深冷处理时间对镁合金MIG焊接接头耐腐蚀性的影响

针对镁合金焊接接头耐腐蚀性差的问题,采用液氮作为制冷剂,在-190℃对AZ31镁合金MIG焊接接头进行了不同时间的深冷处理,随后在3.5％的NaCl腐蚀液中进行全浸腐蚀试验,通过失重法、微观金相观察以及XRD分析等探讨了深冷处理时间对镁合金焊接接头耐腐蚀的影响.试验结果表明:合理控制深冷处理时间可以提高镁合金焊接接头的耐腐蚀性,其中经过(-190℃、6h)深冷处理后的焊接接头耐腐蚀性较好.     

7A52铝合金交流钨极氩弧焊焊接电流对焊接接头组织性能的影响

采用交流钨极氩弧焊对7A52铝合金板进行焊接,通过对不同焊接电流得到的焊接接头显微组织和显微硬度的分析,得出焊接电流对焊接接头组织性能的影响.试验结果表明,当焊接电流为140～160 A时,得到的焊缝组织较均匀,晶粒排列较紧密,焊接接头性能较好.     

CMT+P焊接电流对5083铝合金焊接接头组织及力学性能的影响

采用不同焊接电流,对3 mm厚5083-H116铝合金板材进行CMT+P焊接试验,并对接头显微组织、拉伸性能、弯曲性能等进行检测。结果表明,焊接电流对接头力学性能和焊缝中心晶粒尺寸有显著影响;焊接电流增大,抗拉强度降低,焊缝中心晶粒尺寸增加。通过对CMT+P焊接参数进行调整,可以获得满足使用要求的焊接接头,抗拉强度281 MPa,达到母材的84.38%;屈服强度163 MPa,达到母材的67.92%;伸长率13.5%,达到母材的75%;焊缝中心为等轴晶,熔合线内侧为柱状晶。      

固溶时效态GH925/Inconel625异种合金焊接力学性能研究

采用氩气保护焊(MIG)和625专用焊丝,研究GH925合金圆柱搭接焊接电流、道次间隔时间(T=1～2 s)对焊结区组织成分、析出相对焊接接头力学性能的影响。研究表明,固溶时效态GH925合金采用625专用焊丝可以得到熔合良好的焊接接头,接头抗拉强度最高达到830 MPa,达到焊丝抗拉强度的1.15倍。焊缝区组织由奥氏体γ相和弥散析出δ相组成,焊接电流50 A时焊缝区以平面晶析出为主,出现晶界多边化现象;焊接电流65 A时焊缝为胞晶组织,焊接电流65和80 A时靠近熔合线母材一侧2～3 mm处出现δ相带状剧烈析出区,与δ析出温度范围有关。能谱分析表明析出相为(NiFeCr)固溶型复杂化合物。增加道次间隔时间T有利于获得力学性能更好的焊缝组织。     

304不锈钢焊接接头的耐应力腐蚀性能

碳钢/304不锈钢复合管如果不锈钢钢管的焊接工艺参数不当,焊接接头便容易发生应力腐蚀。采用钨极氩弧焊方法焊接了304不锈钢钢管,通过慢应变速率拉伸和双环动电位再活化试验研究了不同焊接工艺参数焊接接头的耐应力腐蚀性能。结果表明,可有效提高耐应力腐蚀性能的最优焊接工艺:氩气流量为12~15 L/min,焊丝为ER308,焊接电压为50 V,电流为50 A,焊接速度为8~10 cm/min;选择合适的焊丝和降低焊接电流可有效增加304不锈钢焊接接头处的耐应力腐蚀性能。     

30CrMnSiNi2A与Q235异种钢焊接接头组织与性能分析

目的探讨30CrMnSiNi2A与Q235异种钢焊接接头的组织与性能。方法采用手工电弧焊对两者进行焊接,为了获得性能良好的焊接接头,焊前对其进行焊前预热,焊后对其进行焊后退火。通过X射线探伤检测,拉伸、冲击试验,显微硬度检测及光学显微镜金相分析等一系列工艺试验,对焊接接头进行研究。结果焊缝质量等级达到Ⅰ级;焊缝组织为先共析铁素体、针状铁素体、珠光体组织;30CrMnSiNi2A侧热影响区组织为回火索氏体,粗晶区组织片层厚度大于细晶区组织片层厚度;Q235侧热影响区由不完全重结晶区、细晶区、粗晶区组成。结论 30CrMnSiNi2A与Q235钢焊接后,获得了工艺性、力学性能良好的接头,可运用于2种材料焊接的实际生产。     

