RU2456349C1 - Procedure for out-of-furnace treatment of iron-carbon melt - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: cored wire is introduced into the melt in two stages, during the first of which the wire is introduced with a modifying composition and during the second one the wire is introduced with a refining composition, also the wire with the modifying composition contains iron and calcium in the form of a silicon alloy and/or in the metallic phase with the following ratio of the components, wt %: the total content of calcium and silicocalcium is 30-95, iron is the rest, and the wire with a refining composition contains lime, carbonate salts of alkaline-earth metals (AEM) and/or alkaline metals (AM), haloid salts of alkaline-earth metals (AEM) and/or alkaline metals (AM) with the following ratio of components, wt %: lime is 1-50, carbonate salts of alkaline-earth metals and/or alkaline metals are 1-25, halide salts of alkaline-earth metals and/or alkaline metals are the rest, when the wire with the modifying composition is introduced with calcium consumption of 0.1-0.3 kg per ton of melt, and the wire with the refining composition is introduced at a consumption rate of 0.5-5 kg per ton of melt.

EFFECT: invention enables to improve strength, ductility and impact hardness of the finished metal by reducing the amount of oxide and sulfide inclusions.

5 cl, 1 ex, 2 tbl

Description

The invention relates to ferrous metallurgy and can be used in steelmaking for deoxidation, modification and refining of various steels, alloys and cast irons used in transport engineering, metallurgy, energy, construction industry, in the manufacture of products in the "northern version", etc.

A known method of processing steel with a modifying mixture containing, wt.%: 10-30 silicomishmetal, 10-29 silicocalcium, 10-30 silicobarium, 1-5 magnesium, 15-30 lime, 5-10 corundum, 5-10 fluorspar (cm USSR AS No. 740837, C21C 1/00, declared December 16, 1977, publ. 06/15/1980 “Modifying mixture”). According to the specified method, steel refinement and modification is carried out by the slag of the CaO-Al ₂ O ₃ -CaF _{2 system} and alloys with active elements.

The disadvantage of this method is the low efficiency of this mixture, introduced by a flux-cored wire, due to the low absorption by the melt of active low-melting modifying elements due to their early melting and evaporation to form protective liquid-moving slag from refractory components of the mixture.

Known modifier for steel based on aluminum, containing, wt%: magnesium 10-15, calcium 12-15, barium 8-10, aluminum - the rest, which is made in the form of dense granules of a fraction of 1-1.5 mm (RF patent No. 2228384 , according to class C22C 35/00, declared December 24, 2002, published May 10, 2004 “Modifier for steel”). The disadvantages of using such an alloy include the low modifying effect of Ca, Mg, and Ba on nonmetallic inclusions when they are introduced into the melt simultaneously with aluminum, since most of them are spent on steel deoxidation. In addition, the introduction of a modifier in the form of granules without the use of a protective shell leads to a partial loss of their effectiveness due to the interaction of alkaline earth elements with slag.

There is also known a method of processing an iron-carbon melt, comprising introducing into it a refining and modifying mixture consisting of materials containing barium, calcium, magnesium, rare earth metals, silicon, as well as borate ore and aluminum. As materials containing barium, calcium, magnesium and rare earth metals, oxides and / or carbonates of barium, calcium, magnesium and rare earth oxides are used. The mixture is introduced at a melt temperature of at least 1300 ° C in an amount of 0.5-5 kg / t with the following components, wt.%: Oxides and / or carbonates of barium, calcium, magnesium 50-70, rare earth oxides 1-10, borate ore 2-5, aluminum 5-20, silicon 20-35. The specified mixture is introduced continuously to the bottom of the tank filled with iron-carbon melt (see RF patent No. 2192479, class C21C 1/00, C21C 7/06, decl. July 16, 2001, publ. 10.11.2002 "Method for refining and modifying iron-carbon melt ").

The disadvantage of this method is its low efficiency of modification and refining, which is due to both the use of active elements in the mixture only in the form of oxides and carbonates, and the simultaneous introduction of both modifying and refining components of the mixture into the melt. The result is a decrease in the strength, plastic and viscous properties of metal, manufactured in accordance with the prototype. In addition, the introduction of such a mixture into the melt under industrial conditions is impossible without the use of cored wire.

