RU2434966C2 - Alloy for steel de-oxidation, refining, modifying and micro-alloying (versions) - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: according to first version alloy contains wt %: silicon 30-65, aluminium 0.1-10, calcium 10-20, barium 7-20, iron 1-15, strontium 7-20, copper 0.1-10. According to the second version alloy contains wt %: aluminium 30-65, silicon 0.1-10. Contents of the rest of components correspond to the first version. Summary contents of calcium+barium+strontium in both versions of composition is over 25%.

EFFECT: raised plastic and strength properties of steel due to more efficient de-oxidation and transfer of products of de-oxidation reactions into slag; more efficient modifying and micro-alloying due to more uniform distribution of disperse strengthening phases in structure of metal.

2 cl, 4 tbl, 2 ex

Description

The invention relates to the field of metallurgy and can be used in the production of high-quality steel grades, both low-alloyed, to which high demands are made, and high-alloyed steel grades requiring a high degree of deoxidation of steel, in the production of which deoxidation with aluminum is unacceptable, for example, in the production of rail steel.

Currently, many alloys are known for deoxidation and refining of steels. Many are based on the introduction of oxygen-active materials into steel, such as aluminum (RF patent No. 2072171), ferroaluminium (RF patent No. 2310006), silicocalcium, ferrosilicobarium (RF patent No. 2369642), silicocalcium RF patent No. 2234541. The disadvantage of using one or more of the above alloys as a deoxidizer is a high percentage of those who do not have time to surface deoxidation products, such as SiO ₂ and Al ₂ O ₃ , which, when hardened, remain in the metal and worsen its plastic, strength, technological and operational properties.

To modify the steel of railway rails in order to reduce its contamination with line oxide oxide inclusions of steel, an aluminum-barium alloy is used [Reducing contamination of rails with line inclusions when steel is heated by aluminum-barium. Deryabin A.A., Kolosova E.L., Syreyshchikova V.I. and others. Byul. Central Research Institute of Chemistry "Ferrous Metallurgy", 1981, pp. 57-58.] In this case, a decrease in the anisotropy of plastic properties and a deeper deoxidation of the metal were achieved, the total oxygen content decreased from 0.0036-0.006% to 0.0026%. The modifier was seated in the bucket.

Closest to the claimed is an alloy for deoxidation and refining of steel according to the patent of Russian Federation No. 2369642 in the form of a filler for a flux-cored wire for out-of-furnace treatment of metallurgical melts, containing silicocalcium or silicocalcium and metallic calcium, halides, ferrosilicobarium containing silicocalcium with barium.

The disadvantage of this alloy is its low efficiency for modification, associated with the presence of only two modifying elements - calcium and barium, the interaction time of which with a liquid melt is limited. In addition, the filler contains no microalloying additives, which does not allow to fully obtain, when deoxidizing, refining and modifying, a complex of high strength, plastic and viscosity characteristics in metal.

The technical result is an increase in the plastic and strength properties of steel due to more efficient deoxidation and removal of deoxidation products into slag, more efficient modification and microalloying, which provide a more uniform distribution of dispersed hardening phases in the metal structure.

The specified technical result according to the first embodiment of the invention is provided due to the fact that the alloy for deoxidation, refining, modification and microalloying of steel, containing silicon, calcium, barium, iron, additionally contains copper, aluminum and strontium, while the components are taken in the following ratio, wt .%:

iron 1-15 silicon 30-65 calcium 10-20 barium 7-20 copper 0,1-10 strontium 7-20 aluminum 0,1-10

the total content of calcium + barium + strontium is more than 25%.

The specified technical result according to the second embodiment of the invention is provided due to the fact that the alloy for deoxidation, refining, modification and microalloying of steel, containing silicon, calcium, barium, iron, additionally contains copper, aluminum and strontium, while the components are taken in the following ratio, wt .%:

iron 1-15 silicon 0,1-10 calcium 10-20 barium 7-20 copper 0,1-10 strontium 7-20 aluminum 30-65

the total content of calcium + barium + strontium is more than 25%.

Alloys for deoxidation, refining, modification and microalloying of steel of the indicated compositions are characterized by a high content of active materials with respect to oxygen, silicates, aluminates, alkaline-earth elements - calcium, barium and strontium, which, when used together, make it possible to obtain more fusible compounds that are easily derived from metal to slag.

