Thread: Cast repair

While making a frame to add wheels to my belt sander I managed to tip the thing over. Happily I wasn't under it as it is damn heavy. I'm kicking myself because part of the design was to move the wheels out further than the feet as it wasn't very well balanced in the first place, so I should have seen this coming.

So far the damage appears limited to a cheap level, some nasty looks scrapes on one of my 4" angle grinders and the tracking wheel busted off the mounts.

The bottom left mount has been broken since I got the sander.

Its some sort of cast.
Only tried to weld cast once before and that was 30something years ago.
I could likely just drill some more holes be that seems a little rough.
I do have some silicon Bronze mig wire that I believe I could use with my TIG for a repair or is there a better way to go?
I haven't used a stick welder for the best past of 30 years either.

Hello Stu.
I have used Sil Brz to repair cast iron before. A bit weird. Heat the CI to remove an easy carbon. Then wire brush it to the max. Remember you are brazing not welding, just heat the surface till it goes bright then add filler metal. it is really strong.
regards
BC

Hi Stu
If I had to guess I would venture that the cast iron is just grey cast iron.

Silicon bronze mig filler wire might be ok but I think if its small diameter its not going to be easy to get the volume of fill required. Is the SB available as a tig filler rod of appropriate size?

Have you got the broken cast iron piece to braze back on ? If not, you can fab a flange from mild steel and tig braze it back on the box section that has Linishall cast into it.

A possible filler alternate, if you have tig, you could use some Nickel based cast iron electrodes as a Tig based Filler.
You will need to clean most of the the flux off. You need the 55 series as the 100's are not machinable.I have a couple of 55 grade in 10 gauge squirreled away somehere .I'll look tomorrow and if I can find them I can post a couple to you to try out.

Probably the same treatment for the wheel tracking pulley mount but its hard to see as the photo is blurred.
That part needs more disassembly. Certainly practice on something else first.

Grahame

Thank you guys.

I just remembered I do have some other rods but I am not exactly sure what they are or how they are used.
I bought some torches from a place that I believe did cast iron repairs and the guy gave me a hand full of rods.
They are 600mm x 4.5mm, snap like a carrot and "look like" cast iron.
Anyone know what they are?

BC, and hints on weld prep? I'm guessing the cast is about 5mm thick(as I assume it doesn't "flow" into joints well. Which reminds me, I do have silver solder and OXY/ACET, would that be better?

Grahame, One idea I had was (if needed) I could use my dead MIG as a wire feed, although I am getting much better at this hand wire feeding business.

There seems to be a little confusion, the first picture is where the tracking wheel mounts on the sander/linisher(I knew there was another name for them and it was pretty much right there in front of me lol), the missing pieces from the Linishall casting are still under this bolts(not my best pic and the first time I have been unable to solve rotation problems).

Is it possible your rods are along the same line and the ones I mention above?

Hi Stu,
The picture looks very much like cast iron filler rods used with the Oxy Acetylene process.If you have oxy that would be great but needs a flux. The molten pool of the cast iron is quite different to other ferrous metals. It flows like molasses.
I may have some flux I will need to look.

The flame needs to be neutral or slightly oxidising as a carburising flame can make the welded bead very hard indeed through too much carbon. Hardness, contraction and cracking all go together. The linishall box should not give problems stress wise.

Cast iron is already super saturated - so to speak- with carbon, so more carbon from a carburising ( carbon rich) flame is definitely to be avoided.

Your filler rods are nothing like I have which are stick electrodes about 300mm long 3.2 Diam.

I have never used the rods with TIG but extensively with Oxy.

If you intend using the pictured rods with the Tig process I would say the Tig will need to be running hot and require a tungsten diameter as big as you can fit in it.

The preps are 90 degrees inclusive and only half material thickness deep.

Cheers
Grahame

While I was chasing more info on flux I found the following on fusion welding cast iron with Oxy Acetylene.

https://www.yourarticlelibrary.com/m...-diagram/83865

Grahame

Sounds like silicon bronze TIG or silver solder OXY/ACET might be the easiest for a beginner, unlikely to mess with hardness etc or at least less likely to end up with a puddle on the floor

I have a piece of a cast iron table from a scrapped machine, I will have a bit of a play in the next couple of days to see what I am up against. I have an idea I'd like to try, which maybe a little over the top, I'm pretty sure half of it comes from youtube.
Grind a deep weld prep from one side.
Run beads of sil/bronze along that weld prep(sort of like tinning a solder joint, my idea)
Grind sil/bronze until the parts fit together again.
clamp parts together, braze.
grind through to the braze line from the other side.
braze.

Needlessly complicated for the repair I am doing?



And I missed from my last post, thank you for your offer of some rod, I will see how things go.

(Disclaimer -I've never done this myself)

Don't see a need to wet the parts first, and having done so it will probably cause fit up issues as you have noted. The other thing, particularly with a thick part like this is that if you V one side (like that idea) and completely weld it before doing the other side, you may get distortion coming in as the weld contracts. I would suggest prepping the part and put in one or perhaps 2 passes. V the other side and put a pass or two on that. Alternate so the pull from the welds is 'even'.
The pros preheat CI so that heat distortion and cracking is minimised. Could be worth considering if you have a gas camping stove and the part is small as you are putting on a lot of material (=heat)

Michael

Hu Stu
If you go the silicon bronze route with Oxy acetylene its probably the best bet.

