Welding Repair,... Cast Iron?

[royesses]

I used silicon bronze on the pivot arm on my 4x6 bandsaw. I had leaned over the saw to get a drop off piece and put too much weight on it. That was 3 years ago and it is not going to break. I just tig bronzed it and also the bandsaw vice nut which was broken in 3 places. Both have held up very well. You might need to pre heat that large piece first. Clean and vee it.

Roy

 

[pontiac428]

But then I'd need to buy the special silicon bronze rod right?

Don't worry, it's cheap as far as that stuff goes. It's useful for many repair processes, so you might even find it at your local hardware store.


Edit:
Preheat the part by building a brick "oven" around it to contain the heat. This will also slow cooling after, so win!

 

[westerner]

Good stuff! I have a very small bit of experience, and alot of time listening to my uncle, he of MUCH experience. Good advice given above! The experience I have is on thicker material, (1/4 to maybe 5/16). Part weighed 8-10 lbs total. I used an AC stick welder with high nickel rod. You will not see penetration like 6011. You will want to hold a longer arc, and sorta spray the molten rod. Lots of preheat (oxy/acet rosebud), stress relief, and a very slow cool. Stress relief consisted of a pneumatic needle scaler, applied IMMEDIATELY after stopping the weld, and don't be gentle. Slow cool was "bury the piece in woodstove ashes for a day", immediately after the welding was done. The parts/jobs/projects were- 2 different transmission/transfer case adapters, for 70's vintage domestic 4wd vehicles. Both jobs resulted in parts that did not crack, did not leak, and are still in service more than a decade later.

 

[Robo_Pi]

This tube I'll be brazing on is 1/2" thick.

Here's a better view from the back end.

You can see the crack at the bottom of the rectangular slot heading off to the right. It goes exactly half way around. So this jaw is being held on by a half-circle of 1/2" thick casting. That's why it didn't break off entirely I guess. It's a pretty heavy duty vice. I think it's still worth trying to rebuild. But yeah I'll be able to grind a really deep vee-groove in this. There's a lot of material there to braze to.

Don't worry, it's cheap as far as that stuff goes. It's useful for many repair processes, so you might even find it at your local hardware store.

I'll look around and see what I can find. I'll probably need to order some. I live in a rural area where there aren't too many decent hardware stores around anymore. There used to be, but they all closed up. Sadly.

I would like to try to TIG braze this just for the learning experience. But we'll see how it goes. If I get in the mood to braze before I get the proper TIG rods I might just braze it up with gas.

Preheat the part by building a brick "oven" around it to contain the heat. This will also slow cooling after, so win!

I actually have a blacksmith forge. I wouldn't heat it up too much. But I could certainly warm it up in there quick enough.

I also have a couple old propane cooking grills that I use for heating things up. I don't use propane on those anymore, I just burn scrap wood in them when I need to heat something up. They have the nice cast cover that holds the heat in pretty well. Like others have said, you don't need to get it too hot. In fact, the idea is not to overheat it. 300 to 500 degrees F should be plenty.

Not sure when I'll do this welding. I'll grind the vee-groove first. I do projects around here a little bit at a time. That's just how I work. I'm usually doing 10 things at once. So I do a little bit on each thing. So it may take this project a week to get completely welded.

 

[cathead]

I would probably vee it out and braze it or possibly see how the casting welds first. Cast iron piston rings broken in half are generally
of good quality and work well for rod in my experience. Rings that break in half are cast iron, if they just bend, they are likely chrome
rings. Several ring halves can be welded together so you don't have to hold on to short pieces. Sometimes, I just don't like going
to town just for a welding rod or two. That's my cheapskate tip of the day.

In any case I would do a preheat and slow cool down..

 

[Cooter Brown]

You can preheat it with a torch but make sure the post heat it and wrap it up in a welding blanket to cool slowly.... I have trouble with Cast Iron TIG brazing, I would use Low fuming bronze with stay-silv black flux and an Oxy Torch, Its way easier to screw up when TIG brazing....

This is a repair I just did to my shaper vise with low fuming bronze...

 

[rwm]

Preheat and TIG with silicon bronze. Easy and you'll be glad you did. Let it cool slow.

Whenever I have tried this, I have had some melting of the base metal creating a brittle joint. I played with the welder settings but I could never get it right so the base metal did not melt to some degree. The joint looked fine but failed too easily when tested. I have had much better success with OA gas braising. This creates a consistent strong bond.
If you do go that route, Welding tips and tricks (Jodi) has some videos on this.
Robert

 

[fixit]

http://www.locknstitch.com/index.ht...QSN_wnHSUIKCksYqv3UlK5PDZ2i3WppIaAki1EALw_wcB

I worked for many years repairing & servicing Large air compressors ( up to 2000 hp & as old as 1934) this is the way we repaired cracks the cast parts. It's amazing how well this method will hold broken parts together.

 

[Robo_Pi]

I cut the vee groove today.

I'm not going to weld it today though.

The vee-groove is only about 1/4" wide at the top. I didn't go below the crack. This is 1/2" material. The vee-groove I made is probably only about 1/4 deep. I could do deeper. What do you think? I didn't want to grind clear through and leave a big gap on the bottom where the brass can fall through while molten.




As I got around to the bottom the crack actually disappeared in the bottom of the vee-groove. So it must not have been cracked clearly through on that part of it.




My current plan for welding is to preheat the whole thing to about 400 degrees. I even have an oven thermometer that I can use to assure I'm at that temp.

I've decided to go with the gas torch and the brazing rod I have. My plan is to go over the entire crack first with just a tinning pass, and then go back and fill it with brass.

I might try to get to this tomorrow if possible.

 

[Robo_Pi]

I just noticed a second problem with this vice. I may as well fix that too while I have the thing hot.

Right behind a vice jaw screw the vice is broken:





I figure I can just gouge this out with the grinder and fill it full of brass. Then redrill and tap the hole. All it does is hold the vice jaw in place so it won't have any stress on it.

May as well fix that too while it's hot.