Good advice or downright dangerous ???

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I've lined bored my excavator swing tower. It is made of ductile iron so I sleeved it instead of building up with weld and boring out.I made a Youtube video of my experience:http://www.youtube.com/watch?feature...&v=ZHSxLmJBD4Yand I've recieved a comment which I think I should get some further opinion on. I appreciate the guys advice but unless people more knowledgeable than myself say it's OK, I'm inclined to think the advice is potentially dangerous and could lead to failure of such a part.Here is the commment:"You can weld these holes in this part. I use welding wire ER70S-6 wire at .035" size. I weld the bearing brackets on with nickel rod. The secret to the welding is that you must over-bore the holes to allow for at least 2 welding passes (I use a Boretec bore welder, but you could use a simple MIG welder). The weld deposit will be easily machinable using the carbide bits you are using. This will save having to make the sleeves thus eliminating a future failure point."Everything I've learned about welding cast iron stresses at least plenty pre-heat and maybe even post heat. I've seen how weak the welds are on cast iron if not done properly. A knowledgeable member on another forum puts cast iron parts in a furnace after welding to "make them behave" (his words LOL). I take it this is to anneal the brittle and weak heat affected zone, and bring back the toughness.Won't just doing a couple of layers of weld still create a very hard, brittle and weak heat affected zone where the first weld joins to the cast iron. Also if this guys method would create a weak area, a lot of the original metal has been machined out so there's not a much "meat" left of the original good stuff.  So far I've had 2 line boring guys say they wouldn't weld ductile iron bores, only sleeve them.
Reply:Iv'e rolled the dice with cast iron many times and many different ways. Personally I would listen to the line boring guys, but out in the field you just don't have that option sometimes. As far as putting it in a furnace and bringing it down slowly that's a big 10/4 from me. If you have that option. That will bring the cooling process down slowly and evenly and keep the dissimilar metals from rapidly shrinking during the cooling process causing the weld to pull apart and stress the porus cast.I hate being bi-polar it's awsomeMy Heroes Have Always Been Cowboys
Reply:Thanks Mike,I've been Googling the matter of welding ductile iron and seems the only practical in the field method I've read about so far, is to use special high strength high nickel content rods or even a special flux core wire. A few welders have talked about the inablity to maintain an even preheat temp of around 600 while welding and so variations in temp could cause more cracking problems than they solve. These special rods/wires are supposed to help get rid of the cracking problem too, something about how the carbon is affected by the weld.In the comment I recieved the guy is just using pretty standard mig wire for steel.
Reply:Nodular ductile iron is a bit different than gray, white or malleable, at least I've been led to believe from old books where they did a lot of repairs."USMCPOP" First-born son: KIA  Iraq 1/26/05Syncrowave 250 w/ Coolmate 3Dialarc 250, Idealarc 250SP-175 +Firepower TIG 160S (gave the TA 161 STL to the son)Lincwelder AC180C (1952)Victor & Smith O/A torchesMiller spot welder
Reply:With me it all depends on what is easiest..But 95% of the time we bore and sleeve or turn and sleeve.Keeps the weld area to a minimum and the yelling and screaming at bay.......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:There is a lot of different types of cast out there with lots of different properties so no one answer is correct. Some you can get away with it while on others you can't.   As for boring over size and welding up here's my take on it. In nearly all cases where a heavy preheat, maintained heat, and post heat isn't done there will be a layer of very very hard carbides where the weld meets the original cast part. This isn't good for a strong bond but in this case that's not as important as other factors. The first layer of weld will also be very hard and near impossible to machine. A second layer over this will reduce that hardness and each layer after that will get easier to machine as the excess carbon from the cast gets diluted by more soft weld. Basically what he's doing is casting a sleeve in place with the weld. It's one way of doing it but far from my preferred method.   If high nickel rod it used (like 99%) then the carbide transition layer will still be there and very difficult to machine. However the weld deposit it's self will be of a much softer and very machinable nature so if you don't try to machine through the weld to the cast you're alright. Still not my favorite but a common method. Nickel wire's are out there in fact I just tried some a while back when a maintenance welding type salesman came by. We welded on some cast iron and once I got it dialed in it wasn't completely terrible to weld with. But attempts at drilling through the welds showed the transition layer was there. I could drill the cast iron next to the weld easily as well as the weld itself. But trying to drill through the weld into the cast iron was impossible. Also don't ask about the cost of this wire unless you're sitting down and have your heart medication handy.   