Welding crack in thick cast iron.

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Ok so a guy at work is looking to restore one of the pullboxs pictured below. It's made of heavy cast iron. Probably 1000lbs.Anyway, it has a crack in one side of the lower body. Thankfully the crack is on a straight flat surface and not over anything decorative or curved. Probably a 10" line.As far as I know, oxy fuel welding it is the way to go. I don't have a torch or the skill. I have a MIG TIG and stick welder. I've never stick welded but I can grind it to death I don't care. What I do know is either way I have to pre heat.(i have an acetylene torch just no oxy fuel)And obviously I need to take time to grind a bevel into it and clean it up. No problem there.So what next? www.FirehouseFabricators.comZachLincoln 210mpLincoln SW200Hypertherm Powermax 45xp2x4 CNC Plasma Table.
Reply:First off it's BAD being on a straight flat surface. That's the hardest type of cast iron to repair. Curved surfaces are a lot easier.   I just got through fighting the water tank on the engine I was working on. Nice flat surfaces like to crack when cooling. I was heating the whole piece from below while brazing from the top. Covering with blankets to cool slow and peening to relieve stress and it still took 4 tries to get it done.Millermatic 252XMT 304'sDynasty 280DXHypertherm PowerMax 1250Miller Trailblazer 302 EFIOptima PulserXR feeder and XR Edge gun and more athttp://members.dslextreme.com/users/waynecook/index.htm
Reply:I doubt it's really "thick". My guess from working with similar cast iron objects is that the thickness is most likely 1/2" to 3/4" tops. With iron I wouldn't really call that thick.Plenty of options open for you. If it's in reasonable shape, I'd braze it. The color difference won't matter because it will be painted most likely. I've also seen cast ground out and "cold" welded with high nickel alloys. With this you do really tiny beads. You don't want the material to get hot enough you can't lay your hand next to it after welding. You move around a lot to keep the heat down. I've had good luck with both methods of repair. If you preheat, you'll need to post heat as well, and bury it in vermiculite or something else to slow the cooling rate as much as possible. I've had mixed results doing this, probably because with larger items it's hard to really preheat them well without proper tools like an oven.If any one here has the knowledge to do it right, it's probably member Castweld. Look up some of his cast iron repairs or send him a PM. He's got a few more tricks under his sleeve as well like spray welding. I haven't seen him around for a bit, but last time I remember him being on he was swamped with work. I'm hoping that's the case right now, but he might reply to a PM..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Before you do any grinding or heating drill holes at the ends of the crack or cracks to keep them from spreading.
Reply:I'm guessing brazing is out for me. Never done it. Probably not gonna learn on this.Would a high nickel alloy stick rod be my best bet? I saw a video where Lanse did it with nickel rods and back stepping.As far as thick goes 1/2-3/4 is thick for me www.FirehouseFabricators.comZachLincoln 210mpLincoln SW200Hypertherm Powermax 45xp2x4 CNC Plasma Table.
Reply:MJD has a good point! A hole at either end of the crack will limit the potential for the surrounding area to develop a crack past your weld while cooling.I have had very good success with nickel rods on cast iron (about an 80% success rate). I normally clean the piece to death, put a nice rounded bevel to the crack/broken pieces, preheat to the 600-800 degree range depending on thickness and quality, thicker parts can handle a little more heat but always watch your interpass temps. Overheating is bad just like under heating (unless using the stitch method that DSW suggested). Once I've reached my preheat I will weld immediately and usually keep heat on it using a torch or heat gun while it slowly cools off (sometimes takes up to an hour or so), all the while I will softly to moderately tap the part Untill it has reached a temp that is safe to touch. Don't get too carried away with the hammer because cast iron is tough as nails and still brittle as an egg shell at the same time.The most important thing you must do to obtain success is say this phrase when your done...."for the love of god please don't crack, please, please,please!!!!) and everything should turn out fine! LolGood luck!Last edited by Dantheharleyman99; 12-09-2014 at 05:34 PM.Real welders know how to penetrate!(Equipment)Whatever can be used to beat my opponent into submission!
