Continued from the previous report on centerless grinding of alusil, this paper discusses the surface grinding of alusil. Eleven sorts of grains in GC- and WA-systems were used for grinding wheels and the optimum conditions for the grinding were researched with respect to the observation of ground surfaces.
The results obtained were as follows.
It seemed that WA-wheel gave better ground surface of alusil than GC-wheel, and well ground surface was obtained when the grain size of abrasives was rather rough and the grade of wheel was low. The ground surface with good appearance showed comparatively high value of NF-roughness. In general, the surface was better when the depth of grinding was smaller and the feeding velocity on the table was higher. In the range of these experiments, WA46.31-wheel gave the best results, and WA60H-, WA80K- wheels, etc. also gave comparatively good results.

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Al-Zn-Mg alloys have attracted public attention for their use in structural wrought alloys and casting alloys. They give good mechanical properties in the state of as welded or solution heat treated. Accordingly, the authors made experiments to examine whether high strength die castings can be produced from their secondary metals. In particular, the effects of small amounts of additional elements such as Ca, Zr, Th, Bi, Pb, Cu, etc. and also the effects of heat treatment on their properties were investigated.
The results obtained were summarized as follows.
(1) The addition of Ca gave their higher fluidity than any other elements. The addition of Zr improved their hot shortness and gave larger elongation percentage and higher impact value than any other elements.
(2) The addition of Pb or Bi improved their machinability, and also prevented them from adhesion to metallic mold.
(3) Form the standpoint of their good ageing properties, their mechanical properties were improved by heat treatment.

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Al-Zr alloys are qualified as high electric conductors having high heat resistance by their peculiar recrystallization characteristics. However, there are few reports on their manufacturing techniques covering melting, casting, and heat-treatment procedures. The effects of casting temperature, mass of ingots, and heat treatment on recrystallization characteristics of Al-Zr alloys were clear as shown in the previous reports. Preferable casting and heat-treatment procedures were of importance in raising recrystallization temperatures of Al-Zr alloys containing silicon.
In this study, the effects of silicon content on electric conductivity and heat resistance of Al-0.2% Zr-0.1% Fe alloy were investigated. It was also concerned with the effects of two-stepped heat treatment on the above properties.

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In drilling an aluminum plate by using conventional drills, a strain figure of polygonal shape (having odd number vertexes) was formed in countersinking at the early stage of drilling. The strain figure swiveled with the rotation of the drill in the progress of countersinking and this is called "walking phenomenon of drill."
At the drilling stage, when the drill margin was in contact with the material face, the vertexes of the strain figure gave a rotating scar to some depth of the hole wall, and this is called "rifling phenomenon", which caused lowering of drilling accuracy.
In this paper, drilling tests were made by using conventional drills on the plates of 9 sorts of aluminum alloys, or 1S, 2S, 3S, etc. The walking phenomenon, or swivelling motion of the polygonal figure, was discussed relating to the progress of drilling starting from the countersinking at the early stage and a relation was obtained between the walking phenomenon and drilling conditions or materials.
As the results, the swivelling speed of the polygonal figure depended upon the dimensions of drill and conditions of drilling. The speed was higher with larger angle of chisel edge or higher rotating speed of the drill. In general, it was high for hard materials and became lower for soft materials if the chips were not fully removed. It would be possible to determine the drilling machinability for any materials by the swivelling speed of strain figure.

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