Hybridization of filler wire in multi-pass gas metal arc welding of SA516 Gr70 carbon steel

In the present investigation, multi-pass gas metal arc welding (GMAW) of SA516 Gr70 carbon steel was carried out by different filler wires such as solid, metal cored and flux cored, wherein, other process parameters were kept constant. The hybrid approach of multi-pass filler wires was applied to obtain three different welds. The root pass was filled by a solid wire for all three cases while the subsequent filler pass was applied through solid, flux-cored and metal cored filler wires, respectively. Metallographic, mechanical and metallurgical analyses such as macrograph study, optical microscopy, tensile testing and hardness variations were performed to address the quality of weld. The results revealed that defect-free sound welds were produced by the hybrid approach of different filler wires in multi-pass GMAW. Overall cost and time reduction can be achieved through hybrid filler welds, without affecting their mechanical strength. Angular distortion was reported minimum at hybrid weld of solid and metal cored filler wire. Maximum reinforcement with higher penetration was observed at weld of solid and metal cored filler wire. Impact toughness was reported higher in case of hybrid weld of solid and flux cored filler wire. Higher macro hardness was reported at weld of solid and flux cored filler wire.     

Hardfacing of Wear-Resistant Deposits by MAG Welding with a Flux-Cored Wire Having Graphite in Its Filling

A high carbon content in a ledeburite-martensite deposit provides high wear resistance. This can be accomplished in hardfacing by MAG welding with covered electrodes, alloying fluxes, and flux-cored wires. Hardfacing with covered electrodes is not efficient, whereas application of alloying fluxes is suitable only for the flat welding position. Hardfacing by flux-cored MAG welding, however, is efficient and suitable also for out-of-position welding, i.e., in the horizontal-vertical and overhead positions, which is particularly important in maintenance. The paper deals with the investigations of the influence of hardfacing-weld alloying by means of the cored-wire filling in hardfacing both by CO₂ welding and welding with no externally supplied shielding medium. The efficiency of alloying the hardfacing weld depended on the composition and the filling ratio of the wire. In hardfacing of martensite-ledeburite deposits, the high carbon content in the deposit was provided by the addition of graphite to the cored-wire filling. A result of the high graphite content in the filling was a reduction of the filling ratio of the wire, and, consequently, weaker alloying of the hardfacing weld. As little as 10 wt.% graphite in the wire filling substantially affects alloying of the hardfacing weld. In this case, the amount of carbide-forming elements in the hardfacing weld will be reduced by around 4 wt.% whereas the carbon content will increase by as little as 1%, which, however, is enough to obtain high-quality martensite-ledeburite wear-resistant deposits with S-BC3 cored wires and with no externally supplied shielding medium of which the chemical composition, structure, and wear resistance were quite comparable to those obtained with a CrWC 600 covered wire (produced by SZ-Elektrode, Jesenice). Advantages of the cored wire over the covered electrode are substantially higher performance and lower consumption of the electric current.     

An outlook on comparison of hybrid welds of different root pass and filler pass of FCAW and GMAW with classical welds of similar root pass and filler pass

In the present study, gas metal arc welding and flux cored arc welding were applied on SA516 Gr70 carbon steel material. Two different hybrid passes were applied, wherein flux cored wire and solid wire were applied to root pass and filler pass one by one and vice versa. Besides, two more welds of similar electrode root pass and filler pass of flux cored arc welding and gas metal arc welding were acquired. The comparative analysis was carried out in terms of macrostructure and microstructure examination, tensile testing, hardness variations, and impact testing for these classical welds and hybrid welds. The results reveal that, hybrid welds lead to better impact properties relative to classical welds. Maximum angular distortion of 2.66° was reported with classical weld of gas metal arc welding with solid wire root pass and same filler pass. The maximum impact toughness of 49 J/m³ was reported for flux cored root pass and solid wire filler pass at the weld zone. Maximum tensile strength of 596 MPa was reported for hybrid weld of solid root pass and flux cored filler pass. Microstructures are reported with the presence of different acicular ferrite and grain boundary ferrite. Maximum acicular ferrite of 61% was reported with classical weld of flux cored arc welding.     

