Současné zvýšení odolnosti proti opotřebení a houževnatosti nástrojové oceli pomocí kryogenního zpracování – reálná možnost anebo fikce

Jurči Peter - STU Trnava (Slovak Republic)

Mechanical properties of metallic material, such a strength and toughness are in strong conflict in most cases. It means that high-strength steels, for instance, manifest a low toughness, and, on the contrary, low-carbon sheet metals with a ductility of around 40% have commonly very low tensile strength. In tool steels, their strength and hardness is closely related to the wear resistance, hence, one can naturally expect that the higher wear resistance the lower should be the toughness. One of few possible ways how the strength and toughness of metallic materials can be improved simultaneously is the grain-size refinement. This can be obtained mainly by properly chosen combination of thermo-mechanical treatment followed by well-controlled cooling down. However, this kind of treatment is inappropriate for ledeburitic tool steels from several reasons. Alternatively, it has been demonstrated over the last few years that properly done subzero treatment followed by tempering can improve the wear resistance of tool steels along with their toughness and fracture toughness. This paper demonstrates the main metallurgical principles of variations in properties of tool steels, and delineates the possible extent of these ameliorations

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