Tool steel

Tool steel is a term used for a variety of high-hardness, abrasion resistant steels. Specific tool applications are dies (stamping or extrusion), cutting, moldmaking, or impact applications like hammers (personal or industrial). It is also a common material used to make knives. Tool Steels are extremely hard and are quite often used to form other metal products. From a composition standpoint, tool steels are carbon or alloy steels, which are capable of being hardened and tempered. Some desirable properties of tool steels are high wear resistance and hardness, good heat resistance, and sufficient strength to work the materials. Some application of tool steels include drills, deep-drawing dies, shear blades, punches, extrusion dies and cutting tools.

Classifications of Tool steels

Tools steels fall into three basic categories:

• Cold work tool steels
• Hot work tool steels
• High-speed tool steels

Cold-work steels are further subdivided into:

• Air-hardening
• Medium-alloy cold-work steels
• High-carbon, high-chromium cold-work steels
• Oil-hardening cold-work steels

Hot work steels are subdivided into:

• Chromium
• Tungsten
• Molybdenum hot work steels

High-speed tool steels are divided into:

• Molybdenum
• Tungsten
• Intermediate high-speed steels

Other types of tool steels include:

• Water-hardening tool steels
• Shock-resistant tool steels
• Low-carbon tool steels
• Low-alloy special purpose tool steels

According to the classification system developed by the American Iron and Steel Institute (AISI), tool steels can be subdivided in seven different groups, based on prominent characteristics such as alloying elements, heat treatment and application. These groups are high-speed-, cold-work-, hot-work-, shockresisting-, mould- special-purpose- and water-hardening as following:

Water-hardening steels

Water-hardening steels are denoted group W steels. They are essentially plain carbon and low alloyed steels. Carbon is the principal alloying element, but small additions of chromium and vanadium are often added for grain refinement, improved resistance against wear and (to a less extend) improved hardenability. (Group W steels can only be hardened to few millimetres below the surface). These tools have low resistance towards softening at elevated temperatures. They are used for applications with limited dynamic load and at low speed such as lath tools, woodworking- and engraving tools.

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