Carbon tool steels are steels designed for machining, heat treating and other metal working tasks that are, for the most part, only accessible to non-metal working trades. Carbon tool steels have a low carbon content, typically from 0.5 percent to 1.2 percent, and are characterized by high-hardenability and strength. The hardness of a given alloy is determined by the alloying content and heat treating process used in its manufacture. Carbon tool steels are available in several standard grades and carbon ranges, such as A2, D2, O1 and S7, and can be customized for specialized applications.
A2 steel is a versatile, low-alloy tool steel that is characterized by its good machinability and strong contributions in cut-wear resistance and hardenability. A2 steel is an air-hardening material, meaning it is easily hardened by cooling in still air or oil. The A2 steel is not as resistant to wear and chipping as some of the harder carbon tool steels, but it is a more economical choice for many applications. In certain applications, it can be used successfully and can provide a balance between wear and cutting performance.
D2 steel is a high-carbon alloy that is often used for cutting tools and dies. Due to its high wear resistance, it is often used in applications that require extended tool life. D2 steel is heat treated through a process called precipitation hardening, which involves air-hardening to various temperatures and then soaking for a set period of time. In comparison to A2 steel, D2 offers better wear resistance and toughness, but is more difficult to machine due to its greater hardness.
O1 steel is a low-alloy steel commonly used for high-speed tooling and die work. It has a low carbon content and is usually supplied in an annealed condition, which makes it very easy to machine. This steel is often used when a softer or lower carbon form of steel is needed. Due to its low-alloy content, it is not as wear resistant as other carbon tool steels. It is most often used to make intricate parts or punch dies and it is often used for cold working applications where high strength and low ductility is required.
S7 steel is a shock-resisting, air-hardening tool steel that has excellent wear resistance and meets the strength requirements of most applications. It is often used for heavy industrial applications due to its toughness and strength. Its low carbon content allows it to be readily machined and hardened. Its exceptional thermal properties make it ideal for press tools and heat treating, and it is often used for dies, punches and plastic molds.
Though each of these carbon tool steels offer unique advantages, it is important to understand the type of application for which each one is best suited in order to ensure a quality finish and extended tool life. Whether an application requires high wear resistance and strength or a softer form of steel, there are a number of carbon tool steels that can cater to the specific requirements of a project. Carbon tool steels offer excellent machinability and strength that can exceed most any project requirement.
