WO2007055609A1 - Mixture for refining and modifying steel or cast-iron - Google Patents

Abstract

The invention relates to metallurgy, in particular to out-of-furnace processing of steel and cast-iron. Said invention enables to develop a reaction mixture which makes it possible to extract alkaline-earth or earth rare metals with a high recovery degree during the recovery thereof from carbonates and oxides, mainly by means of aluminium, subsequently, to form stable silicon compounds and to obtain a liquid-movable synthetic slag from calcium aluminate. The inventive mixture for refining and modifying steel and cast-iron comprises a polymetal ore containing carbonates and/or oxides of alkaline-earth metals, oxides of earth rare metals, aluminium, silicon or the alloys thereof consisting of iron whose content is equal to or less than 25 % and a datolite ore in the quantity of 30-80, 0.001-15, 5-30, 5-25 and 1-5 mass %. Said mixture cal also contain 0-15 mass % at least one type of oxide from a TiO2, Nb2O5, V2O5, MoO3 and NiO group. Said mixture makes it possible to exclude the roast processing of a main component, to produce and dry brings, when the mixture is introduced in an iron-carbon melt, to produce a liquid-movable and a highly-basic slag and to simultaneously carry out refining, modifying and micro alloying of steel and cast-iron.

Description

 MIXTURE FOR REFINING AND MODIFICATION OF STEEL AND

CAST IRON

The invention relates to the field of metallurgy, in particular to the creation of a refining and modifying mixture for the treatment of steel and cast iron. The developed mixture can be used at metallurgical and machine-building enterprises for out-of-furnace treatment of steel and cast iron in order to improve their quality.

Known refining and modifying mixture containing 50-70% of the oxides and / or carbonates of barium, calcium, magnesium, 1-10% of rare earth oxides, 2-5% of borate ore, 5-20% of aluminum and 20-35% of silicon [1 ]. When this mixture is introduced into a metal iron-carbon melt due to reactions, the simultaneous formation of a modifying alloy containing active elements and refining slag is achieved.

The disadvantage of the mixture is the toxicity and high cost of barium oxides and carbonates obtained from natural sulfate ores through complex chemical processing. In addition, the introduction of the mixture into liquid steel is accompanied by a significant pyroelectric effect due to the formation of vaporous magnesium, the vapor pressure of which at a temperature of 1600 ^° C exceeds 2 MPa (20 atm).

Closest to the invention in terms of technical nature and the achieved effect is a briquette for deoxidation and modification of steel and cast iron [2], containing the product of firing of Witheritstrontianite concentrate, aluminum, ferrosilicon FC65, fluorspar and a binder with the following content of components, May. %:

The firing product of Witeritstrontianite concentrate 53-55

Aluminum Powder 7-12 Ferrosilicon powder FC65 29-32

Fluff stitch 2-3

Binder 2-4

The disadvantage of the briquette is the low efficiency of using barium and strontium, recovered from Witeritstrontianite concentrate, due to the presence of ferrosilicon FC65 containing up to 35% iron. Such a high iron content increases the loss of these metals by evaporation due to their extremely low solubility in the resulting ferroalloy. The low efficiency of the mixture is also due to the absence of a calcium-containing component in it, since the greatest effectiveness of barium and strontium in the treatment of liquid steel is manifested only in the presence of calcium, a solvent of barium and strontium, in the modifier.

The aim of the invention is to increase the refining and modifying ability of the mixture.

