ISOturningtool holdernomenclature

To achieve the best properties a steel material has to offer, ideally the dough microstructure should be completely martensitic by quenching.

In this case, the heated structure is a mixture of austenite (γFe) and ferrite (αFe), so rapid cooling transforms the austenite into martensite, but the ferrite remains unchanged until room temperature.

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To obtain high hardness by quenching, the material must be heated to a specified temperature to achieve an austenitic structure. If the temperature is lower than the appropriate temperature, incomplete quenching will occur, and if the temperature is too high, problems will arise in terms of toughness and ductility.

Quenching The purpose of quenching is different for machine structural steels and tool rods. For machine structural steels, the objective is to impart high strength, which, in combination with the tempering applied after quenching, is an important heat treatment to obtain the required mechanical properties. For tool steels, the objective is to obtain sufficient hardness by solid solution of carbides.

When heated to this temperature, a perfect austenitic structure is obtained, so an ideal martensitic structure can be obtained if the material is cooled rapidly and passes the Ms point.

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The hardening temperature of carbon steel is basically determined by the equilibrium state diagram of the iron-carbon system, as shown in the figure below. For example, the A3 transformation point of S45C, which is sub-eutectoid, is about 780℃, so the standard hardening temperature range is 820~870℃.

THE MICROSCOPIC MICROSTRUCTURES OF 0.45% CARBON (S45C) QUENCHED FROM THREE DIFFERENT TEMPERATURES AS SHOWN IN THE FIGURE ABOVE ARE SHOWN BELOW.