According to the research of the behaviour of nitrogel in the basic open hearth fhrnace and the basic electric are furnace, the following results were developed:
(1) The definite decrease in the nitrogen content of the molten steel during thelting in a basic open hearth furnace is visible after the occurrence of the increase in the oxygen content of the molten steel that has not Finished melting. A simple mechahical boiting would not decrease the nitrogen content of the molten steel.
(2) In a rimmed steel, the nitrogen causes an ingot segregation as in carbon, phosphorus, etc., but in somewhat less degree.
(3) In the basic electrie are furnace, the nitrogen content of the molten steel is already remarkable at the moment of melting-down. It is due to the existence of a period when the steel bath has not been fully covered by the slag. Therefore, the nitrogen absorption of the molten steel during melting may be suppressed by adding slag-formers such as lime and fluospar to the furnace bed before charging the steel scraps and thus covering the bath with slags from the primary stage of melting.
(4) In the electric arc furnace, the more free carbon (cokes) exists the greater is the amount of CaC₂ found in the slag of the reducing period, while the nitrogen increases with the CaC₂. No relation is found between the nitrogen in the slag and that of the molten steel.

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The solubility of carbon into γ-iron was investigated in high vacuum, and an abrupt increase of solubility between 1, 130° and 1, 140° was discove ed. It was presumed that the transformation of iron corresponds to the transformation due to the nitrpgen absorption. (Cf. Tetu to Hagane, Vol. 26, 1940, p. 101). In the present experiment, the correct temperature of the newtransformation was determined to be 1, 137±4°C and named "AN" point.

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In the present research, the cooling power of various kinds of the quenching media was measured more accurately than in the result of the other similar methods, by using a specially devised apparatus. Consequently, the so-called "three stages" in cooling on the cooling curve of quenching media was explained and their "characteristic points" were precisely determined. Thence a "temperature-cooling velocity curve" was plotted for each quenching medium and its threefold tendencies were classified. Besides, the effect of the temperature of quenching media on the cooling power and on the differential cooling velocity were explained.

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