Tool Steel Knowledge needed

[JHCC]

acein, you could also consult the Heat Treater's Guide Companion app from ASM International and the ASM Heat Treating Society, available free for both Apple and Android platforms. It's an excellent resource for most steels in use in the US, apart from proprietary alloys from individual companies (such as 15N20 from Bohler-Uddeholm).

[Latticino]

Depending on how you plan on using your hammer, the dies don't necessarily have to be that hard (and as you alluded it would certainly be a mistake to harden too far). In fact  I took a class from a professional smith who runs one of his hammers with mild steel dies that he only hardens with Super Quench.  Theoretically you shouldn't be abrading away the surface of a hammer die in the same way you do by sharpening things like Knives and axes, so a relatively shallow hardness is acceptable.  I certainly witnessed him using this hammer to straighten out cold laminated steel knife blades with no apparent damage to the dies.  

That being said, from what I can tell I would expect 4340 would make great dies for your hammer.  If it were me, I would perform my own anneal on the stock to make sure it was as soft as possible to allow easy shaping and harden and temper afterwards.  Since I wouldn't be concerned about maximizing hardness, I would quench in a medium speed oil and temper immediately after stock drops down to 140 deg F.  Note that apparently there is a variety designated 4340H that can be subject to quench cracking, so extra care might be needed if you have that flavor.

[Scott NC]

  I notice an hour ago, acein, you were still prodding Frosty on your profile.  I also notice how information flows once it is figured out which way the wind blows around here.  I wish I could have answered your question before all the melee but it's out of my wheelhouse.  Dynamics are interesting on this forum.

Edited January 26 by Scott NC
Fix wording

[Nobody Special]

Good afternoon,

I didn't make the dies. I would think that might be thick enough to warrant it, but I would tend to err on the side of too soft rather than too hard and see how that goes. Many people on here have far more experience than I do using power hammers and can probably give better advice.

The area where I experienced something similar was making hand-held hammer heads; on a couple of hammers, steels that were oil quench when making blades didn't harden fully when doing an oil quench for hammer heads. Of course, it can be counterproductive to have hammer heads too hard. Also, in one case when I water hardened, I had the hammer crack at the eye after a couple of days of use, even though it was tempered softer at the eye.

[patrick]

On 1/23/2024 at 6:26 PM, acein said:

Patrick, thanks for the information.  I have read online that I can harden 4340 up to 60HRC.  Some say I can get 45 HRC with quenching, Then flame harden up to 60.  Do you think this is achievable?  

Generally speaking it is going to be tough to get 4340 up to HRC 60. The maximum as-quenched hardness of any steel is a function of the carbon content (barring the very highly allowed cutlery and high speed steel types). It typically takes about 0.57% carbon to hit HRC 60. More carbon above that value will not give you higher hardness, but it does give increased wear resistance which is why cutlery grades have carbon close too or sometimes exceeding 1% carbon. For steels in the 0.405 carbon ranges, max hardness is going to be in the mid 50s HRC. Usually, the parts will be tempered, so working hardness will be somewhat, or maybe a lot, less than this. Flame hardening is a technique using a torch to locally heat the surface. Typically a quench nozzle or spray follows close behind the torch tip. The goal is to create a hardened surface layer while keeping the interior of the part at a lower hardness for better toughness. For the power hammer dies that were discussed in another thread, I would suggest a through hardened part rather than a surface hardened one. 

With the use of special coatings or other treatments such as carburizing and nitriding, it is possible to achieve surface hardness of HRC 60 or above, but I can't think of an application in the blacksmith shop that would benefit from this. This type of hardness is used for gears and bearings in high wear applications or shafting subjected to a lot of sliding wear. In the blacksmith shop, the hardest tools usually will be power hammer dies, anvil faces and hand hammer faces. These should all be made with hardness closer to the low 50 HRC range to reduce the chances of brittle failure.