Basic Tool Design Guidelines for Friction Stir Welding of Aluminum Alloys

Friction Stir Welding (FSW) is a solid-state welding process that has multiple advantages over fusion welding. The design of tools for the FSW process is a factor of interest, considering its fundamental role in obtaining sound welds. There are some commercially available alternatives for FSW tools, but unlike conventional fusion welding consumables, their use is limited to very specific conditions. In this work, equations to act as guidelines in the design process for FSW tools are proposed for the 2XXX, 5XXX, 6XXX, and 7XXX aluminum series and any given thickness to determine: pin length, pin diameter, and shoulder diameter. Over 80 sources and 200 tests were used and detailed to generate these expressions. As a verification approach, successful welds by authors outside the scope of the original review and the tools used were evaluated under this development and used as case studies or verification for the guidelines. Variations between designs made using the guidelines and those reported by other researchers remain under 21%.

Investigation of the influence of electrode manufacturers ‘recipes on the production and chemical composition of welding fume particles

The quality of the welded joint, production and chemical composition of welding fume particles in the MMAW process, in addition to the welding parameters, mostly depend on the quality of the coated electrode. As part of the preliminary experimental research of the optimal technological composition of the electrode coating, from the aspect of minimizing welding fume, an experimental research of one class of electrodes, E 42 4 B 32 H5, EN 499/94, standard production program of three manufacturers of welding consumables. The test was performed to examine the influence of the manufacturer’s recipe on the production and chemical composition of welding fume particles.

Corrosion Behaviour of Unprotected Weldments in Marine Environments

In the absence of protective measures such as paint or cathodic protection systems, steel weldments, immersed in seawater, are expected to corrode freely. This is particularly true for the ice breakers serving the Canadian Coast Guard, where, in the course of operations, paint is scoured from the vessel hulls and cathodic protection systems were not installed. However, the weldments do not corrode uniformly. In some cases, the weld itself corrodes rapidly and requires regular replacement. At the other extreme, the heat-affected zones corrode instead—a potential safety and integrity concern. The morphology of ice breaker weldment corrosion has altered over the last few decades and this has been attributed to changes in welding consumables and processes. The current study is an investigation into the corrosion characteristics of weldments with a particular focus on the compositional differences between weld metal and hull plate steels. A method has been developed for numerically describing the corrosion of weldment regions (plate steel, heat-affected zones, weld cap passes and weld re-heated zones) arising from an accelerated corrosion test. This in turn enabled the development of an equation that predicts weldment corrosion performance based entirely on material composition. This permits selection of welding consumables that are anticipated to give good corrosion performance, avoiding the extremes of rapid weld metal corrosion and preferential heat-affected zone attack.

Laser Beam and Laser-Arc Hybrid Welding of Aluminium Alloys

Aluminium alloys are widely used in many industries due to their high strength-to-weight ratios and resistance to corrosion. Due to their specific thermophysical properties and intricate physical metallurgy, these alloys are challenging to weld. Work-hardened alloys may experience strength loss in heat-affected zones (HAZ). The strength of precipitation-hardened alloys is severely damaged in both HAZ and weld metal due to coarsening or full dissolution. The high thermal conductivity and reflectivity of aluminium causes lower laser beam absorptivity with lower processing efficiency. Weld imperfections such as porosity, humping, and underfills are frequently formed due to the low melting point and density promoting high liquidity with low surface tension. Porosity is the most persistent imperfection and is detrimental for mechanical properties. In this work, extensive review was made on laser beam and laser-arc hybrid welding of aluminium alloys. Solidification cracking, evaporation of alloying elements, porosity and keyhole stability, and other challenges are studied in detail. The current development of laser welding of aluminium alloys is not so mature and new discoveries will be made in the future including the use of newly developed laser systems, welding consumables, welding methods, and approaches.

