RU2532793C1 - Mixture for steel processing in ladle - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to ferrous metallurgy, and namely to deoxidising refining mixtures at out-of-furnace treatment of metal in a furnace-ladle unit. Flux consisting of the following components (wt %) and containing CaF₂ is used as material: 23-43 MgO, 25-45 Al₂O₃, 10-20 SiO₂, 5-10 CaO and 2-7 CaF₂. The mixture contains the following components, wt %: deoxidising agent 10-35, flux 5-20, and lime is the rest.

EFFECT: invention allows obtaining steel with sulphur content of not more than 0,005%, increases ladle lining resistance by 10-15% with minimum environmental load.

2 cl, 5 tbl, 1 ex

Description

The invention relates to ferrous metallurgy, in particular to deoxidative refining mixtures used in out-of-furnace metal processing on a ladle furnace unit.

The closest in technical essence and the achieved result is a mixture for processing steel in a ladle, disclosed in the description of the technology of out-of-furnace metal processing on a ladle furnace in the production of low-silicon steel, including a deoxidizer, a material containing CaF ₂ in the form of fluorspar, lump and powdered fluidized lime (RU No. 2465340).

A disadvantage of the known mixture is the high material costs for the formation of the mixture using large quantities (more than 500 kg per heat) of fluorspar, difficulties in creating conditions for the removal of sulfur during the introduction of the processing mixture, increased deoxidant fumes and wear of the lining.

An object of the invention is to increase the efficiency of the mixture in the process of bucket processing

The technical result is the creation of conditions in the bucket to achieve deep desulfurization of steel with minimal use of CaF ₂ , increase the durability of the lining of ladles and improve the ecological environment.

The technical result is achieved by the fact that the known mixture for processing steel in a ladle, including a deoxidizing agent, a material containing CaF ₂ and lime, as proposed, as a material containing CaF ₂ , it contains a flux of the following composition: 23-43% MgO, 25- 45 Al ₂ O ₃ , 10-20% SiO ₂ , 5-10% CaO and 2-7% CaF ₂ , with the ratio of components in the mixture, mass. %:

Deoxidizer 10-35; Flux 5-20; Lime rest

The mixture as a deoxidizer may contain AI and / or FeAI. The proposed deoxidizing mixture as a result of incorporating a flux with certain ratios of components allows one to obtain in the ladle the refining slag of the MgO - Al ₂ O ₃ - SiO ₂ - CaO - CaF _{2 system} ; saturated in content (MgO), forming a significant amount of low-melting phases and having a reduced viscosity.

The optimal content of components in the flux used is: 23-43% MgO, 25-45% Al ₂ O ₃ , 10-20% SiO ₂ , 5-10% CaO and 2-7% CaF ₂ , which with the declared amount of flux and lime the mixture provides refining of metal from harmful impurities and reducing wear of the periclase-carbon lining of the bucket.

When the MgO content in the flux is less than 23%, the refining slag formed in the ladle due to its high aggressiveness to pereklazouglerodnoy lining does not provide high durability of the ladles. When the MgO content is in the range of 23-43%, the refining slag formed in the ladle provides deep metal desulfurization and high durability of the periclase-carbon lining of the ladles. A further increase in the concentration of MgO in the flux leads to the fact that the slag formed in the ladle is shifted to the heterogeneous region. Such slag does not provide deep metal desulfurization and high durability of the lining of ladles.

For the effective use of the mixture when processing metal in a ladle, the composition of the mixture components, within the framework of the proposed composition, is selected taking into account the receipt in the ladle furnace of refining slag with the basicity (CaO) / (SiO ₂ ) = 2.5 ÷ 6.0 and the ratio (CaO) / (Al ₂ O ₃ ) = 1.0 ÷ 6.0. The composition of the mixture, providing the refining slag with a ratio of components in it outside the above ratios, does not allow to obtain the optimal refining properties of the slag.

