Numerical simulation of spot welding for galvanised sheet steels

Abstract

Galvanised sheet steels are now widely used to be the substrate for body in white (BIW) construction in the automotive industry. Weldability of galvanised sheet steels much worsened compared to spot welding of low carbon steels. The present paper develops a 2D axisymmetric model and employs an incremental coupled thermal–electrical–mechanical analysis to predict the nugget development during resistance spot welding (RSW) of galvanised sheet steels. Temperature dependent contact resistance for faying surfaces was determined to take into account of the influence of zinc coat for spot welding galvanised sheet steels. The effect of dynamic contact radii on temperature distribution was studied and compared with results under constant contact area assumption. The predicted nugget shape and size agreed well with the experimental data. Higher current and longer welding time should be applied for galvanised sheet steels compared to low carbon steel spot welding. The proposed model can be applied to predict weld quality and choose optimal welding conditions for spot welding galvanised sheet steels.     

Dissimilar friction welding of induction surface-hardened steels and thermochemically treated steels

Results on friction welding of surface-hardened steels are analyzed based on experiments using induction-hardened steels as pivotal component, joined with quench-hardened steels and steels thermochemically treated by carburization and nitriding, respectively. Higher axial pressure needs to be applied, in order to fully expunge the hardened layers from the joining plane. A smooth surface for the burr, without cracks, can be obtained for adequate welding parameters and the burr can be subsequently removed without major risks, immediately after the friction welding process ends. For joining an induction hardened C55 steel with a quenched hardened C55 steel, the maximal friction pressure has to be limited to about 200 N/mm², in order to avoid materials separations in the centre of the joint. High axial pressures lead to good mechanical characteristic for friction welding an induction-hardened 34CrNiMo6 steel with a carburized 16MnCr5 steel. Friction welding of an induction-hardened C55 steel with a C45 nitrided steel showed that an increase of the friction upset distance to 6 mm favours the complete expulsion of the nitride debris, with positive effects on the quality and mechanical properties of the joint.     

Study of hyper-interfacial bonding of ultrafine-grained steels

To obtain so-called super-steels providing a good combination of high strength and high toughness, efforts are being made to develop ultrafine-grained steels involving intense grain size refinement with retention of a mild steel-equivalent low-alloy composition in order to lessen their environmental impact and reduce total life cycle costs.^1-5 Within this context, it is imperative to develop suitable welding and joining technologies for structural applications of ultrafine-grained steels; a number of previous studies have addressed their welding characteristics.^6-8 Developed ultrafine-grained steels, however, face a number of important problems such as grain coarsening, HAZ softening and microstructural changes due to the thermal effect of the welding process itself. Such microstructural changes are predicted to exert a significant effect on joint characteristics, particularly deterioration of welded joint performance in ultrafinegrained steels as steels subjected to a high degree of grain size control. Microstructural changes in the joints of ultrafine-grained steels, however, have not yet been satisfactorily investigated.     

Defect-free joining of zinc-coated steels by bifocal hybrid laser welding

Laser welding of zinc-coated steels in an overlap setup is prone to weld defects and seam expulsion reducing in particular the properties in mechanical loading and in general the deployability of such weldments in industry. Several laser welding process technologies failed to created defect-free welds in zinc-coated steels. This paper renders the welding of zinc-coated steels by the novel technology of bifocal hybrid laser welding. The zinc-coated steels under consideration are DX56D + Z, DC04 + ZE, and HXT700D. The bifocal hybrid laser system is realised by combining an Nd:YAG laser with a high power diode laser, both of 3 kW maximum output power. The beam parameter product (BPP) of the employed Nd:YAG laser of 25 mm mrad translates with an optical system of focal length f = 150 mm into a circular focus of diameter 0.45 mm, whereas the BPP of the HPDL of 85 mm × 200 mm mrad can achieve a rectangular focus of 0.9 mm × 3.7 mm. The optical system allows the respective focal plane and relative position of the foci to be independently vertically and horizontally positioned. This paper presents research into the causes of instabilities in laser welding of zinc-coated steels. Experimental evidence is considered and presented to establish the need for an empirical process model for stable laser welding of zinc-coated steels. The increase of process robustness is discussed.     

