Some Contributions on Drilling Aluminium-Silicon System Commercial Cast Alloys

Abstract

Six sorts of aluminium-silicon JIS commercial cast alloys, i.e. AC2BF, AC2BT6, AC3AF, AC4AF, AC4AT6 and AC4BF, were examined on drill-machinabilities in regard of drilling resistance, accuracy of drilled holes, deposits on the drill face, chip treatment and others. The results obtained were summarized as follows:
(1) In the case of F-materials (as-cast), the drilling resistance and time were smaller in copper-containing materials, i.e. 2BF and 4BF, and were larger in 4AF, especially 3AF. And the drilling resistance and time of T6-materials (heat-treated) were larger than those of F-materials.
(2) The drilling temperature was lower in 4AT6 than in the other materials, but the temperatures were about 100∼120°C as a whole and posed no serious problem.
(3) In the case of F-materials, the accuracies of drilled holes, i.e. enlargement of the hole diameter, roundness of the hole figure and surface roughness of the drilled hole in 4AF and 3AF were inferior to those in 2BF and 4BF, and the roundness of the hole figure and the surface roughness of holes in T6-materials were better than those in F-materials.
(4) In the case of F-materials, the deposits, such as a cohesive large built-up edge, which deteriorate the accuracy of a drilled hole, were observed on the drill face. This phenomenon was more remarkable in 4AF, especially 3AF than in 2BF and 4BF. And the deposits in T6-materials were less cohesive and smaller than those in F-materials.
(5) There were no difficulties in chip formation regardless of the chip treatment.