San-mai (Clad Steel)

San-mai (三枚, “three sheets”) is the most common way modern Japanese knives are built. A thin core of hard, high-performing steel is forge-welded between two layers of softer stainless or iron. The core does the cutting and keeps its edge; the outer layers add toughness, resist rust, and mean you only sharpen the small exposed strip of hard steel at the edge rather than a whole hard blade. It is the opposite approach to honyaki, where the entire blade is a single piece of steel. A Damascus pattern, when present, is usually just a decorative treatment of those cladding layers.