RU2502808C1 - Modification and refining compound for iron-carbon and non-ferrous alloys (versions) - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: compound includes material containing calcium, barium and strontium carbonates; with that, it contains the following components, wt %: CaO 16.0 - 40.0, BaO 10.0 - 24.0, SrO 2.5 - 11.5, CO₂ 18.0 - 30.0, SiO₂ 2.0 - 15.0. In addition, compound can contain carbon-bearing material or metallic aluminium in quantity of 2-35 wt %, or titanium-bearing material in quantity of 0.01-35 wt %, or rare-earth metals in quantity of 2-49.5 wt %.

EFFECT: invention allows improving refining and modifying properties of compound due to optimisation of chemical composition and addition to compound of new elements.

5 cl, 4 ex, 5 tbl

Description

The invention relates to the field of metallurgy, namely, to the production of materials for furnace and secondary furnace processing of steel, cast iron and non-ferrous metals in order to increase their casting, mechanical and operational properties. The modifier can be used in foundry and metallurgical industries.

Known modifier with a refining effect patent RU No. 2364649 used for out-of-furnace refining and modification of steel, cast iron and non-ferrous alloys.

The disadvantage of this modifier is the low content of the main modifying element - strontium and, as a result, low modifying and refining ability.

Known wear-resistant cast steel, smelted using barium carbonates of calcium and strontium RU No. 94045199.

Also known is “Batch for smelting cast iron in a cupola”, patent RU No. 2343202, in which calcium barium and strontium carbonates are used as a refining and modifying additive. The disadvantage of this invention is the restriction in its use only in the cupola process.

The closest in technical essence to the proposed composition for refining and modification is a natural mineral barium-strontium-calcium carbonate used for out-of-furnace steel processing patent RU No. 22215046. It is successfully used in an amount of 4-7 kg for out-of-furnace steel processing.

The disadvantages of the natural material are the large sizes of pieces of carbonate, as a result, reduced reactivity and efficiency in the processing of steels and cast irons, as well as the inability to use non-ferrous alloys for processing. The disadvantage is the increased content of SiO ₂ , which negatively affects the efficiency of refining and modification by neutralizing most of the active substances.

An object of the invention is to improve the refining and modifying properties of the composition by optimizing the chemical composition and adding new elements to the composition.

, а суммарное содержание карбонатов СаСО₃+ВаСО₃+SrCO₃>50%, при этом карбонаты кальция бария и стронция в пересчете на оксиды содержатся в составе в количестве, мас.%:According to the first claim, the achievement of the technical task is achieved due to the fact that the composition for modifying and refining iron-carbon and non-ferrous melts, including calcium, barium and strontium carbonates, the ratio of the total content of calcium, barium and strontium oxides to the total content of silicon oxides

and the total carbonate content of CaCO ₃ + BaCO ₃ + SrCO ₃ > 50%, while the calcium carbonates of barium and strontium in terms of oxides are contained in the composition in the amount, wt.%:

CaO 16.0-40.0 Wow 10.0-24.0 Sro 2.5-11.5 CO ₂ 18.0-30.0 SiO ₂ 2.0-15.0

According to the second claim, the achievement of the technical task is carried out by the fact that the composition additionally introduces carbon-containing material (coal, coke, graphite, etc.) in an amount of 2-35 wt.%.

According to the third paragraph of the claims, the achievement of the technical task is achieved by the fact that metallic aluminum (powder, granular) is added to the composition in an amount of 2-35 wt.%.

According to the fourth paragraph of the claims, the achievement of the technical task is achieved by the fact that the composition is additionally introduced titanium-containing material (in pure form or in the form of an alloy with other metals) in an amount of 0.01-35 wt.%.

According to the fifth claim, the achievement of the technical task is carried out by the fact that rare earth metals in an amount of 2-49.5 wt.% Are additionally introduced into the composition.

When using the proposed composition, an important factor is the basicity of the composition - this is the concentration of the active basic substances (alkali carbonates) in it with respect to acidic impurities (silicon and iron oxides). Silicon oxide is an impurity and does not affect the metal, at the same time in small amounts it participates in the modification process as a substance that lowers the melting point of the system (Ba, Ca, Sr) CO ₃ - (Ba, Ca, Sr) O - SiO ₂ , but its excess also negatively affects the modification process by binding active alkaline earth metals and their oxides to durable compounds, which in turn go to slag without interacting with metal and HB. Iron oxide has a negative effect on the metal. In comparison with the prototype in this composition, the iron content is minimized, and the content of silicon oxide is reduced to optimal. If the composition is basic below 2, the effectiveness of the composition is reduced. The basicity of the material used in the prototype is about 1.7. Optimization of the content of silicon and iron oxides and an increase in basicity contribute to an increase in the refining and modifying ability of the composition.

