The interaction between oxygen and phosphorus in molten iron was studied by a method of equilibrating molten Fe-P alloys with a mixture of hydrogen and water-vapor at a given ratio.
The composition of the gas mixture was so determined that slag was not formed. In order to examine the effect of temperature on the interaction parameter e ^(p) _o, experiments were performed at three different temperatures of 1540°C, 1585°C. and 1625°C, but there was almost no difference within the experimental errors.
The interaction parameter e ^(p) _o (=∂logf ^(p) _o/∂ [%P]) calculated from the present results was approximately +0.06 at an average temperature of 1585°C.

View full abstract

The process of refining by consumable electrode arc melting method is discussed based on the results described in the first report (idem, Tetsu-to-Hagané, 48 (1962) 13, p. 1654) and more experiments were successively performed.
1) Reduction of various oxides such as Al₂0₃, Si0₂ and Cr₂0₃ reacting with carbon in molten metal might be possible in the range of temperature and pressure in which the melting was carried out. And a possibility of removal of Al₂0₃ and Si0₂ generating their gaseous suboxides was discussed. Generation of the former suboxide would be impossible by thermal decomposition, but possible by carbon reduction at high temperature. The 510 could be generated by thermal decomposition as well as by carbon reduction.
2) Floating refining process which was peculiar to the method was discussed; and the analyses of oxide inclusions floated up on the surface of an ingot confirmed that the process really took place.
3) Decrease of nitrogen and hydrogen was discussed.

View full abstract

The purpose of this study was to evaluate the refining procedure during consumable arc remelting in a 2000-A laboratory-scale furnace. Electrodes used forremelting were airmelted and cast ingots of Fe-Cr alloys and commercial steels AISI-304.
The resultes obtained were as follows:
(1) The carbon in alloys acted as a powerful deoxidizer in molten pool by C-0 reaction under the reduced pressure. It was presumed that the flotation of inclusions contributed to the deoxidation.
(2) The residual nitrogen content in a vacuum-arc-melted ingot was proportional to the initial nitrogen content in electrodes used.
(3) The removal of high vapor pressure impurities such as Pb, Sn, Cu by vaporization in vacuum arc melting were not done so successfully as in vacuum-induction-melting process.
(4) Arc melting in Ar and N₂ atmospheres was also carried out with N-155 electrodes, that contained 0.20% nitrogen as an alloying elements, could be remelted successfully without any trouble in a 1/4 to 1 atm Ar-gas chamber. On the other hand, inarc melting of AISI-304 in N₂ gas atmosphere, an extremely high-arc voltage was observed and there was a remarkable nitrogen absorption up to 025%.
(5) Melting current extremely influenced the macrostructure. Highercurrent was apt to cause a coarse dendritic structure. Lower current, however, caused a worse ingot surface.

View full abstract

The annealing of low-carbon steel sheets is usually performed either by a batch-type annealing furnace or by a continuous annealing furnace. In this paper, an experimental study was made on the recrystallization behavior of low-carbon iron sheets, and on the effect of annealing processes, i. e. box-type vs. continuous type, upon mechanical properties of low-carbon iron sheets.
The main results obtained are as follows:
1) When compared with normal low-carbon steel sheets, low-carbon iron sheets has a higher recrystallization or softening temperture, and is relatively slow in recrystallization speed.
2) In the case of continuous-type annealing, more than 100.. higher annealing tempe -rature is needed compared with a batch-type annealing when the same mechanical properties and grain size are expected.
3) Batch-type or box-annealing is satisfactorily performed when the soaking time is more than 2 h, and the optimum soaking temperature is around 850°C.
4) In the case of continuous-type annealing the necessary soaking period is at least more than 3mn, and the preferable soaking temperature is not less than 900.., but when compared with the batch-type annealing method, properties of the product are somewhat inferior.

