Composition of water/oil hardening knife steels listed in terms of quenching speed
By comparing compositions and the TTT graphs below, the effect of Chromium becomes apparent. Chromium extends the time available for a proper cooling path. Over about 2-3%, Chrome steels become air hardening--meaning such steels can cool in air and still achieve suitable hardness.
As a help in understanding generic steel names: F stands for finishing, W for water, O for oil, L for low alloy and S for shock. 10XX steels are just iron and carbon. For example, 0.80% carbon steel is notated as 1080. Most hot-rolled steel avaiable from your welder is around 1020.
Performance comparison of low alloy knife steels
Additional information on L6, O1, and S1 is available from Timken. The wear resistance of F2 is described by it's maker, Carpenter, as 4 to 10 times that plain carbon steels such as 1095 and W1. Conversely, you'll need special wheels to grind it.
We're going to use O1 (Oil Hardening #1) as it's performance is good, it's widely available and affordable.
Be aware that there are lots of brand names for O1--Arne, Badger, Carpenter O1, Colonial No.6, Ketos, Keystone, Lukens O1, Oilcrat, Presco, Thyrodur 2510, and Truform among others. There may be small compositional differences between brands, but in general, O1 is O1.
The range of composition for O1:
Carbon 0.85 - 1
Since you've already forged a 1018 knife it's now time to obtain some O1 and make a 'real' knife. Get 1/8" by 1", just like you've been using. Everything learned forging O1 can be applied to the other steels.
Online Steel Suppliers:
Online Metals O1 and W1
Texas Knifemaker's Supply 1084, 1095, 5160, O1
Admiral Steel O1, L6, 52100, 1080, 1095, 5160
Now for the TTT graphs of various low alloy knife steels.
Should you not find a diagram for the steel you're interest in,
F2--an extremely fast steel, probably not possible to avoid some Ferrite, water hardening
W1--standard one second carbon steel, water hardening.
O1--two seconds, oil hardening
52100--7-8 seconds, oil hardening
L6--30 seconds, oil hardening