Cast Iron Repair
Moderator: Harold_V
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warmstrong1955
- Posts: 3568
- Joined: Thu Mar 18, 2010 2:05 pm
- Location: Northern Nevada
Re: Cast Iron Repair
redneckalbertan wrote:Not sure what Bill means by heat gun but an IR thermometer would be handy. Never used one but many times I've wanted one. Any time I've had to control heat for a procedural weld I've always had templesticks to use, but they tell you one temperature only so you don't know what the temperature is, just whether you are over the marked temp or under.warmstrong1955 wrote: Heat guns can be handy too, to give you an idea how fast things are cooling down.
Bill
An IR thermometer is exactly what I'm talking about. I've got a couple of 'em. Cheap now-a-days. Lot better thaan temp sticks....which I have some of too, but havn't used in quite some time.
Bill
Today's solutions are tomorrow's problems.
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hammermill
- Posts: 2938
- Joined: Sun Jun 27, 2010 10:43 pm
- Location: pendleton or
Re: Cast Iron Repair
plus one on ir heat guns now a days I figure maybe 25 dallors up depending on range and lazer pointers. I try to see all the techs have one in the tool bag. darn useful all the way around. often times you see them as noncontact thermometers
Re: Cast Iron Repair
The ship's engineer and I were having a conversation this week regarding cast iron repair. He has access to an old D-8 that has a need for some water jacket repairs due to the farmer leaving only water as coolant during a freeze. He asked me about stitching, which I have never heard of, then proceeded to show me some of the repairs done with the process. Maybe this will help....
http://www.locknstitch.com/Metal_Stitching.htm
http://www.locknstitch.com/Metal_Stitching.htm
Re: Cast Iron Repair
There is a young hick on youtube, chucke2009 something like that, who shows various ways of welding cast iron. It's a little high strung, but you might get something out of it.
I think he had a video on stitch welding cast iron, with lots of peening...
http://www.youtube.com/user/ChuckE2009/ ... =cast+iron
I think he had a video on stitch welding cast iron, with lots of peening...
http://www.youtube.com/user/ChuckE2009/ ... =cast+iron
Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...
Re: Cast Iron Repair
Russ,
I've covered this in earlier posts, but it is worthy of a repeat.
What is a weld? According to the textbook it is defined as: "a casting surrounded by a heat treatment".
The casting portion of it is the melted parent metal combined with the filler metal into a final alloy. The heat treatment is the total effect of the heat added to the area of interest during the process.
The pre-heating/post-heating cycle usually applied to cast iron alloys for weld repair is not strictly for the purpose of "heating" as much as it is for the control of cooling rate. The control of the cooling rate is significant as it allows dissolved carbon to precipitate out as graphite rather than to remain as brittle carbide. The classic case of a "tear-out" failure of a cast iron weld repair at the root of the weld puddle is primarily due to carbide embrittlement from a too rapid cooling. The high temperature of the electric arc (10,000 or so deg.) causes the carbon, which is freely available in cast iron, to dissolve in the iron, beginning just outside the molten pool. The mass of adjacent iron draws the heat out of the carbide formed faster than the carbon can precipitate out, creating a thin layer of iron carbide, which, at the first sign of stress, fractures, causing failure of the repair. From the pictures, this appears to have occurred here.
As heat flow is governed by the temperature difference between the hot side and the cold side of the system involved, pre heating minimizes this temperature difference around the critical temperature where iron and carbon dissolve and precipitate, and minimizes the chances of retaining the carbide in the undesirable "frozen" state.
As I have stated before, I am much more of a torch man when welding cast iron than an electric rod man. I find that the application of larger quantities of cooler heat (6,000 vs 10,000 deg) gives me a better finished product. Also the alloy I use (MG-240) does not seem to have the degree of alloying elements, like nickel, which doesn't have the differences in coloration, that may be aesthetically important in some instances. You work the rod under a crust of flux that kind of resembles a blob in a 50's sci fi flick, working from surface to rod and from hotter to cooler surfaces. I just like the way the torch functions in this respect. Nice and slow and controllable and plenty of excess heat to keep things nice and warm.
