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doctor demo
11-24-2010, 12:33 AM
I have a project that includes milling some 1-1/2" thick abrasion resistant plate.
The pieces have been water jet cut and now have to be finished to size.

I have torch cut, welded and punched a r plate in the past but I don't have any history machining it.

Any suggestions would be appreciated.

Steve

3jaw
11-24-2010, 10:29 AM
I used to work in a shop that made material handling gates and we used A.R. plate for the wear surfaces. A.R. is a pain in the you know what to machine. Use carbide tooling and oil and it won't be as bad as HSS. It will work harden very easily so make sure you are always making chips and keep the cutting speed down.

Evan
11-24-2010, 11:39 AM
It depends a lot on the particular grade of AR plate. Some grades are marginally machinable but others are not. The work hardening is instantaneous when the material is pushed beyond the yield point by any means. Waterjet cutting is a good choice as it won't have produced general hardening but unless the plate is in the fully annealed condition you may not be able to machine it.

Annealing AR plate requires that it be heated above the Curie temperature and soaked there for long enough to ensure that all of the cross section is up to full temp. Then it must be cooled at an extremely slow rate with no sudden changes in temperature until it is below about 300F. The cooling rate should be no faster than about 50 dgrees per hour which means that it should be cooled over a 48 hour period for best results.

I have had sucess using my wood burning stove to anneal AR steel. Build up a big fire with the plate near the bottom and then let the fire burn to a large bed of coals. At that point open the drafts to create maximum heat from the coals and keep the fire stoked with only a small log one at a time to prevent to large a bonfire in the stove. After a few hours of this let it burn to a hot bed of coals again and throw a layer of ashes that you previously cleaned from the stove on top of the coals to bank the fire. Close it up and come back a day later.

If you don't have a stove to use you can get the same result with a barbeque pit and some regular charcoal. A shop vac will produce a nice blast of air to approximate a forge and get the plate up to temperature. Once up to temperature throw some fresh charcoal on the coals and cover the pile with dry sand.

doctor demo
11-26-2010, 01:54 AM
It depends a lot on the particular grade of AR plate. Some grades are marginally machinable but others are not. The work hardening is instantaneous when the material is pushed beyond the yield point by any means. Waterjet cutting is a good choice as it won't have produced general hardening but unless the plate is in the fully annealed condition you may not be able to machine it.


Well it must be some ''mild'' grade of A.R. Plate. I turned the o.d. of one of the 26 pieces that need lathe work as well as some mill work. It machined a lot like crmoly. The best I could do was a .020 pass or I would get chatter, but that is on My little lathe at home I'm hoping for a little better at the shop on Friday. I'll let You know.

fishfrnzy
11-26-2010, 11:11 AM
Doctor,

AR plate has alot of variants in the US. AR 235,321,360,400,450,500,600 all reprewsenting Brinell hardness. Usually the AR235-321 will be T1 (ASTM A514) and would be the easiest to machine.

Here may be a place to start:

http://www.ssab.com/Global/Hardox/Brochures/en/010_SSAB_plate_machining_UK.pdf

Some other useful data for bending and welding:

http://www.ssab.com/en/Media/Downloads/