Weld Repair of Cast Iron

[weldtek]

We have a customer requesting we attempt weld repair of some cracks in a slag crucible. It's cast iron ~ 3" thick. I had PMI done reporting the following, C > 3.50%, P .052, S .062, Mn .066, Si 1.5, Cu .23. I'm thinking we need to pass. Anybody have any thoughts?

 

[metengr]

Hi weldtek;
Are any of these cracks through-wall? I would probably pass on any weld repairs because of the service duty and risk of developing more cracks.

 

[weldtek]

Hello Metengr,
Yes, there are some cracks that are through the entire wall thickness. My thinking is that any attempt to repair a material such as this is likely to be fraught with problems. I've recommended to the owner that we steer clear of this one, but, I may be over ruled.

 

[GBor]

There is a man in Louisiana that runs a cast iron crack repair business. The process was originally patented in the 1940's, I think, but the patent expired and was then renewed by his company. I can't seem to remember the name of it, but he (Tommy Breaux) travels all over the world repairing cast iron pressure vessels. I'm pretty sure it is some type of stitching process...the repair looks like a scar . metengr probably knows far more about it, but I could track down the name of the company if it is of interest to you.

Garland E. Borowski, PE
Borowski Engineering & Analytical Services, Inc.
Lower Alabama SolidWorks Users Group
Magnitude The Finite Element Analysis Magazine for the Engineering Community

 

[metengr]

It is called metal stitching, which is a mechanical repair. However, given the service duty mentioned above, I personally would not use it for this application.

 

[vesselfab]

we just had a large cast iron piece repaired.
it was 24" thick and 24" long weld.
the part was furnace brazed.

I am not sure if this material would meet your temperature requirements, the repair was stronger than the original cast iron, but weld metal may have a melting point lower than what you are doing.

Lock 'n Stitch is the company with their main office in California, but they travel all over the world repairing and welding castion that is not, for one reason or another, not economically of physically able to be shipped

 

[GBor]

Well, here's a good one. I did a search to try to track down the name of the company I mentioned earlier. On one search, Tommy Breaux's name came up. He responded to a thread here on eng-tips, so he's here somewhere.

The name of the company is Engineered Casting Repair Services, Inc./METALOCK Corp.

http://www.casting-repairs.com/services.htm

Tommy's a good guy. Give him a call...he may either be interested in the work if you aren't, or he may be able to give you a good idea on the troubles that you might run in to.

 

[unclesyd]

Not much help but a few ideas.

If worst comes to worst you might try to find someone who still does thermite welding of CI. This was a common way to repair slag transfer cars at one time.

Also depending on the size of you CI vessel you might want to talk to the people who do flood welding.

Also if you could heat/preheat the casting to 1325F you stand an excellent chance that the repair will be successful. This takes someone well versed in the art of welding cast iron.

 

[Ubbe]

First off all – there is always a risk of cracking when welding cast iron.

When preparing the damaged area, use arc gassing in order to obtain a good welding geometry.
This method will prevent carbon from being smeared on the surface and therefore reduce the risk of cracking when weld material is applied.
If it is possible, try to use an elevated work temperature, say 300 degrees Centigrade, during the welding process – followed by at slow cooling rate.
The filler material should be a Nickel-base (from 55% Ni and up).
After each bead, hammer on the weld in order to release tensions.
Repeat until finished.
There might be a different colour in the repaired are.
Do not forget to get customer acceptance in advance and notify machining company about different material data if turning or milling is used.
I have used this method when I worked in European foundries.