Rod for cast iron to milt steel repair?

[Fallon]

I recently inherited a coal forge made out of an old brake drum. My brother knocked it over & broke a leg & some other welds attaching a tool holder ring to the drum. He wasn't getting to fixing it any time soon so gave it to me on my recent visit back to Oregon from Colorado (Oregon humidity explaining most of the rust as it's been sitting around a while). Looks like a lack of penetration on the original weld to me, but it's held up for over 25 years until it was knocked over, so decent enough.

I can TIG & DC stick with my Miller Maxstar 200, although not with any particular skill. I seem to be gravitating to stick these days as it's faster & most of my work is dirty or doesn't need to look good. I know cast iron can be problematic to weld due to cracking & usually welds best with a stainless or high nickel rod. Not any particularly high strength requirements, but I don't want it to crack, or end up failing with a pile of burning coal in it. Any recommendations for what easy to find & somewhat economical rod locally or online I should acquire for this? Preferably something that I can store for a while without a rod oven or anything as I'll likely end up with most of a box left over for another project down the road.



Ugg, can fix typos in the post, but not subject.

 

[LD1]

You called it.

Some stainless or nickel rod. Whatever you can find locally.

If you want even stronger....preheat the thing with a torch....then weld....then wrap in a fire blanket, fiberglass insulation, burry in sand, etc. Whatever you can to allow it to cool SLOWLY.

Cast iron cracks because it doesnt expand/contract as much as mild steel. So as the part cools down rapidly....and the steel contracts, it cracks. So cooling slowly and allowing the steel to stretch rather than break. Thats why nickel or stainless rod is preferred because it is alot more ductile and will stretch as the part cools rather than the less ductile rods like you are used to

 

[user.69169]

Theres connections where WELD ain't the best answer, and dis is one of dem.

You got way too much thermal motion in that connection and thermal + motion + weld generally don't make fer a HAPPY house. Original weld on de cast side was fine, but over time and heat cycles and shock the alloy formed welding cast to steel let go of de cast.
Even if you got de metallurgy on the cast its a crapshoot.

Heat is too great for brass even at de expensive silver bearing end of dat alloy. Phosphor Bronze might work, but it ain't gonna stay happy over time. Straight up E70-s6 steel from a MIG using Co2 MIGHT work, or might not as time goes on due to shock loads. 309 SS might work, but next shock might rip brake drum apart too.

Better solution, change de joint to one allowing a flange to be bolted or riveted to de brake drum. Thermal shock goes out of the picture.
BEST solution, make a coking table you drop de forgepan into and pretty much all stresses go away. Gotta coke de coal someplace anyhow.

However you go, DON'T grind de cast. Dat brings nasty contaminants in de CI up and kills purchase especially wid brass or bronze.

 

[stuckmotor]

The smoothest welding rod I ever used was a nickel rod with baby blue flux. That was over forty years ago and I don't know if I even looked at the number on the rod. It welded was like spreading butter with my AC buzz box.

 

[user.69169]

The smoothest welding rod I ever used was a nickel rod with baby blue flux. That was over forty years ago and I don't know if I even looked at the number on the rod. It welded was like spreading butter with my AC buzz box.

Probably Castolin Eutectic "Toolweld" came in a red & yellow plastic container.

 

[ruffdog]

Eutectic 680 rod:

EutecTrode(R) 68 | Castolin Eutectic

 

[yomax4]

I vote 312 Stainless. Or one of it's specialty names like Super Missile Weld, Weldcote Super 120 etc.

 

[stuckmotor]

Eutectic 680 rod:

EutecTrode(R) 68 | Castolin Eutectic

Thanks guys. I bought maybe four from the local welding guru and don't remember about the box. They sure ran smooth.

 

[user.69169]

For de record I'm sticking to the joint is a bad design dat should be changed.

I can see how man who originally built it copied a rivet forge wid slip out legs, but steel tubes welded to cast brake drum is not de same as sleeves cast into de rim of a forgepan when de pan is poured.
Just cause something can be welded don't mean it should be welded.

 

[swines]

If you've already welded this, check the welds regularly. Cast iron changes over time if exposed to high temperatures. The process is called graphitization. The carbon in the cast iron is changed to graphite. Welding requires melting the cast iron and having it mix with the welding rod. The cast iron will not weld properly as the weld material doesn't fully bond to the cast iron because of graphitization. This is not a problem with brazing as the cast iron is not required to melt in order to bond with the brazing material which is why brazing is often used in repairing cast iron. Since this is a forge, the cast iron will be subjected to heating and cooling which may cause the weld to crack as the weld material is not fully mixed into and become part of the cast iron.