Tool steel is a specialized type of steel designed for the production of cutting tools, dies and other precision components. According to industry standards, tool steel contains between 0.7% and 1.5% of carbon, giving it the necessary hardness and wear resistance. In this article, we will look at the main types of tool steel, their properties and practical applications in modern metalworking.
Main types of tool steel
Tool steel is classified into several main categories according to its chemical composition and intended use. Carbon tool steel contains primarily carbon as the main alloying element and is used for the manufacture of simple cutting tools. Alloy tool steel includes additional elements such as chromium, molybdenum, tungsten and vanadium for improved performance.
High Speed Steel (HSS) is a high alloy tool steel with exceptional heat resistance. According to metalworking industry reports, HSS retains its cutting properties at temperatures up to 600°C, making it ideal for high-speed operations. This type of steel contains significant amounts of tungsten, molybdenum and cobalt.
Cold-working tool steel is characterized by high hardness at room temperature and is used for the production of round hole plugs and other precision instruments. Hot-work tool steel withstands high temperatures and is applied in the production of hot deformation dies.
Chemical composition and properties
The carbon in tool steel determines its basic hardness and wear resistance. At a carbon content of 0.8% to 1.2%, an optimum hardness-to-toughness ratio is achieved. Chromium improves corrosion resistance and hardenability, while molybdenum increases heat stability.
Tungsten in high-speed steels provides high red hardness - the ability of the material to retain its cutting properties at high temperatures. Research from metallurgical institutes shows that the addition of 6-18% tungsten can increase the tool's operating temperature by up to 200°C compared to ordinary carbon steel.
Vanadium forms hard carbides that significantly improve tool wear resistance. Cobalt in some special grades of high-speed steel increases red hardness and is applied in the manufacture of disc and worm cutters for heavy duty applications.
Heat treatment and structural modifications
Heat treatment of tool steel involves a sequence of heating, quenching and tempering to achieve the desired mechanical properties. Quenching is carried out at temperatures between 800°C and 1200°C depending on the steel type and the desired final hardness.
During hardening, the carbon in the steel forms a martensitic structure with high hardness but also brittleness. Subsequent tempering process at 150°C to 650°C reduces internal stresses and improves toughness without significant loss of hardness. The correct ratio between hardness and toughness is critical for tool durability.
Specialised heat treatment techniques include cryogenic treatment and repeated tempering to stabilise the structure. Industry studies indicate that properly treated tool steel can reach hardnesses of 58-65 HRC while retaining sufficient toughness for practical application.
Practical applications in metalworking
Tool steel is widely used in the manufacture of various types of machine tools. Carbon grades are used to make simple drill bits, chisels and carving knives. Alloy marks are suitable for more complex applications such as dies and stampings.
High speed steel is the preferred material for the production of milling cutters, drill bits and broaches for high-speed machining. Its ability to retain sharpness at high temperatures makes it indispensable in modern manufacturing. Special cobalt grades are applied in the machining of stainless steels and superalloys.
When selecting a tool steel for a specific application, the factors of material being processed, cutting modes, desired accuracy and cost effectiveness are taken into account. Proper selection can increase productivity by up to 40% over unsuitable material, according to analyses in dental processing.
Frequently Asked Questions
What is the difference between carbon and alloy tool steel?
Carbon tool steel contains mostly carbon (0.7-1.5%) and is used for simple tools. Alloy includes additional elements such as chromium, molybdenum and tungsten for better performance properties and wider application.
At what temperature is tool steel hardened?
The hardening temperature varies between 800°C and 1200°C depending on the steel grade. Carbon grades are quenched at lower temperatures (800-850°C), while high-speed grades require 1200-1250°C.
Why is high speed steel more expensive than ordinary tool steel?
High speed steel contains expensive alloying elements such as tungsten, molybdenum and cobalt. The production process is more complex, but the investment is justified by the higher productivity and durability of the tools.
Can tool steel be sharpened repeatedly?
Yes, quality tool steel allows repeated sharpening without loss of properties. With proper heat treatment the tool can withstand 10-20 sharpening cycles depending on the application.
What are the main defects in the heat treatment of tool steel?
The most common defects include deformation from uneven cooling, cracks from too rapid quenching, and insufficient hardness from improper temperature. Proper process control is critical to the quality of the final product.
How to choose the right tool steel brand?
The choice depends on the material to be processed, the operating modes and the accuracy requirements. For general applications, standard grades are used, while specialized operations require high-alloy or high-speed steels with specific properties.
Tool steel remains a staple material in modern metalworking thanks to the variety of grades and opportunities for property optimization. Proper material selection and processing are key to achieving high performance in production. For more information on optimization of production processes and the selection of suitable tools, consult experienced specialists in the field.
