In this report the behavior of sulphur in the molten phase was studied.
The amount of sulphur which transferred to slag from steel bath during melting period seemed somewhat to be influenced by the basicity of slag at the earlier period of melting period and at "melt down". Some investigations were made upon the influence of sulphur in iron ore or lime, the fluidity of slag and the "slag off" on the behavior of sulphur in steel bath during refining period.
The fluidity of slag seemed to have a decided influence on the change of sulphur pct. in steel bath.
The change of sulphur pct. in the ladle was studied. The relation between sulphur partition (S)/[S] and the basicity, and besides between [S] and the fluidity of slag was studied.
The desulphurization action in the open hearth furnace seemed to proceed mainly by sulphur transfer between slag and bath or diffusion of sulphur in slag rather than by desulphurization reaction.

抄録全体を表示

Constructing the following electrode concentration cell, authors measured electromotive force corresponding to the change of silicon content in iron by a potentiometer.
The temperature range of the experiment was 1, 520-1, 530°C and for measurement of the temperature a Pt-Pt-Rh thermocouple was used. As preliminary experiments, the reversibility and thermoelectromotive force were investigated.
The theoretical relation between electromotive force E and the activity of silicon a_Si was as follows:
where a'_Si: the activity of pure silicon
aⁱ_Si: the activity of silicon ion in the molten slag.
Because pure silicon was selected as a standard state, then the following equation was obtained from eqn. (1)
n was approximately determined as n 4 by calculation from the authors' data.
The activity of silicon was obtained by substituting the values E, n and T to eqn. (2).
Being judged from this result, Fe-Si binary solution was recognized to be a semi-regular solution and obeyed to Henry's law up to about n_Si=0.10
Furthermore, the free energy change ΔG⁰_{1, 793} of the following reaction at 1, 520°C was calculated from the author's data.
ΔG⁰_{1, 793} represented the free energy of solution of silicon at unit activity on a scale in which the activity was equal to percentage at infinite dilution. To convert this to activity on a mole fraction scale in which the activity of pure liquid silicon was unity, the following eqn. (4) was required
From the relation between log(A_Si/n_Si=γ_Si) and square of the mole fraction of iron n²_Fe, activity coefflcient γ⁰_Si which represented γ_Si at n_Fe=0 was obtained as 0.013. and the mole fraction of silicon in dilute solutions was 0.0199 times its weight percentage. From these two values, the ratio of the activities of silicon on the two scales was obtained as 0.00026.
Substituting this value to eqn. (4), authors obtained the following value

抄録全体を表示

Being suggested by the characteristics derived from the results of the previous report, the author measured the decomposition voltages on the system BaO, C2O-SiO₂ and also in this case it was clear that the results conld be treated like in the potentials. Accordingly, both results being combined together, the next relations was obtained between potential E and a_SiO2, a_CaO
a_BaO was calculated by means of the Gibbs-Duhem's equation.
The derived activity values were satisfactory in comparison with previously calculated and obtained ones.
Subsequently, according to these results, the author discussed the forms of activity line, and referring to the constitution of molten slags, introduced the concept "ion pair".
Furthermore, the character of the silicate ions was discussed.

抄録全体を表示

The authors studied on the characteristics and differences of acid and basic open-hearth furnace steels regarding the changes of grain size during the steel making process. The result obtained were as follows:
1) The grain size of basic furnace steel was irregular and that of acid furnace steel was homogeneous at every stage of steel making process, but the grain size of both the steels during the steels making process showed the same tendency of change. But the basic furnace steel which was deoxidized by additional ferro-silicon to the furnace before tapping, showed the homogeneous grain size after addition of its deoxidizer, and it is alike to acid furnace steel.
2) Grain size of the acid furnace steel in ladle was coarse compared with that of basic furnace steel, but it was homogeneous. Basic furnace steel showed fine but irregular grain size.
3) The refining reactions of the acid furnace were slow and thorough in the furuace, but the refining reactions of basic furnace were heavy aad imperfect in the furnace; and as deoxidizers were added into ladle, deoxidizing reactions were continued during the ingot casting process in the ladle. And amount of additional aluminum into ladle as deoxidizer was 0.03% in case of basic furnace and 0.01% in case of acid furnace.
4) It was thus evident that characteristics and differences of grain size in both the steels were caused by different refining methods of both furnaces.

