In the reports “Studies of hanging of a blast furnace- I, II”, we presented the results of investigation on the hanging in the shaft of blast furnace. In this report, we studied the hanging in the lower part of the blast furnace where the temperature was high. In the test of the experimental blast furnace, a hanging occurred frequently when the temperature of combustion zone rose above 1750°C In order to explore this phenomenon, we carried out experiments on the vaporization of components of some blast furnace slag.
The results obtained are as follows:
(1) Vaporized materials were mainly composed of MgO, followed by SiO₂ and MnO, CaO and Al₂O₃ being negligible.
(2) The quantity of each of the vaporizing components was related to its content in the slag.
(3) Vaporization of MgO, SiO₂ was intensified with a rise of slag temperature.
(4) Oxidized components of slag were reduced. The reduction was accompanied with boiling action, producing a carbide.
(5) Vaporized materials seem to include lower oxides and reduced metals, in addition to the vaporizing oxidized components of slag.

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The equilibrium of oxygen in liquid iron alloys containing nickel, cobalt, tungsten and molybdenum simultaneously with H₂-H₂O mixtures has been studied at 1600°C.
Effects of alloying elements on the activity coefficient of oxygen in liquid iron alloys have been measured, and the obtained values of parameters compared with the calculated ones based on the equations introduced by C. Wagner.
As the concentrations of alloying elements increase in liquid iron, the equation comes to be unfit for our results.
The empirical formula was given for the Fe-Ni-Co-W-Mo-O system as follows:
log f^{(Ni, Co, W, Mo)}_O(corr)=log f^(Ni)_O+log f^(Co)_O+log f^(W)_O+log f^(Mo)_O
+0.000116[%Ni]·[%Co]-0.000163[%Ni]·[%W]
+0.000082[%Ni]·[%Mo]-0.000055[%Co]·[%W]
+0.000003[%Co]·[%Mo]-0.000266[%W]·[%Mo]

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Silicon and manganese are the most important elements as the deoxydation reagent in the steelmaking practice. There have been a number of reports on the deoxydation reaction of these elements. The equilibrium constants reported, however, do not show good agreement among themselves.
The equilibrium between the molten iron and the slags containing FeO, MnO and saturated silica was studied in the Si0₂ crucible at 1550°C, 1600°C, and 1650°C. The results obtained are summarized as follows:
1) The equilibrium constant for the deoxydation of silicon in the molten iron containing less than 1.2% manganese is represented as
K_Si=-17140/T+5.97
2) The effect of manganese on the activity coefficient of silicon was examined. The activity coefficient was a function of only the concentration of manganese, and not of temperature. The experimental results were represented by the equation:
log f^(Mn)_Si=0.281[%Mn]
3) The activity of iron oxide in the slag, FeO-MnO-Si0₂ system, was determined by using the relation
a_FeO=(a_O)_obs/(a_O)_sat
where (ao) obs refers to the activity of oxygen in the molten iron equilibrated with FeO-MnOSi0₂ slag and (ao) sa.t to the activity of oxygen equilibrated with pure wiistite. The activity of iron oxide was independent of temperature, and dependent on the concentration of iron oxide. It exhibited negative deviation from RAOULT'S law.
The activity coefficients of FeO (γFeo) in the binary slags such as FeO-saturated Si0₂ obtained by extrapolation to the zero concentration of manganese oxide was in good agreement with the values found in the literature.
4) The activity of manganese oxide in the ternary slags was obtained.It was defined as
K_Mn-O=a_MnO/a_MnOa_O
where KMn -0 was the equilibrium constant of the reaction Mn+O=MnO (in silica-saturated slag).
The true equilibrium constants of Kmn-0 were calculated by using the value of Kmn=ampo/aFeo [%Mn] obtained by J. CHIPMAN. The activities of oxygen and manganese were calculated from the interaction parameter of the dissolved elements in the liquid iron.
The effects of silicon on the activity coefficient of manganese were estimated by using the WAGNER'S equation. The result was expressed as a function of silicon concentration in theliquid iron:
log f^(Si)_Mn=0.550[%Si]
The activity of manganese oxide was independent of temperature, and dependent on the concentration of manganese oxide in the silica saturated slag. It showed negative deviation from the RAOULT'S law as the iron oxide.

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The drawability of mild steels containing small amounts of nickel and chromium was studied. In the low carbon steel, nickel may be present in solid solution with iron, while chro-mium is present almost entirely as carbide. Thus the dependence of the difference in drawability upon the contents of nickel and chromium would be expected.
The results obtained are summarized as follows:
1) The mechanical properties, such as tensile strength and yield strength, were found to be improved with nickel content, but the dependence of these properties on the chromium content was indefinite.
2) The annealing texture of mild steel sheets showed no change with the nickel content, but the chromium content tended to retain the rolling texture.
3) The drawability of mild steel sheets was independent of the nickel content, but it had the tendency to deteriorate with the chromium content.

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In the present paper, the following points on the characteristic properties and cooling actions of quenching oil are revealed through analysis of the results reported in previous papers:
On the characteristic properties:
(1) Simple or similar component oil does not show a remarkable quenching effect.
(2) The mixture of low and high boiling point oils shows a remarkable quenching effect, and the maximum quenching effect appears toward the side of low boiling component.
(3) The quenching effect of the mixture increases with a larger polarity of low boiling oil, and with a greater thermal instability of high boiling oil.
On the cooling actions of the mixture:
(4) In the cooling stage I (vapour film), the steel is cooled mainly by vapourization ofthe low boiling oil. In this stage, bubbles containing cracked hydrocarbons are generatedviolently.
(5) The bubbles separate immediately from the steel surface, and the duration of stage Iis short.
(6) For the cooling stage II (vapourization), the high boiling oil adheres to the surfacewith thermal cracking, consequently the steel is cooled by low boiling oil rapidly.
(7) For the cooling stages III and IV (convection), cooling proceeds mainly by low boilingoil.
(8) Thus the mixture exhibits a remarkable cooling effect.