I like Hammermill's boiler section idea for pre-heating, as it is a "soft" heat generally and generously applied, and provides for excellent post cooling. It is very similar to the system I use for annealing the axles I am so fond of using for raw stock. You could probably use something like the bottom of a 55 gallon steel drum and charcoal to heat the area of repair, blanketing the rest of the structure with fiberglass insulation. An IR thermometer is a good buy, as the prices have come down and the temperature range has gone up, not quite to casting range, but still very useful. Despite the desires of your friend, I don't think no teardown is a good idea. Beside the obvious avoidance of collateral heat damage, it's a good opportunity to "tune up" the rest of the tool. If he's just doing a quick fix so he can foist it off to someone else as a serviceable tool, slap him for me. The world's got enough of those guys.
Be aware that the pre heat is maintained during the weld, and make provisions to deal with the significant radiated heat produced by it by shielding with bricks or sheet metal, so you don't get fried in the process. With good pre-heating (if I were doing it, I'd go for a dull red) a narrow vee, no more than 30deg, and minimal peening, no more than necessary to remove slag, it should be satisfactory. You still, however, have to get all the old failed weld material out. Keep us posted as to results.
Good luck.
BTW, the remaining weld products AND the IR thermo should be yours as a thank you and would be money well spent on his part.
Bill Walck
I've covered this in earlier posts, but it is worthy of a repeat.
What is a weld? According to the textbook it is defined as: "a casting surrounded by a heat treatment".
The casting portion of it is the melted parent metal combined with the filler metal into a final alloy. The heat treatment is the total effect of the heat added to the area of interest during the process.
The pre-heating/post-heating cycle usually applied to cast iron alloys for weld repair is not strictly for the purpose of "heating" as much as it is for the control of cooling rate. The control of the cooling rate is significant as it allows dissolved carbon to precipitate out as graphite rather than to remain as brittle carbide. The classic case of a "tear-out" failure of a cast iron weld repair at the root of the weld puddle is primarily due to carbide embrittlement from a too rapid cooling. The high temperature of the electric arc (10,000 or so deg.) causes the carbon, which is freely available in cast iron, to dissolve in the iron, beginning just outside the molten pool. The mass of adjacent iron draws the heat out of the carbide formed faster than the carbon can precipitate out, creating a thin layer of iron carbide, which, at the first sign of stress, fractures, causing failure of the repair. From the pictures, this appears to have occurred here.
As heat flow is governed by the temperature difference between the hot side and the cold side of the system involved, pre heating minimizes this temperature difference around the critical temperature where iron and carbon dissolve and precipitate, and minimizes the chances of retaining the carbide in the undesirable "frozen" state.
As I have stated before, I am much more of a torch man when welding cast iron than an electric rod man. I find that the application of larger quantities of cooler heat (6,000 vs 10,000 deg) gives me a better finished product. Also the alloy I use (MG-240) does not seem to have the degree of alloying elements, like nickel, which doesn't have the differences in coloration, that may be aesthetically important in some instances. You work the rod under a crust of flux that kind of resembles a blob in a 50's sci fi flick, working from surface to rod and from hotter to cooler surfaces. I just like the way the torch functions in this respect. Nice and slow and controllable and plenty of excess heat to keep things nice and warm.
I like Hammermill's boiler section idea for pre-heating, as it is a "soft" heat generally and generously applied, and provides for excellent post cooling. It is very similar to the system I use for annealing the axles I am so fond of using for raw stock. You could probably use something like the bottom of a 55 gallon steel drum and charcoal to heat the area of repair, blanketing the rest of the structure with fiberglass insulation. An IR thermometer is a good buy, as the prices have come down and the temperature range has gone up, not quite to casting range, but still very useful. Despite the desires of your friend, I don't think no teardown is a good idea. Beside the obvious avoidance of collateral heat damage, it's a good opportunity to "tune up" the rest of the tool. If he's just doing a quick fix so he can foist it off to someone else as a serviceable tool, slap him for me. The world's got enough of those guys.
Be aware that the pre heat is maintained during the weld, and make provisions to deal with the significant radiated heat produced by it by shielding with bricks or sheet metal, so you don't get fried in the process. With good pre-heating (if I were doing it, I'd go for a dull red) a narrow vee, no more than 30deg, and minimal peening, no more than necessary to remove slag, it should be satisfactory. You still, however, have to get all the old failed weld material out. Keep us posted as to results.
Good luck.
BTW, the remaining weld products AND the IR thermo should be yours as a thank you and would be money well spent on his part.
Bill Walck
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Russ Hanscom
- Posts: 1955
- Joined: Wed Mar 15, 2006 11:10 pm
- Location: Farmington, NM
Re: Cast Iron Repair
The job is done.
