Machinability enhancement of non-leaded free cutting steels

摘要

For decades free cutting steels have been alloyed with lead in order to improve machinability. Enhanced machinability is characterised by low tool wear, short breaking chips, high surface quality and low cutting forces. Although the lead content in steels is comparably low, leaded steels are under threat for environmental reasons. The EU-directive on end-of-life vehicles generally prohibits the use of lead for machinability enhancement but currently an exception for steels alloyed with up to 0.35% lead exists. Within the present work it was investigated if alternative alloying elements are capable of substituting for lead in terms of machinability. The machinability of different alloyed free cutting, carbon and case carburising steels was analysed. Thereby, it was focussed on dry machining of free cutting steels (grade 11SMn30). The evaluation of machinability was carried out by the criteria cutting force, surface quality, tool wear and chip form. The influence of cutting parameters, tool coating and cutting fluid was described.