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  1. #1
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    Default Oxy fusion welding cast iron

    Hi all, I'm trying to learn CI fusion welding for repairs and one-off CI constructions/reproductions.
    I'm currently attending a TAFE welding course (Cert IV engineering), and have been hobby welding for 50 years - just want to get rid of bad habits I've accumulated and learn new tricks). The teaching staff there have never learnt CI fusion welding, nor seen it done.....
    However, since I'm trusted there, I was able to rummage around the store and found several old packets of cast iron welding rods (made by CIG), dated in the '80s. I also found two unopened tins of cast iron welding flux - with user instructions on the labels.... go figure.
    So under the interested and watchful eye of my instructor, I got a few bits of CI out the scrap bin, cleaned them up and went at it.
    I heated the pieces up, pretty hot, but not quite glowing. A stip of pine burst into flame on touching the workpiece.
    Then heated the end of the rod to dull red and dipped it into the flux (280g Borax/kg - I wonder what the rest is?).
    Then I proceeded as if I was putting down a 'normal' bead. It flowed nicely, behaved somewhere between MS welding and bronzing. Seemed too easy, I must admit, given the 'mystery' surrounding CI fusion welding....
    After slow cooling and cleaning, the weld looked exactly like the surrounding CI, and appeared completely sound. I haven't cut any on the bandsaw yet to see what the penetration is like, but under the hood I could see both the workpiece and the filler running and mixing nicely in the puddle.

    I have a couple of broken CI bench vises to fix and a machine vice with swiss cheese pattern to fill. That's why I want to learn this. I also have a large drill press table with a broken off corner I would like to try restore to original.... the list goes on - broken out T-slots on a milling table etc.

    Next try will be the first bench vise and I'll take photos then.

    Any experience with this here? Any suggested procedures? Any other advice? No need for me to reinvent the wheel for such an old process....
    Cheers, Joe
    retired - less energy, more time to contemplate projects and more shed time....

  2. #2
    Join Date
    Jan 2004
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    Hi Joe,
    The place I started my apprenticeship at, Accurate welding Work of Cordelia, St. South Brisbane specialised in that welding procedure.
    The main application was the repair of cast iron diesel cylinder heads for 4 cylinder Hastings Deering Cat bulldozers.

    Joe, It is a hot, hot procedure and this time of year is ideal to do it, so, it is a full face visor for you and leather welding coat to keep you protected.

    The molten pool under the welding cone can get fairly large up to 10 - 15mm in diameter. You are dealing with a fluid puddle that has the consistency of cold treacle. The trick is to manipulate that puddle by working the oxy flame cone gently into that molten pool . Work it vertically and side to side and round and round - but do it GENTLY. No rapid torch movements.

    This gas flame cone manipulation serves to release any gas bubbles from contaminants contained by the cast iron and float them out to the top of the molten pool where they form an easily removed crust. Flick the flux into that molten pool regualarly to also release and float out those contaminants.

    If your broken vice parts are separate it essentail you fixture them to avoid them moving around from the welding procedure. Distortion can be extreme in unfixtured work.

    Bear in mind our # 15 welding nozzles were tricked up with a water jacket over the welding nozzle .It was just the water pressure from a a just cracked on tap and the output went into the drain. As we were working in red hot combustion chambers that water jacket was essential.

    For prep I can recommend vee ing out 3/4 material depth. Fill that and go back into the opposite side vee it out and backfill later.

    More later when memories come back into this old head.

    Grahame

  3. #3
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    Gees Grahame, I'm beginning to wonder if there is anything you 'Don't' know. What a great answer, I've never even heard of fusion welding CI.

    Phil

  4. #4
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    Heating or preheating the work is standard .
    Toss the job in a hot fire and get it up to red heat. We used a 2'' line gas line fire with a makeshift loose brick wall but maybe a brick-covered bench might suffice.

    Certainly, 2 pairs ( with 2 people ) of tongs to lift the red-hot vice to the bench. Keep the work out the breeze to minimize heat loss.

    During welding ensure the job is NOT bumped .There was often enough molten cast iron to do reall nasty stuff if it got into a boot.

    Now off to the drs for more pain relief.

    Grahame

  5. #5
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    Phil, I don't even remember what we called the process. Oxyacetylene welding of cast iron, maybe.

    We were the only firm in Brisbane that did it, so there ws not much knowledge of it, even then, in the mid-60s.
    Knowing everything mate !, far from it.

