A charged material containing alloy iron of at least one of ferrochrome containing metallic Si or ferrosilicon, and unreduced slag containing Cr oxide generated by oxidative refining, is charged into an electric furnace as a mixture in which a mass ratio of a metallic Si amount to a Cr oxide amount is from 0.30 to 0.40, and a C concentration is in a range of from 2.0% by mass to a saturation concentration, and molten iron containing Cr obtained due to the Cr oxide undergoing reduction processing is produced, such that, when the charged material is heated and melted in the electric furnace, an attainment temperature is set to from 1400° C. to 1700° C., a maximum average heating rate in any 80° C. interval from 1300° C. to the attainment temperature is set to 15.0° C./min or less, and a minimum average heating rate in any 80° C. interval from 1300° C. to the attainment temperature is set to 3.0° C./min or greater.

A charged material containing alloy iron of at least one of ferrochrome containing metallic Si or ferrosilicon, and unreduced slag containing Cr oxide generated by oxidative refining, is charged into an electric furnace as a mixture in which a mass ratio of a metallic Si amount to a Cr oxide amount is from 0.30 to 0.40, and a C concentration is in a range of from 2.0% by mass to a saturation concentration, and molten iron containing Cr obtained due to the Cr oxide undergoing reduction processing is produced, such that, when the charged material is heated and melted in the electric furnace, an attainment temperature is set to from 1400° C. to 1700° C., a maximum average heating rate in any 80° C. interval from 1300° C. to the attainment temperature is set to 15.0° C./min or less, and a minimum average heating rate in any 80° C. interval from 1300° C. to the attainment temperature is set to 3.0° C./min or greater.

A charged material containing a metal raw material of at least one of ferrochromium containing metal Si or ferrosilicon and unreduced slag containing Cr oxide generated by oxidation refining is charged into an AC electric furnace including three electrodes, a mass ratio of a metal Si amount to a Cr oxide amount being from 0.30 to 0.40, and a C concentration being from 2.0% by mass to a saturation concentration, and operation is performed under a condition where a diameter PCD (m) of a circle passing through the centers of the three electrodes viewed in a plan view from a central axis direction of the electric furnace, an average electrode height H.sub.e (m) that is a vertical distance from a tip of each electrode to a molten metal surface, a furnace inner diameter D.sub.f (m), a molten slag thickness H.sub.s (m), a spreading diameter D.sub.arc (m) of an arc on the molten metal surface, and a deflection angle θ (deg) of the arc satisfy the following relationships to produce molten iron containing Cr.

D.sub.arc=PCD+2H.sub.e.Math.tan θ

θ=52.5−75.Math.(PCD/D.sub.f)

0.22≤D.sub.arc/D.sub.f≤0.30

0.35≤H.sub.e/H.sub.s≤1.50

A charged material containing a metal raw material of at least one of ferrochromium containing metal Si or ferrosilicon and unreduced slag containing Cr oxide generated by oxidation refining is charged into an AC electric furnace including three electrodes, a mass ratio of a metal Si amount to a Cr oxide amount being from 0.30 to 0.40, and a C concentration being from 2.0% by mass to a saturation concentration, and operation is performed under a condition where a diameter PCD (m) of a circle passing through the centers of the three electrodes viewed in a plan view from a central axis direction of the electric furnace, an average electrode height H.sub.e (m) that is a vertical distance from a tip of each electrode to a molten metal surface, a furnace inner diameter D.sub.f (m), a molten slag thickness H.sub.s (m), a spreading diameter D.sub.arc (m) of an arc on the molten metal surface, and a deflection angle θ (deg) of the arc satisfy the following relationships to produce molten iron containing Cr.

D.sub.arc=PCD+2H.sub.e.Math.tan θ

θ=52.5−75.Math.(PCD/D.sub.f)

0.22≤D.sub.arc/D.sub.f≤0.30

0.35≤H.sub.e/H.sub.s≤1.50

A monitoring method of a steelmaking process in a steelmaking vessel, wherein matters Mn, each having its respective properties PMn, are charged into said steelmaking vessel so as to produce a liquid steel and a slag.

A monitoring method of a steelmaking process in a steelmaking vessel, wherein matters Mn, each having its respective properties PMn, are charged into said steelmaking vessel so as to produce a liquid steel and a slag.

Disclosed are processes for recycling chromium oxide and producing chromium-alloy steel. Chromium oxide is reduced to metallic chromium and metallic chromium is mixed with steel to form chromium-alloy steel.

Disclosed are processes for recycling chromium oxide and producing chromium-alloy steel. Chromium oxide is reduced to metallic chromium and metallic chromium is mixed with steel to form chromium-alloy steel.

The invention relates to a process for producing low-nitrogen crude steel. This process includes melting directly reduced iron and/or scrap in a melting furnace with arc resistance heating to give a metallic melt and a slag. The metallic melt is removed from the melting furnace and used to charge a converter. The metallic melt is refined in the converter to give liquid crude steel. The liquid crude steel is tapped having a nitrogen content [N] of not more than 50 ppm, especially of not more than 30 ppm.

A method for efficiently manufacturing low-phosphorus molten steel by use of a steelmaking electric furnace, in which slag resulting from melting a solid iron source is effectively separated from molten steel, and thus a unit consumption of lime required to reduce a phosphorus content in the molten steel is reduced. The method includes: charging a solid iron source and an optional molten iron source and melting and heating these raw materials by using electric energy; partly or entirely removing slag generated during the melting; performing dephosphorization by adding dephosphorization flux; and tapping low-phosphorus molten steel thus refined, and in the method, a slag composition ratio being [CaO]/([SiO.sub.2]+[Al.sub.2O.sub.3]) of the slag to be removed is adjusted to be not less than 0.25 and not more than 0.70.