[TheForge] Re: Arc welding advice sought

[Mike Spencer]

Frosty wrote:

F> Is this going to be under load or will a failure put ANYBODY at risk?

Lower die insert for the A&O hammer. The insert is a piece of truck
flat/dog-leg helper spring about which I can find noting on the net.
I want to weld a 1/2"x2" m/s tab or ear to it.  The insert will sit on
the existing flat die; the ear will be clamped against the side of the
flat die with robust band and large screw.  [1] The concept is proven
and the insert won't have routine loads that stress the weld.  But
there will always be *some* such loads and this particular piece of
steel has to have a reasonably good and robust attachment to the ear.

> The failures you're experiencing is at the boundary of the HAZ .(Heat
> Affected Zone)

That's exactly what's happening although I didn't know the
terminology. 

> What's happening is the arc is melting the base metal and it's
> cooling too quickly over hardening the molybdenum in the spring
> steel.  Moly is an air hardening metal above a certain %.

Didn't know the metallurgy, either.

Ron wrote:

RC> Larry is right; Did you "V" it, preheat and post heat?  I would
RC> have thought DC reverse polarity with 7018 should work

"V", yes. pre- or post-heat no. So I'll do a test piece with pre and
post heat and slow cooling.  Don't have vermiculite on hand but I can
wrap it in ceramic wool batting.

Then Dan Brewer wrote:

DB> You will need to remove the temper of the material to get a good
DB> weld.  So heat to cherry red and cover with vermiculite until cool
DB> reheat to 400 to 800 deg Weld .  cover with vermiculite until cool
DB> reheat to cherry and quench in oil/ The spring should retain its
DB> hardness.

The oil quench is out, don't have the means to oil quench a ca. 2x3x8
inch chunk.  But if the test with lesser preheat doesn't work, I'll
try running the workpiece up to cherry and cooling slowly before
welding.

F> You might call Lincoln or a spring shop and see what if anything they
F> recommend for welding springs. 

Yeah, I should ask at the spring shop where I got the material.  Of
course, they'd never *think* of repairing such a spring by welding but
maybe somebody there has tried to work with the material.  Odd that I
can't find anything about this kind of spring on the net.  Every time
I visit the spring shop, there's 2 or 3 broken ones in their dumpster
so they must be common articles of trade.

F> My recommendation if you plan on putting ANY load on them is think of
F> something different.

I just hate that thought but it may come to that.  Grumble.  The
spring stock is *just right* in size and shape and this problem didn't
show up until I had a lot of work into it.

Thanks.  I'll report back by 'n' bye.
- Mike


[1] http://home.tallships.ca/mspencer/shop/ao-die-mod.html


-- 
Michael Spencer                  Nova Scotia, Canada       .~. 
                                                           /V\ 
mspencer at tallships.ca                                     /( )\
http://home.tallships.ca/mspencer/                        ^^-^^