随焊冲击碾压对LY12CZ铝合金接头组织和性能的影响

随焊冲击碾压是一种控制薄壁结构焊接应力变形、防止热裂纹的新方法.这种方法同时也改善了LY12CZ铝合金接头组织,提高了其力学性能.金相和拉伸断口SEM观察表明,随焊冲击碾压焊缝区晶粒明显细化,组织更加致密,气孔、缩松等缺陷大大减少.与常规焊接接头拉伸断口脆性和塑性断裂特征并存相比,随焊冲击碾压焊缝断口形貌呈现典型的塑性断裂的特征.随焊冲击碾压之后,接头区的硬度有了明显提高,表明接头软化区重新得到强化.而拉伸、疲劳和三点弯曲实验结果表明,随焊冲击碾压之后接头的抗拉强度、塑性及疲劳寿命等力学性能也都得到不同程度的提高.由于薄弱的焊趾部位得到强化,裂纹萌生位置也由焊趾转移到焊缝.     

10CrNi3MoV钢激光-MAG复合热源焊接技术研究

研究了船用10CrNi3MoV钢激光-MAG复合焊接头组织和力学性能,并与常规MAG焊接头进行了对比。结果表明,采用激光-MAG复合焊接工艺进行10CrNi3MoV钢焊接是可行的;与常规MAG焊相比,激光-MAG复合焊接头显微硬度明显升高,焊缝中心冲击韧性有一定下降,但仍能满足技术指标要求。为进一步改善焊接接头的综合性能,提出通过焊接材料成分优化,来降低焊缝金属淬硬倾向,提高接头的韧性水平。     

超薄不锈钢片的微激光焊接工艺研究

采用微型脉冲激光实现了0.2mm厚321不锈钢片的对接焊,并通过正交优化设计对工艺参数进行了优化,研究了工艺参数对焊接接头微观形貌及组织的影响。结果表明,焊接接头获得最大抗拉力的最优工艺参数是脉冲功率百分比为15、脉冲频率为5Hz、脉冲宽度为2.1ms,此时焊接接头的承载能力达到母材的95%。当微激光焊的脉冲能量过大时会产生热量的积累、导致焊缝发生烧穿,当脉冲宽度较小时激光脉冲的熔透能力较弱、导致焊缝未焊透,这两者都会导致焊接接头的承载能力较差。承载能力较高的焊接接头其显微组织由焊缝中心区的等轴晶和焊缝边缘细小的柱状晶组成。     

地铁立柱拼焊结构的焊接性

通过试验对地铁小立柱拼焊结构的焊接性进行了探讨,并提出相应的改善措施。试验结果表明：采用适当的焊接组装工艺,可大幅提高接头焊缝质量及生产效率。     

新型焊接工艺对不锈钢薄板焊缝成形及接头性能影响的研究进展

不锈钢薄板作为一种性能优越的节约型材料,广泛地应用于国民生产中的各个领域,具有良好的发展前景。基于不锈钢薄板的重要性,研究其焊接工艺对促进不锈钢薄板产业的发展具有重要意义。分析总结了焊接工艺对不锈钢薄板焊缝成形及接头性能影响的最新研究进展,表明:(1)激光焊接不锈钢薄板焊缝成形优于电弧焊,通过改进气体保护方式可提高焊缝成形质量,波形控制法可辅助改善电弧焊焊缝成形;(2)高能束焊、搅拌摩擦焊可极大地细化焊接接头晶粒,改善接头力学性能;(3)采用低热输入焊接工艺可以减轻焊接接头腐蚀敏感性,增加保护气体流量或外加磁场可提高电弧焊接头的耐腐蚀性。     

动态低应力小变形无势裂随焊锤击焊接技术研究

从力学角度出发,首次提出随焊锤击的焊接技术,并结合跨焊缝两侧横向位移的测量及显微组织的研究,分析了随焊锤击防止焊接裂纹的作用机理,试验结果表明,随焊狂击技术可显著地改善焊缝显微组织及残余应力分布,防止焊接热裂纹的产生,并能够有效地控制LY12CZ铝合金薄板焊接横向及纵向收缩变形,可以认为随焊锤击是一种更合理,更具实用价值的低应力小变形无热裂的焊接技术新方法。     

