双孔微剪切评定焊接接头的局部强度

提出一种评价力学性能不均匀焊接接头强度的方法,研制了测量材料局部力学性能的双孔微剪切试验装置,对焊接接头各区域进行微剪切试验.记录加载过程中载荷传感器和位移传感器传输的数据,转化得到剪切应力-应变曲线.建立双孔微剪切试验的有限元模型,选择不同屈服应力和加工硬化指数的材料进行有限元模拟,建立试验剪切应力,应变曲线与材料强度参数的相关性,并利用拉伸试验对其准确性进行了验证.结果表明,利用双孔微剪切试验曲线可直接得到材料的强度参数,并利用双孔微剪切试验测定X70管线钢焊接接头上各区的强度.     

轿车用铝合金焊接接头局部力学性能分析

铝合金焊接接头是一个组织和力学性能不均匀体,准确测定不同区域的局部力学性能,对评定接头整体性能和改善焊接工艺是十分必要的.通过对轿车用5052铝合金焊接接头显微组织及硬度分析,提出了微冲压试验方法,结合ABAQUS有限元商业软件对接头局部力学性能进行了研究.在有限元反向模拟计算间接得出局部材料的本构关系,同时利用拉伸试验验证该方法的准确性.结果表明,焊接接头局部力学性能分布特征与硬度值分布特征基本相似,熔合线附近是焊接接头力学性能最薄弱的区域.     

屈强比对DP540双相钢闪光对焊接头变形行为的影响

对屈服强度不同、厚度为6 mm的DP540双相钢板进行了闪光对焊。检测了焊接接头的显微组织和拉伸性能。结果显示：屈服强度为338 MPa的焊接接头屈强比为0.62,拉伸试样断裂在粗晶区;屈服强度约为450 MPa的焊接接头的屈强比为0.8～0.9,拉伸试样断裂于母材;屈强比较低的接头母材组织粗大且马氏体呈大块状,粗晶区部分铁素体晶粒尺寸达50μm以上;焊接接头在拉伸试验过程中首先在粗晶区产生塑性变形,其不同区域的变形不均匀;屈强比较大的焊接接头母材铁素体晶粒尺寸约为10μm,粗晶区铁素体晶粒尺寸约为20μm;特征区组织细小且马氏体呈岛状弥散分布的焊接接头在拉伸试验过程中能均匀变形。     

微冲压法评定铝合金焊接接头局部力学性能

铝合金焊接接头存在力学性能不均匀性,准确测定不同区域的局部力学性能,对评定整体接头性能和改善焊接工艺是十分必要的.文章提出了微冲压试验方法,并通过有限元反向模拟计算可以间接得出材料局部的本构关系.同时利用拉伸试验验证该方法的准确性.另外对5052铝合金焊接接头局部力学性能进行了测试,其分布特征与硬度值分布基本相似.该研究为焊接接头局部本构关系的表征提供了理论依据和新的试验方法.     

12Cr密封面SAW和GMAW堆焊工艺研究

针对SAW和GMAW在阀体材料上堆焊12Cr密封面进行了焊接工艺评定试验。利用光学显微镜分析了焊接接头热影响区(粗晶区)金属的显微组织;并进行了拉伸、弯曲、冲击试验和焊缝及热影响区的显微硬度测试。结果表明,2.25Cr-1Mo阀体材料具有较强的冷裂倾向,焊前需250℃以上的温度预热;GMAW焊试样得到的焊接接头性能略优于SAW焊试样,两种工艺方法得到的接头性能均满足密封面要求。     

316L不锈钢厚壁管全位置TIG焊接头组织及性能

采用法国POLYSOUDE管-管全位置自动脉冲TIG焊机焊接壁厚20 mm的316L不锈钢管,焊后对接头的组织性能进行了测试和分析。试验结果表明:在焊接过程中,通过焊机中参数数据库对焊枪处于不同焊接位置时焊接工艺参数的控制和调整,可以获得成形均匀一致、质量稳定的焊接接头;拉伸试验结果表明:接头的抗拉强度在600 MPa左右,拉伸试样全部断裂在母材;在接头4个不同位置中,焊缝的硬度最高,其最大值可以达到HV207。采用管接头全位置自动TIG焊可以得到焊缝成形及组织性能均匀一致的不锈钢管接头。     

