28 replies to this topic

[William Keeling]

Body saw would be useless on a cage. BTW, part of the problem is that welding leaves the metal hard and brittle, and that's just where you're trying to cut. Plasma doesn't care.

mig -- hard brittle
tig -- not hard or brittle

tig is the what to go on a cage -- self normalizing

[Ron Alan]

I have my reasons for not, but thanks.

Like safety

[dstevens]

mig -- hard brittle
tig -- not hard or brittle

tig is the what to go on a cage -- self normalizing

Not necessarily. A bad TIG weld can be brittle and a good MIG weld is not brittle. The effects on the material welded have more to do with material type, thickness, weld type (butt. filet, corner, lap) filler material and the skill of the operator to not only apply good technique but to also be able to properly configure the machine. Filler for general mild steel that would be used in this app for either TIG or MIG is identical in composition but varies in form factor. The strength delta in this app the difference between TIG and MIG is so minute that it's not discernible. This is the same thing they teach at the Lincoln Electric Motorsports Welding School, Hobart Welding School and the college where I'm working on getting my welding cert.

Roll cages are a bit thicker, .095 to .120 and mild steel reacts favorably to either process as long as you have a competent operator. There are other apps when either a TIG or a MIG have a greater advantage though in a cage or chassis app MIG is fine. In fact that's what most commercially available cars use though some are build using TIG for example drag cars under a certain time are required to have 4130 TIG welded cages. Here's a bit I found about rac car welding a while back a couple years after I'd picked up welding again.

There always seems to be controversy about MIG (metal inert gas) versus TIG (tungsten inert gas) welding. According to the welding experts I have conferred with-and I have conferred with many, mostly in the Aerospace industry-the general consensus is the difference in strength is mostly academic. The main points of discussion centered on the material being welded and the complexity of the weld joint. If we focus on steel and the types of joints used in race cars, in a correctly performed weld, the difference between a MIG and a TIG weld is almost nonexistent from a strength perspective. The same can be said for aluminum in a race car context.

Read more: http://www.stockcarr...l#ixzz1dAkreqbI

[William Keeling]

I did not say anything about strenght -- I wrote able brittleness (malleability). Do the the nature of the way the heat is added to the weld (TIG the base metal is heated -- MIG filler is the heat source) only TIG is self normalizing and creates a malleable and machine able weld with out additional normalizing.

But you know more that me as I have not been to welding college.

"Each type of weld has its place on specific components of the race car. Both MIG and TIG have positives and negatives in the fabrication process." from your link

"In the TIG process, the amount of control you have when it comes to heat input and adding filler material is much greater, as the inputs are instant due to TIG welding being a much more manually controlled process." also from your link

check with your college profs about the properties of metals (metallurgy) tensile strength is but one.

[dstevens]

The cert deal is new, I'm doing it so I have something to hang on the wall at the fab shop and because in some cases a certified fab guy reduces motorsport product liability insurance. I learned to weld about 35 years ago then picked it up again about 5 years ago and have done a couple of cars, a few cages, plenty of pit and shop equipment and have been in enough race fab shops to have a good idea of what is going on. Some of the advantages for TIG welding in motorsport (or anyplace) much thinner material, more precise control over the puddle, more cosmetically appealing and able to joint dissimilar or esoteric material. While TIG welding of cages is done, it's much more common to see a MIG welded cage particularly in a commercially produced race car. In this app normalizing is not an issue and the differences are academic. TIG welded cages are fine but the durability of the welds isn't any better and due to the time it takes to TIG makes it more expensive. The beads can look very nice though.

Here is something I think is neat that MIller did in the booth at PRI a couple years ago. Leavitt built a complete chassis on the show floor. They MIG the cage and clips but TIG some of the smaller parts and in a complete build TIG the non ferrous parts as well. I'd like to make it to PRI or IIMS this year but it's not in the cards.

http://www.millerwel...nd-TIG-welding/

[William Keeling]

I have a test for you tig and mig a butt weld then saw down each weld with a new blade then compare the blades -- this thread was talking about cutting our a cage

[dstevens]

I have a test for you tig and mig a butt weld then saw down each weld with a new blade then compare the blades -- this thread was talking about cutting our a cage

I'd love to do a couple of coupons as a test. I'm not sure the sawsall blade test is in the destructive inspection part of the cert... The intake manifold and fuel system are all over the bench right now with fumes of Seafoam, Engine Brite and throttle body cleaner so I'll need to finish that up and clean up a bit soes I don't blow anything up.


new welding cart by Dave Stevens, on Flickr

[dstevens]

I haven't forgotten about your test William. I'm likely to be cleared to work in the shop this afternoon (by at least the doc, maybe not the Mrs... )

I'll post some things about fab I've picked up over the last few years. Some good resources for welding for the beginner are most any of the Finch books. A text that is used in more formal welding classes is Welding Principles and Applications by Jeffus.

[dstevens]

OK, after now a couple of hours doing the test and documenting it, here it is. I'm not doing this to beat anyone down but to show that one process in a given app is not necessarily better than another. It all depends on what you are doing. I'll blog my AWS training in a new section of the blog, which I've put this. I'm not big time fabricator, though I'd like to be one some day. However, there are plenty of folks here that aren't too informed and need to tell what is crap, and what is Shinola. I'd love it if any other experienced fabricators joined in the discussion.

As for the tests I promised William a few weeks back, story and pics at http://roaddog.com/r...esnt-mean-shit/

Dave