Influence of Heat Input on Martensite Formation and Impact Property of Ferritic-Austenitic Dissimilar Weld Metals

The effect of heat input on martensite formation and impact properties of gas metal arc welded modified ferritic stainless steel (409M) sheets (as received) with thickness of 4 mm was described in detail in this work. The welded joints were prepared under three heat input conditions, i.e. 0.4, 0.5 and 0.6 kJ/mm using two different austenitic filler wires (308L and 316L) and shielding gas composition of Ar + 5% CO2. The welded joints were evaluated by microstructure and charpy impact toughness. The dependence of weld metal microstructure on heat input and filler wires were determined by dilution calculation, Creq/Nieq ratio, stacking fault energy (SFE), optical microscopy (OM) and transmission electron microscopy (TEM). It was observed that the microstructure as well as impact property of weld metal was significantly affected by the heat input and filler wire. Weld metals prepared by high heat input exhibited higher amount of martensite laths and toughness compared with those prepared by medium and low heat inputs, which was true for both the filler wires. Furthermore, 308L weld metals in general provided higher amount of martensite laths and toughness than 316L weld metals.     

Ti对金红石型药芯焊丝熔敷金属组织性能影响

以金红石型药芯焊丝为基础,通过在焊丝中加入不同含量的钛铁,研究了Ti对熔敷金属组织及力学性能的影响。结果表明,随焊丝钛含量的增加,脱氧方式从Ti、Si、Mn联合脱氧逐渐转为以Ti脱氧为主,且熔敷金属中夹杂物的Ti含量逐渐增大,同时熔敷金属中合金元素含量增加,屈服强度逐渐趋近抗拉强度,塑性变差。组织分析发现,以复合氧化物形式存在的化合钛对针状铁素体的形成有促进作用,以合金元素形式存在的固溶钛对针状铁素体的形成有抑制作用。     

Effect of welding wire and groove angle on mechanical properties of high strength steel welded joints

Mechanical properties of high strength steel welded joints strictly depend on the welding process, the filler material composition and the welding geometry. This study investigates the effects of using cored and solid welding wires and implementing various groove angles on the mechanical performance of weld joints which were fabricated employing the gas metal arc welding process. It was found that weld joints of low alloy, high strength steels using low alloy steel cored welding wires exhibited higher tensile strength than that of low alloy steel solid wire and chromium‐nickel steel bare welding wire when the method of gas metal arc welding is employed. The effect of groove angle on the strength and toughness of V‐groove and double V‐groove butt‐joints was investigated. V‐groove joints, with higher tensile strength than double V‐groove joints in the whole range of groove angles, were superior in toughness for small groove angles, but impact toughness values of both joints were comparable for large angles. The effect of heat input and cooling rate on the weld microstructure and weld strength was also investigated by performing thermal analysis employing the commercial software ANSYS. It was concluded that cooling rate and solidification growth rate determined the microstructure of the weld zone which had great consequences in regard to mechanical properties.     

Influence of grain refining elements on mechanical properties of AISI 430 ferritic stainless steel weldments – Taguchi approach

The effect of grain refining elements such as copper, titanium and aluminum on transverse tensile strength, ductility, impact toughness, microhardness and austenite content of AISI 430 ferritic stainless steel welds through Gas Tungsten Arc Welding (GTAW) process in as-welded condition was studied. Taguchi method was used to optimize the weight percentage of copper, titanium and aluminum for maximizing the mechanical properties and austenite content in the weld region of ferritic stainless steel welds. Based on Taguchi orthogonal array the regression equations were developed for predicting the mechanical properties of ferritic stainless steel welds within the range of grain refining elements. The observed mechanical properties and austenite content have been correlated with microstructure and fracture features.     

药芯焊丝Mo含量对低合金钢焊缝金属性能影响

通过在金红石型药芯焊丝中加入不同含量的金属Mo,研究了Mo对熔敷金属组织及力学性能的影响。研究表明,药芯焊丝中的Mo基本全部过渡到焊缝中;添加微量Mo时,焊缝金属强度显著提升,同时冲击韧性恶化严重;进一步增加Mo含量,焊缝金属强化效果不明显,而冲击性能继续下降。组织分析发现,增加焊丝中的Mo含量,首先会降低奥氏体转变温度,增加基体中的碳化物析出相;继续增加Mo时,碳化物含量减少,但M-A组元含量增加,导致韧性持续下降。     

Influences of titanium and manganese on high strength low alloy SAW weld metal properties

The objective of this work was to study the influence of titanium on API 5L-X70 steel weld metal properties at manganese levels of 1.4 and 2%. The best mechanical properties in the weld series were obtained in two compositions, i.e. 1.92%Mn–0.02%Ti and 1.40%Mn–0.08%Ti. In both groups of welds, acicular ferrite in the microstructure was increased with addition of titanium in the range of 0.02–0.08%. Manganese helped to refine and homogenize weld microstructures. Increased hardenability of the weld due to further addition of titanium or manganese encouraged grain boundary nucleation of bainite with greater frequency than intragranular nucleation of acicular ferrite. Also, the amount of manganese in inclusions was decreased with the addition of titanium to the weld. The impact toughness of the weld metal was improved by addition of titanium, but beyond the optimal titanium percentage, the quasi-cleavage fracture mode appeared in the specimens again.     