Reply:You need to check into UTP rods as they are the gurus of cast iron. Read on their techniques and do it just like they say and you won't have any problems. You won't have to drill holes, preheat or postheat either. I've been using them for 30+ years and have never had a problem. They are expensive though.
Reply:I'd braze it. As an amateur, I've had a lot better luck brazing cast iron than welding it. I'd use silicon bronze filler and O/A with borax for flux. Or TIG.You could probably get away with just brazing it in a few places (at the ends and maybe in the middle if the crack goes all the way to both ends) and fill the rest of the crack with epoxy and cabosil filler. Then sand and paint.Good luck.Last edited by Kelvin; 12-10-2014 at 07:35 AM.
Reply:Silicone bronze doesn't do well brazing cast iron with a torch. You have to get it to hot which tends to burn the cast iron making it difficult to get it to flow properly. Low Fuming rod is the right one to use with a torch.  Really need more details of where and how the piece is cracked before any real info can be suggested. If it's not structural then a lot of option open up.Millermatic 252XMT 304'sDynasty 280DXHypertherm PowerMax 1250Miller Trailblazer 302 EFIOptima PulserXR feeder and XR Edge gun and more athttp://members.dslextreme.com/users/waynecook/index.htm
Reply:I like welding as much as anyone here, but sometimes there are other alternatives that might be better.http://www.locknstitch.com/
Reply:Drill the ends with a small drill..."V" out the crack.....Fill holes and crack with Bondo..Let dry..sand...paint....Who knew?...zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Originally Posted by zapsterDrill the ends with a small drill..."V" out the crack.....Fill holes and crack with Bondo..Let dry..sand...paint....Who knew?...zap!
Reply:Dude took a totally gnarly break from hanging out with Bill and Ted on their excellent adventures to do a video on welding cast with no pre-heat.  Don't know if Rufus would approve or it'll get you that "A" you need on your history presentation but it might keep you from being sent to military school.  Dude did some other flicks that might be most excellent (or bogus) for your situation also  Party on, dude(the above will only make sense after you watch the vid)
Reply:Got me , Chucke2009 !
Reply:Hi, I welded cast iron with mild steel welding rods.........using a plasma welder......yeah yeah I know you don't believe in Father Christmas either, but I've done it, so the proof is in the pudding.It goes without saying that preheat and post cooling on critical sections is a must do procedure and drilling for cracks etc, or the weld zone will just develop stress zones and attempt to pull away from the parent metal due to differential expansion and contraction.One piece I welded on was the bottom half of a cast iron die set base, 40mm thick and about 180mm wide and it had various holes from previous tool mountings etc.It was purely an experimental piece of work to see how the "equipment" performed on cast iron.The first weld attempt was with a cast iron rod.....pure uncoated cast iron, not the nickel variety normally used on castings etc.I was not impressed as the weld area, a hole approx. 20mm diam, was as porous as a piece of Swiss cheese.....so I tried a piece of plain welding rod.....grade unknown, but plain steel with the flux coating removed.This gave better results and after attacking it with an angle grinder the weld zone was very acceptable, that is it didn't have the itty bitty pock marked weld the cast on cast gave me.After that the next job I did for a mate of mine was a small clamp for a wood working saw bench.....it was a casting that had broken across the middle of the hole and previous attempts by an "expert" or professional welder had failed as it broke in the same place again revealing the inner structure to be as porous as the one I did before using the cast iron rods.......the guy didn't charge for the job as he said it would only be good to look at......sheet!What the cast iron rods were for I do not know, but you'd have a hard time with oxy/acc if they were for that medium.I can only say that when the weld zone comes to about 1300 deg c and starts to melt the steel combines with the iron and forms a high carbon alloy that is more ductile than the iron by itself, so as it worked in both cases, I can only offer this as a give it a go and see how it turns out solution.BTW......you might need a plasma or Tig welder to get the same results.....can't say for the Tig, but it's similar to the plasma and will probably work if you try it.Ian.