Influence of welding consumables on tensile and impact properties of multi-pass SMAW Armox 500T steel joints vis-a-vis base metal

In this investigation, comparative study of tensile and impact properties of multi-pass SMAW Armox500 T steel joints fabricated by austenitic stainless steel(ASS) and low hydrogen ferritic steel(LHF)consumables vis-a-vis base metal was carried out. The tensile tests were conducted on computer controlled Walter t Bai Ag UTM at a nominal strain rate of 10à3 sà1. Subsequently, charpy impact tests were carried out on an instrumented Zwick-Roell test setup to obtain load vs. displacement and maximum energy absorbed vs. displacement of the specimen. It was observed that, the joint efficiency of weldment processed by LHF consumable was 41.7% and weldment processed by ASS was 30.6% of its base metal indicating the influence of electrode consumable on tensile properties of the joints. On the contrary, impact toughness of weldment processed by ASS was 20% more and weldment processed by LHF was 12% less than that of base metal. Microstructural studies also revealed that, ASS can be considered as a candidate welding consumable for good strain hardening and toughness of the welding joint in impact applications. However, LHF steel consumable is recommended for welding joints that requires higher joint efficiency under tensile loading conditions.

Numerical simulation of 80 ℃ temperature field distribution of thick plate multi-pass welding with SYSWELD

The PPG PITT-CHAR XP flame retardant system has been used by COOEC to preventing the thermal softening of steel in the high temperature,whose degradation temperature is 80 ℃.To prevent damage to PPG PITT-CHAR XP fire retardant paint from excessive heat during welding,it is necessary to get accurately reserved area near the welding joints prior to welding. For the foregoing reasons,the 80 ℃ temperature field distribution of thick plate multi-pass welding was analyzed with SYSWELD.The influence of welding groove form and time interval on welding temperature field was also analyzed. Results showed that the range of 80 ℃ welding temperature field increased with the increasing of weld layers at first and then it inclined to stable value. Interpass time setting was crucial to control the range of 80 ℃ welding temperature field. It was also found that double V groove had better thermal diffusivity than double-bevel groove.And double-bevel groove was better than single V groove.

Numerical Simulation Analysis of Welded Joints in Arch Ribs of Large Span Steel Pipe Arch Bridges

In order to study the residual stress distribution law of welded joints of arch ribs of large-span steel pipe concrete arch bridges,numerical simulation of temperature,stress and strain fields based on ABAQUS for welded joints of arch-ribbed steel tubes using 7-,8-and 9-layer welds is carried out and its accuracy is demonstrated.The steel pipe welding temperature changes,residual stress distribution,different processes residual stress changes in the law,the prediction of post-weld residual stress distribution and deformation are studied in this paper.The results show that the temperature field values and test results are more consistent with the accuracy of numerical simulation of welding,the welding process is mainly in the form of heat transfer;Residual high stresses are predominantly distributed in the Fusion zone(FZ)and Heat-affected zone(HAZ),with residual stress levels tending to decrease from the center of the weld along the axial path,the maximum stress appears in the FZ and HAZ junction;The number of welding layers has an effect on the residual stress distribution,the number of welding layers increases,the residual stress tends to decrease,while the FZ and HAZ high stress area range shrinks;Increasing the number of plies will increase the amount of residual distortion.

Numerical simulation of residual stress and deformation for submerged arc welding of Q690D high strength low alloy steel thick plate

The finite element simulation software SYSWELD is used to numerically simulate the temperature field,residual stress field,and welding deformation of Q690D thick plate multi-layer and multi-pass welding under different welding heat input and groove angles.The simulation results show that as the welding heat input increases,the peak temperature during the welding process is higher,and the residual stress increases,they are all between 330–340 MPa,and the residual stress is concentrated in the area near the weld.The hole-drilling method is used to measure the actual welding residual stress,and the measured data is in good agreement with the simulated value.The type of post-welding deformation is angular deformation,and as the welding heat input increases,the maximum deformation also increases.It shows smaller residual stress and deformation when the groove angle is 40°under the same heat input.In engineering applications,under the premise of guaranteeing welding quality,smaller heat input and 40°groove angle should be used.

