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My blades get this reddish scale when I am normalizing them. The harden perfectly but I'm curious to know why and if I'm normalizing wrong and for this reason they develop the red. Thanks!

Hi all, I've got some questions about normalizing before a quench. In "The Complete Bladesmith", Jim Hrisoulas cautions against leaving steel for too long above critical temperature when quenching, and against quenching multiple times, because the metal is subject to rapid grain growth above that point. I've seen other sources talk about normalizing the steel before the final quench (often repeatedly) to relieve stress and refine the grain. As I understand it, normalizing (a basic 10XX carbon steel) involves heating the steel above the critical point and then letting it air cool. How does one grow the grain and the other shrink the grain? Does normalizing need to happen at a lower temperature? Or is the grain size determined by the rate of cooling?

Specifications United States: AISI 6150, AMS 6450, AMS 7301, ASTM A322 (6150), ASTM A519 (6150), ASTM A829, SAE J1397 (6150) , SAE J412 (6150), AMS 6448, AMS 6455, ASTM A29 (6150), ASTM A331 (6150), ASTM A752 (6150), MIL. S-8503, SAE J404 (6150), UNSG 61500 International: DIN 50CrV4, EN 50CrV4, Chemistry Crucible: Carbon 0.50, Manganese 0.80, Silicon 0.30, Chromium 1.00, Vanadium 0.15 Metal Ravne: Carbon 0.51, Manganese 0.90, Silicon max. 0.40, Chromium 1.09, Vanadium 0.18, Metal Suppliers Online: Carbon 0.48-0.53, Manganese 0.7-0.9, Silicon 0.15-0.35, Chromium 0.8-0.9, Vanadium 0.15 min. Principle Design Features 6150 is a fine grained, highly abrasion resistant carbon-chromium alloy steel. Very good shock resistance and toughness are also key properties of this alloy in the heat treated condition. Forging Range Forge between 2200 and 1600 degrees Fahrenheit. Note that welding temperature is around 2300 degrees Fahrenheit. You pretty much want to be forging this stuff at a welding heat and be sure to stop hitting it before it gets too cold. The first heat you take will require a definite soak time, from 10-30 minutes, before you start forging. Critical 1360-1380 degrees Fahrenheit Normalize Cycle 1 - Make it good and hot, around 2200 degrees Fahrenheit, soak 10-30 minutes, air cool. Cycle 2 - Get it to 1600 degrees Fahrenheit, soak 10-30 minutes, air cool. Cycle 3 - Heat to 1550 degrees Fahrenheit, soak10-30 minutes, air cool. Hardening Preheat to 1200-1250 degrees Fahrenheit and equalize. Heat to 1500-1650 degrees Fahrenheit, soak 10-30 minutes. Quench Oil quench to hand warm (150 degrees Fahrenheit). Temper Immediately. Temper 2 hours minimum soak at temperature. Cross sections thicker than 2 inches require 1 hour per inch of thickness, round any fractions up. Knives from 6150 will get tempered cooler than you are used to, Here is a clue from an old post (Tempering 6150) "I heat treated a forged blade made of 6150, quenched it in oil and tempered twice at 375 for an hour each time. It Rc tested at 58." Do your own research! Find out, for yourself, all of the information I left out! Here are links to some of the sources used for the information herein: Crucible Selector - AISI 6150 Alloy Steel Metal Ravne Steel Selector - Steel VCV150 (Mat. No. 1.8159, DIN 50CrV4, AISI 6145/6150) Metal Suppliers Online - 6150 Ally Steel