Developments in the gas metal arc welding process have found a way to produce almost perfect joints in very thin metal. In years past, if gas metal arc welding was to be used to weld heat sensitive metal, short circuiting or dip-arc methods needed to be used. This would require molten droplets at the end of the electrode wire to be short circuited to the work piece multiple times per second. New developments in gas metal arc welding have been perfected to provide the welder with greater control over the arc and heat input to allow for the wire welding of thin or sensitive joints to be performed. This is due primarily to the use of cold metal transfer gas metal arc welding.
Cold metal transfer consists of a short circuit process where droplets detach from the wire in a more productive way. Although this is a beneficial discovery for welders, there are two things that make short circuit gas metal arc welding problematic in certain conditions. The first thing is that a high short circuit current is capable of producing high heat and the second is that the process of opening the short circuit is uncontrolled which produces splatter.
The conventional gas metal arc welding process allows the welding voltage to be measured in order to determine the length of the arc. In the process of cold metal transfer the wire moves toward the metal work piece until the short circuit occurs, this produces an arc length of zero. Once the short is open and the wire draws back at a certain speed and for a specific time; this means that the arc produced depends on the speed and time that was used. In this process the arc isn’t controlled through welding voltage but is mechanically adjusted after each short circuit. If the welding speed or the electrode changes during the welding process, the arc length will stay the same. This control allows for welders to join large gaps in weld joints, which is one of the most common problems when working with thin metals. Previously the high heat that is produced in gas metal arc welding would melt the metal before the gap is closed, in the new process of combining cold metal transfer, the low heat input allows for large gaps in either welding or brazing to be accomplished.
New developments in the world of welding are constantly changing the way certain jobs can be done. As technology continues to grow in the welding area, more and more advancements will be made. This will make working on different types of metals much easier for welders.
Reference: http://www.thefabricator.com/article/arcwelding/welding-thin-with-gmaw
