Spring steel is simply referred to as "spring steel." The term "spring steel" is used to describe a specific category of steels that are specifically designed and optimized for use in springs. Spring steel is known for its ability to exhibit elasticity, resilience, and the ability to return to its original shape after being deformed.

Spring steel is often made from high-carbon steel or low-alloy steel with specific alloying elements added to enhance its spring properties. Some common types of spring steel include 1070, 1095, 5160, and 9260, among others. The choice of specific grade or type of spring steel depends on the desired strength, toughness, and other performance requirements of the spring application.

So, in short, spring steel is the name used to describe steel specifically designed for use in springs due to its unique properties.