Re: [CAD_CAM_EDM_DRO] Re: Metal selection 101

I think the best method for hardening the 8620 is color case hardening.
the process is simple, leave a nice looking HARD surface and a soft inner
core.
This is ideal for firearms receivers as the soft core helps prevent
shattering of the receiver(in your face) if an overloaded cartridge happens
to be fired in it.

Smoke
-----Original Message-----
From: dave engvall <dengvall@...>
To: CAD_CAM_EDM_DRO@yahoogroups.com <CAD_CAM_EDM_DRO@yahoogroups.com>
Date: Monday, March 12, 2001 5:48 PM
Subject: [CAD_CAM_EDM_DRO] Re: Metal selection 101

>Hi Lee, et al
>Understand that everyone has their preferences for
>steels, etc.
>Mine are:
>
> 8620 easy to machine but a little gummy;
>can be quenched in oil or water and will give
>decent hardness for many applications w/o
>carburizing. e.g. Rc 38-42 on quench and temper.
>If you need a really hard case then go ahead and
>carburize, quench and temper. For fancy
>apps....carburize, cool, quench from 1550, quench
>from 1450. Give really nice fatigue values.
>(e-mail me if you really care :-) )
>
>4140 because of the higher C content more
>difficult to machine. Hardens deeper than the
>8620. Oil or polymer quench.
>
>4340 deeper hardening than 4140. Easier than
>4140 to find in the Seattle area because of the
>aerospace applications.
>There was a ton or so of 4340 /300M at Boeing a
>few weeks ago.... $0.25/lb. :-)
>Because of it's deeper hardening characteristics
>consider 4340 an upgrade from 4140.
>
>A10... air hardening , low quench temp and
>therefore low distortion. easy to machine because
>of the spherodized carbon content.
>
>A6 - if you can get it... a nice balance (for a
>tool steel) between hardness and toughness.
>
>D2 - very hard but brittle by comparison.
>
>H13 - consider for very high impact
>applications....really tough if you temper back to
>Rc 38.
>
>S7 - designed for high impact toughness.
>
>Hope this helps some.
>
>Dave
>
>
>
>
>
>
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