I really wanted it to work so I could stop doing all the brazing I do on some of the castings I get in. But what happened was exactly what I thought would happen which is why I hadn't tried it before. But since he was offering to let me try it for free I didn't have anything to loose.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:Thanks very much for the replies.Nice detailed explanation Wayne, cheers.Guess the big question is what is the lesser evil. Both sleeving and building up with weld take away some of the original "meat" so you are left with a thinner "ring" of the original metal to take the tensile pull. If you build up with weld and rebore, you have a brittle transition zone between the thinner "ring" of original metal and the built up weld. My calculated guess (and it's just a guess) is that machining extra original metal away to leave a thinner ring so that you can build up with TWO layers of weld, is worse than machining less original metal away and putting a thin sleeve in.So maybe the least evil of the lot is to use a special nickel welding consumeable so it's not necessary to do two weld buildups and therefore don't have to remove so much original metal. Of course if you don't take enough metal away and hit the hard part of the weld.........ouch. Plus I've heard a few times about the cost of that wire, wonder if they sell it in small quantities (like enough to build up one bore LOL).I think I'll stick to sleeving.Keith.Last edited by mancavedweller; 07-09-2013 at 03:14 AM.
Reply:either method will work, building up and boring, or making sleeves.  Most of the work that I do we have to build up and machine to make the bushing fit.  I have for the past 25 or so years used 70S-6 wire, but recently I vistited the Liebherr factory in France and they recommend 100 series wire in the bores............I have built up thousands of Liebherr bores with 70 series wire without issue, so I am going to stick with it, but do some testing with the 100 series wire and see what happens.  Most of the repairs I make are the result of grease system failures, not long term wear, but I have noticed that my repairs only last 3-4 years, where a factory bore will last 5 years if the grease system is maintained...............what I mean by "last" is the bushing gets loose in the bore.  I believe that Liebherr may be onto something with the tougher filler metal.  I think the reasom my repairs don't last as long as factory is the 70 wire may be softer and the material mashes a little over time and lets the bush move?????   Anyway I am going to try 100 series wire the next time around and see what happens.6 Miller Big Blue 600 Air Paks2 Miller 400D6 Lincoln LN-25's4 Miller Xtreme 12VS2 Miller Dimension 812 4 Climax BW-3000Z bore welders Hypertherm 65 and 85Bug-O Track BugPair of Welpers
Reply:Thanks ExpatWelder,this is getting very informative. So Leibher actually OK the use of mig welding on ductile iron bores ?When you say 100 series wire, that would be something like 100S-6 ?Keith.
Reply:Keith, Expat,Ductile iron can have a wide range of strength, ductility, and toughness depending on the chemistry used in the iron, the casting process, and any heat treatment applied after the casting is made.  This link has some good stats that will illustrate what I'm saying.  See Table 5 on Page 2 of the link below and compare the tensile, yield, and elongation values.  You don't have to plow through all the engineering mumbo-jumbo to see that ductile iron strength and ductility can vary greatly.http://www.mid-atlanticcasting.com/d...uide_FEB05.pdfExpat, I'm sure Liebherr's engineers know what they're talking about.  But what they recommend may not apply to every piece of ductile iron used in all makes and models of equipment.  Liebherr's recommendations are based on the fact they know everything about the ductile iron castings in their machines.  I'd say your past choice to use 70S-6 was the safe, conservative bet and while you may not get the max life out of repairs, you also dodge potential cracking issues when welding on ductile iron of unknown properties.Keith, I suggest the safest course of action for your repair is to stick with the 70S-6 wire and good weld pre-heat and interpass temp control.  The lower strength filler metal will be tougher; less brittle.  This will reduce chances of cracking.  I agree with Irish Fixit's comments and suggestions.  The nickel filler will work; but the cost for a small quantity just doesn't make sense in the big picture.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Thanks A_DAB_will_do,I've added that PDF to my file collection. Seems funny now that just a couple of weeks ago I was thinking that ductile iron is just some cheap cast iron used to make old water pipes.I guess I'm now in a state of acceptance that this building up with weld on ductile iron bores does get done and machines aren't falling into several peices because of it. I wonder if these pre-heat, interpass heat, etc actually get used on these jobs, especially when you've got the line boring bearings set up in place. All the theory seems to say not to do it because of the brittle / weak transition zone, which could potentially lead to cracks starting and travelling. Yet life in the real world is proving it's working.