WQT-1衬垫单面焊接工艺研究

采用CO_2气体保护焊,通过x射线探伤,拉伸、弯曲、冲击试验、研究了WQT-1陶质衬垫的单面焊接工艺,反面焊缝成形质量以及焊缝化学成分与接头的机械性能。研究结果表明:烧结型WQT衬垫抗潮性能好,焊前不需烘干;焊接工艺的合理规范区间较宽,便于选择;反面焊缝成形美观,焊接质量稳定、可靠;接头性能优异。     

10Ni2CrMoV钢焊接接头腐蚀特性研究

通过室内挂片和电化学测试试验,结合微观分析,比较了手工焊和埋弧焊工艺制备的10N i2CrMoV钢焊接接头的腐蚀特征,讨论了相关因素的影响。结果表明:两种工艺的焊接接头均以焊缝金属的耐蚀性最差,热影响区的耐蚀性最好;接头各区中的化学成分和微观组织的差别,是导致接头各区耐蚀性差异的主要因素;埋弧焊接头的耐蚀性优于手工焊接头的,焊接过程中输入的线能量较高是主要原因。     

5A90铝锂合金激光焊搭接接头的组织和性能

以厚度为3.0和4.0 mm的5A90铝锂合金板为研究对象,系统地开展了铝锂合金双光点激光焊接工艺研究,并对激光焊搭接接头的组织和性能进行了分析。结果表明:通过合理的选择激光功率和焊接速度可保证焊接过程的稳定性,改善焊缝的成形质量;在母材半熔化区与焊缝柱状晶之间存在一条等轴细晶带,焊缝中心组织为等轴树枝晶,晶粒尺寸一般随激光功率的降低和焊接速度的增大而细化和均匀化。     

5083厚板TIG焊焊接工艺研究与应用

介绍了铝合金厚板(δ=28mm)TIG焊对接焊缝的工艺研究及应用。分析了大厚度5083材料的焊接工艺特点,采用合理的坡口形式,经过焊接工艺评定取得了较合理的工艺参数,最终焊制出了满意的焊接接头。     

Fatigue tests on steel plates with longitudinal weld attachment strengthened by ultra high modulus carbon fibre reinforced polymer plate

Welded steel connections of infrastructures are susceptible to fatigue failure. Advanced carbon fibre reinforced polymer (CFRP) has been demonstrated promising for fatigue strengthening of steel structures. Limited research was conducted on CFRP strengthening of welded connections. This paper focuses on the application of ultra high modulus (UHM) CFRP plates with a modulus of 460 GPa to strengthen steel plates with longitudinal fillet weld attachment using five CFRP strengthening configurations. A series of fatigue tension tests were carried out with constant amplitude fatigue loading. Beach marking technique was adopted to record the crack propagation process. Effects of CFRP bond length, bond width and bond locations on fatigue performance of welded steel joints were investigated. The experimental results showed that UHM CFRP plates could generally increase the fatigue life of the welded steel joints. It seems better to apply CFRP on the welding side of the specimen to achieve longer fatigue life. Then, the effects of weld and weld attachment on the CFRP strengthening efficiency was further studied by comparing experimental results of non‐welded steel plates with single side UHM CFRP plate strengthening. Finally, the classification method was adopted to assess the strengthening efficiency of the UHM CFRP plate to the steel plates with longitudinal weld attachment.     

Microstructural and mechanical characterization of electron beam welded Al-alloy 7020

The electron beam (EB) welding process is used to weld any metal that can be arc welded with equal or superior weld quality. EB welding is carried out in a high-purity vacuum environment, which results in freedom from impurities such as oxides and nitrides. Thus, pore-free joints can readily be achieved in metallic materials, such as Al-alloys and Ti-alloys. However, autogenous EB welding of some aluminium alloys leads to a significant strength reduction (undermatching) in the fusion zone due to the loss of strengthening phases. For such Al-alloys, the local microstructure-property relationships should be established to satisfy the service requirement of a welded component with strength undermatching. Autogenous EB welding was performed on 5 mm thick aluminium alloy 7020 plate. Microstructural characterization of the weld metals was made by optical and scanning electron microscopy. Extensive microhardness measurements were conducted in the weld regions of the joints which exhibited a hardness loss in the fusion zone due to the loss of strengthening phases. Tensile properties of the joints were determined by testing flat transverse tensile specimens at room temperature without machining the weld profiles. Furthermore, elastic-plastic fracture toughness tests (CTOD) were carried out on the base material and welded joints at room temperature.     

