Traditional samurai swords, such as the katana, were typically made using a type of carbon steel known as tamahagane. Tamahagane is a specific type of steel that was produced through a labor-intensive process in Japan.

Tamahagane is created by smelting iron sand (satetsu) with charcoal in a traditional clay furnace called a tatara. The resulting steel has a relatively low carbon content but contains impurities, such as silica and slag, which give the steel its characteristic grain structure.

The tamahagane steel is then carefully forged and shaped by skilled swordsmiths using traditional techniques. The forging process involves heating, folding, and hammering the steel to remove impurities, refine the grain structure, and create the desired shape and curvature of the sword blade. The blade is then differentially hardened by heating and quenching, which creates the distinct hard edge and softer, more flexible spine of the katana.

The specific composition and properties of tamahagane can vary depending on the region, the quality of the iron sand used, and the skill of the swordsmith. The traditional craftsmanship and knowledge of the swordsmiths played a crucial role in creating high-quality swords with exceptional cutting ability, durability, and beauty.

It's worth noting that tamahagane is a term specific to traditional Japanese sword-making. In modern times, other types of steels with specific properties and characteristics are often used to create functional and decorative swords that resemble traditional samurai swords.