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Cast Steel Welding

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  • old jupiter
    replied
    Welding cast iron right IS tedious, Olivero, no way around that.

    My opinion is that the "best" way to weld the usual sorts of grey cast iron is by gas welding, which is REALLY tedious, requiring a long slow preheat to well over a thousand degrees (exact temp depending on the content of the cast iron, if you can find that out). Do the welding with the casting closely surrounded with (also very hot) firebricks and wrapped in forbidden asbestos cloth, with only the actual weld area uncovered. Use cast iron rod dipped in cast iron flux. Rather than dipping rod in a liquid puddle, you stick cast iron rod into the mushy iron puddle with a sort of jabbing action which tends to displace the oxides and glop up to the top of the puddle. Make a big ugly, kind of crusty-looking build-up because you are going to machine off or rotary file off much of it and get down to good new iron. A very slow operation. After welding, completely wrap the very hot part and the firebricks with the asbestos cloth, This method ends up with the most uniform material in your part. A stress-relieving "normalization" operation might also be called for. I'm glad I haven't had to do this in decades, but it was sort of impressive to do at the time (fixing a couple of racing outboard motor cylinder blocks, . . . none of which have been made of cast iron in a looong time).

    Generally I prefer to gas-braze cast iron, if I have to do it at all.

    There's also a sort-of-quick method I once used to fix a cracked exhaust manifold (Ford 240 six). You can sometimes get away with stick-welding a broken grey iron casting COLD, using NiRod. Vee out the crack after "stop-drilling" holes at the very ends of the crack. I might, as I usually do with any welding, have given the manifold enough heat to drive off any moisture, but that's all, and when I started welding the part was only warm to the touch. I welded a half-inch long bead and STOPPED, did some peening while it cooled, and waited until I could hold my hand on the first bead, then welded another half inch and repeat process. Tedious for sure, and if you try this technique you must NOT be in any hurry or you'll soon hear the faint little pings of the new cracks.

    But that poor manifold, which at the time I welded it was already twelve years old and had probably already lost some of its original properties, still held up without further cracking for another twenty years, which amazed me. When I had to do some engine work (those Ford 240s were TOUGH!!), I took a close look at my old repair. The Ni-Rod bead had contracted over the years, pulling away from the sides of my Veed-out crack, and looked like a length of dirty grey clothesline lying in the middle of the V-groove. Yet it still had adhesion at the bottom of the crack, and was still sealing the manifold from any exhaust leaks and noises. Still amazes me!
    Last edited by old jupiter; 05-21-2016, 10:41 AM.

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  • ryanjones2150
    replied
    Yup, and it would probably be stainless or aluminum too. Now what....that's the kind of stuff that makes a man resort to profanity. By gosh.

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  • Meltedmetal
    replied
    Originally posted by fabricator View Post
    I would weld it to a steel plate and be done with it.
    You then might want to cover the slots in the base, or bolt it to the plate or live with the accumulating chips in the base. And I know for me the first thing that would happen is I'd drop some small part that would bounce right into those slots.---Meltedmetal

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  • fabricator
    replied
    I would weld it to a steel plate and be done with it.

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  • ryanjones2150
    replied
    which is exactly what you're doing when you weld continuously, heating one part and letting another cool. The difference in the expansion and contraction and the cooler metal around it contributes to the cracking. So pre and post heat aim to even that out. Peening relieves the stresses caused by the weld puddle solidifying.

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  • Olivero
    replied
    Sounds really tedious that way, I welded mine pretty much non stop, only stopping to find the next seam. If you keep heating one part and letting another cool, does that not make it more prone to crack as you now have different expansion-contraction across the piece?

    I will need to get a Mordor fire pit though.

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  • ryanjones2150
    replied
    cast iron, hands down, way harder to deal with. Not that you can't light up on it and melt metal together, but its all the other "things" that cause problems. If you preheat it like I was saying...or by tossing it into the fires of Mordor for a while...it will burn that goop out of there. Which is why you cook the hot dogs BEFORE you throw your piece in for preheat. The post heat just keeps it from cooling too slowly and cracking all over the place. I've peened only small repairs that I've used a cast iron welding rod for. You don't have to beat the living daylights out of it either. And its a battle, weld a bit, peen it...weld a bit, peen it...repeat.

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  • Olivero
    replied
    Here is the base.

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  • H80N
    replied
    Here is an overview from the Harris site that may be helpful

    http://www.harrisweldingsupplies.com...cast-iron.aspx



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  • Olivero
    replied
    Okay cool, I noticed what looked like oil was seeping out of the base yesterday after I welded it, i noticed what looked like oil running down the side of it but figured it might just have been from using oil while drilling in the past and it might have made its way down, but I guess it could be from the casting.

    I did clean up whatever I saw but by the time I was done, there was more. Didn't think much of it at the time.

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  • H80N
    replied
    Originally posted by Olivero View Post
    Cool guys, thanks for the replys. I will have to try the slow cool down and see if it prevents the cracks.

    So which contains more carbon, A.K.A is harder to weld, cast steel or cast iron?
    Cast iron presents the greatest challenges...

    on top of all else.... "Cast Iron".... can encompass a huge range of alloys... some fairly easy to weld.... others so full of impurities (and or oilsoaked) that they are near impossible to join...

    It can be a crapshoot... each one is different...

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  • Olivero
    replied
    Cool guys, thanks for the replys. I will have to try the slow cool down and see if it prevents the cracks.

    So which contains more carbon, A.K.A is harder to weld, cast steel or cast iron?

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  • ryanjones2150
    replied
    I've tig brazed cast iron with great success, including reattaching a vice jaw that I snapped off. The tig braze is a good choice because you're not actually melting the base metal and therefore avoid the cracking issues. If you say you can see five or six cracks, there are plenty more and go deeper than you probably think. Here's what I've done in the past:<br />
    <br />
    Prep the pieces and get a couple of tacks to hold it in place.<br />
    <br />
    Start a nice fire outback, cook some hotdogs on it then toss your piece in the fire. <br />
    <br />
    Eat the hot dogs. <br />
    <br />
    Now go fish your piece out and wrangle it to your welding bench without melting your hands off. <br />
    <br />
    Brush it off and get after it. Once you have it done, put it back in the fire and leave it overnight. <br />
    <br />
    Be good to go the next morning. <br />
    <br />
    Probably need a new paint job though.

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  • aametalmaster
    replied
    Your base is cast iron NI rod will do the job whatever you preference is with a welding machine. Cast steel can be welded with 7018 or MIG or any other process you want. Big difference in material. But your base will be cast iron...Bob

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  • cruizer
    replied
    Kitty litter or floor dry works best and is simple to get for that slow cool down

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