AA5052薄板磁脉冲胶焊复合接头动态力学性能研究

目的 研究AA5052铝合金薄板在高速冲击载荷下的磁脉冲胶焊复合接头的动态力学性能,探究不同载荷速率对该胶焊复合接头力学和失效行为的影响规律.方法 利用磁脉冲焊接系统成功制备了胶焊复合连接试件.采用万能拉伸试验机、高速拉伸试验系统,结合全场应变测量系统,获得胶焊复合接头的力学性能规律,以及渐进失效过程和搭接区应变变化.通过扫描电镜观察焊缝断口,对其显微形貌进行表征.结果 当剪切速率从2 mm/min提升到10 m/s时,接头的峰值载荷从6086.5 N增大到6592.5 N,吸收的能量从41.1 J增大到96.4 J.相比于2 mm/min准静态剪切断口,1 m/s高速剪切断口中等轴韧窝和胶粘剂薄层的比例均提高.当剪切速率在1 m/s以下时,接头发生胶层和焊缝断裂失效;当剪切速率在1 m/s以上时,胶层和焊缝得到的强化程度高于母材,胶层开裂程度减小,接头搭接区的刚度提高,所以拉伸端母材发生严重的颈缩直至断裂失效.结论 随着剪切速率的增加,接头的峰值载荷和吸收能量均增大,胶层的开裂程度减小,失效形式由焊缝和胶层断裂转变为母材断裂.     

铝-铜外导槽式磁脉冲焊接接头组织与性能

目的 对铝板和铜板进行外导槽式磁脉冲焊接,研究不同晶粒度的母材对焊接接头界面形貌和力学性能的影响。方法 采用万能拉伸试验机、扫描电镜、EDS能谱以及显微硬度计等分析方法,观察焊接接头界面形貌,测试焊接接头的力学性能。结果 在电压9 kV,间隙2 mm的条件下,获得了铝板和不同退火温度的紫铜板外导槽式磁脉冲焊接接头;铜母材的晶粒度大小会影响铝-铜板焊接接头界面形貌,经450 ℃退火处理的铜板与铝母材形成界面波形最明显且过渡区厚度最大;过渡区是铝铜元素的混合区,宽过渡区界面形成稳定的化合物,如CuAl和CuAl2;焊缝处的显微硬度值总是比两侧母材的硬度值高,远离焊缝的硬度值保持稳定,未热处理的铜板与铝板形成的焊缝硬度最高。结论 铝-铜外导槽式磁脉冲焊接接头强度高于铝母材。     

5052铝合金胶接-磁脉冲焊接复合接头盐雾腐蚀性能研究

目的 研究5052铝合金板胶接-磁脉冲焊接复合接头的抗腐蚀性能和腐蚀路径.方法 以AA5052铝合金板为研究对象,选用胶接-磁脉冲焊接复合工艺进行连接,并在35℃、质量分数为5％的氯化钠溶液中对样件进行中性盐雾腐蚀试验6～18 d,之后对接头的剪切性能进行测试,再结合SEM对接头的腐蚀路径进行分析.结果 在中性盐雾腐蚀试验中,腐蚀时间增加,磁脉冲点焊接头和胶焊复合接头的质量损失率均增大,峰值载荷下降,且腐蚀6～12 d阶段内质量损失率和性能衰退均放缓.经过18 d的盐雾腐蚀后,胶焊复合接头的峰值载荷下降了6.4％,而磁脉冲点焊接头则下降了23.1％.胶层能延缓胶焊复合接头的力学性能衰退,起到一定的防腐蚀作用.结论 在中性盐雾腐蚀试验中,胶焊复合接头中的胶层可吸收盐雾液滴并阻碍其渗透,并延缓接头的力学性能衰退.盐雾液滴的腐蚀路径为:在磁脉冲点焊接头中,大部分盐雾液滴渗透进入变形区的凹槽,而在胶焊复合接头中盐雾液滴会被胶层吸收一部分.随着盐雾腐蚀的进行,盐雾液滴会逐渐穿透胶层,降低胶粘剂和母材之间的嵌合力以及胶粘剂之间的内聚力.此外,少部分盐雾液滴流动至焊缝外侧,逐渐向焊缝内侧浸入,并溶解焊缝周围的金属,造成点蚀区局部连通的现象.     

