基于纵向磁场控制的大直径空心螺柱焊接工艺

采用电弧螺柱焊方法对外径20 mm、内径10 mm的空心螺柱与45钢板材进行焊接,研究了旋弧磁场对接头显微组织特征及力学性能的影响. 结果表明,在纵向旋弧磁场作用下,电弧中电荷受洛伦兹力作用呈螺旋运动,接头外观成形得到改善. 受磁场控制的电弧持续搅拌熔池,改善了焊接热循环条件,影响了熔池凝固结晶过程. 接头中先共析铁素体呈有规律的网状分布,珠光体也变得细化. 接头温度梯度减小使得固态相变时间增长,母材侧热影响区马氏体数量显著下降,热影响区宽度变小. 但旋弧磁场电流过大时焊接过程飞溅倾向明显增大,焊缝中气孔增多. 在焊接时间1 400 ms、焊接电流800 A、旋弧磁场电流0.43 A时,电弧在空心螺柱端面充分燃烧,接头抗剪强度可达到325 MPa.     

电弧螺柱焊技术的发展与应用

综述了电弧螺柱焊技术的发展和应用。作为一种广泛应用的螺柱焊接方法，电弧螺柱焊技术具有焊接效率高，易于实现自动化控制等优点。以焊接设备的发展更新、焊接材料的研究及应用领域为主要内容，对电弧螺柱焊中的普通电弧螺柱焊和电容储能电弧螺柱焊进行了比较；介绍了电弧螺柱焊中新发展的短周期控制方法，通过短周期拉弧螺柱焊技术与传统电弧螺柱焊技术的对比，突出了短周期控制方法的特点和优点；指出短周期拉弧螺柱焊是当前占主导地位的电弧螺柱焊方法，大直径螺柱的短周期拉弧螺柱焊研究将是重要的研究方向。     

空心螺柱旋弧焊接方法

基于纵向发散型磁场迫使电弧沿螺柱壁旋转的思路,提出了空心螺柱旋弧焊接新工艺。针对外径12mm、壁厚3mm的空心螺柱,实现了螺柱焊电弧绕螺柱四周壁的均匀旋转。焊接工艺试验表明,旋弧螺柱焊工艺参数明显大于同外径实心螺柱,焊接工艺有较大的规范窗口,但相对实心螺柱窗口变窄,最佳旋弧电流参数范围为1～2A,焊接时间为600～700ms,焊接电流为800～900A。接头性能检测表明,旋弧螺柱焊获得了饱满美观的螺柱焊成形,宏观组织检测未发现未熔合、夹渣、气孔等焊接缺陷,界面焊合率达到了100%,接头强度可保持在330～390MPa。     

铝合金TIG电弧横焊接头缺陷及控制

重型运载火箭燃料贮箱要求对铝合金进行立式装配焊接,TIG电弧横焊是能够较好满足制造要求的方法之一.对铝合金TIG电弧横焊接头的成形特点和焊接缺陷进行分析,利用平板堆焊试验研究焊接电流、焊接速度和焊枪角度对焊缝正面偏移量的影响,最后研究焊接电流频率对气孔缺陷的影响规律.结果表明,采用较小的焊接电流、较快的焊接速度有助于降低焊缝正面的不对称性,利用电弧分力可以抑制熔池下淌,焊接频率为100 Hz时气孔缺陷最少.结合上述试验结果提出了铝合金横焊缺陷的控制措施并进行了试验验证.     

Flux shielded arc butt welding of concrete reinforcing steel

Abstract

The present paper reports on a new variant of flux shielded arc butt welding without the addition of a filler material, applied to steel bars for concrete reinforcement. The welding process is described, including the arc ignition and forcing together of the workpieces, via the application of a mechanical force, to form an upset. A new portable machine is described, using which it is possible to apply flux shielded arc welding on site. Experiments were carried out, from which optimum welding parameters such as welding current, weld time, and upsetting force were found. The strength properties of the welded joints obtained were determined via mechanical testing, i.e. a bend test, a tensile strength test, and an impact toughness test. Macroscopic sections of the welded joints were also produced. A quality analysis of the butt welded joints showed that the mechanical properties of the joints were equivalent or even superior to the properties of the parent metal.     

Soft variable polarity plasma arc horizontal welding technology and weld asymmetry

Abstract

Soft variable polarity plasma arc welding technology has been proposed to solve the problems in horizontal position welding for aluminium alloys. Arc thermal field shape, arc pressure distribution and the characteristic of the weld pool, which are important for keyhole stability, have been changed compared with the ordinary variable polarity plasma arc. Its stability in application can be evaluated by the operational window. The thermal cycle curves, microstructures and microhardness of the horizontal position weld indicate the weld asymmetry. The influence of asymmetry as well as welding defects on tensile strength and fracture behaviour has been studied. The fundamental reason for the asymmetry was considered as the asymmetric fluid flow around the keyhole in the weld pool.     