Reply:Originally Posted by mancavedwellerI've lined bored my excavator swing tower. It is made of ductile iron so I sleeved it instead of building up with weld and boring out. (snip)Everything I've learned about welding cast iron stresses at least plenty pre-heat and maybe even post heat. I've seen how weak the welds are on cast iron if not done properly. A knowledgeable member on another forum puts cast iron parts in a furnace after welding to "make them behave" (his words LOL). I take it this is to anneal the brittle and weak heat affected zone, and bring back the toughness.
Reply:Hi Matt,thank you very much, that info makes a lot of "metallurgical sense" to me. However I thought the cracking would come from the "flexing" of the ductile iron together with the hard/brittle transition zone. I had no idea about different expansion and contraction rates of the CI & weld metal purely through temperature change. That means potentially cracks could start even when there's no load on the part, but put temperature changes and load together, and it's even more possible.I knew it was you that posted the info on putting the parts in a furnace but didn't want to mention you by name in case anyone would be in disagreement with your method.I'm very glad you posted here because it never crossed my mind about a weld build up repair only being good for one time. Of course the next time the repair needs doing you can't bore out to that diameter again because of the hardened transition zone. That wouldn't make a customer very happy when second time around the line borer tells him it's impossible to bore out. Good point and very valueable information.Keith.
Reply:Originally Posted by Matt_MaguireThat would be me, and those are re-man parts for tamping machines. The CI ends up losing strength with the recipe I use for the thermal treatment but for this purpose it doesn't matter. There is a lot to the story on how I settled on the method but the the short story was economy, in '93 they were $450.00ea new with 4 parts needed on a machine & I could re-man all 4 for $450.00. There were thousands of the machines running with 2 year re-fit cycles out there - do the math. The OEM hates people like me...For your purpose you did the right thing. While a 2 pass steel filler solution will allow machining - any further reclaim of the part would be near impossible. You will also get fair underbead cracking because the CI is stiffer at any temp than steel & they don't shrink & grow at the same rate (the CI is sluggish at moving with temp changes). Brazing works well with CI because it "upsets" when the CI grows & "stretches" when the iron shrinks & they both stay happy.If I am going to sleeve ductile iron I either want steel sleeves in the 40-50RC hardness range or CI ones of similar strength.Wayne, you kinda knew that was gonna happen didn't you!  That CI stuff gets pi$$y when you weld on it for sure. The nickel will stick two pieces together pretty good & I get the whole money thing for sure.What's happening Expat! If you are opening up the bores before welding on those machines going to LA-75, LA-90 or LA-100 wire gets you to 90, 100 or 110ksi strength (but maybe not hardness needed).  When working with E70s-6 (all filler metal bore) then the best you get is 80ksi. If you could get Liebherr to pass along the material to you I can pass along some recipes I've developed.If they are using 4130 or a similar strength lower carbon/low alloy HT castings & I have the DI (ideal diameter) spec'd for heat treat & quench I can give a rifle shot recipe for strength & hardness. Roller quenched plate like T-1 the recipes are not so good but still pretty good...Good luck all,Matt
Reply:Hi Expat,Well as a relative beginner to all this I'm left with more question marks than answers. Everything I've read or been told about the effects of welding on cast recommend against building up CI bores, and give reasons why it could potentially be a cause of failure.I'd love Leibher to give an explanation of why it's OK to build up CI bores, why the hardened transition zone will not be a starting point for cracks, and why the differing rates of thermal expansion between the CI and build up weld will never cause cracks. Is getting away with building up CI bores (and the machine not falling to peices) more due to there still being sufficient strength left in the original meat of the body. Are there cracks unknowingly occuring at the transition zone but they don't progress into the ductile. At this point in time it seems it shouldn't get done, but does get done, doesn't break so it's OK. I think a future client would run me off site if I gave that reasoning for doing something.I accept it does get done and the part doesn't fall to peices, I'd just like to understand why it's OK to do it this way when all the literature, etc seems to says otherwise. I feel like an apprentice that's being told to forget all the proper procedures and just do the job.Keith.
