Q235钢摩擦叠焊单元成形焊接接头金相组织分析

针对Q235钢开展了摩擦叠焊单元成形焊接试验并对在主轴转速5 000 r/min,塞棒进给速度0.3 mm/s条件下的焊接接头的显微组织和显微组织硬度进行了测试,分析了摩擦叠焊单元成形焊接接头中不同位置的金相组织结构与摩擦焊接过程中温度和压力之间的关系,以及接头中不同位置处显微组织硬度存在差异的原因 该研究对Q235钢摩擦叠焊焊接工艺参数的研究及提高焊接接头的质量具有一定的指导意义.     

焊后热处理对水下摩擦叠焊焊接接头质量的影响

基于摩擦叠焊技术特点,研究不同的焊后热处理工艺对水下摩擦叠焊焊接接头质量的影响。结果表明:焊后热处理能够明显细化水下摩擦叠焊焊接接头的组织晶粒,降低焊接接头的硬度,提高拉伸强度和弯曲性能。     

7075铝合金不同冷却介质条件下搅拌摩擦焊接头的组织与性能

针对3 mm厚7075铝合金板材,采用相同的焊接参数分别在空气和水中进行搅拌摩擦焊接,研究不同冷却介质对接头的热循环曲线、宏观形貌、微观组织、硬度以及力学性能的影响。结果表明,水下焊接的热循环曲线更趋于平缓,高温停留时间短。水下焊接的焊缝表面成形更好,焊核区(NZ)和热影响区(HAZ)显微组织的晶粒更为细小,接头热影响区更窄,并且接头的塑性流线更清晰,而空气中焊接的接头热影响区软化严重,硬度仅为113 HV。水下FSW接头断裂形式为脆性断裂,而空气中FSW接头断裂形式为韧性断裂。     

TC4钛合金高转速惯性摩擦焊接头组织及性能分析

采用高转速(3500～4300 r/min)惯性摩擦焊方法焊接TC4钛合金,观察了不同焊接工艺条件下焊接接头的显微组织,讨论了高转速条件下惯性摩擦焊接接头组织的形成机理,分析了焊接接头的性能.结果表明,TC4钛合金惯性摩擦焊焊接接头的形状呈"V"字型,焊缝区和热影响区的组织特征与低转速条件下的显微组织一致.焊缝组织沿径向变化,心部为细小的等轴晶,向外逐渐过渡为片状组织;焊缝区的硬度高于母材和热影响区;接头拉伸试样断裂于母材.     

不同环境下X65管线钢摩擦塞焊搭接焊接头组织和力学性能分析

为了研究摩擦塞焊搭接接头的金相组织和力学性能,分别在空气中和水下对圆锥形搭接试样进行试验. 结果表明,在空气中焊接时,没有焊接缺陷的产生;在水下焊接时,低的焊接工艺参数导致接头产生未填充和未连接两种焊接缺陷. 接头中焊缝和热影响区组织为上贝氏体,母材为细小的铁素体和珠光体组织. 接头的硬度分布为母材最低,热影响区次之,焊缝最高,水下搭接接头的硬度一般高于空气中接头的硬度. 在空气中焊接时,只有塞孔底部的拉伸试样断裂在结合线处;而在水下焊接时,靠近塞孔底部的两个拉伸试样在结合线处发生断裂.     

7075铝合金不同冷却介质条件下搅拌摩擦焊接头的组织与性能

针对3 mm厚的7075铝合金板材,采用相同的焊接参数分别在空气和水中进行搅拌摩擦焊接(FSW),研究不同冷却介质对接头的热循环曲线、宏观形貌、微观组织、硬度以及力学性能的影响。结果表明,水下焊接的热循环曲线更趋于平缓,高温停留时间短,焊缝表面成形更好,焊核区(NZ)和热影响区(HAZ)显微组织的晶粒更细小,接头热影响区更窄,并且接头的塑性流形更清晰,而空气中焊接的接头热影响区软化严重,硬度仅为113 HV。水下FSW接头断裂形式为脆性断裂,而空气中FSW接头断裂形式为韧性断裂。     

