Behold the broken gear lever for the QCGB on my late model Atlas/Craftsman 12. Like to take a shot at fixing it before try finding a replacement. I’ve got a gas welding outfit and a couple different kinds of fluxed brazing rod. I did enough brazing in HS to give me courage. Also I’m cheap. So why not, right…
My question(s) – can I save myself some work and keep filler metal out of the bore by leaving a stainless dowel in the void while brazing? Am I correct to assume the brass won’t stick to the stainless and should press out after everything’s cooled? Is there a better procedure with the resources I have? Or is there a better filler metal (on Amazon) for what I’m trying to do?
WWTFD? (What would the forum do…)
I binge-watched a ton of videos about repairing cast iron, and cast semi-steel. One starts with This Old Tony, and welding cast iron.
The whole range of options includes brazing with metal fillers that will wet to the iron, and fill gaps, but melt at lower temperatures than the iron, through to using nickel rods, and especially nickel-alloy rods specifically designed to match to, and repair, cast iron. I think they are the FeNiCo 65 alloy.
Your break was under tension, and is now completely open, and contaminated inside. The right way is to grind out the crack all the way to the middle, with a bevel angle, and then carefully lay in welds until it is filled. Then file out, drill and ream the hole. Folk have taken short-cuts in repairing cast iron, but putting it on a camper gas stove to keep it about 350C to 400C hot while you do the repair goes a long way to close up the temperature gradient between the weld and the iron while the fix is done. The advice is to keep heating some after the weld is done, for half a minute or so, then put the thing in a box of wood ash, covered over with ash, and leave it to cool slow. Some folk who have woodburners say the leave it in the stove overnight as it goes cold,
You can do this to leave enough of the original hole to help you re-machine the hole out. I think if you put a stainless rod in the hole, you are committing to a lower temperature filler. With enough flux in there to be effective on the iron, I am guessing you end up with a need to machine out stainless, which will be a bigger pain than fixing a hole with excess flow.
Any repair metal, joining to the iron, will make a new alloy in the metal it penetrated into, which will have new hardness, expansion coefficients, and internal tensions different to the original iron. You can definitely make effective repairs with various brazing rods. The hardball repair is to use an iron nickel cobalt alloy rod designed for it. You can get them on eBay.
If it's a critical part, for example a nonreplaceable one, and you want a professional repair, then using Castweld 65 nickel stick electrode under TIG would be the way to go. You'd want a bevel to fill, and you would only weld the outside to retain the bore. It would be permanent.
The silver solder you have will need some heat, but that would be my choice with oxy acetylene. Brass works too, just not quite as strong as silver.
With torch, blanket the part after the weld so it cools slowly. With resistance welding, pre-heat on the propane bbq and blanket after.
I've never welded cast iron, but I thought preheating the rods and the part, plus peening the weld as it cooled was best practice? Hopefully someone with first hand experience can provide some tips!
sino welding Product Page
I got a bit over ambitious with my chinese sheet metal folder and cracked the casting clean in half……. I was going to replace it with solid bar, but it woudln't hurt to have a go at welding it – it would save me £30 and a fair amount of swarf….
Edited By Russ B on 29/10/ 10:10:51
Hi, if you are using these Supercast electrodes, your welder will need an OCV, that is the voltage across your welding holder and the return lead (earth) needs to be at least 45 volts before you start welding. If you are using a DIY buzz box, you may not get that and you will have difficulty striking an arc. The electrodes don't need to be heated but they should be dry, which can be done in an oven at around 100/120 odd degrees for an hour or so. You should not need to preheat the joint to much more than about 150 degrees and you should keep the heat input low by keeping a short arc and not making the runs too long and peening should be done after every run while the weld is still hot. A little post heat can be applied after the weld is finished, but not by an excessive amount and allow it to cool on its own away from the cold and draughts.
Regards Nick.
Edited By Nicholas Farr on 29/10/ 10:38:32
I've never bothered with proper cast iron welding rods for home shop repairs. There is no doubt that the proper rods in skilled hands produce a stronger job but if you don't have the experience and don't use the correct procedures they can be serious trouble.
My method is to use a 1.5 mm ordinary general purpose rod at the lowest practical current to build up thin layers of weld on the two sides of the crack. Each layer should be peened with the chipping hammer before it cools off. This reduces cooling stresses but means you can only do the weld in short strips. Make sure everything is cool before adding the next layer. Once you have 3 or 4 layers each side do the final fusion in the normal way with a larger rod but don't use too thick a weld. Most stuff I seen needs three or more runs. Peen between runs as before and let everything cool off before the next run.
