Stainless Steel - Car Craft Magazine

Stainless Steel And Aluminum
Stainless steel and aluminum are seeing more use in automotive applications, and they too are welded differently from mild steel. Stainless steel is so named because its high chromium content prevents the formation of iron oxide (rust). When welded, the chromium can react with the carbon in the steel and oxygen present in the atmosphere. The result is called "sugaring," which manifests itself in a scaly, crappy-looking weld. Argon shielding gas will prevent sugaring of the weld bead on the front of the piece, but what about the back? Sugaring can occur on the back of the weld, too, if the penetration was sufficient. As a result, such a weld is structurally unsound and would be prone to cracking or complete failure under high heat or vibration. To avoid this, it is necessary to back-purge the weld-to provide a stream of shielding gas over the back of the joint.

Karl Hoes demonstrates the proper technique for welding stainless tubing. He has sealed both ends of the tube with tape. A hose from the gas regulator provides a stream of argon into the tube, which displaces the atmosphere shielding the back of the weld from contamination.
Karl Hoes demonstrates the proper technique for welding stainless tubing. He has sealed bo

Aluminum is a tricky metal to weld. In its natural state, aluminum is coated with a tough but transparent layer of aluminum oxide. This oxide provides excellent corrosion resistance, but it melts at a higher temperature than pure aluminum. So when welding, the operator must use enough heat to melt the oxide layer, then back off the heat to avoid overheating the aluminum underneath. If using a TIG welder, the machine should be set to run in AC mode. Positive voltage of the AC sine wave will actually clean off the aluminum's oxide layer, while the heat generated during the negative-voltage part of the cycle will melt the aluminum. Again, be sure to use the proper filler rod, compatible with the alloy you're welding, and switch to pure argon gas if using a MIG welder. The 80/20 argon and carbon dioxide mix used for steel will not work when welding aluminum.

Where Do I Sign?
Lincoln offers the Basic Motorsports class 12 times a year, usually around the middle of each month. The course schedule is posted on Lincoln's Web site, and you can register online as well. Sign up early, though-classes are limited to 12 students each and can fill up quickly. It's recommended that you have some welding experience before taking the class. The concentrated nature of this course would likely cause a total novice to get left behind. If you've never welded before, or would just like to spend a week practicing one welding process, Lincoln also offers five-day MIG and TIG classes.

Note the cloudy-looking area surrounding the weld beads on these aluminum plates. This is where the AC positive phase cleaned away the oxide layer-the electrons bombard the surface of the plate, essentially blasting away the oxidation.
Note the cloudy-looking area surrounding the weld beads on these aluminum plates. This is
MIG welding with aluminum used to be a pain. The filler wire is very soft, making it difficult for the machine to push it through the power cable. Innovations like spool guns and push-pull guns remedy that situation by feeding the wire as close to the torch tip as possible. With a spool gun, the wire is mounted in a housing on the torch itself, while a push-pull gun has an extra set of rollers in the torch handle to help pull the wire through the cable.
MIG welding with aluminum used to be a pain. The filler wire is very soft, making it diffi

The cost of the Basic Motorsports Welding class was $655. Factor in airfare, hotel, and "entertainment" expenses, and it's possible to ring up a bill over $1,000. Still, we feel it was a bargain based on the amount of stuff we learned. And learning in a concentrated environment with lots of hands-on time really helps hammer the technique home.

We highly recommend that any car guy have basic welding skills. Whether you take classes from Lincoln, Hobart, or your local community college, you'll be learning an invaluable skill that will pay for itself many times over.