A Comparative Numerical Analysis on the Effect of Welding Consumables on the Ballistic Resistance of SMAW Joints of Armor Steel

In the present investigation, a comparative study of ballistic impact behavior of Armox 500T (base metal) and its weldments prepared by low hydrogen ferrite (weldment-1) and austenitic stainless steel (weldment-2) consumables against 7.62 AP bullet has been performed with the help of finite element analysis code Abaqus 2017. Further, the result is validated with the experimental results. The experiment has been performed on the base metal, weldment-1, and weldment-2 against 7.62 AP bullet. Further, a two-dimensional explicit model has been developed for given purpose to simulate the bullet penetration at such high strain rate (103 s−1). Both bullet and plate are considered as deformable. Experimental results revealed that the depth of penetration in the base metal, weldment-1, and weldment-2 is 10.93, 13.65, and 15.20 mm respectively. Further computational results revealed that the depth of penetration of base metal, weldment-1, and weldment-2 is 10.11, 12.87, and 14.60 mm, respectively. Furthermore, weldment-1 shows more resistance against 7.62 AP bullet than weldment-2 in experimentation as well as FEA results. The percentage difference between experimental and FEA results are less than 10% which shows the prediction capability of FEA models. A feasibility analysis has been presented for using the welding consumables to weld the Armox 500T plate. Finally, in terms of ballistic resistance, the low hydrogen ferrite consumables are more appropriate than austenitic stainless-steel electrodes.

Effect of boron and manganese on hot crack resistance and toughness for flux cored arc weldments of 550 MPa grade tensile strength

The hot crack resistance and mechanical properties of flux cored arc (FCA) welds were investigated with three kinds of welding consumables having different boron (B) and manganese (Mn) contents for high strength carbon steel. The hot crack resistance measured from self-restraint testing strongly depended on the amount of B in the welding consumable. Welding consumable with higher B contents resulted in longer total crack length and an increased number of cracks. Boron was intensely detected near the grain boundary of the weld centerline by secondary ion mass spectrometry (SIMS) analysis, and precipitated with boron carbide (Fe23(C,B)6), as analyzed by transmission electron microscopy (TEM). This promoted hot crack propagation in the high strength carbon steel welds. However, removing B from the welding consumable decreased the low temperature toughness for root and face weld metal due to the growth of Ferrite Side Plate (FSP) in comparison with welding consumables having more B or Mn contents. The addition of Mn in the weld metal suppressed the formation of FSP and increased the low temperature toughness. Therefore, the minimization of B and the supplement of Mn successfully achieved hot crack resistance and low temperature toughness for high strength carbon steel welds of 550 MPa tensile strength.

Tensile properties of shielded metal arc welded ultrahigh hard armour steel joints

The present generation Armoured Tracked Vehicles (ATVs) are constructed using Rolled homogenized armour (RHA) grade steels closely confirming with AISI 4340 specifications. However, in future Armoured Tracked Vehicles (ATVs), the overall weight of ATVs has to be reduced enormously and hence, the designers have prescribed to employ Ultra High Hard Armour (UHA) steels for the construction. Welding is considered to be one of the important fabrication methods in ATVs construction. However, welding of UHA steels is highly challenging due to higher hardness and higher carbon content. Shielded Metal Arc Welding (SMAW) is among the most widely employed welding process in the construction of ATVs since it is more versatile and cost-effective. Armour grade steels are welded conventionally using Austenitic Stainless Steel (ASS) consumables to eliminate the serious problems of hydrogen induced cracking. Hence, in this investigation, an attempt has been made to study the influence of ASS welding consumables on tensile properties and hardness of UHA steel joints made by SMAW process. UHA steel plates having 15 mm thickness were welded by SMAW process using five different ASS consumables (having different Creq/Nieq ratio). Tensile properties (unnotched and notched) of the welded joints were evaluated. From this investigation, it was observed that the joint welded using ASS consumable (having higher Creq/Nieq ratio) exhibited superior tensile properties as result of the evolution of ferrite phase with vermicular and globular morphology in the austenite matrix at weld metal region.