This past Saturday the Flatland T's held a Cast Iron Welding Day to demonstrate how to weld cast iron with an oxy/acetylene torch and cast iron rod. Here's a few photos of the process.
The special red cast iron flux.
Exhaust manifold with a hole in it.
Filling the hole with a cast iron rod
What it looks like right after the hole is filled. This is during the post weld cool down period...playing the flame over the manifold so it cools down slow.
Weld finished before grinding.
Weld after grinding.
Another part welded...a lever off of an old cutout. This time, used an old cast iron piston ring off of a Model T.
Thanks Verne. Great information.
For how long did you play with the flame during the cool down period? I've heard about others covering welded cast iron parts with hot sand to make it cool real slow. Did you check if the manifold stayed straight after cooling? (I would have clamped it down to something straight and strong to ensure straightness)
cover with powdered lime while red hot will take 2-3 days to cool to touch
I believe the bigger the part, the more you need to worry about pre-heat/post-heat. The flame was played up and down the manifold for about 3 to 5 minutes before & after it was welded. It was off about 1/8" in the middle when we finished. We did not think about checking it prior to welding. I did the one that is on my daughter's 1914 Touring about 5 years ago and did not need to straighten it after welding. It had a hole in almost the same location. A trashcan full of vermiculite (the normal garden variety) has been used in the past to cool the part (engine cylinder off of an early REO). Someone brought a Model A exhaust manifold to weld. It was broken in two between No. 1 & 2 ports. When I have welded cast iron in the past, the part is ground so there is about a 1/4" gap between the parts. What we needed for this Model A manifold was a plate to bolt it to so it would be held in position due to the 1/4" gap. The small bracket shown in the photos was V-d out pretty good and propped in position, but then it wasn't real critical. The old cast iron piston ring used to weld it seemed to be a much better quality "rod" than the cast iron rod that was bought from the welding store. It flowed a lot better.
Verne: Tell about the flux please. Thanks, Dan
I did not provide the flux but all that I have seen is like brazing flux only it is red. I looked on the Internet and found a couple of sites. The first link has flux and the second link shows rod and flux. I believe the fellow that brought the flux said he went down to the local welding supply and bought it but that they had to order it. I would check with the second one and be sure it is for welding cast iron with cast iron rod. Most welding supplies think you are talking about brazing. You kind of have to redirect their attention.