FV520B不锈钢角焊缝接头的组织和断裂机理

通过对焊接接头疲劳断口的观察研究,讨论了控制接头疲劳失效的疲劳机理。实验研究了焊接接头的母材、焊缝及热影响区的微观组织形态。结果发现:母材组织为细小均匀的板条马氏体及弥散分布的第二相粒子,而焊缝区为粗大的板条马氏体及少量的第二相颗粒。组织特征的区别证明母材综合力学性能优于焊缝。     

某压缩机法兰与钢管焊接接头焊缝开裂失效分析

某平台湿气压缩机法兰与钢管焊接接头焊缝发生开裂失效,采用宏观观察、化学成分分析、金相检验、力学性能试验、扫描电镜分析和能谱分析等方法对焊缝的开裂原因进行了分析。结果表明:焊接接头结构的不合理和焊缝内部的未熔合缺陷造成局部应力集中,并导致焊接接头的疲劳极限下降,在应力作用下法兰一侧切口处焊缝根部与未完全熔合的法兰母材交界处形成裂纹源;在外部循环载荷作用下,裂纹逐渐向外表面扩展,当达到焊接接头的疲劳极限时,焊缝即发生开裂。     

60mm厚度6061-T6铝合金板搅拌摩擦焊接接头微观组织与力学性能

采用搅拌摩擦焊接方法对6061-T6铝合金板进行了60mm双面对接焊实验,研究了搅拌摩擦焊接接头的微观组织与力学性能,结果表明:焊缝区微观组织沿厚度方向发生了不同程度的改变,焊接接头强度达到218MPa,为母材强度的70％;焊接热循环引发的金属强化相“重固溶”和“过时效”是接头力学性能下降的重要原因,其中前进侧热机影响...     

厚板7022铝合金搅拌摩擦焊接实验研究

对10mm厚度的7022铝合金进行了搅拌摩擦焊接,获得表面光滑的焊接接头,并通过X射线检测焊缝无裂纹和气孔。研究该搅拌摩擦焊接头不同区域的显微组织特征,并通过拉伸、冲击和硬度试验分析了焊接接头的力学性能。结果表明,焊缝处组织为细小均匀的等轴晶粒;在搅拌头转速为400r/min,焊接速度为100mm/min时焊接接头的抗拉强度、屈服强度均比母材高;焊接接头的冲击韧性比母材高;焊接接头显微硬度比母材稍低,焊接接头具有良好的力学性能。     

316L不锈钢薄板焊缝成形及力学性能研究

目的 减少1 mm厚度316L不锈钢薄板在焊接生产过程中出现的缺陷等问题,并提高不锈钢薄板焊缝成形质量和焊接接头力学性能。方法 采用脉冲激光焊接技术实现对厚度1 mm的316L不锈钢薄板的精确焊接,并利用金相显微镜、维氏硬度计、万能拉伸试验机和扫描电镜对焊缝的表面形貌、微观结构、力学性能、断口形貌进行表征分析。结果 当激光功率为403 W、输出电流为150 A、焊接速度为150 mm/min、离焦量为−5.525 mm时,焊缝正反面的形貌规则无缺陷。焊缝区内的微观结构主要由δ-铁素体和奥氏体2种晶粒构成,相较于母材及热影响区,焊缝区晶粒尺寸更细小均匀,平均硬度为156HV,表现出更高的硬度特性。焊接接头的抗拉强度和屈服强度均值分别达到643.28 MPa和305.95 MPa,相对于母材的强度分别提高了7%和49%;平均断后伸长率为37.2%,达到原始母材伸长率的55%;断裂呈现韧性断裂的塑性变形和延展性特征。结论 优化调整焊接工艺参数后,1 mm厚度316L不锈钢薄板的焊缝成形质量提高,无缺陷且微观组织分布均匀,焊接接头强度显著提高。     

