Friction stir welding of thin DH36 steel plate

Abstract

A series of 4, 6 and 8 mm DH36 steel welds were produced using optimum conditions for friction stir welding (FSW). Comparator welds in the same thickness from the same plates were produced using a single sided single pass process submerged arc welds (SAW). This work was carried out to evaluate the mechanical properties of FSW material with a view to its possible application in a shipbuilding production process route.

Overall, the performance of the FSW material was superior to the SAW comparators. Areas such as distortion and fatigue were particularly positive in the FSW material. An 8 mm thick plate was also produced using two FSW passes, one from either side, and it was found to have superior toughness and fatigue performance when compared to the single sided 8 mm FSW material. Some of these benefits are thought to have originated from the internal overlap zone between the two passes.     

Friction stir welding of multilayered steel

Abstract

This study investigates the mechanical properties and microstructure of friction stir butt welded high strength/ductility multilayered steel consisting of 15 alternating layers of SUS 301 austenitic stainless steel (eight layers) and SUS 420J2 martensitic stainless steel (seven layers) with a total thickness of 1·2 mm. With optimised welding parameters, defect free welds with an ultimate tensile strength (UTS) of 1240 MPa and a fracture elongation of 13% were accomplished. This corresponds to a joint efficiency of 90%. In this case, fracture occurred in the heat affected zone as a result of a very pronounced hardness drop in the martensitic layers resulting from the formation of a large amount of grain boundary precipitates, which were formed at temperatures ～750°C slightly below A_c1. By applying post-weld heat treatment, the hardness drop in the martensitic layers was removed and the tensile properties were enhanced to UTS of 1310 MPa (95% joint efficiency) and a fracture elongation of 22%.     

Thermomechanical deformation behaviour of DH36 steel during friction stir welding by experimental validation and modelling

Friction stir welding is a solid state thermomechanical deformation process from which the plasticisation behaviour of the stirred material can be evaluated through the study of flow stress evolution. Flow stress data also supporting the development of a local microstructural numerical model have been generated. Hot compression testing of DH36 steel has been performed at a temperature range of 700–1100°C and strain rates from 10^?3 to 10² s^?1 to study the alloy’s thermomechanical deformation behaviour in conditions that simulate the actual friction stir welding process. It has been found that the evolution of flow stress is significantly affected by the test temperature and deformation rate. The material’s constitutive equation and constants have been calculated after analysis of these data. Preliminary numerical analysis results are in good agreement with experimental observations.     

搅拌摩擦点焊

搅拌摩擦点焊(FSSw)是一种最近研究开发出来的新焊接技术.同目前的电阻点焊相比,该方法是具有节能、设备简单、焊点强度高、变形小、焊前表面清理简单,可以焊接厚度差别大的材料,特别适用于高强度铝合金的焊接.重点介绍该技术的基本原理、优缺点、焊接设备,对几种典型铝合金的焊接工艺参数、接头强度和组织等进行了比较详细的分析,从而对该技术有一个全面的了解.     

Research on multi-objective optimization of GMAW welding of DH36 steel

Weld bead morphology plays an important role in welding procedure specification and welding process planning. In order to obtain the quantitative relationship between process parameters and weld morphology of DH36 marine steel plate, grey correlation method was used to study multiple morphology characteristics simultaneously. Eighteen experimental runs were proposed according to orthogonal method. With grey correlation theory, three response objectives, aspect ratio, depth of penetration and weld were transformed into a single grey correlation grade(GRG). The process parameters were quantitatively correlated to the GRG value and optimized with the target of maximum aspect ratio, minimum depth of penetration and maximum weld area. The results show that the optimized weld bead morphology is better than other weld bead morphology. The relative error of the predicted GRG with respect to the actual value is 5.06%, which further verifies the accuracy of the established model. The microstructure and hardness analysis suggests that the optimized welded joint has obtained required mechanical properties.The research outcomes provide a theoretical basis for multi-objective optimization of arc welding morphology in practical applications.     

