Forge Welding Techniques Explained: San Mai
One of the most popular styles of forging, the technique of San Mai is an ancient and time-tested method of bladesmithing that produces blades that are as functional as they are beautiful!
(Image credit: Cellular Abroad)
Originating over 700 years ago in Feudal Japan, San Mai is the process of forging layered steel into blades. Literally meaning “three parts” in Japanese, this description refers to the three main components of the blade: The central core of harder steel for slicing and the two outer edges made from softer, durable steel.
As is common with other forge welding techniques, the term San Mai refers specifically to the forging process rather than a specific type of blade. Japanese bladesmiths used this technique to forge all manner of blades from battle swords to everyday knives, with many becoming popular due to their ability to consistently hold an edge and their resistance to corrosion.
While blades crafted from one type of steel often require compromises in sharpness and/or durability, this layering of different types of steels offers the best of both worlds. San Mai is often referred to as a “metal sandwich” due to being forged from a three-layered billet of steel. This layered steel billet results in a unique set of properties; a hard steel core providing a sharp edge perfect for slicing and cutting, and softer steel on the edges offering additional shock resistance.
(Image credit: Maker Material Supply)
As a result of the layering process, San Mai blades feature a distinctive lightning bolt pattern down the center of the blade. Sometimes resembling mountain peaks, this bold stripe shows the different kinds of steel melting into one impeccable blade.
While Damascus and San Mai are often compared due to their legendary performance, both techniques are very different. Unlike Damascus, San Mai doesn’t require an extensive layering process. With San Mai, there’s no need to continuously restack the billet; once the bladesmith has the three layers in place, it’s a matter of forging the pieces until they are welded together. The bladesmith’s main concern is keeping the center piece aligned with the outer layers.
“Repeated heating and slow cooling alters the blade’s microstructure, increasing its ductility and preventing it from becoming too brittle and hard. ”
After forging, San Mai must go through a process of normalization followed by air cooling at room temperature. As with many blades, the normalization process follows a triple cycle to refine the steel and ensure its edge will hold. Repeated heating and slow cooling alters the blade’s microstructure, increasing its ductility and preventing it from becoming too brittle and hard.
(Image credit: Everything Wing Chung)
Modern day bladesmiths crafting San Mai generally use a laminate billet on the outside and high carbon 1080 steel in the center. The sharp 1080 steel gives it an edge, while the outer layers keep the blade strong and shatter resistant. Steel with low carbon is flexible, but is often soft, making it less than ideal for cutting. San Mai blades avoid this by using a laminate billet to incorporate both hard and soft steel into the blade. The softer, outer laminate acts as a protective coat for the hard, more brittle inner layer.
However, carbon content isn’t the only element to take into consideration when forging in this style. Steel with high amounts of chromium can be used for the outer layer to prevent rusting and oxidation, as the chromium serves as a key component in the San Mai blades’ ability to survive the typical wear and tear.
While many forging techniques have become obsolete or lost to history, San Mai is still wildly popular among chefs. Blades crafted from this technique are a favorite in the culinary world due to their incredible sharpness and low propensity towards rusting. Chefs using these blades can consistently slice through thick pieces of fish and meat with little effort.
(Image credit: Eating Tools)
San Mai blades are not only highly functional, but they also make fantastic pieces of artwork. Many professional chefs will hang custom engraved pieces of San Mai in their kitchens for display to the masses. As long as a San Mai blade is properly maintained, it will serve its purpose flawlessly, and for a very long time.
The San Mai technique will continue to be popular for years to come and will remain a favorite among chefs and bladesmiths worldwide. This blade doesn’t just look appealing, it has the cutting skills to live up to the hype.
Stick with BRUTE de FORGE as we continue to dig into the techniques used to forge the weapons that forged the world, including our previous deep-dive into Damascus. Be sure to follow us on Twitter and Facebook to stay up-to-date with the latest bladesmithing news!
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