Quantitative analysis of sulphide inclusions in free cutting steels and their influence on machinability

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• AS_18_n3_319_GRU (3,2M)

Abstract

Free cutting steels are intended for the fabrication of parts on automated machine tools. Free cutting steels have to meet the requirements set by automated parts production such as: longest possible tool life, highest material removal per unit time, chip breakability and workpiece surface quality. In describing the nature of non - metallic inclusions reference is mostly made only to the assessment of the banded structure of the inclusion. In plastic deformation soft manganese sulphide inclusions get thinner and longer while the autonomy of individual particles is retained. Plastic deformation is less efficient if the hardness of the inclusions is higher, which can be achieved by different metallurgical or chemical effects by the formation of oxide-sulphide inclusions. The shape of non-metalic inclusions can be described in various way. One of the simple ways is to describe it by the ratio of inclusion length to inclusion width. The machinability index varies with the ratio of inclusion shape, from 200 to 100%, which means that it is desirable that the manganese sulphide inclusions in steel must be as globoidal as possible. Detailed analysis of inclusions is possible only if we use highly developed, up-to-date equipment.

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A propos de : Janez Grum