Effects of mild steel welding fume particles on pulmonary epithelial inflammation and endothelial activation

Welders have an increased risk for cardiovascular disease (CVD) following exposure to welding fumes. The underlying mechanisms are largely unknown; however, oxidative stress, systemic inflammation, and endothelial dysfunction have been suggested as contributing factors to particle-induced CVD. We investigated effects of mild steel welding fume (MSWF) on three target cell types: macrophages, pulmonary epithelial, and vascular endothelial cells. Cells were exposed to MSWF at nontoxic doses for 6 h/day, for five consecutive days. The expression of 40 genes involved in inflammation, fibrosis, and endothelial activation was analyzed. Moreover, changes in the reactive oxygen species production and migration capacity of cells were assessed. The expression of matrix metallopeptidase 1 ( MMP1) was induced in both epithelial and endothelial cells following repeated exposure to MSWF. Although MMP1 is important in inflammatory responses in vivo, this effect was not concurrent with changes in the inflammatory status, cell proliferation, and migration capacities, nor did it induce oxidative stress in the cells. Thus, repeated exposure with low doses of MSWF was sufficient neither for inducing inflammatory stress in epithelial cells and macrophages nor for endothelial activation, and higher concentrations of MSWF or the nonparticle fraction of MSWF may be critical in causing the increased risk of CVD observed among welders.

Optimization of Mild Steel Welding Process Parameters Using Multivariate Linear Regression

Local welders in Nigeria are prone to poor quality weldment because of their lack of welding technical skills. When these local welders carry out their welding operation, the welded joints are considered to be good enough because the metal materials welded together are seen to be good and satisfactory. In most case, when these welded joints have not fully served their service life, these materials fail due to the poor quality of the weldment. Material quality can easily be assessed by inspecting the microstructure of the weldment. In this wok, mild steel welding process parameters were optimized using multivariate linear regression (MLR). The study involves the determination of the suitable set of conditions for the welding process parameters that would give the optimum weld of mild steel (low carbon steel) using Gas Metal Arc welding (GMAW) technique and obtain a relationship between the three welding process parameters and the ultimate tensile strength and Brinell hardness number. For this reason, an experimental study was carried out using nine samples of the specimen of mild steel. The experimental and predicted results show that arc voltage and gas flow rate affect the ultimate tensile strength and the Brinell hardness number of mild steel. The maximum ultimate tensile strength and Brinell hardness number were obtained at 180A, 15V and 20l/min. It was also observed that the ultimate tensile strength decreases with increases in arc voltage and gas flow rate. But these two parameters tend to have a positive effect on the Brinell hardness number.

Steel Welding with Micro-Jet Injector

The article focuses on mild steel welding and covers the new possibilities of that method. Since 2011 innovate welding technology based on micro-jet cooling just after welding is being checked. Weld metal deposit (WMD) was carried out for standard MIG welding and for new welding method with micro-jet cooling. A very high percentage of acicular ferrite (AF) in WMD was gettable (55-75%) for low alloy welding with micro-jet cooling injector. This beneficial structure (very high amount of AF) is unusual to observe in WMD in other welding methods. This method is very promising mainly due to the significant improvement of weld quality and reduces costs. Furthermore impact toughness and strengths of WMD were carried out. The present paper aims at outlining same of the recent innovations in MIG welding which represent steps ahead to achieve the objectives outlined above.

Mechanical Properties of Dissimilar Welds between Stainless Steel and Mild Steel

Joining of stainless steel type 304 to mild steel was carried out using a gas tungsten arc welding (GTAW). Samples were welded using stainless steel welding electrode: (AWS: E308l-16) and mild steel welding electrode: (AWS: E6013). The mechanical properties of welded joint were investigated by tension test. It was observed that, the yield strength and tensile strength of welded samples using mild steel welding electrode were slightly lower than welded samples using stainless steel welding electrode. All welded samples fractured at mild steel base metal indicated that the regions of stainless steel base metal, fusion zone and heat affected zone are stronger than mild steel base metal.