[Hobbytime]

Nice thread on brazing cast iron, but o/a and cast iron in stick form will give you a better color and texture match.Repair on the door
would have been easier with a piece of cast from an old bath tub and done with o/a and put in a brick enclosure with preheat to prevent
the cracks from contraction while cooling.
Brazing is a good repair ,but on many things o/a is a much better repair . Manifolds are much better done with o/a because the temp
change will eventually make the braze pull away from the iron. I think the case boiler cover can be done with the o/a cast iron in the
brick oven with 1200 deg preheat . I do many manifolds for show tractors and they should not show the repair .

below are some photos of the repair of a mianus exhaust manifold from 1920.

Full sequence here ---http://imageevent.com/gmachine/manifoldandcastironrepair/mianusexhmanifold


george

nice repair, what did you use for the replacement outer piece to take the place of the broken pieces? looks like malleable steel not cast iron...

 

[george md]

Repair piece is a piece of a wet sleeve ( cast iron ) from an engine . Use sleeves and pieces of bath tub that is the right shape,
put many pieces of tub in manifolds .

Look at the link to imageevent , there are several hundred photos of some of the odd repairs.

george

 

[bigb]

Well I finally got around to trying brazing on my Baldor 8" bench grinder guard that was cracked in numerous places. Some of the cracks ended up in mounting holes and a couple did not so I drilled those at the end. I filled the holes in afterwords. I did several applications as I had a few low spots and some porosity in a couple places. I preheated the heck out of it each time and slow cooled it in a Tillman welding blanket which kept it warm for hours, I was really surprised. It is now very solid feeling and one area that had a small "loose tooth" chunk is now solid. I still have a few low spots and a couple tiny holes that showed up after taking a flap wheel to it, debating whether to fill them in and smooth it down.

 

[HT2-4956]

Well I finally got around to trying brazing on my Baldor 8" bench grinder guard that was cracked in numerous places. Some of the cracks ended up in mounting holes and a couple did not so I drilled those at the end. I filled the holes in afterwords. I did several applications as I had a few low spots and some porosity in a couple places. I preheated the heck out of it each time and slow cooled it in a Tillman welding blanket which kept it warm for hours, I was really surprised. It is now very solid feeling and one area that had a small "loose tooth" chunk is now solid. I still have a few low spots and a couple tiny holes that showed up after taking a flap wheel to it, debating whether to fill them in and smooth it down.

bigb,

It looks to me like you're not working hot enough. With out being there to watch you it's hard to say for sure but I suspect that you're melting some of the bronze off on to the joint before the cast is really hot enough to wet it out and take it good. So my advice is to get your faying surfaces hotter before melting any bronze off on them. And don't try and put to thick a layer of bronze on at one time, especially on the first pass. On the first pass just put a little bit on and concentrate on getting it wet out good. Then after you get all the faying surfaces coated with a thin layer you can start adding more on the subsequent passes to get your build up.

You are using a carbide burr to cut your grooves right?

 

[bigb]

Yes, I got a new Forney 1/4" carbide ball. After the first pass, when the surfaces are coated, do you still need to use flux for subsequent passes?
I did get it quite hot, I thought. It would just start to show a dull orange color sometimes but that would fade quickly when I would pull the flame away. I was having some trouble with the flame blowing the molten brass around so I kept pulling it away. Another one of my concerns was expanding one section enough to cause more cracking even though I pre-heated the whole thing each time.

 

[HT2-4956]

Yes, I got a new Forney 1/4" carbide ball. After the first pass, when the surfaces are coated, do you still need to use flux for subsequent passes?
I did get it quite hot, I thought. It would just start to show a dull orange color sometimes but that would fade quickly when I would pull the flame away. I was having some trouble with the flame blowing the molten brass around so I kept pulling it away. Another one of my concerns was expanding one section enough to cause more cracking even though I pre-heated the whole thing each time.

bigb,

You don't need as much flux on subsequent passes but I like keeping at least a little bit of flux going into the mix on the theory that it's better to waste a little and have to much than not enough. Are you using pre-coated rods or bare?

As to relating color to temperature....Rog02 posted a color chart in post #39 that'll help you with that. You need to be up in the full Orange temperature range. Since you can't see those colors accurately thru your brazing goggles I occasionally lift mine up so I can get a good peak at where I'm at heat wise. Especially at the very start to help get things going good.

As to the flame blowing your puddle around....if you try and run to big a flame on a small tip the flame velocity goes up and will give you that problem. So use the next bigger size tip and put a smaller (softer) flame on it. I do quite a bit of fiddling about with the flame size on my tip when I'm bronze brazing. Mostly I'm turning it down (in stages) as the heat builds up in the part.

The other thing is that maybe you don't have enough pre-heat on the part. If it would take more than a minute to raise where I'm trying to braze at up to orange I'd probably stop and do some more preheating. Having a good preheat on it also helps with running a smaller (softer, less velocity) flame while putting the bronze on.

As long as you have a good preheat on the whole part heating a small diameter area (inch or so) up to orange so you can get the bronze to wet out and stick good won't cause it to crack. At least I can't recall it ever doing it on any of the things I've done.

