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Welding cast iron manhole covers

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spec

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I have a house on a street of Victorian houses and pretty much all of the original cast iron manhole covers that are on drives have been cracked by the weight of motor vehicles. Luckily, the front manhole on my house in on the lawn and is in tact.

One of the neighbors is into the history of architecture, especially Victorian and Edwardian, and apparently each house builder had his name cast into manhole covers, so this makes the manhole covers worth saving.

So to the question: is it possible/relatively straight forward to weld seven mm thick cast iron. I have MIG and TIG welded mild steel and aluminium but know nothing about cast iron and have never done oxyacetylene welding. Would the manhole cover need to be preheated to avoid further cracks during welding?

To all the welding experts on ETO, any advice would be appreciated.

spec
 
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Les Jones

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Most Helpful Member
Hi spec,
My preferred method would be sifbronze but you would need to find someone with oxy acetylene welding equipment. For the best joint I would grind a champher on both edges until they almost met in a point. For your job I would only grind the underside so the join was not so visible from the top. Many years ago I had to repair the flange on the starter motor of my sisters then boyfriend's (Now husband) Jag. I first repaired one side. (Two bolt hole fixing) Then later the other side broke and I repaired that side as well. The car also had starting problems at the time. I traced the fault to the centrifugal advance mechanism in the distributer. It was stuck in the fully advanced position. On both occasions the starter flange had broken after trying to start the car when the battery was low. The problem was under those conditions when the engine turned over slowly it fired long before TDC and the engine then tried to turn the starter backwards. The sifbronze joints survived better than the original cast iron. I have heard that you can get welding rods for welding cast iron with an normal stick arc welder but I have never tried them. It may be possible to use sifbronze with your TIG welder but the fumes from the flux may contaminate the tungsten tip. I did an internet search for "sifbronze TIG" and found this page so it looks like it would be possible.
Edit, I've just seen Eric's post so it looks like that could be another solution. (I think you would have to use the pure argon from your TIG welder with the stainless steel wire on your MIG.)

Les.
 

camerart

Active Member
Hi S,
When welding cast iron, I think the whole thing should be heated nearly to welding point in a 'dry' sand container, then welded, then allowed to cool slowly, to avoid shock..
C.
 
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spec

Well-Known Member
Most Helpful Member
Hi spec,
My preferred method would be sifbronze but you would need to find someone with oxy acetylene welding equipment. For the best joint I would grind a champher on both edges until they almost met in a point. For your job I would only grind the underside so the join was not so visible from the top. Many years ago I had to repair the flange on the starter motor of my sisters then boyfriend's (Now husband) Jag. I first repaired one side. (Two bolt hole fixing) Then later the other side broke and I repaired that side as well. The car also had starting problems at the time. I traced the fault to the centrifugal advance mechanism in the distributer. It was stuck in the fully advanced position. On both occasions the starter flange had broken after trying to start the car when the battery was low. The problem was under those conditions when the engine turned over slowly it fired long before TDC and the engine then tried to turn the starter backwards. The sifbronze joints survived better than the original cast iron. I have heard that you can get welding rods for welding cast iron with an normal stick arc welder but I have never tried them. It may be possible to use sifbronze with your TIG welder but the fumes from the flux may contaminate the tungsten tip. I did an internet search for "sifbronze TIG" and found this page so it looks like it would be possible.
Edit, I've just seen Eric's post so it looks like that could be another solution. (I think you would have to use the pure argon from your TIG welder with the stainless steel wire on your MIG.)

Les.
Hmm, very informative Les.

I had not thought of SIF bronze.

One of the objectives would be to have the weld totally unobtrusive so that the weld simply did not show.

An additional requirement would be to strengthen the manhole cover underneath so that it did not crack again under the weight of an automobile. I thought of a cruciform of angle or U iron to do the strengthening.

spec
 

spec

Well-Known Member
Most Helpful Member
Hi S,
When welding cast iron, I think the whole thing should be heated nearly to welding point in a 'dry' sand container, then welded, then allowed to cool slowly, to avoid shock.
C.
Yes, I suspected that it may be necessary to heat the cast iron up to a high temperature before welding. A bit of general heat seems to help most welding.

spec
 

Les Jones

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Most Helpful Member
Hi spec,
I think preheating as camerart suggests would be worthwhile. (That was not a problem with a small item like the starter flange as the heat from welding heated the whole item.) I think Eric's suggesion of stainless steel MIG welding would make a less visible joint than sifbronze. I think it would be wise to try to find some scrap cast iron to try the chosen method on before working on the manhole cover. I think it is also wise to try to strengthen it as it was probably not designed to take the weight of a car.

Les.
 

tcmtech

Banned
Most Helpful Member
If they broke from normal vehicle weight the odds are they are made from the typical lowest grade of material possible the foundry who made them could get away with and they won't take to being welded at all. :(

I've worked around cast iron all my life and unfortunately I have to say that ornamental castings tend to be made from the crap the foundry couldn't use for anything else which means they are mostly casting slag and burnt sand mixed with just enough iron to make it stay together which makes them about as weldable as a rock. :mad:

Melt them down and re pouring is about the only thing that works and if you are going to that degree of work just have the new ones cast out of steel.
 

ClydeCrashKop

Well-Known Member
Most Helpful Member
7mm isn't very thick / strong. Maybe epoxy a cast iron or steel disc to the bottom side of it. If you can hide a few screws, they would help. Make sure the disc is small enough to let the cover fit in place.

