New to the forum and wanted to say hello before getting to the purpose of this thread. I've been welding on scrapers, loaders, dozers etc. for several years now, but a few days ago I was surprised with a jaw die (manganese) that needs to be re-pointed. Now, the company I work for has been selling manganese steel for a long time for jobs such as this, but I've yet to successfully re-point one here at the shop. My welder and I worked on one a few months ago, and we managed to warp it. The customer was still able to bolt it on and use it, but I was disappointed at the result. After this initial jaw die, I had hoped that we wouldn't get involved in the repointing of one of these again. This new jaw die is a lot smaller and thinner than the previous one, so naturally I'm going into this project with extreme caution. Do any of you have any experience re pointing jaw dies with manganese bars/plate etc.? If so, what method do you suggest? Any help would be greatly appreciated.
Welcome to the forum's Manganal-Steve.... boy, I've never heard of it being done b4... Columbia steel had cast a set of jaw dies for one of my primary's one and got the shoulders to low for the cheek plate's to tighten them , but the fix was just to tack a thicker strip along side to fix the problem.. those strips were broke off when it was time to turn the jaw's, the weld on held during the installation and once the cheek plate's were tight then couldn't come out anyways. I would imagine warping would be a main concern. If you successfully do this, please post your method here. We could save a few thousand dollars ... thanks ,, Grandpa.
Thanks for the welcome. I will post before and after photos as soon as we begin tackling that jaw die...
This is the previous one... It was really big, and managed to warp just a tad despite the way we tried to distribute the heat on the welds.
This is the jaw being re pointed.
Now, the customer was happy with the wear life on the manganese bars, not so much with the warpage... however slight it was.
Those look like new jaw's,,, are you pointing a new set?
That was a new set, and this one I'm doing now is also new.
Yeah the guy that hardfaces our rolls tried to build up a jaw die one time and he warped it also. I think he said they had to machine it back to square? Not any savings there. We use the diamond shaped dies around here. I would be very interisted in this thread as we use a Kue-Ken 30X42 jaw here and the dies cant be fliped. Dusty
How much of a build up? It seems to me that depending on the wear, re building one up might be more heat, and with less material to work with, the more likelihood of warpage.
Our dies are a different design than what is in the pics. Ours are flat with diamond shaped patterns in them. I believe what you working on is for softer rock than what we have? So adding tips is not an option. If I can figure out how to post a pic I will. Yes I'm sure that he had to put alot of heat in them to build it up to new. Dusty
These are not mine, but my pics won't load for some reason, it gives you an idea of what I'm talking about. Dusty
Can't these just be protected by adding a sheet of manganese? Shape cut, plug welds, rather than building it up?
What number rod/wire are you using for your application Steve?
I have a few questions: - 1. What temps are you using for pre-heat and post-heat and how long do you take to cool down the whole piece to ambient temperature after welding? 2. Are you welding with 2 welders simultaneously one working on each side of every bar? 3. Do you use needle gun scalers not only to remove the weld slag but to stress-relieve the welds after each pass?
grandpa, I am using 5/32" for the root pass, and I continue with 1/16" wire.
Nige, as far as pre-heat, we are only scurrying the water out. post heat, we throw a leather blanket over it so that it will cool off slowly. We did have two welders on the first jaw, but I found it that would have made the warpage worse than it should have. Yes, we use needle gun scalers to stress relieve the welds.
Thanks Steve. Personally I think I'd be pre-heating the whole jaw to at least 350 DegF (175 DegC) before starting to weld, not going above 450 DegF (225 DegC) interpass temperature, and when finished welding lag the whole thing in thermal blankets (heated if necessary) and cool it at no more than 50 DegF (30 DegC) per hour until it's at ambient temperature. Welding simultaneously with one welder each side of the bar should reduce the warpage IMO, not make it worse. Can you detect exactly at what point in the process the warpage is taking place..?
Nige, I don't think having two welders working on it simultaneously will keep it from warping, because you're just applying more heat to the same side of the jaw. If it was a situation where one welder did one side and the other the opposite side, I can see that working. I talked to a guy (old timer) that's done a few of these before (successfully) and he advised just the opposite. One welder, alternate welds, and do it slowly as to not allow the jaw to collect too much heat. He advised using only electrodes, too.
I can see your old-timer's point. Using electrodes you can only deposit a limited amount of weld per minute. Using a wire feeder you can possibly go up to anything like 4 times the amount of weld metal. Based on that then more weld metal deposited equals more heat. Heat could be the root cause of the warpage, therefore it makes sense. However pre-heatingup to a certain temperature then keeping the interpass temp within certain fairly tight limits, plus close control of cooling ought to stop the warpage. I'd be interested to hear what others think.
My recollection of my welding school days is no preheat for Manganese alloys. Its meant to be kept cool. Having said that I doubt that with the scale of that job its possible to keep it straight. Looks like it may have to be re machined after welding.
Thats what we came up with. Could not keep it from warping.. Dusty