This goal is achieved by the fact that in the mixture for the deoxidation and modification of steel and cast iron containing aluminum, barium-strontium-containing and silicon-containing material according to the invention, rare-earth metal oxides and datolithic ore are additionally introduced in the form of oxides and carbonates, and barium-strontium-containing and silicon-containing materials are used respectively polymetallic ore containing alkaline earth metals in the form of carbonates and / or oxides, and silicon, or its alloys, containing less than 25% iron, in the following ratio, May. %:

Polymetallic ore 30-80

Aluminum 5-30

Silicon, or its alloys, containing less than 25% iron 5-25

Rare earth oxides 0.001-15

Datolite ore 1-5 Polymetallic ore in the form of carbonates and / or oxides contains barium, strontium, calcium, magnesium, silicon, potassium, sodium, iron, manganese, aluminum and titanium in the following components, May. %: 10-18 Ba, 2-7 Sr, 10-20 Ca, 0.4-0.7 Mg, 10-16 Si, 2-3 K, 0.7-1.5 Na, 1.5-7 , 0 Fe, 0.1-0.3 Mn, 1-4 Al and 0.4-0.8 Ti.

Datolite ore in the form of oxides and / or carbonates contains boron, aluminum, magnesium, calcium, silicon, iron, manganese, potassium and sodium in the following ratio, May. %: 2-4 V, 0.3-1.0 Al, 0.2-0.4 Mg, 20-30 Ca, 15-25 Si, 2-5 Fe, 0.2-2.5 Mn, 0 04-0.06 (K + Na).

In addition, the mixture for deoxidation and modification of steel and cast iron may contain May 5-15. % of at least one oxide from the group TiO ₂ , Nb ₂ O ₅ , V ₂ O ₅ , MoO ₃ , NiO.

The technical effect when using the invention lies in the fact that the developed composition of the mixture provides a high degree of extraction of alkaline earth and rare earth metals when they are reduced from carbonates and oxides mainly by aluminum, the subsequent formation of stable compounds with silicon, the formation of liquid synthetic slag from calcium aluminates. With the additional introduction of at least one of the oxides TiO ₂ , Nb ₂ O ₅ , V ₂ O ₅ , MoO ₃ , and NiO into the mixture, it allows refining, modifying, and microalloying steel and cast iron at the same time.

Alkaline earth metals calcium, barium and strontium contribute to the most favorable type of non-metallic inclusions in steel - oxides in the sulfide shell. When alkaline-earth and rare-earth metals are introduced together in liquid steel, due to the low boiling point and low solubility of calcium, barium, and strontium in liquid iron, these metals are consumed to a greater extent than rare-earth metals, the boiling point of which exceeds 3000 "C. These metals dissolve well in iron and are stored for subsequent interaction with harmful impurities, including nitrogen, hydrogen and non-ferrous metals, convert them to passive forms and clean grain boundaries upon cooling and crystallization of the metal.

A decrease in the amount of polymetallic ore in the mixture below the lower limit (30%) will lead to a decrease in its refining and modifying ability. An increase in its content of more than 80% will not lead to an increase in the modifying effect of alkaline earth metals on the melt due to their extremely limited solubility in liquid iron. In addition, in this case, refractory slag with a low refining capacity is formed.

An increase in the amount of aluminum in the mixture of more than 30% will lead to an excessively high content of aluminum oxide in the slag formed from the mixture, an increase in the melting temperature of the slag and a decrease in its refining ability. A decrease in the amount of aluminum in the mixture of less than 5% will lead to insufficient reduction of the alkaline earth and rare earth metals from the mixture and, as a result, a decrease in the modifying effect.

If the mixture exceeds the upper limit (more than 25%) of the amount of silicon, the refining ability of the slag formed from the mixture decreases due to the excessively high content of silicon dioxide in it. A decrease in the amount of silicon in the mixture of less than 5% will reduce its modifying ability due to unsatisfactory reduction of active elements.

The lower limit of the content of rare-earth metal oxides in the mixture (0.001%) is due to the fact that in some cases the necessary modifying effect is achieved practically without the participation of rare-earth metals. In addition, rare earth metal oxides are scarce and costly. Rare earth oxides increase more than 15% of metals is impractical due to the possibility of the formation of a steel macrostructure defect - cerium inhomogeneity.

