CS263270B1 - Method of production steel! with a content of uhMcu above 0.3% - Google Patents

Abstract

In the technology of producing steel with a carbon content of over 0.3 t in oxygen converters and tandem furnaces, steel with a carbon content of under 0.15% is cast into a ladle containing 5 to 20% by weight of liquid pig iron, which liquid pig iron produced in a blast furnace with a phosphorus content of over 0.10% by weight is dephosphorized outside the blast furnace to a phosphorus content of up to 0.05% by weight before being mixed with the steel.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for the production of carbon monoxide masses above 0.3% in oxygen converters and tandem furnaces.

Production of steel with carbon over 0.3 wt. in oxygen converters and tandem furnaces it uses various technological variants such as blowing the melting to a low carbon content below 0.15% by weight. followed by carburization with solid carbons, further combined carburization with liquid pig iron and subsequent carburization with solid carbons, or a method of working on the catcher, i.e., interrupting oxygen blowing at high carbon content, by near-analysis of the finished melt.

All these variants have a number of disadvantages and limitations. Carburizing with solid carbohydrates to a carbon content of 0.5 to 0.8% by weight. it requires a considerable amount of carbohydrates, causes tapping difficulties, requires further homogenization of the steel in the ladle, and in the case of cheaper carbohydrates it brings a considerable amount of impurities into the steel. Combined carburizing is a preferred technology, but in a scarcely limited phosphorus content in pig iron, which contains phosphorus above 0.10% by weight, moreover the phosphorus of steel slag increases its content to 0.12 to 0.14% by weight. It is inefficient to produce pig iron with a phosphorus content of 0.08% or less in blast furnace conditions. Another method of producing carbon steel "on the catcher" also requires pig iron with a low phosphorus content and, in order to achieve the necessary tapping temperature, means a higher specific pig iron consumption in kg.t of steel, thereby reducing the efficiency of the converter process.

These disadvantages are overcome by the process for producing steel with a carbon content above 0.3% by weight in oxygen converters and tandem furnaces, using pig iron carburizing according to the invention. The principle of the invention is that the steel is cast with a content of less than 0.15% by weight of carbon into a ladle containing 5 to 20% by weight of liquid pig iron, whereas the liquid pig iron produced in a blast furnace with a content above 0.10% phosphorus , is phosphorized outside the blast furnace to a phosphorus content up to 0.05% by weight before mixing with the steel.

The process for producing carbon steel according to the invention makes it possible to achieve a highly efficient production of carbon steels in oxygen converters and tandem furnaces at low cost production of pig iron in blast furnaces. It is an object of the present invention to achieve, among other things, a better quality of the steel produced. Pig iron is produced in a blast furnace with a phosphorus content above 0.10% by weight and a sulfur content above 0.030% by weight; after the phosphorus outside the blast furnace, the phosphorus content falls below 0.05% by weight, the sulfur content below 0.020% by weight and silicon below 0.02% by weight. The melt of carbon steel is blown in the converter below 0.15 a and tapped into a ladle filled with phosphorous, siliconized and desulfurized pig iron in an amount of up to 20% by weight of the melt. In this way, the melting of the melt is almost to the desired carbon content rate without the need for further carbonization with solid carbons. On homogenizing devices such as argonization or vacuum station, only carbon correction is performed, thus minimal carburization by solids.

The production method of the invention allows efficient production of both carbon and alloy steel in oxygen converters and tandem furnaces without interfering with the economy of the blast furnace process, i.e., the reduction of phosphorus in the blast furnaces. It increases the quality of produced steels, enables to increase the production of converter steel plants, which is limited by the volume of converters, allows to increase production in the ladle, reduces the burn of alloys, improves the yield. Since the phosphorous pig iron contains about 0.6 to 0.8 wt. of manganese, the amount of ferro-manganese required for alloying can be reduced.

In an exemplary embodiment, a 175t melt in an oxygen converter was blown to 0.08% carbon and 0.015% phosphorus. For the production of cord wire containing 0.72% carbon, 0.45% manganese, 0.020% manganese, 0.020% phosphorus and 0.020% sulfur, 25 tons of phosphorized and desulfurized liquid pig iron with a carbon content of 4.5%, manganese were used 0.6,, silicon 0.2,, phosphorus 0.02 a, and sulfur 0.015 6. Pig iron brought to fusion 0.56% carbon, douhliphienl to 0.12,, depending on the burn was secured at the vacuum station. Phosphorus decomposition of pig iron practically did not increase the content of phosphorus in steel, in the case of sulfur content there was a decrease.

Virtually all types of steel can be produced by the technology of the invention and the pig iron volume can be selected indefinitely, since it is not limited by the high phosphorus content of the conventional and hitherto used technologies.

Claims (1)

Process for producing steel with a carbon content above 0.3% by weight in oxygen converters and tandem furnaces, using pig iron carburizing, characterized in that the steel is poured below 0.15% by weight into a ladle containing 5 to 20% by weight liquid pig iron, whereas liquid pig iron produced in a blast furnace with a content by weight above 0.10% phosphorus, is phosphorized outside the blast furnace to a content by weight up to 0.05% phosphorus before mixing with the steel.