Inverse kinematics and welding experiments of the intersecting pipe welding robot

A robot used for multi-pass welding of the piping branch junctions and nozzle attachments to main pressure vessels is 4-DOF serial mechanism, two mobile joints and two rotary joints are adopted in design. The kinematic model was established with DH parameters, the inverse kinematics was solved. According to the forward and inverse kinematics equations, the robot kinematics was simulated in Matlab, the simulations indicate that the solution for inverse kinematics can satisfy the welding requirements well. As there are size errors, processing errors and welding deformation, the path of welding is forecasted according to the previous welding situation, and then, the path is taught at desired via-points, which plays an important role in submerged-arc welding. The submerged-arc welding experiments indicate that the robot and the welding methods are preferable to ensure welding quality.

Prediction of Welding Residual Stress in 2.25Cr-1Mo Steel Pipe

A numerical analysis method was proposed to predict the welding residual stress in 2.25Cr-1Mo steel pipe considering solid-state phase transformations. A thermal elastic plastic finite element (FE) model considering effects of martensite transformation was developed based on commercial ABAQUS software. Continuous cooling transformation (CCT) diagrams were employed to simulate the fraction of martensite in fusion zone, coarse-grained heat affected zone and fine-grained heat affected zone. The Koistinen-Marburger relationship was used to trace the formation of martensite. The effects of both volume change and yield strength change due to phase transformation on welding residual stress were considered using the proposed FE model. The result shows that the phase transformation has significant effects on the welding residual stress in multi-pass butt weld of pipe. The predicted simulation results by the proposed numerical method are generally in good agreement with experimental results.

Transient out-of-plane distortion of multi-pass fillet welded tube to pipe T-joints

The out-of-plane distortion induced in a multi-pass circumferential fillet welding of tube to pipe under different weld sequences and directions was studied using Finite Element Method(FEM) based Sysweld software and verified experimentally. The FEM analyses consisted of thermal and mechanical analyses.Thermal analysis was validated with experimental transient temperature measurements. In the mechanical analysis, three different weld sequences and directions were considered to understand the mechanism of out-of-plane distortion in the tube to pipe T-joints. It was learnt that the welding direction plays a major role in minimizing the out-of-plane distortion. Further, during circumferential fillet welding of the tube to pipe component, the out-of-plane distortion generated in the x direction was primarily influenced by heat input due to the start and stop points, whereas the distortion in the z direction was influenced by time lag and welding direction. The FEM predicted distortion was compared with experimental measurements and the mechanism of out-of-plane distortion was confirmed.

Effect of copper on mechanical properties of high strength SMAW weld metal

Mechanical properties of SMA W （shielded metal arc welding） weld metal （ yield strength higher than 900 MPa ） with systemazic additions of copper （ up to 1.48 wt% ） were tested, The microstructure and precipitates in different regions were analyzed by optical microscope and transmission electron microscope, The results indicate that copper improves the low temperature toughness of weld metal when the copper content is low and reaches the peak value 48 J （ at - 50℃ ） with 0. 2 wt% copper additions. When the content is high the copper precipitates as 8-Cu phase in the reheat zone of middle beads. These precipitates improve the strength of the weld metal evidently （ yield strength up to 975 MPa） without obvious effect on the low temperature toughness. The copper within 1.1 wt% content can improve the strength without toughness loss.

