On Thu, 22 Jun 2017 16:11:48 -0500, 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
Stick weld it with your DC welder tack in place with a single weld,
then preheat. "Stitch" it in place, keep it hot, then finish the weld.
Back off the post-heat and let the weld normalize. Should be better
than factory, where it was likely glued together with a MIG.