TC4线性摩擦焊接头的力学性能及组织变化特点

用自制的XMH-160型线性摩擦焊机进行了TC4线性摩擦焊试验研究.利用前期试验优化的工艺参数进行焊接,获得了100%焊合率的焊接接头.对焊后试件进行了拉伸性能试验,拉伸试件均断在远离焊缝的母材区,表明接头的力学性能指标超过了母材.对接头解剖后进行了组织分析和显微硬度测试,发现焊缝中部宽约60μm,边缘宽约110μm,焊缝两边的金属流线组织呈对称分布;焊缝中心区为α β超细晶组织,近缝区为不同程度的α β变形组织,但晶粒未明显长大;焊缝的显微硬度明显高于母材.接头组织的上述变化特点是拉伸力学性能和显微硬度均高于母材的主要原因.     

焊接工艺对TP304钢焊缝金属组织及性能的影响

针对TP304不锈钢,采用三种不同的焊接工艺方法,选取合适的焊接工艺参数,成功制备三组完整的焊接接头.通过X荧光化学成分分析、显微组织观察和显微硬度试验研究了不同焊接方法对TP304不锈钢焊缝金属组织和性能的影响.结果表明,不同焊接方法下焊缝合金成分有所差异,且分布不均;各焊层显微组织形态和晶粒大小差异较大;整个接头的硬度值分布并不均匀,焊缝高于热影响区,热影响区高于母材.三种焊接方法相比,TIG-MAG焊缝的硬度值最大,TIG-SMAW的最小.对于薄板不锈钢焊接,TIG-MAG组合焊法优选.     

超高强度钢35CrMnSi惯性摩擦焊接头组织与性能

对35CrMnSi超高强度钢进行了惯性摩擦焊试验研究,对热处理前后焊接接头组织、显微硬度进行分析测试,并对热处理后焊接接头进行了拉伸性能、冲击性能及拉伸断口分析。结果表明:焊后接头焊缝组织为板条马氏体与残余奥氏体,热力影响区组织为细小的马氏体、索氏体、珠光体和铁素体混合组织;热处理后焊缝组织为回火马氏体与少量铁素体;摩擦焊接头焊缝区的硬度高于热力影响区和母材,热处理后焊接接头硬度趋于一致,焊接接头抗拉强度大于1 890 MPa,断后伸长率大于7. 5%,焊缝区拉伸断口为混合断口;焊接接头冲击吸收能量大于18. 5J。     

2219-T4铝合金双轴肩FSW与常规FSW接头性能对比研究

对常规搅拌摩擦焊和双轴肩搅拌摩擦焊技术进行了比较,试验材料为6 mm厚2219-T4铝合金.对两种焊缝的微观结构、显微硬度和力学性能进行了测试.结果表明双轴肩焊缝的宏观形貌与常规搅拌摩擦焊焊缝的不同,呈哑铃型.且由于双轴肩焊接的热输入量较高,其接头的显微硬度和力学性能普遍低于常规搅拌摩擦焊接头.双轴肩搅拌摩擦焊接头的抗拉强度可达到常规搅拌摩擦焊接头的90%.     

Joint performance of laser-TIG double-side welded 5A06 aluminum alloy

The influence of welding parameters on mechanical properties and microstructure of the welds of laser-TIG double-side welded 5A06 aluminum alloy was investigated. The results show that the weld cross-sectional shape has an intimate relation with the mechanical properties and microstructure of the welds. The symmetrical "X" cross-section possesses a relatively higher tensile strength and elongation than the others, about 91% and 58% of those of base metal, respectively. The good weld profiles and free defects are responsible for the improvement of tensile properties. Due to low hardness of the fusion zone, this region is the weakest area in the tensile test and much easier to fracture. The loss of Mg element is responsible for the decrease of mechanical properties of the joints. The microstructure of "X" cross-section has an obvious difference along the direction of weld depth, and that of the "H" cross-section is consistent and coarse.     

