焊管焊接接头拉伸试验相关标准的讨论

焊管常用标准对焊缝接头拉伸试样是否去除焊缝余高要求不一。本文从焊接接头拉伸的实际意义出发,探讨了是否去除焊缝余高及断裂位置对试验结果的影响。不去除焊缝余高的情况,更偏重于焊缝结构的整体强度,而不是严格意义上的焊接接头的抗拉强度。为避免分歧及便于对比,西气东输二线管道工程技术条件中统一规定了焊接接头拉伸试验必须去除焊缝余高,且报告断裂位置。     

X65管线钢焊接接头在模拟浅表海水环境中的应力腐蚀试验研究

在海水环境中,由于海水从海底管道外管焊缝浸入,导致外管焊接接头断裂。为了研究可能导致X65外管焊接接头断裂的因素,应用慢应变速率拉伸试验(SSRT),通过应力-应变曲线、扫描电镜(SEM)等手段分析了3个X65管线钢焊接接头在空气及模拟浅表海水环境中的应力腐蚀性能。结果表明:在空气中X65钢焊接接头试样的延长量最大,达5.6 mm,在模拟海水中试样的延长量均减小,其中2号试样延长量最小,仅3.6 mm,表明试样在浅表海水中塑性变形能力降低;模拟海水中3个试样的应力腐蚀敏感性指数均处于有应力腐蚀倾向的范围;在空气中试样的断裂为韧性断裂;在浅表海水环境中试样的断裂为韧性断裂与脆性断裂的混合断裂,有应力腐蚀开裂的趋势;海水中含有的大量Cl~-导致焊接接头的应力腐蚀敏感性升高,失效风险增加。     

Microstructure Evolution and Tensile Properties of Ti3Al/Ni-based Superalloy Welded Joint

In the present work,the dissimilar joining of a Ti_3AI-based alloy to a Ni-based superalloy was attempted by gas tungsten arc(GTA) welding technology.Sound joints were successfully achieved by using a Cu—Ni alloy as filler material.According to X-ray energy dispersive spectroscopy and X-ray diffraction analysis results three transitional layers at the weld/Ti_3AI interface were verified as follows:Ti_2AINb phase dissolved with Cu and Ni;AI(Cu,Ni)_2Ti,(Cu,Ni)_2Ti and(Nb,Ti) solid solution;Cu-rich phase and a complex multi-element phase.The In718/weld interface is characterized by solid solutions of Ni,Cu,Cr,Fe and Nb.The average tensile strength of the as-welded joints at room temperature is 1 63 MPa,and after a post—weld heat treatment it is increased slightly to 177 MPa.The fracture occurred at the surfacial layer of the joined Ti_3AI base alloy,indicating that the Ti_2AINb layer dissolved with Cu and Ni is the weak link of the Ti_3AI/ln71 8 joint.     

Microfractography of the Surfaces of Welded Joints of Austenitic and Ferritic Steels Obtained in Tensile Tests

Materials Science - We present the results of microfractographic investigations of static tensile tests for welded joints of the 1.4539 austenitic and 1.4742 ferritic steels used for the production...     

Full Field Tensile Strain Shearography of Welded Specimens

Digital shearography is a coherent optical method used in conjunction with digital image processing. It allows the shearogram, which depicts directly displacement derivatives, in real time to be observed and to be evaluated numerically. Strains are functions of the displacement derivatives. Thus, the shearogram contains the strain information, but usually it includes both the in‐plane strain, e.g. ?u/?x, and the out‐of‐plane component, e.g. ?w/?x. In order to get the pure in‐plane strain as well as the pure out‐of‐plane component, two linearly independent directions of illumination (usually the same but mutual and sequential illuminations) are introduced in the measuring device. The shearograms for each illuminating direction are evaluated by applying the phase shifting technique. The result by subtracting the phase maps of the two shearograms yields a new fringe pattern depicting the pure in‐plane strain component and the result by adding the phase maps corresponds to the pure out‐of‐plane component. The theory and an application to non‐destructive tensile testing are demonstrated in this paper. Its applications for determining the strain distribution of the homogeneous and inhomogeneous material and an error analysis are presented.     

