What kind of steel alloy a bladesmith uses to make a sword depends largely on their experience and the characteristics they want in the blade. The alloy used is almost always a form of carbon steel. A certain amount of carbon is necessary to give the metal enough hardness to be able to take an edge and hold it. But too much carbon decreases the flexibility of the blade, making it brittle and more likely to break.
Jim Hrisoulas, author of "The Complete Bladesmith," recommends a steel with a carbon content of around 60 to 70 points. In steel, carbon content is listed as points with each point equaling 0.01 percent of the total composition. Therefore, a 70 point rating means that the alloy has 0.7 percent carbon in the mix. Don Fogg actually uses 1086 steel (.86 percent carbon) and achieves superior results. However, the higher the rating doesn't always mean better steel. A process of careful heat-treating allows for very hard blades that are resilient and tough.
Photo courtesy Don Fogg Knives
The steel in a sword should have a carbon rating of 60 to 70 points.
Most of the steel alloys include one or more of the following elements, each one providing certain advantages (and some disadvantages). While the elements listed below are the most common, there are many others that may appear in an alloy.
-
Chromium - Aids hardening; used in stainless-steel alloys; can cause the steel to crack during forging
-
Tungsten - Provides for a sharp and long-lasting edge; hard to forge
-
Manganese - Adds strength during the heat-treatment process
-
Molybdenum - Keeps the steel hard at higher temperatures; very difficult to forge when present in high quantity
-
Nickel - Adds strength, does not increase hardness; appears in higher concentration in stainless-steel alloys
-
Silicon - Improves flexibility and hardness; can increase conductivity of the alloy
Before choosing a metal, the bladesmith creates a design for the blade and determines what the most important characteristics for that blade will be. For example, a slim blade like a rapier needs to be very flexible while a broadsword needs greater hardness and strength. The bladesmith also decides what method to use for creating the blade. This will determine which metals can be used, particularly stainless steel alloys. Stainless steel is incredibly difficult to forge and temper properly, but a bladesmith can purchase stainless steel bars and grind them into shape using the stock removal process. In stock removal, a sword blade is made by taking a stock piece of steel and removing portions of it by cutting and grinding until you have the desired shape. Most bladesmiths prefer the flexibility that forging provides them with when creating custom swords. A forged blade is created by heating the metal and pounding it into shape.
Forged swords may contain a single metal or a combination of metals. The easiest and most common form of forged sword uses a single steel alloy to create the blade. Designs are sometimes engraved or etched into the steel to simulate the more complicated pattern welding and Damascus blades.
Pattern welding, also called laminate steel or pattern-welded Damascus steel (see below), uses two or more metals combined together during the forging process. Typically, layers of a steel alloy are combined with layers of a softer metal, such as nickle. The layers are folded onto each other numerous times, which helps to further remove any impurities in the metal. It also greatly multiplies the total number of layers. If a bladesmith starts out with three layers of nickle sandwiched between four layers of steel, then a single fold will double the number of layers to 14. Another fold would make 28 layers and a third one would create a total of 56 layers!
Photo courtesy Don Fogg Knives
A pattern-welded Damascus blade created by master bladesmith Don Fogg
As the folding continues, the softer metal welds or glues the layers of steel together to form a single whole. The softer metal layers give the sword greater flexibility without sacrificing the hardness of the steel needed for the cutting edge. Once the blade is complete, it is given an acid wash that brings out the contrast between the metals used. The patterns created by the different metals add incredible beauty to the blade and can be quite intricate.
Damascus Steel
A technique that was considered lost for many centuries, true Damascus steel has often been confused with pattern-welded steel. In fact, many sword makers and sellers still refer to pattern-welded blades as Damascus steel.
Photo courtesy Don Fogg Knives
Detail of a feather pattern in a Damascus blade
J. D. Verhoeven, A. H. Pendray and W. E. Dauksch published an article in the September 1998 issue of the Journal of Metallurgy about Damascus steel that turned the sword-making world upside down. They assert that true Damascus steel is wootz steel. Wootz was a form of steel made in India that had a very high carbon content. When the steel was forged, some of the carbon would separate into bands. These bands would appear very light in color and the rest of the steel would become quite dark when polished and etched. The result was a highly contrasted pattern. As bladesmiths learned how to work with the wootz steel, they discovered that they could make the patterns very intricate by changing the angle of the blade in relation to the bands of carbon and steel.