抄録全体を表示

As a high-tensile steel sheet for ship-building a Mn bearing low alloy steel like DS was hitherto used, but since electric arc welding became widely applied for the purpose of saving weight and labor, high tensile steel of superior weldability has been in demand. This study was made by the Japanese Navy technical staffs during the World War II.
Eleven kinds of steel regarded as being suitable for welding were selected with reference to the Japanese and foreign technical literatures.
Thirteen kinds of steel in all including DS and HT selected for comparison with these steels were melted with a high frequency furnace and then rolled into sheets of 12mm width. The mechanical properties, weldability and strength of butt-welded joint of these experimentally manufactured steel sheets were tested. As a result of tests, it was confirmed that DS and HT hitherto used had quite inferior weldability, while Si-Mn steel showed the most excellent properties.
In view of the test results and from the standpoint of mass production and domestic natural resources, the standard of the components of steel experimetally manufactured by an O.H. furnace was determined as follows: C 0.15-0.20%, Si 0.3-0.7% and Mn 0.9-1.2%. Eight charges were melted, poured into 6-18t ingots and rolled into 12-22mm wide sheets in the Kure Naval Arsenal and Yawata Iron Works. Several types were performed on these experimentally manufactured sheets, and they showed generally satisfactory results.
Mechanical properties of these sheets were as follows: Yield point 32-43kg/mm², tensile strength 52-60kg/mm², elongation 23-32% (G.L.=200mm)
Trial use of these sheets for construction of submarines with an application of welding showed excellent results without causing any defects.

抄録全体を表示

In sequence of to the former report, the effect of boron addition on mechanical properties of constructional alloy steels in different conditions of heat treatment were studied. Results obtained were summarized as follows.
1. Proper Al-Ti-B treatment gave favourable effect on notch toughness when the steel was completely hardened and tempered at temperatures lower than 400°C, but if excess addition of boron was made, some adverse effect appeared at higher tempering temperatures.
2. In the case of incompletely hardened and tempered states, if the microstructure of ashardened specimen consisted of martensite and bainite, boron gave benefical effact on strength and toughness because it increased the percentage of martensite, but if hardening was so unsufficient that there appeared proeutectoid ferrite and pearlite at the grain boundary with smaller percentage of martensite, slight decrease in notch-toughness occurred as well as in fully annealed states.
3. Also effects of intermediate transformations by austempering on the mechanical properties and low temperature notch-toughness were studied.

抄録全体を表示

Specimens of the ball bearing steel, SUJ 2, were heat-treated by subzero-treatment, oil quenching and tempering, martempering-oil cooling, and martempering-air cooling. Some groups of these were tested in the static notched bending of charpy-type specimens and the compressive breaking of ring shaped one, and the other were studied as to the dimensional stability of retained austenite by various quenching methods. The quantitative determination by pointcounting and lineal analysis was carried out in microscopical methods.
The results of experiment were as follows:
1) In the ball bearing steel, SUJ 2, the coarsening temperature of austenite grain was at 870°C, duplex range was from 930°C to 1050°C, and quenching crack was generated by quenching from above 850°C austenitizing temperature. Considering above these, retained austenite and carbide solubility, the best austenitizing temperature was at 840°C±5°C.
2) In the comperessive breaking test the oil quenchihg and tempering was superior to subzero heat-trsatment, but there was the tempered brittleness at 180°C and 250°C tempering temperature in the static notched bending test. In sabzero-treatment there was no notched brittleness. Both martempering heat-treatment made the specimens generate the primary acicular bainite, and on account of it hardness was too low, but the mechanical properties were very good.
3) From dimensional stability at room temperature by various quenching the experimental equations were gained:
Sabzero treatment…
Oil quenching…
Interrupted quenching…
4) Lineal analysis and point-counting with microscopical photographs without the Hurlbut counter were inadequate for quantitative determination of this degree's retained austenite. Lineal analysis was more convenient in quantitaiive determination than point counting.

抄録全体を表示

Description was made on the development of titaniferous magnetite smelting, and the properties of high titanium slag. The present states of high titanium slag making were also mentioned.

抄録全体を表示