By means of microscopic observation as well as thermal, X-ray and magnetic analyses, ' the constitution of the Ni-Cr-C system was investigated, and its equilibrium diagram was determined, as shown in Fig. 4.
In this system, there exist 7 phases, each of which is found in binary systems, that is, γ(Ni), α(Cr), G(graphite), ε(Cr₄C), η(Cr₇C₃), ζ(Cr₃C₂) and κ(CrC), and no ternary compound was in existence. The following 5 non-variant reac-tions, occur in this system the last one being inferred merely through the micro-examination:-
1) Melt (M₁)_??_α+γ+ε (1305°) 2) Melt (M₂)+η+ε (1315°) 3) Melt (M₃)+η_??_γ+ζ (1260°) 4) Melt (M₄)_??_γ+G+ζ (1240°) 5) Melt (M₅)+κ_??_G+ζ (?)

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By microscopic examination the domain of the new κ phase adjacent to α in the Cu-Si system is determined. The κ phase decomposes at 555° into α+γ on drastic annealing and, the eutectoid composition is 5.13% Si. The decomposition below 555° is extremely slow unless the samples are cold-worked. Therefore to determine the solubility curve of γ to α solid solution, the specimens should be annealed at least for 7 days after the cold-working.

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Al, Cr, Mn, V, Me, W and Cu were added singly to iron in such quantity that they form a solid solution with iron. The results of the experiment are summarized as follows : (1) Addition of Al, Cr or Mn increases resistivity of iron against sulphur, while V or Mo decreases the same property, (2) Addition of small amount of W increases resistivity of iron against sulphur a little, but much addition decreases the same property, (3) Addition of Cu has no marked influence on resistivity of iron against sulphur, (4) Corrosion-time curve of Ni resembles to that of iron, but the resistivity is small in Ni-than-that of iron, (6) Velocity of reaction of sulphur on Cu and its temperature coefficient are very large.

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The cutting efficiency of a high speed steel tool does not only depend upon the raw material, its constituent and heat treatment, but also on the form of cutting edge. In studying the cutting efficiency of tools, the measurement of cutting force on the edge is highly desirable. High speed steels used in this experiment were three kinds containing various amount of Co as follows : (i) C 0.72, Cr 4.23, W 17.76, V 0.94, (ii) C 0.75, Cr 4.20, W 19.47, V 1.68, Co 5.70. (iii) C 0.83, Cr 4.22, W 20.49, V 2.24, Co 11.60.
Steels cut were three kinds, (i) annealed Cr-steel, (ii) Ni-Cr-steel tempered after quenched in oil and (iii) austenitic stainless-steel. In the experiment, the cutting forces on the tool were measured by the testing apparatus of “Schiess Defries”, and the following terms were investigated: (1) the effect of the size of bite on the cutting efficiency, (2) the relations between the cutting force and the material to be cut, cutting speed, depth of cut and feed of the bite and (3) the effects of depth of cut and feed of bite on the cutting efficiency.
The results of this experiments were as follows:-
(1) Cutting efficiency becomes higher as the tool size increases when it is properly hardened, (2) Cutting speed has almost no effect on cutting force, (3) Cutting force is nearly in direct proportion to the increase of cutting depth, (4) as the cutting area increases, the cutting efficiency decreases rapidly, (5) as far as the present experiments are concerned, the less the feed for the same cutting area, the thinner the shavings, and the higher the cutting efficiency.

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A small amount of Ag, Bi, Cd, Co, Cr, Fe, Mo, Ni, Pb, Sb, Sn, Ti, W and Zn has been added singly to the duralumin(Cu 4%, Mg 0.5%, Mn 0.5% rest Al), and the effect of these elements on the grain-refinement of the slabs, on the age-hardening and on the mechanical properties of the duralumin has been investigated. The results obtained maybe summarised as follows:
(1) The addition of Co, Cr, Fe, Mo, Ti and W was found to be effective for the grain-refinement of the slabs.
(2) By the addition of Ag, Co, Cr, Fe, Mo, Ni, Pb, Ti and W, the age-hardening of the duralu-min was retarded.
(3) The mechanical properties of the duralumin were improved by the addition of Cd, Co, Cr (<0 6% ), Mo (<0.5%), Pb, W (<0.3%) and Zn, but the addition of Ag, Bi, Fe, Ni, Sb, Sn and Ti gave no effect.

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In the previous paper (Nippon Kinzoku Gakkai-si, Vol. 3, No. 5, 1939), the present author has established a new equilibrium diagram of the aluminium-zinc system using high purity aluminium and suggested that the peritectic reaction which occurs at 442° in the range of the alloys contailiing from 54% to 81% of zinc is probably due to the segregation during cooling.
In the present paper, more detailed experiments have been carried out for the properties of the said reaction. by means of thermal and microscopic analyses. As no thermal arrest corresponding to the peritectic reaction is detectable in the alloys which were cooled from the liquid under vibration, it was concluded that the peritectic reaction at 442° was due to the marked seggregation during cooling.

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