Why not "braze" reinforcements on?, info from the "Welder's Handbook" Options

[SpecialK]

I was re-reading my copy of Welder's Handbook because my practice welds on some scrap were weak as hell when trying to weld 18ga to some 12ga (rosette welds) to beef-up my seatbelt attach points that rusted out. (IMG:style_emoticons/default/headbang.gif) Needed a break (IMG:style_emoticons/default/beer.gif) to do some research and find out what I was doing wrong.

The author, Richard Finch, is big on brazing automotive sheetmetal repairs as opposed to fussion welding (MIG, Arc, etc.), particularly when it involves pre '80 cars that weren't assembled using HSS (High Strength Steel). He says that the high temps involved in fussion welding actually weakens the surrounding metal, where as the lower temps involved in brazing doesn't. You can't braze butt joints like you'd use to attach outer body panels, but the reinforcement kits like Mark's (Engman) inner long stiffener's and Brad's 10ga beasts would actually be much stronger (at the attach points). His example is taking 1" x 5" long strips of .060" mild steel, overlapping the ends by 1" and brazing them together. In a pull-test machine it takes over 3000 lbs. to pull them apart and it's always the base metal that breaks, never the brazed joint. Since lap joints are the preferred joint when brazing, and all of the weld points (holes) on the reinforcements are essentially lap joints, wouldn't it make sense to braze in the stiffeners rather than MIG weld?

Or then there's always the possibility that everyone does braze their stiffeners in, and I'm just assuming they've been MIG'd (IMG:style_emoticons/default/slap.gif)


Kevin

[Brando]

Big Fucking Hammer? I love that test!

In all honesty, the input provided above about brazing is true. When in my industrial metal class in highschool, the welding chain went as such:

Oxyacetlyne -> Brazing -> Stick (Electric) -> MIG -> TIG (stainless) -> TIG (aluminum)

Aluminum was the hardest... stuff melts so damn fast when it's hot...

A properly done MIG or TIG weld will outlast brazing welds. If MIG or TIG welded aircraft parts can withstand the test, undoubtedly they will last on your car if done to the same standard.

For the problems you are having (2 different sized metals)... To melt the thicker metal you will need a higher amperage. As you noticed this burns the thinner metal away quicker. Adjust by increasing your feed speed and moving faster. It is doubtful with different sized metals you will have perfect welds... Although if the thinner metal is fused completely to the thicker metal your job is done. Not much else after that.

Also, avoid using fluxed rod. The slag is from the flux shielding on the rod. When the metal cools it 'bubbles' to the surface with any impurities. If there are no impurities, well, the slag will become deposits in your welds. Using Argon will eliminate this problem.

That's pretty much all i can say... besides practice practice practice... that will be your best friend, as many above have mentioned (IMG:style_emoticons/default/smile.gif)