    As far as what I know, only a drip in the water to what you know. Forty-five years married I still don't know how women think?

    Grahame

  6. #6
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    Very interesting Joe and great info from Grahame too.
    I've had success using TIG to fusion weld CI on quite a few occasions eg (//metalworkforums.com/f160/t117...ding-cast-iron).
    This was something I just tried one day and have no idea if it's a recognised or recommended technique.
    Initially I used 316 filler but the resulting deposit was very hard and difficult to machine, I have since used mild steel filler and while the deposit is not quite as hard it is still similar to chill CI. I've successfully repaired a couple of smallish vices using this method and both are still going strong so it must be fairly sound.

    Like all welding, prep is king and things need to be very clean. Oil doesn't seem to be too much of a problem as it seems to burn away during preheat. However contamination from any epoxy based fillers etc makes the process pretty much impossible, even if the edges to be welded are taken back with a burr and all filler removed a good repair is impossible as I assume the CI absorbs it.

    I'd be interested to learn what material the oxy filler rods are and also where they and the flux might be available as I've only ever seen Ni Electrodes or Manganese Bronze filler at BOC for CI repairs. It would also be interesting to know how the weld deposit machines when compared to the base material.
    Cheers,
    Greg.

  7. #7
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    Joe before I forget.

    The oxy-acetylene balance is of paramount importance.

    If the flame is not set to neutral but allowed to run carburizing the carburizing effect of an already carbon-rich cast iron base can be catastrophic.

    I saw a stone disintegrated on a surface grinder. One of those jobbies that ran flat and spun while taking a broad swing cross the work.

    Normally, with properly set neutral flame, you can cut the weld face with a file.

    Given you take it easy and keep your flame neutral I don't think you will have any trouble.

    Maybe just a line of people saying, Joe my cast iron whatsit is broken, can you weld it?

    Good Luck

    Grahame

  8. #8
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    Hi Kiwi john
    I am surprised !
    My thoughts are that GTAW process would not lend itself readily to large volume. Hard to keep the heat in it.

    It might be OK with a smaller lightweight piece. The difficulty as I see it is the question of fillers.

    The filler Joe is talking about is a 5mm rough ingot shape of 100% cast iron maybe 700 mm long.

    Good filler for welding a vice with an oxy-acetylene heat source. The big cast iron rod is incompatible
    to even a large tig tungsten size.
    But any tig needed for something like a big vice would need to to be a big one to keep up that welding heat needed.

    Grahame

  9. #9
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    Hello Joe,
    You will find it easier to perform a downhand fusion weld on CI if you are able to incline the work at about 30 degrees up from horizontal. This keeps the top of the weld pool approximately horizontal without the tendency to flow ahead into the V preparation, and makes control of the pool easier. Success with CI welding depends on preventing contraction stresses when the item cools. CI does not like tension stress. It is vital that preheating and post-welding cooling control is carried out appropriately. For a challenge, you could try welding up a broken CI spoked wheel.

    Chas.

  10. #10
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    I'll update with some photos tomorrow night.
    I've ground back the weld edges and made a fixture to hold the two pieces together.

    To answer a couple of questions: the filler rod is pure cast iron and about 6mm diameter.
    The resulting deposit files just like any soft cast iron and is indistinguishable from the parent metal.
    Even to just run a couple of beads, I had to use a #15 oxy tip (large).
    I have an old Lincoln welding book, which recommends neutral to slightly carborising flame - never oxydising.
    I have seen a photo of someone in the US fusion welding with cut strips of CI about 3mm x 3mm - that might be a way of doing small repairs.
    Lastly, the flux is essentially Borax. I'll take a photo of both the welding rod packets and the flux container tomorrow.
    At home, I'll try cutting a strp of CI on the bandsaw and use ordinary Borax for a trial, one I have the technique down a bit more and can judge any differences to other consumables.

    The
    Cheers, Joe
    retired - less energy, more time to contemplate projects and more shed time....

  11. #11
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    When I was younger back in the early seventies a place near my home specialised in welding CI cylinder heads with oxy as said above heated in a oven thenbolted down and welded then back in the oven on a cool down cycle, then machined appropriately they gave me some rods I would have them in the shed somewhere

  12. #12
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    Hi Grahame,
    The CI pieces I've TIG welded are have probably been no more than 20 - 25mm cross section, although the Waldown drill press base I patched up certainly had a substantial total mass. These are some photos of a little drill press vice I managed to break in half as indicated by the arrows. I've used this vice many times since and not been gentle with it, so far the repair is hanging in and showing no sign of failing.

