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| John Stevenson:
As many may know I make a lot of special dividing plates, these are made from laser cut blanks usually out of a material called A36 which is a hot rolled steel plate that has a thick oxide layer on it. There is an alternative material called HRPO which stands for Hot rolled picked oiled, basically A36 but cleaned up, costs more and not every company uses it of has it in the stock you want. They like A36 because the oxide layer stops reflection and also stops any dross sticking the the top surface. Problem with A36 is the thick oxide coat destroys the tips on drills in a heartbeat, OK for the odd hole and if you heavily centre punch that also helps but many thousands of holes on a CNC is asking for a broken drill, especially in under 3mm sizes. So what's special about HRPO ? Basically it's been through a commercial picking process, so if we can replicate this it helps with laser cut frames, angle iron and anything that needs to be finished, paint sticks the HRPO better than A36. Picture of a plate straight from the laser cutters. Also in the picture is a piece of bronze and a piece of copper to see how these perform. I'll say at this point the process didn't do much for them. A tub was prepared out of an old plastic 5 gallon suds container by cutting the side out and a 'plate rack' cut on the laser to hold 20 plates which really only applies to me. The solution used is Cementone Brick and Patio cleaner which is basically a weak hydrochloric acid. Don't buy any cleaner that says GREEN on it, that's just basically soapy water. I mix this 1:1 with water and in my case it takes 10 litres of solution. I put these in the tub last night at about 7:00pm and just been out 10:30 am following day and they are all clean and de-scaled, just need a rinse and a wipe with oil. Even cleans the 'burnt' laser cut edge up. |
| Lew_Merrick_PE:
John -- A36 is more properly designated ASTM A36 steel. All that means is that this is a steel with between 0.15% and 0.22% carbon content that has a minimum yield strength of 36,000 psi. Without that designator, it is Merchant Stock or Merchant Grade Steel that can have a minimum yield strength as low as 22,000 psi. You can often save some sheckles by using the MS designation in your order if the lower yield strength is acceptable (and it is usually much closer to 36,000 psi). Muriatic acid (weak hydrochloric acid) works quite well for descaling operations. My local steel yard calls me whenever they have n X 6 inch "drops" lying about. I can pick them up for $0.50/lb rather than the usual $0.90/lb for non-"drops." I set them on pieces of ø1/2 inch plastic (usually ABS or acetal) "tips" left over from longer stock in various sized plastic tubs (I even have an 8 ft long tub scrounged from a siding container at a building site). I cover the pieces to (about) 1/4 inch deep of muriatic acid in such tubs and the scale dissolves within 15 minutes (that after having reused the muriatic acid several times). I rinse them off with a soda-water (call it 1 lb to 5 gallons of water) mixture and dry them. I dress the faces (i.e. 1 inch nominal thick becomes .95 inches thick and .5 inch nominal thick becomes .45 inches thick, etc.), wax them down, and store them in my rack for use in various things I make. One thing that is really handy if you do this is an all-plastic suction-pump (they go on sale for less than $5 regularly at Harbor Freight) to suck up the muriatic acid when the task is complete. This makes it simple to put the acid back in the bottles. I can usually get 5-7 "reuses" before the acid no longer works effectively. Doing this en masse means that I have nice clean & bright steel in my rack when a project crops up... |
| trevoratxtal:
White vinegar is my choice, fairly safe, flush-able, Cheap to purchase and grand on Chips, :lol: Potato type not metal. :) Regards to all. Trev |
| awemawson:
I've banged on about this before but here we go again..... Citric Acid - removes rust, scale and leaves a nice clean surface and is safe enough to put your hands in (cuts sting though!) and it can be disposed of down the drain when finished. Cheap as chips in powder form on eBay |
| Stilldrillin:
--- Quote from: awemawson on May 27, 2013, 12:31:33 PM ---I've banged on about this before but here we go again..... --- End quote --- So, I bought some. From Ebay.... http://www.ebay.co.uk/itm/270958120373?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649 Didn't need it, at that moment. So, I chucked some in the teapot....... Nowt happened! :palm: So, it's in Mrs. Drillin's kitchen cupboard. Waiting to come in useful, mebbe! :scratch: David D |
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