Pulse spray gas metal arc welding of advanced high strength S650MC automotive steel

With an increasing demand for safer and greener vehicles, mild steel and high strength steel are being replaced by much stronger advanced high strength steels of thinner gauges. However, the welding process of advanced high strength steels is not developed at the same pace. The performance of these welded automotive structural components depends largely on the external and internal quality of weldment. Gas metal arc welding (GMAW) is one of the most common methods used in the automotive industry to join car body parts of dissimilar high strength steels. It is also recognized for its versatility and speed. In this work, after a review of GMAW process and issues in welding of advanced high strength steels, a welding experiment is carried out with varying heat input by using spray and pulse-spray transfer GMAW method with filler wires of three different strength levels. The experiment results, including macro-microstructure, mechanical properties, and microhardness of weld samples, are investigated in detail. Very good weldability of S650MC is demonstrated through the weld joint efficiency > 90%; no crack in bending of weld joints, or fracture of tensile test sample within weld joint or heat affected zone (HAZ), or softening of the HAZ. Pulse spray is superior because of thinner HAZ width and finer microstructure on account of lower heat input. The impact of filler wire strength on weldability is insignificant. However, high strength filler wire (ER100SG) may be chosen as per standard welding practice of matching strength.

Mechanical Properties of Aluminum 5083 Alloy GMA Welds with Different Magnesium and Manganese Content of Filler Wires

Gas metal arc welding of aluminum 5083 alloys was performed using three new welding wires with different magnesium and manganese contents and compared with commercial aluminum 5183 alloy filler wire. To investigate the effect of magnesium and manganese contents on the mechanical properties of welds, mechanical properties were evaluated through tensile strength, bending, and microhardness tests. In addition, the microstructure and chemical composition were analyzed to compare the differences between each weld. The tensile strengths of welds using aluminum alloy filler wires with a magnesium content of 7.33 wt.% (W1) and 6.38 wt.% (W2), respectively, were similar. The tensile strength and hardness of welds using wires with a similar magnesium content, but a different manganese content of 0.004 wt.% (W2) and 0.46 wt.% (W3), respectively, were higher in the wire with a high manganese content. Through various mechanical and microstructural property analyses, when the magnesium content of the filler wire was 6 wt.% or more, the manganese content, rather than the magnesium content, had a dominant effect on the strengthening of the weld.

Modeling of Melt Flow and Heat Transfer in Stationary Gas Tungsten Arc Welding with Vertical and Tilted Torches

A 3D numerical simulation was conducted to study the transient development of temperature distribution in stationary gas tungsten arc welding with filler wire. Heat transfer to the filler wire and the workpiece was investigated with vertical (90°) and titled (70°) torches. Heat flux, current flux, and gas drag force were calculated from the steady-state simulation of the arc. The temperature in the filler wire was determined at three different time intervals: 0.12 s, 0.24 s, and 0.36 s. The filler wire was assumed not to deform during this short time, and was therefore simulated as solid. The temperature in the workpiece was calculated at the same intervals using heat flux, current flux, gas drag force, Marangoni convection, and buoyancy. It should be noted that heat transfer to the filler wire was faster with the titled torch compared to the vertical torch. Heat flux to the workpiece was asymmetrical with both the vertical and tilted torches when the filler wire was fully inserted into the arc. It was found that the overall trends of temperature contours for both the arc and the workpiece were in good agreement. It was also observed that more heat was transferred to the filler wire with the 70° torch compared with the 90° torch. The melted volume of the filler wire (volume above 1750 °K) was 12 mm3 with the 70° torch, compared to 9.2 mm3 with the 90° torch.