    Cast Vice Repair 01i.jpg

    The following shows the TIG welded repairs done using 316 filler rod.

    Cast Vice Repair 01a.jpg Cast Vice Repair 01c.jpg Cast Vice Repair 01b.jpg
    Cast Vice Repair 01d.jpg Cast Vice Repair 01e.jpg Cast Vice Repair 01g.jpg

    Below are photos of the drill press base which was welded using mild steel filler rod and no preheat.

    Waldown Base 05.JPG Waldown Base 08.JPG Waldown Base 09.JPG

    One of the trickier repairs I've done using TIG was a treadle sewing machine leg which was broken into half a dozen pieces. The piece was too big to preheat and because the heat is highly localised with TIG I had to be very careful when making the welds in order to avoid cracking due to differential expansion.

    Again, I've got no idea if this is a recommended practice and I would not use it to make a critical repair but I have found it to be very useful.
    Apologies for the thread hijack.
    Cheers,
    Greg.

  13. #13
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    kwibo99
    Awesome work. Very impressive!
    I am full of painkillers at the moment so will come back later when coherent.
    Grahame

  14. #14
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    kwibo99,
    Very nice work!

    In pics the weld interface blends and wets in nicely . Partly it is due to the smooth Tig arc and partially due to your choice of filler. On the same weld bead also you have avoided the trap of over filling and minimized any contraction . Overfilling the bead is the short cut to contraction cracking.

    Stainless steel contains nickel and chromium.

    As a filler alloy, the nickel is an ideal material to help in overcoming the contraction cooling from molten heat. It has the give and take the CI has not and alloys pretty well in most circumstances

    Most CI.welded is grey cast iron and apart from the high carbon up to 3 & 4% percentage is pretty manageable stuff, to a degree. You can be lucky get to weld on good grey cast iron. If you are not you can get caught on unknowens.

    Where it gets tricky is that that the carbon % varies from sample to sample and manufacturer to manufacturer. Some foundries cast wonderful CI’s to weld and others terrible.

    There are other grades of cast iron and only sometimes with them, do the welding gods allow us a win.

    Grahame

  15. #15
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    Right, here is an update with pictures.
    V-grooved the edges of the break with just enough of the broken edge left to get a good register of the two parts. I then fixtured the broken-off vice jaw to the body, using the holes for the removable strip as fixture points, as recommended by Graeme.
    I took the bits to school, along with a metal bucket of vermiculite and a dozen lightweight firebricks.
    Once set up, I heated the whole shebang with the cutting torch to just below glowing dark red in a makeshift 'furnace'. The wooden handle of the wire brush just caught fire when touching the workpiece. This was the recommended temperature in a very old Lincoln welding book I have....
    Then swapped to a #15 welding tip and had at it with a very slightly carburising flame.
    Every few minutes during welding, I pointed the flame at the rest of the workpiece to keep it all hot.
    Once I had filled the V-groove from the front, I removed the fixture and welded the joint from the back for 100% penetration.
    I followed Graeme's advice and played the flame in each short section of the puddle to ensure that anything floating was ejected and found that a few gas bubbles were trapped too - they came to the surface quite visibly.
    The other thing I found was that when the cast iron rod and cast iron work melted together, it really was like toothpaste or treacle - however, playing the flame in the puddle quickly made it very liquid without warning, and a couple of times, bits of the puddle ran away on me and dripped on the floor! So this is not a process to do out of position.
    When finished, I reheated the whole thing evenly again and then dumped it in my bucket of vermiculite and covered it up as far as I could (I didn't take quite enough with me).
    Tomorrow will show if it worked - and how good the weld metal is, as far as porosities is concerned. I'll clean it all up and grind off the excess beads and lumpy bits. I'll take some close-up shots of the welds themselves then.
    20180827_140502~01 (Website).jpg 20180827_145625~01~01 (Website).jpg 20180827_145559~01 (Website).jpg 20180829_183845 (Website).jpg 20180829_190103 (Website).jpg 20180829_190641 (Website).jpg 20180829_191558 (Website).jpg 20180829_191634 (Website).jpg 20180829_191921 (Website).jpg 20180829_182149 (Website).jpg
    Cheers, Joe
    retired - less energy, more time to contemplate projects and more shed time....

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