Welding of twinning-induced plasticity steels

This work focuses on the technical and technological aspects of fusion welding of high-manganese steels exhibiting twinning-induced plasticity (TWIP) for both similar and dissimilar joints. Changes in the alloy chemistry resulting from evaporation and dilution are discussed with respect to stacking fault energy and austenite stability. The influence of fusion welding on grain size and strength is also discussed. Conclusions are drawn with respect to optimization processes for fusion welding of TWIP steel.     

高强管线钢的焊接性及其焊接接头的耐腐蚀性

近年来,油气输送管道朝大管径方向发展,输送介质复杂,输送压力增大,使用条件越来越苛刘,因而管道材料的研究正朝着具有高强度、高韧性以及优良的现场焊接性等多方面性能发展,国产高强X70管线钢已在西气东输工程中投入使用。由于焊接工艺是输气管道铺设的主要工艺之一,高压输送管道的焊接部位,尤其是铺设管道环焊部位是失效事故的多发位王,因此,针对国产X70,XSO管线钢从焊接方法、焊接材料等方面进行了阐述,分析了其焊接性,并进一步讨论了其焊接接头的耐腐蚀性能。     

国内外双相不锈钢焊接的研究进展

主要介绍国内外双相不锈钢焊接在各个方面的研究进展.针对双相不锈钢焊接材料的开发,强调Ni和N元素在控制相平衡上的影响;介绍了国内外双相不锈钢焊接方法的最新动态,主要有埋弧焊、等离子弧焊和激光焊的改进、电阻对焊的尝试、新型双弧焊接技术的应用等;分析了奥氏体和铁素体两相比、有害析出物和氢脆对双相不锈钢焊接性的影响及解决措施;讨论了影响双相不锈钢焊接接头腐蚀性能和韧性的因素,对其影响机理进行了初步的解析;最后,进行了总结和展望.     

制造加氢反应器用Cr-Mo中温抗氢钢

介绍了高温、高压加氢反应器用Cr-Mo抗氢钢以及在生产过程中焊缝金属典型裂纹产生的原因及防止措施.并讨论了Cr-Mo钢焊接材料的选择原则、接热输入和焊后热处理规范对焊接接头性能的影响.     

Laser beam welding of dissimilar stainless steels in a fillet joint configuration

This paper investigates laser beam welding of dissimilar AISI 304L and AISI 430 stainless steels. Experimental studies were focused on effects of laser power, welding speed, defocus distance, beam incident angle, and line energy on weld bead geometry and shearing force. Metallurgical analysis was conducted on a selected weld only to show various microstructures typically formed at different zones and consequent change in microhardness. Laser power and welding speed were the most significant factors affecting weld geometry and shearing force. All the bead characteristics but radial penetration depth decreased with increased beam incident angle. The focused beam allowed selecting lower laser power and faster welding speed to obtain the same weld geometry. Weld shape factor increased rapidly due to keyhole formation for line energy input ranging from 15 kJ/m to 17 kJ/m. Fusion zone microstructures contained a variety of complex austenite-ferrite structures. Local microhardness of fusion zone was greater than that of both base metals.     

Microstructures and properties of laser/arc hybrid welds and autogenous laser welds in pipeline steels

Abstract

Lasers are capable of producing welds with deep penetration, low distortion and faster travel speeds, compared to arc welding. More recently, laser/arc hybrid welding processes have also been generating interest for industrial fabrication. In this paper, six carbon–manganese, mainly pipeline, steels were welded using both autogenous Nd:YAG laser welding, and Nd:YAG laser/MAG hybrid welding. The improvements in weld microstructures and weld metal toughness that are possible when using the hybrid process are described and illustrated. Laser/arc hybrid welding is shown to be a process that can generate good quality welds in commercially available pipeline steels. It also has the potential to complete girth welds in these steels with significantly fewer welding passes than are currently required for arc welded pipelines, reducing the joint completion time.     

