Porosity formation mechanisms in cold metal transfer (CMT) gas metal arc welding (GMAW) of zinc coated steels

Abstract

2016)Porosity formation mechanisms in cold metal transfer (CMT) gas metal arc welding (GMAW) of zinc coated steels, Science and Technology of Welding and Joining, 21:3, 209-215,The porosity formation in cold metal transfer (CMT) gas metal arc welding (GMAW) of zinc coated steel is studied over a wide range of the heat inputs (160-250 J mm 21 ), which shows low porosity in weld bead (,2% of bead area) in low (,250 J mm 21 ) and high (.350 J mm 21 ) heat inputs and maximum at medium (250-350 J mm 21 ) heat inputs. The high speed imaging of weld pool shows that the highest frequency of zinc vapour escapes at high heat inputs compared to other conditions. Numerous experiments show that size and location of pores along with escaping of zinc vapour are the results of competition of viscosity of weld pool against buoyancy and vapour pressure within the time required to reach solidification temperature. Based on this concept, mechanisms involved in porosity formation, growth and escape phenomena are disclosed, which can help select the optimised welding conditions to obtain porosity free welds in CMT-GMAW of zinc coated steels.

A Study on the Effect of Wire Composition on Welding with Gap and Offset in Cold Metal Transfer (CMT) GMAW

“…This is attributed to the porosity formation during zinc evaporation. This issue has been addressed in the authors' previous work 11,17) . The bead cross sections are measured and evaluated according to the acceptance criteria set in Fig.…”

Consideración sobre la soldadura de transferencia de metal frio de AA5754 al acero galvanizado a partir de aspectos mecánicos y microestructurales

“…The necessity for joints between dissimilar materials often arises in functionally complex industrial applications, economic and environmental concerns (Torkamany et al, 2010;Guo et al, 2014;Liu et al, 2015). For instance, the combination of steel with aluminum provides fuel-efficiency by reducing the weight of construction (Miller et al, 2000;Torkamany et al, 2010;Ahsan et al, 2016). One of the major challenges in transportation vehicle manufacturing is the joining of aluminum and steel by conventional fusion welding methods due to the large difference between their physical and chemical properties (Cao et al, 2014a ;Guo et al, 2014;Squires et al, 2015).…”

“…Recently developed cold metal transfer (CMT) welding which is characterized with low heat input and spatter free weld, is recommended for joining dissimilar materials (Yang et al, 2013;Ahsan et al, 2016). In CMT welding, filler wire is withdrawn after short-circuiting and the metal transfer takes place by the detachment of the molten droplet with the aid of the wire movement (Yang et al, 2013;Zhang et al, 2013;Ahsan et al, 2016).…”

“…As is known, numerous steel grades are the major materials of vehicle structures. These steels are mostly coated with zinc to provide galvanic protection (Ahsan et al, 2016). Zhou and Lin (2014) reported that zinc coating provides wettability of aluminum on the steel surface and also some heat can be removed from the system with the help of zinc vaporization.…”

Analysis of Weld Joint of DX51D Steel with AlMg3 Alloy Made by CMT Welding Method

“…However, with the welding method being evaluated, we can encounter some welding problems and defects, e.g. the porosity of the weld metal, Ahsan et al (2016), Cong et al (2015), and the formation of segregation cracks during solidification, Rush et al (2010), Meško et al (2014).…”