SU1354713A1 - Steel melting method - Google Patents

Description

The invention relates to ferrous metallurgy, in particular, to methods for redistribution of chisel margins iron into converters.

The purpose of the invention is to reduce the incidence and emissions, increase the metal yield, reduce the ozone consumption and reduce the cost of steel.

The method is as follows.

The main difficulties in the conversion of low manganese iron in the converter are the deterioration of slag formation due to the reduced content of manganese oxides in the slag, which raises the melting point and viscosity of the slag melt, makes it difficult to assimilate lime and dispersion metal, leads to emissions and emissions metal and slag at the beginning of the purge and during the period of intense decarburization, reduces the metal yield. To reduce efflux and blowout emissions of low-manganese iron, the height of the tuyere at the beginning of smelting is increased, the duration of slag penetration is increased (however, the metal yield is reduced and the purge is lengthened) and the intensity of oxygen supply is reduced during the period of intense decarburization, which is also elongated.

Another disadvantage of using low manganese iron is the deterioration of the heat balance of smelting due to a decrease in heat input due to the oxidation of manganese iron. It is advisable to blow low-manganese iron with a mixture of oxygen and ozone. The use of ozone as a more ci-oxidant than oxygen allows to intensify the oxidation of impurities, shorten the duration of smelting, and improve the removal of sulfur and phosphorus and nitrogen from the bath. By adjusting the ratio of oxygen and ozone, it is possible to achieve a corresponding decarburization rate to the optimal state of the slag melt, which will ensure a reduction in emissions and emissions and increase the metal yield. In addition, ozone decomposes with significant heat generation, which compensates for the decrease in heat input associated with a reduced manganese content in the iron.

It is not possible to use a mixture of oxygen and ozone to purge low-manganese iron by means of known methods, since purging the mixture with this mixture during the entire period of oxidizing refining. Nor, laid down in these methods, will lead to a sharp increase in the processes of vynoev and emissions of metal and slag from the converter during the period of intensive decarburization.

Therefore, you need ozone in

to introduce mixtures with oxygen not during the whole purge, but only during certain periods of hydrofluor. As a result of the analysis of the processes occurring in the converter bath, conclusions were drawn

that when purging low-manganese iron in the converter, such periods are the initial and final refining periods.

The expediency of purging the mixture

ozone and oxygen in the initial period of melting is due to the need to intensify iron oxidation processes at this time, i.e. induction of active liquid slag, yjty4, assimilating lime and reducing

removal of metal from the converter, removal of sulfur into the gas phase, aided by the elevated position of the tuyere, as well as metal dephosphorization

taking into account the favorable low temperature bath. At the same time, the period of the initial slag deposition and the duration of smelting will also be shortened.

The feasibility of flushing a mixture of ozone and oxygen in the final stage of refining is associated with the need to shorten the duration of smelting due to the intensification of decarburization, which is difficult in the low carbon concentrations present in the smelting cone, as well as reducing the nitrogen content in the metal due to the direct interaction of ozone with nitrogen with the removal of nitrogen in the form of oxides and the gas phase.

In the remaining purge time, when decarburization and mass transfer processes are intensively proceeding in the converter bath, ozone is not suitable for feeding in terms of both emission reduction and emissions, and for saving ozone.

Purging a mixture of ozone and oxygen in the initial melting period of less than 20% of the total time of refining the metal with gaseous oxidants leads to a deterioration of the guidance of the active phase.

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Slag due to the lack of iron oxides, deteriorates the absorption of lime, desulfuratsky, dephosphorization increases emissions and emissions, reduces the yield of metal, lengthens the heat and increases the cost of steel.

Purging a mixture of ozone and oxygen in the initial melting period of more than 30% of the total refining time increases emissions and effluents, reduces metal output, increases ozone consumption, increases the cost of steel, and affects the processes of sulfur and phosphorus removal,

Purging a mixture of ozone and oxygen at the final stage of purging less than 10% of the total refining time lengthens melting, impairs nitrogen removal and increases its content in steel.

To assess the materiality of the claimed parameters, a series of experimental heats was carried out with a change in the claimed parameters, both within the specified parameters and with output for them.

Examples Experimental melting was carried out in a 100 kg induction furnace. Solid 1-grade manganese iron with a manganese content of 0.25% was loaded into the furnace. After the iron was melted and brought to a temperature of 1400 ° C, purging was started with a mixture of ozone and oxygen with a mixture content of 10% ozone with a mixture consumption of 4445 cm / kg, min (4000 oxygen consumption, ozone consumption 445 cm / kg min).

In the first embodiment, purging with a mixture of oxygen and ozone was carried out in the first 25% and last 15% of the total refining time of the metal. During the rest of the purge period, only

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KO oxygen. The purge was terminated upon reaching a predetermined carbon content of 0.07% and a predetermined temperature. The purge flowed normally, without emissions and terrains. The total ozone consumption was 2, LZ (cm / kg) 10. At the end of refining, the metal contained sulfur, 0.004% phosphorus and 0.0024% nitrogen. The metal yield was 90.8%.

Similarly spent melting on other options. Melting according to the prototype was carried out with a purge with a mixture of acid or ozone for the entire time of oxidative refining .., The results are shown in the table, the analysis of which shows that using the proposed method while observing the specified parameters eliminates emissions and emissions , increase the metal yield by 0.7%, reduce the ozone consumption by more than two times, reduce the cost of steel by increasing the metal yield and reducing the ozone consumption, ensure the content of series, phosphorus and nitrogen in the metal same level

Claims (1)

Invention Formula The method of steel smelting, including metal purging with oxygen with ozone additives in the amount of 3-30%, is characterized by the fact that, in order to reduce the amount of effluent and emissions, increase the metal yield, reduce the ozone consumption and reduce the cost of steel, purge the mixture oxygen and ozone are produced in the first 20-30% and the last 10-20% of the time of refining the metal, and in the interval, with oxygen.