Magnesia flux, which is part of the mixture, is used in the form of a briquette.

The optimal chemical composition of the flux in the briquettes: 23-43% MgO, 25-45% Al ₂ O ₃ , 10-20% SiO ₂ , 5-10% CaO and 2-7% CaF ₂ .

The claimed mixture for processing steel in a ladle was tested on 450 melts in the smelting of pipe grades of steel. Smelting was carried out in 135 tons of arc steelmaking furnaces. Metal was produced in a slagged ladle. The amount of skull slag in the bucket is 9.5-13 kg / t. The formation of the slag mixture was carried out in a ladle at the outlet from the furnace with magnesia flux additives at various ratios of the declared composition, lime and aluminum additives and subsequent lime and aluminum additives at the ladle furnace installation.

Example

Magnesia flux containing, mass. %: MgO 43; Al ₂ O ₃ 20; SiO ₂ 20; CaO 10; CaF ₂ 7, weighing 200 kg, granular aluminum 220 kg and lime 650 kg were loaded into a ladle at the outlet. Additionally, 1000 kg of lime and 50 kg of aluminum wire were added after melting to the ladle-furnace unit. The amount of skull slag in the ladle was 13 kg / t of metal.

The total consumption of the components of the mixture amounted to:

Deoxidant (total consumption Al) 270 kg (12.7%) Flux 210 kg (9.5%) Lime 1650 kg (77.8%)

that in terms of a ton of metal at a flow rate of the mixture of 15.7 kg / t amounted to Flux 0.785 kg / t; Lime 13.345 kg / t; Almet 1.57 kg / t. The processing time at the ladle-furnace installation is 55 minutes. The sulfur content in the metal after completion of the processing of steel in the ladle with the mixture was 0.004%.

Examples of tests of various flux compositions in the mixture and the costs of the components forming the mixture, and the effect of the resulting mixture on the sulfur content in the pipe steel after processing is given in tables 1-5. As a result of the processing, the sulfur content was 0.002-0.005%.

The above examples within the framework of the proposal do not exhaust all possible options for the formation of the mixture and allow other options for creating the mixture in the ladle by varying, for example, the additive time.

The use of the inventive mixture formed in a ladle using aluminum and / or ferroaluminium as a deoxidizer in an amount of 10-35%, magnesian flux in an amount of 5-20% and lime - the rest, it is possible to obtain steel with a sulfur content of not more than 0.005%, to achieve increasing the durability of the lining of ladles by 10-15% with a minimum environmental load on the environment.

Table 1 No. The composition of the flux,% Mixture consumption, kg / t * CaO CaO Sulfur in the metal MgO Al ₂ O ₃ SiO ₂ CaO CaF ₂ Flux Lime Almet SiO ₂ Al ₂ O ₃ one 43 twenty twenty 10 7 0.44 7.48 0.88 3.93 6.04 0.005 2 40 25 twenty 9 6 0.88 7.04 0.88 3.72 5.53 0.005 3 33 38 16 8 5 1.32 5.72 1.76 3.33 2.7 0.003 four thirty 45 fourteen 7 four 1,496 4,664 2.64 3.05 1.72 0.002 5 26 44 twenty 6 four 1.76 3.96 3.08 2.75 1.4 0.003 6 23 45 fifteen 10 7 1.76 3.96 3.08 2.8 4 1.4 0.004 * - with a total consumption of the mixture of 8 kg / t, and the skull bucket slag 13 kg / t

table 2 No. The composition of the flux,% Mixture consumption, kg / t * CaO CaO Sulfur in the metal MgO A1 ₂ O ₃ SiO ₂ CaO CaF ₂ Flux Lime Almet SiO ₂ Al ₂ O ₃ one 43 twenty twenty 10 7 0.785 13,345 1,57 5.46 5.22 0.004 2 40 25 twenty 9 6 1,57 12.56 1,57 5.03 4.72 0.003 3 33 38 16 8 5 2,355 10,205 3.14 4.35 2.16 0.003 four thirty 45 fourteen 7 four 2,669 8,321 4.71 3.87 1.32 0.002 5 26 44 twenty 6 four 3.14 7,065 5,495 3.32 1,04 0.003 6 23 45 fifteen 10 7 3.14 7,065 5,495 3.49 1.05 0.002 * - at a total flow rate of the mixture of 15.7 kg / t, and a skull bucket slag of 13 kg / t