As to wrapping your part in a blanket (or burying it in something) so it cools slow....While it certainly won't hurt I never do it. I just let it sit on the table where it is and cool off in still air.

 

[California]

Is that advice applicable to repairing broken cast iron using nickel arc rods?

I have some rods left over from a (successful) repair a while back. I think preheating was the key to getting it right, that time.

Now I need to repair the leg of a patio bench, which will have more stress than the previous project.

The rods are labelled AWS A5.15 ENIFe-Cl. Size 3/32 and I see I wrote '55amps' on the container.

Any comments will be appreciated.

 

[bigb]

bigb,

You don't need as much flux on subsequent passes but I like keeping at least a little bit of flux going into the mix on the theory that it's better to waste a little and have to much than not enough. Are you using pre-coated rods or bare?

As to relating color to temperature....Rog02 posted a color chart in post #39 that'll help you with that. You need to be up in the full Orange temperature range. Since you can't see those colors accurately thru your brazing goggles I occasionally lift mine up so I can get a good peak at where I'm at heat wise. Especially at the very start to help get things going good.

As to the flame blowing your puddle around....if you try and run to big a flame on a small tip the flame velocity goes up and will give you that problem. So use the next bigger size tip and put a smaller (softer) flame on it. I do quite a bit of fiddling about with the flame size on my tip when I'm bronze brazing. Mostly I'm turning it down (in stages) as the heat builds up in the part.

The other thing is that maybe you don't have enough pre-heat on the part. If it would take more than a minute to raise where I'm trying to braze at up to orange I'd probably stop and do some more preheating. Having a good preheat on it also helps with running a smaller (softer, less velocity) flame while putting the bronze on.

As long as you have a good preheat on the whole part heating a small diameter area (inch or so) up to orange so you can get the bronze to wet out and stick good won't cause it to crack. At least I can't recall it ever doing it on any of the things I've done.

As to wrapping your part in a blanket (or burying it in something) so it cools slow....While it certainly won't hurt I never do it. I just let it sit on the table where it is and cool off in still air.

I was using plain brass rods and dipping. I guess it needs to be hotter next time. I have heard about using a bigger tip but there is so much to remember I forgot, I was using a Victor #4 with O2@10 and Acetylene @6-7

 

[HT2-4956]

Is that advice applicable to repairing broken cast iron using nickel arc rods?

I have some rods left over from a (successful) repair a while back. I think preheating was the key to getting it right, that time.

Now I need to repair the leg of a patio bench, which will have more stress than the previous project.

The rods are labelled AWS A5.15 ENIFe-Cl. Size 3/32 and I see I wrote '55amps' on the container.

Any comments will be appreciated.

CA,

I haven't always had the best of luck using that 55 nickel rod to fix cast iron. For the past 30 odd years my go to way of fixing cast iron has been this bronze brazing and as far as I know I haven't had a failure yet.

If you're going to try using it I'd follow the advice given here.

http://philarc.com/products.do?item_id=36550

 

[HT2-4956]

I was using plain brass rods and dipping. I guess it needs to be hotter next time. I have heard about using a bigger tip but there is so much to remember I forgot, I was using a Victor #4 with O2@10 and Acetylene @6-7

bigb,

Do you know which specific "plain brass rod" you've got? I use Harris Low Fuming Bronze #15. It works best at around 1700 (+) F. It's been a while since I've used any but the flux coated stuff so I've always got plenty of molten flux present. The only time that gets to be a problem is down in a deep groove where it can't run off and builds up to deep and starts interfering with the puddle flow. When (and if) that starts to happen I just break the flux off the rod by laying it on the table and tapping it with a hammer to get most of it off so I'm not adding more. On a part like you're fixing I don't see where I'd need to do that though.

A #4 tip sounds way to big to me. I've got one but I mostly use it just for preheating the part. After that I switch down to a smaller size tip (usually a #2) for the actual brazing.

As to the regulator pressures....other than turning the O2 pressure down if I've had it turned up for cutting I don't pay that much attention to where they're set. I just adjust my flame at the torch as needed. I do quite a bit of fiddling around with my flame size as I go to keep things working smoothly. You just have to be sure to keep it adjusted to a neutral flame. I also occasional decided that the tip size I'm using isn't the best one for the situation so I'll stop and quickly change to a different one.

 

[California]

I haven't always had the best of luck using that 55 nickel rod to fix cast iron....If you're going to try using it I'd follow the advice given here.

http://philarc.com/products.do?item_id=36550

Thank you!

Here's the essence of their advice === quote, my bold ===

... [absolutely clean,and grooved]

Generally, small section castings can be welded without preheat, however it is important that the base metal interpass temperature does not rise above the “hand-hot” level. Deposit in short intermittent beads about 25mm to 50mm with frequent interruptions to allow cooling to take place. Fill crater at end of each weld bead. Remove all traces of slag remnants before applying the next bead. Deposit without weaving and hammer pein each weld bead, whilst still hot, to reduce both local stresses and the risk of weld metal cracking. Large castings should be heated slowly and uniformly to a temperature in the range of 100-300ºC (depending upon possible. After welding, the workpiece should be cooled slowly at an even rate, cover with mineral blankets or immerse in warm dry sand, lime or vermiculite.

