What is San Mai steel? San Mai steel is, in many ways, similar to Damascus steel—it’s well known for incredible levels of durability despite being forged and cut down into blades, and they have exceptional cutting power. The process by which San Mai steel is made is entirely different, however, and it results in a unique set of attributes that other varieties of steel do not have.
San Mai steel is Japanese in origin and aims to achieve specific goals in its composition and construction process. Its name, translated from the original Japanese, roughly comes to mean “three parts”, which is a very apt description for the makeup of these blades. The makeup of the blade is rather simple; the central core of the blade (the part that becomes the edge) is made with a harder steel, whereas the two outer edges beyond that point are made up of a milder, more pliable steel. Its these materials that are what San Mai steel is made of.
This method of creating blades combines the best aspects of both varieties of steel and creates a blade with traits few others have. The hard metal steel at the center of the blade provides it with a sharp, sheer edge that’s perfect for slicing and cutting, whereas the milder steel surrounding it gives the blade shock resistance and helps prevent the blade from shattering, which is a common problem with blades made of pure hard steel. This interplay of different elements gives a San Mai blade it’s unique and legendary reputation. The makeup of the blade is only half of the story, though. The method by which it’s made is just as important to the creation of a San Mai steel blade.
To create San Mai blades, metalsmiths go through a specific process that give these blades their well-known and well-recognized properties. To answer the question of how to make San Mai steel, we need to cover how smiths identify its components. The way metalsmiths pick out which steel to use for the center and the outer portions is based on their carbon density—the more carbon in the steel, the “harder” it is. Once the proper varieties of steel are found, the harder metal will be sandwiched between two equivalent slabs of the milder metal, then they are forged to bond them together. If done properly, sharpening the blade will just barely expose the central, harder steel to create the sheer edge, whereas the milder, more shatter-resistant metal creates a defensive coat around it. Hopefully this in-depth explanation has helped answer the common question of “What is San Mai steel?”