What is tool steel – definition

Tool steel is a type of high-strength steel with special properties that is used to manufacture various types of tools, including cutting tools, molds, dies, knives, drills, pliers, and tools for heat treatment and forming. Tool steel is characterized primarily by high hardness, abrasion resistance, and the ability to maintain its properties under high temperatures.
Hot-work tool steel is ideal for tools that are exposed to frequent and sudden temperature changes. These steels also cope well with high pressures and abrasion. Medium-alloy steels are characterized by good thermal conductivity, which is why there are no major problems with crack formation. These types of steels are mainly used for the production of press anvils and reliable forging dies. High-alloy steels are mainly used for press dies or high-pressure die casting molds. In the production of these tools, contact with hot material is quite long.

Tool steel is characterized by very high hardness (even over 60 HRC), thanks to which tools made of it cope very well with the materials being processed. Alloy tool steels provide adequate ductility, crack resistance, and high abrasion resistance. The tools are able to maintain their performance even under very high friction, where there is significant unit pressure. Their greatest advantages include adequate hardenability and high resistance to the tempering effect of high temperatures.

The most popular types of tool steel

In terms of tool surface temperature, alloy tool steels can be divided into cold and hot working steels. If the tools are to be used below 200 degrees Celsius, cold working alloy steels are used. Above this temperature, hot working steels are used. There are also non-alloy tool steels, which are designed for cold work. There are currently six grades of non-alloy steel, which differ in their carbon content (C45U, C70U, C80U, C90U, C105U, C120U). The most popular types of tool steel for hot work include:

• 1.2367/X38CrMoV5-3
• WNL/1.2713/55NiCrMoV6
• WLV/1.2365/32CrMoV12-28
• WCLV/1.2344/X40CrMoV5-1
• WCL/1.2343/X37CrMoV5-1

What is the composition of hot work tool steel?

The most important role in all tool steels is, of course, played by carbon, which has the greatest influence on the hardness of steel. Tool steels are usually high-carbon steels. Medium-carbon steels are only used for tools that require significantly higher resistance to dynamic loads. In addition to carbon, tool steel also contains numerous alloying elements. These are primarily carbide-forming elements: Mo, CR, W, V. Through heat treatment (hardening and tempering), it is possible to combine these elements with carbon. The main task of alloying elements is to increase wear resistance and improve hardenability. Thanks to these elements, it is also possible to improve resistance to the tempering effect of heat, making it possible to maintain incredible hardness even at very high temperatures. By increasing hardenability, less intensive cooling agents can be used without any problems. In this simple way, it is possible to reduce stress and limit the occurrence of so-called hardening cracks.

The use of non-alloy tool steels

Non-alloy steels are mainly used for the production of hand tools with simple shapes. Steels with a lower carbon content are used to produce, among other things, reliable impact tools (hammers, punches, chisels, axes, cutters, etc.). Non-alloy steels with a high carbon content are used in the production of tools for metalworking with low cutting speeds (taps, drills, milling cutters, dies, etc.).

Cold work tool steels

Unlike non-alloy steels, cold work steels have increased hardenability. From a practical point of view, this means that they can be used to produce tools with much more complex shapes. Increased wear resistance is provided by fine carbides of elements such as Mo, V, W, and Cr. Steels with lower carbon content are characterized by high impact resistance, which makes them ideal for the production of chisels and riveters. High-carbon steels, on the other hand, are used to manufacture tools with fairly complex shapes (rolling rolls, cutting plates, broaching rings).