We find that steel is the commonest construction material so every welder gets trained in steel welding but as per the demand of your job, you may need to learn Aluminium welding as well. The process although is similar but Aluminium welding is little trickier and metal have to be treated differently as the Aluminium have different properties. The metal is utilized by manufacturers due to its desirable characteristics like a light in weight, high strength, corrosion resistance, versatility in extruding & casting and superior recycling capabilities. The Aluminium welding with the Mig compared to steel welding have issues like feed ability, incomplete fusion at the beginning of the process and crater formation at the end of the welding process.
Feed ability: The uninterrupted spooled welding wire supply in Mig welding is a challenge and a practical problem in Aluminium welding as compared to steel welding with Mig. This issue is primarily due to the mechanical properties of the materials. The rigged steel wire can easily be fed over a farther distance while the sot Aluminium deformed or shaved during the operation and need more attention in the selection of the process to avoid irregular wire feeding or burn back.
The spool end must be instilled with brake setting with pressure for the free-wheeling when stopping welding. The metallic inlet and outlet guide, as well as liners for steel welding, is not useful for the Aluminum where nylon is used to prevent abrasion and shaving or the Aluminum wire. The drive rolls developed in U type with a chamfered edge, smooth, aligned with corrective pressure. The contacts tips are made specifically smooth for Aluminium welding where internal bores are sharp to shave the softer Aluminum alloy. The specialized push-pull feeder developed and improve the feeding system of the wire for the free feed ability.
The Hot Start Feature: The thermal conductivity of the Aluminium is six times than the steel which leads on to rapidly losing the heat from the weld area leading to difficulty in starting the weld on this material. The incomplete fusion is the result of this high conductivity of heat. The ay to overcome this problem is to start the weld with a high current for a specified time period before shifting to general welding conditions for the remainder of the welding process. This higher heat input at the beginning of the welding process helps to overcome the sinking of the heat and thus reduce or minimize the chance of incomplete fusion at the weld area.
The Crater Filling: The thermal expansion which is twice of steel and reduction on solidification which is 6% of volume may lead on to distortion and crater formation at weld zone. These craters are very serious defects and every welding technique requires to fill and make crater free welding. If we try to reduce the weld pool size before the arc is fully stopped or extinguished the resultant craters may be of very small size or almost removed and welding can be made free from cracks and craters. The power source are now designed with built in crater fill feature to make the crater free welding a possibility. It terminates the welding in a gradual manner by decreasing the current over a predetermined time period. The user may adjust the favourable termination to avoid the crater formation.