SK material

Relatively inexpensive knives often use SK material, which contains slightly more impurities. The impurities referred to here are sulfur and phosphorus, among others. The higher the amount of these impurities, the easier it is to perform the "hardening" process, one of the steps in knife manufacturing. As a result, the skill required from the blacksmith is not as high. Additionally, these impurities can also cause embrittlement, which makes the metal lose its toughness and become more prone to breaking. For these reasons, SK material allows for cheaper production. Besides knives, SK material is also used for tools like axes, hammers, and saws.