The plasma cutter ready to work. The torch is in the foreground. Behind it is the ground c
This lack of weld speed in a TIG unit has both a plus and a minus side. For most stock car cage welding, the TIG is much slower than the more common MIG welder. But the TIG is more precise and can be used so as not to shock the metal when welding. The metal is shocked when an arc welder or MIG welder is employed. For mild steel chassis work, this is OK. Things change when alloy steel such as 4130 chrome-moly is being used. In the welding process, 4130 chrome-moly steels don't like to be shocked, in either heating or cooling modes. When heat-shocked, 4130 can become brittle in the area of the weld. Some years ago, several drivers inadvertently tested heat-shocked welds on their 4130 rollcages. The tests turned out to be quite deadly.
It was for these reasons that until the last few years, most tubular 4130 aircraft frameworks were torch-welded (not brazed, but welded). As TIG welders have become more common, this has changed. TIG is used, as was the torch, because the controller allows a slow start to warm the joint, and at the finish of the weld, it allows the heat to slowly taper off. These are things that can't be done with a MIG or arc welder.
TIG welding also has its place in welding very thin sections of steel tubing such as tubing with a wall thickness of 0.049 or 0.035 inch, etc.
When TIG welding on steel, a filler rod of like material is usually recommended. When welding on 4130 chrome-moly tubing, I have used a mild steel rod many times with no problems. However, I've learned that a 312 stainless steel filler rod might be more appropriate. The stainless alloy rod has more ductility, thus it puts less stress into the weld. Before beginning a 4130 steel tube project, my suggestion would be to consult with a recognized aircraft or Sprint car chassis builder for the proper filler rod for your application.
There is another area in which the TIG welder is the industry standard. That is in the welding of aluminum. Yes, I know you can feed aluminum wire through a MIG welder. If you are in a controlled production environment (clean metal, exact machine settings, and so on) it works. Trying this at home meets with varied results. MIG welds on aluminum tend to have a lot of splatter. They are seldom as strong as the same weld with a TIG welder. The TIG welder's ability to control heat and the speed that it works are ideally suited for aluminum welding.
In welding aluminum, 4043 filler rod is a good choice with a wide variety of aluminum alloys. It works easily and makes a good weld. I have found it to be the best all-around filler rod. The 5000 series of aluminum filler rods such as 5356 will have a greater tensile strength. If you are welding a part that will be anodized, I have found that the 5052 rod usually provides a better, though not perfect, color match after anodizing.
The plasma cutter is in operation. Here the torch is held slightly off the work piece. The
The Plasma Cutter
If ever there were a magic torch, this is it. For years I have wanted one of these machines. I had seen them demonstrated, but it wasn't until I got one in my hand that I really appreciated its capabilities. Try to find a local welding supply company that will allow you to sample one of these units.
Initially plasma cutters were large, expensive, industrial units. Then over the years, the technology filtered down to the home shop level. They are still not cheap, but if you do much fabrication work, they have significant value. The plasma cutter allows you to do precision work that might otherwise have to be done on a bandsaw, ground by hand, or perhaps not done at all.
I showed a friend how it worked and then let him use it. He made a few cuts and said, "What's next?" I wrote my name in chalk on a piece of 12-gauge (about 11/48-inch thick) metal and handed it to him. A few moments later, my name fell out on the floor. (OK, hold the jokes about name dropping.)
The beauty of a plasma cutter is the way in which it concentrates heat. You will notice right away that a fresh cut piece of steel can often be picked up with your bare hand. Don't take my word for it; test to make sure it isn't too hot.