Method for producing carbon steel by using low-temperature low-silicon molten iron in 90-ton converter

Abstract

The invention discloses a method for producing carbon steel by using low-temperature low-silicon molten iron in a 90-ton converter. The method comprises the following steps of: adding waste steel in the 90-ton converter; blowing oxygen at the top and bottom to smelt; adding slag charges in different times and adjusting the position of an oxygen lance; and stopping blowing and tapping steel when the temperature of molten steel is up to 1660-1690 DEG C. Through dynamically adding the slag charges and adjusting the position of the oxygen lance step by step, when the low-temperature low-silicon molten iron is smelted, low-temperature splashing cannot be caused, and the smelting risk of the converter is effectively avoided; the consumption of lime corresponding to low silicon is reduced, and the consumption of the lime does not exceed 33kg / ton of steel; and the disadvantage of low temperature to the smelting process can be converted into the advantage for dephosphorization under the condition of controlling the stability of the process, so that the dephosphorization effect is ensured, and the smelting rate and comprehensive utilization ratio of the molten iron are increased.

Description

technical field [0001] The invention relates to a method for smelting carbon steel, in particular to a method for producing carbon steel with low-temperature low-silicon molten iron in a 90-ton converter, that is, molten iron with a temperature <1200°C and a silicon content of <0.25% before blending into the converter. Background technique [0002] For the iron and steel metallurgical process with blast furnace-converter-extra-furnace refining as the core process, the appropriate temperature and composition of molten iron in the blast furnace are the basis for ensuring the smooth flow of the process. However, as the sources of raw materials for iron and steel enterprises are increasingly diversified and the pressure of cost control is increasing, the temperature and composition of molten iron produced by blast furnace smelting fluctuate significantly, and the frequency is gradually increasing, especially in the condition of low-temperature and low-silicon molten iron. ...

AI Technical Summary

Problems solved by technology

First of all, due to the low temperature of the furnace, it is difficult to slag in the early stage, and low-temperature splashing is easy to occur, and at the same time affects the oxidation and exothermic reaction of elements in molten iron; The addition of lime and other slag materials is reduced, and the covering effect of slag materials on the converter molten pool is not ideal, which affects the chemical reaction efficiency and increases the risk of mid-term splashing, and the reduction of the proportion of slag-steel directly leads to the decline of dephosphorization effect; Finally, at the end of smelting, due to the limitations of early temperature, slag-gold reaction and other conditions, the hit rate of the end point components is low, the hit rate of the end point temperature is even lower, and the overoxidation of molten steel often occurs due to multiple spot blowing for temperature rise

[0004] At present, for low-temperature low-silicon hot metal, steelmaking enterprises have a variety of countermeasures, mainly including: 1) reduce the ratio of scrap steel, reduce the addition of slag, and increase the initial smelting temperature to a certain extent, but the ratio of scrap steel is reduced. The impact of the bottom of the furnace is enhanced, which may shorten the furnace cycle. When the slag is reduced, the hit rate of the converter smelting end point cannot be guaranteed

2) Add carbon powder to heat up. This is a more direct and very effective way to heat up. However, the addition of carbon powder directly causes severe fluctuations in molten steel temperature, which has a great impact on the control of the smelting process, and the success rate of carbon process and end point control will be significantly reduced. , ultimately affecting the refining rate of steel types; adding ferrosilicon to increase the temperature is equivalent to increasing the silicon content in molten iron, and the heating effect is obvious, but the cost increase is too large, which cannot meet the needs of the current steel industry to reduce costs, increase efficiency, save energy and reduce consumption

3) Forced point blowing at the end point to raise the temperature, as mentioned above, will cause peroxidation of molten steel, which will eventually lead to excessive consumption of deoxidized alloys, low yield of molten steel, and is not conducive to cost and consumption control.

If conditions permit, the operation of leaving slag in the previous furnace is actually to reduce the amount of slag added during the smelting of low-temperature and low-silicon molten iron, so as to reduce the influence of heat absorption by the slag on the process temperature. It is a one-time feeding method. From the perspective of temperature conditions, adding a large amount of slag at one time will inevitably cause severe fluctuations in the temperature in the furnace, which is not conducive to process temperature control; from the perspective of kinetic conditions, adding all the slag at a time , the accumulation of slag in a short period of time is serious, and the contact with molten steel is not sufficient, which not only makes the dynamic conditions poor and the reaction is uneven, but also causes the slag that melts slowly to splash at low temperature under blowing conditions, seriously affecting Smelting process control

Lime consumption, the amount of lime added is reduced from 51.25kg / t to 40.78kg / t, and its disadvantages: because it adopts a single fixed amount of scrap steel, it does not do dynamic addition, and the initial stage of blowing adopts high gun position , The way of low oxygen flow rate will significantly weaken the oxygen utilization rate, which is not conducive to cost saving and energy saving, and the average lime consumption is 40.78kg / t steel, that is, the consumption of slag is relatively large