Corrosion properties of zinc alloys have been investigated by some researchers, but most of their reports are concerned about commercial zinc die casting alloys that contain about 4%Al. It has been found that high aluminum zinc base alloy castings containing more than 15%Al have supperior physical properties to the said commercial zinc alloys by our previous studies.
  The main purposes of the corrosion tests reported here.
  Using the water vapor exposure method were to investigate the effects of: (1) Al contents of zinc-aluminum binarys; (2) Cu and other additives of small amounts in Zn-22%Al entectoid alloy; (3) small amounts of additives in Zn-22%Al-1%Cu alloy; (4) heat treatment of alloys; and (5) corrosion on the mechanical properties of alloys.
  The results obtained are summerized as follows:
  (1) The intercrystalline corrosion becomes a troublesome problem in zinc-aluminum alloys. It is more severe in phases with different potentials such as in the fine crystallization of eutectic composition or when many phases crystalize and fine eutectoid structures are formed after they decompose.
  (2) High aluminum content alloys have slightly better corrosion resistance compared to 4%Al alloys. However, zinc-aluminum binary alloys are generally inferior in corrosion resistance even when heat treated.
  (3) Additions in small amounts of Mg, Be, Ce, Ni and Cr improve the corrosion resistance of zinc-aluminum binary alloys.
  (4) The addition of Cu is remarkably effective in improving corrosion resistance of zinc-aluminum system, of which the optimum Cu content is about 1%.
  (5) Corrosion resistance of Zn-22%Al-1%Cu alloys may be improved by adding a small amount of Mg or Cr.
  (6) Pb, Sn and Cd affect corrosion resistance of zinc-aluminum system. However, they influence high aluminum zinc base alloys less than Zn-4%Al alloys.

View full abstract

  The refinement of primary silicon in Al-(15∼20)%Si alloy has been investigated by using a flux containing phosphorus. The correlation of the refinement of primary silicon with the addition of magnesium, and the effect of magnesium on the properties of hypereutectic aluminum-silicon alloys were studied. Furthermore, the effect of some additives on the cast structure and mechanical properties of Al-(15∼20)%Si-1.0%Mg alloys were discussed.
  The results of this experiment are as follows:
  1) Less than 2.0% magnesium should be added to obtain Al-(15∼20)%Si-Mg alloys containing refined primary silicon.
  2) Magnesium addition over 2.0% resulted in the precipitation of coarse primary silicon, and feathery structure was observed at the tip of the primary silicon. Primary Mg₂Si and silicon crystallized simultaneously in the alloy containing 10% magnesium.
  3) Tensile strength of Al-(15∼20)%Si alloys increased considerably by the addition of 0.5∼1.0% magnesium.
  4) The addition of calcium increased the size of primary silicon in Al-(15∼20)%Si-1.0%Mg alloys, but titanium, tin, copper and zinc etc. each either slightly decreased, or scarcely influenced the size of primary silicon.
  5) Tensile strength of Al-(15∼20)%Si-1.0%Mg alloys decreased, by degrees, with the increase of tin addition, but elongation became profound by T₆ solution treatment. Primary silicon coarsened and tensile strength decreased markedly even with a very small quantity of calcium in these alloys. On the other hand, it was found that the addition of titanium of 0.1∼0.3%, copper of 1.0% and zinc of 0.5∼1.0% increased the tensile strength of these alloys.

View full abstract

  The object of this investigation is to elucidate the mechanism and preventives of mold wall movement of green sand mold by finding out the causes.
  Laboratory tests and pouring tests were performed to study the influences of binder-water content and amount of additives of green sand mold.
  Results were as follows;
  1) Mold wall movement increased as moisture content was elevated.
  2) Mold wall movement increased with increasing metalostatic pressure.
  3) Mold wall movement decreased by the addition of various additives, especially by certain high volatile carbonaceous additives such as pitch or seacoal, in the green sand.
  4) The presence of high moisture content layer is considered to be one of the factors affecting mold wall movement.

View full abstract

  Authors have elucidated in a past report the effects of the carbon content and the cooling rate on the structures of primary austenite and eutectic ledeburite¹⁾, studying the structures of unidirectionally solidified hypoeutectic white cast iron, containing 1.8-4.2% carbon. The present investigation was conducted to find out the effects of phosphorus on the structures of hypoeutectic white cast iron, solidified unidirectionally by the method stated in the last study¹⁾. The carbon content of these alloys were one of 1.9, 3.0 or 3.9% and phosphorus was contained within the range from 0.05 to 0.40%.
  The results of the experiment were as follows :
  (1) The distance between the stalks of the primary dendrite was independent of the carbon and phosphorus content and could expressed by the same equation used¹⁾ for iron-carbon alloys as a function of the cooling rate at early stage of solidification of primary austenite.
  (2) The second-arm-spacing of the primary dendrite became slightly smaller by increasing the phosphorus content.
  (3) The size of a group of dendrite cells¹⁾, having a constant crystallographic orientation, became smaller with the increase of the phosphorus content.
  (4) The size of a colony of ledeburite became larger with the increase of the phosphorus content.
  (5) The size of a group of eutectic colonies¹⁾ became smaller with the increase of the phosphorus content up to about 0.1%, but when the phosphorus content was more than about 0.1%, it became larger.
  (6) In low carbon samples (< 3.0%C), eutectic cementite became massive by the addition of phosphorus.

View full abstract

  In order to clarify the sintering mechanism of chomite sands, the properties of various sintered specimens and the influence of impurities contained in chromite sands on the generation of substances among the sand grains and the sintering of chromite sands were investigated.
  The results were as follows:
  (1) There was a limit to the prevention of metal penetration by the use of chormite sands.
  (2) Chromite sands contained two kinds of impurities, one of which was largely composed of SiO₂, MgO and FeO, and the other largely composed of SiO₂, MgO and Al₂O₃.
  (3) The chief components of the substances among the sand grains appeared in sintered specimens were SiO₂, FeO, Al₂O₃, MgO and CaO. The substances among the sand grains were generated by the reaction between impurities and chromite sand grains, and caused the decrease of the hot strength of chromite sand moulds at high temperatures.
  (4) The sintering of chromite sand moulds in the temperature range of 1,100 to 1,300°C occurs, not because of the substance among the sand grains, but because of the direct bonding of chromite sands.

View full abstract