TC1 电阻微焊接接头显微组织及力学性能

目的 研究不同工艺参数（焊接电流、焊接时间）对金属箔材精密电阻微焊接头机械性能的影响。方法 采用电阻微焊接技术对0.05 mm 厚的TC1 箔材进行点焊连接试验,通过拉伸-剪切试验对焊接接头进行力学性能检测,利用硬度网格法结合金相观察,对焊接不同区域进行有效预测。结果 当焊接电流为400 A时,焊核直径随着焊接时间的增加而明显增大,而采用更高的焊接电流时,焊接时间对焊接直径没有显著影响。焊点接头的剪切力随着电流的增大而增大;在所有参数条件下,过长焊接时间都造成了焊点接头剪切力不同程度的减小。此外,由于微观组织的变化,不同焊接区域显现出不同硬度值,其中焊核硬度>母材硬度>热影响区硬度。结论 焊接电流对TC1 电阻微焊接接头力学性能影响较大;硬度网格法可以有效预测焊接不同区域。     

X90钢级管线钢预精焊接头的性能研究

为综合研究X90管线钢的焊接性,选用国内某钢厂轧制的X90管线钢卷板,利用预精焊工艺制备试验钢管4根,采用金相分析、扫描电镜(SEM)断口分析、夏比V型缺口冲击试验、拉伸、弯曲、硬度等试验,研究了焊接接头各个区域的组织和性能.试验结果表明:内外焊缝区组织均为针状铁素体,热影响区(HAZ)粗晶区晶粒粗化严重,主要组织为粒状贝氏体和贝氏体铁素体,在原奥氏体晶界和贝氏体板条内部存在块状或条状的(马氏体-奥氏体)M-A组元;HAZ冲击功离散性较大,出现了单值较低(45 J)的试样,SEM断口分析呈现典型的解理断裂特征;焊接接头抗拉强度805~815 MPa,断裂位置均在HAZ;焊接接头反弯试样易在HAZ出现裂纹和脆断现象;HAZ硬度在220~250 HV之间,较母材下降30 HV左右.HAZ是X90预精焊钢管焊接接头的薄弱环节,为提高X90管线钢的焊接稳定性,应重点研究精焊内外热循环双热影响亚区的组织转变和脆化机理.     

焊接方法对X90管线钢焊接接头性能的影响

目前,关于焊接方法对X90管线钢焊接接头组织性能的影响相关报道较少。采用手工电弧焊(SMAW)、熔化极气体保护焊(GMAW)、埋弧焊(SAW)3种焊接方法对X90管线钢进行对接焊。利用金相显微镜(OM)、扫描电镜(SEM)及能谱仪(EDS)对焊接接头及冲击断口进行显微组织及成分分析,分析了焊接方法对X90管线钢焊接接头组织性能的影响规律。结果表明:焊缝区组织主要为粒状贝氏体和针状铁素体;SMAW粗晶区组织主要为多边形铁素体、粒状贝氏体及M/A组织,GMAW和SAW粗晶区组织主要为粗大的铁素体、粒状贝氏体及板条贝氏体;3种焊接接头硬度分布趋势一致,盖面层硬度最高;SMAW、GMAW和SAW焊接接头抗拉强度依次为714,771,790 MPa,断后伸长率依次为23.3%,22.9%,20.0%;SAW与GMAW熔合线处20℃冲击吸收功比SMAW高约40 J,断裂机制为微孔聚集型,在韧窝底部有金属碳化物粒子析出。     

转向架构架焊接接头的组织与性能

采用工艺试验,力学性能试验以及光镜、电镜等显微分析等方法对转向架构架焊接接头的组织形态和力学性能进行了研究,确定了焊接接头各区的组织形态和力学性能的变化情况。研究结果表明,利用(Ar CO2)混合气体保护焊焊接Q345E钢时,焊缝组织主要为先共析体素体、针状铁素体和珠光体,热影响区组织主要为先共析铁素体、珠光体和粒状贝氏体,焊接接头具有良好的力学性能。     

The influence of laser welding parameters on the microstructure and mechanical property of the as-jointed NiTi alloy wires