Investigation on various welding consumables on properties of carbon steel material in gas metal arc welding under constant voltage mode

In this present work, the influence of different consumables on weld properties of carbon steel plate was studied by automatic gas metal arc welding under constant voltage mode. For all experiments, the process parameters such as welding current of 200 A, voltage of 28 V and welding speed of 200 mm/min were kept constant. The results indicate that the angular distortion remained higher for solid wire, whereas it was minimum for flux-cored wire and the lowest in metal-cored wire. Mechanical properties such as yield strength, tensile strength, elongation and joint efficiency remained high for solid wire relative to cored wire. Excellent impact toughness of the weld metal and heat-affected zone was reported for the flux-cored welds compared with solid wire and metal-cored welds.     

Simulations of Transformation Kinetics in a Multi-Pass Weld

This paper discusses the thermal welding cycle's influence on microstructural changes in the weld metal. We examined the kinetics of austenite formation by the application of simulated microstructures. Special attention was dedicated to the thermal welding cycle's influence on the formation of microstructures with very low toughness, which could be potential triggers of brittle fracture. The simulated microstructures were prepared by the application of several simulated thermal cycles with different peak temperatures, on samples of real single-pass weld metal.

The results of this research show that martensite-austenite constituents form in the overcritical temperature regions (over 950°C), too. The dissolution of carbides (particularly cementite) occurs at temperatures much higher than their expected solubility temperature, particularly over a short heating time. The nucleation rate of austenite in ferrite is not very rapid, in spite of the great amount of interfacial area on which nucleation can occur. The surface energies associated with austenite, ferrite, and carbide are not favorable for nucleation. Nucleation occurred at high angle boundaries where the surface energies are more favorable. The rate of austenite formation is controlled by the rate of growth of the austenite grains. The kinetics of austenite transformation in the weld metal are slower compared to the kinetics of austenite transformation in the heat affected zone. The weld metal is very stable and less sensitive to the thermal influence of the subsequent weld passes. The simulation of kinetics of austenite transformation in the weld metal enables the determination optimal of welding parameters, particularly the cooling rate from 800°C to 500°C.     

Effects of oxygen contamination in the argon shielding gas in laser welding of commercially pure titanium thin sheet

This work studied the effects of oxygen contamination in the argon shielding gases on weld microstructures and properties during laser welding of commercially pure titanium thin sheets. The experimental results, mainly analyzed by optical and scanning electron microscopy and mechanical testing, have indicated correlations between weld surface colour, weld microstructure and mechanical properties (strength, ductility, hardness). As the oxygen content increased, the weld surface colour changed from silver, straw to blue while the surface hardness continued to increase. On the other hand, with the increasing of oxygen content, the weld strength increased first and then decreased because the microstructure changed from mainly serrated alpha in welds made with pure argon shielding gas to mainly acicular and platelet alpha. Practical guidelines are also discussed, based on the study, to deal with shielding deficiencies in laser welding of titanium.     

The Influence of Shielding Gas on Notch Toughness of Stainless Steel Weld Metals

The study aims to examine how the notch toughness of stainless steel weld metals are influenced by the shielding gas. The compositions of shielding gas have significant effect on the notch toughness of the stainless steel weld metal using solid wires, but only slight effect while using flux-cored wires. Inclusions and/or delta-ferrite have pronounced effects on the notch toughness of all the deposited metals. Both vermicular and lathy ferrite are observed, and the ferrite content is decreased by increasing the amount of CO₂ in the Ar + CO² mixtures in both group samples.     

电弧喷涂粉芯丝材的研究进展与应用

简述了电弧喷涂粉芯丝材的优点及制作工艺,介绍了电弧喷涂粉芯丝材的发展历程,以及耐磨损、耐腐蚀、耐高温电弧喷涂粉芯丝材的最新研究进展,展望了电弧喷涂粉芯丝材的应用前景,指出了金属陶瓷复合粉芯丝材、非晶态粉芯丝材、纳米粉芯丝材是未来电弧喷涂粉芯丝材的发展方向。     

Influence of Tool Geometry in Friction Stir Welding

In this article we highlight the results of a recent study undertaken to understand the influence of tool geometry on friction stir welding (FSW) of an aluminum alloy with specific reference to microstructural development, defect formation, and mechanical response. The welding trials were made on 4.4 mm thick sheets using tools made of die steel and having different diameters of the shoulder and the pin, and the profile of the pin. Throughout the welding operation, the rotational speed, traverse speed, and tool axial tilt were held constant at 1400 rpm, 80 mm/minute, and 0 degrees, respectively. For a shoulder diameter of 20 mm and a pin diameter of 6 mm, the severity of defects in the weld was found to be the least and the resultant tensile strength of the weld was high. For the welds that were made using a tool having a shoulder diameter of 10 mm and a pin diameter of 3 mm the tensile strength of the weld was the least since the degree of defects observed were higher.     

