Tempering/Quench lines

G. McCormack · 16th March 2009, 03:01 AM

Steel is made up of crystals, and its crystal microstructure is dependent on things like how it was worked, and what temperatures it was heated up to and cooled down from- and at what rates.
When a bladesmith quenches a carbon containing steel blade from above a specific temperature into oil or water, certain microstructures are formed. Different microstructures form because of a number of factors, including the amount of carbon, the temperature before quenching, and the rate of cooling.
These different microstructures look different when etched, and that is the reason parts of your blades are darker than others.

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16th March 2009, 03:01 AM	#2
G. McCormack Member Join Date: Jul 2005 Location: Tallahassee, FL Posts: 131	Steel is made up of crystals, and its crystal microstructure is dependent on things like how it was worked, and what temperatures it was heated up to and cooled down from- and at what rates. When a bladesmith quenches a carbon containing steel blade from above a specific temperature into oil or water, certain microstructures are formed. Different microstructures form because of a number of factors, including the amount of carbon, the temperature before quenching, and the rate of cooling. These different microstructures look different when etched, and that is the reason parts of your blades are darker than others.