Hardenability

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As hardenability or hardenability refers to the quality of steel , with which intensity he up to the middle (with consistent quality) hardened can be.

Procedure

In general, it can be said that a maximum of 5 mm is the limit for hardenability and one centimeter is the limit for through-hardened steel that has the same hardness outside and inside (e.g. 5 mm from above and 5 mm from below). Depending on the alloy of the steel or the proportion of alloy elements in the steel, the critical cooling rate must be taken into account, as there is a risk of cracking if exceeded. The most common quenching agents are water, oil and air, which, however, are strongly oriented towards the critical cooling speed of the respective steel.

example

A workpiece with a diameter of around 100 mm that has been treated with optimal oil quenching contains around 1% ferrite and martensite as well as residual austenite with a hardness of 340 HV ( Vickers hardness ). On the outside, however, the hardness is around 500 HV. The heat treatment is based on the phase diagram for steel. It shows graphically which temperatures are required before heating in the so-called austenite area. These lie above a characteristic line in the phase diagram, the temperature values ​​of which are marked as transition points A3 and A1. They are 723 ° C or higher.

literature

  • Hubert Gräfen, VDI-Gesellschaft Werkstofftechnik (publisher): Lexicon of materials technology. Corrected reprint, VDI Verlag, Düsseldorf 1993, ISBN 978-3-642-51733-4 .
  • Walter Crafts, John L. Lamont: Hardenability and Selection of Steels. Springer Verlag, Berlin / Heidelberg 1954.
  • Berthold Schlecht: Machine elements 2. Gears - gears - bearings, Pearson Education, Munich 2010, ISBN 978-3-8273-7146-1 .

Web links