Role of nickel as an interlayer in dissimilar metal friction welding of maraging steel to low alloy steel

Continuous drive friction welding of dissimilar metals, maraging steel and low alloy steel was carried out. It was observed that the hardness, ductility and impact toughness of maraging steel are low due to the diffusion of elements such as carbon, manganese, silicon and phosphorus from low alloy steel to maraging steel. An attempt was made in this study to improve the properties by friction welding of maraging steel and low alloy steel with nickel as an interlayer. The hardness, tensile strength and impact toughness are observed to be improved, as nickel acted as diffusion barrier. The effect of post-weld heat treatments on microstructure and mechanical properties of dissimilar metal friction welds with and without interlayer was also studied. Maraging steel responded to solutionizing & aging and low alloy steel responded to quenching and tempering. The notch tensile strength and impact toughness in case of dissimilar metal weld with interlayer are observed to be more than that of the dissimilar metal weld without interlayer.     

Joint performance of CO2 laser beam welding 5083,H321 aluminum alloy

Laser beam welding of aluminum alloys is expected to offer good mechanical properties of welded joints. In this experimental work reported, CO2 laser beam autogenoas welding and wire feed welding are conducted on 4 mm thick 5083- H321 aluminum alloy sheets at different welding variables. The mechanical properties and microstructure characteristics of the welds are evaluated through tensile tests, micro-hardness tests, optical microscopy and scanning electron microscopy （SEM）. Experimental results indicate that both the tensile strength and hardness of laser beam welds are affected by the constitution of filler material, except the yield strength. The soften region of laser beam welds is not in the heat-affected zone （ HAZ ）. The tensile fracture of laser beam welded specimens takes place in the weld zone and close to the weld boundary because of different filler materials. Some pores are found on the fracture face, including hydrogen porosities and blow holes, but these pores have no influence on the tensile strength of laser beam welds. Tensile strength values of laser beam welds with filler wire are up to 345.57 MPa, 93% of base material values, and yield strengths of laser beam welds are equivalent to those of base metal （264. 50 MPa）.     

Mechanical Characterization of Copper-Copper Wires Joined by Friction Welding Using Instrumented Indentation Technique

Friction welding samples of both the fire-refined high-conductivity (FRHC) and electrolytically tough pitch (ETP) copper alloy wires have been mechanically characterized by instrumented indentation technique and tensile test. Hardness profiles in the perpendicular direction to the weld interface, in both the central and peripheral zones, of the as-welded FRHC-FRHC and ETP-ETP samples have been investigated at nano-/micrometric scale. The microstructures of welds have been observed using both the optical microscopy and scanning electronic microscopy. The results show the typical friction welding zones: the interface zone, the thermo-mechanically affected zone (TMAZ), and the transition zone between the TMAZ and the base metal zone (BMZ) that present a microstructure and hardness close to the base metal. No presence of a heat-affected zone is observed. Although both welds show the same tendency in hardness distribution, FHRC-FHRC weld presents a TMAZ narrower than ETP-ETP one, which produces a stronger drop in hardness with increasing of the distance from welding central line, and a higher difference in hardness between the central and peripheral zones. The tensile tests of ETP-ETP welds showed that all samples broke by the BMZ that is far away from the interface of the welded joint, while the most of the FRHC-FRHC welds are broken at the TMAZ region at low strengths. These appreciable differences in mechanical properties for the FHRC-FHRC welds are probably generated by a stronger variation in their microstructural properties. Therefore, it may justify the welding failures in the FHRC-FHRC weld at the typical tensile stress for an industrial cold-drawn process of wires.     

低活化马氏体钢真空扩散焊接头力学性能

在不同焊接工艺参数下对低活化马氏体钢进行真空扩散焊接试验,分别对焊缝区进行光学显微观察(OM)与扫描电镜观察(SEM)分析,并对焊件进行力学性能测试. 结果表明,低活化马氏体钢的焊后组织主要为板条马氏体及少量的残余奥氏体,焊缝结合状况良好;在一定范围内提高焊接温度、延长保温时间可以提升接头抗拉强度,但过高的温度及保温时间会导致奥氏体晶粒粗化,损害接头的抗拉强度及冲击韧性. 经过焊后热处理(正火+回火)的接头抗拉强度相对于热处理前有所降低,但组织稳定性及冲击韧性有一定改善.     

