Effects of copper addition on physical and mechanical properties of sintered manganese steel were studied. The results obtained were as follows :
(1) The addition of copper to iron and manganese by mixing process has not a good effect of improving the sintering between iron and manganese, as liquid phase of copper and iron-copper alloy formation prevent the sintering between iron and manganese.
(2) The addition of copper-manganese alloyed powder to iron can make alloying of copper and manganese to iron, and can increase the tensile strength as compared with copper addition only.
(3) Copper infiltrated sintered manganese steel has good mechanical properties, for example, tensile strength of 69.3Kg/mm², and elongation of 5.0%, In order to obtain sintered Fe-Mn-Cu compacts having good mechanical properties, the method of copper infiltration to sintered manganese steel is most recommended. (Received March 17, 1966)

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Some factors which affects the absorption band at near 3400cm ^-1 in the infrared spectra of α and γ-FeOOH have been investigated.
The potassium bromide pressed disks for the measuring were prepared by the mixing of the samples and potassium bromide powder using the agate mortar.
The results were as follows: The infrared spectra of a and γ-FeOOH were observed as a medium absorption band at near 3400cm ^-1 The intensity of this absorption band decreased with aging time. After 24 hours, this becomes a shoulder like form and is very weak.
From these facts, it was supposed that the near 3400cm ^-1 band is due to the O-H stret-ching of the non stoichiometric water formed by the grinding in the amorphous hydrated ferric oxide. On the other hand, the change of the intensity with time were seemed to being due the recrystallization into α or γ-FeOOH from the amorphous hydrated ferric oxide.

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Relations between basic properties of sintered WC-Co base alloys at the room temperature and the composition of the binder phase, that is, the carbon content of the alloys, have been investigated. It was found that the properties were strongly affected by the binder phase composition, although any harmful phase was not formed in-the structures of alloys. On the other hand, researches on the subject for sintered WC-Ni.alloys have never been carried out and it is still vague whether Co is superior to Ni or not as the binder metal of cemented carbides.
Therefore, studies on the properties of the WC-10%Ni alloy in relation to the composition of the binder phase were carried out. The results were compared with those already known for WC-10%Co alloy, to get an accurate knowledge on the superiority of Co or Ni as the binder metal. Specimens were vacuum-sintered at mostly 1450°C for lhr. The carbon content of alloys was closely controlled. Results obtained are summarized as follows.
(1) Sintering temperature of WC-10%Ni alloy was higher by about 70°C than that of 10%Co alloy. This shows that the temperatures at which the liquid phase is formed, are in this case higher by about 70°C than corresponding temperatures of WC-10%Co two phase alloys. (2) The two phase range in WC-10%Ni alloy extended from about 5.77 to 6.06%C in WC and the width of the range corresponded to about 0.3%C (the values in WC-10%Co alloy are about 6.04-6.22%C and 0.15-0.18%C, respectively). Based on the former result, it is clear that the free carbon phase is formed more easily in Ni-binding alloy than the other. (3) The amount of W dissolved in the binder phase varied abruptly from about 10% to 31% according to the carbon content of the two phase alloys (the value in Co-binding alloy is in the range from 2-3% to 9.10%). (4) Properties such as density, hardness, transverse-rupture strength, magnetic saturation and resistance to acidic solution, etc. showed regular changes in the phase range. These changes were explained by the composition changes in the binder phase. The maximam strength of the alloy was obtained at about the highest carbon side of the range ; however, the value was inferior to that of the Co-binding alloy. The reason may be that the content of the W dissolved in the binder phase in Ni-binding alloy is much higher than that of the other. The alloy having carbon content of less than 5.95% was found to be non-magnetic. (5) Aging phenomena taken place during annealing at temperatures as low as 800°C were not observed in the Ni-binding alloy. (6) The rapid grain growth of WC was observed in the high carbon alloys. (7) From these results, Co was confirmed to be by far superior to Ni as the binder metal of cemented carbides, except for a few cases.

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Mixtures of accurately weighed Mn, Fe, Fe₂O₄ powder were pressed into discs and were sealed in evacuated quartz tube. They were heated at 1000°C for 9 hrs, and then were quenched into water. The composition was chosen so as to enhance the following reaction quantitatively,
4yMn+{1-4(x+y)}Fe+Fe₂O₄→4Mn _yFe _1-(x+y)O
After the accurate composition was determined by chemical analysis, the quenched specimens were again heated at various temperatures for different durations in order to observe the thermal disintegration.
From the results of microscopic observations, it was found that manganese played as an accelerater of grain glowth in the wustite and showed a little influence on the known features of the disintegration.
During the heat treatments, lattice constants of manganese-bearing wustite increased over the stable limits, and those of deposited spinel increased with the increase of manganese conntent. On the other hand, those of metal phase remained unchanged.
From the results above mentioned, it was found that manganese distributed both in the disintegrated wüstite and the deposited spinel and was not included in the metal phase. It was also possible to discuss the mechanism of disintegration.

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Several factors affecting magnetic saturation of the cemented carbides were studied. It was found that the carbon content of the alloys, i.e., the composition of the binding phase was one of the most important factors, although the value of saturation was affected by cobalt and partly by impurity contents. Carbides grain size or addition of the other carbides was considered to have no effects on the saturation values. It was also indicated that the value of the alloys prepared by slow cooling was not changed by subsequent annealing at low temperatures.

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