The closest in technical essence, the achieved result and selected as a prototype is a method for out-of-furnace treatment of iron-carbon melt by introducing a flux-cored wire with a filler containing calcium and silicon into the melt, the calcium content being 36-56 wt.%, The ratio between calcium and silicon is within (0.6-1.3): 1, and the ratio between the calcium content in the filler and the content of the filler in the wire is 0.7: 1.2 (see paragraphs of the Russian Federation No. 2234541, class C21C 7 / 00, declared May 23, 2003, publ. 08/20/2004 "A wire for out-of-furnace processing of metallurgical melts").

The introduction of materials into the melt in the form of flux-cored wire ensures their more efficient use, since it prevents premature interaction with slag and metal. However, the composition of the filler cored wire, made in accordance with the prototype, does not satisfactorily refine the melt and provide high metal strength, ductility and toughness in metal products. In addition, the disadvantage of calcium as a modifier is its low survivability in the melt. Being in the form of a CaSi ₂ phase or calcium metal, it has low boiling points (1487 ° С) and melting points (980 ° С), high vapor pressure at temperatures of out-of-furnace treatment of steel melts. As a result, calcium in the composition of such a filler is subject to considerable fumes and has a short temperature-time interval in the melt. In addition, the prototype does not provide refining of the melt after the modifying treatment.

The objective of the present invention is to increase the strength, ductility and toughness of the metal.

The technical result obtained during the implementation of the invention is to increase the efficiency of modification and refinement by reducing the amount of oxide and sulfide inclusions in the finished metal.

This problem is solved due to the fact that in the known method of out-of-furnace treatment of an iron-carbon melt by introducing a flux-cored wire according to the invention into the melt, the flux-cored wire is introduced in two steps, the first of which introduces a wire with a modifying composition, and the second a wire with a refining composition this wire with a modifying composition contains iron and calcium in the form of an alloy with silicon and / or in the metal phase in the following ratio of components, wt.%: the total content of calcium and silicone altsia 30-95, iron - the rest, and the wire with a refining composition contains lime, carbonate salts of alkaline earth and / or alkali metals, halide salts of alkaline earth and / or alkali metals in the following ratio of components, wt.%: lime 1-50, carbonate salts alkaline earth and / or alkali metals 1-25, halide salts of alkaline earth and / or alkali metals - the rest, and a wire with a modifying composition is introduced with a flow rate of calcium of 0.1-0.3 kg per ton of melt, and a wire with a refining composition is introduced at a rate 0.5-5 g of the composition per ton of melt.

The wire with the modifying composition may additionally contain silicobarium in the following ratio of components, wt.%: Total calcium and silicocalcium content 30-95, silicobarium 1-40, iron - the rest; or alloys and oxides of rare-earth metals in the following ratio of components, wt.%: total content of calcium and silicocalcium 30-95, total content of alloys and oxides RMZ 1-25, iron - the rest; or simultaneously silicobarium, as well as rare-earth metal alloys and oxides in the following ratio of components, wt.%: total calcium and silicocalcium content 30-95, silicobarium 1-40, total content of alloys and oxides RMZ 1-25, iron - the rest.

A wire with a refining composition may additionally contain carbides in the following ratio of components, wt.%: Lime 1-50, carbonate salts of alkaline earth and / or alkali metals 1-25, carbides 1-10, halide salts of alkaline earth and / or alkali metals - the rest.

Studies conducted on the sources of patent and scientific and technical information have shown that the claimed method is not known and should not be explicitly learned from the prior art, i.e. meets the criteria of novelty and inventive step.

The inventive method can be implemented at any enterprise specializing in this industry, because this requires well-known materials and standard equipment, and is widely used in the production of steel and cast iron products, i.e. is industrially applicable.

