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Development and mastering of deoxidation and alloying technology of ShKh15SG-V bearing steel using MnS25 ferromanganese silicon.

Statement of the problem. One of directions of the OJSC << Dneprospetsstal >> marketing strategy is increase of the bearing steel production for OJSC << Kharkovsky Bearing Plant >> (KhBP). The latter plans to organize supply of their products to a number of leading automobile concerns (Toyota, Nissan, Volkswagen), which open their branches in Russia, and master production of high-precision large-size bearings for mobile stock of Ministries of Railways of CIS countries.

Production of steel for large-size bearings with increased calcination capacity, ensured in the ShKh15SG-V steel (GOST 3756-73) by weight share of manganese 0.90-1.20 and silicon 0.40-0.65% and in the ShKh15 steel respectively by 0.20-0.40 and 0.17-0.37%, is more complex than production of other kinds of bearing steels concerning technical-economic parameters of through technology of melting and ladle treatment of the metal.

In [1] results of the technology of melting and ladle treatment of the ShKh15SG-V steel with application of imported 75% ferrosilicon (Ca less than or equal to] 0.1%) instead of national FS65 ferrosilicon (DSTU 4127-2002), containing 0.3-0.5% Ca [2, 3], are presented. It was established that application in the experimental campaign of the imported ferrosilicon and ferromanganese of the FMn78A grade (DSTU 3547097) with ladle treatment of the metal according to the used at the Dneprospetsstal through technology of the ShKh15SG-V steel production did not allow improving steel quality with stably low parameters concerning globular and oxide inclusions. Assessment of the metal quality (GOST 801-78 and ASTM E45, method A) relative globular kinds of inclusions showed that certain reduction of contamination of the billets and sectioned rolled stock was accompanied by increase of the oxide inclusions. So, assumed significant increase of yield of the efficient sectioned rolled stock of comparable geometric size was not achieved [1].

It should be especially noted that constantly increasing requirements of the bearing metal consumers to quality of the metal products stipulate the need to continue scientific researches and development of new technologies for increasing degree of the steel purity from non-metal inclusions. Multiple investigations [2, 3] of micro- and macrostructure of the bearing steel and bench tests of the metal quality showed dangerous influence of non-metal inclusions on operation characteristics of bearings. Occurring in zone of contact of the roller with the bearing rings volumetric stress state of the metal that causes change of metal-physic properties up to structural change of the steels in the contact zone in the pair system ball (roller)--ring causes incoherence of elastic-plastic properties of the inclusions--metal matrix interphase boundary with subsequent development of pitting (chunk-out of the metal).

In [4] interaction between the hazard parameter and dimensions of different chemical-mineralogical inclusions are presented (Figure 1). The highest hazard in regard to reduction of service life of a bearing cause large-size difficultly formed in the process of rolling of the metal inclusions, which preserve in ready metal products shape of globules. Non-metal inclusions represent calcium aluminates of homogeneous structure, heterophase complexes, which include compounds (solutions) of the CaO-[Al.sub.2][O.sub.3] system, and spinel-like (Mg, [Fe.sup.2+])O[(Al, [Cr.sup.3+], [Fe.sup.3+]).sub.2] [O.sub.3] phases. As a rule, in analysis of conditions of formation of inclusions priority of absolute contents of dissolved in the metal oxygen and an element-deoxidizer is established. At the same time special significance acquires ratio of activities of both elements-deoxidizers ([a.sub.Mn], [a.sub.Si], [a.sub.Al]) and non-controlled by standards in the course of melting and ladle treatment elements ([a.sub.Mg], [a.sub.Ca]) [5-7]. By means of change of activities of the deoxidizers in course of deoxidation of molten steel and during solidification of the metal, crystallization and solid-phase reactions of formation of oxide phases occur in certain areas of phase equilibriums of the CaO-MgO-[Al.sub.2][O.sub.3]-Si[O.sub.2] system.

Content, chemical-mineralogical composition, and dimensions of non-metal inclusions depend upon a number of the following priority factors: thermodynamic activity of used deoxidizers and their composition, temperature-time conditions of deoxidation and ladle treatment of the metal, methods of steel casting, limitation of secondary oxidation, quality of bottom-pouring refractories (high heat resistance and low erosion), weight of the ingots (duration of the metal crystallization), and geometrical dimensions of sectioned rolled stock, which effects deformability of inclusions.

