ANOTHER reason NOT to weld cast iron

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Hands On

Re: ANOTHER reason NOT to weld cast iron

Post by Hands On »

In reply to Tryp

< Why do major manufacturers make rod that is so damn expensive no hobby welder would buy it? >
Major manufacturers and I'm talking about the rolls royce of cast iron electrodes - EUTECTIC CASTOLIN - DO NOT MANUFACTURE WITH THE HOME MARKET IN MIND - Their products are manufactured with the maintainence market in mind where an hours down time means thousands of dollars of loss. Bear in mind there are many grades and types of cast iron and each requires its own grade of electrode.
Accordingly they will pay several hundred dollars for a packet of electrodes that will sucessfully repair the breakage in the hands of a competent cast iron welding operator.

The operator must be competent in the use of these electrodes -not just experienced in some other type of metal. I worked at Queensland Alumina Limited The largest aluminium refinery and where downtime was rated at $thousands per hour. I could repair cast iron wear and breakages because I understood the material and was experienced.

Cast iron contains up to 4% carbon content . It is a super saturated solution through out the metal. It is carbon affect on cooling which causes cracking.. If you do not understand this and how do deal with it you are continuall domed to failure. Cast iron best works under compression and cant stand much tensile or torsion. In summary the most cost effective and sucessful repair for home welders is oxycaetylene process but this must done with caution as a too carburising flame will give a diamond hard finish.

My 2C worth
Grahame Collins
JHM13
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Re: ANOTHER reason NOT to weld cast iron

Post by JHM13 »

I have an article somewhere concerning a problem that auto racers were having
cracking heads in the valve seat area.Since it was getting difficult to find this particular head, a guy devised a way to fix them.After removing the valves,
He veed and I think end drilled the crack.He then took loose bricks and built a
brick floor and box somewhat bigger then the head.He had the head supported on bricks so the area of work would be easily accessable.He then filled the whole
thing with charcoal briquetes and lit it off.He even had the top of the head covered.
He covered the top with a piece of sheet iron and let it heat for a hour or so .
He got his O/C rig set up and got his cast iron rods ready to go.
He uncovered the head,brushed the ashes&charcoal back and welded it in place.
When done ,he raked the charcoal &ashes back over it,and covered it and ignored it until the next day.They remachined the head and said they were very happy
with the results>
MikeC
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Re: ANOTHER reason NOT to weld cast iron

Post by MikeC »

"It is carbon affect on cooling which causes cracking.. If you do not understand this and how do deal with it you are continuall domed to failure."

Agree with you 100%, hands on. As I said, the reason for this extensive training and availabilty of super expensive electrodes are to allow a broken machine, which very probably CANNOT be repaired ANY OTHER WAY, to be stuck together well enough to get the job done. How do you acetylene weld or braze a 100ton hydraulic press frame that has broken through a thick section? Nearly impossible (especially these days). In this case, electric welding would be about the only option.

"Cast iron best works under compression and cant stand much tensile or torsion."

Yes, agreed again. Unfortunately, somebody forgot to tell those guys who made machine handles, mounting ears, shifter arms, etc... out of cast iron and imposed just such loads on them. When those get broken, you have to have the FULL strength of the original joint or it'll come off in your hand, or break inside the machine. To make matters worse, these are usually very small sections by comparison. Pre-heat is not a problem, it's the cooling that gets you. They cool WAY too fast in most cases (as quick as the torch is removed). Unless you have an oven, it's going to come out brittle nearly every time.

"In summary the most cost effective and sucessful repair for home welders is oxycaetylene process but this must done with caution as a too carburising flame will give a diamond hard finish."

Not only just a carburizing flame, there are plenty of gotchas for welding cast iron, even with a torch. Unless material homogeneity, or color match is required, there are far less pitfalls and problems with brazing. If properly reinforced, the joint will be as strong as, or usually stronger than, the original part before the break. Brazing rods are cheap and there is less gas used due to the lower temps, lower pre-heat and shorter post heat (if any) required.
18x72 L&S, Fosdick 3ft radial, Van Norman 2G bridgemill, Van Norman #12, K. O. Lee T&C grinder, Steptoe-Western 12X universal HS shaper, 16spd benchtop DP, Grob band filer, South Bend 10L
MikeC
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Re: ANOTHER reason NOT to weld cast iron

Post by MikeC »

"A few must haves :

Cherry red heat before and during welding
Cleaned, Well prepared and fluxed welding areas
Trained ,experinced and skilled oxy acetlenewelding operators
Water cooled (shrouded ) oxy aceylene nozzles
Post heat in a bricked in firepit
very slow cooldown rate rate - onetime 4 days"

I like very much that you labelled these MUST HAVES! Not good ideas, not suggestions. Without these conditions the weld will be brittle. White iron will form as the iron hardens with the carbon still in full solution.The extent may vary, but it's going to happen. Most home shops (and most other shops for that matter)cannot maintain all these conditions.

If the part is of any size at all, it's going to take at least two or more guys and torches to maintain the heat, most of us are trying this solo.

The cleaning and fluxing I think we can all pretty much accomplish if we take our time and do it right.

