Grant Erwin wrote:
Christopher Tidy wrote:

Don Foreman wrote:

On Mon, 29 Aug 2005 03:59:50 GMT, Ignoramus5361
wrote:

From a person 100% ignorant about welding, I must say that your welds



look extremely nice. I would try cutting your piece with a chop saw
to analyze penetration of the weld. Picture
http://www.mythic-beasts.com/~cdt22/fillet5.jpg

makes me wonder just how deep the penetration really was. Depth of
penetration seems to be important in more than just one human
endeavour!

i




I think that depth of penetration is far less important than it is
often made out to be. What is important is fused area. If you
welded the end of a rod to a block of steel, would you feel
that the fused region should go halfway down the length of the rod to
be sound? (Of course you wouldn't!) Width of well-fused area does
have some correlation with penetration
with single-pass welds, because puddles are not flat.

However, strength does depend on where metal is located relative to
load moments. Penetration could be important in a filet weld if
welded only on one side, to resist bending moment and avoid stress
concentration. You do want weld metal in regions where the
cross-section will be in tension under load, however it gets placed
there. The simple guidline is therefore that significant
penetration is necessary to have a strong weld. But it depends on the
joint design and how the joint will be loaded.



I think the penetration is better than it looks in that end-on photo
because I stopped welding just before I reached the end of the seam
(in the past I've managed to blow ugly holes in the metal at the end
of a seam).

Out of curiousity, which of my fillets do people think would be
stronger? Here are the pictures again:

http://www.mythic-beasts.com/~cdt22/fillet1.jpg
http://www.mythic-beasts.com/~cdt22/fillet2.jpg

The first was made using RoyJ's suggested technique and the second by
dragging the rod. The first is about twice as wide as the second, and
is concave rather than convex. Instinctively I would guess that the
first is stronger because (i) there's more metal in the weld, and (ii)
the radius of curvature is much larger and therefore the stress
concentrations should be less severe. However, the heat affected zone
around the first weld is also larger, which might weaken it. What do
people think? I'd be interested to hear.

Chris


I believe your second weld will be not only stronger, but substantially so.

Is that because the heat affected zone around it is much smaller?

I can't believe you're going to fabricate an enclosure box for a phase
converter. I think the last one I used I paid like $18 for. Of course,
I'm getting ready to make a welding rod oven, and lacking sheet metal
skills entirely, I'll probably weld it up, sigh. You won't see me using
100% welds, though. I'll skip weld it together, then fill the cracks
with Bondo, sand, prime, and paint. Then insulate and line. I seriously
doubt it'll rust.

There are two reasons for fabricating the enclosure. First, I have no
sheet metal working equipment. Second, it needs to support a 240 V -
415 V transformer bolted to the side of it, which weighs 150-200 lbs.

Best wishes,

Chris