Physical-chemical audit of used technology of melting and refining of steel. Physical-chemical audit of melting processes and ladle treatment of the ShKh15SG-V steel, carried out according to the used technology with application of national FS65 ferrosilicon and experimental technology with application of imported low-calcium 75% ferrosilicon allowed detecting shortcomings of through technology at stages of the molten steel alloying and deoxidation and stipulating the innovation through technology of the ShKh15SG-V steel production under conditions of Dneprospetsstal [8, 9].

Theoretical analysis of the processes and material balance of the steel deoxidizers (calcium and aluminium) at all stages of ladle treatment showed that although << excessive >> amount of calcium during casting and crystallization of metal in the mould (weight of the ingot equaled 3.6 t) ensures with residual (dissolved) aluminium a relatively low content of the dissolved (active) oxygen, at the same time it is to a significant degree responsible for formation of increased amounts and dimensions of both globular inclusions in steel on basis of CaO-[Al.sub.2][O.sub.3] and heterogeneous inclusions on basis of CaO-[Al.sub.2][O.sub.3]-MgO-Si[O.sub.2] (Figure 2, Table 1).

Investigations, carried out at the Dneprospetsstal plant, showed that because of a relatively high content in the FS65 ferrosilicon of calcium, its concentration in molten steel after addition of ferrosilicon into the metal during treatment in the ladle-furnace increased up to the values, exceeding critical ones. This became the basis for performance of experimental melts of the ShKh15SG-V steel according to different options of deoxidation using aluminium and additions of the FS65 ferrosilicon into the metal (into a furnace, a ladle-furnace, a vacuumator, or addition by parts of the general amount at different stages of melting and ladle refining of the molten metal). Averaged values of chemical composition of the metal and the slag according to used technologies at different stages of melting and ladle treatment of the ShKh15SG-V steel are presented in Tables 2 and 3.

[FIGURE 1 OMITTED]

As far as heat load on surface of the slag melt (q of disintegration of electrodes on the ladle-furnace) is almost 50% higher in comparison with arc furnace of equivalent capacity ([g.sub.ladle] = 0.4; [q.sub.DSP-60] = 0.22) and occupies practically whole surface of the slag melt, in case of overheating of the slag in zone of operation of electric arcs and at higher integral temperature of the slag in the ladle-furnace installation mass-exchange processes in the slag--metal system are developed, initiated by reduction reactions with participation of the metal pool and oxide-fluoride slag components.

Source of influx of << excessive >> calcium into the metal are processes of calcium reduction from the CaO-Ca[F.sub.2] melt by silicon of the FS65 ferrosilicon, aluminium in composition of FS65 (1.5-2.0%), and aluminium powder during deoxidation of the slag in course of degassing of the metal.

Reduction of calcium at the stage of ladle treatment may be presented in generalized form by the following reactions:

Ca[O.sub.l.sl] + 1/2 [Si] + [[Ca].sub.1%] + 1/2 (Si[O.sub.2]); [DELTA][G.sub.1] = 239740 - 103.32 T [J/mol]; lg[K.sub.1] = - 12515/T + 539. (1)

Ca[O.sub.l.sl] + 2/3 [Al] + [[Ca].sub.1%] + 1/3([Al.sub.2][O.sub.3]); [DELTA][G.sub.2] = 211945 - 60.11 T [J/mol]; lg[K.sub.2] = - 11064/T + 3.14. (2)

Thermodynamic characteristics of reactions (1) and (2) are calculated, taking into account heat of dissolution and transition of the components from the standard << pure substance >> state into ideal infinitely diluted 1% solution in iron [10].

Determining according to method of A.G. ponomarenko [10] activity of the metal and slag components (Table 3) as phases with collectivized state of the electrons, it was established that values of activity of oxides at 1600 [degrees]C equal 0.345 for 50% CaO; 0.137 for 10% Si[O.sub.2], and 0.048 for 10% [Al.sub.2][O.sub.3] Then chemical potential ([[micro].sub.i] = [DELTA][G.sub.T], i/[d.sub.in] of formation of calcium solutions with content 10 ppm according to reactions (1) and (2), provided chemical potentials of the elements diluted in the metal and the flag phase are equal, acquires the following values:
T, K 1600 1700 2000 2200

[[micro].sup.(1).sub.Ca], J 1.31 1.32 0.17 -0.55
[[micro].sup.(2).sub.Ca], J 3.60 3.38 2.73 2.29


[FIGURE 2 OMITTED]

Analysis of thermodynamic data and theoretical calculations confirms prevailing influence of silicon on the calcium reduction processes and indicates technological factors for limitation of this process by reduction of the slag basicity and increase of the [Al.sub.2][O.sub.3] content.