The introduction of the modifier in steel aims to improve the structural characteristics and increase the mechanical properties of the metal. As a result of the modification occurs:

a) additional deoxidation and desulfurization of steel;

b) reduction in the amount of oxides, oxysulfides, sulfides, as well as a change in the composition of the resulting non-metallic inclusions;

c) purification of grain boundaries and near-boundary sections of particles, eutectics and segregation, leading to embrittlement of the metal;

d) grinding of the dendritic structure, as well as the formation of a fine-grained structure in subsequent technological operations to obtain finished products.

After completion of the modification, the inclusions, phases, eutectics, etc., remaining in the metal should be removed from the melt as much as possible as a result of refining, since their presence in the metal reduces the quality of the finished product.

The effectiveness of each of the tasks depends on the composition of the modifying and refining materials used, as well as the technology of out-of-furnace melt processing. The introduction of modifying and refining materials into the melt in the form of a flux-cored wire ensures their more efficient use, since it prevents the premature interaction of these chemically active substances with slag and metal.

It was experimentally established that to obtain the most pure in gases, non-metallic inclusions, phases, etc. metal modification and refining operations must be performed sequentially and, in accordance with the differentiation of their tasks, using various materials introduced by flux-cored wire. Thus, materials containing alkaline earth metals (hereinafter referred to as RZM) and rare-earth metals (hereinafter REM), in particular calcium in the form of silicocalcium and metallic calcium, barium in the form of silicobarium, alloys or salts of REM should be used to modify the melt. The use of materials having different melting and boiling points reduces the elasticity of calcium vapor and extends the temperature-time interval of the interaction of the modifying material with the melt and, accordingly, increases the efficiency of the modification. Calcium in prolonged form is the leading element in this material, and the amount of input modifier is usually 0.1-0.3 kg (in terms of calcium) per ton of melt. With smaller amounts, the modification of inclusions is insufficient, with large quantities, the number of phases, inclusions, etc., which have not been removed from the metal, increases, and the cost of processing unreasonably increases. When the total content of metallic calcium and silicocalcium in the material is less than 30 and more than 95 wt.%, Due to the foregoing, under- or over-modification of the melt takes place.

With an increase in silicobarium content of more than 40 wt.%, The proportion of calcium introduced by the material decreases and the use of a larger amount of flux-cored wire is necessary, which is not economically feasible.

With an increase in the REM content in the modifier material by more than 25 wt.%, The formation of “cerium inhomogeneity” and the formation of a large number of high-temperature inclusions that impede the casting of metal on a continuous steel casting machine can occur.

For refining the melt, it is effective to use insoluble compounds having a specific gravity substantially lower than the melt density, capable of high chemical sorption of the oxide and sulfide phases, forming complex inclusions with them easily removable from the melt. It has been established that such compounds can be lime, carbonate and halide salts of alkaline earth metals, as well as carbides (calcium, etc.).

When they are introduced into the melt in the form of mixed filler flux-cored wires, the best refining efficiency is achieved when the ratio of these compounds to each other is close to eutectic, which ensures the formation of low-temperature flotation-refining liquid phases in the melt.

It was experimentally established that the amount of refining material introduced should be in the range of 0.5-5 kg / t of melt. An increase of more than 5 kg / t of melt is not economically feasible.

An example implementation of the method.

The method was used in the manufacture of rolled metal from steel 25, which had a composition before mass modification in the ladle, wt.%: 0.22-0.24 C, 0.52-0.55 Mn, 0.2-0.23 Si, 0.026-0.028 S, 0.013-0.014 P, 0.11-0.12 Cr, 0.08-0.09 Ni, 0.022-0.024 Al, Fe - the rest.

The material of the flux-cored wire fillers for modification and refining was obtained by mixing in various ratios of phases and alloys: silicocalcium (30 wt.% Ca), metallic calcium, silicobarium (22 wt.% Ba), ferrosilicon REM (30 wt.% REM), REM oxides ( 79 wt.% REM), lime, sodium carbonate (Na ₂ CO ₃ ), calcium carbonate (CaCO ₃ ), calcium carbide (CaC ₂ ), fluorspar (CaF ₂ ), silicon carbide (SiC), calcium chloride (CaCl ₂ ), sodium (NaCl) and magnesium (MgCl ₂ ). The compositions and costs of materials for processing the melt are shown in table 2.

