Tamahagane, which is the raw material for Japanese Swords, is made of iron sand due to its low level of impurities. In the tatara steelmaking method, high-quality material with a carbon content of around 0.3 to 1.5% through low temperature reduction (1300-1500℃) is the main ingredient of the tamahagane. This is then flattened out to a thickness of about 3 mm. The material is then stacked up and forge welded by heating to around 1300℃.