When the content of carbonates is less than 50%, the effectiveness of the composition is reduced. This is due to the increased content of impurity components (SiO ₂ ) which during reactions in the liquid metal bind to impurities in strong compounds. When the carbonate content is less than 50%, a higher consumption of the composition is required, accordingly, the complexity of the modification process increases and its efficiency decreases. With a carbonate content of more than 50%, the composition has a high modifying and refining ability.

The composition of the mixture includes components similar to those indicated in the prototype, but they are taken in a different ratio. The proposed ratio of components more effectively affects the metal structure, mechanical and operational properties by increasing the content of alkali metal carbonates and the optimal content of SiO ₂ .

The processing of iron-carbon and non-ferrous alloys with a composition for refining and modification can significantly reduce the content of harmful impurities in the metal and increase the content of active elements (BaO, CaO, SrO) in the slag, which leads to an increase in the casting, mechanical and operational properties of steels, cast irons and non-ferrous alloys.

As a result of grinding to fractions less than 4 mm, the total surface area of the modifier particles sharply increases, which significantly increases the reactivity of the material and makes it possible to efficiently conduct ladle processing of not only steel, but also cast iron, as well as non-ferrous alloys.

In the crystallization process, adsorption phenomena associated with the presence of surface-active impurities are important. Adsorbed substances lower interfacial surface energy, changing the crystallization parameters. This has a great influence on the formation of the crystal itself, the nature of the boundary phases, the shape and distribution of non-metallic inclusions. The decrease in surface tension at the melt – crystal interface is associated with the enrichment of the surface layer with active elements (S, O, P, N) or the formation of FeO, AlN, MnS, etc. films on the surface. Refining and modification through the use of a new finely dispersed modifier can effectively affect the adsorption process by removing harmful impurities and gases, changing the nature of crystallization and the redistribution of crystallizing phases and their number. The dispersion of the modifier increases the surface of interaction with metal several times in comparison with large pieces (up to 50 mm). Therefore, the treatment of steels with the proposed composition in finely dispersed form significantly increases their fluidity, crack resistance, strength, wear resistance and cold resistance. The achieved decrease in the size of dendritic crystals and grain upon the introduction of highly active elements in carbonate into steel is accompanied by an increase in the intergranular surface and a decrease in the specific boundary concentration of impurities. This favorably affects the properties.

The material can serve as a substitute for expensive and scarce fused master alloys and ferroalloys, which are used to process steel melts, in particular ferrocerium, silicocalcium, silicobarium, etc.

Introduction to the melt of the composition in an amount of 2-7 kg / t increases the fluidity of the iron-carbon melts due to the fact that during refining and modification there is a change in the crystallization pattern, in particular, a decrease in the size of the crystals. The combination of this factor with the refining action of barium, calcium and strontium carbonates provides an increase not only in fluidity, but also in crack resistance of alloys.

When carbon-containing material is added to the composition in an amount of 2-35%, the balance of chemical reactions that occur during the interaction of the composition with the metal in the melt changes. Thus, the probable reactions of the formation of barium, calcium and strontium carbides are intensified,

CaCO ₃ + C = CaC ₂ + 3CO, dG _1500C = -2008332 J \ mol

BaCO ₃ + C = BaC ₂ + 3CO, dG _1500C = -2148690 J \ mol

SrCO ₃ + C = SrC ₂ + 3CO, dG _1500C = -893420 J \ mol

Judging by the Gibbs energy of these reactions, we can say that the probability of their occurrence is quite high.

When steel with the proposed composition was treated, pure barium, calcium and strontium formed as a result of reactions of aluminum, silicon and carbon oxide using aluminum silicon and carbon contained in the metal and “freshly prepared” carbides of SchZM have a modifying, refining and microalloying effect. For the most effective interaction of SHZM carbides with metal, a high temperature (1600-1800 ° C) is required, achieved only in the arc zone in an electric arc furnace or AKOS. Gaseous carbon monoxide released during this reaction is a good deoxidizer, and also sparges the metal, rising through it.

