Machining tool steel- heat treating

[DrPatron]

I have a piece of tool steel  (1"x6"x12") It  was on the cutter head of a post peeler. I want to machine it to use as the male end die on a hydrualic  press break.  I don't know what grade of steel it is, but a file won't touch it. I plan on annealling the material in the gas forge, machining the die,  then  hardening and re- tempering,  Am good with the annealing and  re-hardening, but don' know what temperature to temper for a prss die ( Will have to temper to color ,don't have an oven) An Suggestions on the procss and proceedures would be appreciated.  It a pretty espencive piece of steel. I'd hate to scew it up.  But nothing ventured,nothing gained  Thanx-DrPatron

[jonesie]

if you do not know what  type of steel it is how our you going to anneal ,reheat treat and draw back. it might be oil hardening or air hardening, and they heat treat and draw at different temperatures. good luck jonesie

[Lew_Merrick_PE]

DrPatron,

1) Slowly heat up the piece until it is no longer attracted to a magnet (being careful to not allow the magnet to get hot).  When this happens, you have reached the Curie point where the shape of the steel's crystal structure has changed.  Slowly cool the piece to (about) 360°F (180°C) -- and then allow to cool to room temperature normally (i.e. in free air).  You can do this with charcoal, coal, or coke if you do not have access to an industrial furnace or kiln -- just bury the part in ashes and allow the fuel to go out.  So long as your rate of cooling is sufficiently slow, this will anneal the steel.  Keep your fire (assuming that approach) on the reducing side of things.

2) Given that this piece came out of a post peeler, the only gotcha I can foresee is it being S7 (Shock Resisting, Air Hardening) tool steel.  It would be a shame to waste it.  The easiest way to check for this would be to have a piece of "excess" to test.  Heat it up to the Curie point, hold it at that temperature for 20 minutes + 15 minutes for each inch of the thinnest dimension's thickness, and allow it to cool in moderate flow air (i.e. in front of a room fan).  If it gets "hard to a file," then you have an air hardening tool steel.  If not, it is likely to be an oil hardening variety.  Water hardening steels tend to distort more than oil hardening -- which is why I think that it is probably an oil hardening variety.  This statement is a SWAG (Scientific Wild Ass Guess) -- which is somewhat better than a pure WAG.

3) You probably want to end up in the Rc 40-45 range for a ram on a press-die.  I have attached the McMaster-Carr data on tool steels for your enjoyment...