Ti、Mn对Q690钢SMAW熔敷金属组织和力学性能的影响

以开发与Q690高强钢匹配的焊接材料为目的,通过扫描电镜、能谱分析等手段研究了Ti和Mn含量对焊条电弧焊(SMAW,shielded metal arc welding)熔敷金属组织和力学性能的影响。结果表明,Ti和Mn可以有效地改善熔敷金属的微观组织和力学性能。适量添加Ti、Mn会促使熔敷金属中针状铁素体的形成。随着Mn含量的增加,熔敷金属的微观组织由粒状贝氏体+针状铁素体转变为板条贝氏体+马氏体,导致其抗拉强度升高,冲击性能下降。

高速列车转向架SMA 490BW耐候钢焊接热影响区模拟试验

实验分析高速列车转向架构架用钢焊接接头热影响区的组织性能。采用Gleeble-3500热模拟试验机对SMA490BW耐候结构钢进行焊接时温度循环的模拟,研究了三种焊接线能量状态下两个不同特征热影响区的组织和性能,为焊接工艺的优化提供理论依据。SMA490BW耐候钢的过热温度区间热影响区组织多为贝氏体,并且组织性能根据采用线能量的不同会产生明显差异。随着焊接热输入的增加,其组织晶粒增大,强韧性下降。推荐热输入线能量E=5 kJ/cm。

Thickness-Dependent Microstructure and its Effect on Anisotropic Mechanical Properties of Duplex Stainless Steel 2205 Multi-pass Welded Joints

In this study,the thickness-dependent microstructural characteristics of duplex stainless steel 2205 multi-pass welded joints were first investigated by the combination of optical microscope and electron back-scattered diffraction observation.Subsequently,a series of tensile tests of miniature samples cut from different passes and directions were performed to analyze the thickness-dependent and anisotropic mechanical properties.The results demonstrate that the microstructure changed with the welded passes,i.e.,a large number of grain boundary austenite,Widmanstätten austenite and a small number of tiny intragranular austenite existed at the surface passes,while a mass of intragranular austenite were found at the middle passes.Meanwhile,the Kurdjumov–Sachs orientation relationship was widespread at the welded zone.In addition,the yield and tensile strengths of the middle passes were greater than that of the surface passes due to the grain-boundary strengthening by tiny intragranular austenite.Furthermore,due to the existence of Kurdjumov–Sachs orientation relationship,the longitudinal yield and tensile strength were greater than transverse values,particularly for the middle passes.

High Efficiency and Quality of Multi-Pass Tandem Gas Metal Arc Welding for Thick Al 5083 Alloy Plates

Multi-pass tandem gas metal arc welding(TGMAW) for Al 5083 alloy plates with 30 mm thickness is carried out to study its high efficiency and high quality. The welding process is evaluated by high-speed photographs and electrical signals. The deposition rate and welding time are calculated to characterize the welding efficiency. The bead formation, porosity, microstructure and mechanical properties are tested and analyzed. The results indicate that though arc deflection occurs due to the electromagnetic interference between two arcs during TGMAW process, it does not affect the welding process stability significantly. The deposition rate and welding time of TGMAW process are about 15 g/min larger and about 16.7% less than those of gas metal arc welding(GMAW)process respectively, accompanied by the reduction of heat input. The TGMAW welded joint has less porosity and more refined microstructure to contribute to the improvement of mechanical properties(micro-hardness, tensile strength and ductility). It can be concluded that TGMAW process yields excellent performance of welded joint with improved welding efficiency, which makes it extremely practical during welding of thick plates.

铁基形状记忆合金与45钢焊接性能研究

对铁基Fe 30Mn 6Si形状记忆合金与 4 5钢的焊接性能进行了试验研究和分析。在选定的焊接方法和工艺参数条件下 ,焊接接头抗拉强度达 730MPa ,是母材强度的 92 .4 % ,在热影响区内 ,铁基形状记忆合金的性能稳定。因此 ,铁基形状记忆合金与 4 5钢具有良好的焊接行为。

