San Mai Japanese Kitchen Knives
One of the more common forms of Japanese kitchen knife design, and perhaps our favourite, is the technique of "San Mai".
San Mai kitchen knives consist of a hard (often high carbon) steel core, with a soft iron, or stainless steel cladding surrounding it. The advantage to this knife design is the high carbon steel core is only exposed on the edge, resulting in a sharper knife, with the majority of the knife body covered in a more rust resistant steel. As the edge of your knife is the edge which is sharpened, rust is easier to remove if it does start to form (although easy to avoid with minimal knife maintenance).
In Japan, the hard inner core is referred to as "Hagane", with the outter layer(s) of lamination referred to as "Jigane"