cracking problems--any suggestions?

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I've taken on a fairly large repair project, and have been having some problems I haven't seen before. I'm working on a Hitachi excavator and am rebuilding one of the frame sections that one of the drive tracks rides on. The whole thing is rusted out, so I've had to cut out pretty much all the steel and insert new steel. The problem that I've run into is that some of my root passes have been cracking. I'm using 6010 rod for the root and some intermediate passes, and 7018 for cover passes. I'm used to seeing crater cracks at the end of a bead sometimes, but these have been longer than just crater cracks. I see them mostly in vertical beads, and mostly where I'm joining new mild steel to the original steel. I figured that maybe the original was an alloy of some form or another and that was causing it, but the last sections I just finished I had cracks where I was welding mild steel to mild steel. Also, one of the beads that I had problems with was in the flat position. I think part of my problem is that I can't turn the current down as far as I'd like on the machine I'm using. If I turn the setting down too far, I have a problem with the arc going out; the rod doesn't stick, the arc just stops. Since I have the heat up higher than I want, I end up moving faster than I want and I think the bead comes out thinner. That's the only thing I can come up with on my own. I've never had a problem with 6010 welds cracking like this. Anyone have any suggestions? This has caused some serious problems for me and I've spent way too much time grinding out cracks.Another question: pretty much every root pass I did on the last section that I welded cracked. I ground out the cracks, but not the entire weld every time. Am I looking at having cracks, if any were left in the root pass, propagate through the enire weld. I inspected all the root passes I did throughout this project and always ground out any cracks that I found, most all of which were just small crater cracks. Also, all the root and intermediate 6010 passes were ground smoother for the 7018 cover passes, and I didn't see any cracks. I'm wondering now though after dealing with this last section if I missed some. If I did, are these cracks necessarily going to propagate through the rest of the weld? Does anyone have any experience with this sort of repair job and seen this sort of cracking problem? Any help would be greatly appreciated
Reply:you cant just keep welding over cracks especially with stick step 1  wherever the crack is... grind it out as deep as you can..from about 1/2" before the crack to 1/2" after..only concentrate where the crack is..and re-weld if it cracks again..then repeat  step 1gotta get to the bottom of the problem...eventually you'll get what your after..but you must grind out the crack area before every pass..and i'd use 7018..so carry on!...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:I'm with zapster on this. Get rid of initial crack completely. Goughing is alot quicker than grinding if you have access to the gear to do it. Forget the 6010's and weld with the 7018's. Personally, I only use low hydrogen electrodes for earthmoving and heavy equipment repairs. My guess is that if you have welded over the top of cracks they will re appear.
Reply:Well, everything is already said... Good luck!My Babies: HF Drill pressHF Pipe Bender3   4.5" Black and Decker angle grindersLincoln Electric PROMIG 175that´s it!
Reply:How thick of a material are you welding and how is the joint prepped? I'm assuming a dc- setup, but just to make sure. Check that your grounded securely and as close to the work as you can get it. And to clarify, you are having this problem only on the 6010, and intermittently throughout the weldment, primarily in the root passes?Can I ask exactly the 6010 rod you are using and are you using a smaller diameter rod for your root? Do they appear to be welding well otherwise? I've heard Lincoln 5p rod is moisture-finicky; too wet and your arc gets messy and the flux boils, too dry and you start to loose the coating near the end of the rod and your arc becomes hard to control as well. The usual answer here is exactly what the fellas recommended, ground it out completely and start over. Sounds like you might have something else going on here though, so post back with as much specifics as you can stand and let us look it over again.If you don't have the time to do it right, then you definitely don't have the time to do it over.
