Tanjiro Kamado's sword in "Demon Slayer: Kimetsu no Yaiba" is referred to as a "Nichirin Blade." The specific material used to make the sword is not explicitly mentioned in the series. However, based on the context and historical inspiration, it can be assumed that the blade is made of steel.

In the series, Nichirin Blades are depicted as powerful weapons forged with special techniques and materials. They are said to be capable of cutting through demons effectively. The blades possess distinct patterns and colors representing the unique abilities of their wielders.

While the exact composition and properties of the fictional Nichirin Blades are not specified, they draw inspiration from traditional Japanese swords like katanas, which were typically made from various types of steel. Japanese swordsmiths used different types of steel and techniques to create blades with desired qualities, including sharpness, strength, and flexibility.