Microstructure and mechanical properties of Al-6061-T6 alloy welded by a new hybrid FSW/SSW joining process

In this study for the first time, the effects of decrease in heat inflow to the weld metal in friction stir process by utilising semisolid processing and decreasing the pin rotational speed as well as increasing the pin transverse speed were examined. As a result, the characteristic loss of hardness and strength in the weld zone were eliminated. The results showed that by approaching the ultrafine microstructure in the weld zone through the hybrid FSW/SSW process, the hardness and elongation values reached to 90?Hv and 8.88%, respectively. These are only slightly different from those of the base metal of the welded samples. Furthermore, the ultimate tensile strength of the samples welded by the hybrid technique was found to be about 167?MPa that was higher than those of the samples welded by friction stir welding (151?MPa) and semisolid welding (114?MPa) techniques.     

5A02铝合金C O2激光焊接头组织和力学性能分析

对2mm厚的5A02铝合金进行C02激光焊接试验研究.分析激光焊缝成形和接头微观组织形态,测定了接头上表面和焊缝厚度方向上的维氏硬度,并对接头进行横向和纵向拉伸试验,用扫描电镜观察分析拉伸断口形貌.结果表明,激光功率和焊接速度合理匹配能够获得成形良好、无缺陷的焊缝,焊缝中部为等轴细晶,熔合线附近是柱状晶组织.焊缝各区域...     

Welding behaviour,microstructure and mechanical properties of dissimilar resistance spot welds between galvannealed HSLA350 and DP600 steels

Abstract

Resistance spot welding experiments were conducted on dissimilar material combination of HSLA350/DP600 steels. The welds were characterised using optical and scanning electron microscopy. The fusion zone of the dissimilar material spot weld was predominantly martensitic with some bainite. Mechanical properties were also determined by tensile shear, cross tension and fatigue tests. The performance of dissimilar material spot weld was different from that of the similar ones in each of the HSLA350 and DP600 steels and exhibited different heat affected zone hardness. The DP600 weld properties played a dominating role in the microstructure and tensile properties of the dissimilar material spot welds. However, the fatigue performance of the dissimilar welds was similar to that of the HSLA350 welds. Fatigue tests on the dissimilar material spot welds showed that the 5·5 mm diameter nugget exhibited higher fatigue strength than the 7·5 mm diameter nugget.     

35CrMo调质钢超窄间隙MAG焊接头组织分析

介绍在低温预热条件下35CrMo调质钢厚板的超窄间隙MAG环缝对接焊的设备与工艺。通过焊接接头的金相观察、硬度测量和拉伸试验,分析其组织分布和力学性能。发现焊缝区和热影响区内的微观组织均为细晶形态,硬度值较高。焊接接头的拉伸实验结果表明,断裂均发生在硬度值较低的焊缝区,但对应强度大大高于该焊丝的抗拉强度。应用超窄间隙MAG焊较低热输入焊接工艺,有利于形成细晶粒的焊缝和热影响区组织,能够通过细晶强化大幅度提高熔敷金属的抗拉强度,这对低合金调质高强钢的工艺设计与应用具有重要的参考价值。     

Mechanical evaluation and thermal modelling of friction welding of mild steel and aluminium

In friction welding of two dissimilar materials, two rods are welded together by holding one of them still while rotating the other under the influence of an axial load which creates frictional heat in the interface. In this study, mechanical properties of mild steel and aluminium welded rods were evaluated to understand the thermal effects, and an explicit one-dimensional finite difference method was used to approximate the heating and cooling temperature distribution of the joint. The thermal effects of the friction welding were observed to have lowered the welded materials hardness compared to the parent materials. The tensile strength of the welded rods is lower than the parent rods due to incomplete welding. The preliminary predictions were compared to actual thermocouple data from welds conducted under identical conditions and were shown to be in fair agreement. The finite difference method proposed in this work will provide guidance in weld parameter development and will allow better understanding of the friction welding process.