アルミニウム合金鋳物4種B(AC4B)の各種熱処理と被削性について

抄録

Since a great change is introduced by heat treatments in structures or mechanical properties of aluminum casting alloys, there would also be produced some change in machinability of the alloys. However, few studies concerning this field have been reported and many problems remain still unsolved.
This paper describes the turning tests made on so-called copper silumin, aluminum casting alloy 4B (JIS AC4B), for the object of examining the effects of five sorts of heat treatments; or T2-, T4-, T5-, T6- and T7- treatments. Cutting resistance, cutting temperature, roughness of finish surface, growth of deposit on tool surface, chip formation, etc. were discussed to find out a relation between machinability in turning and heat treatments.
The results were summarized as follows.
The cutting resistances of the heat treated materials were generally higher than that of F-material (as cast) and in particular, that of T7- material was the highest. The ascending order of the resistance was generally arranged as follows:
T2-<T5-<T6-
The cutting temperatures of T4- and T6- materials, which showed comparatively higher hardnesses, were higher than those of the soft materials; T2-, T5- and T7- materials. The roughness of finish surfaces of T4- and T6- materials was good, but that of T2- and T5- materials was bad.
The growth and adhesion of tool deposit, or built-up edge, etc., was very frequently observed on T2- and T5- materials, but seldom on T4- and T6- materials.
Chips were produced in continuous linear form at low cutting speed, but at higher speed, the chip figures were gradually changed to chopped or ground form, and they were scattered in all directions. These phenomena were particularly observed in turning of T4- and T6- materials.