RU1788031C - Plated powdered modifier - Google Patents

Abstract

The invention can be used in metallurgy, and more specifically, in the processing of liquid steel during continuous casting. SUBSTANCE: clad powder modifier, consisting of a steel shell and a powder filler containing silicon and calcium, additionally contains vanadium, titanium and iron in the following ratio of components, wt.%: Titanium 28-30; vanadium 30 32; iron 31 - 35; calcium 3-5; silicon rest. 2 tab.

Description

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The invention relates to metallurgy, and more particularly, to secondary furnace treatment of steel.

Clad powder modifiers are used in metallurgy for the refinement and microalloying of cast iron and steel. They are used to introduce chemically active elements with a high affinity for oxygen (Ca, Mg, Zr, Al, Ti, V, Si, Nb), lungs with a low density (Ca, Md, C, B, Si, Sc), and high vapor pressure ( MD, Ca, Sc, Fe), low solubility in iron (Pb, Ca, MD). The most widely clad powder modifiers are used to introduce calcium into steel, having a high vapor pressure, low solubility in iron and a high oxidation tendency. The use of these modifiers makes it possible to increase the degree of calcium uptake by several times in comparison with powder injection, which nevertheless remains at the level of 10–20% and does not allow providing residual in steel

sufficient calcium to efficiently microalloy the steel.

Closest to the technical nature of the proposed technical solution is a flux-cored wire containing silicocalcium.

The modifier used in this work consisted of a 13 mm mild steel shell and a SKC 30 type SiCa filler. SiCa consumption was 0.2 - 0.8 kg / t, calcium absorption 9 - 11%, calcium concentration in finished steel (10 - 17).

Such a calcium content in the steel is not sufficient for an effective microalloying effect, which improves the quality and mechanical properties of the metal. In order to obtain a higher concentration of calcium in steel, it is necessary to increase the degree of assimilation of this element, and to improve the quality and mechanical properties of the metal, it would be desirable to perform complex microalloying of steel

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and other elements, in particular vanadium and titanium. The introduction of expensive and easily oxidized ferroalloys containing vanadium and titanium into steel, together with SiCa as a filler of a clad powder modifier, would significantly increase the degree of assimilation of these elements and complexly microalloy the metal.

The aim of the invention is to improve the quality and mechanical properties of low alloy steel structures by increasing the degree of assimilation of chemically active elements and complex microalloying.

This goal is achieved in that the clad powder modifier containing a steel shell and a powder filler of silicon and calcium, additionally contains titanium, vanadium and iron in the following ratio, wt.%:

Titanium. 28-30 Vanadium 30-32 Iron - 31-35 Calcium 3-5 Silicon balance The composition of the clad powder modifier was chosen based on the fact that the ferroalloys used to process liquid steel should have a crystallization onset temperature of about 1400 ° C. This condition arises from the heat reserve of molten steel, the temperature of which at the outlet is 1600 ° C. Therefore, the composition of refractory ferroalloys, in particular ferro-titanium and ferrovanadium, must correspond to low-temperature eutectic or low-temperature incongruent intermetallides, decomposing to the melting point in the solid state. On the other hand, to increase the absorption of volatile elements such as calcium, it is best to use formulations which correspond to congruent melting compounds. It is known that these compounds are retained in the liquid state upon significant overheating and contribute to an increase in the degree of assimilation due to the presence of a chemical bond between the components of the intermetallic compound, since this reduces the activity and elasticity of calcium vapor and increases its evaporation temperature from the metal melt .

Analysis of the double state diagrams of Fe-Ti, Fe-V, Ti-V showed that a eutectic is formed in the Fe-Ti system at 1085 ° and 68 wt.% Ti, which corresponds to the composition of FeTi2, and in the Fe-V and Ti- systems V continuous series of solid solutions are formed. It is natural to assume that elements analogous to Ti and V will be

replace each other indefinitely in various ratios in chemical compounds and solutions. Thus, based on a double eutectic corresponding to the composition of FeTi2

there may exist a triple (Ti, V) 2Fe with unlimited solubility V VT and vice versa.

