[TheForge] A36 vs 1018

[Paul N]

OK, I've been reading that PDF that Frosty posted a couple weeks ago, 
and I'm about halfway through my first pass at it. (It will likely 
require more than 1 to understand it)
 (It was this one: http://www.feine-klingen.de/PDFs/verhoeven.pdf)  And 
many thanks for posting that. It's just the kind of description I had 
been looking for.

We should probably start "Frosty's Book Club" discussions, as I'm sure 
that there are things I think I understand, but that I've 
mis-interpreted. But that's a different story.

I'm finding the "book" very enlightening, and not horribly difficult to 
read. (Although anything even approaching an hour at a time seems to 
stimulate the auto-nap response) I had taken a metallurgy class in 
college over 30 years ago, but studying to pass a class is totally 
different from studying to LEARN. So while I've been exposed to this 
stuff before, this time is different and enlightening.

OK, now for my real question:

I've occasionally been stymied while trying to forge weld with hot 
rolled A-36 steel, and since it occurred last night while I was 
demonstrating how to make a basket handle (using 6 pcs of 1/4" round 
A36) I thought maybe it's time to ask. I've made dozens of these, so 
it's not exactly a new process for me.

My problem last night was that the person that asked for the demo had a 
pretty hollow (coal) fire, but I thought that I'm finally getting pretty 
good at this, so why not go ahead with it as is. The first weld, with 
all the pieces kind of loose, went off without a hitch. Welded nicely on 
the step of the anvil. But when I went to the other side, which I've 
always found easier as it's more stable, it didn't take. That's not 
really a problem in itself. I've been here plenty of times.

What became an issue is, now even after correcting the fire, I can't get 
it to weld. After about 4 attempts, the ends are now hopelessly 
distorted and difficult to repair and I abandoned my demo in 
frustration. BTW, I was using straight 20-mule team borax as a flux.

So, what happens to the metal? Does it pick up contaminants? Did it 
de-carburize (there was a little sparking, but not what I'd consider 
significant, and even if it did, wouldn't the lower carbon level make it 
easier to weld? )

In the past, when I've had a failure like this with A-36, Usually end up 
cutting back the ends to get a successful weld, so I'm expecting that 
there has been some metallurgical transformation here. So I'm wondering 
if anyone knows what that change might be.

Since I'm feeling a little more knowledgeable now, I've looked at  the 
chemical compositions of 1018 and A-36, and aside from the slightly 
higher carbon content of A-36 (about 0.25% C vs 0.18% C) there isn't all 
that much difference, chemically. Perhaps it's the inherent grain size, 
and with a little annealing the A-36 would behave better?

(Using references from: 
http://www.benjaminsteel.com/Technical%20Data/A-36-properties.htm and 
http://www.geocities.com/haimanaua/htdocs/steels/1018.html )

So, can anyone explain the differences in behavior in A-36 and 1018 when 
it comes to forge welding?

thanks,
**pn