Reply:I don't really have an answer for you mancave............It's not just Liebherr.  I have welded up bores........literally thousands of them, on every brand of machine you can think of.......In the maintenance world that's pretty much the standard way of doing it.  Sometimes when I have multiple large bores to do we use plain ol 7018 and weld across the bore.......saves a little time when I can throw 4 or 5 guys on 4 or 5 holes versus setting my bore welder up and doing one at a time.I have noticed that when I weld a hole up multiple times, like when I am training somebody on a scrap piece in the shop, after we have weded the hole up and cut it out soay 20 times, I get alot of underbead cracking, almost to the point of the weld material just about will come out in one piece once you are done..............other than that I have Zero problems.???6 Miller Big Blue 600 Air Paks2 Miller 400D6 Lincoln LN-25's4 Miller Xtreme 12VS2 Miller Dimension 812 4 Climax BW-3000Z bore welders Hypertherm 65 and 85Bug-O Track BugPair of Welpers
Reply:Originally Posted by mancavedwellerHi Expat,Well as a relative beginner to all this I'm left with more question marks than answers. Everything I've read or been told about the effects of welding on cast recommend against building up CI bores, and give reasons why it could potentially be a cause of failure.Keith.
Reply:I am by no means an expert on the metalurgy involved and will not comment on the welding processes.  But I am experienced at fixing stuff that fails periodically from normal (and often abnormal) wear.  I like the idea that you bored then sleeved the hole.  Future repairs should be simple enough - push out the sleeve and push in a new one.  In this way you need not be concerned with problems caused by repeated heating and welding of the original casting.- MondoMember, AWSLincoln ProMIG 140Lincoln AC TombstoneCraftsman Lathe 12 x 24 c1935Atlas MFC Horizontal MillCraftsman Commercial Lathe 12 x 36 c1970- - - I'll just keep on keepin' on.
Reply:Hi Expat,I appreciate all your input and I hope I don't come across as pushy, it's not that at all. I'm probably just more of a worrier and like to understand the why of everything. I sometimes think while everyone else is just getting the job done, I'm researching how to do it. I think I'll be hunting for your threads, your jobs look pretty amazing.Hi Matt,by the way I'm not a funny speaking Ozzy, I'm a funny speaking POHM (prisoner of her majesty as the Ozzies call us ). I just couldn't bear our crap English weather any more and left to find work in the oilfield in Asia, ended up living in Singapore 6 years (while working in Indonesia) then moved to Australia. And to think someone back home said I would get sick of the Australian sunshine, hasn't happened yet.I could be completely wrong but my experience to date with Kitty is they make lots of money on NOT making parts repairable (at least on my little machine, maybe it's not worth their while to sell parts for a pump or motor on a tiny machine). I needed an output shaft for the slew motor, they only sell the complete motor. I needed a $10 seal for the main pump, they only sell the pump ($1100). Needed two small shafts for the track drives they only sell the drive units ($8000 for a pair), etc, etc, etc. Wouldn't surprise me if making the swing tower out of ductile is an attempt to dissuade repairs, and just purchase a complete new one.Hi Mondo,thanks for the heads up. My main reason for using sleeves was that I don't have any bore welding facilities. I didn't realise the part was ductile iron at the time or even understand exactly what ductile iron was when I started (that's all changed now ). It had actually been recommended NOT to sleeve and build up with weld but I think that was under the assumption of the part being steel. However, I do love the thought of just pressing out old sleeves and pressing in new ones down the track.Keith