Yup it takes ages with all the waiting around for cool off but it does work.
Theory is that it sidesteps the two major issues of carbon migration and cooling contraction leading to cause failure if you simply weld cast iron like its steel. Carbon migration produces very hard, brittle joint lines which fail easily under stress. Cooling contraction guarantees plenty of stress. Carbon migration needs high temperatures. The thin layer build up process minimises temperatures and, once the first layer or two is done blocks the weld region from further migration. Peening helps counteract contraction stresses. Being thin layer means less stress anyway. Once you have a few layers of weld on the iron the final joint is weld metal to weld metal so that behaves just like an ordinary joint. Multiple thinner runs peened when hot again keep the cooling stresses down.
This is an official, albeit old fashioned, technique for field expedient repairs. That said I'd be chary about using it on anything liable to take serious tension loads. Frankly I'd be worried about serious tension loads on any home repair.
Lots easier with an inverter welder than buzz box 'cos you can turn the current right down.
Clive
There are many different cast iron rods available from 99% nickel down to various mixtures of nickel and iron. More iron = a harder, as in a non machinable weld.
I have found the rods easier to strike than similar size mild steel ones.
As you don't say what amps nor what size rod it's impossible to be more helpful other than to say 1.5mm rods will work on a 90A welder and have you checked the earth is good.
When it does work or you try to follow Clive's advice, if you hear a small tinkling sound after breaking the arc that's the weld cracking off the casting.
Back when I was doing repairs off all types we often got broken castings to repair.
Want more information on Cast Iron Stick Electrodes? Feel free to contact us.
we always discussed the job with the client to make sure that welding was the best (or only!) option.
If a weld repair was all that could be done then we would usually use a high nickel content rod as it was easier to machine after the welding. What we always did is use a welder with a high voltage which made it easier to strike and maintain an arc. A really old Murex/BOC welder was the favorite tool with up to 120 volt AC or DC. Probably illegal now!
A modern inverter welder works really well when set at a high frequency and with the proper rods.
If you do it right it will be as good as the original casting.
The rods are 2.5 I normally keep rods in airing cupboard . I did do a bit of experimenting and after I had managed to lay down a base layer, I tried a normal steel rod, as I at first wondered if the welder/leads were playing up, and found that the normal rod layed down much better.
Now I am wondering if the particular cast iron is different to the good old UK stuff as the machine is Chinese. Maybe more steel content.
If so, perhaps it takes normal rods ok ?
I had thought about metalock principal but where can you get the figure of eight wedges from ? If I could get some I would go that route.
Mike.
Its been 30 yrs since i last welded cast iron ! I have used high nickle rods , stainless and buttering runs with GP rods and all work and have their uses .
I would tend to follow what Fizzy has told you .
I would also have a read of the back of the box of electrodes as this will yield some important information like amperage requirements – these are ball park figures but they will get you near to what you need .
Voltage requirements , current type and preferred polarity if AC is not to be used ( some rods can use ac or dc some only like dc .
pre heat , i used to use a big acetylene torch to take the chill out of a part but depending on its physical size you may be pushing the proverbial up hill with a point stick if the part is big and for cooling i used a fireproof blanket or buried the part in a tray of sand if they were small enough to do so .
I also got into the habit of after grinding the V out i would go over it with a carbide burr as it has a cutting action which removes any of the graphite smear you get when grinding cast iron – not really going to cause an issue with a fusion weld but it will with brazing and i just got into the habit of doing everything the same way with cast iron regardless of whether i was welding or brazing it .
The last time I welded cast iron it was in the form of an ornamental clock face some three feet across, after many cracks appeared in places other than the areas being welded I resorted to a degree of pre and post heat and ultimately covering the whole casting in agricultural lime (slaked) keeping this is hot as I could with a spreader torch for two hours after welding had finished. The shape of the casting, many interconnecting segments, may also have caused uneven stresses to build up in adjacent areas not subject to welding heat. As this casting was more of an ornament than substance my efforts were acceptable I feel.
If pressed again to tackle a similar job I would concentrate more attention on pre and a longer post heat.
Guy
Contact us to discuss your requirements of Flux Drying Machine. Our experienced sales team can help you identify the options that best suit your needs.
Comments
Please Join Us to post.
0