The Nd:YAG laser welding was used to join the binary NiTi alloy wires with different compositions(Ti-50.0 at.%Ni and Ti-50.9 at.%Ni) which had the same diameter of 1 mm. The wires were welded with different parameters, including impulse width and welding current. The aim was to assess the influence of the laser-welding process on the microstructure and mechanical properties of the welded joint of binary NiTi wires. The optical microscopy (OM) and the metallographic microscopy (MM) were used to analyze the microstructure of the welded joints. The tensile test and the differential scanning calorimetry (DSC) were carried out to examine the ultimate tensile strength and the reverse martensitic transformation temperatures of the welded joints. It was found that the welding current and the impulse width had great influence on the quality of the welded joints, an optimal parameter combination would remove the pores and micro-cracks appeared in the fusion zone, and result in good mechanical properties such as higher fracture strength and elongation. The laser welding had a few effect on the reverse martensitic transformation temperatures of the welded joints.     

焊接速度对 7A52 铝合金 FSW 组织及力学性能的影响

目的在保证搅拌速度一定时,针对8 mm厚的7A52铝合金,在不同焊接速度下采用搅拌摩擦焊(FSW)进行焊接试验,研究其焊接接头的显微组织及力学性能。方法利用搅拌摩擦焊机进行对接焊接,焊后制取金相试样观察焊接接头宏观形貌和显微组织,并测定其力学性能。结果7A52铝合金FSW焊接接头焊核区的面积随着焊接速度的增大而增大,当焊接速度为250mm/min时,焊接接头的焊核区面积最大,焊核区的显微组织都为细小的等轴晶,焊接接头横截面的焊核区呈明显"洋葱环"的形貌,而热力影响区的结构特征则呈现出了较高的塑性变形流线层。焊接接头显微硬度分布都呈现出"W"形变化,在焊接速度为150 mm/min时,焊接接头的平均抗拉强度能达到452 MPa,达到了母材抗拉强度的89%。结论通过对不同焊接速度下7A52铝合金FSW焊接接头的组织和性能进行研究,得到了不同焊接速度下焊接接头组织和力学性能。     

奥氏体不锈钢A-TIG焊工艺研究

目的研究焊接参数对焊缝成形和接头宏观组织的影响。方法改变焊接电流、焊接速度、焊接电压以及活性剂中的一个参数,固定其他3个参数不变,对奥氏体不锈钢进行焊接,分析其接头宏观形貌、组织和力学性能。结果随着电流、电压的增加,焊接接头的熔深和熔宽都在增加,随着焊接速度的增加,焊接接头的熔深和熔宽都在降低,在相同参数下,将不同活性剂下的A-TIG焊接头的熔深和熔宽进行比较,发现涂敷C4活性剂接头熔深最大达到4.29mm,而常规TIG焊接头熔深为1.38mm,涂敷C4活性剂的接头熔深为TIG焊的3.11倍,且熔宽也有所减小。结论 C4活性剂A-TIG最佳工艺参数为:I=175 A,U=14 V,v=80 mm/min,此时能将6 mm板材焊透,成形良好,在此工艺下焊缝等轴晶范围最大,焊缝组织最为细小。相比于TIG焊,涂敷C4活性剂接头强度系数提升4.1%。     

中间层锌箔对铝-钛异种接头微观组织和力学性能的影响

本文旨在通过改善焊接工艺,提高铝-钛接头性能,扩大铝-钛复合件的应用范围.通过在铝-钛熔钎焊接工艺中添加锌箔,探讨了中间层锌箔对铝-钛接头微观组织和力学性能的影响.采用TIG焊机对铝/钛异种金属板材进行熔钎焊接实验,利用金相显微镜、扫描电镜、能谱仪、维氏硬度计和电子拉伸机对铝/钛接头的微观组织和机械性能进行分析.研究发...     

Achieving ultra-high strength friction stir welded joints of high nitrogen stainless steel by forced water cooling

The microstructure and properties of water-cooled and air-cooled friction stir welded (FSW) ultra-high strength high nitrogen stainless steel joints were comparatively studied. With additional rapid cooling by flowing water, the peak temperature and duration at elevated temperature during FSW were significantly reduced. Compared to those in the air-cooled joint, nugget zone with finer grains (900 nm) and heat affected zone with higher dislocation density were successfully obtained in the water-cooled joint, leading to significantly improved mechanical properties. The wear of the welding tool was significantly reduced with water cooling, resulting in better corrosion resistance during the immersion corrosion test.     