Weld zone characteristic and mechanical performance of in situ titanium matrix composites using gas tungsten arc welding (GTAW)

Abstract

In situ TiB_w and La₂O₃ reinforced titanium matrix composites were successfully fusion welded by the gas tungsten arc welding (GTAW) process and the weldability and feasibility for composites were studied, and uniform and defect free welds were produced with sound welding parameters. Microstructural observations showed that the joint has a distinctly identified weld zone characteristic. In addition, the distribution and size of TiB_w in the weld became much more homogeneous and smaller. Moreover, the welded joints exhibited good mechanical properties at ambient temperature and the strength equal to the base metal at elevated temperature. The fracture mechanism of TiB_w in the weld also was investigated.     

Experimental and numerical investigation on combined girth welding of API X80 pipeline steel

Abstract

API X80 pipeline steel is widely used in natural gas and oil transportation. In this study, X80 pipeline steels with 18.4?mm thickness and 1219?mm diameter, made in China, were welded by a combined girth welding technology. Experimental results showed that microstructures in weld metal and coarse grain heat affected zone are mainly composed of coarsening bainite grains with dimensions of 20–50?μm, and Vickers hardness in weld seam is lowered by the seven-pass welding process. Simulated results illustrated that repeatedly thermal cycles imposed by the combined multipass girth welding process easily result in softened weld joints. The predicted microstructures, phase compositions and hardness in weld metal are in agreement with the measured ones. The results could be applied to optimise this combined girth welding process and improve the weld quality of API X80 pipeline steel and even higher grade pipeline steels.     

窄间隙热丝TIG焊接工艺研究及缺陷分析

研究了Polysoude窄间隙热丝TIG焊接系统的焊接工艺,分析焊缝产生缺陷的原因。通过对焊接电流、电弧电压、送丝速度、焊接速度、热丝电流等参数的优化分析,得到一组相互匹配的最优参数组合。试验结果表明,采用优化后的工艺参数对大口径无缝钢管进行焊接,可以获得焊缝表面形貌美观、内部无缺陷的优质焊接接头。     

Suggestion of welding procedure for compressive residual stress induction by using low transformation temperature welding materials

ABSTRACT

To understand the cause of compressive residual stress in welded joints, we analysed by numerical analysis the effect of welding pass sequence using low transformation temperature (LTT) welding materials on residual stress around the weld toe of boxing fillet welded joints. It was determined by numerical analysis that the produced compressive residual stress and the influence of the stiffeners are reduced in the equivalent position of the weld toe in a fillet welded joint because of the influence on the behaviour of the stiffener in the weld being due to residual stress distribution around the weld toe. The residual stress reduction method of extending the length of the welded bead and releasing the weld toe from the stiffener, similar to the concept of discarding a bead to reduce tensile residual stress, was effective in fillet welded joints. Numerical analysis of the relationship between residual stress around the weld toe and width of the weld bead in the bead-on-plate welding model clarified that compressive residual stress can be introduced around the weld toe by having a wide width weld bead. In addition, a fully penetrated welded joint was very effective for causing compressive residual stress around the weld toe.     

7A52铝合金-钢异种结构CMT熔钎焊接头组织及镀镍层的行为与影响

以ER4043铝硅焊丝为填充金属,研究了Q235钢螺柱与7A52铝合金板CMT焊接工艺,在焊接电流115~135 A,电弧电压14.5~16.5 V,焊接速度0.3 m/min条件下,焊接过程稳定,焊缝成形连续美观.结果表明,7A52铝合金侧熔合区界面为熔焊特征,铝母材发生熔合,熔合良好;钢螺柱侧熔合区为钎焊特征,界面存在反应层,由靠近钢螺柱的Fe₂Al₅层和靠近焊缝侧的FeAl₃层组成,整体反应层厚度由根趾向焊趾方向逐渐减小.焊趾部位出现富镍区,主要由Al₃Ni的共晶组织及少量Al₃Ni₂组成.与无镀镍层焊缝比较表明,镀镍层在焊接过程的行为降低了界面反应层厚度,且通过形成富镍区,降低了接头的脆性,使接头抗剪切强度提高了15%~19%,最高达到146.9 MPa,满足了高强铝合金螺柱焊接的质量要求.     

Investigation on the stepping arc stud welding process

0IntroductionArc stud welding is gradually becoming an increasingimportant joining process fromthe firstpractical applicationdeveloped originally for the shipbuilding industry as a re-placement of the time consuming drilling and boltingprocess in1939[1].T…     

间隙对栓钉穿透焊过程的影响及其对策

栓钉穿透焊是用于建筑中压型钢板组合梁的焊接方法．其中,压型钢板与钢梁之间的间隙是影响穿透焊过程的重要因素。基于步进式电弧螺柱焊方法。以焊接过程中螺柱与工件之间挤压力为控制量．实现时螺柱进进深度的控制。在此基础之上,设计了栓钉穿透焊模拟试验。试验结果表明．步进式电弧螺拄焊中可以实现螺柱送进深度的自动控制．无需在焊前预先设置螺柱送进深度;在穿透焊中采用螺柱送进深度控制法,减小了间隙对焊接过程的影响．保证了焊接过程的顺利实现。     

双丝埋弧焊接头性能研究

在16Mn钢板上进行双丝自动埋弧焊工艺试验,得到了不同焊接速度下的焊件.对不同工艺参数下得到的焊接接头试样进行了拉伸试验、硬度测试以及金属显微组织观察,并计算了双丝自动埋弧焊时的熔敷率.结果表明:采用双丝埋弧焊得到的焊缝外形美观;金属熔敷率与焊接速度成反比;随着焊接速度的降低焊接线能量相应的增大,较长的高温停留时间会促...     