现代电子产品焊接质量的检测技术

介绍了现代电子产品焊接质量的检测技术 ,以及用于检查焊点质量和组装板 (SMA)功能的测试仪器的工作原理及测试能力。目前常见和广泛使用的焊接质量检测方法是人工目测检查 ,其主要问题是其主观性 ,只能用来检测电子元件的形状、尺寸、颜色、表面特征及焊点的外观质量 ;自动光学检测 (AOI)可以在整个过程中发现和纠正缺陷 ,但只是外在的焊点缺陷 ;激光 /红外线组合式检测系统、X射线检测系统可以分析焊点微米级水平的缺陷 ,能找出其他检测所不能可靠地发现的缺陷 ,包括空洞、焊点形状差和冷焊锡点等 ;另外 ,X射线检测系统能一次测试单面或双面电路 ,准确地定位缺陷 ,获取工艺参数 ,例如锡膏厚度等。

Adaptive pass planning and optimization for robotic welding of complex joints

Current industrial robotic welding systems can- not achieve automated solutions for multi-layer multi-pass welding of complex joints due to the presence of non- uniform and irregular welding groove geometries. This paper presents an adaptive pass planning approach for robotic welding of such complex joints. The welding groove is first segmented considering both the variation in groove dimension and the reachability of the robot welding torch. For each welding segment, the welding passes are planned to be in accordance with welding practices, viz., keeping the same number of welding passes in each layer while maintaining consistent welding parameters. An adaptive pass adjustment scheme is developed to address the discrepancies between the simulated results and the actual welding deposition after finishing a few layers of welding. Corresponding robot paths are generated and optimized to ensure minimum joint movement subject to three constraints, viz., reachability, collision-free and singularity avoidance. The proposed approach has been sim- ulated with the arc welding of a Y-type joint found typically in offshore structures.

Anomalous residual austenite formation in root of welding layers of 9% Cr/CrMoV dissimilar welded joint

The morphology and distribution of residual austenite in the welded zone of 9% Cr/CrMoV dissimilar welded joint were observed by color metallographic method. Moreover, the details of the distribution, shape, length, length-to-width ratio, and the content of residual austenite in each welding layer were systematically characterized using Image-Pro Plus image analysis software. Different from the techniques such as X-ray diffraction, vibrating sample magnetometer, and electron backscatter diffraction that only involve the content of residual austenite, color metallographic method can offer much more details of the residual austenite, including the location, shape, size, and content, helping evaluate the overall characteristics of the residual austenite produced in the weld. It is interesting that a large amount of block-like and film-like residual austenite was found in the root of each welding layer, while rare at the top. The area fraction of residual austenite located in this zone was approximately 7.5% compared with only 0.5% at the top. In addition, the average area, length, and length-to-width ratio of dispersed residual austenite were quantitatively evaluated to be （4.7 ± 0.6）μm2, （5.1 ±0.6） μm, and （1.1 ± 0.1） μm, respectively. This variety of residual austenite was resulted from the tempering effect by latter welding layer on the previous one and different cooling rates in these two regions during the welding process.

爆炸焊接记忆合金Ni_(50)Ti_(50)与Cu界面的扩散机理

为了揭示焊接界面细观尺度扩散特征,采用内嵌入势函数(EAM势)对形状记忆合金Ni_(50)Ti_(50)和Cu的爆炸焊接界面进行分子动力学数值模拟,同时结合SEM、EDS测试方法对爆炸焊接界面微细观形貌及物理特征作实验分析。结果表明,记忆合金Ni_(50)Ti_(50)与Cu在采用u_z=–1500 m/s,u_x=700 m/s冲击碰撞工况下,体系的压强震荡逐渐变小,120ps以后趋于平衡,体系的温度稳定在1350 K左右,而压强稳定在28 GPa左右;在扩散层两侧Cu的原子浓度一直维持在5%左右,Ni和Ti的原子浓度在47%上下波动,界面扩散层厚度在1.03~1.45μm的范围内;采用SEM、EDS微观分析验证了焊接界面扩散层厚度约为1.56μm,基本与计算结果相一致。