SAN TSUBAME knives both feature 3-ply stainless steel construction. The middle layer is VG No. 5. This layer is very hard and acts as the cutting edge. The two outside layers are made of SUS410 stainless steel. The outside layers are softer and more stain resistant than the cutting edge and actually protect the cutting edge.
3-ply stainless steel has an original thickness of 20 mm and is thinned by repeated rolling to a thickness of 2 mm. You might want to look at this rolling process as a modern forging technique. Also, this rolling process removes all the impurities in the steel leaving you with a very hard, very pure stainless steel. After the rolling processes, the V-G No. 5 cutting edge reaches a hardness of 61 degrees on the Rockwell scale and a final thickness of .65 mm. The outside layers each reach a thickness of .675 mm.
The blade of the SAN TSUBAME is hand-hammered about half way down from the spine. The whole blade is then sandblasted. The sandblasting only affects the softer SUS410 outside layers leaving the outside layers with a matte finish and the VG No. 5 core with a mirror polish. The hammering and sandblasting give the SAN TSUBAME a very rich appearance.