Weld or Braze cast?

admin

Greetings all, I've lurked here for a while. An unsuccessful search has lead me to making my first post. Just for introductions, I would rate myself as an experienced home welder, stick and MIG, on mild steel. I'm OK on the "plain jane" stuff, but specialized processes and metals are beyond my experience. I'm having a little trouble figuring out how to repair this bearing holder for an electric motor. The motor fell over backwards and broke the bearing holder into four pieces. Red lines in the pic show the breaks. I've got all the pieces fit back together good, just need to find a way to hold them there. The piece is cast....something. The metal is magnetic. Gray color in the center. It will make some sparks when grinding but not too many, dark red/yellow if I recall correctly. I think it is cast steel, but not sure. I took it to a pro welder and he thought it was "weldable" but I didn't get the warm fuzzy feeling from his assessment. Cool guy and all, just wasn't 100% in the answer. This piece doesn't really have any movement or handle any tourqe. It just holds the end of the motor amature centered, so distortion is a concern. It's machined to fit inside the motor case, so expansion is a concern. I'd like to have the pro welder TIG it, but not sure if it will hold or if it will crack again. He mentioned nickle rod or even just MIG. I also thought about brazing it.    What say ye great minds? What kind of metal do I have here and how do you suggest I fix it.Thanks for the input, Nathan Attached Images
Reply:Take a real small drill bit and drill a real small hole somewhere non umportant on the piece.  If you get chips (looks like long ribbons) it's probably steel.  If you get powder it is probably cast iron.  Hopefully it isn' t that pot metal crap.You can weld cast iron with high nickel rod.  Pot metal is almost impossible to work with I think."Any day above ground is a good day"http://www.farmersamm.com/
Reply:Howdy Meat man, From here, by the look of the radius at the flange, and the grain near the windings I'll bet on cast.I'd say the only way to go is a heavy vee and braze.Good LuckOops, never mind.I missed this: Originally Posted by Meat man . . .What say ye great minds? . . .
Reply:Originally Posted by Meat man   . . .What say ye great minds?
Reply:For that repair I'd use AllState 4-60 Nickel rod.  Best cast rod I've ever used to repair stuff like that.  3/32" size.You are going to dismantle the motor, aren't you?  You might get lucky welding it assembled, but the innards have to be protected real good from any arc spatter.  I'd only weld that in the FLAT position, hence the concern about screwing something up internally.After dismantling, bevel the cracks at least 1/2 the thickness of the web.  If crack isn't all the way across the web, do as Sam said and "stop drill" the ends of the crack.Preheat, and weld intermittently.  Don't weld all the cracks at once.  Weld one and allow it to cool to a point you can lay your hand on it.  Weld a little more, repeat.  Peening the weld bead between passes will help relieve welding stresses also.  Cast Iron has virtually no ability to stretch (ductility) as the bead cools and shrinks.  This is where most cast iron welding repair failures occur, along side the weld at the heat affected zone.  Welding all the cracks at once could really warp the housing, and your armature won't spin properly.  If it's possible to clamp the webs to prevent distortion, do so.I once had a large HP electric motor housing cracked in a shop I ran in Korea.  Took one of my Korean weldors almost a week to do the job, using the weld a little, cool a little method.  Like I said, it was a humungous motor, very expensive to replace.Good Luck.
Reply:Sounds like you have some gray cast iron. I personally like to weld cast, and I use nickel rod. Preheat is very important, but so is what you do with it ater welding. I have a tub of play sand which I will bury a hot freshly welded piece of cast in. Not a bad idea to heat up some scrap steel and bury it in the sand to heat the sand up too prior to welding your cast. When you cool your casting in the sand, it slows the cooling rate big time, thus making the casting a bit more ductile. Vermiculite will work too. I know a guy who has an old stove in his shop that he cools a casting in. He cranks it way up and turns it down 50 degrees an hour. He has never had one break. I have never had one break either using the sand.only thing worse than an ugly woman is an ugly weld
Reply:Brazing will have the least distortion and residual stresses. We have been brazing and fusion welding cast iron castings for over 100 years, this high nickel "stuff" has really only been around for about 40 years as a "quick and dirty" alternative. I have seen brazed parts in service 50 years after the repair was made, and arc welded jobs fail like crazy.
