Tool steel can refer to a variety of carbon and alloy steels which are commonly used to make tools.
Tool steels are vastly different from steel used in consumer goods and they are made on a much smaller scale. Strict quality procedures assure that a given grade of tool steel will perform a specific task such as machining or perforating.
Tool steel is generally used in a heat-treated state. Many high-carbon tool steels are also more resistant to corrosion due to their higher ratios of elements such as vanadium and niobium.
Tool steels are steels which are manufactured under carefully controlled conditions with carbon content between 0.7% and 1.5% and low manganese content to reduce the possibility of cracking during water quenching. Proper heat treating of these steels is important for adequate performance.
High-load applications such as punching stainless steel, spring steel and high-strength low-alloy require tool steels with a combination of shock resistance, wear resistance and high compressive strength.
Tool steels are made in a number of grades for different applications. Choice of grade depends on the edge temperature under expected use. This is an important determinant of both composition and required heat treatment. For example:
- W-type tool steel is the most commonly used tool steel because of its low cost compared to other tool steels.
- Cold-work type tool steels are used on larger parts or parts that require minimal distortion during hardening.
- D-type tool steels retain their hardness up to a temperature of 800°F (425°C) and is used for forging dies, die-casting.
- S-type tool steel is designed to resist shock at both low and high temperatures and is used in jackhammer bits.
- T-type and M-type tool steels are used for cutting tools where strength and hardness must be retained at temperatures up to or exceeding 1400°F (760°C).
- H-type tool steels were developed for strength and hardness during prolonged exposure to elevated temperatures.
Tool steels are also used for injection molding because resistance to abrasion is an important criterion for a mold that will be used to produce hundreds of thousands of parts. The higher carbon grades are typically used for such applications as stamping dies, metal cutting tools, etc.
Tool steel's suitability comes from its alloy's properties:
- Distinctive hardness
- Resistance to abrasion
- Ability to hold a cutting edge
- Red-hardness
Other factors in tool steel selection include:
- Machinability
- Grindability
- Tolerances
- Polishability