Tool Steel simplified questions

[SteelSlaver]

I got the book as recommended. Great read and very informative. Learned a lot and of course that bring me more questions, I realize most of the water hardening steels discussed had a carbon content over 1% but some of the oil hardening and red hard materials did not. I was curious as to why a temper over 400 was seldom recommended in the water hards, when I read here that less than 400 would not really do a complete temper. I also found it interesting that as time of temper went up temperature of temper went down to achieve the same effect.

Would 1095 or my 1095/15n20 damascus harden better in brine than in fast oil and would I end up with a higher hardness after temper or would it just harden a bit deeper.

I found the timbre and other information very interesting. Loads of information and little facts. Well worth the money. Thank you Mr Cashen for the heads up.

 

[Stacy E. Apelt - Bladesmith]

mete or Kevin will give a better answer. but here is a little info:
Red hard has more to do with the alloy elements than the carbon content.

Brine (or water) doesn't harden any harder than oil if it passes the nose. However it may harden deeper, as you suspected. Insufficient quench media volume is far more of a problem.

Temper over 400F is fine for certain functions (spring temper) but for knife purposes, 400F is usually a ceiling for simple water hardening steels. It will give a good hard edge with sufficient toughness.

Temper target is a factor of time and temperature. It you increase one you have to decrease the other to get the same result.
Stacy

 

[mete]

The quenching rule is to quench as fast as necessary to obtain required hardness but no faster. Faster than necessary quench invites quench cracks !!...The tool steels that are used as tooling which gets hot usually contain amounts of V, Mo, and W which give secondary hardening and maintain hardness [red hard]...The simple steels are usually tempered at 400 F since higher temperature quickly reduce useful hardness.