Continuosly from the previous report, this report contains the results of the fundamental examination on the following items.
Physico-chemical properties.
1) Properties caused by sintering.
2) Properties caused by reduction.
3) Soluble properties of phosphoric acid in 2% citric acid.

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The authors have had an examination to make high quality coke for blast furnace using the high volatile caking coal blended with our factory-made semi-coke from non-caking coal as material, both of which produced in Hokkaido.
The strength of coke, thus made, is much increased when the mother coal is blended with 20-30% of finely ground semi-coke of 0·3m/m and smaller size. Blending more than 30% rather decreases the strength sharply.
The semi-coke size to be used is the smaller the better, to the limit, below 200 mesh its complexion becomes poor on the contrary. Bigger than 0·6m/m are nearly ineffective, however.
Similar effect is found when coke-breeze is used in place for semi-coke, In that case the best adequate percentage of blending proved a little low, besides the effect too is some-what less.
Examination, also made to the semi-coke from other source, has proved that the mere blending lather spoiled the strength, except the semi-coke ground as finely as above.

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How the steel bath becomes not gasious in final period of melting process, and how the steel bath gets the standard amount of Si, Mn, C are discussed.
Thus the five objects to remelt steel scrap are all obtained. From the first report to the seventh report, the mutual correlation of the entire procedure in the acid open hearth process is physically and chemically analysed, and we knew that the whole operation which is systematised with the accumulation of experiences is generally reasonable and we are obliged to pay our respects to our senior's merit.

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(1) Author propose the new method to decide the basic open hearth slag composition which can be adopted simply and rapidly before hearth. The process is as follows: taken sample is powdered in mortar made of cast iron and sifted through 100 mesh sieve. FeO% and CaO/SiO₂ are decided from the colour of powdered sample. The fortes are as follows: the process is very simple and rapid, the results are quantitative, the vessel need not special one.
(2) The connection between the powdered colours of slag and the values of FeO% and CaO/SiO₂gained from the actual melts are shown in fig I. According to the slag composition, colour changes white, grey, black, pitch-black, yellowish-brown, brown, dark-brown, reddish-brown, and russet.
(3) Slag composition is statistically investigated. The melt-down slags are in the field ABEF (fig 2) and its center line is M-M'. Slags befor-tap are in GHCD (fig 3), its center line is T-T'. When the basicity is the same, the FeO value of the former is larger than the latter.
(4) The effects of slags upon molten bath are studied. The larger FeO% and basicity, the smaller of C% at melt-down and P% of mgot. The limit line of C 100% is C-C' line (fig 2) and of P.03% of ingot is P-P' line (fig 3).

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(I) The grain-boundaries of mild steel are harder than the interior of grains. This structure may be called "skeleton structure." When a piece of mild steel is cold-worked, the skeleton breaks, and thereupon appears the jog of yield point. Mild steel, thus cold-worked, bears slip bands both in the skeleton and in the interior of grains. When such steel is subjected to aging, the crack of skeleton are remedied by thermal motions of atoms, and precipitations are formed along the slip bands both in the skeleton and in the interior of grains. And thus the steel becomes harder. This is the phenomenqn of strain-aging.
(II) As the skeleton is remedied and becomes harder, the jog of yield point reappears.
(III) Isothermal curves for the increases of yield point and tensile strength during aging have hyperbolic forms, and they are expressed by the equations (2) and (3) in this paper. The velocity constants derived from these equations vary with absolute temperature, as shown by equation (5). If we calculate the activation energies from equation (5), we get 20, 000cal./mol. for the increasing velocities of both yield. point and tensile strength. This fact suggests that the atomic prgcesses are the same tor the precipitations both in the skeleton and in the interior of grains.
(IV) The change of the length of jog during aging goes parallel to equation (7). The reappearance velocities of yield point are expressed by equation (9) or (10). It is demonstrated theoretically that the activation energy derived from the reappearance velocities of yield point is approximately equal to that calculated from equation (5).

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The author has recognized particular structure in carburized case of Si-Mn-Cr steel containing Mo. In this 2nd report the influence of cooling velocity and that of each element Si, Mn, Cr, Mo on this structure were studied, and also the relation between this particular structure and the so-called "Bainite" was ascertained.

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The author studied as follows: (1) The influences of Cr, Ni, W, Mo, V, Ti, Cu of the high Mn-Cr steels on the high temperature (up to 800°C) mechanical properties of the high Mn-Gr steels, at the same time, for reference, on some of decrease of toughness when kept at about 700°C after quenched from 1050°C and on the scaling. (2) The effect of Ti of the high Mn-Cr-W-Mo steels on the decrease of toughness, not only at the room temperature, but also at the high temperature up to 700°C, when kept for long time at 750°C after quenched from 1050° and 1200°C.(3) The influences of C and V of the high Mn-Cr steels on the hardness and the shock value when quenched from 1000-1200°C and tempered at 500-800°C. (4) The influences of the conditions of every heat-treating process of the high Mn-Cr-V steels. (5) Additional remarks; The influences of V and Ti of 14% Cr-14% Ni-W steels on the shock value and the hardness when heated at 1000-1350°C and when kept for long time at 750°C after quenched from 1100 and 1200°C.

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