Young Brunette Girl Reveals Her Full Natural Breasts While Posing With Japanese Katana Sword

When steel with a carbon content of 0.7 percent is heated beyond 750 degrees C it enters the "austenite phase". When austenite is cooled very suddenly by quenching in water the structure changes into "martensite", which is an extremely hard form of steel. When austenite is allowed to cool slowly its structure changes into a mixture of ferrite and pearlite which is softer than martensite. By carefully controlling the heating and cooling of the blade being forged Japanese swordsmiths were able to produce a blade that had a softer body and a hard edge creating a superior weapon, this process is called differential hardening or differential quenching. The reason for the formation of the curve in a properly hardened Japanese blade is that iron carbide, formed during heating and retained through quenching, has a lesser density than its root materials have separately.
After the blade is forged it is then sent to be polished. The polishing takes between one and three weeks. The polisher uses finer and finer grains of polishing stones until the blade has a mirror finish in a process called glazing. This makes the blade extremely sharp and reduces drag, making it easier to cut with. The blade curvature also adds to the cutting power.