焊接方法对铝合金焊接接头微弧氧化色差的影响

目的 分析铝合金焊接接头微弧氧化过程中色差产生的原因。方法 采用单激光和激光-MIG复合焊2种焊接方法焊接2A12铝合金,利用RGB值定性描述不同焊接试样的色差差异大小,采用金相、SEM和微区XRD观察2A12铝合金单激光和激光-MIG复合焊接头微弧氧化前后的组织、微观形貌和表面物相组成。结果 经微弧氧化处理后,2A12铝合单激光焊焊件的焊缝和母材之间无明显色差,2A12铝合金激光-MIG复合焊焊件的焊缝和母材之间存在明显色差,结合金相组织、表面和截面的SEM形貌以及表面EDS和XRD测试分析结果可知,成分和表面熔融物颗粒的大小不同是铝合金焊接接头微弧氧化色差形成的主要原因,焊接接头的组织对铝合金焊接接头微弧氧化色差的产生没有影响。结论 单激光焊接接头微弧氧化后的氧化色差较激光-MIG复合焊接头的小;铝合金(2A12)焊接接头产生氧化色差主要是因为焊接接头的成分和表面熔融物颗粒大小不同,而组织对色差无影响。     

Cruciform fillet welded joint fatigue strength improvements by weld metal phase transformations

Arc welding typically generates residual tensile stresses in welded joints, leading to deteriorated fatigue performance of these joints. Volume expansion of the weld metal at high temperatures followed by contraction during cooling induces a local tensile residual stress state. A new type of welding wire capable of inducing a local compressive residual stress state by means of controlled martensitic transformation at relatively low temperatures has been studied, and the effects of the transformation temperature and residual stresses on fatigue strength are discussed. In this study, several LTTW (Low Transformation‐Temperature Welding) wires have been developed and investigated to better characterize the effect of phase transformation on residual stress management in welded joints. Non‐load‐carrying cruciform fillet welded joints were prepared for measurement of residual stresses and fatigue testing. The measurement of the residual stresses of the three designed wires reveals a compressive residual stress near the weld toe. The fatigue properties of the new wires are enhanced compared to a commercially available wire.     

TIG与FSW焊接工艺下2219铝合金疲劳裂纹扩展性能研究

目的 研究钨极惰性气体保护焊（TIG）和搅拌摩擦焊（FSW）对2219铝合金焊接接头疲劳性能的影响,并探究这2种不同焊接技术条件下焊接接头疲劳裂纹的产生与裂纹扩展原理,了解2种焊接接头的抗裂纹扩展能力,为工程实践应用提供数据参考。方法 采用疲劳裂纹扩展试验方法,测试上述2种焊接工艺条件下焊缝金属和热影响区组织的疲劳裂纹扩展速率da/d N和阈值,使用光学显微镜和扫描电子显微镜观察并分析金相组织和疲劳断口形貌特征。结果 疲劳裂纹倾向于沿裂纹处萌生,裂纹的存在成为主要的裂纹扩展源头,有利于加速裂纹向前延伸。热影响区由于组织结构不均匀,不同位置的晶粒尺寸存在明显差异,疲劳裂纹扩展路径倾向于沿靠近焊缝一侧向靠近母材区域扩展。TIG焊接工艺下焊缝金属和热影响区的裂纹扩展速率明显低于FSW焊接工艺下的焊缝金属和热影响区,与此同时,TIG焊接接头表现出优良的抗疲劳裂纹扩展性能。结论 通过此研究,建议2219铝合金焊接接头采用TIG焊接工艺,抗疲劳裂纹扩展效果更佳。     

DP590双相钢点焊接头的正交试验及超声检测分析

对DP590双相钢点焊接头进行正交试验,研究不同工艺因素对点焊接头失效载荷和焊核直径的影响,确定最优点焊工艺参数,并探讨点焊接头压痕深度的超声测量方法.采用超声波水浸聚焦入射法对1.5 mm厚的DP590双相钢点焊接头进行超声C扫描,获得接头焊核直径,利用超声A扫信号,计算点焊接头压痕深度,并与实际测量结果对比.研究表明:焊接参数对DP590点焊接头的失效载荷与焊核直径的显著性影响一致,从大到小依次为焊接电流、焊接时间、电极压力;DP590点焊接头最优的焊接工艺参数为:焊接时间70 ms,焊接电流15.0 k A,电极压力6.5 k N,在此参数下接头的抗拉强度为9 521.4 N;超声A扫信号计算得到的点焊接头表面压痕率与实际压痕率的误差在2.5%~9.7%,超声计算所得压痕深度与实际测量压痕率较为接近.     