It ended up taking five nights. The first was to grind the parts down to get the broken surface flattened and to get some V groove. Night two was to coat the future mating surfaces with 3/32 high nickel repair rod. Preheat was about 500 F per the Lincoln welding handbook. The small part maintained temp from welding, the large part required a constant heat input. I was not satisfied the way the rod did not want to maintain a smooth bead, the result was a bit more lumpy than desired. Night three was used to grind the surfaces flat and test fit the parts. Night four was the big weld, it took three hours of welding, grinding, and peening to get the groove filled. For alignment, a bar was clamped in the V groove and the broken part was held with a clamp and several bolts. We started with a 500 F preheat but his torch quit mid way through so the final temp of the work area was 200+ F - the main casting weighs about 2000#. Not much I could do but carry on. Obviously no controlled cool down period. Total consumption of rod was about 4#.
Night five I tipped the machine upright with the truck and some creative rigging, I did not want to wait for him to locate a crane - he was moving the shop so during the initial move, I had the casting placed for best welding access. Once the machine was upright, I finished grinding off the excess and cleaned up the V groove. We installed the hammer and it seemed to slide properly - the gibs still need final adjustment. There are now three 5/8" grade 8 preload bolts installed which should reduce the tendency for future cracking. Once he gets the power reconnected, I will stop by and see how it is working.
I have an IR thermometer that was used for temperature measurement. A needle scaler was used for peening the welds.
No pictures of note, I was too busy trying to make this work to stop and take photos.
It ended up taking five nights. The first was to grind the parts down to get the broken surface flattened and to get some V groove. Night two was to coat the future mating surfaces with 3/32 high nickel repair rod. Preheat was about 500 F per the Lincoln welding handbook. The small part maintained temp from welding, the large part required a constant heat input. I was not satisfied the way the rod did not want to maintain a smooth bead, the result was a bit more lumpy than desired. Night three was used to grind the surfaces flat and test fit the parts. Night four was the big weld, it took three hours of welding, grinding, and peening to get the groove filled. For alignment, a bar was clamped in the V groove and the broken part was held with a clamp and several bolts. We started with a 500 F preheat but his torch quit mid way through so the final temp of the work area was 200+ F - the main casting weighs about 2000#. Not much I could do but carry on. Obviously no controlled cool down period. Total consumption of rod was about 4#.
Night five I tipped the machine upright with the truck and some creative rigging, I did not want to wait for him to locate a crane - he was moving the shop so during the initial move, I had the casting placed for best welding access. Once the machine was upright, I finished grinding off the excess and cleaned up the V groove. We installed the hammer and it seemed to slide properly - the gibs still need final adjustment. There are now three 5/8" grade 8 preload bolts installed which should reduce the tendency for future cracking. Once he gets the power reconnected, I will stop by and see how it is working.
I have an IR thermometer that was used for temperature measurement. A needle scaler was used for peening the welds.
No pictures of note, I was too busy trying to make this work to stop and take photos.
Last edited by Russ Hanscom on Sat Aug 09, 2014 8:46 pm, edited 1 time in total.
Re: Cast Iron Repair
Russ 
Congrats's on your success.
That story sure brought back some memories
Thanks for sharing.
Ken.
Congrats's on your success.
That story sure brought back some memories
Thanks for sharing.
Ken.
One must remember.
The best learning experiences come
from working with the older Masters.
Ken.
The best learning experiences come
from working with the older Masters.
Ken.
Re: Cast Iron Repair
Aloha,
I remember in the late 40's, my Dad had a job removing some dirt from the mountain for a pressing job. It was early evening when something broke on the shovel (the old type with cables that scooped from the front and emptied from the bottom) and his mechanic brought out his acetylene, oxygen welding torch. It must have been about 24"'s or more and he welded the bucket. Nothing fancy in the old days and all the repairs that I saw was done with a torch or a gas Hobart arc welder. Nothing like the good old days and having an experienced welder.
Mahalo,
doogdoog
I remember in the late 40's, my Dad had a job removing some dirt from the mountain for a pressing job. It was early evening when something broke on the shovel (the old type with cables that scooped from the front and emptied from the bottom) and his mechanic brought out his acetylene, oxygen welding torch. It must have been about 24"'s or more and he welded the bucket. Nothing fancy in the old days and all the repairs that I saw was done with a torch or a gas Hobart arc welder. Nothing like the good old days and having an experienced welder.
Mahalo,
doogdoog