Cast Iron Welding

Chuck hub ready to weld
Chuck hub ready to weld
Chuck hub ready to weld
Welding complete -- Back
Chuck hub ready to weld
Welding Complete -- Front
Chuck hub ready to weld
Two bead weld on front
Chuck hub ready to weld
3 beads on back
Chuck hub ready to weld
Softweld NI-99
Chuck hub ready to weld
Close up
Chuck hub ready to weld
Close up of back

I have a fairly extensive section running up to this welding project which is to be found at "Mounting a 30" chuck" in the lathe section, but since this is a unique welding process, or at least as unique as a stick welder can be I've put this section under welding.

In summary I have reworked a cast iron mounting plate for a lathe chuck and put a steel core in it which now must be welded there. This implies welding cast iron to steel. Cast Iron popular for both lathe chucks (historic actually--the trend is toward steel), and even more often used for chuck mounts because of its rigidity, but it is no friend of the welder.

The problem with welding is that it creates a localized hot spot which then shrinks when it cools and pulls away from the cast iron creating a new crack--very frustrating to someone trying to weld up a crack in cast iron.

The general solution for this is temperature management and the use of Nickel rod. the nickel rod is spendy stuff and comes generally in a 55% nickel and 99% nickle formulations. Nickel is a fairly soft metal (but spendy). We used Softweld 99 because that is what we had. While it isn't as strong as the 55 NI, it is also softer and more forgiving.

This is what Lincoln says about them:

"Choosing electrodes for welding cast iron typically comes down to three things: cost, machine-ability, and whether the weld is single or multiple pass.

Softweld 99 Ni (AWS class ENi-CI) is a nominally 99% Nickel electrode. Nickel is expensive, and so, therefore, is this premium electrode. The electrode will deposit welds that are machine-able, an important consideration when the casting is to be machined after welding. Repairs made with Softweld 99 Ni are often single pass welds with high admixture. Even with high admixture, the weld deposit will remain machine-able. It works best on castings with low or medium phosphorous contents.

Softweld 55 Ni (AWS class ENiFe-CI)is a nominally 55% Nickel electrode. The lower Nickel content makes this electrode more economical than Softweld 99 Ni. Weld deposits are usually machine-able, but under conditions of high admixture, the welds can become hard and difficult to machine. It is often used for repairing castings with heavy or thick sections. As compared to Softweld 99 Ni, welds made with 55 Ni are stronger and more ductile, and more tolerant of phosphorous in the casting. It also has a lower coefficient of expansion than 99 Ni, resulting in fewer fusion line cracks.

The theory is that nickel will stretch to accommodate the temperature change rather than breaking the cast iron. When you apply it you immediately follow the welding by aggressive use of your hammer to help it stretch. In this operation we used a air driven piening hammer and in the close up photos you will see 'tracks' from the air gun that actually sank into the Nickel here and there.

The front (flat side) got a 2 bead weld. The core was machined to that it was recessed about 1/4 of an inch to provide an angle corner to weld in. The first bead was applied as much as possible to the cast iron. The second bead joined the first bead to the mild steel core.

We followed the cold welding practices outlined by Lincoln for cast iron welding. We waited for a day of moderate temperatures and no wind----since we have an unheated shed to work in, and prewarmed both pieces of iron on a wood stove until they were completely warm--but not too hot to handle. The pieces being quite heavy were not prone to cooling out quickly. The idea of 'cold welding' is to have them around 100 degrees when working on them. Slowly heating them on a wood stove got them heated all the way through, etc. Welding was done slowly a couple of inches at a time--the entire welding consumed about 2 hours. The work was then covered with a couple heavy t shirts out of the rag bag and it was time to eat lunch. A couple hours later I took some of these photos and all was well A long ways from completely cooled out, but cool enough to handle bare handed so at the moment I think the end is all well.

The front was a fairly deep groove to start with and it got 2 beads on the cast iron side one above the other and then the 3rd bead was added to join the two beads on the cast iron to the mild steel core. While this is an unconventional way to do a 3 bead weld there was a lot of cast iron surface area available and it's the problem child. Though the hub was a decent slip fit into the plate, for additional belt and suspenders attachment we also drilled the plate 3 times and jammed set screws into the 'core'.

- - Updated 12/31/2012
- - Updated 1/03/2010