Welding 4130

I mentioned a while ago that Fab Shop would be publishing an article
about welding 4130 steel, written by a specialist at Hobart. It's in
the current issue:
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It was being edited as I made my exit from the magazine, so it's
missing a couple of things I had wanted to include, and I didn't do
the final edit. But it's still helpful to anyone who wants some expert
advice on welding the stuff. Blaine Guy knows what he's saying.
Reply to
Ed Huntress
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Thanks Ed. Downloaded the whole mag to peruse later...
You should watch Jody's latest youtube video too. Some real world TIG aluminum casting repair. It shows crack detection, prep, filling... lots of nice little tips. Also a few little tidbits in the comments here and there besides "cool!", "you're the best!" ;-)
Tig Welding Cast Aluminum Outboard Jet Pump
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Reply to
Leon Fisk
That's really impressive. I imagine how much practice that must take to get the feel for doing that. That's why we have pros.
Reply to
Ed Huntress
Yeah, he admits that he probably wouldn't do the job if it wasn't for a friend.
Those are the kind of repairs I would like to know about down the road several years...
I welded up a neighbors broken grass shoe earlier this summer for his JD #5 Sickle Mower. It was in two pieces and had already been welded/fixed a long time ago. Cast iron, never tried welding that before. I bought some Forney Noma-Cast rod to try. Nickle rod is just way too expensive for my fooling around abilities...
So far it has held together for at least one mow job. I had my doubts it would even last that long ;-)
Reply to
Leon Fisk
Did you see that butt-welded tube photo in the Fab Shop article? That was a certification piece that my welding instructor welded around 15 years ago.It's normalized 4130 welded with 4130 filler -- the worst-case combination. He's a certified U.S. Air Force airframe welder, and he has to be re-certified every year.
Anyway, looking at it, and thinking about my own welding (in)experience, I thought I could break that with one or two hammer blows. I asked him if I could have it and then I proceeded to beat the crap out of it.
It wouldn't break. Finally, I got a tiny little crack to show up where I had folded it over and smashed it some more.
The whole thing is a series of mysteries. Serious welding instruction these days includes quite a bit of basic metallurgy. I think that's a good thing.
Reply to
Ed Huntress
That was a good weld. You might get the tube to crack doing that to it without any weld area involved...
If you go back through Jody's videos and info he covers a fair amount on metallurgy. For people in the trade and serious about welding it is important, that is for sure.
After watching, reading stuff available on the web today I'm nothing but an amateur welder, if that. I'm best sticking stuff together with a MIG and ER70S solid wire in horizontal position. Nothing special...
Reply to
Leon Fisk
Right. It tells you something about that chrome-moly 4130, too. In the normalized condition, which is how most of the tubing is sold, its strength and hardness are virtually identical to that of DOM 1070. But the 4130 has twice the elongation (25% versus 12%), so it's much more ductile.
Me, too.
Reply to
Ed Huntress
After reading your introduction as Editor and pending exit I remembered listening to this last summer while getting in some exercise:
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Direct download link (~8mb):
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Something like 10 minutes long. It is a good show (TED Radio Hour) from week-to-week but I rarely manage to listen to it...
Reply to
Leon Fisk
Ha! Yeah, I remember that one. I listened to it a long time ago -- maybe you pointed it out. I loved it.
There so much good stuff around to read and watch, like TED. It's really tempting to spend too much time with it, now that I'm not on a schedule.
Reply to
Ed Huntress
A friend and I have had good results welding cast with stainless steel mig wire - using TIG and pre-heating the heck out of it. Have had very good results on cracked exhaust manifolds, as well as cast depth control sector on old John Deere tractor. Several of the repaired parts are over 10 years old in regular use.
Reply to
clare
Clare, thanks for the tip. I'll add it to my welding cast iron notes. Stainless filler rod has around 10% nickel depending on the type. Quite a bit more chromium. I'm sure the nickel is helpful. This is where the metallurgy education would be of use. What does the chromium do, help or hinder the weld...
Reply to
Leon Fisk
No idea if the chromium helps or hinders - I just know it has worked very well for me.
Chromium in cast iron acts as a carbide stabilizer, so I doubt it has any bad effect on the weld when used as an alloy in the filler rod. In cast iron it also reduces free graphite. Again, likely can't hurt
Reply to
clare
I have never welded cast iron, but I've read a lot about it for article research. So this is second-hand info.
In general, austenitic stainless has two virtues for welding other materials: it's ductile, and because it's austenitic, it can absorb a lot of carbon from the base metal (c.i. is loaded with it) without becoming brittle.
This has led a lot of people to use stainless filler for welding c.i. The 309 and 309L grades seem to be preferred. But when experts comment on it, they often say it's something you "can get away with," and it's not as effective or as reliable as high-nickel filler metals made for welding c.i.
Reply to
Ed Huntress
Way back when I was at an airbase that had a Boeing team rebuilding the heat and pressurization system on B-52's and as the system has a lot of stainless ducting there was a half a dozen welders industrially tigging the ducts all day.
One of them came to me and asked if I would machine a head flat if he welded a crack in it and I told him "sure". A couple of days later he brought a 6 cylinder head in with about an inch of tig welding on it. I jigged it up and took a light cut with a fly cutter and when the cutter hit the weld it took the end off the cutter bit.
I tried it with a file and the file just skated over the bead.
I finished the job on the surface grinder but my experience in that case and several afterwards is that welding cast iron with stainless rod can result in diamond hard beads. Whether these beads tend to be brittle enough to matter I have no idea.
Reply to
John B.

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