The material of the prototype was composed of silicocalcium (30 wt.% Ca).

The prepared mixtures of various compositions and material according to the prototype were crushed to obtain a fraction of 0-2 mm and rolled into a steel shell 0.4 mm thick, obtaining a flux-cored wire with a diameter of 14 mm

During the experiments, the melt from the electric furnace was discharged into a 15 t ladle and after deoxidation with ferrosilicon and aluminum, it was successively treated with cored wire with modifying and then refining materials. Each bucket was treated with a wire with a different composition of fillers. The consumption (see table 2) of the modifying filler (in terms of calcium) was 0.01-0.3 kg / t of steel, the refining consumption of 0.1-5.0 kg / t of steel.

When processing the prototype, the melt from the electric furnace was produced in 15 tons of a ladle and after deoxidation with ferrosilicon and aluminum, it was treated with flux-cored wire with SK 30 with a flow rate of 0.1 kg / t of steel.

During processing in all cases, the melt was purged with argon.

Next, the metal was poured into 7-8 tons of ingots, which were rolled into bars with a diameter of 20 mm. The final heat treatment of rolled metal included normalization at 880 ° C.

Contamination with non-metallic inclusions, as well as mechanical properties were evaluated in the finished metal.

Table 1 presents the results of determining the content of oxides and sulfides, as well as the temporary resistance σ _B , elongation δ and impact strength (KCV) at -60 ° C - and _N in the metal processed according to the prototype and according to the options presented in the table one.

From the data in tables 1 and 2, it is seen that:

1) the processing of the melt according to the prototype (option 0) leads to high contamination of the metal with oxide and oxysulfide (1.5 points), as well as sulfide (1.2 points) inclusions, low temporary resistance (56 kgf / cm ² ), relative elongation (less than 28%) and low temperature impact strength (1.7 kgf * m / cm ² );

2) metal processing by the present method (options 3-14), i.e. in the sequential use of flux-cored wires with modifying (having compositions, wt.%: total content of metallic calcium and silicocalcium 30-95, silicobarium 1-40, the sum of alloys and oxides of rare-earth metals 1-25) and refining (having compositions, wt.%: lime 1-50, carbonate salts of ЩЗМ and ЩМ 1-25, carbides 0-10, halide salts of ЩЗМ and ЩМ - the rest) with materials with a flow rate of 0.10-0.30 kg / t, respectively, in terms of calcium and 0.5- 5 kg / t reduces pollution by oxide, oxysulfide (0.9-1.0 points) and sulfide (0.5-0.6 points) inclusions, as well as the increase in temporary resistance (more than 61 kgf / cm ² ), elongation (more than 32%) and impact strength (more than 2.2 kgf * m / cm ² );

3) the processing of the melt according to options different from the declared (options 1 and 2) does not lead to an increase in the purity of steel by non-metallic inclusions and the level of mechanical properties compared to the prototype.

Thus, from the data presented in tables 1 and 2, it follows that a decrease in the number of oxide, oxysulfide and sulfide inclusions in the finished metal and high values of temporary resistance, elongation and toughness occur only in the metal processed by the present method.

Table 1 Contamination and mechanical properties of metal that has undergone after-furnace treatment using various technologies Option No. (Table 1) Inclusion pollution, point Mechanical properties Oxides + Oxisulfides Sulfides σ _B , kgf / cm ² δ,% a _N , kgf * m / cm ² 0 (prototype) 1,5 1,2 57 28 1,6 one 1.45 1,1 57 29th 1,6 2 1.35 1,2 56 28 1,5 3 1.00 0.6 61 33 2,3 four 0.90 0.5 62 32 2,4 5 0.95 0.5 61 34 2,3 6 1.00 0.6 61 32 2,3 7 1.00 0.5 62 32 2,4 8 0.90 0.5 62 32 2,4 9 0.95 0.55 63 33 2,4 10 1.00 0.6 62 32 2,4 eleven 1.00 0.55 62 32 2.2 12 1.00 0.55 63 33 2,4 13 0.95 0.6 64 34 2,3 fourteen 0.9 0.55 63 33 2,3