低频相位对双丝双脉冲GMAW熔滴过渡和焊缝成形的影响

采用不同直流脉冲匹配的tandem焊枪实现了12 mm厚Q235钢共熔池打底焊接,并利用高速图像(HSI)和实时电信号对焊接过程进行实时动态检测,研究了焊接速度对焊缝成形、焊接电弧形态和焊接过程稳定性的影响. 结果表明,焊接速度主要对焊缝成形和焊接过程稳定性造成影响,对电弧形态的影响不大. 随着焊接速度的增加,电弧稳定性先增大后减小,在焊接速度为40 mm/s时,背部自由成形最佳. 不同焊接速度下,主丝电弧都保持较高的挺度,几乎不发生偏移,从丝电弧形态在单个脉冲周期内通过产生9° ~ 15°的规律性摆动,促进熔池中部金属向侧壁流动,减小熔池后端金属的累积,从而消除焊缝表面的驼峰和起脊缺陷,提升了整体光洁度. 主丝的焊接稳定性整体高于从丝,当焊接速度为40 mm/s时,两电弧稳定性最好.     

Friction stir keyholeless spot welding of AZ31 Mg alloy-mild steel

Friction stir keyholeless spot welding (FSKSW) using a retractable pin for 1.0 mm thick galvanized mild steel and 3 mm thick AZ31B magnesium alloy in a lap configuration was investigated. The process variables were optimized in terms of the joint strength. The effects of the stacking sequence on joint formation and the joining mechanism of FSKSW AZ31B-to-mild steel joints were also analyzed. It shows that the process window and joint strength are strongly influenced by the stacking sequence of the workpieces. While the process window is narrow and unstable for FSKSW of a magnesium-to-steel stack-up, a desirable process was established for the steel-to-magnesium stacking sequence, a desirable process and higher strength joint can be got when the steel-to-magnesium stacking sequence. XRD phase and EPMA analyses of the FSKSW joint showed that the intermetallic compounds are formed at the steel-to-magnesium interface, and the element diffusion between the mild steel and AZ31B magnesium alloy revealed that the joining methods for FSKSW joints is the main mechanical joining along with certain metallurgical bonding.     

基于DH36船用钢材的垂直气电焊工艺

针对DH36船用钢材编制了垂直气电自动焊焊接工艺,并进行焊接工艺认可试验。以垂直气电焊技术代替传统的人工焊接技术,实现了DH36船用厚板立缝的一次焊接成形,它凭借焊接速度快、焊缝质量好等优点,得到了广泛地应用。     

铝合金船舶的摩擦搅拌焊接工艺

摩擦搅拌焊(FSW)是在低于工件材料熔点情况下操作的固相焊接,是在旋转情况下通过一种耐磨工具将板材或型材材料连接的工艺,可用于铝、镁、铜等的焊接,焊接质量优良.通常情况下,摩擦搅拌焊的焊缝强度超过热影响区.介绍了摩擦搅拌焊在造船和船舶制造业上的应用,以及船舶工业的研究需求.     

Friction stir welding of aircraft wings

ABSTRACT

To reduce the weight of the wings of the TU-204SM aircraft, investigations were carried out to design the upper wing panel made of the V-1469 high-strength aluminium–lithium alloy of the third generation. The technology of friction stir welding was developed and fragments of the welded panel produced. The tests of the stability under compression showed that the application of the welded panels reduces the weight of the wing by up to ~10% and increases the stability and load carrying capacity by up to ~30%.     

Friction stir welding of copper alloys

Copper plates ,brass plates and copper/brass plates were friction stir welded with various parameters. Experimental results show that the microstructure of the weld is characterized by its much finer grains as contrasted with the coarse grains of parent materials and the heat-affected zones are very narrow. The microhardness of the copper weld is a little higher than that of parent plate. The microhardness of brass weld is about 25% higher than that of parent material. The tensile strength of copper joints increases with increasing welding speed in the test range. The range of parameters to obtain good welds for copper is much wider than that for brass. When different materials were welded, the position of copper plate before welding affected the quality of FSW joints. If the copperplate was put on the advancing side of weld, the good quality of weld could be got under proper parameters.     

