welding (was: Tranny woes)

[treed2 at wsu.edu (T. Reed)]

On Thu, 11 Dec 2003, Nate Mellom wrote:

> No worries about the weld failing under torque?
>

I think it's a common misconception that welds fail frequently.

I took a welding class this past summer and the instructor really knew
what he was doing; he was an ARTIST when it came to welds and he had all
the knowledge, equipment, etc. He had years of experience and his own
company was making big money on a variety of special projects he was doing
for various companies and affluent individuals.

Anyway, I had just welded two plates together with Oxy-Acetylene and had
them in a vice and was bending them back and forth trying (unsuccessfully)
to break the weld. He asked me what I was doing and I explained. Then he
told me that -good- welds (like the one I was trying to break) are as
strong as or stronger than the metal around them. In fact the plates I had
in the vice were bending next to the weld, not at it.

I think a lot of random boobs in their garage with $50 welders try to weld
things and utterly fail to make a good weld; succeeding only at joining
the two pieces just enough so that they stay together. Then the "weld"
breaks and they come to the conclusion that welds are weak.

It's important to have the proper current (too little and you will only
succeed at joining the outermost shell), the proper wire feed rate,
shielding gas if you don't use flux-core wire, the proper wire type for
the materials you're joining, AND good weld technique. If any one of
these isn't right, you may get a crappy weld that may or may not hold up.

When you're welding steel (say, spider gears in a differential), assuming
you're using a monstrous machine with enough current, you should be able
to turn the whole cluster of gears in to one solid piece of steel that
will (essentially) never break. It's not like soldering when you're
joining things with an intermediate metal. The filler metal is generally
the same (or damn close) to the materials you're welding together. The
whole area gets molten and joins together in to one piece. Its like the
instructor said when somebody welded something together crooked and was
trying to put an arc on it while pulling it apart: "that's not coming
apart! go use the plasma cutter"

-Toby