Method for producing ultra-low phosphorous steel by converter double slag process

Abstract

The invention belongs to the field of iron and steel, and particularly relates to a method for producing ultra-low phosphorous steel by a converter double slag process. The method comprises the following steps: 1) adopting a conventional feeding process in the early stage of blowing, and when the amount of oxygen to be blown accounts for 25 to 35% of total required blown oxygen amount, adding 1 to2 Kg / t of Al2O3 and 0.75 to 1.5kg / t of limestone into a converter; 2) when the amount of oxygen to be blown accounts for 30 to 40% of the total required blown oxygen amount, performing a deslagging operation, and then adopting the conventional feeding process; 3) when the amount of oxygen to be blown accounts for 90 to 100% of the total required blown oxygen amount, adding 0.75 to 1.5kg / t of Al2O3 and 1 to 2kg / t of limestone into the converter, thus obtaining the ultra-low phosphorous steel after the converter blowing is finished. The Al2O3 and the limestone are added to make slag during primary deslagging, so that the melting point of slag can be reduced, the fluidity of the slag is increased, the dephosphorization efficiency before deslagging is improved, and the phosphorus content is reduced to 0.025% or less during primary deslagging; the Al2O3 and the limestone are added at an end point of the converter to improve the flowability and foaming of the slag, the temperature of moltensteel is not reduced, and the slag-steel interface reaction temperature is reduced to improve the dephosphorization efficiency, so that the phosphorus content can be reduced to 0.005% at the end point of the converter.

Description

technical field [0001] The invention relates to metallurgical technology, in particular to a method for producing ultra-low phosphorus steel with double slag in a converter. Background technique [0002] Dephosphorization of molten steel has always been an important part of the converter smelting process. There are two main factors affecting the phosphorus content at the end of the converter: one is the thermodynamic reaction conditions, which require high alkalinity and oxidative slag to be produced and lower the temperature; the other is kinetic conditions. It is necessary to make foam slag well, strengthen stirring, increase the reaction speed of steel slag interface, and ensure that the phosphorus in molten steel is quickly transferred to the steel slag interface for dephosphorization reaction. The key link in the production of ultra-low phosphorus steel is the dephosphorization effect of the first slag dumping process of the converter and the phosphorus distribution rat...

AI Technical Summary

Problems solved by technology

[0005] In the existing process, the production of ultra-low phosphorus steel adopts the double slag dephosphorization process. Even if a large amount of slag is used, a high oxidizing atmosphere and high alkalinity slag are used, it is still difficult to reduce the phosphorus content at the end of the first slag dumping and the converter.

(1) Due to the low temperature (about 1340°C) during the first slag dumping, high melting point of slag, poor fluidity, and poor kinetic reaction conditions for dephosphorization reaction, although the thermodynamic conditions meet the requirements, the phosphorus content in the double slag process still does not decrease 0.04-0.06%, resulting in high phosphorus content in the end point of the converter, beyond the target range; (2) High end point temperature of the converter is very unfavorable to dephosphorization, but in order to ensure the temperature of the subsequent process, the end point temperature cannot be lowered too much, in order to Satisfy the requirements of end point control and post process, the end point phosphorus content of the converter is about 0.01%, the lowest can only be reduced to 0.008%; and the slag consumption in the converter smelting process is large, and the furnace lining is severely eroded

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