The level of proficiency will be varied GREATLY, especially in the home shop, especially considering those other guys we might try to draft into holding a torch to achieve and maintain that cherry red heat. "Oooops, I didn't know it would melt like that..."

I know I certainly don't have a water cooled torch. Would have loved to a few times lately. Once that tip gets just so hot, it's going to pop back on you no matter what you do. The only cure is to swap tips or quit until it cools down, then you are back to the pre-post heat problems.

I certainly don't have a bricked firepit in my shop yet..... Burying in sand is a substitute, but if that sand is not cherry red hot, too... you just quenched it, especially if the part is small.

Cooling of any sort and at any time during the welding process is most critical. That's where the carbon phases change and where things get VERY hard and brittle, or not. I certainly have no chart on the wall to look up how long to cool a certain part base on section thickness and overall size. Would be nice if there were such a thing.
18x72 L&S, Fosdick 3ft radial, Van Norman 2G bridgemill, Van Norman #12, K. O. Lee T&C grinder, Steptoe-Western 12X universal HS shaper, 16spd benchtop DP, Grob band filer, South Bend 10L
Doug_Edwards
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Re: ANOTHER reason NOT to weld cast iron

Post by Doug_Edwards »

This reply is not for Mike, it is for others who may have the need to weld
cast iron, as it appears from reading Mike's posts, that his mind is made
up as far as the unsuitablilty of welding cast iron.

My experiences are much different than what Mike portrays. I personally
have had good success welding gray iron with nickel rod, as well as have
been around others that have also. I did it by the book considering preheat,
stressreleving, and post heat. Apparently I am not alone, as the gray iron
foundry I use, regularly welds castings on correctable defects.

I will not say I consider it a cure all, as some castings by nature of the
design are poor choices to fix. I suspect that there are also poor pours
of iron that do not lend themselves to much of any kind of repair.

That Mike has not had, or seen success in welding iron, does not mean
that it is not a good idea or cannot be successfully done, even in a home
shop. I will again say that recomended proceedures should be followed for
best results

Regards,

Doug
http://www.precisionlocomotivecastings.com/
Building a 70 ton Willamette in 1.6"
Building a 80 ton Climax in 1.6"

"Aim to improve!"
"Mine is not to question why, mine is just to tool and die"
tryp

Re: ANOTHER reason NOT to weld cast iron

Post by tryp »

I very well understand the reason that they make cast iron rods that no hobby welder could afford. I too work in a chemical plant where downtime means tens of thousands an hour. There they have several boxes of cast rod that as far as I know never gets used, as there are no process items that are made from cast, just 316, hastalloy, 2205 and titanium. So when I need some the welders just grab a box for me.

Out of curiosity I went and checked the hardness of the area surrounding the welds I made in the base of the shaper. It cuts easily with a file and a centerpunch marks it well. Not what I would expect from chilled or white iron. I don't think that the entire item needs to be heated, nor does it need to be cooled over days, I'm sure hours is fine under some type of insulation like vermiculite or ash.
danhill

Re: ANOTHER reason NOT to weld cast iron

Post by danhill »

I have always put welded cast parts into lime. I have a mowing machine part that was brazed 40 years ago still in use.Lime costs little, a wooden box can be built for large parts.Ive used a rod that gives better results than brazing.
Old Jack
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Re: ANOTHER reason NOT to weld cast iron

Post by Old Jack »

@MikeC. I know this a old post but I'm very interested in metal reinforced brazing of cast iron. I have a swing arm from an old metal shaper that has been welded in the past but has failed due to a poor repair. I'm new to the forum and I'm hoping to communicate with you on the subject. I like the idea of brazing and reinforcement and the characteristics of brazing cast IE. cracking, ect. Would like to hear from you if you have the time.There are several questions I'd like to explore regarding brazing a large piece. Thank You
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Harold_V
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Re: ANOTHER reason NOT to weld cast iron

Post by Harold_V »

Old Jack---
Welcome to the board.
Please be advised that MikeC has not made a showing on this venue for 16 years. The chance that you'll hear from him is not good.

H
Wise people talk because they have something to say. Fools talk because they have to say something.
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Re: ANOTHER reason NOT to weld cast iron

Post by liveaboard »

I cut and sectioned a cast iron exhaust manifold, then welded the resulting 7 pieces back together with cast iron welding rod.
This was 30 years ago, and I don't know what the rod was composed of exactly, but it was not nickel.

I tacked the parts together with the flanges bolted to the head, then removed the assembly to fully weld on the bench. I did not preheat.
After cooling there was a lot of warping (as expected) and I had the flanges machined flat again.

It was a new manifold, not shot full of carbon. Also, quite thin material compared to the heavy castings discussed here.
Anyway, the result was very satisfactory, after machining it fit on the engine and did what it was supposed to do.

I also had a southbend lathe I bought with a friend for $45 (I paid the $45, he had a van and a place to put it) that had a broken apron casting that had been welded back together with nickel rod. It was never right.
And the backgear was shattered.
And it had a flat belt drive that was really funky and slipped off all the time.
Still, I made things with it.
Old Jack
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Re: ANOTHER reason NOT to weld cast iron

Post by Old Jack »

To Harold V. Thank You for your kind reply. OJ
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