结构钢焊接匹配性研究进展

对结构钢焊接的高强匹配和低强匹配两种技术路线的发展进行了综述。在焊缝金属具有足够韧性的情况下,高强匹配能利用焊缝金属的高强度降低位于焊缝中裂纹的扩展驱动力、从而有利于焊接接头抗断性能的提高;随着结构钢强度的提高,焊接冷裂纹敏感性增大、焊缝韧性降低,采用焊接裂纹敏感性相对较低、焊缝金属塑韧性相对较高的低强匹配焊接技术能较好的控制焊接冷裂纹的产生并保证接头的抗断性能。     

Evolution of microstructures and mechanical properties in similar and dissimilar friction stir welding of AA5086 and AA6061

In this work, thermo-mechanical behavior and microstructural evolution in similar and dissimilar friction stir welding of AA6061-T6 and AA5086-O have been investigated. Firstly, the thermo-mechanical behaviors of materials during similar and dissimilar FSW operations have been predicted using three-dimensional finite element software, ABAQUS, then, the mechanical properties and the developed microstructures within the welded samples have been studied with the aid of experimental observations and model predictions. It is found that different strengthening mechanisms in AA5086 and AA6061 result in complex behaviors in hardness of the welded cross section where the hardness variation in similar AA5086-O joints mainly depends on recrystallization and generation of fine grains in weld nugget, however, the hardness variations in the weld zone of AA6061/AA6061 and AA6061/AA5086 joints are affected by subsequent aging phenomenon. Also, both experimental and predicted data illustrate that the peak temperature in FSW of AA6061/AA6061 is the highest compared to the other joints employing the same welding parameters.     

Mechanical properties of friction stir butt‐welded Al‐5086 H32 plate

Al‐5086 H32 plates with a thickness of 3 mm were friction stir butt‐welded using different welding speeds at a tool rotational speed of 1600 rpm. The effect of welding speed on the weld performance of the joints was investigated by conducting optical microscopy, microhardness measurements and mechanical tests (i.e. tensile and bend tests). The effect of heat input during friction stir welding on the microstructure, and thus mechanical properties, of cold‐rolled Al‐ 5086 plates was also determined. The experimental results indicated that the maximum tensile strength of the joints, which is about 75 % that of the base plate, was obtained with a traverse speed of 200 mm/min at the tool rotational speed used, e.g. 1600 rpm, and the maximum bending angle of the joints can reach 180^o. The maximum ductility performance of the joints was, on the other hand, relatively low, e.g. about 20 %. These results are not unexpected due to the loss of the cold‐work strengthening in the weld region as a result of the heat input during welding, and thus the confined plasticity within the stirred zone owing to strength undermatching. Higher joint performances can also be achieved by increasing the penetration depth of the stirring probe in butt‐friction stir welding of Al‐5086 H32 plates.     

Effect of welding wire and groove angle on mechanical properties of high strength steel welded joints

Mechanical properties of high strength steel welded joints strictly depend on the welding process, the filler material composition and the welding geometry. This study investigates the effects of using cored and solid welding wires and implementing various groove angles on the mechanical performance of weld joints which were fabricated employing the gas metal arc welding process. It was found that weld joints of low alloy, high strength steels using low alloy steel cored welding wires exhibited higher tensile strength than that of low alloy steel solid wire and chromium‐nickel steel bare welding wire when the method of gas metal arc welding is employed. The effect of groove angle on the strength and toughness of V‐groove and double V‐groove butt‐joints was investigated. V‐groove joints, with higher tensile strength than double V‐groove joints in the whole range of groove angles, were superior in toughness for small groove angles, but impact toughness values of both joints were comparable for large angles. The effect of heat input and cooling rate on the weld microstructure and weld strength was also investigated by performing thermal analysis employing the commercial software ANSYS. It was concluded that cooling rate and solidification growth rate determined the microstructure of the weld zone which had great consequences in regard to mechanical properties.