It should be specially noted that observance of steel production conditions with rational content of calcium in molten metal is necessary, but not sufficient condition for production of sectioned rolled stock with specified index of the metal contamination with globular and oxide inclusions, corresponding to top groups of quality. That's why it is very important to ensure the most favorable state of the metal, preceding to alloying, deoxidation, and ladle treatment of the steel intermediate product in DSP-60, ladle-furnace, and vacuumator for formation of primary in molten steel and secondary non-metal inclusions within liquidus--solidus range during crystallization of metal in the mould.

Thermodynamic analysis and experimental investigations showed that at separated deoxidation of molten iron by manganese (ferromanganese) the oxides (Mn, Fe)O or pure manganese oxide are formed with melting point 1850 [degrees]C. In the Fe-Mn-O system at content of manganese in the melt 0.02% mole share (1.9% wt.%) equilibrium concentration of manganese oxide in slag phase achieves 89.8 wt.% [11]. In case of deoxidation of iron by silicon (ferrosilicon), product of the reaction is Si[O.sub.2] with melting point 1720 [degrees]C. Combined alloying and preliminary deoxidation with application of complex alloy of ferromanganese silicon are accompanied by formation (at certain weight shares of manganese and silicon in ferroalloy and molten iron) of low-melting reaction products of the MnO-Si[O.sub.2] system (Figure 3) of eutectic composition with melting point 1320 [degrees]C [12]. This situation is thermodynamically substantiated and experimentally confirmed in monography [13] and then in work [14], whereby according to the monography molten nonmetal inclusions form at temperatures of steel production in case of ratio in the metal of [% Mn] and [% Si] 3 to 8 (Figure 4).

So, if alloying and preliminary deoxidation of the metal-intermediary product as basis of the ShKh15SG-V steel is performed using ferromanganese silicon with a certain ratio of manganese and silicon, in which dissolved calcium is practically absent, it is possible to create prerequisites for formation and removal of greater part of primary non-metal inclusions and production of metal with reduced content of dissolved oxygen. Later, during introduction of aluminium at the stage of the metal treatment in the ladle-furnace and in the ladle vacuumator, thermodynamically more stable conditions should be ensured for production of steel with reduced content of globular and oxide inclusions. Ratio between amount of these two kinds of inclusions is to a great degree determined both by residual content of dissolved calcium and aluminium and ratio of their concentrations, i.e. [% Al]:[% Ca]. It follows from the diagram (Figure 5, a), which illustrates phase equilibriums in the Fe-C-O-Al-Ca system on surface of solubility of the components in molten metal that change of calcium and aluminium amount in molten metal causes formation of different primary inclusions of morphological type: homogeneous liquid-phase solutions of the CaO-[Al.sub.2][O.sub.3] system, the mCaOxn[Al.sub.2][O.sub.3] calcium aluminates, and [Al.sub.2][O.sub.3] corundum.

[FIGURE 3 OMITTED]

[FIGURE 4 OMITTED]

[FIGURE 5 OMITTED]

Participation of magnesium in formation of spinel and heterophase alumocalcium inclusions. In [5-7] influence of dissolved in the bearing steel magnesium on formation of globular heterophase inclusions, presented by the MgOx[Al.sub.2][O.sub.3] spinel both as independent phase and spinelides [(Mg, [Fe.sup.2+])Ox([Al.sup.3+], [Cr.sup.3+], [Fe.sup.3+]).sub.2][O.sub.3], is investigated. Source of influx of magnesium into the melt in melting of both steel in reduction electric furnaces [18] and ferroalloys (for example, production of metal manganese by silicothermal method [12]) are the processes of reduction of magnesium by carbon [19], silicon and aluminium from the MgO-containing linings of the furnace and slag-line area of the ladle in the course of ladle treatment.

