Welding or Brazing for grey cast iron ??

doxford jim · Jun 2, 2011

Hi Guys,

I am interested in your input for repairing what appears to be a grey cast iron casting.

It is part of my steering and has broken and needs to be either replaced or repaired successfully.

Being it is cast, pre and post heat treatment I understand, is needed - to be able to weld it successfully. Also the correct welding rods would be required.

Another alternative would be brazing as it can permeate through the fractured area and once solid, offers a good bond. I have seen cast iron successfully brazed and last for years.

What would you do to repair this component and why.

Any info would be appreciated.

Thanks in advance.

Jim

slowzuki · Jun 2, 2011

I would think that would not hold up if brazed.

I would be skeptical of it holding if welded. I've welded cast in the past via pre-heating, high nickle rod, peening while post heating over a 20 min cool down period. Its really tricky, and when its a good penetrating weld with preheat, the cast flows like crazy.

You can't let it "freeze" and build up layers because they will just crack off the edges of the cast. If you don't drive at high speeds, I'd let her rip, worst case you ruin the part, which it already appears to be junk.

There are lots of fab shops that could build this part for you out of steel or cromoly if needed. Check out places that make Dana 60 steering arms for the off-roading community.

In BC Breeze Industries is one shop I know that also does general machining.

Shield Arc · Jun 2, 2011

I' am so glad I saved this, saves a lot of typing

Most of this was taken right out of Lincoln's book "Metals and How to Weld Them".

First off there are six different types of cast iron so you need to know the type of cast iron you are dealing with. Manifolds and cylinder heads are Gray cast iron. If preheating can be used, the preheat temperature for shielded arc welding (stick) should be held between 500-degrees and 1200-degrees. When oxyacetylene welding you should preheat between 900-degrees and 1200-degrees. You should never let the object being repaired get over 1450-degrees. Make your repairs, then place the object in your kitchen oven, (if it will fit) at 500-degrees for 24-hours. I would purchase the proper temp sticks from your local welding supply.

Nickel 99 can be cut, drilled, milled, and ground. Ni-55 can be ground. The low nickel rod can't be even ground.

Other suggestions:

Ni-44 for Tig rod

Certanium 889, (stick)

Crown Alloys 255 (stick)

Lincoln Softweld 55 (stick)

Harris / Welco 65 (stick)

Ni-55 (stick)

Shield Arc · Jun 2, 2011

Here's one I saved of a guy who has good luck with Mig.

I do a lot of cast iron repairs with 100% success so far. Last year, after several months of research, I found information on a couple websites & mostly in an old Lincoln Welding book. The process is called "Cold Welding Cast Iron With MIG". I practiced several weeks on broken cast iron parts & broken/cracked manifolds my bro' gave me to get my technique down pat. It has worked with superb results.

I use MIG, 309/309L .030 wire, 98/2(AR/CO2) @15cfh & generally in the 80A range. You can use any gas with a mix of no more than 5% CO2 (ex:95/5). The 309 wire has a carbon content of .01 & works best. The idea is to keep the temperature cool by running short beads <1" & allowing the joint to cool before continuing. After running the short bead, you can take your glove off & lay your hand on the metal & will feel only warm to the touch. Since your pieces are not large, I would suggest shorter 1/2" beads & allow each weld to cool back to room temp before continuing.