Friction stir welding of duplex stainless steels

Duplex stainless steels are successful in a variety of applications such as the food industry, petrochemicals and plants for desalination of seawater, where high corrosion resistance and high mechanical strength are required. However, the beneficial microstructure may change during fusion welding steps, and it can compromise the performance of these materials. Friction stir welding is a solid-state process avoiding typical problems concerning solidification such as solidification cracks, liquation and segregation of alloying elements. Superduplex stainless steels can avoid unbalanced proportions of ferrite and austenite, formation of secondary deleterious phases and grain growth of ferrite in the heat-affected zone. Consolidated friction stir welded joints with full penetration 6 mm thick were obtained for UNS S32101 and S32205 duplex and S32750 and S32760 superduplex stainless steels. The friction stir welds were submitted to tensile tests indicating an improvement of strength in welded joints, showing increased yield and tensile strength for all studied cases. Regarding the microstructural characterization, an outstanding grain refinement was observed in the welded joint, achieving grain sizes as small as 1 μm. This refinement was associated with the combination of microstructural restoration mechanisms in the dual-phase microstructure promoted by severe deformation associated with a high temperature during the welding process.     

Welding HSLA line pipe steels

Summary This paper has reviewed the various aspects of weldability as it is influenced by the base metal composition and processing in HSLA line pipe steels. The Mo-Nb steels meet these stringent weldability requirements. Consumables have been developed for both girth and seam welding the Mo-Nb steels, and the strength and toughness required for severe service can be obtained with consumables of reasonable cost and good operating characteristics.Plenum Publishing Corporation is indebted to Climax Molybdenum Company, a division of A MAX Incorporated, 1 Greenwich Plaza, Greenwich, Connecticut 06830, for providing the original English version of this article.Published in Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 56–60, July, 1977.     

低碳钢与不锈钢焊接接头弯曲性能的分析

通过对Q235-B和316L异种钢I形和Y形坡口埋弧焊对接接头Q235-B一侧熔合区显微组织和元素分布及显微硬度的观测和分析,指出了在碳素结构钢与不锈钢异种金属的焊接接头中,碳素结构钢一侧出现硬而脆的熔合区;提出了减小熔合区的宽度是提高异种钢焊接接头抗弯曲性能的关键.此外研究了不同焊接工艺对焊接接头抗弯曲性能的影响机制,采用小尺寸的Y形坡口和使用含镍量高的焊丝,既有效地减小了熔合区的宽度,提高了异种钢焊接接头的抗弯曲性能,避免在对接接头双面埋弧焊时发生烧穿焊接缺陷.     

Development of ceramic backing for friction stir welding and processing

Usually, a workpiece is deformed during friction stir welding due to high applied loads. Consequently, fully and consolidated friction stir-welded joints as well as tool life time can be affected promoting unscheduled manufacturing stops, which favour decreasing the welding productivity. Furthermore, the workforce is dislocated to not predicted maintenance steps. This work proposes the development of a special ceramic backing to joining and processing material using FSW technologies. Four ceramic deposits were tested over a steel plate, which allowed selecting those with less porosity and, thus, better strength. This backing allowed us to obtain full penetration welds for duplex stainless steels, to high forces during engagement for high-strength low-alloy steels and to obtain consolidated aluminium–steel dissimilar joints. For the last one, there was not adherence of the soft material in the workpiece. In addition, the ceramic backing allowed us to confine the heat and plasticized metal, as well as develop established welding parameters.     