As a result of deoxidation reactions, complex fusible compounds are obtained that are chemically corresponding to anorthite regions, as well as similar compounds with barium and strontium, which are easily removed from metal to slag. Barium has an atomic size comparable to the size of the crystal lattice of iron, and cannot exert a microalloying effect, while strontium, remaining in small amounts in the metal, exerts not only a modifying, but also a microalloying effect, which positively affects the strength and plastic characteristics become. The increase in the plastic and strength properties of steel occurs due to more efficient deoxidation and removal of deoxidation products into slag due to the introduction of strontium in the alloy, which increases the activity of calcium and barium, which in turn contributes to a more complete globularization of nonmetallic inclusions, more efficient modification and microalloying, which provide more uniform distribution of dispersed hardening phases in the metal structure.

The use of the proposed alloys for deoxidation, refining, modification and microalloying of steel makes it possible to relate the residual oxygen content in steel according to the reactions:

with silicon

Si + FeO = SiO ₂ + Fe,

with calcium

Ca + FeO = CaO + Fe,

with barium

Ba + FeO = BaO + Fe,

with strontium

Sr + FeO = SrO + Fe,

with aluminum

Al + FeO = Al ₂ O ₃ + Fe,

and remove the reaction products into slag, forming fusible compounds of the type:

with calcium

CaO * SiO ₂ * Al ₂ O ₃ , melting point ~ 1600 ° С,

with barium

BaO * SiO ₂ * Al ₂ O ₃ , melting point ~ 1400 ° C,

with strontium

SrO * SiO ₂ * Al ₂ O ₃ , melting point ~ 1500 ° C,

2СаО * BaO * 3SiO ₂ , melting point ~ 1320 ° С.

The resulting fusible compounds have a melting point significantly lower than the melting point of pure Al ₂ O ₃ , component 2050 ° C, of pure SiO ₂ 1700 ° C.

These compounds more easily float from metal to slag than SiO ₂ and Al ₂ O ₃ separately, respectively, and it becomes possible to obtain steel that is cleaner in non-metallic inclusions, having better plastic and strength properties. The joint use of elements in one alloy promotes better formation of complex compounds formed by the products of deoxidation reactions, these complexes are in liquid form, which allows them to be effectively enlarged during the interaction due to the fusion of small particles into larger ones and to float out of the metal.

Also, the alloy has a modifying effect on the metal due to the presence in it of surface-active elements of barium and strontium. The modifying effect is expressed in grinding grain. The high content of active alkaline earth elements in the deoxidation alloy increases the deoxidizing ability of the alloy and additionally gives it a refining effect due to the removal of deoxidation products into slag.

The copper introduced into the alloy increases the absorption of calcium, barium, and strontium by iron-based alloys, since it has a high degree of solubility with both calcium, barium, and strontium, and with iron. Copper contributes to an increase in the specific gravity of the alloy, increases its solubility in steel, and makes it possible to obtain a more stable storage alloy with a high content of active elements Ca, Ba, and Sr. The amount of copper depends on the mass fraction of calcium, barium and strontium in the alloys. The higher the proportion of calcium, barium and strontium in the alloy, the higher the copper content it is desirable to maintain in the alloy - this allows you to simultaneously solve two problems: increase the specific gravity of the alloy and lower the initial activity of calcium, barium and strontium. With a seemingly low change in each of the indicators (specific gravity and initial activity) separately, the total effect when using the alloy is significant in the complex and provides more efficient operation of the alloy at temperatures above the boiling point of calcium, barium and strontium. A larger specific gravity and reduced initial activity have a great advantage when using an alloy in conditions of a high probability of binding of the deoxidizer to slag - feeding to the furnace, feeding to the bottom of the bucket.

The supply of any active deoxidizing agent to the slag - metal system always has one difficulty - the interaction of the deoxidizing agent with slag oxygen. This problem is relevant when using aluminum, high percent ferrosilicon and silicocalcium. Barium activity with respect to oxygen at temperatures exceeding the boiling point of calcium is higher than that of calcium. Strontium in the series of calcium, strontium, barium is the most active element, respectively, when interacting with the slag - metal system, the elements practically insoluble in iron (calcium, barium and strontium) will interact with the oxygen of the slag, and the metal will be deoxidized from the surface. The solution to this problem by supplying a deoxidizer in the form of a wire tribal apparatus is not always possible and convenient. Silicon and aluminum dissolve well in liquid steel and also interact well with oxygen, respectively, complex alloys formed by silicon, aluminum, calcium, barium, strontium will be subject to strong oxidation by both atmospheric oxygen and slag oxygen.

