Abstract: A process for producing a steel in at least two converters using a great or substantial amount of an iron-bearing cold material. The iron-bearing cold material and a carbonaceous material are supplied into one of the converters under the presence of a molten iron or a preliminarily treated molten iron and are melted therein under oxygen-blowing to obtain a preliminarily treated molten iron containing a high content of carbon, and the preliminarily treated molten iron is refined in the other converter under oxygen-blowing to obtain a molten steel having the given composition.

Abstract: Methods for controlling blowing, controlling the slag formation and predicting sloping in the blowing of molten pig iron in LD converter are carried out by measuring acceleration of the horizontal movement of a detector, such as a lance provided in the converter, which is caused only by the slag impinging against the lance, by an accelerator, integrating the measured values to obtain integrated average values at every several seconds, and programming the integrated average values in a computer.