SU1406179A1 - Powder-like mixture for dephophorizing steel - Google Patents

Abstract

The invention relates to the field of ferrous metallurgy, and more specifically to the production of steel in electric arc furnaces, and can be used to intensify the process of dephosphorization during the oxidation period of smelting. The aim of the invention is to improve the ability of the mixture to be phosphorus-rich. Powder-like mixture for dephosphorization of steel. Contains, wt.%: Limestone to 10-15; iron oxides 55-65; nepheline concentrate 3-7; the main recycling fault is the rest. The use of the mixture allows a 1.5-fold increase in the degree of dephosphorization of steel. 1 tab.

Description

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The invention relates to ferrous metallurgy, and more specifically to the production of steel in electric arc furnaces, and can be used to intensify the process of dephosphorization during the oxidation period of smelting.

The aim of the invention is to increase the dephosphorization capacity of the mixture.

The proposed powder mixture of AJM steel dephosphorization contains limestone, nepheline concentrate, iron oxides and recirculated basic slag in the following ratio of components, wt.%: Limestone to 10-15j iron oxides 55-65; nepheline concentrate 3–7, recirculated basic putty — the rest, while the total content of nepheline concentrate and recirculated slag must be at least 25%.

Introducing lime into the mixture (10-15%) instead of lime contributes to the creation of lower temperatures in the purge zone, as a result of which the thermodynamic conditions of dephosphorization are improved when the powdered slag mixture is injected into the metal melt.

In addition, carbon dioxide released during decomposition of carbon dioxide increases the mass transfer of the reactants and the products of the dephosphorization reaction, which favorably affects the kinetics of the process.

The content of limestone in the mixture above 15% reduces the oxidation potential of the mixture, and below 10% does not create a sufficiently effective bubbling of the slag phase, which adversely affects the course of the process of dephosphorization.

The introduction of recirculated basic slag into the mixture increases the basicity of the slag and contributes to a more rapid slagging.

A decrease in the content of the recycled slag below 18% worsens the course of the dephosphorization process due to the low activity (CaO) in the slag. An increase in the content of recycled slag above 32% leads to a decrease in the oxidizing potential of the mixture, which reduces the dephosphorization capacity of the mixture.

The high content of iron oxides (55-65%) increases the dephosphorization capacity of the mixture, since the higher the concentration of FeO in the slag, the less

the content of residual phosphorus in the metal.

A decrease in the content of iron oxides below 55% and an increase in their content above 65% significantly affects the process of removing phosphorus from a metal melt, in the first case by reducing the oxidative potential of the mixture, and in the second case, the degree of CaO in the slag decreases.

When the content of nepheline concentrate in the mixture is below 3%, the kinetic conditions of the dephosphorization deteriorate due to the formation of a thick, heterogeneous Slag, and when the content of nepheline concentrate is above 7%, the basicity and / or oxidized slag mixture decreases.

When the total content of nepheline concentrate and recirculating slag is less than 25%, the slags are thick, heterogeneous, which has an inhibiting effect on the process of removing phosphorus from the metal melt.

To confirm the optimality of the composition of the proposed powder mixture for dephosphorization in a 5-ton electric arc furnace, a series of melts of 35XM steel was carried out using the proposed mixture (1-8), with mixtures having a composition whose content of components goes beyond the boundary values of the proposed composition (9 -16), and the famous mixture (17-19).

As a material containing iron oxides, blacksmith scale was used, containing 98.1% of FejO.

The chemical composition of the recirculated basic slag - the slag of the recovery period during steelmaking in an electric arc furnace, is as follows:% CaO 56.1; SiO 16.5; FeO 1, 1; MpO 0.5; MgO 14.3; 4.5; , 3 and other elements 1.7.

The powdery dephosphorizing mixture with a fraction of not more than 2 mm was blown into the stream of oxygen using a pneumatic blower into a metal melt with a temperature of 1560-1570 ° C in an amount of 1.8% of the mass of the charge with an intensity of 4.8-5.2 kg / t min The melt before purging had the following chemical composition, wt.%: Carbon 0.33-0.42; silicon 0,17-0,24;

manganese 0.4-0.7; chromium 0.8-1.1; phosphorus 0,027-0,04.

Metal samples for phosphorus content in steel were taken immediately before the injection of powder mixtures and three minutes after the end of the purge.

The test results are given in

Calcium, characterized in that, in order to increase the dephosphorus capacity of the mixture, it contains lime as calcium compounds and additionally contains recirculated basic slag in the following ratio of components,%

Table continuation

Claims (1)

Claim A powder mixture for steel dephosphorization containing iron oxides, nepheline concentrate and - - - - At- The composition of the mixture, weight L measures Fe oxides Of- West nanny Nepheline concentrate Recycled Main Slag 1 55 12 5 28 2 65 10 5 20 3 60 10 5 25 4 60 fifteen 5 20 5 60 12 3 25 6 60 thirteen 7 20 7 63 12 7 18 8 65 10 3 32 9 54 12 5 29th 10 56 Ίο 5 19 eleven 60 9 5 26 12 60 16 5 19 thirteen 60 ' 12 2 26 14 60 12 8 20 fifteen 64 12 7 17 NII calcium, characterized in that, in order to increase the dephosphorizing ability of the mixture, as by rierou ve connections calcium she contains limestone and further comprises recirculating main slag at the following relation components May.%: Yu Limestone Iron oxides 10-15 55-65 Nepheline concentrate Recirculation 15 main slag 3-7 Rest at this total nepheli- new concentrate and recirculation th slag should be not less than 25%. Summar- new The phosphorus content, 10 ³ % Degree of dephospho- Of- holding- - walkie-talkie news no before after % felin CONC, and slag recycling, weight. % purge purge - 33 35 16 54.3 - 25 27 thirteen 51.6 - thirty 32 fifteen 53.1 - 25 40 17 67.5 - 28 28 eleven 60.7 27 34 fifteen 55.9 - 25 34 14 58.8 - 35 thirty 12 60.0 - 34 35 22 37.1 - 24 38 23 39.5 - 31 • 32 20 37.5 - 24 28 17 39.3 - 28 35 20 42.9 - 28 32 18 43.8 "G 24 32 19 40.6 Table continuation At- • The composition of the mixture, weight.X Summar- Content Power Mer R-- r — r 1---- ——- new phosphorus , 10’X dephospho- Oxide IE Nefeli- Recycle Of- holding- - --—— walkie-talkie ly Fe West new Cooler news no before after X nyak - concentration onny felin about about spending the main END, and blows DU, wki Noah recycled slag lecture slag weight.? .............. L— 1. —W 16 62 14 4 20 - 24 thirty 17 43.3 17 31 4 - 65 - 38 21 44.7 18 40 - 5 - 55 - ³⁵ 19 45.7 19 fifty 9 - 41 - 29th 16 44.8