02-10-2018, 12:44 AM
(This post was last modified: 02-10-2018, 12:44 AM by Mark Reich.)
Carbon steel has been in use for thousands of years. Only a century ago, someone discovered that adding a lot of chromium to carbon steel kept blades from rusting.
Very simply, steel is "stainless" because it has at least 14% chromium. Stainless only rusts under the worst conditions.
The only benefit of so much chromium alloy is that it prevents rust. Otherwise more than about 1.5% chromium is an impurity that severely degrades the performance of regular carbon steel. Mainly it makes steel softer, more malleable, with larger grain. These things lead to difficult burr removal and less edge stability, which kill cutting performance.
The oldest, most common Japanese steels are White #1 and #2, which is basically purified iron with a single alloying element, an abundance of carbon. With these two, clean ingredients, iron gets very hard, with finer than fine grain. Actually, cementite isn't an alloy, it's a phase of steel with no grain.
Cementite isn't perfect. It's fragile. It breaks and chips easily, and of course it rusts easily. But it is easy to sharpen to an extremely keen edge, mainly because of it's so hard and brittle that it's a cinch to completely deburr.
This is just a rudimentary explanation. but it's probably mostly accurate.
Very simply, steel is "stainless" because it has at least 14% chromium. Stainless only rusts under the worst conditions.
The only benefit of so much chromium alloy is that it prevents rust. Otherwise more than about 1.5% chromium is an impurity that severely degrades the performance of regular carbon steel. Mainly it makes steel softer, more malleable, with larger grain. These things lead to difficult burr removal and less edge stability, which kill cutting performance.
The oldest, most common Japanese steels are White #1 and #2, which is basically purified iron with a single alloying element, an abundance of carbon. With these two, clean ingredients, iron gets very hard, with finer than fine grain. Actually, cementite isn't an alloy, it's a phase of steel with no grain.
Cementite isn't perfect. It's fragile. It breaks and chips easily, and of course it rusts easily. But it is easy to sharpen to an extremely keen edge, mainly because of it's so hard and brittle that it's a cinch to completely deburr.
This is just a rudimentary explanation. but it's probably mostly accurate.