According to data of [20], the MgOx[Al.sub.2][O.sub.3] spinel in austenite steels is formed at contents of [Mg] and [Al] equal respectively to 1 and 10 ppm (T = 1873 K). In order to exclude formation of the spinel it is suggested to control content of [Mg] and [Al] in the following way:

* replacement of the [Al.sub.2][O.sub.3]-MgO lining of the ladle walls and bottom for dolomite one;

* reduction of aluminium content in the used ferrosilicon from 1 to 0.01 wt.%;

* reduction of the [Al.sub.2][O.sub.3] content in the slag at tapping from electric arc furnace from 17-23 to 5 wt.%, renewal of the slag before treatment on the ladle-furnace installation and achievement of 2 wt.% [Al.sub.2][O.sub.3] after the treatment instead of 7 wt.% according to the valid technology.

Precision investigations [21] confirmed participation of magnesium in transformation of primarily formed corundum inclusions into heterophase structure, the nucleus of which is corundum with the MgOx[Al.sub.2][O.sub.3] spinel trimming. Crystal-chemical structure of multiphase oxide inclusions is determined by physical-chemical state of the pool, sequence of introduction of the deoxidizers, and interaction of dissolved in the metal elements.

Validity of the provisions of regularities of formation of heterophase inclusions, determined by the ratio of activities of the dissolved elements-deoxidizers, is confirmed by results of investigation of the metal deoxidation by magnesium [22] and treatment of the ShKh15SG-V steel by magnesium in composition of iron-silicon-magnesium (8% Mg) hardener [6].

At introduction up to 0.3 kg/t of magnesium in the ShKh15SG-V steel of experimental melts changed crystal-chemical structure of oxide inclusions, which was stipulated by redistribution of elements-deoxidizers in process of formation of alumocalcium and spinel phases. Identification of composition of inclusions by methods of X-ray microspectral analysis detected the following intensity of X-ray radiation of the [K.sub.[alpha]] elements:

Methods of optical microscopy and X-ray microspectral analysis showed that increase of magnesium content in the melt (48 and 25 ppm, respectively, in the metal of experimental melts and the metal, produced according to valid technology) limited formation of the MgOx[Al.sub.2][O.sub.3] spinel as independent structure and created prerequisites for formation in the composition of heterophase oxide inclusions of solid solutions (Fe, Al, Mg)O.

Results of carried out investigations are confirmed by thermodynamic model of interaction reactions of dissolved in the metal calcium, aluminium and carbon with oxygen (Figure 5, b), which establishes ratios of mentioned elements for formation of solid solutions of the spinel series and liquid-phase products of deoxidation in the form of calcium aluminates.

Main provisions and options of developed technology of alloying and deoxidation of steel using the MnS25 ferromanganese silicon. Analysis of results of systemic investigations of the oxide phase formation processes in structure of non-metal inclusions and influence of technological parameters of melting and ladle treatment of steels of the bearing assortment on quality of the metal products became the basis for development of technology for alloying and deoxidation of the ShKh15SG-V steel, which ensures regulated composition of heterophase globular inclusions and reduction of general level of the metal contamination with inclusions.

In the course of industrial mastering of the ShKh15SG-V steel alloying and deoxidation the MnS25 ferromanganese silicon (DSTU 3548-97) was used, produced at OJSC ZFZ. Chemical composition of the MnS25, FMn78 and FS65 ferroalloys is presented in Table 4.

As follows from data of Table 4, content of calcium and aluminium in MnS25, which participate in the process of deoxidation and formation of globular alumocalcium inclusions, is 10-20 times smaller than in the FS65 composition. That's why during deoxidation and alloying of the metal with the MnS25 ferromanganese silicon (0.01% Ca) amount of calcium, introduced into the metal, is one order lower than in case of using FS65 (0.42% Ca) according to the valid technology.

Within the framework of this work 15 experimental-commercial melts were carried out in the DSP-60 arc reduction furnace according to five technological versions with application of the MnS25 ferromanganese silicon, which differed both by sequence of its additions into the furnace and into the ladle at tapping of the melt or at the stage of treatment of the steel in the ladle-furnace and by introduction of correction additions (ferromanganese and ferrosilicon) and aluminium at different stages (in the ladle-furnace and ladle vacuumator) of ladle treatment of the steel (Table 5).

