Rules of MIG Welding Technique:
Developing the skills for a good MIG (Metal Inert Gas) weld is of paramount importance particularly for automobile repair technicians. Most of welding repairs done on a car, light truck or van is by MIG welding process. It may therefore be helpful for budding welding operators to understand and follow the rules of MIG welding techniques.
It will be a good idea to first practice on some scrap metal sheet until you gain a reasonable expertise over MIG welding techniques. You will find that many welding fabricators will dispose off waste scrap materials. You may buy a few different metal pieces of varying thicknesses. The ideal thickness for initial practice session could be 1.5mm.
As a first step, you will have to prepare the metal by thoroughly cleaning it to remove all the likely rust and paint. This is necessary because if any contaminants find their way into the weld, it will weaken the weld. Gentle use of any angle grinder or flap wheel should suffice to remove surface rust and paint, and to effectively clean the more inaccessible areas, you may use an air grinder.
Some prefer holding the torch in one hand - though the operation will be lot more comfortable and the torch will also be steadier if you use both hands. It will be worthwhile to dispense with the hand held mask that came with the welder and use instead a full face mask. In fact, you can have a better welding control if you can rest an arm against some solid support.
You should angle the head at maybe 20 degrees to one side so that the weld pool becomes clearly visible. The contact tip should be positioned at about 6mm to 10mm from the metal that is to be welded. Thus, cutting the wire about 10mm long and holding the torch in a way that the wire touches the sheet is a sound way to position a MIG welder.
As a matter of fact, there are a variety of torch movements used in MIG welding. But generally speaking, a zig-zag motion is most common as that will enable the arc to act against both metal sheets to be welded.
It is certainly much easier to lay weld onto a steel sheet than to join, so it may be worthwhile to practice the initial technique that way. Soon a welding a liquid weld pool should develop. If the weld pool becomes unduly big due to slow welding or high power settings, it might result in a hole in the metal. If you weld fairly quickly, the weld will not penetrate through the metal.
As regards welding direction, pushing the torch forward is a better technique rather than pulling it - for the simple reason it improves coverage of shielding gas. However, for thin mild steel that is to be welded horizontally, the direction of welding will hardly make any difference. So if you are able to obtain better visibility with the pull technique, you may as well opt for the same.
Practice as much as possible till such time you succeed in getting neat welds. In fact, it should not take more than a couple of hours practice for you to get a feel for MIG welding.
It is suggested that before trying to weld two pieces of metal, you should initially spend time laying welds on sheet so that you become conversant with welding on different power settings.
The two most common mistakes most beginners make are they hold the hold the torch too far away from the metal that is to be welded and/ or move the torch too fast, You will have to intensely practice for a few hours to avoid these errors and gain expertise in MIG welding.