Reply:How thick of a material are you welding and how is the joint prepped? I'm assuming a dc- setup, but just to make sure. Check that your grounded securely and as close to the work as you can get it. And to clarify, you are having this problem only on the 6010, and intermittently throughout the weldment, primarily in the root passes?Can I ask exactly the 6010 rod you are using and are you using a smaller diameter rod for your root? Do they appear to be welding well otherwise? I've heard Lincoln 5p rod is moisture-finicky; too wet and your arc gets messy and the flux boils, too dry and you start to loose the coating near the end of the rod and your arc becomes hard to control as well. The usual answer here is exactly what the fellas recommended, ground it out completely and start over. Sounds like you might have something else going on here though, so post back with as much specifics as you can stand and let us look it over again.If you don't have the time to do it right, then you definitely don't have the time to do it over.
Reply:You are welding a highly restrained unit.  Preheat might be wise.  It doesn't have to be a lot.  I would try for at least 200 F.  It sounds like your first welds are the ones that are cracking.  Likely you are putting heat into a relatively cold area and it shrinks back and cracks the partially welded joint.   Without exception anything over one inch thick MUST be preheated.... unless you want to do the job over and over and over.
Reply:Lotechman is pointing you in the right direction. If there is no place for the weldment to move when the weld shrinks, then it will crack. #2. Is the piece you are repairing a casting or a fabricated piece?#3. Unless you have open roots, I would use 7018 for the root as well. You are using a lower tensile electrode to start with: 6010. This could give you problems, especially if it is a casting.#4. Preheat is a must as well.I did a lot of repair work on machinery in days gone by. Crawler cranes, rock crushers, bulldozers, and the like. We never used any filler less than 70K tensile.
Reply:Originally Posted by DetailerDaveLotechman is pointing you in the right direction. If there is no place for the weldment to move when the weld shrinks, then it will crack. #2. Is the piece you are repairing a casting or a fabricated piece?#3. Unless you have open roots, I would use 7018 for the root as well. You are using a lower tensile electrode to start with: 6010. This could give you problems, especially if it is a casting.#4. Preheat is a must as well.I did a lot of repair work on machinery in days gone by. Crawler cranes, rock crushers, bulldozers, and the like. We never used any filler less than 70K tensile.
Reply:Thanks for the replies guys.The new plate I'm welding in is 3/8", the existing that I had to leave and that I'm welding to is 1/4" to 3/8" after being wasted away. The new plate is mild steel, the existing steel is unknown, but seems to be mild steel, maybe a low alloy. Nothing cast.I'm using 1/8" Lincoln 5p, and 3/32" and 1/8" Lincoln 7018 H4R.I haven't been pre-heating except when I'm doing 7018 first thing in the morning.Have only had the cracks in the 6010 root passes. All the intermediate and cover passes have been sound. Haven't had cracks in all the root passes just a couple until this last piece where all the root passes developed cracks.I'm sure moisture will be somewhat of a problem, but I didn't think it would affect the 6010 rod. I'm in the Florida Keys and it's pretty humid here. The guy I'm doing the work for doesn't see the need for a rod oven since he's got a wooden box with a light bulb in it.All of my joints are V-grooved with about a 1/8" thick root face. I fit them up with a 3/32" to 1/8" gap. I was using the 6010 rod in an effort to get a 100% penetration weld like I'm used to doing with v-groove butt weld pipe joints. All of my welding experience before this project has been aboard ships, and about 40% of that is pipe welding. I've always had a hard time getting 100% penetration with 7018 -- I either burn through or my keyhole closes up. Where I found cracks I ground them out completely, but after all the cracks that I had in the last section, I became paranoid that I might have missed some in the earlier sections. However, I've been thinking that the piece that I had the large number of cracks in was the last piece to be welded in, so there was no movement in it. I'm still concerned with the cracking though, because I'd like to think that I can do a 6010 root pass on a rigid structure and not have it crack. Maybe not. Thanks again for the help and any other thoughts would be greatly appreciated.Last edited by me37; 11-20-2006 at 03:51 PM.
