Description
San mai is Japanese for 3 layers, although the technique of putting a hard cutting edge of steel between layers of softer more supportive iron is also prevalent in most of the world for the majority of the past 2000 years and was a particular favorite of the Vikings and Saxons. Stainless steel clad san mai is the modern version of this ancient tradition.
Stainless clad san mai
I am offering stainless steel san mai in a few thicknesses and core thicknesses . I have found that a core thickness of about 1/4 (thin core) works well for knives that will be made by stock removal and a core thickness of around 1/3 (thick core) works better for forged knives. This is marked as thick or thin when you look at the product options.
I am currently offering claddings of 420 martensitic stainless steel.
It has good stain resistance (in its polished and oxidized state) and can form some really beautiful intermetallic at the stainless steel core boundary. This is especially true especially with 26c3 as a core material.
Heat Treating instructions
I apply anti scale compound to my blades when I normalize and harden them. Normalize Damascus steel at 800C and then air cool. I would recommend 3 normalization cycles. Austenise at 800C and hold at temp for 5 minutes. Harden by quenching into a fast quenching oil pre heated to at least 40C. Temper immediately at temperature ranges between 180C and 250C. I temper kitchen knives at 190C or 200C and choppers at 220C and axes at 250C. To soften for drilling I recommend a sub critical anneal, heating the steel to 700C or dull red if you do not have a heat treatment oven and allowing to air cool. If necessary repeat a few times.
Etching advice
Grind all decarburised material from the blade prior to etching. (Hardening will often leave a thin layer of decarburised material on the blade this needs to be removed as it can look patchy in the etch. Grind to 400 grit then clean off all fingerprints with clean 800 grit abrasive on a rubber block. I find abrading the blade gives a better finish than acetone or washing up liquid and hot water. Etch in 1/3 strength ferric chloride until desired depth. Neutralize the blade in bicarbonate of soda solution and then clean in hot water and washing up liquid and rinse with cold water. Ferric reactivity is very dependent on temp. and I find etching can be as quick as 5 min in the height of British summer and take many hours in the winter. A darker contrast can be had by first etching in ferric and then transferring to 50X strength instant coffee. Neutralize as normal after coffee.
