engleski

Thermally activated processes - metal forming

When the temperature is increased, the strength values (yield stress, proof stress, tensile strength) fall and the metal becomes "softer". Besides, the possible degree of deformation at higher temperatures is, as a rule, greater and the metal becomes more ductile. This change of properties at rising temperatures is widely used for metal forming. It is desirable in all forming processes to keep the required force and work as small as possible. A further requirement is that the material permit large deformations without loss in its cohesion. This is possible for nearly al metals by choosing a sufficiently high temperature. The disadvantages of hot forming are a higher rate of oxidation, increased gaseous solubility of many metals, and a lower precision of the produced workpieces. Osijek, 22. do 25. rujna 2021. 158 19. skup o prirodnom plinu, toplini i vodi 12. međunarodni skup o prirodnom plinu, toplini i vodi 19th Natural Gas, Heat and Water Conference 12th International Natural Gas, Heat and Water Conference Oxidation of the upper surface lowers the surface quality and may cause surface defects. G absorption can lead to embrittlement of the material. To avoid this, heating and forming should take place in a protective environment. Another method is forming in the so-called warm forming range at intermediate temperatures, which results in a lower rate of oxidation. The temperature range in which thermally activated processes, which lead to changes of the mechanic properties cited, occur to a significant degree, depends on the material, and in particular on melting temperature. A precise limit cannot be given, since apart from temperature, the time and the degree of deformation appear as effective factor

temperature, properties, deformation

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