An addition of carbon of less than 2% does not significantly affect the efficiency of the material. The addition of more than 35% carbon is impractical, since the excess carbon is not involved in the recovery of alkali metal oxide, but burns in the slag and, in rare cases, can lead to carbonization of the metal, which is also not desirable in the production process as it can lead to defective metal in chemical composition.

The addition to the composition of metallic aluminum (powder or granular) in an amount of 2-35% increases the likelihood of occurring due to the close location of the reacting substances aluminothermic reactions such as:

4СаО + 2Al = 3Са + CaO · Al ₂ O ₃

4ВаО + 2Al = 3 Ва + BaO · Al ₂ O ₃

4SrO + 2Al = 3Sr + SrO · Al ₂ O ₃

3CaO + 2Al = 2Ca + (CaAl ₂ ) O ₄

3BaO + 2Al = 2Ba + (BaAl ₂ ) O ₄

3SrO + 2Al = 2Sr + (SrAl ₂ ) O ₄

As a result of the intensification of the reactions of the formation of pure barium and strontium, these substances interact with the components of the melt, providing a modifying, refining, and microalloying effect. The reaction products (CaO · Al ₂ O ₃ , BaO · Al ₂ O ₃ , SrO · Al ₂ O ₃ ) are removed from the metal to slag. For such reactions to occur, a temperature of 1000-1200 ° C is sufficient.

An addition of aluminum of less than 2% does not affect the efficiency of the material, an addition of more than 35% leads to the fact that aluminum, in addition to activating the composition and deoxidation of the metal and slag, can remain in the metal with the formation of aluminosilicate starch inclusions.

The introduction of a titanium-containing material (in pure form or in an alloy with iron or another metal) gives a deeper deoxidation of the metal due to the high affinity of titanium to oxygen and the formation of titanium nitrides, which in turn are additional crystallization centers, which contributes to the refinement of the microstructure of the iron-carbon melt . The introduction of titanium into steel together with the patented composition is an effective way to simultaneously deoxidize, refine and modify steels.

The introduction into the composition of rare-earth metals in pure form, alloy, or another compound provides an increase in the refining and modifying ability of the composition due to the formation of complex and finely dispersed compounds with nonmetallic inclusions, which are additional crystallization centers and are located in the metal not at the grain boundaries, but directly in the grain body. The formation of new stable crystallization centers promotes crystallization of a metal with a finely dispersed microstructure.

The compositions are recommended to be used for both furnace and ladle processing of steels and alloys, depending on the brand of metal being modified and the smelting unit. On arc furnaces, the joint use of the compositions can be used, for example, the composition according to paragraph 1 of the claims can be used in the furnace before release, and the composition according to paragraph 4 of the claims can be used at the bottom of the steel pouring ladle. In an induction furnace, it is better to use furnace processing of metal. The composition according to paragraph 1 of the claims is more focused on the refinement of alloys, the composition according to paragraph 2 of the claims is oriented to refining and diffusion deoxidation of metal, the composition according to paragraph 3 of the claims is oriented to deoxidation of metal and graphitizing treatment of cast iron. The compositions according to paragraphs 4.5 of the claims are focused on modification (grinding of the metal structure)

Example 1

The melts were carried out on a DSP-5 electric arc furnace with a main lining. The effectiveness of the composition was tested on steel 110G13L. The composition was supplied in an amount of 3 kg / t to the furnace 5 minutes before release and to the bottom of the bucket before release in an amount of 2 kg. We used a composition containing components in the following ratio:

CaO 24% Wow 23% Sro 10.5% CO ₂ twenty% SiO ₂ 8% Impurities 14.5%

Table 1 shows the test results of the patented composition in comparison with the results of using the prototype.

Table 1 Experience Mechanical and casting properties of steel 110G13L Grain score σ _in , MPa KCV-70, MJ / m ² Crack resistance, N Using prototype one 820 0.6 1230 3 2 1050 0.72 1390 6 3 118.6 0.98 1470 6 four 850 0.69 1360 four Average 976.5 0.7475 1362.5 4.75 Using a patentable composition one 123.0 0.8 1350 3 2 156.0 0.9 1540 one 3 110.0 1,1 1300 2 four 112.4 0.8 1450 2 5 957 0.75 1480 four Average 1194 0.87 1424 2,4

From a comparison of the data in the table shows that the metal structure in comparison with the prototype becomes finer, increased crack resistance, impact strength and temporary resistance. This suggests that the proposed composition gives the best modification efficiency.