C和W对低合金Cr-Mo钢焊缝金属组织和冲击韧性的影响

使用OM、SEM、EPMA、EBSD等手段并进行热膨胀和冲击等实验,研究了C和W元素对第四代钠冷快堆用低合金Cr-Mo钢钨极氩弧焊(TIG)熔敷金属微观组织和冲击韧性的影响.结果 表明:多道次焊接热循环使多层多道焊缝金属的组织分布不均匀,分为表层焊缝组织和中间焊缝组织.表层焊缝组织,可分为熔化区(MZ)、粗晶区(CGH...     

Effect of TiO2-containing fluxes on the mechanical properties and microstructure in submerged-arc weld steels

This work presents a study of the effect of TiO₂ additions in fluxes on the mechanical properties and microstructure of the weld metal formed during Submerged-Arc Welding (SAW) of ASTM A-36 steel plates. Four fluxes with about 9, 12, 15 and 18% Ti were used with a low-carbon electrode. The welding conditions were kept constant. The microstructure of the weld metal for each flux consisted mainly of equiaxed ferrite and acicular ferrite. The increase in the percentage of acicular ferrite and a decrease in its length were observed with an increase in titanium content. The increase in titanium content in fluxes also improved the toughness and ductility of the welds.     

Mixed mode I/II fracture of 2024-T3 friction stir welds

For the first time, a series of mixed mode I/II fracture experiments have been performed on both base material and three families of friction stir welds (FSWs) in 6.4 mm thick, 2024-T351 aluminum plate; the FSW joints are designated hot, medium and cold due to the level of nominal weld energy input per unit weld length (specific weld energy) during the joining process.Results from the fracture tests indicate that the measured critical crack opening displacement (COD) at a fixed distance behind the crack tip properly correlates both load-crack extension response and microstructural fracture surface features for both the base metal and all FSWs, providing measure of a quantitative fracture toughness. The COD values also indicate that transition from mode I to mode II dominant crack growth occurs at lower loading angles for FSW joints having higher specific weld energy input, with a truly mixed mode I/II COD measured during crack growth in the medium FSW joint. Using results from recent detailed FSW metallographic studies, specific features in the fracture process are correlated to the FSW microstructure. Finally, the observed ductile crack growth path in all three welds tends to exit the under-matched FSW weld region as the far-field applied shear loading is increased, with the medium FSW being the only case where the flaw remained within the FSW region for all combinations of shear and tensile loading.     

Fracture toughness and fatigue crack growth in Ti‐6Al‐4V friction stir welds

Friction stir welding of titanium holds the promise for producing joints with microstructures and mechanical properties that are more comparable to wrought material than traditional fusion welding processes. Extensive data exist on the microstructure and static mechanical properties of titanium friction stir welds, but very little are available on the durability (fatigue) and even less on the damage tolerance (fracture toughness and fatigue crack growth). This paper presents the results of an investigation into the damage tolerance of friction stir welds made in 6 mm thick Ti‐6Al‐4V after a post‐weld heat treatment. It was found that the apparent fracture toughness was lower than the wrought base material, 7–25% depending on the crack orientation relative to the weld, but the crack growth performance (ΔK vs. da/dN) of the weld in the absence of weld‐induced residual stresses was identical to the base material.     

Nd:YAG激光焊接对铝锂合金组织和织构的影响

采用Nd:YAG激光进行了5A90铝锂合金薄板的对焊实验,借助光学显微镜、扫描电镜及EDS能谱、背散射衍射技术测试了焊缝的显微组织、合金元素分布及焊缝中的微观织构,并与母材进行了比较。结果表明:Nd:YAG激光焊接使5A90铝锂合金的微观组织和微观织构发生了很大的变化。焊缝区呈现出大量的等轴枝晶组织,这是由于焊缝中存在较多的异质形核点和较高的成分过冷度。焊缝中织构呈随机分布的状态,激光焊接完全改变了母材面心立方金属的冷轧织构组织。