What Is Tool Steel?

Tool steel is the steel used to make cutting tools, measuring tools, molds and wear-resistant tools. Tool steel has higher hardness and can maintain high hardness and red hardness at high temperature, as well as high wear resistance and appropriate toughness. Tool steel is generally divided into carbon tool steel, alloy tool steel and high-speed tool steel.

Steel for manufacturing various cutting tools, cold and hot deformation molds, measuring tools and other tools, collectively referred to as tool steel. Various tool steels have common requirements, such as high hardness, good wear resistance and certain toughness and strength, etc., as well as their own special requirements, such as red hardness, impact resistance, dimensional stability, thermal fatigue resistance and Good comprehensive mechanical properties. In order to meet these different requirements, tool steels of various compositions are used in production, and their performance requirements are achieved by appropriate heat treatment processes.

High speed tool steel is an alloy tool steel, which contains C, Mn, Si, Cr, V, W, Mo, Co. And it can be used as a high-speed rotary cutting tool, which is wear-resistant and high-temperature resistant, that is, Cr, V, W, and Mo are relatively large. Take W ₁₂ Cr ₄ V ₅ Co ₅ as an example. 5%, V-> 4.5% -5.25%, W-> 11.75% -13%. The proportion of Cr and V must not be less than 3%. The content of P and S should not be greater than 0.030%.

The processing methods of alloy tool steels are mainly press working steels and cutting tool steels. There are many types of alloy tool steels, including cold work, hot work, and non-magnetic.

According to different chemical compositions, tool steel is often divided into three categories: carbon tool steel, alloy tool steel, and high-speed steel (essentially high-alloy tool steel). According to the use of steel, it can be divided into three major categories: cutting tool steel, mold steel, and measuring steel.

Carbon tool steel : Carbon tool steel has a high carbon mass fraction, ranging from 0.65 to 1.35%, and is classified as a sub-eutectoid, eutectoid, or hypereutectoid steel according to its organization. The surface of carbon tool steel after heat treatment can obtain higher hardness and wear resistance, and the core has better toughness; the annealing hardness is low (not greater than HB207), and the processability is good. However, its red hardness is poor. When the working temperature reaches 250 ° C, the hardness and abrasion resistance of steel decrease sharply, and the hardness drops below HRC60. This type of steel has low hardenability. Larger tools cannot be hardened (water-hardened diameter is 15mm), and the hardness of the surface hardened layer and the central part is very different during water hardening. Makes tools prone to deformation during quenching. Or crack formation. In addition, the quenching temperature range is narrow, and the temperature should be strictly controlled during quenching. Prevent overheating, decarburization and deformation.

T7, T7A hypoeutectoid steel : has better ductility,

The service life of tool steel is closely related to the quality of its heat treatment. The heat treatment of tool steel is characterized by spheroidizing annealing in advance to obtain a uniform and moderately spheroidized structure. The final heat treatment is quenching plus low temperature tempering (high-speed steel is Quenching and tempering at 560 ° C for three times) to obtain a high hardness structure with uniform and fine carbides distributed on the tempered martensite matrix to ensure the wear resistance of the tool. The heat treatment of hot forging die steel is different. The pre-heat treatment is a one-step annealing, and the final heat treatment is quenching plus moderate temperature tempering or high temperature tempering to obtain good comprehensive mechanical properties. ^[2]