Reply:This is how I was taught, and it is only another method, I have not tried any of the other methods because the only place I worked at that repaired cast Iron was where I learned this from, so we had to do it their way. I never saw anything fail, the owner even repaired some old/rare Mopar block that had cracked from being frozen.Again this is only another method, not right, wrong, better or worse, just what I knowWe never preheated the part, because cast iron has so much carbon in it.We would bevel out the crack and weld the joint with TIG using NiCu7 filler rod, more copperin the rod than you normally see.When welding it we didn't completely melt the base metal, we melted some of itbut didn't get a big fat puddle going, then add filler. So some of it was welded but technically other parts of that same little area were brazed (the base metal never melted)We would weld about 1/2" to 3/4" then stop and peen joint very well. we had old center punches with handles welded on them, hold the point exactly where you want to peen and strike the punch with a hammer. Every visible part of the weld was peened.Welding just a little at a time and keeping the thing as cool as possible.So there are a lot of similarities with other peoples methods, this one just stressed keeping it cool.The guy who I learned this from was a weld engineer at Allis-Chalmers for a looongtime and holds several patents for welding process'Yup
Reply:Pa seemed to hit it on the head. But without knowledge of the metal type it had to make a absolute dead on choice. 1st I would try to take the housing apart to make sure the bearings and armature are out of harms way during weling.  Try to get some high grade ni/cu rod we use that the most on repairs similiar to what it appears you have. If you don't have a machine that can do the job a brazing job will work.If you go not feel comfortable doing this this my recommedation is pay the bucks and have it done by a professional.Last edited by specter; 02-14-2009 at 10:00 AM.Co-Own CNC shop:Miller :1251 plasma cutter, MaxStar 700 TIG/Stick, & XMT 456 Multiprocess Welder.&  2 Hypertherm HPR260's Plasma CutterSorry I had a bad stroke but now I am back.
Reply:I've used Nickel, and Nickel-iron rod for cast iron parts like handles of old post drills, used both  Cu-Ni and Ni-Cr for welding 416 cutouts to the bottom of both stainless and cast iron pipes, etc, etc, etc,.The point here is that although a number of good methods and materials exist which an experienced welder can use, the OP doesn't have much experience in this area so may want to either use the safest/easiest method, or do enough practicing that he won't have a problem on his motor repair.Also, the nickel-containing rods tend to be expensive and only come in larger amounts in many shops; since they aren't allowed to 'break' packages in most places anymore, that may limit selection too.
Reply:i would braze it.  heat the part to burn out the oil, vee it out, flux it and braze away.  doesn't matter that metal it is.
Reply:I did a little investigating. I drilled a 3/32" hole, I got a little bit of powder but mostly small V shaped chips. Looked a little like the chips that come out just before a long ribbon of swarf when drilling mild steel. I also ground on it a little. I used a fresh grinding wheel in my 4.5" grinder (regular hard wheel, not a flap wheel) and a 3" pneumatic cut-off. I got orange colored sparks. I don't really what to disassemble the motor because the windings are built into the case. This thing is 40-50 years old and I'm nervous about getting it apart. I'm actually using the windings and armature to center the bearing. I found that one wrap of duct tape and a couple of masking tape will center the armature in the motor perfectly. I had planned to stuff a couple of old gloves under the piece to be fixed and cover with welding paper, but I'm not sure that will protect the inards from the heat of either process. I was actually thinking about JB Weld on both sides, but I didn't want you to laugh me off the board. I had already planned to attach a guard over this piece (attached to the case) to protect if from future tip-overs. Thanks for the input so far. How do my latest findings change the situation?