铝合金船舶的搅拌摩擦焊接工艺

0 引言 由英国焊接研究所(TWI)发明的搅拌摩擦焊(Friction Stir Welding简称FSW),是用一种利用耐磨的旋转工具将铝、镁和铜的板材或型材材料连接的工艺.     

塑料板材搅拌摩擦焊工艺

以6mm和8mm聚氯乙稀板材为研究对象,用搅拌摩擦焊方法进行了工艺可焊性试验。试验证明,一定厚度的塑料板,不开坡口,用搅拌摩擦焊方法可一次焊成。虽然影响接头质量的因素很多,但只要焊接参数选择恰当,就能获得令人满意的焊接接头。     

铝合金的搅拌摩擦焊

在详细介绍搅拌摩擦焊原理，特点的基础上，针对铝合金的搅拌摩擦焊特点，性能以及工业应用进行了阐述，并且对搅拌摩擦焊在中国市场的发展和应用作了简略介绍和预测。     

Friction stir welding of 304 stainless steel using Ir based alloy tool

Abstract

In order to investigate the durability of an Ir based alloy tool, friction stir welding (FSW) of 304 stainless steel plates was performed under various welding conditions, and the mechanical properties of the joints were measured. Defect free joints are possible under certain conditions, and the mechanical properties of the joints are the same as the base material. When the rotation pitch is ～0·3, the degree of wear of the Ir based alloy tool with 1·4 mm probe height, which was used for the FSW of a 304 stainless steel plate with 2 mm thickness, was less than or equal to that of the polycrystalline cubic boron nitride tool with 2 mm probe height, which was used for the FSW of a 304 stainless steel plate with 9 mm thickness. The result of the tool life test in this study showed that the Ir based alloy tool enabled the FSW of 304 stainless steel over a 75 m length.     

Friction stir scribe welding technique for dissimilar joining of aluminium and galvanised steel

Friction stir scribe technology, a derivative of friction stir welding, was applied for the dissimilar lap welding of an aluminium alloy and galvanised mild steel sheets. During the process, the rotating tool with a cobalt steel scribe first penetrated the top material – aluminium – and then the scribe cuts the bottom material – steel. The steel was displaced into the upper material to produce a characteristic hook feature. Lap welds were shear tested, and their fracture paths were studied. Welding parameters affected the welding features, including hook height, which turned out to be highly related to fracture position. Therefore, in this paper, the relationships among welding parameters, hook height, joint strength and fracture position are presented. In addition, the influence of zinc coating on joint strength was also studied.     

Friction stir spot welding of aluminium to steel by rotating tool without probe

A friction stir spot welding process, in which a rotating tool without a probe was employed, was applied to a lap joint of an aluminium plate to a low carbon steel plate. The thicknesses of both plates were 0.5 mm. In this process, the rotating tool of 5 mm diameter, rotating at 18,000 rpm, was plunged into the aluminium plate at a rate of 2 mm/s, and then kept at a maximum plunged depth of 0.05–0.35 mm for 0–2 s (dwell time). In the weld obtained by this process, a hole due to the impression of the penetrated tool probe was not formed, although a slight depression by the tool plunging remained. At tool plunge depths of 0.1 mm or over, it was possible to weld the two plates. The maximum tensile failure load of 454 N was obtained at a plunge depth of 0.1 mm and a dwell time of 1.5 s. Its joint was fractured at an almost constant load along the periphery of the depression, leaving a part of the aluminium plate on the steel plate surface. Based on the observation of the weld interface microstructure and metal flow of aluminium in the weld, controlling factors of the joint strength were discussed.