2219-T87铝合金的中心表面裂纹拉伸试样的断裂强度(英文)

将2219-T87铝合金板材进行低温拉伸试验,用改进的固有缺陷模型分析铝合金基材和焊接接头金属表面裂纹试样的断裂强度数据,通过构成的失效评估图来确定材料的断裂参数。通过考虑材料的极限拉伸强度、铝基材及焊接接头金属的断裂强度数据,对具有不同厚度的中心表面裂纹拉伸试样进行断裂分析。由拉伸断裂板材所得到的失效评估图能够应用到由相同材料构成的任何开裂组件的失效压力估计。     

应力集中对焊接接头拉伸试验的影响

应用NX Nastran有限元分析软件,对焊接接头拉伸试样进行应力集中分析,总结了试样过渡半径对应力集中的影响规律.结合塑性材料和脆性材料不同的断裂机理得出结论,应力集中对塑性材料焊接接头拉伸试验影响不大,对脆性材料影响显著,使试验结果偏低,是造成试样脆性断裂的主要原因.     

S355钢T形接头高周疲劳性能

在工程领域中焊接构件极易产生疲劳断裂,引起各行业广泛关注。文中以T形接头为研究对象,采用MIG焊对S355钢板进行T形接头焊接试验,并对焊接接头进行金相组织和硬度分析。结果表明,焊缝主要为先共析铁素体、珠光体、粒状贝氏体和少量针状铁素体;熔合区成分和组织不均匀,晶粒大小不一致;过热区晶粒较粗大且不均匀;正火区组织主要为铁素体和珠光体,晶粒细小均匀。焊接接头的硬度高于母材,最高硬度出现在热影响区。对T形接头焊接试样进行轴向高周疲劳试验,通过最小二乘法拟合试验数据,得到疲劳S-N曲线。     

T2紫铜-45钢电子束焊双材料界面性能与裂纹偏转

焊接接头性能与缺陷一直是焊接材料相关课题的重要方面,大量的研究描述了焊接材料的接头性能与特征,但异种焊接材料的界面与开裂问题研究并不充分. 文中对T2紫铜-C45钢电子束焊接双材料界面强度和裂纹开裂的问题,首先采用标准拉伸和三点弯曲试验,得到该材料焊缝区抗拉强度、屈服强度、弹性模量参数,并依此计算判断出断裂韧性值;其次对拉伸和三点弯曲试验试样的宏观和微观断口分析,表征其断口形貌特征,得出断口断裂类型为准解理和沿晶脆性复合断裂模式;基于试验分析结果对裂纹开裂偏转路径进行讨论,得出裂纹沿焊缝区扩展并偏向T2紫铜端;最后以实测参数为基准,基于ABAQUS有限元分析得出三点弯曲试验下焊缝区的裂纹扩展和偏转方向结果,为该种异种金属焊接材料接头性能的提升提供了依据.     

铝合金FSW拼焊板塑性变形规律研究

铝合金搅拌摩擦焊拼焊板焊缝各区力学性能的差异导致拼焊板成形时严重的不均匀性,降低了拼焊板的成形性能,极大地限制了铝合金拼焊板的应用。以2024铝合金搅拌摩擦焊拼焊板为研究对象,通过实验和有限元模拟系统研究接头力学性能失配对铝合金拼焊板塑性成形性能的影响规律和机理。对铝合金搅拌摩擦焊接头进行金相检验和硬度测试,根据接头组织及硬度分布特征,将搅拌摩擦焊接头划分为焊核区、热机影响区、热影响区以及母材区4个部分,以此建立搅拌摩擦焊接头的有限元模型,并对接头变形过程中的约束与协调变形规律进行分析。接头变形时拉伸应力在屈服应力最小的区域最低,在屈服应力较大的区域相应升高,且在接头中存在失配比交界处都会发生突变。从形变能的角度分析,这主要是由于力学性能失配而导致变形不协调及相互约束,表现在接头拉伸性能上就是屈服强度及屈服位置、抗拉强度、延伸率随接头各区失配比组合的差异。     

