SU1425213A1 - Method of converter treatment of vanadium pig iron in duplex process - Google Patents

Abstract

The invention relates to the field of ferrous metallurgy, more specifically to the methods of redistribution of vanadium-containing cast irons by a duplex process into a converter ah. The purpose of the invention is to improve the quality of the slag produced, reducing the consumption of pig iron and the cost of steel. The method includes, at the first stage of the process (upon receipt of vanadium slag and carbon semi-finished product) filling into a converter before pouring iron into steel scrap in an amount of 5-12% by weight of liquid iron with a ratio of lightweight to total scrap (0.6-0.8): 1 and heating, up to 400-700 ° C. At the stage of decomposition, steel scrap is used, mostly lightweight, with a certain well developed surface and, as a rule, substantially oxidized. Preheated scrap, on the one hand, is itself a source of iron oxides, which play an important role in the process of cast iron devanadiation — the formation of vanadium spinel. On the other hand, lightweight scrap, located on the surface of the converter bath, is predominantly oxidized at the beginning of the purge, which additionally introduces iron oxides into the slag. Steel scrap, due to chemical interaction with liquid iron, has time to dissolve Along with reduced scale consumption (using scrap) and, accordingly, the amount of unreacted oxides, it reduces the anisotropy of slag properties and reduces the content of metal inclusions in it. A lower concentration of ballast impurities in steel scrap compared to scale and cast iron increases the concentration of VjOj in vanadium slag. A significant improvement in the quality of the slag is ensured by the preliminary uniform heating of the steel scrap at the stage of the cast iron decomposition. This is achieved by adding scrap to the converter for a high-temperature vanadium donkey left from the previous smelting, and heating the scrap to AOO-700 C before pouring the iron, at a ratio of de-KOBecHofi of the scrap and its total amount (0.6-0.8) :one. The method allows to improve the quality of the slag produced (increase the average size of the spinel grain VjOj, reduce the number of metal inclusions), reduce the consumption of liquid iron (by 50-150 kg / t) and the cost of steel. 2 tab. cl with to SP

Description

ten

25

This invention relates to ferrous metallurgy, in particular, to methods for redistributing vanadium-containing cast irons to a duplex process in a cockverter; The aim of the invention is to improve the quality of the slag produced, to reduce the consumption of pig iron and the cost of steel.

The goal is achieved by filling the converter with steel scrap in the amount of 5-12% of the mass of cast iron at a ratio of leg, total and total scrap (): before zapivka pig iron and heat it to 400 - 15 700 ° С.

At the stage of the Devanadi C, steel scrap is used, mainly lightweight, with a well-developed surface and, as a rule, 5 is essentially oxidized; Poetog-g; on one side, the scrap, especially the preheat, is the source itself; iron oxides 5 which play an important role in the 3 proDefess of de-casting iron — the formation of vanadium spinel C (Pe „Mg IfoJO (V, Cr, Fe,, and on the other hand: lightweight JTOM, located on the surface of the converter Ianna, The minutes of purging are predominantly oxidized, which additionally adds oxides of gel: In the shak, absorption 5 in this way., the phase metal surface - slag with the natural material - accelerates the formation of: due to the increase in the relative corrosion (vanadium oxidation)

I. Steel scrap due to the sourdough interaction with liquid iron manages to dissolve over the rapidity of the flow of the virgin period, which, together with reduced scale consumption (when using scrap) and, accordingly, the amount of unreacted oxides, reduces anisotrophication. - due to the properties of the pshak and the content of metal inclusions in whom the bolae low concentration of baplasse auxiliaries in the steel scrap compared with dross and cast iron contributes to the magnitude of the concentration, О j in the ionic hapak.

A significant improvement in the quality of the pack is ensured by the pre-heating of an uninterrupted heating of steel scrap. At the stage of davadadia of the pig iron, the addition of a scrap of overhead to high-temperature wa is achieved.

t

35

40

45

50

ten

25

15

20

five

0

five

0

previous smelting and heating of scrap with an oxygen-oxygen torch up to 400-700 C before pouring iron.

At temperatures of 400 ° C and more, the oxidation rate of iron increases abruptly in the wustite layer in the scale. As a result, ne -. The heat of the scrap and after the scrap is heated in an atmosphere of air is oxidized on the scrap surface, which is one of the advantages of the proposed method for the duplex smelting process.

Heating scrap above 700 C is impractical due to the loss of metal with emissions when casting iron into the converter. due to the over-oxidation of lightweight scrap, as well as a significant reduction in the rate of heating of the scrap to higher temperatures, and thus loss of productivity.