Option 1. The metal-intermediate product was alloyed in the furnace using carbonaceous ferrochromium, having preliminarily deoxidized pool with approximately 1 kg/t of aluminium, then it was tapped into the ladle with separation of the furnace slag and creation in the ladle of oxide-fluoride slag of the CaO-Ca[F.sub.2] system with ratio of components 4:1. In the course of tapping of the intermediate product into the ladle the MnS25 ferromanganese silicon was added. Correction of manganese and silicon content was performed in the ladle-furnace. Because of discordance of carbon content in the steel at the stage of the metal treatment in the ladle vacuumator, caused by low share of carbon influx with the MnS25 addition (% C < 0.35), steel in the ladle was carbonized by the coke powder, which is not envisaged by the valid technological instructions. This enabled increased contamination of the steel with inclusions, which was taken into account in analysis of results of the delivery and investigation control of the billets and sectioned rolled stock.

Option 2. It is similar to option 1, but together with solid slag-forming materials (SFM) and MnS25 (amount of MnS25 was increased up to 850 kg per a melt) 250 kg of standard FS65 per a melt were added for correction into the ladle.

Option 3. Peculiar feature of this option is addition of MnS25 into the DSP-60 furnace before tapping. Correction of chemical composition of the metal was performed in the furnace-ladle.

Option 4. Difference of this option from the previous ones consists in addition of MnS25 in the ladle-furnace.

Option 5. The metal-intermediate product, partially deoxidized in the furnace by the FS65 ferrosilicon, was tapped into the ladle with simultaneous addition of MnS25 and deoxidation with aluminium on bars. In the furnace-ladle the steel was deoxidized by aluminium, and final deoxidation was performed in the vacuumator (Figure 6).

In the course of ladle treatment of the steel chemical composition of the slag was analyzed (Table 6).

Casting of the metal and further processing were performed according to the valid technological instructions. Change of content of the elements in process of melting of the steel is shown in Table 7.

Results of quality control of billets and sectioned rolled stock of experimental melts of ShKh15SG-V steel. Analysis of data, presented in Table 7, proves that developed technology of deoxidation and alloying of the ShKh15SG-V steel by the MnS25 ferromanganese silicon ensured reduction of calcium content in the steel down to 8.4 instead of 9.6 ppm in the serial metal, i.e. on average by 1.2 ppm. Best results were achieved in melts of options 2 and 5 of the experimental technology--respectively 6.7 and 7.1 ppm, which was stipulated by smaller amount of the correction FS65 addition in the ladle-furnace (respectively 30 and 25 kg per a melt). Content of aluminium, sulfur, nitrogen and hydrogen in steel of experimental melts was the same as in the serial metal.

According to technical norms, sampling of the metal for control in regard to non-metal inclusions was performed from rolled bars of one ingot of first bottom plate and one ingot of the last bottom plate. Horizons of the sampling corresponded to head (A), middle (B) and bottom (N) parts of each ingot. Quality control of the metal was performed using method of maximum number according to scales of GOST 801-78, and for metal of export designation using in addition the ASTM E45 scales (method A).

Methodology of the metal estimation using ASTM E45 (method A) is characterized by priority of parameters relating to oxide inclusions, while scales of GOST 801-78 contain more rigid requirements to heterophase globular inclusions. That's why comparative analysis of the metal quality according to two normative documents is subject to further investigations.

Integrated parameters of the delivery and investigation control of the metal of experimental melts and the metal, produced according to the valid technology (with application of the FS65 ferrosilicon and the VMn78 ferromanganese) in relation to content of nonmetal inclusions, are presented in Table 8. Carried out within the framework of the investigation control X-ray spectral microanalysis of inclusions of the ultimate number according to GOST 801-78 (I group-number > 2, V group-number > 3) showed that composition of globular inclusions is presented by heterophase formations, containing calcium, aluminium, magnesium, and silicon; oxide row inclusions are formed with participation of elements of aluminium, calcium, magnesium manganese and sulfur.

Criteria of efficiency of the developed technology of deoxidation and alloying of steel using the MnS25 ferromanganese silicon are assumed parameters of yield of efficient metal from the first control, which excludes fulfillment of a repeated control on doubled number of specimens and redirecting of the metal for rolling for another profile and number of specimens with drop-outs in regard to inclusions (globules, oxides, and sulfides).

