Here a brief sketch is made about the hot rolling of thin sheet, such as tin plate, black sheet, and electrical sheet in order to give a general idea to those who are interested in this work.
At first the author explained the fuel used, and then the heating furnace, lastly the hot rolling itself from the practical standpoint, as he is an engineer of the rolling department of the Yawata Imperial Steel Works.

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In low chromium-high carbon steels, the magnetic transformation below 200° takes place in two steps, which were previously attributed to existence of two carbides, i. e., cementite and α-double carbide by one of the present writers. By annealing and slow cooling the specimens, the change takes place in one step. This trans-formation temperature in well annealed specimens, gradually decreases, as the chromium content increases. The corrosibility of the carbide existing in low chromium steels by boiling picrate solution gradually decreases, as the chromium content increases. From these facts it is concluded that the chromium dissolves in cementite forming a θ-solid solution, and the α-carbide is not a double carbide. β-carbide previously proposed by one of the present writers is also the θ-phase dissolving much chromium and not a double carbide.
The corrosibility of carbides by several etching reagents, and the X-ray spectrum of carbides in many alloys of this system were investigated. In this system there exist two other carbides, η-and ε-phases, besides θ-phase, above described. The η-and ε-phases are solid solutions dissolving iron in trigonal and cubic carbides, Cr₇C₃ and Cr₄C, respe-ctively and not double carbide, confirming the view of Westgren, etc.
From these results a constitutional diagram at the room temperature showing the fields in which several phases exist was constructed, that of Westgren etc. being somewhat modified.

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The phosphorus in the iron and steel gives most injurious effect on their properties as well as sulphur, so that it is encouraged to eliminate the phos-phorus as lower as possible in their manufacture.
There are many literatures as to the effects of phosphorus on the mechanical properties of steel, but as its effects change by the amount of carbon and other impurities in it, it is impossible to specify the limit of phosphorus content which is not objectionable to the properties of steel, and also it is impossible to express the change of mechanical properties by the increase of phosphorus content.
The author made the phosphor-irons which contain the phosphorus from 0.014 to 0.91 per cent with very small amount of carbon and other impurities, and he investigated the effect of phosphorus on the mechanical and physical properties of iron.

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