Microstructures and Mechanical Properties of 12Cr1MoVG Tube Welded Joints With/Without Post-weld Heat Treatment

Small-caliber, thick-wall 12Cr1MoVG seamless steel tube welded joints were fabricated in this study by gas tungsten arc welding and shielded metal arc welding techniques, then the microstructures, mechanical properties, and residual stress distributions of the joints with or without post-weld heat treatment (PWHT) were compared. The welded joints are mainly composed of bcc ferrite (F), Fe₃C, and M₇C₃ carbides. PWHT did not cause an apparent microstructure evolution in the joints, but promoted granular pearlite decomposition and growth of F grains and carbides, therefore decreasing the yield, tensile strength, and hardness while increasing the impact toughness and elongation of the welded joints. PWHT also released the circumferential residual stress and altered the stress state in the joint from tensile to compressive. Although the mechanical properties and bending performance of the small-caliber, thick-wall 12Cr1MoVG seamless welded joints without PWHT are acceptable, our results show that the joints with PWHT are more reliable.     

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）.     

焊丝成分对6082-T6铝合金焊接接头组织和性能的影响

采用ER5356和ER5087焊丝对12 mm厚6082-T6铝合金进行熔化极惰性气体保护焊(MIG)后,通过显微硬度测试、拉伸力学性能测试、光学显微镜(OM)、扫描电镜(SEM)、电子背散射衍射(EBSD)和透射电镜(TEM)等研究焊丝成分对焊接接头力学性能与显微组织的影响。结果表明:采用ER5087焊丝焊接的6082-T6铝合金焊接接头焊缝区晶粒更细小;抗拉强度、屈服强度、断后伸长率以及焊接系数均高于ER5356焊丝焊接的6082-T6铝合金焊接接头的;两种焊丝焊接的6082-T6铝合金焊接接头的硬度最低区域与拉伸断裂位置均在距离焊缝中心10~15 mm处的热影响区,该区域β″强化相聚集长大、粗化,导致析出相强化作用减弱,成为焊接接头性能最薄弱区域。     

Static tensile strength characteristics of fillet welding lap joints assisted with bonding

A series of tensile tests were carried out on fillet welded lap joints assisted with bonding for investigating the static tensile strength characteristics of the joints from the viewpoints of stress reduction effect around the welded part due to bonding. It was confirmed that the mechanical properties of epoxy resin bonding used in this study were not deteriorated by heating to less than 150°C. When the fillet welded lap joints with bonding were assembled, the bond layer 20 mm from the weld toe was subjected to heating to over 150°C. In other words, the mechanical properties in that region deteriorated. The strengths of the elastic limits of specimens with welding and bonding were higher than those of specimens with only welding by from 60 to 100 MPa. The ultimate tensile strengths of them were almost the same because they were broken at the base plate. The strains around the weld toe and the root of specimens with welding and bonding were smaller than those of specimens with welding by around 13% in the elastic region. The strengths of specimens with only bonding were 170 MPa, which could be explained by a theory of elastic stress distribution. Even if the bond layer 20 mm from weld toe of the specimens with welding and bonding was thermally damaged, the possibility was confirmed that the residual bond layer had around 100 MPa in strength. It could be concluded that the strength of the residual bonding assisted to decrease the stress around the welded part of the specimens with welding and bonding.     

