Rob, this threat should pretty much cover you.

Red

Mete, Poseur, Blue, Bill Leeper & others :

Anybody who knows about Steel "ET 64" ??
And what is the properties of this steel, impact stength etc etc?
And how good is for use as a rifle action ?

Ulrik, There are some American steels which use ET as part of the designation, From what your gunsmith is talking about doing this might be very similar to our 4130 (modified). I made magazine boxes from an ET steel. ET stands for elevated temperature. It was really a 4130 type. One of these steels was trade named "Astroloy" . 4130 does not harden completely through in cross section because it is not really a through hardening steel. By heating to a very high temperature and letting the steel cool rapidly in a neutral atmosphere but cold hearth, the steel maker was able to provide a steel not having the "normal" characteristics of 4130 steel. My billets were 38 m/m thick and Rockwell hardness was right at the advertised R C 36. This ate saw blades and cutters and I had some difficulty getting it to a lower rockwell hardness, because it defied normal 4130 procedures. Hobaugh made barrels from Astroloy for a long time. Unlike 4130 it did not blue well, turning a wine red color, which got lighter with age. Carburizing temperature would undo the results of the ET treatment, and the result would be the same as that on some US military rifle receivers of WW-II. These functioned quite well. I hope this might provide a clue for you and your Gunsmith. Steel companies like to think they have a secret proprietary process on something like this

Ulrik,

Never heard of it. What country is it from? Is it a stainless, tool (high alloy / high carbon steel) or a low alloy / low carbon steel?

POSEUR

it�s a norwegian number. It is a CrMo steel of some kind. Should be very high quality. I guess it is high carbon steel because my gunsmith is planning to case harden the action.
All I know is that it is prehardened steel, ET 64. Hardness: 32 HRc and that it will be case hardened after machining is done.

Ulrik,

Cannot find any reference to it on this side of the Atlantic, at least not in my reference materials.

From your description though, it sounds very much like our SAE4140 prehard aka Duralloy. Not the best stuff in the world for a rifle action, in my opinion, but it will most certainly work. In general CrMo steels, particularly when hardened, do not have very good impact strengths. Also, if it is a prehard, you will not be case hardening it at least not in the traditional sense.

With a prehard alloy (typically containing at least 0.4% carbon) one would induction hardened, which can produce a case IF the section is thick enough (if there is insufficient section thickness through hardening occurs), or it would have to be through hardened and then drawn back.

Personally, I would opt for 17CrNiMo6 or 18CrNiMo7-6. I would anneal the billet, machine the action and bolt, and case carburize to achieve an effective case depth of 0.5mm - 0.9mm, a surface hardness of Rc57 to Rc 62, and with a core hardness of Rc 30 - Rc 35. "Effective case depth" is defined as the depth from the surface at which time the hardness has dropped to a value of Rc 50. This is a VERY tough steel with very good to excellent impact strength. You should be able to get it in Europe without too much difficult. If you wanted to use a USA steel then I would opt for SAE8620 at a minimum preferring SAE4320. Is would case carburize the US grades the same as the DIN steel.

ASS_CLOWN