What is a TIG welder? You may have heard of Heliarc welding. This is the brand name of one of the first welding machines to use the tungsten (T) electrode with an inert (I) gas (G) process. TIG is the generic name for this process.

The tungsten electrode forms the point of the electric arc. It does need to be reshaped on its end occasionally, but it is not consumed in the process.

The inert gas that flows out of the ceramic cup and around the tungsten shields the arc from the atmosphere. This is necessary because the heat generated will allow the metal being welded to burn. By shielding the weld area with an inert gas such as argon, the oxygen in the air is excluded, thus the weld metal cannot burn.

The TIG process produces the purest welds of any form of welding available. Done properly, there are no contaminants in the weld. Occasionally, for some welds, the inert gas is also introduced to the back side of the weld area to keep contamination away from the weld. TIG welds can be of a quality in which an X-ray won't reveal imperfections.

Most all TIG welders have a variable amperage control-excluding the old one I used for years, when I had to stop and crank the wheel around to change the setting. This led to a great deal of difficulty in getting good welds. I strongly recommend you never get a TIG machine without a hand or foot control. The Miller Dynasty 200 DX TIG welder I now have gives me a choice of either a hand or foot control. It merely depends upon which one I choose to plug in.

The foot control seems better when welding at a bench. The movement of your foot doesn't affect the steady movements of your hand while welding. When away from the bench, such as when I'm moving around making chassis welds, the hand control adjusts amperage for easy, slow starts and slow stops. As uncoordinated as I am, the hand control took a few minutes to get used to. However, once I did, I wondered how I ever got along without it.

There have been many advances in the TIG welding machines over the years. My Miller weighs less than 50 pounds and has electronic controls that are very handy. It will do everything my ancient 900-pound TIG machine will do, only better.

Benefits & Features

TIG welding is not unlike using an oxyacetylene torch. In this case, the torch is electric. The "fire" is created by the tungsten tip that creates an electric arc to the work piece. The tungsten should never touch the work piece. When it does, there will be a pfffft. Then you get to stop and grind a fresh surface on the tungsten tip. One feature that sets it apart from the torch is that the "flame" is adjustable with either the hand or the foot while the weld is in process.

With the ground wire hooked up, the argon bottle on, and a welding rod in hand, you are ready to weld. This is one area where the auto-darkening helmet is worth its weight in trophies. With it you can position your hands and just ease on the power. The light comes on and the lens goes dark. Remember, don't touch the tungsten to the work piece. The arc will start without touching. As the power comes up, watch for a molten puddle to appear. When it does, use the controller to adjust the heat. You must have enough heat to keep the puddle molten but not so much that the puddle melts through, leaving a hole in the metal.

Begin feeding the welding rod into this puddle as you move along. Too much rod too fast will cool the puddle, increase the heat, or slow down. Welding is a matter of heat control. The TIG welder works slowly and precisely. You can see what you are doing and change the heat or feed to make good welds.

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

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.

The plasma cutter works in the beginning like an arc welder. An electrical current establishes a concentrated arc, the heat source. As the heat melts the metal, compressed air is injected into it. This "jet stream" blows away the molten metal as the hand-held torch moves along. A single knob adjusts the heat and air settings for various metals and thickness.

Used on autobody sheetmetal, the cut is narrow and clean. The paint is not burned more than 31/432 inch on each side. This same machine will cut a 31/48-inch-thick steel plate. In fact, a plasma cutter will cut any material that conducts electricity, such as aluminum, steel, copper, stainless, or brass. I have used it to cut an aluminum sheet to make an air cleaner and also to make suspension brackets for a street stock. In short, this is a very useful machine.

How To Use It

As with any machine, some skill is necessary. With the Miller Spectrum 375 Cut Mate, very little skill is required.

A plasma cutter requires a source of compressed air and electricity. This one can be used on either 110 volts or 220 volts with the flip of a switch, but 220 is preferable. An air compressor that will keep up with a touch-up-type spray gun is sufficient. Only 4.5 cfm at 60 psi is required.

With the machine plugged into the selected electricity, using somewhat more air than you can blow into a Breathalyzer, turn on the switch. The ground wire must be attached to the work piece like a welder. It will actually work without the ground but not nearly as well. With the torch in hand, hold the tip near vertical and touch it to the metal you want to cut. When you pull the trigger, things happen fast. If you have used an oxyacetylene for a while, you may have a tendency to move too slowly. On body sheetmetal, the torch will cut at a faster speed than you can accurately follow. Thicker metals, of course, require slower travel while cutting.

There are no special needs when cutting aluminum other than to adjust the knob, if necessary. Aluminum has such a rapid heat transfer that more heat may be needed. I cut out a 10-inch circle of 0.095-inch aluminum. Immediately, I picked it up bare-handed on the opposite side from where I finished cutting.

As with anything that throws sparks, eye protection is a necessity. The eye protection need not be the same as TIG welding, so medium dark safety glasses are sufficient.

To begin a cut on a flat surface, angle the torch slightly away from you. This will keep sparks from flying in your direction. As it begins to cut, bring it back to vertical.

Cutting is always easier and cleaner if you can use a guide. A steel bar clamped in place makes a good straight cut guide. I have used things around the shop such as wheel rims for curved or round guides.

Once a part is cut out, it might need a little cleanup on the backside. When the plasma cutter is adjusted properly for the metal and thickness, very little cleanup is needed. Often, just tapping the cut face with a small hammer removes all the slag. This is easier than getting out the grinder.

Conclusions

The TIG process makes quality welds on steel, alloy steel such as 4130, and on aluminum. The TIG machine allows a soft start and soft stop. This prevents heat shock to the metal. Heat shock is detrimental to 4130 alloy welds.

The plasma cutter provides far better control of the cut area than a torch. It cuts any material that conducts electricity. Also, it puts much less heat into the part being cut, greatly reducing warpage.

Again, I can't teach you everything about using a TIG or plasma cutter in this article. My intention has been to introduce you to these tools and demonstrate what they can do. Hands-on experience will further this education. I recommend Welder's Handbook by Richard Finch. This book, available from Speedway Motors, covers all of the above in greater detail.Contact Sleepy at sleepy.gomez@primedia.com.

SOURCE
Miller Electric Manufacturing
Appleton
WI
9-20/-734-9821
millerwelds.com
Speedway Motors
P.O. Box 81906
Lincoln
NE  68501
4-02/-474-4414
  • «
  • |
  • 1
  • |
  • 2
  • |
  • 3
  • |
  • View Full Article