5383铝合金电子束焊接接头组织与性能研究

通过金相观察、力学性能试验和SEM技术研究了5383铝合金真空电子束焊接接头的金相组织、力学性能和断口形貌特征。结果表明,焊接接头的拉伸强度低于母材;焊缝区组织主要为基体上均匀散布的强化相,熔合区为柱状树枝晶;在焊缝熔合线附近由于一次枝晶的生长方向受凝固过程中温度梯度的影响,微观组织为垂直于熔合线方向的柱状树枝晶;焊接接头的拉伸断口呈韧窝特征,但底部易出现气孔缺陷,单纯采用扫描函数不能完全消除根部气孔缺陷。     

不锈钢激光-MAG复合焊接头微区性能研究

激光复合焊可用于不锈钢焊接,但激光复合焊接头热影响区小,组织变化梯度大.研究接头微区性能可以确定接头薄弱环节,为焊接接头的工艺评定和断裂分析提供理论依据.为此,本文对4 mm厚SUS301L-HT不锈钢进行激光-MAG复合焊接,采用维氏硬度、微型剪切和微拉伸等试验,研究了焊接接头焊缝、热影响区及母材的微区力学性能,并结合金相、断口扫描等分析了各微区力学性能的差异.结果表明：焊缝区域组织主要为柱状奥氏体树枝晶+少量的δ铁素体;母材的剪切强度和抗拉强度最高,分别为560和1 066 MPa,其次为复合焊接头热影响区,焊缝区域最差,接头硬度分布规律与各微区强度变化趋势一致;运用数学方法,得出了接头微拉伸强度与微型剪切强度、硬度之间关系的经验公式.接头各微区剪切断口和拉伸断口SEM分析呈现典型的韧性断裂特征.     

Application of low Ms temperature consumable to dissimilar welded joint

Abstract

The welding of dissimilar joints is very common in systems used in oil exploration and production in deep sea waters. Commonly involves welding of low carbon steel pipes with low alloy steel forgings both with inner Inconel clad. The forged steel part undergoes a process of buttering with Inconel or carbon steel electrode before the weld of the joint. The buttering process is followed by a process of residual stresses relief. The conventional way of reducing the level of residual stresses in welded joints is to apply post welding heat treatments. Depending on the size and complexity of the parts to be joined, this can become a serious problem. An alternative technique for reducing residual stresses is to use an electrode that during the cooling process undergoes a displacive transformation at a relatively low temperature so that the deformation resulting from the transformation compensates the contraction during the cooling process, and, although many papers have been published in this direction using Fe–Cr–Ni alloys, most of them report a loss of toughness in the weld metal. Maraging steel is a family of materials with M_s temperature below 200°C and even without the final heat treatment of aging has superior mechanical properties to low alloy steels used in forgings. In this work, forged piece of AISI 4130 was buttered with Maraging 350 weld consumable and subsequently welded to ASTM A36 steel using Inconel 625 filler metal. In addition, the dissimilar base metal plates were welded together using Maraging 350 steel weld consumable. The levels of residual stress, and the toughness and microstructures of heat affected zone and weld metal were investigated.     

日本潜艇用钢及焊接材料的焊接性能综述

本文综述了日本的潜艇用钢及其焊接材料的各项焊接性能试验情况。对NS63和NS80钢的大量试验结果表明:为了防止产生焊接裂纹,应根据钢种强度级别、板厚和拘束应力的不同来选择不同的预热和道间温度,通常在50~150℃之间变化;相应的焊接热输入也宜在16~24 kJ/cm之内选配,以便得到与焊材相适应的临界冷却速度,使之满足焊缝力学性能的要求。还要限制施焊环境的水蒸气分压(≤25mmHg),焊材的吸潮量要≤0.20%。另外,对NS110钢的低强匹配焊接接头也进行了大量的试验工作,结果表明:在焊缝强度比母材降低15%的条件下仍具有良好的综合性能,将其应用到潜艇壳体上是可以信赖的。     

