Formerly¹⁾ the author reported the general conclusion on the characteristics of coalite used for manufacturing metallurgical coke as reinforcing material for the fibrous constituent which is the main part of coal.
This time the author manufactured 92 kinds of coalite from Chuo coal and Takamatsu coal, and some kinds of coalite from Takashima coal and Iwojima coal under different conditions and then the relation between the manufacturing conditions and the reinforcing quality was studied on them.

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The grain controling method of silica brick is very effective for the improvement of the properties of silica brick.
In this report, as first step, the meaning and the method of grain controling is explained and next, the application of this method to the manufacture of silica brick is being treated.
As a result of studies, it was understood that the grain controled silica bricks have the following properties.
1. Low porosity: very available for the roof brick of the open hearth furnace.
2. High resistance to spalling: very available for the roof brick of the electric furnace as intermitted operation.
3. High resistance to abrasion: very available for the inside brick of the rotary kiln.
4. High viscosity in the melting state: very available for the utilization of the second class raw materials.

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In foreign countries, the influence of zirconium on iron and steel was studied quite a considerable time: the results were put to practical use. but, in Japan, there are few published systematic studies about this influence of zirconium, in fact, still many unknown points about the effects of zirconium and no commercial uses of it.
The author has studied about this problem since 1941 and reports on this essay I, the influence of a small amount of zirconium on iron and steel, mostly, the results of elemental studies in laboratory scale.
The results of these experiments are summerized as follows.
(1) Commercial zirconium mother alloy of differentiated methods of preparation in assortment, chemical composition, action and yield in melting were tested.
(2) When a small amount of zirconium is added into steel, blowholes in ingot can be reduced and sound ingot gotten, and oxygen and nitrogen contents in ingot can be reduced. The degree of deoxidizing action is stronger than silicon and pretty weaker than aluminium. Zirconium greatly reduces the percentage of acid-soluble nitrogen in an ordinary steel.
(3) Pretty clean steel can be obtained with moderate treatments and many characteristic inclusions are recognized in zirconium-treated steel. Compositions and forms of these inclusions were studied.
(4) Desulphurising capacity of zirconium is stronger than manganese and the maximum value of desulphurisation percentage was 65%.

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In the first report, expriments on the influence of oxygen on the grain size and hardenability of pure carbon steel was described in detail, that is, in pure carbon steels, grain size is influ enced by the presence of oxygen, moreover, hardenability is distinctly retarded with an increase of oxygen content.
However, in commercial steels, as various alloying elements are contained, it is necessary to clarify the influence of oxygen on these steels containing the third element, and then to apply the most appropriate refining method to make these steels.
In this second report, the author has tried to study these infiuences on pure nickel steels containing a certain amount of carbon and various amounts of oxygen.
Results obtained are as follows:
1) Pure nickel steels containing a little oxygen and much oxygen have greater tendency to form grain growth at the temperatures between 930°C and 1050°C than that containing medium amount of oxygen.
2) In pure nickel steels containing a little nickel and much oxygen, abnormal structure is apt to appear in the carburized samples; however, even if nickel content increases in the steel containing much oxygen, abnormal structure is not observed,
3) Pure nickel steels containing much oxygen have distinctly lower hardenability; however, even if nickel content increases in such steels, they become to have the same hardenability as that containing less oxygen.
4) From above mentioned facts, it is revealed that nickel neutralizes the injurious effects of oxygen in steel. On the other hand, it is said that flakes are apt to break out in nickel steels; therefore, it is thought that the practical refining of nickel steels has to be performed chiefly to remove hydrogen, even though it causes an increase of oxygen to some extent. However, it has not yet been clarified that whether these results depend upon only the effect of oxygen content or not.

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The authors have tried to get the relation between mechanical properties of some alloy steels, such as Ni-Cr-Mo, Mn-Cr-Mo, Cr-Mn or Cr-V, and the practical applicability for the forging die block, but they have failed to find the exact relation between them. Then, for this purpose, they have devised. the special testing machine, which shows the relation between the number of blows of small hammer striken on the cylindrical specimen and accumulated infinitesimal deformations of that specimen induced by the blows under high temperature condition. The accumulated deformations are measured with the micrometer.
As the testing condition above mentioned and the actual condition of die block under application are so similar that some exact relation between the results obtained by that testing machine and the endurance of die block must exist
The results are as follows:
1) Above 600°C substitute steels (Cr-Mn, Cr-V, etc.) show the abrupt increase of deformation, but at lower temperature than 600°C the deformatioon of Cr-Mn steel is less than that of Ni-Cr-Mo steel. (by the testing machine.)
2) In the case of the deep impression or the large die, the life of Cr-Mn die is shorter than that of Ni-Cr-Mo die. Nevertheless, in other case, the endurance of Ni-Cr-Mo die is not always longer than the others. (by the results of actual measurements of forging dies under application.)
3) As we know, in the former case, the temperature of some portion of die often becomes several hundreds degrees, we can recognize that good correlation exists between the results by the laboratory testing machine and the life of die block.
4) The mechanical test of the actual die block are also performed.

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Graphitisation times, mechanical properties and fluidities of malleable castings containing 2.4% carbon, 0.7% silicon, 0.5 (1.0, 1.5)% copper and 0.05 (0.1, 0.3)% aluminium are studied:
(1) The addition of slight amount of aluminium effects strongly to shorten the graphitisation time of first stage, e.g. from 16 hr 30min. to 2 hr 15min.
(2) All specimen casted in sand mould 5-40mm thick show white pig fracture.
(3) Fluidities of this molten metal are injured by addition of aluminium, but improved this injured fluidities by addition of copper.
(4) The best mechanical properties are obtained by precipitation hardening treatment after graphitisation of first stage, e.g. tensile strength 78kg/mm² and elongation 4%.
(5) The addition of aluminium effects decreasing the tensile strength and elongation percentage and transform the shape of graphite from sphere to star and the addition of 0.3% aluminium causes to precipitate the primary graphite.

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