Reply:Sorry for the double post, don't know what happened there. One more question: is the cracking centerline of the bead or along the edge? Toe or HAZ-cracking is an indication of hydrogen in the weldment and can usually be cleared up by sufficient preheat. Centerline cracking could be caused by things such as cocave bead, softer metals in the base material migrating into the bead, etc. Make sure the rods are dry, trying a fresh can could clear it up right there. Good luck!Last edited by Clanweld; 11-21-2006 at 11:12 PM.If you don't have the time to do it right, then you definitely don't have the time to do it over.
Reply:I weld on hitachi equipment and in most cases they use mild steel with the occassional t-1, So throw away the 6010 buy some 1/4 x 1 flat for backup strip and your problems will go away. Also preheat can never hurt especially since you mentioned humidity chase that moisture out. Also if you ever have an issue or a question about how to weld a piece of equipment contact the dealer they have updates and weld procedures for most applications.http://www.hitachi-c-m.com/http://www.hitachiconstruction.com/e...hitachi_const/
Reply:Originally Posted by mla2ofusDD,did you ever have the "pleasure" of gouging out and welding up a crack in a roll crusher shell? I think that's why I have an intense dislike for an airarc to this day. If somebody asks me if I know how to use one I say"Nope, never learned how".                 Mike
Reply:Thanks again for the replies guys.The cracks were centerline, and I figured they were likely from a concave or thinner than optimum bead. Like I said, the machine I'm using is old and beat and I can't get the current turned as low as I'd like, forcing me to move faster and producing a thinner bead than I want.This project was a bit of a learning experience for me, not having done any real large project on heavy equipment before. This project was one of the two track frames, so when I go to do the other side I'm going to adjust. I was going about the joints on this side the way I butt weld pipe, but on the next one I'm going to forgo the 6010 and use just 7018. I'll just have to practice getting 100% penetration welds with the 7018. Thanks again y'all.
Reply:Just for the record - you mentioned that you were using 1/8" rods - and you couldn't get the amps as low as you want  -  what amps are you using?Here in the Great White NorthMosquitoes can't fly at 40 below
Reply:The dial on the machine shows 80 amps, but it acts more like 90 or so amps. The mark on the dial is just a paint mark that someone put there, and I don't think it's that accurate. All the other settings seem high too. If I turn the current down below 80 amps with the 1/8" 6010, the arc just stops whenever I move the rod a little too much. And it doesn't take much movement to lose the arc.
Reply:Hitachi recommends either using a back up strip or back gouging to produce a 100 % welds, The filler metal is 7018 or wire equivilant.Depending on ambient temperature there is no pre heat for 3/8 plate. I am trying to get you to focus on this info we have much larger shovels and are dealing with thicknesses ranging from 1 1/2 on up to 3 inches. Also have you ever taken into consideration the fact that 7018 is performing better than the 6010 is the slag helps keep the cool air off of the weld while solidifying?
Reply:Dipper Welder, Thanks for that info. I've never considered using back-up strips because I was taught for pipe welding that it's kind of cheating -- you can do it, but it's better if you don't use them. If Hitachi recommends them though, then I will stop trying to make my life more difficult.Back gouging isn't an option for the majority of the welds. It's a box shaped structure and I can't get to the back side. The joints that I could get to the backside worked well because I didn't need to try to get 100% penetration, so my gaps were a little smaller. I just ground the backside with a die grinder. The welder I'm using is only 250 amps and doesn't really work with the air arc equipment.I'm not sure what the original thickness of the material was. Everything I cut off was paper thin. This guy's equipment works and sits in seawater most of the time and doesn't get rinsed off. I'm surprised the thing was still operating at all.By the way, how is the quality of the welds on the Hitachi equipment usually? Alot of the welds that I was planning on butting up too I ended up having to grind out completely because they were completely honeycombed. It looked like they found a way to weld with soap suds.Happy Thanksgiving.
Reply:Most of the welds we cut into for repairs are sound, sounds to me that maybe they where having problems and didn't catch it right away. I have seen porosity in Dresser truck frames and Catipillar Equip as well.