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In order to acquire the economical, easy-to-forge alloy, having an excellent creep rupture life, various kinds of alloys were prepared. That is, N-155 alloys with one part of Nickel and Iron N-155 alloy, replaced by Manganese and Chromium respectively, the ones with one part of Cobalt replaced by Chromium and the ones containing various amounts of Chromium, Nickel, Molybdenum, Tungsten, Niobium, Nitrogen etc, with Cobalt totally eliminated.
The effects of these elements on the high temperature properties were tested.
Results obtained are as follows.
The alloys containing γ+α phases showed a more remarkable age hardening property and a considerably poorer creep rupture life at 700°C than the ones having γ single phase.
The stable γ phase was found to be the indispensable condition for acquiring an austenite steel having an excellent creep rupture strength.
In 6% Nickel+10% Manganese type alloys containing no Cobalt, the stable γ phase could be obtained if the Nitrogen content was increased up to about 0.8%. The residual alloying composition showing the maximum creep rupture life in this type alloys was about 20% Chromium, 2.5% Tungsten, 2% Molybdenum, 1% Niobium, 0.23% Carbon, and the creep rupture life of the alloy having the above mentioned composition was superior to that of N-155 alloy. Furthermore, this alloy was easily forged and proved economical, it was named 10M6N alloy.

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The authors have made a study of some effects of rare earths adlition to steel for theseseveral years. In this report, the influences of addition of the RE (rare earth)-Ca-Si complexalloys (of domestic commercial product) to stainless steels (AISI type 201, 202, 304 and 430), stainless alloy (20 series, equivalent to Carpenter 20) and heat resistant alloys (Iron-base Ni-Cr-Mo, equivalent to Timken 16-25-6; Ni-base, to Nimonic 90; and Fe-Cr-Al alloys) aresummarized. The ingot weights of type 304 and 20-series alloy were 30-50 kg, and those ofother laboratory-made ones were about 4kg, and 0'l5'-06 wt% of RE-alloys were added in thefurnace just before casting. Besides, to check up the influence of calcium and silicon containedin RE alloy, comparative specimens (added 02-05 wt% of Ca-Si alloy) of type 201, 202 and 430 steels were melted, respectively.
The authors investigated mainly the effects of RE-alloys upon microstructure, mechanicalproperties, ductility at high temperature, anticorrosion and oxidation properties: particularly, on the subject of ductility at high temperature, sub-size impact, impact-bending, torsion, bending and tensile tests were carried out elaborately.
Main results of experiments obtained are as follows:
(1) Treatment with RE-Ca-Si decreased the non-metallic inclusions in alloys, especiallyA-series (ductile sulphides and silicates) and B-series (alumina), and it appears better touse RE-Ca-Si than to use RE metals or Ca-Si alloy alone.
(2) Microstructure was not markedly influenced, but RE treatment arrested the precipitationof impurities and harmful carbides at grain boundaries, so that the corrosion resistance, particularly to the intergranular corrosion, was improved. Moreover Ca-Si treatmentdelayed the coarsening of ferritic grain-size of Fe-Cr-Al steel at high temperature.
(3) As RE elements tend to stabilize sulphides in steel, the hot-workability and hightemperature ductility were improved remarkably.
(4) In an oxidation test of heat-resisting alloy series, RE-Ca-Si alloy treated specimensshowed an increase in the scaling resistance because their oxide films were fine and hard tospall.

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From the viewpoint of protective atmosphere for heat treatment, the effects of annealingatmospheres on the primary and secondary graphitization in making black heart malleablecast iron were studied. Namely, the relations between the graphitizing process of cementitein ledeburite or pearlite structures and the annealing atmospheres were investigated by observingthe graphitizing behaviour of several single atmospheres such as Ar, N₂, H₂ CO, CO₂, H₂0 and CH₄, as well as some practical furnace atmospheres which contain hydrogen as acomponent such as the mixed gas of N₂-H₂ system, the charcoal gas generated by blowingwet air and the exothermic gas produced through partial burning of propane. Results obtainedare as follows.
When heated in the elemental gas which contains hydrogen such as 112, H₂0 or CH₄, atomichydrogen penetrated quickly into the cast iron. In these atmospheres, the number of graphiteparticles formed was decreased and simultaneously the diffusion of carbon in austeniteor ferrite matrix was lowered because the meta-stable cementite in Fe-C system was stabilizedremarkably with dissolved hydrogen. In consequence, primary graphitizing was retardedand secondary graphitizing almost stopped. In the other annealing atmospheres the penetrationinto the cast iron was so sluggish that the difference from that in the argon atmosphere wasnot recognized.
In every annealing atmosphere except hydrogen, the “bull's eyes” structure was formed bythe furnace being cooled after primary graphitization was completed. However, it was foundthat free ferrite phase was not precipitated in the hydrogen atmosphere. It was observedthat the degree of super cooling and the dilatic value at Al transformation became lowerthan in the other atmospheres.
When heated in various practical furnace atmospheres, both primary and secondary graphitizationwere disturbed rapidly with rising hydrogen and water vapor contents. The particularpreventive tendency of dissolved hydrogen was very remarkable at the secondary graphitizing stage.

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