Embrittlement of ferritic chrome steels in welding

Conclusions High-temperature heating characteristic of a weld joint in the area of overheating of the heat-affected zone causes an increase in the parameters and the static distortions of the crystalline lattice of chrome steels with an increase in nitrogen content. At the same time, the inelastic effects, the Snoek and Kester peaks, increase, which is caused by the introduction of nitrogen into the crystalline lattice and its interaction with the fields of stresses and dislocations.After imitation of the structure of overheating steels contaminated with nitrogen have a high impact strength, which is an indication of the weak influence of supersaturation of the crystalline lattice on the tendency of chrome steels toward embrittlement in welding.An increase in the carbon content has a negative influence on the impact strength of chrome steels after high-temperature welding heating. In comparison with steels contaminated with nitrogen there is practically no increase in the lattice parameters of such steels. After high-temperature heating the static distortions of the lattice decrease. There is also a decrease in the peaks of internal friction caused by migration of carbon atoms along the interstices of the crystalline lattice into the zones of stresses and their interaction with the dislocations.Embrittlement of ferritic chrome steels as the result of carbide precipitates is also possible after short-time heating in the 550–850°C range, which is indicated by the decrease in the crystalline lattice parameters and also the maximum in internal friction caused by carbon atoms. In heating to 400–550°C nitrides are also formed together with carbides.The effects revealed after short-time heating make it possible to relate the mechanism of embrittlement of ferritic chrome steels in welding to strengthening of the heat-affected zone metal as the result of precipitates of finely dispersed carbonitrides.Central Scientific-Research Institute for Machine Building Technology Scientific Production Association. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 1, pp. 41–45, January, 1984.     

Structure and mechanism of formation of dissimilar welded joints in nuclear power plant made of austenitic and pearlitic steels

The structure and mechanism of the formation of welded joints in pearlitic and austenitic steels in power engineering structures are analyzed. The results of investigations of the crystal structure of metals and metallurgical processes taking place in the welding zone are presented. Recommendations are given for improving the welding technology and welding materials, and the chemical composition of the materials used in these applications is determined more accurately.     

镀锌钢板点焊电极寿命研究

通过在不对电极进行更换和修磨的情况下，对2种镀锌钢板进行连续点焊的电极寿命试验，探索焊接过程中电极直径的增加规律和影响因素，以及对熔核尺寸的影响，并简单分析电极在长时间焊接后的合金化程度。     

Effects of surface treatments of galvanized steels on projection welding procedure

A group of projection welding experiments and joints tension-shear tests are carried out for cold-rolled steel sheets, galvanized steel sheets (GSS) without treatment, GSS with phosphating and GSS with surface greasing, respectively. The experimental results are regressively analyzed on the computers, then the projection welded joint tension-shear strength curve and the perfect welding currents range of each material are obtained. The results show that surface treatments of galvanized steels have effects on their spot weldabilities. Among the four kinds of materials, GSS with surface greasing have the worst spot weldability, for they need higher welding current and have a narrow welding currem range.     

Stainless and acid-resisting steels and alloys

Conclusions Highly alloyed steels and alloys are produced in conformity with GOST or technical specifications in thick and thin sheets, beams and channels, bars, hot-rolled and cold-rolled pipe, and rod. Castings are produced in the specialized plant of the Ministry of Chemical and Petroleum Machine Building.The technology of welding stainless steels and alloys is given in [15] and [16].TsNIIChERMET. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 10, pp. 43–50, October, 1967.     

不同组织超细化预处理下的异种钢超塑焊接

通过对40Cr/T10A钢试样及试样待焊面表层分别实施盐浴加热循环淬火、高频淬火及激光淬火的组织超细化预处理,探讨了钢待焊表面组织对40Cr/T10A异材恒温超塑焊(ISSW) 工艺及接头质量的影响.试验结果表明,钢待焊表面组织对ISSW接头的形成有重要影响.待焊面组织越细,ISSW所需焊接温度向低温区移动,初始应变速率向高应变速率区域移动,ISSW所需时间越短;即使待焊双方一方实施组织超细化,也可实现接头抗拉强度达到40Cr母材的强度,但ISSW所需压接时间稍长.ISSW属小变形焊接,接头变形主要集中在原界面附近的淬火区,且T10A侧的变形均大于40Cr侧.