I posted this on KF but I think it is worth repeating.
Now that i have introduced myself, I would like to introduce you to my favorite steel Mr. O-1, and his wife in my damascus Mrs. L-6.
I will briefly introduce some of the common alloying elements of steel as well.
In my research early in my damascus making was looking for some suitable steels to make good damascus out of. I started out with 1095 and 15n20, a popular mix, but I thought there might be a better mix. There are many factors necessary to produce a good damascus mix, just as there are many factors of personality necessary to produce a good marriage. In order to produce steel only two ingredients are necessary Iron and Carbon. Each additional element produces certian traits, like personality traits in us. Not only is each element important the quantity is also important. Carbon in quantities around one percent are best for our purposes, over 1.5% and the steel becomes cast iron, lowering the melting point. Carbon around 1% is very good for slicing cutters that require a very strong abrasion resistant edge, but it is not the best for blades made to do heavy cleaving or chopping. Less than .6% and there in not enough carbon to produce enough carbides to give enough wear resistance and hardness for knives. Manganese is commonly added to all modern steels, it helps smooth pouring of the steel when it is molten, in higher quantities it assists in hardening and it is the element most responsible for the dark coloring of the steel in damascus.The main reason for manganese in almost all modern steels is to combat the effects of sulfur, by forming manganese sulfide, a more stable compound that does not liquefy in the grain boundaries. Chromium is a popular alloying element, and in quantities over 13% is responsible for the stainless properties, due to the high concentration of microscopic chromium oxides on the surface of the steel. In lower quantities it produces chromium carbides, which can be benificial in small quantities, however in large quantities they can clump into huge clusters and make sharpening difficult. They have a tendency to break out of the edge rather than being worn down in the sharpening process. Carbide clustering can be controlled by using powder metallurgy or by lowering the carbon content in the steel, thus disallowing the formation of excess carbides. Tungsten (wolfram) is another carbide former, producing fine and very hard carbides, in small quantities it aids in wear resistance as all the carbide formers do, in large quanties it is used in steels used to cut other steels, especially hardened steels. Molybdenum is another carbide former, though not as hard as tungsten, is a common alloying element, especially in the high alloy stainless steels. In non-stainless steels it is added to hot-work steels, those steels which may encounter some heat during use, like drill bits. It gives the steel a much higher tempering temperature, so that heat encountered in use will not affect the hardness of the steel. Silicon gives the steel additional toughness, and has no effect on hardness. Nickel also gives the steel toughness, it also gives the steel acid and etchant resistance, which allows for the contrasting effect in damascus. In higher quantities in collusion with chromium it can produce stainless effect in steel without much carbon and without being hardened. The 300 series of stainless steels used in stainless countertops and food pans.
This has been a general overview of some of the common alloying elements, just to give some basic idea of what certian elements in steel do. I am not a trained metallurgist, however I have made a serious study of the subject. One important fact is that very small amounts of alloys can have a noticeble effects, as little as .05%.
O-1 stats (typical)
L-6 stats (typical)
O-1 is an oil hardening tool steel with deep hardening qualities with little size change in hardening, with a fine grain structure. These characteristics make it an excellent steel for many purposes, including knives. The small amount of tungsten makes a significant difference in the cutting ability and wear rsistance of this steel. Fully hardened it can reach 65rc.
L-6 is a tough, high-strength oil hardening tool steel suitable for high stress jobs, like saw blades and longer knives.
Fully hardened it can also reach 65rc.
Alloying in steel is always given in a range, so that minor variations can occur; as a result the heat treatment temperatures are also given in a range. One of the things that make these two steels such a perfect match is that those heat treat ranges overlap. This is of critical importance for the high preformance of the finished damascus. This overlap is the reason that only a very few steels can be compatable for damascus, and the reason why 3 steel combinations are impractical.
For these reasons I believe that properly heat treated the O-1 and L-6 damascus is the best combination available for knives. This damascus mix is not for beginners, requiring more skill to work properly than mixes such as 1095/15n20, and more precision with temperatures, but I believe that the extra efoort is worth it in the finished product.
I would also like to give credit to Kevin Cashen, who proof read this and added some additional comments to make this information more complete, and who has helped me with my understanding of metallurgy over the years.
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