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High Manganese Steel

Solidus

Aluminum
Joined
Jul 20, 2004
Location
Melb Australia
Anyone with experience with this ball breaking material?

A workmate has a tough job. He has to cut a LOT of material out of a rock crusher component on a VBM. The workpiece is a high manganese steel casting. Useing the 100* angle of a 19mm CNMG roughing insert he's taking .100" DOC at .036" feed, around 150 FPM. The noise could be mistaken for a tractor being dragged upside down along a pavement. :cool: Any increase and bye-bye insert. The feed was stipulated by the boss, but apparently he was only going off the machine finish of other parts. Could've been a light finishing cut he was looking at. Any pointers as to best practice?
I was also wondering whether it would be possible to get better metal removal, or less noise ;) , using a SC whisker ceramic insert. Any other suggestions welcome.
Vincent
 
Vincent

I've e-mailed you a couple of pages from a book, relating to machining austenitic manganese steel castings as used for crushers etc. It shows the recommended tool shape, with 12 degrees top rake and 7 degree front clearance. It recommends at least 10 ft/min but not more than 15 ft/min, DRY, 3/16" cut, 1/32" per rev feed. It recommends dry cutting to generate sufficient heat to keep the steel soft enough to prevent work hardening. Chips should come off bright blue (that part should be easy). The author makes the obvious statements about tool sharpness, rigidity, overhang.

I'll hold a glass against the floor tonight (UK time), and listen for the noise of dragged inverted tractors coming from below.

Afterthought: The book is old, and I think the details relate to 'super high speed' 12% Cobalt tool steel, even though TCT tooling is detailed elsewhere in the book. Hence the relatively low recommended cutting speed (and the possible need to endure the noise for ten times as long as with your current speed!).

[ 04-12-2005, 05:22 PM: Message edited by: Asquith ]
 
The WG300 SC whisker reinforced ceramic from Greenleaf is an amazing insert. Almost as amazing as .036" feed is :D

If you are able to cut it for a while with carbide, I'd think the WG300 would outperform that by quite a lot.

Is this an interrupted cut?
 
Try machining high manganese stainless! We get a lot of Nitronic 60 (8-10%) and S2400 series stainless bar and some duplex stainless castings. The only high mn steel that we machine are forgings for some ultra high pressure stuff (50ksi). Then try tapping or threading!

First of all, your surface footage is a little fast. We'd probably start at around 120 sf/m on a casting. Your feed rate looks about right, but IMO, your DOC is big. Maybe 0.075".

Your set-up has to be extremely rigid on a VBM. We'd probably use a SNMG 643 with a 15deg lead holder.

AIK, the floor in my office shakes when we run a big casting on our 108" Gray. It's 50' away and sits on a 6' thick iso pad.
JR
 
remmember only 50 to 60 % cutter engagment this really can make all the diffrence on these wear risistant steels. this over came a larger part of our problem on clamshell grab parts. ps forget 75 thou feed a tooth this is way to much for any rotory cutter on this grade matirial, use a finner tooth pitch to get the same feed and stock removal as you clearly have the horse power.
 
Sturm Ruger uses many manganese steel investment castings in their firearms. Investment castings are used to minimize machining, apparently for good reason.
 
Well Ray tried SC whiskered inserts, both 16mm button and CNMG 12 at .008" feed and around 300 fpm but couldn't get tool life. The job was finished with carbide, closer to JR's settings.
JR, I would NOT like to have to tap his stuff! :eek:
Asquith, I hope you didn't need a mop! Thanks for the email. That grind could be interesting with a large stellite tool perhaps? Can you still buy the stuff? I'm thinking that with the lessened cutting pressure, a much larger cutting depth could be achieved, making up for the slower speed. We'll probably never get the chance to find out.
Lathefan, we're talking around 2 tons of metal. That's a lot of wax! :eek: Thanks all.
 
Solidus,
We run a lot of casting in the 10 ton range.

We are the largest user of Stellite (alloy 6) in the US. Somewhere in the 1,000 lbs per month range. We machine a bunch of it. We also buy a lot of solid alloy 6 castings. Most of the alloy 6 that gets machined is either a sealing or bearing surface and requires a 16 finish or better.
JR
 
JR, the more I hear about your workplace, the more I like it!
I guess your cutting with CBN on that stellite? I could imagine getting paranoid about keeping ways clean. That must be some abrasive grit.
Do you use any stellite cutting tools or are the redundant?
 
No CBN, and very little ceramic. The Kennametal man does stop once a week. Stellite is not that hard, in the 35-40 Rc range. Just machine is with a good grade of carbide. Most of the guys don't mind machining Alloy 6 as much as Hastaloy or K-Monel. Probably the worst stuff we have to machine is single point threading Nitronic 60 - high Chrome, high Nickal, and high Maganese.
JR
 
Super late to the game here, but I was a freshman in high school in 2005. Now I work for a dredge pump manufacturer and all of our pumps are made from either A128 manganese or A532 chrome irons. In the past two years I have put a lot of time into tooling research and development to increase production, and have gotten milling, turning, and signal point Acme threading down. I can't share everything, but Green Leaf ceramics are worth their weight in gold after finding the sweet spot. Facing A128, we can do .075" doc, 0.030" ipr, at 225 sfm, with light interrupted cuts lasting around 20 minutes a pass, turning the insert after about 20 to 30 minutes of cutting. We could push harder but the castings are sometimes unpredictable.
 
repair of this stuff

Super late to the game here, but I was a freshman in high school in 2005. Now I work for a dredge pump manufacturer and all of our pumps are made from either A128 manganese or A532 chrome irons. In the past two years I have put a lot of time into tooling research and development to increase production, and have gotten milling, turning, and signal point Acme threading down. I can't share everything, but Green Leaf ceramics are worth their weight in gold after finding the sweet spot. Facing A128, we can do .075" doc, 0.030" ipr, at 225 sfm, with light interrupted cuts lasting around 20 minutes a pass, turning the insert after about 20 to 30 minutes of cutting. We could push harder but the castings are sometimes unpredictable.

if you want real fun try putting a taper pin bore in a piece of this stuff that is 100 years old that had the outer casting broken at the pin hole for about 20% of the hole. we welded it ok , the trick is to do it cold with high manganese rod. grinding and keeping it below 500f took time. the drilling and reaming part was a nightmare. slow slow speeds and it ate the best cobalt tooling we could find. just keep at it taking a big bite works better than a little at a time, you will break some tools doing it this way, cost of the job. it had to be done in place to get it straight. the repair held up for 5 years but the machine had a building burn down around it this winter. i am doing a rebuild on it now .i have to deal with a bad babbit bearing in a weird casting next, probably i will be in another thread by the time i am done.
 








 
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