Example 2

The composition according to paragraph 3 of the claims, containing components in the following ratio:

CaO 22% Wow 19% Sro 9.5% CO ₂ 19% SiO ₂ 6% Al fourteen% Impurities 10.5%

Tested to modify 20GL steel smelted in an open-hearth furnace. Steel from the furnace was produced in two buckets through a forked trough. The modification was carried out in one bucket by adding the composition to the bottom of the bucket in the amount of 7 kg / t of liquid steel. The second bucket was produced using standard technology in accordance with the ND. Studies of the mechanical properties of this heat are carried out. The results of mechanical tests and micro studies are shown in table 2.

Table 2 shows that the modification by the composition led to grain refinement, a change in the type of non-metallic inclusions, and an increase in the plastic characteristics of steel, in particular, impact strength at negative temperature on specimens with “V” shaped and “U” shaped notches, as well as positive dynamics of relative compression .

Table 3 shows the chemical composition of the steel of both buckets:

From table 3 it is seen that there was a decrease in the content of harmful impurities in the metal treated with the composition as compared to the metal without using the composition. This confirms the high refining ability of the proposed composition.

Example 3

In order to increase the uniformity of the structure of graphite cast iron and increase the tightness of castings using the composition, experimental casting of samples was carried out to study the structure, mechanical properties, tendency to bleach, fluidity, as well as experimental castings from gray cast iron. For modification used the composition according to paragraph 2 of the claims, in which the components are taken in the following ratio:

CaO eighteen% Wow 19% Sro 8.5% CO ₂ eighteen% SiO ₂ 7% FROM twenty% Impurities 9.5%

The casting was carried out with ladles with a capacity of 2.2 tons. Comparative tests of two variants of the ladle modification technology to increase the objectivity of the results were carried out on cast iron of one heat, sequentially alternating experimental and traditional melt processing.

From each test bucket poured:

- for the study of mechanical properties - 2 cast samples with a diameter of 30 mm and a length of 300 mm according to GOST 24648,

- to determine the microstructure - V-shaped test for mechanical testing according to GOST 24648, drawing 5, type II,

- to determine the tendency of cast iron to bleach after modification - a wedge-shaped sample,

- to study the fluidity of the melt - spiral sand sample in accordance with GOST 16438,

The samples were poured for mechanical tests, microstructure, and bleached by a 10 kg bucket at a temperature of 1360–1380 ° C.

The chemical composition of the base melt in the cast iron and cast iron furnace after the modifying treatment is presented in table 4.

Table 4 Cast iron C Si Mn Cr Cu Ni Ti S P Furnace Cast Iron 3.19-3.30 1.76-1.85 0.61-0.64 0.30-0.31 0.20-0.22 0.12-0.15 0,03 0.022-0.024 0,031-0,035 Using standard production technology 3.13-3.27 2.19-2.28 0.91-0.94 0.30-0.31 0.20-0.22 0.12-0.15 0,03 0.022-0.024 0,031-0,035 Using a patentable composition 3.13-3.27 2,33-2,42 0.95-0.99 0.30-0.31 0.20-0.22 0.12-0.15 0,03 0.019-0.020 0.031-0.035

The test results of the samples are presented in table 5.

Table 5 Cast iron Liquid flow, t ° - 1379, sandy dry Bleached mm σ _in , MPa HB Microstructure, GOST 3443 Using standard production technology 85 2.0-2.4 270-280 207-224 PGf1-PGf2, PGr1,2,9, sections - PGr3, PGd25-90Pt1, PD0,3-0,5, P (F0) Using a patentable composition 97 2.0-2.2 290 224-230 PGf1-PGf2, PGr1.2, sections - PGr9, PGd25-90Pt1, PD0.3-0.8, P (Ф0)

As follows from table 5, cast irons obtained during pilot melts using the new technology have better fluidity in the molten state and more uniform structure and properties in the solid state. The obtained result can be explained by the synergistic effect of the joint action on the melt, which is a complex multicomponent system, of several physical and chemical factors:

- mixing the melt due to the boiling bubbles of CO ₂ formed during the decomposition of carbonates inside the volume of the melt,

- degassing of the melt from the gases dissolved in it due to the formation of CO ₂ bubbles having an initial zero partial pressure of these gases,

- mechanical energy and cavitation effects of CO ₂ bubbles on the cluster structure of the melt,

- local supercooling of the melt microvolumes during the formation, growth and expansion of CO ₂ bubbles in the melt volume, the refining and nucleating action of “freshly prepared” alkali metal oxide oxides formed during the decomposition of carbonates inside the melt volume,

In the cast iron melt, which is a nonequilibrium physicochemical medium, under the influence of these factors, the processes of self-organization of its structural components (self-controlled structure formation of complex systems) are actively taking place, leading to a certain order, that is, the structure of the melt, which ensures the properties discovered during testing.

