Swedish iron ore products, which contribute some 12% of Western European steel producers' ore supply, originate today mainly from iron rich magnetite ore deposits, most of which are contaminated with phosphorus.
Over the years the mining companies have carried through various measures to improve and adapt the ore product properties to changing market conditions.
Since 1978 the Swedish National Board for Technical Development (STU) has been sponsoring a long term research programme in order to study alternative routes for the processing of phosphorus contaminated iron ores.
The present paper describes:
1) Mineral dressing measures to make high quality ore products from phosphorus rich ores
2) Operation of blast furnaces with 100% pellets burden made from enriched, dephosphorized high phosphorus ores
3) A way of making very fine concentrates sinterable in an ordinary sintering plant
4) How to balance the composition of a DR pellet to make it “self-fuxing” in electric arc furnace steelmaking, forming a furnace slag giving minimum refractory wear
5) How to use medium phosphorus hot metal for steelmaking, and
6) Economic comparisons of steelmaking from high phosphorus ores using different processing routes.
At the present scrap price in Sweden of US$90-100/t the route
Mineral dressing→Pelletizing (olivine pellets)→ →Blast furnace (low slag volume operation)→Hot metal desulphurization→LD-LBE steelmaking gives lowest cost of liquid steel based on high phosphorus ores.

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The pulverized iron ore has been reduced by H₂ with a batch type fluidized bed reactor of 60mm I.D. The reduction pressure and temperature are 0.5-3.6MPa and 973-1173K, respectively. On the basis of the experimental results obtained at 973K, the effects of pressure and gas velocity on the reduction rate have been analyzed according to the bubbling bed model. In the region of the partial reduction between 0% and 70%, the experimental result can be explained well by the present analysis.
The analytical results are summarized as follows:
(1)When the pressure is increased at a constant gas velocity, the reduction rate increases linearly with the pressure, independently of whether the gas supply determines the over-all rate or not.
(2)When the gas velocity is increased at a constant pressure, the increase proportion of the reduction rate decreases with the increase of the gas velocity.
(3) When the pressure is increased at a constant moral flow rate, the reduction rate increases exponentially with the pressure, but the increase of the reduction rate saturates as the gas supply approaches the rate determining stage.

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The size degradation of coke and model coke materials in tumble drums has been studied. For the model materials it was shown that current tumble strength indices are affected by size degradation due to both volume breakage and abrasion. The poor correlation between these strength indices can in part be explained by differences in the relative importance of these two mechanisms in different drums. A new procedure using presta-bilized material was developed in which size degradation was controlled by the abrasion mechanism alone. It was found that, by performing measurements in this manner, abrasion of the model coke materials could be represented as a first order rate process. The abrasion rate constant showed a strong relationship with material strength as measured by compressive strength.
Seven cokes with a relative abrasion resistance varying from very low to high were examined using this procedure. In all cases, the abrasion process was well represented by the first order rate equation and the measured values of abrasion rate constant were reproducible to±3%. The abrasion rate constant was found to increase with increasing coke size. Abrasion rate constants measured in ASTM and MICUM drums correlated well and there is potential to relate the rate constant to fundamental coke properties.

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The testing method using a vertical probe which is able to estimate both the effect of mechanical force and the reducibility on sinter degradation in the blast furnace has been established.
Several types of sinter with different RDI were inserted into the operating blast furnace by the use of this probe. The degradation of sinter was observed after recovery of the probe.
It has been found from the test that, the in-furnace degradation ratio becomes high as the RDI value of sinter increases, and that the RDI value is approximately equal to the degradation ratio when sinter is kept in the low temperature reserve zone for a long period of time (about 60min in the present test).
It has also been found that cracks in sinter can be classified into two types according to the configuration; the one is the type of linear cracking in which the structure breaks into blocks and the other is the type of radial cracking in which the structure breaks into fragments. Cracks in sinter with high RDI belong to the latter.

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between liquid iron and slag can be expressed by the following equations as
functions of temperature, slag composition and theoretical optical basicity
(Λ).
LogC_S=3.44(N_CaO+0.1N_MgO-0.8N_Al2O3-N_SiO2)
-9894/T+2.05
logC_S=14.20Λ-9894/T-7.55
logL_S=3.59(N_CaO+O.1N_MgO-0.8N_Al2O3-N_SiO2)
-0.905logN_FeO-4640/T+0.385

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Tundish performance with respect to inclusion separation has a strong influence on steel cleanliness and overall quality of continuously cast products. In the present study, experiments have been done in several 1/4 and 1/3 scale water models, (based on Froude Number criterion), as well as in a 12t real tundish to compare with model predictions. Residence time diagrams from water models and real systems are in very good agreement demonstrating that model predictions could be useful for continuous casting operation. The time for maximum absorbance, peak of the curve of a residence time diagram, was found to be and overall parameter regarding inclusion separation. Flow control devices such as dams, bales and porous plugs are effectively used as well as volume and shape of the tundish, in case of space limitations in many continuous casting machines in actual operation, specially for the case of billet casters.

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A new system for continuous monitoring of hydrogen content in line pipe steel has been developed using an electrochemical permeation method (nickel-plating method).
This monitoring system consists of two cells made from acrylic resin for nickel-plating and for monitoring, pumping equipment for supply of electrolyte and electronic equipment (Yoshizawa type). The monitoring cell can be easily set at any position on the external surface of line pipe. After nickel plating, the monitoring cell is filled with 1 or 3N NaOH solution and then the electronic equipment is operated potentiostatically at 150mV vs. Hg/HgO. Passivation anodic current decreases gradually down to less than 0.4mA/m² within one day. After such preparation, the hydrogen content can be monitored. The detection limit of the hydrogen content by this monitoring system is 0.01ppm.
A field test for monitoring the hydrogen content in line pipe is performed with high reliability over three months.

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The effect of precipitate dispersion on the development of annealing texture in an interstitial free steel was investigated using a Nb-added extra-low C steel. Size and dispersion of precipitates in a Nb-added extra-low C steel was widely changed using the same steel and keeping the grain size similar. Strong {111} recrystallization texture was developed in the specimen with coarse and sparse precipitates, but not in the specimen with fine and dense precipitates. Solute C dissolved from fine precipitates after cold rolling and during heating exists at the recovery stage and at the beginning of recrystallization in the specimen with fine and dense precipitates, but this effect cannot be considered as an important factor because of little change in {110} texture. However, independent of precipitate dispersion, {111} recrystallized grains recover faster than {100} oriented grains and {111} recrystallized grains nucleate in situ in the deformed matrices. Fine and dense precipitates strongly suppress the growth of recrystallized grain, and results in a decrease in {111} texture. Therefore a pinning effect of precipitates for grain boundary moving during recrystallization is considered to be the most important factor controlling the recrystallization texture in an interstitial free steel.

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