View full abstract

The author investigated the quenching-crack sensitivity and hardenability wliten the notched specimens were induction-hardened. The specimens had been prepared from Mn, Ni, Cr, Ni-Cr, Cr-Mo and Ni-Cr-Mo steels that included various amounts of alloying elements.
From the experimental results, the effect of alloying elements on that characteristics was made clear quantitatively, and an important guide to select the induction-hardening steels was obtained.

View full abstract

An investigation was made into the effects of Cu, N, Mn and Al additions on structures of Cr-Ni stainless steels and of the effects of the structures on mechanical properties and corrosion resistance.
Experimental results obtained were as follows:
i) Specimens containing Cu were hardened by precipitation of secondary ferrite and those containing N were hardened mainly by precipitation of Cr₂N and by transformation of austenite to ferrite or martensite. Specimens containing Mn and those containing Al were hardened by formation of σ phase from σ ferrite and by precipitation of Al₃Ni respectively.
ii) The grain boundary reaction which was characterized by formation of lamellar nodules occurred during aging at 750.. with specimens containing higher N content. Granular chromium carbide precipitated within grains of σ ferrite in aging with specimens containing higher Al content. σ phase was formed more rapidly from σ ferrite in aging at 750.. with specimens containing higher Mn content.
iii) The nickel equivalence of Cu and N in their ability to extend the austenite region at high temperature was about 05 and 20 respectively. The Cr equivalence of Al as a ferrite former was about 4. Addition of Mn to the steels decreased the amount of σ ferrite, but on increasing the Mn to above 4% it slightly increased the amount of σ ferrite.
iv) Tensile strength of specimens containing Cu and that of specimens containing Mn depended mainly upon the structural conditions. Solution-hardening by N was very large but effect of structural conditions on tensile strength was larger than that of solution-hardening at test temperature below 500... Tensile strength of specimens containing Al depended mainly upon the amount of AIN.
v) Increase of creep-rupture strength with increasing Cu and N contents was due to both solution-hardening by Cu and N and decrement of the amount of σ ferrite with increasing Cu and N content.
Creep-rupture strength of specimens containing Mn and that of specimens containing Al depended only upon the amount of σ ferrite.
vi) With specimens containing N, the corrosion resistance to HNO₃ reached minimum at about 0.2% of N and that to H₂SO₄ reached maximum at the same content of N.
With specimens containing the other elements, the relation between corrosion resistance to H₂SO₄ and the content of alloying elements was the same as that between creep rupture strength and the content of alloying elements.

View full abstract

In the previous report (Tetsu-to-Hagané, 47 (1969), p. 1697-1704), the author first dealt with high temperatufe load-carrying ability and structural stability of the various gamma -prime precipitated alloys of which the matrix compositions were varied from Ni-base alloys to Fe-base alloys.
In this investigation, the author studied the influence of structural stability and Ti/Al ratio of the various gamma-prime precipitated alloys containing Fe. The matrix composition of specimens were varied in Ni content with the alloys with 0% and 20% Co.
Ti Al contents were determined to be constant at 4% and Ti/Al ratios were selected in the two series of 1/1 and 4/1.
The specimens used for age-hardening, short-time tensile and high -temperature creeprupture tests and X-ray diffraction test were made from a hot-forged bar (16mm diam.) by a double-melting process consisting of vacuum-induction and vacuum-arc methods.
Regardless of the difference in the Ti/Al ratio, age-hardening and high-temperature strength properties were remarkably improved, as the Ni content in the matrix composition was ncreased.
However, age-hardenability and high-temperature strength properties of alloys with a ratio Ti/Al =4/1 were superior to those of alloys with a ratio of Ti/Al =1/1.
The deterioration of high-temperature characteristics in Fe -base alloys with ratios of Ti/ -1/1 were principally caused by the precipitation of massive. β-phases.
It was found that the Ti/Al ratio should be selected to 4/1 preventing the precipitation of massive. β-phase in Fe-base alloys.

View full abstract