From the study of the dephosphorization of liquid iron by the Na₂O-SiO₂-Fe₂O₃ fluxes containing CaO, MnO₂, or Al₂O₃ at 1600°C, the contributions of CaO, MnO, and Al₂O₃ on the phosphorus distribution between liquid iron and Na₂O-MgO-Fe_tO-SiO₂ slaps were derived.
The phosphorus distribution ratio and the equilibrium quotient were expressed by the following equations including the terms of (%CaO), (%MnO), and (%Al₂O₃). (i) log {(%P)/[%P]}=0.092{(%Na₂O)+0.8(%CaO) +0.6(%MnO)-0.9(%Al₂O₃)}+2.5log(%T.Fe) -3.54 (1600°C) (ii) log[(%P₂O₅)/{[%P]²•(%Fe_tO)⁵}]=8.87log{(%Na₂O) +0.1(%MgO)+0.7(%CaO)+0.6(%MnO) -0.9(%Al₂O₃)}-14.94 (1600°C)
The activity coefficients of P₂O₅ and Fe_tO were expressed in terms of the mole fraction of the slag components, and the effects of CaO, MnO, and Al₂O₃ on these activity coefficients were investigated.
The relationship between phosphate capacity and theoretical optical basicity for the Na₂O-based slags containing CaO, MnO, or Al₂O₃ was examined and compared with that for the CaO-based slag. The phosphate capacities of these slags could not be represented uniquely by the theoretical optical basicity. Furthermore, the manganese distribution observed in this experiment was analyzed and compared with that reported for the CaO-based slag.

抄録全体を表示

Desiliconisation of high silicon hot metal was carried out by injecting soda-ash at 1250°C in an induction furnace. The DSi reaction was found to depend on amount and temperature of the hot metal. But it was found to be independent on modes of additions, type of refractory materials and additives used. On the basis of experimental results and discussion it has been concluded that the DSi reaction did not proceed alone according to the proposed reaction: Na₂CO₃+Si=Na₂O+SiO₂+C The silicon was removed from hot metal both by above equation and by vapourisation of silicon by vapourisation induced process.

抄録全体を表示

Distribution of Ca-oxide, Ca-sulfide and MnS in Ca-added CC slab was investigated by new X-ray microanalyzer (CMA). The good relation between the amount of MnS and ACR, ESSP which were proposed as the parameter indicating the degree of shape control was not found. It was observed that the formation of MnS was suppressed by Ca addition even in the slab whose oxygen content was too high to form CaS.
On the other hand, calcium-aluminate inclusions were able to be divided into the following two types by the chemical composition: 1) Ca+O type; S enriched region thinly covered this type of oxides. 2) Ca+S type; S was enriched in the whole region of this type of oxides.
Compare to the Ca+O type inclusions, Ca+S type inclusions were mainly observed in the segregated area in CC slabs.
By the thermodynamic consideration, it was found that the desulfurization reaction by calcium-aluminate during solidification should be considered to clarify the shape controlling mechanism.

抄録全体を表示

The possibility of blowing control based on exhaust gas data was studied. The amount of oxygen accumulated in LD converter (O_s), which is calculated from the oxygen balance by using exhaust gas data, corresponds to the amount of FeO, Fe₂O₃ and MnO in the slag during blowing.
When the refining reaction was controlled by O_s control, the carbon, phosphorus and manganese contents of steel and the total iron content of slag at blow end were controlled at preferable levels and the fluctuations of levels were remarkably reduced. Namely, O_s is an effective parameter representing the progress of the reaction and can be used to control the blowing at an optimum level.

抄録全体を表示

The strength and ductility of cold rolled dual phase steels produced, from four different hot band structures were investigated for a 0.07%C-1.00% Si-1.54%Mn steel. The hot band microstructures were: spheroidized cementite, ferrite-pearlite, bainite-ferrite and martensite. Following 50% cold rolling these were given simulated water quenching type intercritical continuous annealing treatments to produce cold rolled dual phase steel.
The distribution of low temperature transformation products (LTTP) was affected by hot band microstructure. Bainitic hot band produced the most uniform LTTP distribution with complete ferrite grain boundary coverage resulting in marked stage II work hardening seen in Jaoul-Crussard stress-strain analysis. This structure also had the highest endurance ratio in reverse bending fatigue tests. Bainitic and martensitic hot band structures developed the highest tensile strengths when processing conditions were otherwise the same. No hot band microstructure conferred superior ductility for the strength of the resulting cold rolled dual phase steel,

抄録全体を表示

The hot ductility of a series of micro-alloyed steels has been obtained after heating directly to test temperatures in the range 600 to 1100°C with strain rates between 3×10^-2 and 3×10^-4s^-1.
At a strain rate of 3×10^-2s^-1, ductility as measured by reduction of area was generally high for all the steels examined.
At a strain rate of 3×10^-3s^-1, all the steels which showed some grain boundary precipitation, i.e., the C-Mn-Al, C-Mn-Al-Ca, C-Mn-V-Al, and C-Mn-Nb-Al steels exhibited ductility troughs in the temperature range 750 to 1000°C. It is believed that these troughs are caused by grain boundary precipitation retarding the onset of dynamic recrystallisation. The depth of the troughs was generally dependent on the degree of grain boundary precipitation and matrix precipitation, except in the case of the C-Mn-Al-Ca steel which gave only a shallow trough, even though extensive precipitation occurred at the boundaries. Steels in which no grain boundary precipitation occurred, i.e., C-Mn and C-Mn-Ti-Al steels did not show a ductility trough giving excellent hot ductility throughout the temperature range examined.
Decreasing the strain rate further to 3×10^-4s^-1 deepened and broadened the troughs in the Al, V, and Nb containing steels and introduced a ductility trough in the temperature range 800 to 900°C for the C-Mn steel. Failures in the troughs in all these cases were intergranular by grain boundary sliding in the γ and in the case of the plain C-Mn steel, dynamic recrystallisation was observed even at the temperature giving the minimum ductility. It would appear that the adverse effects of decreasing the strain rate on hot ductility is due to strain concentration at the boundaries, and to reduced grain boundary migration rates which favour intergranular failure. Again at this low strain rate the C-Mn-Ca-Al steel although showing a ductility trough, gave very good ductility compared with these other steels. The C-Mn-Ti-Al steel also gave excellent hot ductility, no ductility trough being formed even at the lowest strain rate of 3×10^-4s^-1. Possible explanations to account for the superior hot ductility of the Ca and Ti containing steels are discussed.

抄録全体を表示

S-N curves of Ti-5Al-2.5Sn ELI alloy were determined at liquid helium temperature (4K) for both the base and welded materials.
The base material had a longer fatigue life at 4K than at 77K. Welding deteriorated the fatigue properties at 4K. Internal crack initiation was seen at lower cyclic stress in both the base and the welded materials. For the base material, internal crack initiation occurred at 4K, and there were no obvious defects near the initiation sites. On the other hand, fatigue cracks generally initiated at porosity in the weldment. Internal crack initiation is considered one of the causes of reduced fatigue life.
High cyclic frequency brought about a large temperature increase in the specimen, making the testing temperature uncertain in fatigue tests at cryogenic temperature.

抄録全体を表示

Intensified energy input in the 200-t EAF by means of the twinjet burners has improved the productivity as much as 14%. The combustion in the auxiliary burners is optimum at an efficiency equivalent to the energy more than 80% of electric power. By effective use of an auxiliary combustion energy, high productivity comparable to UHP EAF can be achieved in a large EAF having difficulty to intensify the electric power input.

抄録全体を表示