Fixing cast iron part

Clean clean clean

No specific time, but at least 500 degF, but 800 is better.

A relatively short arc. Low amps, stitch areas, then stop and peen the weld to stretch it as it cools. You want to apply the nickel to the surface, NOT mix it with the cast iron. You don't want dissolution into the base metal.

Nickel rods are their own creature.

Slow cooling is critical. like 100 degF per hour.

Burying the part in powdered lime works well, now that vermiculite is banned. (damn you EPA)

Have to see what the structure is.

The 55% nickel rods are more machinable, but the 75% or higher rods are a bit stronger.

3/32" rod for 1/4" or thinner, 1/8" rod for everything heavier.

Something in the 600 - 800 degF range.

Unless it's your state law, vermiculite isn't banned, Ernie. EPA never banned it. It's available from a garden shop near me in NJ.

None of the Libby Mine vermiculite is on the market anymore (it was closed in 1990), and the EPA says that their samples from other parts of the country and from foreign sources do not contain dangerous amounts of asbestos. They've tried to make that point several times over the past 10 or

15 years.

I'd use oxy-acetylene, railroad rod and Ferro-flux. I don't know where you'd find either railroad rod or ferro-flux these days, but I've mended many broken cast iron pieces with gas, railroad rod and ferroflux.

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Have you considered brazing or silver soldering? Any reason that it must be welded?

-- Unka George (George McDuffee) .............................. The past is a foreign country; they do things differently there. L. P. Hartley (1895-1972), British author. The Go-Between, Prologue (1953).

Steve, I had good success welding cast iron parts as follows:

1) Clean the area 2) Bevel the area 3) Preheat with propane torch 4) Use Nickel 99 rod (expensive, have your neighbor buy it for you).

I so welded a bracket for my milling machine, it holds up very well.

I have some Nickel 99 rod from some good luck bulk auction lots. Otherwise it costs $60 per pound at stores. But it is good stuff.

i

You're assuming it is cast iron. Maybe it's cast steel? You better do a spark test to narrow it down. phil

What he SHOULD be considering, is consulting with an attorney.

A technique I have discovered that works VERY well is to preheat to a dull cherry red and then TIG with stainless steel wire. If the part is CLEAN when you start, and you properly "V" out the joint, I have not had a single repair fail.

I've done (or had done) exhaust manifolds, lift quadrant and other John Deere tractor parts, decorative cast, and all kinds of machine parts this way - and it WORKS.

The stainless alloys with the cast making the metal around the joint stronger and less brittle than the original metal, and more ductile - so it doesn't crack as it cools. (don'r quench or quick-cool, obviously)

The method I use and posted works equally well on cast steel or cast iron - pre-heat and tig with stainless wire.

I've done the same thing as you except I use ni-rod 55 instead of stainless. Took stick rod and removed all the coating. Be sure to not allow the tig arc to hit the cast, keep it on the puddle. phil k.

Brazing can work very well on some cast iron parts if you can build up a heavy collar of brass all around the fracture. I repaired a broken lathe control lever, about 3/4" diameter round bar where it fractured, and one of the lathe legs, about a 3" x 3" angle x 1/2" thick at the fracture. Both collars were about an inch long and 3/16 to 1/4 thick. Requires a lot of brazing rod (cheap), room for a collar of extra material with more cross sectional area than the fracture, and the ability to deposit a thick layer of braze, which as I recall took a bit of practice.

Whatever method, preheat must be enough to burn out the oil that cast iron machine parts inevitably absorb. Grind clean then heat to blue works.

OA welding with matching cast iron rod can deliver good results too. I recall someone making a 6 cylinder head with big valves and ports by gas welding 2 sawed off pieces of V8 heads together using rod made by melting and pouring bits of the sawed off head ends into the groove of angle iron. He cleaned up in his drag racing class with it. Hot preheat and really good distortion control technique required.

SNIP

Unless it's a real oddball these folks probably will have a used or new part, for a good price.

parts are usually under a LOT of stress. Unless it's a museum machine or something where only 5 were ever built I would replace the part.

If you are going to repair it I suggest, CLEAN the part well. If it has held oil use an oven to bake the part and drive the oil out of the casting. Then clean it. Then grind a good bevel on both areas of the break. Preheat the part (I use a modified BBQ grill for small parts) You want it at least 500 or so (hotter is better to a point) Now weld it. You can use a stick with nickel rod or if you have TIG use it with nickel filler. Preheat, weld a small section, hammer it some to relieve stress and toss it back on the heat. Continue until the weld is finished. Now let the part cool SLOW, The ideal way would be in a temp controlled oven where you can ramp the temps down slowly. (I have an ancient electric oven I use for this (also gets used for powder coating and plastic forming, as well as the occasional snack...) You could also put a layer of lime or vermiculite or even sand in a metal pot/box/whatever, lay the hot pat in there and cover it over. Then let it cools down.

I'm from the old school, I consider brazing to be easier to get a decent repair on cast iron. The psi strength of regular brazing rod is just slightly higher than cast iron, adding fillets is easy, and the braze material is quite malleable.

Grind out the joint to get clean metal but don't 'V' it out much, the braze will flow in if you have things done right.

Preheat to around 500 degrees: small parts in a standard household oven (not your wife's if you value your life!), larger parts using a big weed burner propane unit. Use some firebrick to contain the heat, let it heat soak to burn out the old oils and such.

O/A or O/Propane, lots of flux, standard brazing rod. Buttering each side works well, then clamp it down and pour in the filler. Cool slowly, the more intricate the part the slower the cooling. You can peen the hot joint to stress relieve.

MHO

It is the part that goes from the tie rod to the front wheel. The piece that pulls and pushes the wheel, and it has a LOT of force put on it.

Steve

"Steve B"

Then it definately is _not_ cast iron! And brazing this will not hold. You must weld it, I'll bet it is high strength cast steel. phil k.

================== "PrecisionmachinisT" appears to be correct when he wrote On Thu, 14 Apr 2011 08:58:34 -0700

Given the potential for product liability if this breaks, the smart thing appears to replace the part rather than attempting a repair, particularly as it has failed once, and ==>the part should be stronger than new for a good repair.

If it is the drag link itself it is a forged steel part. If it is the sector link (part that attaches to the steering box and moves like a lever) Then it is cast steel. About the only cast iron in the steering would be the steering box, the front axle and hubs and the bolster.

Being this is the drag link then I would suggest welding it, BUT first find a section of steel tubing that will fit over it. Then weld it up good and grind it so the steel tube can slide over the repair. Then weld the tube in place on both ends.

Before welding a fractured part it is always a good idea to find out why it failed. If the part is well within its normal service life expectancy and failed due to a one-time severe overload from something like driving into a tree, then it might be worth welding, especially if the replacement is expensive or hard to get. On the other hand if the part was well into its normal service life and failed in normal service then it has likely suffered metal fatigue damage in all stressed areas, which welding cannot fix, and the welded part will most likely soon fail somewhere else. In this case a weld repair should be considered a temporary emergency fix while waiting on a replacement.

Glen