table 2 Compositions and consumption of modifying and refining materials No. Modifying material * Refining material Composition, wt.% Consumption, kg Ca / t Composition, wt.% Consumption, kg / t SK30 FSB Calcium Met FeSiPЗM + REM oxides Cao Carbonate salts Carbides Halide salts CaCO ₃ Na ₂ CO ₃ CaS ₂ SiC CaCl ₂ NaCl MgCl ₂ one twenty - - - 0.01 fifteen 5 5 - - thirty 25 twenty 0.1 2 fifteen - fifteen - 0.05 one fifteen 10 - - 54 twenty - 0.3 3 fifteen - fifteen - 0.1 one fifteen 10 - - 74 - - 0.5 four fifty - twenty - 0.1 fifty - 10 - - 40 - - 5,0 5 fifty - twenty - 0.3 25 10 5 - - - thirty thirty 1,0 6 95 - - - 0.2 fifteen 10 10 - - thirty thirty 5 1,0 7 80 one fifteen - 0.3 fifteen 10 10 - - thirty thirty 5 1,0 8 thirty 40 - - 0.1 25 10 5 - - 25 thirty 5 3.0 9 85 - 10 one 0.1 twenty 10 fifteen - - 35 10 10 1,0 10 thirty - - 25 0.2 fifty one - - - 49 - - 2.0 eleven thirty 40 - 25 0.1 one fifteen 10 one - 53 twenty - 2.0 12 twenty 25 10 7 0.2 10 10 10 5 5 25 25 10 1,0 13 40 40 10 one 0.3 fifteen 10 10 5 5 25 thirty - 3.0 fourteen 75 one twenty 5 0.2 fifty 5 5 one 6 33 - - 1,0 Note: * The composition of the modifying material does not indicate the iron content, which accounts for the rest.

Claims (5)

1. A method for out-of-furnace treatment of an iron-carbon melt by introducing a flux-cored wire into the melt, characterized in that the flux-cored wire is introduced in two steps, the first of which is introduced a wire with a modifying composition, and the second - a wire with a refining composition, while a wire with a modifying composition contains iron and calcium in the form of an alloy with silicon and / or in the metal phase in the following ratio of components, wt.%: the total content of calcium and silicocalcium is 30-95, iron is the rest, and the wire is refined it contains lime, carbonate salts of alkaline earth (alkaline earth metal) and / or alkali metals (alkali metal), halide salts of alkaline earth (alkaline earth metal) and / or alkali metals (alkaline metal) in the following ratio, wt.%: lime 1-50, carbonate salts ShchZM and / or ShchM 1-25, halide salts ShchZM and / or ShchM - the rest, and a wire with a modifying composition is introduced with a flow rate of calcium of 0.1-0.3 kg per ton of melt, and a wire with a refining composition is introduced at a rate of 0, 5-5 kg of composition per ton of melt. 2. The method according to claim 1, characterized in that the wire with the modifying composition further comprises silicobarium in the following ratio of components, wt.%: Total calcium and silicocalcium content 30-95, silicobarium 1-40, iron - the rest. 3. The method according to claim 1, characterized in that the wire with a modifying composition further comprises rare earth metal alloys and oxides in the following ratio of components, wt.%: Total calcium and silicocalcium content 30-95, total content of alloys and oxides RMZ 1-25 , iron - the rest. 4. The method according to claim 2, characterized in that the wire with the modifying composition further comprises rare earth metal alloys and oxides in the following ratio of components, wt.%: Total calcium and silicocalcium content 30-95, silicobarium 1-40, total alloy content and oxides RMZ 1-25, iron - the rest. 5. The method according to claim 1, characterized in that the wire with a refining composition additionally contains carbides in the following ratio of components, wt.%: Lime 1-50, carbonate salts of ЩЗМ and ЩМ 1-25, carbides 1-10, halide salts of ЩЗМ and SchM - the rest.