电弧螺柱焊中实现螺柱的低速送进

螺柱送进速度是电弧螺柱焊中的一个重要参数。基于对工程中广泛应用的电磁式螺柱焊枪工作原理的深入分析，提出螺柱低速送进的同时提供足够的挤压力可以实现电弧螺柱焊接，研制开发了步进式电弧螺柱焊枪及其控制系统。作为实现螺柱低速送进的焊枪，其动力机构为步进电机，螺旋传动装置为运动机构主体，保证螺柱低速送进时对接头处金属具有足够的挤压力。试验结果表明，采用步进式电弧螺柱焊枪，螺柱低速送进可以完成电弧螺柱焊过程；弯曲试验结果表明螺柱焊接头能满足使用要求。     

Influence of welding position and parameters in orbital tig welding applied to low-carbon steel pipes

The most notable characteristic of Orbital TIG welding is the constant geometric profile of the tubes. In the context of orbital TIG welding of tubes with a large diameter and thick walls, the relationship between the welding position, the use of constant or pulsed current and also the value of the average current on the geometric characteristics of the beads obtained was studied. We deposited welds on SAE 1020 carbon steel tubes, as well as taking macrographs of the cross-sections of the beads using optical microscopy. High-definition films were used to understand the behaviour of the weld pool in different welding positions. The geometric characteristics were quantified using macrographs and software, and the relationship between these characteristics and the above-mentioned variables were traced. In addition, an analysis of the microstructure of the samples was carried out, correlating with Vickers microhardness. It was concluded that the beads welded with pulsed current were more reinforced and wider, as well as being harder and having a finer microstructure. The vertical up position resulted in beads with a lower shape factor and more penetration, and the overhead position resulted in beads with a low shape factor.     

Numerical modelling of temperature distribution during multipass welding of plates

Abstract

Welding is a reliable, cost effective, and efficient metal joining process. Manual metal arc welding (MMAW) is a widely used welding process in industry and multipass welding is very frequently used in the MMAW process. The temperature distribution that prevails during multipass welding affects the material microstructure and hardness of the regions near the weld, and the residual stresses that will be present in the material after cooling to room temperature. These changes will consequently affect the performance of the welded joint. In the present work, a computer model based on the control volume method has been developed to predict the temperature distribution during multipass welding of plates using the MMAW process. To validate the computer model, the temperature distribution was measured experimentally in a 12 mm thickness stainless steel weld pad during multipass welding. The welding parameters were used as input data for the computer model. The computer predictions and the experimentally measured temperature distributions agree well.     

X80管线钢焊条电弧焊接头组织与耐蚀性分析

利用双熔敷极焊条电弧焊技术对X80管线钢进行了焊接,并在焊接接头成分、组织及耐蚀性方面与传统焊条电弧焊进行了对比分析.结果表明,双熔敷极焊条电弧焊技术熔敷效率高,但受其结构及药皮重量系数的影响焊缝中合金元素的含量比普通焊接焊缝的低,且焊缝中多边形铁素体含量较高,另一方面由于对母材的热输入较低,使得其粗晶区组织较为细小,这有利于其性能的提高;对0.5 M Na₂CO₃-1 M NaHCO₃溶液及通饱和CO₂的NACE A溶液中的耐蚀性研究发现,焊缝及粗晶区耐蚀性均差于母材,且采用双熔敷极焊条电弧焊技术有利于提高焊缝及粗晶区的耐蚀性.     

Nd:YAG激光+CMT电弧复合热源横焊工艺参数对焊缝形貌的影响

以304不锈钢为对象,借助横焊焊缝横断面图像来分析Nd:YAG激光+CMT电弧复合热源横焊焊缝横断面的成形特征,研究了Nd:YAG激光+CMT电弧复合热源横焊过程中焊接工艺参数对焊缝横断面形貌的影响.结果表明,在Nd:YAG激光+CMT电弧复合热源横焊中,焊接工艺参数对横焊焊缝横断面形貌的影响显著;Nd:YAG激光加入CMT电弧焊中明显提高了复合焊缝以及复合焊中CMT焊缝的熔深;采取适当的焊接工艺参数(小的光丝间距、大的激光功率、小的焊接速度、适合的离焦量以及小的或大的CMT功率)可以避免熔池机械式叠加和焊缝横断面错位现象,使得焊缝成形良好.     

单片机控制的电弧螺柱焊机

研制了RSN3—3150型电弧螺柱焊机。该焊机内部选用了MICROCHIP公司的PIC16F74单片机作为控制核心,控制功能强大。螺柱焊接过程由单片机控制．简单可靠,并且具有显示焊接电流、焊接电压、焊接时间以及焊接计数和短路保护等功能。