热处理工艺对M390/304 CMT焊接接头微观组织及力学性能的影响

基于改善M390高碳马氏体不锈钢与304奥氏体不锈钢焊接接头的力学性能特别是提高焊接接头硬度,以达到高端刀具生产的要求,对冷金属过渡焊接M390高碳马氏体不锈钢与304奥氏体不锈钢获得的焊接接头进行不同工艺的热处理研究.采用拉伸、维氏显微硬度测试及扫描电镜(SEM)表征不同热处理工艺的焊接接头力学性能及微观组织演变,统计了不同热处理工艺下焊接接头中M390母材、M390细晶区和M390粗晶区等区域的碳化物分布,研究了不同热处理工艺下焊接接头的断裂机理.研究结果表明,在1 150℃水淬热处理工艺下焊接接头既满足刀具钢硬度的要求,又具有良好的力学性能,可以作为M390/304焊接接头的最佳热处理工艺,对应焊接接头的抗拉强度和断后伸长率为502 MPa和20.8%,抗拉强度和断后伸长率分别是焊态的98%和95%. 1 150℃水淬热处理工艺的M390母材、细晶区和粗晶区中碳化物平均尺寸最小,碳化物形貌以细小的块状均匀分布.淬火温度升高,抗拉强度和断后伸长率均呈现出先下降后升高的趋势,随着冷却速度的减小,抗拉强度和断后伸长率均呈现出下降的趋势.不同热处理工艺下焊接接头的断裂位置在M390粗晶区...     

Microstructure and mechanical properties of laser welded dissimilar DP600/DP980 dual-phase steel joints

The use of dual phase (DP) steels in the automobile industry unavoidably involves welding and dynamic loading. The aim of this investigation was to evaluate the microstructural change and mechanical properties of laser welded dissimilar DP600/DP980 steel joints. The dissimilar joints showed a significant microstructural change from nearly full martensite in the fusion zone (FZ) to the unchanged ferrite-martensite dual-phase microstructure in the base metal. The welding resulted in a significant hardness increase in the FZ but the formation of a soft zone in the heat-affected zone (HAZ). The dissimilar welded joints were observed to exhibit a distinctive unsymmetrical hardness profile, yield-point-like phenomenon, and single-stage work hardening characteristic, with yield strength and work hardening rate lying in-between those of DP600 and DP980 base metals, and ultimate tensile strength equivalent to that of DP600 base metal. Although the welded joints showed a lower fatigue limit than the base metals, the fatigue life of the welded joints at higher stress amplitudes was almost the same as that of the DP600 base metal. The welded joints failed in the soft zone at the DP600 side under tensile loading and fatigue loading at the higher stress amplitudes. Fatigue crack initiation occurred from the specimen surface and crack propagation was characterized by typical fatigue striation together with secondary cracks.     

22MnB5超高强钢焊接组织与性能

采用钨极氩弧焊方法,实现了22MnB5超高强钢淬火前后同种材料之间的连接,进行了焊接接头拉伸试验和热影响区内显微组织及硬度分布试验,并对焊接前后材料的抗腐蚀性能进行了试验分析.结果表明,淬火处理后22MnB5组织结构从铁素体+珠光体组织转变为马氏体组织,显微硬度与抗拉强度大幅度提高,原始及淬火后材料的焊接接头具有良好的力学性能和组织形貌,焊后焊接接头抗拉强度和硬度略低于原始母材,经淬火处理后的材料焊后抗拉强度达到1179.59 MPa,略低于淬火材料但比原始母材高很多,淬火热处理材料的腐蚀速率略有上升,而焊接后将大幅度增加腐蚀速率,通过比较淬火焊缝钢腐蚀速率最大.     

Prediction of microstructure and mechanical properties of line pipe welded joints based on hardness map

In this article, the variation of hardness in cross-section of X52 microalloyed steel joints before and after post-weld heat treatment and also the relationship of hardness with ultimate tensile strength, yield strength and microstructure have been investigated. For this purpose, the specimens were prepared in two conditions of as welded and post-weld heat treated, and the hardness maps of their cross-section were provided. Then, some equations were suggested to correlate the obtained hardness with the grain size and tensile and yield strengths. The equations made it possible to predict tensile and yield strengths with high accuracy. According to the results, the maximum hardness and strength belong to the weld junction. Normalisation of the joints at 950°C reduced significantly the hardness difference (and also the strength difference) in various joint areas and homogenised the microstructure considerably. The grain size distribution was also modelled acceptably for the post-weld heat treated joint, and the grain size map was obtained.