In the case of exceeding in the mixture the upper limit (5%) of the amount of datolyte ore, undesirable excessive microalloying with boron is possible, since the pronounced concentration peak (0.003-0.005%) has the maximum effect from microalloying with boron. A decrease in the amount of datolithic ore in the mixture of less than 1% will not provide liquid slag with a high refining ability.

Additional introduction into the mixture of at least one oxide from the group TiO ₂ , Nb ₂ O ₅ , V ₂ O ₅ , MoO ₃ , NiO in an amount of 5% in the presence of aluminum and reduced chemically active elements will lead to the complete reduction of metals from oxides of this group and microalloying they are steel and cast iron. If the content of one or more oxides in the mixture is less than 5%, the content of microalloying elements in the steel will be insufficient. An increase in the amount of these oxides in the mixture of more than 15% is impractical due to the fact that a further improvement in the properties of the metal being processed is not noticeable.

Example 1. Modeling of processes occurring with a mixture when it is heated to operating temperature and exposure.

After mixing, the components of the mixture with a particle size of less than 2 mm are loaded into a graphite crucible, which is heated with a charge in a Tamman furnace at a temperature of 1450 ^° C for 5 minutes. Melting products are weighed and subjected to chemical analysis. The results of the experiments are shown in the table.

As can be seen from the above data, the proposed mixture allows to increase the yield of the alloy, the extraction of barium and strontium into it by 3-6%, additionally extract calcium, rare earth metals and titanium.

The use of the proposed mixture in comparison with the known allows: • to exclude the burning of the ore component, briquetting the mixture and drying the briquettes; • obtain an alloy containing highly active alkaline-earth metals, including calcium, rare-earth and alloying metals, as well as liquid-moving synthetic slag based on calcium aluminates;

• to carry out effective and safe processing of iron-carbon melt, to simultaneously refine, modify and microalloy steel and cast iron;

• Replace expensive and scarce ferroalloys with initial charge materials.

Information sources:

1. RF patent 2192479, IPC C21 C 1/00, 1/06. Bull. JVb 31, 2002.

2. Patent RF2023044, November 15, 2001. Bull. JV21.

Table

Replacement sheet

Claims

FORMULA 1. A mixture for refining and modifying steel and cast iron, containing aluminum, barium-strontium-containing and silicon-containing material, characterized in that it additionally contains rare-earth metal oxides and datolithic ore in the form of oxides and carbonates, and polymetallic materials are used as barium-strontium-containing and silicon-containing materials containing alkaline earth metals in the form of carbonates and / or oxides, and silicon or its alloys containing less than 25% iron, in the following ratio onents, May. %: Polymetallic ore 30-80 Aluminum 5-30 Silicon or its alloys containing less than 25% iron 5-25 Rare earth oxides 0.001-15 Datolite ore 1-5 2. The mixture according to claim 1, characterized in that the polymetallic ore in the form of carbonates and / or oxides contains barium, strontium, calcium, magnesium, silicon, potassium, sodium, iron, manganese, aluminum and titanium at the following content of components, May. %: 10-18 Ba, 2-7 Sr, 10-20 Ca, 0.4-0.7 Mg, 10-16 Si, 2-3 K, 0.7-1.5 Na, 1.5-7 , 0 Fe, 0.1-0.3 Mn, 1-4 Al and 0.4-0.8 Ti. 3. The mixture according to claim 1, characterized in that the datolite ore in the form of oxides and / or carbonates contains boron, aluminum, magnesium, calcium, silicon, iron, manganese, potassium and sodium in the following ratio of components, May. %: 2-4 V, 0.3-1.0 Al, 0.2-0.4 Mg, 20-30 Ca, 15-25 Si, 2-5 Fe, 0.2-2.5 Mn, 0 04-0.06 (K + Na). 4. The mixture according to claim 1, characterized in that it contains May 5-15. % of at least one oxide from the group TiO ₂ , Nb ₂ O ₅ , V ₂ O ₅ , MoO ₃ , NiO.