钎料铺展受阻的问题,以进一步提高钎焊焊接接头质量。     

钛/铝异种合金脉冲激光焊接接头裂纹产生机理

目的 对0.8 mm厚的Ti6Al4V钛合金和2 mm厚的AA6060铝合金薄板进行脉冲激光焊接,分析异种轻合金激光焊接裂纹产生的机理及界面结合机理。方法 采用扫描电镜、EDS能谱以及显微硬度计等微观表征分析方法,对焊接接头的形貌特征、成分以及显微硬度进行分析,探索焊接接头处裂纹产生的原因。结果 钛/铝脉冲激光焊接性较差,接头存在严重的裂纹缺陷,裂纹多集中在焊缝与铝母材交界处以及焊缝中心区域位置,主要以热裂纹为主;接头焊缝可能存在大量的Ti-Al金属间化合物以及少量未熔的钛,其界面层主要成分推测为层状TiAl和外层锯齿状的TiAl3;接头整个焊缝区域的平均显微硬度为HV0.1420,其硬度水平远远高于焊缝两侧铝合金母材,也高出钛合金母材很多。结论 钛铝金属间化合物使钛铝焊接接头焊缝区脆性增大,另外接头焊缝区存在较大的组织应力、热应力、拉压应力、拘束应力等复杂应力,致使焊缝内存在较严重的裂纹缺陷。     

Characterisation of dissimilar P91 and P92 steel welds joint

In the present study, dissimilar weld joint was prepared using the P91 and P92 steel plate of 8-mm thickness, using the multi-pass gas tungsten arc (GTA) welding with filler (weld 1) and autogenous tungsten inert gas welding (A-TIG) process (weld 2). Evolution of δ-ferrite patches was studied in weld zone and heat affected zone (HAZ) for both weld 1 and weld 2. Effect of varying post weld heat treatment (PWHT) duration was also studied on δ-ferrite patches and mechanical properties of the dissimilar weld joint. PWHT was carried out at 760°C. For weld 2, weld zone showed poor impact toughness and higher peak hardness as compared to weld 1. After the PWHT, a considerable reduction in hardness was obtained for both weld 1 and weld 2,while impact toughness of weld zone showed a continuous increment with PWHT duration. For weldments characterisation, optical microscope, scanning electron microscope (SEM) and microhardness tester were utilised.     

Influence of welding parameters on lap joint between Al and Ti alloys using low power fiber laser

Fiber laser beam welding has always been a user‐friendly and flexible method to join dissimilar materials despite differences in thermal coefficient. Many industrial applications such as automotive has replaced the conventional joining methods towards this because of the flexibility and reduction in time consumption. In the present study, dissimilar titanium alloy; Ti6Al4 V and aluminum alloy; AA2024‐0 were laser welded through a lap joint technique using a low power Yb‐fiber laser without any additional filler. The influence of welding speed on weld morphology was investigated using optical microscopy (OM) and scanning electron microscope (SEM). The cross‐section of the joints revealed that the fusion zone (FZ) and heat affected zones (HAZ) are wider when welding speed decreases with lower laser power. This result shows that the low power fiber laser has sufficient energy to melt the base materials, forming a liquid bridge to facilitate the smooth flow of molten metal between the top and bottom layer. Therefore, at lower welding speeds with constant low laser power, it was shown that there are possibilities of laser welding between two non‐ferrous metals.     

Characterization of microstructure,mechanical properties and corrosion resistance of dissimilar welded joint between 2205 duplex stainless steel and 16MnR

The joint of dissimilar metals between 2205 duplex stainless steel and 16MnR low alloy high strength steel are welded by tungsten inert gas arc welding (GTAW) and shielded metal arc welding (SMAW) respectively. The microstructures of welded joints are investigated using scanning electron microscope, optical microscope and transmission electron microscopy respectively. The relationship between mechanical properties, corrosion resistance and microstructure of welded joints is evaluated. Results indicate that there are a decarburized layer and an unmixed zone close to the fusion line. It is also indicated that, austenite and acicular ferrite structures distribute uniformly in the weld metal, which is advantageous for better toughness and ductility of joints. Mechanical properties of joints welded by the two kinds of welding technology are satisfied. However, the corrosion resistance of the weldment produced by GTAW is superior to that by SMAW in chloride solution. Based on the present work, it is concluded that GTAW is the suitable welding procedure for joining dissimilar metals between 2205 duplex stainless steel and 16MnR.     

Effect of laser welding parameters on fusion zone morphological,mechanical and microstructural characteristics of AISI 304 stainless steel

Nowadays, the Nd:YAG laser has been a promising key tool for joining thin components. In this research, mechanical and microstructural properties of laser welded thin austenitic stainless steel sheets were investigated with experimental investigations, as a function of laser welding parameters. Butt welded joints were made using a Nd:YAG laser in the pulsed wave mode. The appropriate laser welding parameters were found in order to obtain quality and strong weld seam. The pulsed laser seam welding process is controlled by a variety of parameters. We focus on the effects of the several processing parameters on mechanical and microstructural characteristics of joint and weld quality. The aim of this research was to evaluate the influence of these processing parameters on joint strength and microstructure. And also we examined the weldability of stainless steels in butt joint configuration by a pulsed Nd:YAG laser beam.     

13MnNiMoNbR与00Cr19Ni10异种钢焊接接头的组织与性能

首先将H309L焊丝堆焊在13MnNiMoNbR钢板坡口上,再将堆焊后的13MnNiMoNbR钢板与00Cr19Ni10钢板用H308L焊丝填充焊接,得到了13MnNiMoNbR与00Cr19Ni10异种钢焊接接头,并对接头的显微组织及硬度进行了分析。结果表明：13MnNiMoNbR钢板侧熔合线附近出现了粗大的铁素体组织,形成脱碳层,而H309L焊缝侧的奥氏体堆焊层熔合线附近出现了黑色的非常细小的碳化物析出层;由于碳化物的析出或是固溶碳,使H309L焊缝侧增碳层处的硬度明显升高。     

Interface microstructure evolution of dissimilar friction stir butt welded F82H steel and SUS304

The dissimilar butt welded joint of reduced-activation ferritic/martensitic steel (RAF/M) F82H and austenite stainless steel (AISI304 (SUS304)) were studied by friction stir welding. The effect of the position of the steels and tool plunging was considered in order to prohibit the mixing of the F82H and SUS304. When the dissimilar butt welding was performed such that the F82H plate was on the advancing side and the tool was plunged on the F82H side, defect-free joints could be successfully fabricated. Optical microscopy and EDX analysis were used to characterize the dissimilar joint microstructures and the interface. It was confirmed that the dissimilar joint formed no mixed structure and inter-metallic compounds.