A shiny clean finish with a burr or stone prepares surfaces for keying the braze filler.

One of the tricks we used in industry to control disortion, was where bolt holes were present, was to bolt the work down to something rigid.

Re the hardness ; I must emphasise that the flame setting of neutral or or even slightly oxidising flame is the key to avoiding hardness.

If the flame setting is allowed to go into a carburising condition( excess Acetylene ) your chances of a really hard surface are increased vastly increased.

I saw a cylinder head so welded by Oxy Acetylene (with ci filler rods) being so hard it ripped the grinder machine stones to bits.

It can be managed but the setting of the acetylene flame must be observed and controlled.

Carburising is a condition that imparts the excess carbon from unburnt Acetylene gas into the molten cast iron filler.

If you are not sure how to to recognise the OA flame let me know and I'll describe it.

Grahame

Here's a link to a very well regarded U tuber using silicon bronze with O/Acetylene on C.Iron.

https://www.youtube.com/watch?v=ZV6O8LIiW6w

A professional and an excellent all rounder in the various processes he uses, but who is willing to say so when he makes a blue.

Hope it helps

Grahame

Hi Stu.
I strongly advise against trying cast iron fusion welding in this case. The amount of heat you need is HUGE. The entire casting needs to be red - and kept that way, with the welding face(s) white hot. That will make it really difficult to prevent the original part from running away from you in the thickness you have in that foot. As Greame said, the filler flows like molasses - I described it as "toothpaste" when I did it. You really have to push it into the "puddle". What you have shown in you photo are cast proper iron filler rods. They have additional ferro-silicone in the alloy to make it fluid, so a strip of normal grey cast iron is even more difficult to use.
I fusion welded a vice successfully, but I was very glad that TAFE paid for the oxy acetylene gas I used! I think I described and photographed the project here somewhere.
I strongly suggest you use silicon bronze and your TIG or MIG to replace the broken part and join the cracked piece instead. It is quite easy, relatively, and not very runny either. You wet the CI surfaces as you go, not before you start rebuilding the missing bit. DO heat the casting to a few hundred degrees with an oxy torch, if it doesn't wet immediately. And make sure the TIG doesn't melt the cast iron - easily done!
The result will be easy to machine and as strong as needed.
I wouldn't try silver soldering. Too expensive and too fiddly in the breaks in the photos.

Hi Michael,
I have a 2" "weed burner" for preheat. So far the wetting seems to be off the table.

Hi Grahame,
I'm all good on the "non carbonising flame"
Still watching the video you linked to.


I had a play with the TIG today before I saw these posts using both sil/bronze and the mystery rod. No flux.
So parts worked better than others. I see what you mean about Molasses!! it does not like to flow(but then flux might have helped there lol)
As predicted I did manage to get some glass hard areas.(preheating may have helped there)
Wetting seemed tricky.
Had a quick shot with AC TIG and there maybe some improvement there but havent done enough to be sure I'm not kidding myself.

I will have a go with the oxy/acet in the next couple of days.

There is one weld prep issue, much of the break is in a 90 deg corner, looking at the pic I see a crack going around the corner as well. Do I do all the prep from the other side?

Wow I type slow lol

Hi Joe

Originally Posted by jhovel

They have additional ferro-silicone in the alloy to make it fluid,

If those rods a fluid I don't want to try plain gray iron!

Originally Posted by jhovel

I strongly suggest you use silicon bronze and your TIG or MIG

My MIG is dead, best it can do is be used as a wire feeder.

Originally Posted by jhovel

You wet the CI surfaces as you go, not before you start rebuilding the missing bit. DO heat the casting to a few hundred degrees with an oxy torch, if it doesn't wet immediately. And make sure the TIG doesn't melt the cast iron - easily done!

Will try preheating as I was struggling to get the sil/Bronze to to do much without melting the cast.

Still I can't expect to go from no idea to laying nice beads with 60 minutes playing about(half of which way spent with rods that have no chance of working)

Originally Posted by jhovel

I wouldn't try silver soldering. Too expensive and too fiddly in the breaks in the photos.

Damn that was my fall back. It seems you need bigger gaps for silver soldering cast iron V copper pipe.

I recently completed my first CI repair using TIG & silicone bronze and found the process to be pretty clean and simple with a good result.
Thorough clean and a quick pre heat of the immediate area to roughly 300C.
Base 01.jpg Base 02.jpg
Welder set to 38A A/C around 200Hz with balance slightly negative.
Base 03.jpg
First pass was a bit shaky but I got the feel for it by the second pass.
Base 04.jpg Base 05.jpg
Wrap the lot in a fire blanket when done to slow cooling as much as possible.
I found if difficult to avoid a bit of mixing when establishing the puddle but found that keeping the arc over the bronze puddle as much as possible helped for the rest of the pass.
I haven't tried silicone bronze with DC but can't see why it wouldn't work at a pinch.
Cheers,
Greg.

No time today other than a few youtube vids about AC TIG

Hi Greg,

Thanks for the numbers I will give them a try, without preheat I was up at more like 50/60 amps and melting the base metal happened pretty damn quick.
" balance slightly negative" going to have to look that up. Other that two small AC welds on my current machine(and even those were on the factory presets) I've not used an AC machine with adjustments other than amps. Sure looks like its worth a few more tries.
I also may not have been clean enough, I was more "welding steel" clean, and it seems you need to be "welding alum" clean or the sil/bronze doesn't flow well.