The reducing velocities by CO gas were tested for a kind of limonite ore, 5 kinds of hematite ores, 4 kinds of magnetite ores and a kind of heating furnace cinder. Each ore was equally granulated in about 1m.m. dia. and 1c.c. of the granulated sample was taken in each experiment. 100c.c. of the mixed gas of CO(35%) and N2(65%) per min. were passed for some hours through the sample which was kept at 800°C. or 1000°C. in an electric resistance furnace. The % of CO₂ in the exhausted gas from the sample was analysed every 10mins. The amount of CO₂ indicated the amount of the oxygen taken from the iron ore, and thus the reducing velocities of the various ores were calculated.
The reducing velocities of the limonite and hematite ores which contained not much silica, were more rapid than those of the magnetite ores and the heating furnace cinder, the velocity of the last being the slowest.
Also the reducing velocities from Fe₃O₄ to FeO and those from FeO to (Fe. FeO) were compared in each ore and averaged. Averaging the ores which contained over 50% of iron (51 to 70% Fe) it was seen that the reducing velocity (at 1000°C. or 800°C) from Fe₃O₄ to FeO was about 2.2 times (1.4 to 3.1 times) greater than that from FeO to (Fe. FeO) and the ratio was greater for the siliceous hematite ores compared with the hematite ores which contained not much silica.
Again the degree of the increment of the reducing velocities of the various ores at 1000°C. against that at 800°C. was compared, and it was found that the degree of the increment for the magnetite ores was much greater than that of the hematite ores.
The conditions of easily reducible ore were ascertained from our experiment.

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Author intended to improve the properties of ordinary cast iron rolls (chilled rolles and sand rolls) in steel works in applying heat treatment processes (annealing or quenching), and studying concretely with many rolls, the author has induced it into practical operation with excellent success at the Imperial Steel Works, Yawata The results of experiments are as follows;
(1) For the annealed cast iron rolls, heating for more than 6hrs. at 700°C is quite effective to remove casting stresses and also to improve the properties of rolls themselves without any fear of reducing their surface hardness
(2) The quenching method for cast iron sand rolls has been succeeded to increase their surface hardness very easily and to get a splendid result in practice with no sign to cause any damage.
Thus the author has gratefully been able to propose a new important improvement in this field.

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The quenching media used for large forgings of steel are mostly rape-seed oil, fish oil and water. Generally speaking, oils are excellent quenching media when fresh or when first used, but unfortunately their good char acteristics change with age and service.
The auther of this paper has investigated the relation between the hardening effect upon the heat treatment properties of steels and cbange in service of rape-seed oil.
And comes to the conclusion by the result of many tests that the rape-seed oil produces a better structure and has an extremely long life in service.
In addition to considering the characteristics of water and fish oil.

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From the results of analyses of 30 specimens the author concluded as the following with some discussiolls:-
1. Chromic oxide is not detected remarkably in general.
2. Few thousandths of one percent of vanadium oxide are always contained.
3. Ratio Ti/Fe being 0·051-0·869, but generally it lies between 0·1-0·4.
4. Ratio TiO₂/V₂O₃ lies within 11-47 in most case.
5. The existence of chromium and vanadium in the titaniferrous iron sand is no more charecteristoc feacture; there lies nothing relations betwee titanium, chromlum and vanadium contents.

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