What diameter is it?
 

spec

Well-Known Member
Most Helpful Member
7mm isn't very thick / strong. Maybe epoxy a cast iron or steel disc to the bottom side of it. If you can hide a few screws, they would help. Make sure the disc is small enough to let the cover fit in place.

What diameter is it?
Rectangle: 17.5" x 23.5", cast around 1878.

My impression was that cast iron, even decent quality, which I think these are, would not be thick enough to support an automobile.Vehicle strength manhole covers, in the UK anyway, are more like 25mm thick.

spec
 

tcmtech

Banned
Most Helpful Member
Rectangle: 17.5" x 23.5", cast around 1878.
Probably won't weld well at all plus the general location specific historical value is worth something to keep it as is.

I would be inclined to go with Clydes idea and epoxy it plus back plate it being if ever needed it can be undone without further damage to the original material.

If you can get it cleaned up to bare rust free metal and get a reasonably flat back to it (grinding if needed) some epoxy like JB weld will do a pretty good job of holding thing together with minimal aesthetic changes to the face side.
 

spec

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Probably won't weld well at all plus the general location specific historical value is worth something to keep it as is.

I would be inclined to go with Clydes idea and epoxy it plus back plate it being if ever needed it can be undone without further damage to the original material.

If you can get it cleaned up to bare rust free metal and get a reasonably flat back to it (grinding if needed) some epoxy like JB weld will do a pretty good job of holding thing together with minimal aesthetic changes to the face side.
Thanks TCM and to Clyde,

Epoxy sounds like a good bet.

By the way the manhole covers are not mine.

spec
 

Uncle Joe

New Member
JB weld is probably the best metallic epoxy available to the general public. I use it all the time for repairs and fabrication, but manhole covers? No way. The repair joint won't handle the weight of person, and even a small automobile is out of the question. In my opinion your best bet is to use an ordinary stick welder to do the job. As was already suggested, do the repair from the blind side (the back). Chamfer the crack about 5 mm deep from the back, so that when the pieces are joined together all that is visible from the top is a hairline crack. Make sure everything is clammped tightly so that warpage is kept to a minimum. When welding cast iron, nickel rods (made just for this purpose) are commonly used. They're tricky to use and take some practice to get used to. The nickel alloy is very soft, so they burn quick and cool very fast. This results in the bead becoming almost invisible through a normal welding hood. All you can see is the puddle, which makes it easy to lose your sense of direction. Long story short, they're pretty difficult to use and require some practice. However, when used properly they work nicely. Also, very important, the v-groove that's recieving the weld MUST be heated and peened to relieve stress. After the chamfer is thoroughly peened it must be heated again to a bright cherry red (not melted!) and then welded immediately while still glowing. Welding cast is difficult and if you want good results it must be done properly. However, when the job is finished and done right it is very gratifying. I've been welding for 40 years and cast is still a challenge. Good luck!
 

spec

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Wow DJ, welcome to ETO,

Thanks for that definitive and well explained post.

It seems like welding the neighbor's cracked manhole covers is a big task one way or another and way beyond the means/skills of a welding hack like me.:)

spec
 

ClydeCrashKop

Well-Known Member
Most Helpful Member
The repair joint won't handle the weight of person, and even a small automobile is out of the question.
I think you missed the part about the backing plate and maybe screws.
 

EvilGenius

Member
Hi Spec
Just thinking outside the box...
There might be a simpler way of preserving the look of the manhole covers.
There are companies out there that would make a cast of the subject in compacted resin and sand and recreate them.
This could be done by the city or neighbors can get together and fund the project in numbers if required.
I saw that on one of the episodes of Dirty Jobs....
Just a thought
EG
 

spec

Well-Known Member
Most Helpful Member
Hi Spec
Just thinking outside the box...
There might be a simpler way of preserving the look of the manhole covers.
There are companies out there that would make a cast of the subject in compacted resin and sand and recreate them.
This could be done by the city or neighbors can get together and fund the project in numbers if required.
I saw that on one of the episodes of Dirty Jobs....
Just a thought
EG
Thinking outside the box is good- I like your idea.

Thanks EG

spec
 

alec_t

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Most Helpful Member
One thing that hasn't been mentioned is that cast iron tends to 'shrink back' (so I'm told) as it melts. This adds to the difficulties of welding the stuff.
 

cowboybob

Well-Known Member
Most Helpful Member
I've used an cast iron crack fix "trick" that I learned from a feller who lived up in a "holler" in Eastern Kentucky. It was for repairing a crack in an engine block wall that was part of the water jacket using an Oxy/acetylene torch, Borax and wire coat hanger(s). It, actually, worked quite well.

Chamfer the crack (as Uncle Joe noted).
Preheat (to almost white glowing) the crack
Sprinkle borax into the crack
Quickly, "Braze" into the crack using the wire coat hanger as the "rod" (as you would a brass rod)
Repeat from "Preheat" above to build up, gradually, the bead and the bond.

It'll be a slow process for what I guess to be a large crack...
 

spec

Well-Known Member
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Once again, thanks for all the advice and information.

Incidentally, all the damaged man hole covers are cracked diagonally in two.

After considering what has been said on this thread, my leaning is now towards the epoxy approach as suggested by CCC in post #9.

I am now pretty sure that the horizontal crack can be hidden with a filler of some type.

By the way, I have rebuilt the front manhole using engineering bricks, and refurbished manhole cover frame and my un-cracked 1878 manhole cover with a hand wire brush and an angle grinder- and pretty fine it all looks too.:cool:

spec
 
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