1045 steel is a medium carbon steel that falls under the American Iron and Steel Institute (AISI) designation system. It is commonly referred to as AISI 1045 steel. The "1045" in the name represents the approximate carbon content of the steel, which is about 0.45%.

1045 steel is known for its good strength, toughness, and wear resistance. It has a higher carbon content compared to low carbon steels, which contributes to its increased hardness and strength. This steel grade is often used in applications where strength and impact resistance are important, such as gears, shafts, axles, bolts, studs, and other components that require high strength and durability.

In addition to its mechanical properties, 1045 steel is also readily weldable and machinable, making it a versatile choice for various fabrication processes. It can be heat treated to further enhance its properties, such as through quenching and tempering.

Overall, AISI 1045 steel is a widely used medium carbon steel with good strength and toughness, suitable for a range of applications in different industries.