In this thread

J.W.S mentions hardening the face of his block anvil.  How do you do this?

First start with a block of steel of an alloy that can be hardened.  Heat the face to the correct temperature for that alloy.  Quench in the correct medium for that alloy making allowance for the fact that large pieces often go one (or more) levels down on the quench list. (so an oil quench steel might need a water quench, etc; the opposite of blades where due to the thinness of the steel you often go 1 higher on the list...)  Draw temper to the appropriate temperature for that alloy and that use.

Lots of quenchent...

JWS pointed out in the first post that the steel block is A2 - which means it hardens as it cools in the air - so a little less daunting to quench than if it were another alloy.

(I asked him that question and he pointed out the original post, which I overlooked.)

Ah.  For some reason my eyes skipped over the A2.  I assume you heat it with an oxy-acetaline torch.  Do you aim for only the face to harden or do you look to get it deeper?

Here is to hoping the local steel yard has some A2.  Being the largest steel yard in northern AZ, you would think they would but not necessarily.

I'm heating it in my largest forge with an hour soak at 1750F - that's the most difficult part of the process.. Well, that and moving an 85lb block of steel at that temp.. Next is air cooling. Rate should be constant, so the shop fans will be pointed at it. Since I'm not heating the entire block to 1750F, only the first 0.5", the rest of the mass should also help with an even draw of temperature. I'm looking at about 12-17 hours then in the oven at around 500F for stress relief and tempering. I don't have the capability to cryo treat it, but that's not what I'm looking for in this tool. I'll be happy with around 54-58R.

J

Oh and A2 can also be oil hardened.. But why complicate it? Lol

 

A2 tends to be quite pricy; you may be able to find 4340 in large chunks cheaper.  I would ask at machine shops about drops before buying retail.

1 hour ago, ThomasPowers said:

A2 tends to be quite pricy; you may be able to find 4340 in large chunks cheaper.  I would ask at machine shops about drops before buying retail.

Around here it's $1/lb.

J

I'm going on memory and that is a dicey proposition these days but IIRC, that large a block may require oil quench to reach the higher hardness ranges.  Of course, it doesn't cost anything other than a bit of fuel to try an air quench first.

An air blast table set up with an air gun on it will cool it quick. My friend has one made with a muffin fan on it for his small parts. The fan is underneath some expanded steel that the parts get set onto.

$1 a pound for A2 is cheap.