The heterogeneous, highly viscous vanadium slag heats the lower layers of the scrap without slagging it. At the same time, it is cooled by the transfer of heat. Scrap, vanadium slag forms a skull - it is welded to the bottom of the converter, which further in the process of de-intensification intensifies the oxidation of vanadium in the depth of the metal. bath, and the start-up particles melting and floating from the bottom of the pshak are the formation of vanadium spinel. As a result, the formed slag has an enlarged spinel grain. However, the best indicators of slag quality, as well as a high level of vanadium extraction from cast iron into slag, are achieved when used in the main. Mr. lightweight scrap with a gross weight of 0.9-1.1 t / m, namely when the ratio of the lightweight part of the scrap and its total quantity (0.6-0.8); 1. The remaining ordinary scrap (packages, cutting of blooms and slabs, knife and flame cutting) has a bulk weight

 l, 8-2.5 t / m

An increase in scrap density, as well as its total amount (over 12% i by weight of cast iron) does not ensure the dissolution of pieces of steel scrap during the period of devantation, and also worsens the extraction of vanadium from cast iron into slag due to a decrease in the interfacial surface and slowed down mass exchange in the metal zones. pic bath around insoluble scrap.

The increase in the share of lightweight scrap in the charge excessively overcools the metal bath at the beginning of the purge, the oxidation of vanadium is slowed down due to diffusion difficulties and, consequently, the slagging process worsens, which is expressed, in part, in a decrease in the average size of the spinel grain of vanadium slag. Reducing the total amount of scrap (less than 5%) levels the effectiveness of its use (Table 1).

Example. B 22-ton converters duplex-process with getting at the first stage (de-stabilization) of van-slag slag and carbon semi-finished product, and at the second stage vanadium-containing iron, are processed,

Comparison of limestone

containing,%: C 4,5; V 0.45; Si 0.24; 2o and the proposed shows that the pre-Mp 0.25; Ti 0.25; Cg 0.08; P 0.05; S 0.024, having a temperature of 1320 C. Purging the metal in the first stage of the process takes 8 minutes while simultaneously supplying oxygen through the upper lance and nitrogen through the lower tuyeres with a flow rate of 45 and 2-4, respectively. In the second stage, carbon semi-finished product is blown up to the steel of the type ZSP in another converter. In this case, lime is loaded into a carbon converter before the intermediate product is filled in the amount of 25 kg / ton. B- as coolers at the stage of decomposition when redistributing vanadium-containing pig iron by hard methods use solid cast iron (2 tons) and scale (0.6 tons) or only scale (1.4 tons). Solid iron is placed in an empty asonverter before casting iron, and scale after casting iron.

The proposed method as coolers use steel scrap in the amount of 1-2.4 tons (5-12% by weight of iron), including lightweight 0.7-1.7 t, with a ratio of the total amount of scrap and lightweight part 1: (0.6-0.8). Scrap. The applied method allows to improve the quality of the slag produced (to increase the average size of the spinel grain, to reduce the amount of metal-25 inclusions), to reduce the consumption of liquid iron by 50-150 kg / t and the cost of steel.

Claims (1)

 Invention Formula thirty The method of converter redistribution of vanadium cast iron by the duplex process, including the filling of solid metal, scale, pouring iron, blowing oxidant) 1M gas to produce in the first stage vanadium slag and carbon semi-finished product, and the second - steel, which differs from improving the quality of the slag produced, reducing the consumption of pig iron and the cost of steel; in the first stage of the process, scrap is poured into the converter in the amount of 5-12% before the iron is cast. 45 of the mass of liquid iron at a ratio of lightweight and total scrap of 0.6-0.8: 1 and heated to 400-700 ° C. 35 they are planted on high-temperature vanadium slag left in the converter from previous melting and heated for 5-10 minutes with a fuel-oxygen torch with a total oxygen supply rate and a natural gas consumption of 0.7 to 400-700 C. 20 tons are poured onto the heated scrap vanadium cast iron. Scale in the amount of 0.7–1.0 t (4–5% of the weight of the pig iron), the bulk particles are scattered on the scrap metal before blowing out, and finish at the first minutes of purging. The temperature of the intermediate product after purging 1360-1400 C. The results are summarized in table 1 and 2. Comparison of limestone and the proposed shows that the proposed method allows to improve the quality of the slag produced (to increase the average size of the spinel grain, to reduce the number of metal inclusions), to reduce the consumption of liquid iron by 50-150 kg / t and the cost of steel. Invention Formula The method of converter redistribution of vanadium cast iron by the duplex process, including the filling of solid metal, scale, pouring iron, blowing oxidant) 1M gas to produce in the first stage vanadium slag and carbon semi-finished product, and the second - steel, which differs from improving the quality of the resulting slag, reducing the consumption of iron and the cost of steel, in the first stage of the process, in the converter, steel scrap in the amount of 5-12% is poured into the converter before pouring the iron. from the mass of liquid iron at a ratio of lightweight and total scrap of 0.6-0.8: 1 and heated to 400-700 ° C. ita 1 . Cost price steel, ruv / t 80 80 J .O 2.0 7 1.4 -1- 0.6 The averaged value of the phenomenon was measured by the “software transmission: C to the blower at the stage deva adac. 20. 17.6 11.4 1053 66-37 18, t 12.6 8,8 10.6 12, 13.2 1142 B70 864 866 861 910 1019 998 930 879 854 938 865 868 882 .889 69-72 54-10 53-75 33-61 53-25. .62-10 fe4-47 63-52 57-95 54-20 52-12 5t-42 53-87 53-99 54-72 55-08 carbon carbon and polzgprodukge ev 50 R 100% war taking into account the loss of slag with discharge semi-product. T BLKP 2