锅筒斜拉杆焊接接头失效原因分析

通过现场勘查及资料查阅,利用宏观检查、无损检测、金相检验、力学性能试验、化学成分分析、扫描电镜分析、电子能谱分析对锅炉缺陷试样的外观、裂纹状况、金相组织、强度、硬度、冲击韧性、塑性、化学元素含量、高倍显微形貌、裂口晶粒能谱等状况进行了分析。结果表明,这是一起罕见的低碳钢由于非金属硅元素含量超标,形成非金属夹杂物,导致焊接时在热影响区发生纵向热裂纹的质量事故。     

ECrNiMo-3焊接X60钢接头组织形貌

利用扫描电镜(SEM)、透射电镜(TEM)观察镍基合金焊缝/X60钢焊接接头微观组织,能谱分析(EDS)测试Cr,Ni,Mo,Fe合金元素在各区域分布,并通过计算获得Mn,C在部分熔化区含量.结果表明:完全混合区为树枝状奥氏体组织,Mo偏析到枝晶间隙.不完全混合区是平面晶形貌,未出现偏析现象,宽度约30μm,在该区内从熔合线到完全混合区,Cr,Ni,Mo含量逐渐增加,X60钢母材Fe含量逐渐降低.部分熔化区是由马氏体基体上镶嵌着大量的第二相粒子构成,仅200nm宽.     

5083铝合金搅拌摩擦焊接头拉伸行为研究

目的 研究5083铝合金搅拌摩擦焊接（FSW）的组织、力学性能和拉伸应变,分析接头的拉伸行为。方法 采用数码相机、光学显微镜、电子扫描显微镜等表征分析方法,对焊缝的表面宏观成形、微观组织、断口形貌进行分析;利用拉伸机、三维数字动态散斑应变测量分析系统和显微维氏硬度计对接头的力学性能和拉伸应变进行测试。结果 不同焊接工艺参数下FSW接头的最低抗拉强度为305 MPa,断后延伸率达到了14%以上;焊核区拉伸应变沿板厚方向呈现上高下低和上宽下窄的不均匀梯度分布,发生了较大程度的变形强化,直到拉伸应力达到抗拉强度。断裂失效前300/120接头的最大拉伸应变在晶粒粗大的母材区,500/120和500/200接头的最大拉伸应变则位于晶粒尺寸差异较大的后退侧焊核区与热力影响区交界处。接头拉伸断口宏观上均为45°剪切韧性断裂,微观上均以韧窝韧性断裂为主,而高热输入500/120接头出现脆性断裂特征,其延伸率明显降低。结论 高热力耦合输入使铝合金FSW接头薄弱区发生转变,强韧性降低。     

FH40+317L复合钢板焊接接头性能分析

对FH40+317L复合钢板的焊接工艺性能进行了试验,分析了焊接接头各区域的金相组织及冲击断口形貌特征。结果表明,FH40+317L复合钢板焊接接头强度及塑性与母材匹配,复层侧不同位置处冲击结果基本相当,-60℃冲击试样断口均为韧性断裂形貌,过渡层未出现马氏体组织。     

2205双相不锈钢GTAW焊接接头组织演化

研究了ER2205不锈钢在固定焊接参数条件下的自动TIG焊接接头的两相组织演化规律。结果表明:受到原始焊道热作用的TIG焊缝具有约50%～60%的铁素体相比例,对应热影响区中的铁素体含量高达70%;随着焊接过程的进行,受到后续焊道热作用影响的焊缝和热影响区的铁素体含量持续降低;在后续焊道焊接过程中焊缝组织不断析出奥氏体相,铁素体相比例不断降低;热影响区中的铁素体含量受到自身焊道和后续一个焊道的影响比较明显;焊缝中部焊道的铁素体相比例低于打底焊道和盖面层焊道。     

焊接接头焊后处理工艺研究现状

概述了焊接接头的后处理工艺,分析了焊后热处理、化学处理及机械处理的原理及处理效果,并重点阐述了机械处理的各种强化技术。焊后热处理可以调整残余应力场、改善焊后组织;化学处理可达到增强工件耐蚀性、硬度、耐磨性等特性的目的;焊后机械处理可以引入有益的残余压应力、细化晶粒、提高表面硬度,从而显著延长焊接接头疲劳寿命、增强耐磨性、提升耐蚀性。