In order to increase the degree of calcium uptake, a composition was selected containing calcium and silicon in a weight ratio of 1.2-1.8. This composition is selected based on the known Ca-Si system, where the stable intermetallic compound is the chemical compound SiCa at the indicated ratio

5 and a melting point of 1245 ° C /

In the low alloy structural steel grade 14G2AF, the contents of vanadium and titanium are at the level of 0.05-0.12 wt.% Calcium 0.003-0.005%. For

To obtain the desired chemical composition, a mixture of composition 6 (Ti, V) 2Fe + SiCa is suitable, which, under the conditions of its introduction, in the form of a filler of a clad powder modifier with a steel shell, can

5 to provide the necessary content of chemically active components with significant savings in the consumption of ferroalloys and alloys.

To match the above

0 composition modifier filler should contain, wt.% GP 28 - 30; V 30 - 32; Si 2-4; Ca 3 - 5; Fe 31 - 35. The content limits of these elements are limited in that, at large deviations from the limiting values, the filler composition will not correspond to the region of existence of the triple eutectic and congruent calcium monosilicide CaSi compound (Table 1).

0 Example Clad powder modifier (which is a steel shell and filler containing a homogeneous mixture of compacted powders of calcium, titanium, vanadium, silicon,

5 iron) was made by folding a steel strip into a tube (groove) and pulling it through dies (or by rolling with rollers) while filling the inner cavity of the wire

0 pre-prepared powder mixture of the required composition, presented in table 1.

Studies on the degree of assimilation of introduced ligatures and their effect on

5, the mechanical properties of the steel being machined were carried out under industrial conditions of the Tula-Chermet NPO electric steel-smelting shop when casting a series of steel melts intended for the manufacture of metal structures in industrial buildings and

crane farms, grades 14G2AF on continuous casting machine of vertical type. Steel was smelted in an electric arc furnace with a main lining with a capacity of 6 tons.

A clad powder modifier in the form of a powder tape with a width of 16.5 mm and a thickness of 3.8 mm was fed by a tribappet into the intermediate bucket under the protective tile through a guide pipe with a diameter of 38 mm filled with metal.

To determine the degree of assimilation of the elements of the introduced ligature, metal samples were taken and the content of these elements in the steel ladle (raw metal) and in the continuously cast billet (metal treated) was determined. Samples of finished products rolled in the form of a strip 5-7 mm thick were subjected to mechanical testing.

The results of studies on the degree of assimilation of the elements of the introduced ligature and tests of the effect of clad powder modifiers on the mechanical properties of steel grade 14G2AF are given in Table 2, from which it follows that a significant improvement in the degree of assimilation of the elements of the ligature and the mechanical properties of the treated steel is achieved with filler compositions according to options 2- 5 corresponding to the claimed clad powder modifier. The most effective result was obtained using

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the composition of the filler according to the variant Ms 3, wt.%: Ca4, Ti 29, V31 / SI3, Fe 33, corresponding to a triple eutetics and congruent compound of calcium monosilicide CaSi.

The technical and economic efficiency of the proposed clad powder modifier is to save ligatures and ferroalloys by increasing their absorption, as well as improving the mechanical properties of continuously cast low alloy structural steel.

Claims (1)

SUMMARY OF THE INVENTION Clad powder modifier primarily for treating liquid low alloy structural steel, containing a steel shell and a powder filler of silicon and calcium, characterized in that, in order to improve the quality and mechanical properties of the steel by increasing the degree of assimilation of chemically active elements and complex microalloying, the filler additionally contains titanium, vanadium, iron in the following ratio of components, wt.%: titanium vanadium iron calcium silicon 28-30 30-32 31 -35 3-5 rest. 35 Table 1 table 2