Copper is an element with a low affinity for oxygen and a very good solubility in iron. X-ray diffraction analysis of the described alloys showed that, with a sufficient copper content and high barium and strontium contents, the alloy contains compounds of the CuSr and CuBa type, which will better dissolve in the metal at the stage of supplying the deoxidizer to the metal and less interact with the oxygen of the slag and the atmosphere having a high temperature, rather than a compound of the type Si ₂ Sr, Si ₂ Ba or type Al ₂ Sr, Al ₂ Ba. Since barium and strontium are the most effective elements that deoxidize steel, it is possible to increase the return on their application by choosing more effective conditions for their introduction into steel.

The supply of alloy for the deoxidation of steel can be carried out in pieces in a furnace, in a dispensing ladle, a casting ladle, in a mold, or introduced into metal in the form of a flux-cored wire.

In the alloy according to the first embodiment of the invention, the percentage of silicon is 30-65%, aluminum is 0.1-10%, copper is 0.1-10%.

In the alloy according to the second embodiment of the invention, the aluminum content is 30-65%, silicon 0.1-10%, copper 0.1-10%.

In both variants of the alloy, the content of active alkaline earth elements is: Ca - 10-20%, Ba - 7-20%, Sr 7-20% and the total content of Ca + Ba + Sr> 25%.

Example 1. Testing of the alloy was carried out on steel 20GL, from which crucial parts of the rolling stock were subsequently cast.

Melting was carried out on a 5-ton electric arc furnace DSP-5 with the main lining. With standard technology, aluminum is fed into the bucket in an amount of 0.7 kg / t of liquid steel. The aim of the experiment was to maximize the deoxidation of the metal and the removal of deoxidation products from metal to slag. We evaluated: the manufacturability of the use of the alloy for deoxidation, the microstructure of steel for grain size, the size and number of non-metallic inclusions, and mechanical properties. Samples of the “club” type, which were poured separately from the casting, were investigated.

To achieve this goal, an aluminum-based alloy in the form of pieces in the amount of 0.7 kg per ton of steel was used.

The chemical composition of the alloy:

Si 5%, Al 57%, Fe 3%, Ca 13%, Ba 8%, Sr 10%, Cu l%, etc. 3%.

There were 5 heats using the proposed alloy for deoxidation and refining and 5 comparative heats using aluminum as a deoxidizing agent. The chemical composition and mechanical properties of the heats are shown in table 1 and table 2, respectively.

Table 1 Sample No. FROM Si Mn S R Al Cr Ni Cu Using deoxidation alloy one 0.2234 0.3654 1,365 0.0216 0.0432 0.0416 0,0796 0.1798 0.1105 2 0.1806 0.2827 1,027 0.0112 0,0287 0,0365 0,0644 0.1985 0.143 3 0.2125 0.4064 1,424 0.0143 0,0267 0.0477 0.1174 0.229 0.1339 four 0.2312 0.3335 1,189 0,0243 0,028 0,0336 0.76 0.1993 0.1395 5 0.202 0.4001 1,347 0.007 0,026 0,0364 0,0674 0.1408 0,0958 Average 0.2099 0.3576 1,2704 0.0156 0,0305 0,0391 0.2178 0.1895 0.1245 Using aluminum (comparative swimming trunks) 6 0.2353 0.3646 1,347 0.0168 0,0355 0,0395 0.0873 0.1773 0.1074 7 0.1841 0.2894 1,074 0.0166 0,0242 0,036 0,0652 0.2025 0.1442 8 0.2295 0.4309 1,455 0,0241 0,0305 0,0298 0.1054 0.2128 0.1342 9 0.2062 0.3247 1,132 0.0196 0,031 0,0596 0,0789 0.2088 0.1472 10 0.2019 0.2817 1,289 0.0147 0.0173 0,0209 0,0691 0.2185 0.108 Average 0.2114 0.3383 1.2594 0.0184 0.0277 0,0372 0.0812 0.204 0.1282

table 2 Sample No. σt, MPa σв, MPa δ,% ψ,% KCU-60 J KCU-60 J Using deoxidation alloy one 760 860 17 46 38 39 2 450 610 25 61 61 51 3 770 870 17 47 38 fifty four 540 700 eighteen 49 32 40 5 520 670 22 59 52 40 Average 608 742 19.8 52,4 44,2 44 Using aluminum (comparative swimming trunks) 6 540 680 twenty 54 48 60 7 500 660 19 48 42 29th 8 700 810 16 44 28 28 9 560 740 17 48 29th 22 10 590 720 eighteen 51 31 40 Average 578 722 eighteen 49 35.6 35.8 Characteristic increase,% 5,190311 2.770083 10 6,938776 24.1573 22.90503

On all experimental swimming trunks, the grain score was 8–9; on comparative swimming trunks, the grain score ranged from 6 to 9.