Analysis of data, presented in Tables 7 and 8, proves that melting of steel with application of MnS25 according to the technological option 5 ensures reduction of calcium in the experimental metal from 9.6 down to 7.1 ppm (by 26%) in comparison with valid technology, and reduction 1.9 times contamination with globular inclusions (from 11.2 to 5.7% of drop-outs), oxide inclusions (from 4.5 down to 3.4% of drop-outs) and increase of the efficient metal yield from the first control from 64 to 89% [23]. Presented indices were used as a basis for determining rational scheme of application of MnS25 for alloying and deoxidation of the ShKh15SG-V steel according to technological option 5--production of an intermediate products partially deoxidized by silicon in the furnace with cutoff of the furnace slag, alloying and deoxidation of MnS25 in process of pouring of the metal into the ladle, deoxidation in the ladle by aluminium on bars and subsequent ladle treatment on the ladlefurnace installations in the vacuumator under oxidefluoride slag (Figure 6).

Economic efficiency of the developed technology of the ShKh15SG-V steel production with deoxidation and alloying using the MnS25 ferromanganese silicon is achieved, without taking into account increase of the metal quality, due to reduction by 5.3 kg/t of total amount of ferroalloys (MnS25, correction additions FMn78 and FS65) with simultaneous reduction of specific consumption of ferromanganese by 90 and ferrosilicon by 56% in comparison with the valid technology.

Positive results of industrial campaign of the ShKh15SG-V steel production with application of MnS25 are prerequisites for further improvement of the through technology of melting of steel of men tioned grade with application of the MnS25 ferromanganese silicon with ratio of manganese to silicon 3.2:4.3, which is one of decisive factors in formation of liquid-phase primary inclusions and ensures improvement of economic indices of production.

CONCLUSIONS

1. The developed innovation technology of the ShKh15SG-V steel alloying and deoxidation with application of the MnS25 ferromanganese silicon (DSTU 3548-97) instead of the FMn78 ferromanga nese and the FS65 ferrosilicon was mastered, which ensured preliminary deoxidation of metal with formation of liquid-phase inclusions of the MnO-Si[O.sub.2] system that allowed reducing level of dissolved oxygen under conditions of formation of oxide phases of non-metal inclusions and simultaneous reduction of the ratio [Ca]/[Al].

2. It was established on basis of results of experimental melts with application of the MnS25 ferromanganese silicon that a rational option of technological scheme for production of the ShKh15SG-V steel is introduction of MnS25 into the ladle at pouring of the metal from the furnace (option 5), which causes reduction of calcium content in the metal by 26%, reduction of contamination of the steel with oxide inclusions 1.3 times and globular inclusions--1.9 times in comparison with parameters of the metal, produced according to the valid technology.

3. It was shown that application of the MnS25 ferromanganese silicon for deoxidation and alloying of the ShKh15SG-V steel increased yield of efficient metal from first control for I group according to GOST 801-78 up to 89% in comparison with 64% according to the valid technology.

[1.] Panchenko, A.I., Salnikov, A.S., Logozinsky, I.N. et al. (2007) Comparative experimental-industrial investigations of effect of 65% ferrosilicium with different content of calcium on contamination of steel ShKh15SG-V with globular alumocalcium inclusions. Advances in Electrometallurgy, 4, 46-52.

[2.] Spektor, A.G., Zelbet, B.M., Kiseleva, S.A. (1980) Structure and properties of roller-bearing steel. Moscow: Metal lurgiya.

[3.] Orzhitskaya, L.K., Spektor, Ya.I., Shugulnaya, E.A. et al. (2005) Nonmetallic inclusions and service life of bearings of steel ShKh15 in a variety of production methods. Elektrometallurgiya, 11, 5-10.

[4.] Volkmut, J., Wilke, F. (2007) Roller-bearings steel: new developments and testing procedure to provide the long-term service life of bearings. Chyorn. Metally, 1 , 49-54.

[5.] Gasik, M.I. (1978) Magnesium in electric steel and some physico-chemical aspects of problem concerning the production of bearing metal range with programmed composition and content of nonmetallic inclusions. In: Metallurgy and coke chemistry. Issue 56. Kiev: Tekhnika.

[6.] Gasik, M.I., Shulte, Yu.A., Gorobets, A.P. (1983) Physicochemical principles of processes of globular inclusion formation in bearing metal. Izvestiya Vuzov. Chyorn. Metallurgiya, 5, 10-15.

[7.] Gorobets, A.P. (1984) Study of conditions of nonmetallic inclusion formation with the purpose of contamination decrease in bearing steel by globular inclusions: Syn. of Thesis for Cand. of Techn. Sci. Degree. Dnepropetrovsk: DMetI.