=== end quote ===

Ok, I'm ready to practice on scrap to get the amperage dialed in, then the real thing.

Their advice also mentions welding common iron to cast iron. Thinking about that, I may add a 'splint' down this cracked bench leg.

Thank you for that reference!

 

[FusionKing]

I love this thread.
I am about the only guy around my area who will mess with this kind of repair.

 

[juiceclone]

Thank you!

Here's the essence of their advice === quote, my bold ===

... [absolutely clean,and grooved]

Generally, small section castings can be welded without preheat, however it is important that the base metal interpass temperature does not rise above the “hand-hot” level. Deposit in short intermittent beads about 25mm to 50mm with frequent interruptions to allow cooling to take place. Fill crater at end of each weld bead. Remove all traces of slag remnants before applying the next bead. Deposit without weaving and hammer pein each weld bead, whilst still hot, to reduce both local stresses and the risk of weld metal cracking. Large castings should be heated slowly and uniformly to a temperature in the range of 100-300ºC (depending upon possible. After welding, the workpiece should be cooled slowly at an even rate, cover with mineral blankets or immerse in warm dry sand, lime or vermiculite.

=== end quote ===

Ok, I'm ready to practice on scrap to get the amperage dialed in, then the real thing.

Their advice also mentions welding common iron to cast iron. Thinking about that, I may add a 'splint' down this cracked bench leg.

Thank you for that reference!

Yeah, I was able to sitck weld a chev eng block clutch pivot mount from another year eng many years ago, using the short weld and let equalize
'process". It was known back then, and it held perfectly with no induced cracks. Just have to keep a mind on temperature.
I think, in most cases, brazing would be better especially if the part was small or could be preheated somewhat.

 

[MinnesotaDave]

Here are 2 quick examples I did on some scrap yesterday to show a student the difference in puddle appearance (before brushing) of AC vs DC on alum.bronze.

Puddle started faster and smaller on DC, but AC looks pretty

He will be practicing to braze a donated broken cast iron bench (in the fall, school ended today). Art class will paint it. Then our shop class will make the wooden seat.

 

[California]

I haven't always had the best of luck using that 55 nickel rod to fix cast iron

If you're going to try using it I'd follow the advice given here.

http://philarc.com/products.do?item_id=36550

Again, thanks for that link. I completed the project today. (Thin cast iron, repair a broken patio-bench leg). With the bead standing proud I think its stronger than original.

As noted at your link:

Clean, beveled both sides.

Avoid overheating. An inch or less of bead then cool to touch.

Tapped with point of slag hammer while hot to distribute stress.

Thoroughly wire brushed between passes to avoid welding over slag.

Success!

 

[milomilo]

Question. I picked up a lot of brazing rod at an auction a year or two ago. All bare rod in unmarked tubes. Some of it is the soft brass I usually use for cast brazing. Some of it is much harder to bend so was thinking it may be bronze rod. Does that sound like a good theory, or maybe the hardness of the rod or maybe it has nothing to do with the rod type?

 

[HT2-4956]

Question. I picked up a lot of brazing rod at an auction a year or two ago. All bare rod in unmarked tubes. Some of it is the soft brass I usually use for cast brazing. Some of it is much harder to bend so was thinking it may be bronze rod. Does that sound like a good theory, or maybe the hardness of the rod or maybe it has nothing to do with the rod type?

milo,

Sounds like a reasonable theory to me. Have you tried brazing with the harder to bend stuff yet? Could just be that one of them is regular LFB and the other is LFB-15. Regular LFB has a runnier puddle and wets out faster while LFB-15 is "thicker" and easier to use for build up.

 

[HT2-4956]

Again, thanks for that link. I completed the project today. (Thin cast iron, repair a broken patio-bench leg). With the bead standing proud I think its stronger than original.

As noted at your link:

Clean, beveled both sides.

Avoid overheating. An inch or less of bead then cool to touch.

Tapped with point of slag hammer while hot to distribute stress.

Thoroughly wire brushed between passes to avoid welding over slag.

Success!

What, no pictures?

 

[HT2-4956]

Here are 2 quick examples I did on some scrap yesterday to show a student the difference in puddle appearance (before brushing) of AC vs DC on alum.bronze.

Puddle started faster and smaller on DC, but AC looks pretty

He will be practicing to braze a donated broken cast iron bench (in the fall, school ended today). Art class will paint it. Then our shop class will make the wooden seat.

View attachment 1687158

View attachment 1687157

Any chance of doing a fillet weld break test on those two samples?

 

[milomilo]

milo,

Sounds like a reasonable theory to me. Have you tried brazing with the harder to bend stuff yet? Could just be that one of them is regular LFB and the other is LFB-15. Regular LFB has a runnier puddle and wets out faster while LFB-15 is "thicker" and easier to use for build up.

I have not tried it yet. Maybe get some time next week.