Microstructure and mechanical properties of friction spot welding aluminium–lithium 2A97 alloy

In this study, we investigated the microstructure and mechanical properties in different regions of the friction spot welded 2A97 aluminium–lithium alloy subjected to different heat treatment processes. The 2.0 mm thick hot-rolled sheet of 2A97 alloy was successfully welded using friction spot welding method with optimised welding parameters. Afterwards, the as-welded 2A97 joints experienced two subsequent heat treatment procedures: solution and ageing; directly ageing. The corresponding microstructure and mechanical properties of the heat-treated specimens were studied by means of optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM), hardness test and tensile test. The results show that the mechanical properties of the 2A97 joints before and after heat treatment were significantly modified, which was mainly related to fine-grained microstructure, size and type of precipitates, and dislocation density. Compared to the base material and the material that only experienced direct ageing, the whole friction spot welded 2A97 joint after solution and ageing treatment delivered better mechanical properties.     

Effect of Tool Pin Profile and Tool Rotational Speed on Mechanical Properties of Friction Stir Welded AA6061 Aluminium Alloy

AA6061 aluminium alloy (Al-Mg-Si alloy) has gathered wide acceptance in the fabrication of light weight structures requiring a high strength-to-weight ratio and good corrosion resistance. Compared to many of the fusion welding processes that are routinely used for joining structural aluminium alloys, the Friction Stir Welding (FSW) process is an emerging solid state joining process in which the material that is being welded does not melt and recast. This process uses a nonconsumable tool to generate frictional heat in the abutting surfaces. The welding parameters such as tool rotational speed, welding speed, axial force, etc., and tool pin profile play a major role in deciding the joint properties. In this investigation, an attempt has been made to study the effect of rotational speed and tool pin profile on mechanical properties of AA6061 aluminium alloy. Five different tool pin profiles (straight cylindrical, tapered cylindrical, threaded cylindrical, triangular, and square) have been used to fabricate the joints at five different tool rotational speeds (800-1600 RPM). Tensile properties, microhardness, and microstructure of the joints have been evaluated. From this investigation it is found that the joints fabricated using square pin profiled tool with a tool rotational speed of 1200 RPM exhibited superior mechanical properties compared to other joints.     

X65管线钢管闪光对焊工艺参数对焊接接头力学性能和缺陷的影响

利用正交试验法,研究了焊接工艺参数对X65管线钢管闪光对焊焊接接头力学性能的影响。正交试验中选择激发闪光阶段烧化量、稳定闪光阶段烧化量、稳定闪光阶段焊接电流、加速闪光阶段闪光速度作为试验因素,焊接接头抗拉强度、塑性和低温冲击韧性作为焊接工艺的评价指标,得到了最优的焊接工艺参数。接头的金相分析表明,焊接的高热输入使接头焊缝区和部分热影响区的晶粒粗化,形成魏氏组织,降低了接头的冲击韧性。刻槽锤断试验表明,灰斑缺陷内部和边缘的密集裂纹导致接头脆性解理断裂。加速闪光阶段优化的闪光速度有利于减少焊缝区内的缺陷并提高接头的力学性能。     

Mechanical properties of friction stir butt welds of high nitrogen-containing austenitic stainless steel

In this study, the friction stir butt welding of 2-mm-thick high nitrogen-containing stainless steel (HNS; Ni-free austenitic stainless steel containing 1 mass% nitrogen) plates was performed using a load-controlled friction stir welding (FSW) machine with a Si₃N₄-based tool at various welding speeds, i.e., 50 mm/min, 100 mm/min, 200 mm/min and 300 mm/min, and a constant tool rotating speed of 400 rpm. To determine the optimum welding conditions to create reliable HNS FSW joints, the effect of the heat input on the mechanical properties of the HNS FSW joints was studied. The mechanical properties were evaluated by the Vickers hardness test and the tensile strength test. Full-penetrated and defect-free butt welded joints were successfully produced, under all the applied welding conditions. The stir zones consisted of very fine grained structures and showed an increase in the Vickers hardness. These joints also showed a higher tensile strength and yield strength than the base metal. In particular, the FSW welds obtained at a welding speed of 100 mm/min, which showed the best mechanical properties, had a relatively higher Vickers hardness, which indicates a good relationship between the welding parameter (heat input) and the hardness profile due to the microstructure refinements. It was estimated that these welding conditions were optimal, and under these conditions both grain growth and α-phase formation were prevented.