Thus, the tests of the refining-modifying effect of the composition for refining and modification together with FS75 ferrosilicon in the manufacture of gray iron castings under conditions of arc melting showed that mechanical properties, tendency to bleach and microstructure satisfy the requirements of regulatory documentation, in particular, grade SC25 in accordance with GOST 1412. Moreover, the use of the composition led to a slight increase in the uniformity and stability of the microstructure, in particular, to a decrease in the amount of dendritic graphite and graphite exclusion colonies, as well as mechanical properties increase process cost reduction and fluidity modifying treatment as compared with conventional technology.

Example 4

Five pilot melts of tinless bronze of the BrA9ZhZL brand were carried out. The melts were carried out on bronze wastes without double remelting and without the use of a deoxidizer (phosphorous copper). For deoxidation and degassing of bronze was used the composition according to paragraph 1, containing components in the following ratio:

CaO 22% Wow 21% Sro 9.5% CO ₂ 19% SiO ₂ 10% Impurities 18.5%

The composition for refining and modification was supplied after the metal was melted and heated to a temperature of 1200 ° C, at the rate of 0.2-0.3 kg per 100 kg of metal. When used to enter the composition into a ladle with an alloy, formation of nastily on it and a slight decrease in the temperature of the metal were noted.

When using the "bell" to enter the composition into the crucible, the modifier was not digested and partially surfaced into the slag. When fed to the bottom of the crucible, the composition also has a strong degassing effect.

According to the results of chemical analyzes, macro and microstructural studies and visual inspection of the machined parts, it was found:

- samples cast from a modified composition of bronze have a decrease in metal level in the center of the sample, in contrast to samples cast with natural carbonate modification and having a flat surface or a slight decrease in the metal level in the center of the sample.

- castings obtained from a modified bronze composition have significantly fewer gas sinks than samples cast using a prototype.

- modification contributes to the grinding of grains of the structural components of bronze.

Using the proposed composition as a modifier allows for the complete degassing of the BrA9ZhZL alloy and the production of castings with lower gas porosity than when using the prototype.

Claims (5)

1. The composition for modifying and refining iron-carbon and non-ferrous melts, including material containing calcium-barium-strontium carbonates, characterized in that it contains components in the following ratio, wt.%:
CaO 16.0-40.0 Wow 10.0-24.0 Sro 2.5-11.5 CO ₂ 18.0-30.0 SiO ₂ 2.0-15.0 2. Composition for modifying and refining iron-carbon and non-ferrous melts, including a material containing calcium-barium-strontium carbonates, characterized in that it contains carbon-containing material (C) in the following ratio of components, wt.%:
CaO 16.0-40.0 Wow 10.0-24.0 Sro 2.5-11.5 CO ₂ 18.0-30.0 SiO ₂ 2.0-15.0 FROM 2.0-35.0 3. Composition for modifying and refining iron-carbon and non-ferrous melts, including a material containing calcium-barium-strontium carbonates, characterized in that it contains metallic aluminum (Al _met ) in the following ratio, wt.%:
CaO 16.0-40.0 Wow 10.0-24.0 Sro 2.5-11.5 CO ₂ 18.0-30.0 SiO ₂ 2.0-15.0 Al _met 2.0-35.0 4. Composition for modifying and refining iron-carbon and non-ferrous melts, including a material containing calcium-barium-strontium carbonates, characterized in that it contains a titanium-containing material (Ti) in the following ratio, wt.%:
CaO 16.0-40.0 Wow 10.0-24.0 Sro 2.5-11.5 CO ₂ 18.0-30.0 SiO ₂ 2.0-15.0 Ti 0.01-35.0 5. A composition for modifying and refining iron-carbon and non-ferrous melts, including a material containing calcium-barium-strontium carbonates, characterized in that it contains rare earth metals (REM) in the following ratio, wt.%:
Cao 16.0-40.0 Bao 10.0-24.0 Sro 2.5-11.5 CO ₂ 18.0-30.0 SiO ₂ 2.0-15.0 REM 2.0-49.5