Reply:jb weld.....somebody bring a rope.nothing's changed.  braze it.there is a couple videos on youtube about brazing.  take a look at them and you will see the basics.Last edited by Scott Young; 02-14-2009 at 07:38 PM.
Reply:Your top photo clearly shows two screws (on top) going into the main housing from the end bell, and two more holes below where screws should be. If those are removed, the end bell should separate from the main housing so you can weld or braze without hurting the motor windings.As I stated earlier, if the parts fit together well and you won't be abusing the motor again, I think JB Weld would  make an adequate repair. You didn't answer the question about being able to get similar scrap to practice on; if you can do that, you may find, after some practice, that you can do a better than 'adequate' job, by brazing or welding it as suggested here by many. Once able to do that, you''ll find lots of similar jobs/projects that require it and....don't tell the neighbors, or you'll never have any free time.....
Reply:I did a little practicing with brazing this weekend. I watched several youtube videos and read some articles. I was able to make several adequate repairs on some scrap (not cast, but several different MS items) even tried my hand at some OA welding with coat hanger. It wasn't pretty, but it stuck - almost zero pentration...but at least I tried!I preped the casting yesterday and plan to braze it tonight. Oldiron2 - I should have explained a little better. I can remove the bearing holder from the motor, I was just worried about removing the windings from the motor (if I was going to leave the holder on the motor case during repair). When I decided to braze it, I decided to remove it from the motor to allow pre-heat, so no more worries.
Reply:Cast iron can behave  differently than mild steel wrt wetting ability of the bronze. I would try to find some cast iron to practice on, just for more experience, if possible.
Reply:Well for better or worse, the deed is done. I didn't have any issue with brazing the piece, except not knowing exactly what is good and bad. I guess I braze like I weld - gorilla style: big, strong, and UGLY. I think it will hold, but it aint much to look at.  I preheated using my charcoal BBQ with low coals about 300* (so I didn't have to explain use of kitchen oven to the boss). After I was done, I put it back in there to cool slowly because I didn't have any dry sand.When I was test fitting, I got a little heavy handed with the piece and it all fell apart. I decided not to let that happen again, so I put on some light tacks with my MIG. It worked, but one cracked and several had bad porosity. I V'ed the cracks with my 3" cutoff and then opened up the edges a little with the die grinder and a stone. I noticed that the center piece was a little bowed in, so I made a small fixture to hold it in place. I had to pre-load the piece from behind. I drilled a hole in a plate and welded on a nut, bolt through the hole. I put another piece of plate behind the center piece and turned the bolt out to put some force on it. Like they say, picture is worth $1000 words. Thanks for the help! I won't claim victory until I test fit the piece and the motor runs, but I'm closer. Attached Images
Reply:Looks as if the brazing worked well, if you were able to keep the bearing area properly  aligned. Now we (I!) need to see the rest of the motor, especially the Brass plate. How old do you think the motor  is, and what horsepower?BTW, now you need to clean up and polish the brass in the weld area, just to get it to sparkle. I like brass; guess you can tell that.
Reply:Lookin' good Meat Man!Nice fixture too.Good Luck
Reply:Well, a big THANK YOU is due to all here. I declare success on this repair. I got everything assembled and wired up last night (in the heated comfort of the dining room, thanks to the recommendation of my loving wife). I was able to hold the armature almost perfectly centered. I have .010" air gap on the bottom and about .015" on the top. Duct tape works wonders!The brazing is still UGLY, but it holds. Bearing alignment is pretty good, but does require a little care during assembly or it will bind up. Going to do an amp draw on it tonight, but physically it is fixed. As requested, here's some pics of the finished project. This is a Hobart 200-A bowl mixer, originally used for baking and industrial kitchen work. I use it for mixing sausage meat. For the 1-2 times a year that I use it, hopefully it will last me a long time. Thanks again. Nathan
Reply:Forgot the pics. Attached Images