The amounts and sizes of inclusions of aluminates, sulfides, and silicates at grain boundaries have decreased.

The plastic and strength properties of steel, shown in table 2, increased from 10 to 23% as a result of grain refinement and metal refining.

Some reduction in sulfur in the metal was observed.

On this steel grade, in accordance with the regulatory technical documentation, the copper content should not exceed 0.3%. The conducted melts showed that the presence of copper in the alloy had practically no effect on its content in the metal. The copper content in the experimental heats was even lower than in the heats deoxidized with ordinary aluminum.

The alloy was stored for 3 months in the open air, the properties of the alloy did not change.

Example 2. The deep deoxidation of steel grade 09G2S was carried out using flux-cored wire with a filler alloy based on silicon for deoxidation and refining of steel.

Smelting was carried out on a 120-ton open-hearth furnace with subsequent metal processing on a ladle-furnace (ACP) unit. With standard technology, aluminum is fed into the bucket in the form of wire in the amount of 0.5 kg / t of liquid steel and silicocalcium in the amount of 1 kg / t of liquid steel. The aim of the experiment was to maximize the deoxidation of the metal and the removal of deoxidation products from metal to slag. We evaluated: the manufacturability of the use of the alloy for deoxidation, the microstructure of steel for grain size, the size and number of non-metallic inclusions, and mechanical properties. We studied samples cut from a finished rolled sheet with a thickness of 40 mm.

To achieve this goal, an alloy based on silicon in the form of cored wire was used. Instead of silico-calcium wire, the alloy was fed in the amount of 0.7 kg per ton of steel.

The chemical composition of the alloy:

Si 53%, Al 8%, Fe 2%, Ca 15%, Ba 9%, Sr 9%, Cu 2%, for example 3%

3 melts were carried out using the proposed alloy for deoxidation and refining and 5 comparative melts using aluminum and silico-calcium wire as a deoxidant. The chemical composition and mechanical properties of the heats are shown in table 3 and table 4, respectively.

Table 3 Sample No. FROM Si Mn S P Al Cr Ni Cu Using deoxidation alloy one 0,078 0.539 1.36 0.014 0.017 0.005 0,063 0.149 0.268 2 0,082 0.52 1.36 0.015 0.016 0.005 0,078 0.138 0.254 3 0,091 0.56 1.35 0.016 0.017 0,022 0,064 0.159 0.232 Average 0.0837 0.5397 1.3567 0.015 0.0167 0.0107 0,068 0.1487 0.251 Using silicocalcium (comparative swimming trunks) four 0,093 0.61 1.51 0.016 0.018 0,023 0,067 0.14 0.226 5 0,085 0.54 1.33 0.017 0.018 0,020 0,074 0.135 0.235 6 0,069 0.72 1,61 0.018 0.017 0.025 0,069 0.146 0.244 7 0,092 0.55 1.33 0.016 0.018 0.015 0,072 0.142 0.21 8 0,086 0.78 1.46 0.017 0.018 0.010 0,085 0.153 0.285 Average 0,085 0.64 1,448 0.0166 0.0178 0.0186 0,0734 0.1432 0.24

The treatment of steel with flux-cored wire with a filler made of a silicon-based alloy for deoxidation and refining of steel showed an increase in the mechanical properties of finished steel. A study of non-metallic inclusions showed a decrease in the number and size of inclusions of aluminates, sulfides and silicates at grain boundaries.

Experimental swimming trunks also showed a slight decrease in sulfur in the metal.

On this steel grade, in accordance with the regulatory technical documentation, the copper content should not exceed 0.3%. The conducted melts showed that the presence of copper in the alloy had practically no effect on its content in the metal. The copper content in the experimental melts is slightly higher than in the melts treated with ordinary silico-calcium wire.

Claims (2)

1. An alloy for deoxidation, refining, modification and microalloying of steel containing silicon, calcium, barium, iron, characterized in that the alloy additionally contains copper, aluminum and strontium in the following ratio of components, wt.%:
iron 1-15 silicon 30-65 calcium 10-20 barium 7-20 strontium 7-20 copper 0,1-10 aluminum 0.1-10
the total content of calcium + barium + strontium is more than 25%. 2. An alloy for deoxidation, refining, modification and microalloying of steel containing silicon, calcium, barium, iron, characterized in that the alloy additionally contains copper, aluminum and strontium in the following ratio of components, wt.%:
iron 1-15 silicon 0,1-10 calcium 10-20 barium 7-20 strontium 7-20 copper 0,1-10 aluminum 30-65,
the total content of calcium + barium + strontium is more than 25%.