Table 3 No. The composition of the flux,% Mixture consumption, kg / t * CaO CaO Sulfur in
metal MgO Al ₂ O ₃ SiO ₂ CaO CaF ₂ Flux Lime Almet Al ₂ O ₃ SiO ₂ one 43 twenty twenty 10 7 0.85 14.45 1.7 5.74 5.13 0.004

2 40 25 twenty 9 6 1.7 13.6 1.7 5.27 4.63 0.003 3 33 38 16 8 5 2,55 11.05 3.4 4,54 2.1 0.002 four thirty 45 fourteen 7 four 2.89 9.01 5.1 4.02 1.28 0.004 5 26 44 twenty 6 four 3.4 7.65 5.95 3.42 1.01 0.003 6 23 45 fifteen 10 7 3.4 7.65 5.95 3.61 1,02 0.003 * - at a total flow rate of the mixture of 17 kg / t, and the skull bucket slag 13 kg / t

Table 4 No. The composition of the flux,% Mixture consumption, kg / t * CaO CaO Sulfur in the metal MgO Al ₂ O ₃ SiO ₂ CaO CaF ₂ Flux Lime Almet SiO ₂ Al ₂ O ₃ one 43 twenty twenty 10 7 0.785 13,345 1,57 5.9 5.08 0.003 2 40 25 twenty 9 6 1,57 12.56 1,57 5,4 4,59 0.002 3 33 38 16 8 5 2,355 10,205 3.14 4.64 2.07 0.002 four thirty 45 fourteen 7 four 2,669 8,321 4.71 4.1 1.26 0.002 5 26 44 twenty 6 four 3.14 7,065 5,495 3.47 0.99 0.005 6 23 45 fifteen 10 7 3.14 7,065 5,495 3.67 one 0.005 * - at a total flow rate of the mixture of 15.7 kg / t, and the skull bucket slag 11.5 kg / t

Table 5 No. The composition of the flux,% Mixture consumption, kg / t * CaO CaO Sulfur in the metal MgO Al ₂ O ₃ SiO ₂ CaO CaF ₂ Flux Lime Almet SiO ₂ Al ₂ O ₃ one 43 twenty twenty 10 7 0.785 13,345 1,57 6.7 4.9 0.004 2 40 25 twenty 9 6 1,57 12.56 1,57 6.06 4.41 0.003 3 33 38 16 8 5 2,355 10,205 3.14 5.14 1.96 0.002 four thirty 45 fourteen 7 four 2,669 8,321 4.71 4,51 1.18 0.003 5 26 44 twenty 6 four 3.14 7,065 5,495 3.74 0.92 0.005 6 23 45 fifteen 10 7 3.14 7,065 5,495 3.99 0.93 0.005 * - with a total consumption of the mixture of 5.7 kg / t, and a skull bucket slag of 9.5 kg / t

Claims (2)

1. A mixture for processing steel in a ladle containing a deoxidizer containing CaF ₂ material and lime, characterized in that the flux of the following composition is used as the CaF ₂ -containing material, wt.%: 23-43 MgO, 25-45 Al ₂ O ₃ , 10-20 SiO ₂ , 5-10 CaO and 2-7 CaF ₂ , when the ratio of components in the mixture, wt. %:
Deoxidizer 10-35 Flux 5-20 Lime rest 2. The mixture according to claim 1, characterized in that Al and / or FeAl is used as a deoxidizing agent.