The authors have found high aluminum zinc base casting alloys having superior mechanical properties in previous studies. This paper reports on the wear resistance of these alloys, particularly on the effects of aluminum contents, copper additions, additions of small amounts of other elements such as Si, Mg, Ni, Ti, Zr, Mn, Cr and V, and heat-treatment conditions. The wear tests were obtained using a OGOSHI type speedy wear testing machine for these alloys.
  The results are summarized as follows:
  (1) In zinc-aluminum binary alloys, as the aluminum content increases, the wear resistance slightly improves, but the partial welding phenomenon (scuffing) appears in all alloys as the friction speed increases.
  (2) By adding copper, the wear resistance considerably improves. It is best when the copper content is in the range of 1 to 5%. Especially, for the alloys containing more than 3% copper, the wear is not significant with the friction speed in the higher speed range.
  (3) Comparing with the commercial copper base bearing metals, high aluminum zinc base casting alloys containing copper, e.g. Zn-22%Al-3%Cu, have superior wear resistance.
  (4) By adding small amounts of silicon, manganese and titanium to the above mentioned Zn-Al-Cu system, the wear resistance somewhat improves. However, the wear resistance improves extremely by the addition of silicon and magnesium at the same time.
  (5) The wear resistance of these alloys is greater when there is a heat-treatment of 24 hours at 350°C followed by air cooling.

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  In the previous work by the authors, fluctuations in iron compositions and methods of their stabilization in cupola melting were investigated, and the phenomenon of composition fluctuations was analyzed by introducing a frequency response method. It was clarified, in that analysis, that a large mixing vessel of iron, i.e., a large capaicty of bottom well was effective in stabilizing iron compositions. However, in cupolas with a front slagging system a large bottom well had little effect upon the stabilization of iron of iron compositions, since only a part of the botton well acted as a mixing vessel.
  In this study, a rear slagging system was applied to cupola melting and attempted to stabilize the iron compositions by enlarging the capacity of the bottom well. The rear slagging system was applied to a cupola of about 1.8t/hr melting rate and two kinds of depth for the cupola bottom well was used, to find out the optimum rear slagging system.
  A bottom well with rear slagging system that was 200mm deeper than the front slagging system and a capacity of about one tenth of the hourly melting rate was confirmed to be effective in stabilizing iron compositions without decreasing the iron temperature. The standard deviation of the carbon content in iron was 0.06-0.07% and that of silicon content was 0.05-0.07%. The effect on decreasing fluctuations of silicon content was especially remarkable. In the deeper bottom well. with a rear slagging system, carbon pickup was enhanced and the standard deviation of carbon content decreased to 0.045-0.06%, but the iron temperature decreased considerably.

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  Solidification of hypoeutectic white cast iron starts by the freezing of primary austenite into a form of cellular dendrite and ends in the precipitation of eutectic ledeburite of a cellular form. The structures of the primary dendrites and the eutectic cells are markedly affected by the chemical composition and the conditions of solidification. An investigation was conducted to clarify the influences of the cooling rate and the carbon content on the structures of hypoeutectic white cast iron solidified unidirectionally in a mold with a water-cooled copper chill plate and exothermic materials. The carbon content of these alloys were within the range of 1.8% to 4.2%,
  The experimental results were as follows:
  (1) The average distance between the stalkes of the primary dendrite was inversely proportional to the square root of the cooling rate at the early stage of solidification of primary austenite and was independent of the carben content.
  (2) The second-arm-spacing (s) of the primary dendrite could be expressed by a function of the cooling rate (V_p) at the early stage of solidification of primary austenite and the carbon content (c) ;
               S = 884/V_p^0.31·C^1.48
where,      S in μ, V_p in °C/min, C in %
  (3) The primary austenite is consisted of groups of several dendritic cells, each group having a constant crystallographic orientation. The size of a group of dendritic cells was inversely proportional to about the two thirds power of the cooling rate at the early stage of solidification of primary austenite and the size became larger with the decrease of the carbon content when it was less than 3.9%.
  (4) The size of a colony of ledeburite was inversely proportional to the square root of the cooling rate immediately after the precipitation of ledeburite and was independent of carhon content.
  (5) The eutectic structure consisted of groups of several colonies lining up in parallel. The size of the group of colonies was inversely proportional to about the two thirds power of the cooling rate immediately after the precipitation of ledeburite and was influenced also by the carbon content.

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  Heat treatment was made on the white cast iron solidified unidirectionally for a given time in the mold made of exothermic material and water-cooled copper chill plate as in the preceding paper, and structural changes were observed microscopically.
  The specimen was heated at 1000°C in vacuum.
  The results are as follows:
  (1) The structural change of the eutectic Fe-C alloy by the heat treatment commences at the boundary of the ledeburite eutectic cell and gradually proceeds to the inner part of the ledeburite eutectic cell.
  (2) With hypoeutectc Fe-C alloy, the change of its structure by the heat treatment is observed first at the ledeburite eutectic cell boundary or in the ledeburite of irregular struture around the primary austenite dendrite and in the course of time, the change extends to the inner part of the ledeburite eutectic cell of regular structure.
  (3) The change of the structure of white cast iron by the heat treatment is closely related to the precipitation of graphite.
The earlier the change of structure begins, the more easily the graphite precipitates. For example the graphite precipitates easily at the ledeburite eutectic cell boundary and around the primary austenite dendrite.
  (4) There are some instances which show that the position of the graphite precipitation may be determind by the direction of solidification of the specimen.
  (5) In the high silicon content alloy, in many cases, the graphite precipitates with no remarkable change of ledeburite structure by the heat treatment.

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