ZK60镁合金光纤激光焊接工艺参数及接头性能研究

目的 采用光纤激光对ZK镁合金进行焊接,分析焊接工艺参数对焊接接头性能的影响规律。方法 采用正交实验方法,在焊接过程中对焊接主要的工艺参数比如:激光的功率,焊接的速度,离焦量进行三因素三水平正交实验,采用拉力实验机对焊接接头进行抗拉强度测试,得到抗拉强度最大的工艺参数组合。对焊缝微观组织及断口形貌进行分析。结果 当激光功率为1 400 W、焊接速度为40 mm/s、离焦量为3 mm时,焊缝抗拉强度达到最高的308 MPa,达到母材抗拉强度的95%。结论 在合适的工艺条件下,光纤激光焊接过程中,如果热输入较低,焊接速度过快,导致熔池冷却速度非常快,同时细化了晶粒,提高焊缝接头的综合力学性能。     

Mechanical properties of friction welded 6063 aluminum alloy and austenitic stainless steel

Friction welding of dissimilar metal combination of aluminum alloy and austenitic stainless steel was examined to investigate the effect of welding conditions on mechanical properties of the dissimilar metal combination. The welded joints were produced by varying forge pressure (F _g), friction pressure (F _r), and burn-off length (B). The joints were subjected to mechanical testing methods such as the tension, notch Charpy impact tests. The tensile strength and toughness decrease with an increase in friction pressure. The tensile strength decreases with an increase in burn-off length at a low forge pressure while tensile strength increases with an increase in burn-off length at a high forge pressure. The tensile failure of the welded joint occurred in aluminum alloy just away from interface in the thermo-mechanically affected zone indicates good joint strength at the condition of low friction pressure, high forge pressure, and high burn-off length. The maximum tensile strength was observed with low friction pressure and high forge pressure. The tensile strength of dissimilar joint is approximately equal to tensile strength of 6063 aluminum alloys at the condition of low friction pressure, high forge pressure, and high burn-off length. The tensile and impact failure of joints was examined under scanning electron microscope and failure modes were discussed.     

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。     

Elucidation of fatigue characteristics and fracture mechanism of friction stir spot‐welded tension–shear joint steels

The fatigue life and fracture mechanism of friction stir spot welded tension–shear joints using 590‐MPa class steel as a base material under constant‐amplitude conditions were investigated with focus on welding dimension variations caused by tool wear. The fatigue limit of the friction stir spot welding (FSSW) joint used for this study is significantly low compared with the static tensile strength of the joint itself. It was clarified that the FSSW joint in this study exhibited two different failure morphologies regardless of the applied load level: base metal fracture and weld area fracture. Although the welding state changes due to the tool wear phenomenon that produce two types of fracture modes in relation to the welding rip diameter, they have no effect on the fatigue strength, regardless of the applied load.     

Welding failure of as-fabricated component of aluminum alloy 5052

This paper describes the failure analysis of the “tray section” made up of aluminum alloy 5052 which is used as a specimen holder in a research reactor. Fracture was observed in the central rod of alloy 5052 before it was taken for service. The fracture had occurred in a brittle mode without any gross plastic deformation at a location where the rod was welded to the stopper plate. Detailed microstructural examination was done using both optical and scanning electron microscopy. The weld fusion zone showed presence of high porosity and eutectic phases mainly along the inter-dendritic regions. These low melting temperature eutectics were rich in Si and Fe and led to weld cracking along the dendritic grains during solidification of the welds. Solidification cracking of alloy 5052 was related to pure aluminum filler wire used for welding that shifted the composition of the welds towards peak cracking sensitivity of 1.5 wt% Mg. The failure of the tray section was concluded to be due to welding defects, e.g. high porosity and solidification cracks. Recommendations to avoid this type of failure are also proposed.     

Fatigue crack propagation rates and threshold stress intensity factors for welded joints of HT80 steel at several stress ratios

Fatigue crack propagation rates and threshold stress intensity factors were measured for welded joints and base metal by using 200 mm wide centre-cracked specimens. The fatigue crack propagation properties of welded joints were similar in spite of the different zones in which the cracks propagated (ie, in the heat-affected zone and in the weld metal) and the different welding process used (submerged arc welding and gas metal arc welding). They were, however, inferior to those of the base metal. It was revealed by observation of the crack closure that the fatigue cracks were fully open during the whole range of loading, due to the tensile residual stress distribution in the middle part of the welded joints. This observation also explains the lack of a stress ratio effect on the fatigue crack propagation properties of welded joints, and their inferiority to those of the base metal.     

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.