Decarburization

Decarburization is a generated or unwanted process in which carbon is partially or completely removed from a melt, a semi-finished product or a finished part.

The affinity of carbon for oxygen , especially at elevated temperatures, is the cause of the decrease in the carbon content in the system under consideration. The decarburization of molten steel is carried out in the refining process by chemical reactions with oxygen or in secondary metallurgy by a vacuum treatment (deep decarburization up to 20 ppm ), while in the decarburization of solids mostly only surface layers lose carbon through diffusion processes. For all materials based on iron-carbon alloys (e.g. steel , cast iron , malleable cast iron ), the decarburization processes are important for their mechanical properties. Steel materials are decarburized in long annealing processes using a hydrogen / water vapor atmosphere or ammonia cracked gas moistened with water vapor.

The depth of the surface zone of steel products from which carbon has been extracted as a result of diffusion is the depth of decarburization. Sections prepared with metallographic methods must be etched accordingly in such a way that all structural components and their grain boundaries can be identified and measured under the microscope from the edge of the section to the unchanged basic structure. This test is to be carried out with an image scale of 50: 1 and measured with an eyepiece micrometer to an accuracy of +/- 0.02 mm.

literature

• Ernst Brunhuber: Foundry Lexicon. Edition 1994, Verlag Schiele & Schön Berlin