[8.] Salnikov, A.S., Logozinsky, I.N., Gasik, M.I. (2007) Comparative examinations of influence of chamotte and high-aluminous (imported) siphon refractories on contamination of billets and bars of steel ShKh15SG-V by nonmetallic inclusions. Metallurg. i Gornorudn. Promyshlennost, 5, 27-36.

[9.] Gasik, M.I., Panchenko, A.I., Logozinsky, I.N. et al. (2008) Thermodynamic backgrounds of processes of oxide and globular nonmetallic inclusion formation at different residual contents of calcium and aluminium. Ibid., 1 , 48-54.

[10.] Grigoryan, V.A., Stomakhin, A.Ya., Utochkin, Yu.I. et al. (2007) Physico-chemical calculations of electric furnace steelmaking processes. Moscow: MISiS.

[11.] Pivovarov, Yu.N., Dashevsky, V.Ya. (2006) Thermodynamics of oxygen solutions in Fe-Mn melts. Metally, 4, 11-16.

[12.] Gasik, M.I., Lyakishev, N.P. (2005) Physico-chemistry and technology of electroferroalloys. Dnepropetrovsk: Systemn. Tekhnologii.

[13.] Samarin, A.M. (1956) Physico-chemical bases of steel deoxidation. Moscow: Nauka.

[14.] Chujko, N.M., Chujko, A.N. (1983) Theory and technology of electric melting of steel. Kiev, Donetsk: Vyshcha Shkola.

[15.] Mikhajlov, G.G., Vilgelm, E.M., Chernova, L.A. et al. (1988) Phase formation in deoxidation of steel with silicium and aluminium. Metally, 4, 10-16.

[16.] Mikhajlov, G.G. (1986) Thermodynamic principles of optimization of processes of steel deoxidation and modification of nonmetallic inclusions: Syn. of Thesis for Dr. of Techn. Sci. Degree. Moscow: MISiS.

[17.] Mikhajlov, G.G. (2004) Effect of magnesium on phase transformations in liquid steel. Elektrometallurgiya, 5, 11-18.

[18.] Zhalybin, V.I., Ershov, G.S. (1977) On reduction of lining magnesium in melting of steel alloyed with aluminium. Izvestiya Vuzov. Chyorn. Metallurgiya, 12, 69-71.

[19.] Gorobets, A.P. (1981) Physico-chemical properties of alkaline-earth metals and their behavior in metal melts. In: Metallurgy and coke chemistry. Issue 74. Kiev: Tekhnika.

[20.] Sakata, K. (2006) Technology of production of austenite type clean stainless steel. ISIJ Int., 46( 12), 1795-1799.

[21.] Takata, R., Yang, J., Kuwabara, M. (2007) Characteristics of inclusions generated during Al-Mg complex deoxidation of molten steel. Ibid., 47(10), 1379-1386.

[22.] Gasik, M.I., Gorobets, A.P., Vukelich, S.B. et al. (1981) Study of nonmetallic inclusion nature in bearing metal treated by magnesium. In: Metallurgy and coke chemistry. Issue 74. Kiev: Tekhnika.

[23.] Gasik, M.I., Salnikov, A.S. (2007) X-ray spectral microanalysis of heterophase globular and streak oxide inclusions in steel ShKh15SG-V. Metallurg. i Gornorudn. Promyshlennost, 6, 31-37.

A.I. PANCHENKO (1), I.N. LOGOZINSKY (1), A.S. SALNIKOV (1), S.L. MAZURUK (1), S.A. KASIAN (1), S.S. KAZAKOV (1), L.M. SKRIPKA (1), M.I. GASIK (2), A.P. GOROBETS (2) and O.N. SEZONENKO (1)

(1) OJSC << Dneprospetsstal >>, Zaporozhie, Ukraine

(2) National Metallurgical Academy of Ukraine, Dnepropetrovsk, Ukraine
Table 1. Chemical composition of analyzed phases (Figure 2) [1]

Phase Weight share of elements, %

 Mg Al Ca Si

1 11.34 24.89 0.52 --
2 0.33 22.41 18.71 --
3 -- 5.57 37.62 --
4 -- 1.76 23.54 0.21

Phase Weight share of elements, %

 Cr Mn Fe O

1 0.26 0.32 25.37 37.29
2 0.36 -- 23.63 34.56
3 0.78 -- 27.76 28.28
4 0.32 S 16.26 17.28 40.63

Table 2. