On Fri, 23 Jun 2017 13:28:52 -0400, Ed Huntress
wrote:

On Fri, 23 Jun 2017 13:16:39 -0400, "Jim Wilkins"
wrote:


"Ed Huntress" wrote in message
. ..
On Fri, 23 Jun 2017 10:49:28 -0400, Tom Gardner
wrote:

On 6/22/2017 5:11 PM, Terry Coombs wrote:

One of the locals brought me a part from his brush hog , it's
the
pivot yoke that carries the rear wheels (I think) . The sleeve
that fits
it to the pivot pin on the body of the machine is worn , and had
broken
the weld on one side , sleeve was split most of the way up .

I'm machining him a sleeve from some 4140-type
(acts/welds/spark
tests/hardens just like 4140 but ...) and I will be welding it to
the
angle iron frame of the yoke . I can either arc weld it with 7018
or
6013 or I can TIG weld it with ER70S2 (or 308 or 309 SS) - my
baby MIG
ain't got the ass for something this heavy . I know they TIG
4130/4140
tube for chassis's , but that's a lot thinner cross section . This
part
will be ~1.250" ID x 4.5" long with about a .625 wall thickness ,
the
original had a 3/16" wall . I don't want to have this thing fail
because
of a HAZ failure ... I'm thinking I might need to preheat (after
tacking
in place) then control cooling to avoid localized hardening .
Thoughts ,
opinions (about the job!) your experiences in the same/similar
situation
welcomed . If you think I'm an idiot for taking this on , keep it
to
yourself ...

--

Snag


I might be tempted to braze it.

Brazing would work. Welding any 4130/40 that thick is going to need
pre-heat and, probably, post-heat.

Here's an article on welding 4130 that we published last year. It
took
me a year to squeeze this article out of the experts. I was
frustrated
for years by the vast amount of bull that's been published about
welding 4130, and I finally got to the right guy at Hobart:

http://magazine.fsmdirect.com/2016/sept/d/#page7

--
Ed Huntress

Thanks. That's similar to advice Finch gave in Performance Welding.

Yeah, but it was Finch that gave me heartburn in one regard. IIRC,
he's one of the guys who said you shouldn't braze 4130 because it
"opens up the grain." This apparently is not true. I have checked this
with numerous experts, including the author of _The Brazing Book_.

Not the only mistake Finch made.

There was another point that turns up in my "Debunking chrome-moly
myths" sidebar, but I can't recall if it came from Finch. I haven't
read Finch's book for years, so it may have been someone else.

BTW, that butt-welded joint in 4130 tube that I beat the crap out of
with a hammer was one of my welding instructor's qualification pieces
for his Air Force airframe certification. It's TIG welded with 4130
filler, which is a worst-case scenario for the welder. They require it
because the Air Force used to heat-treat their complete airframes,
after welding, back when it was used in a lot of military aircraft.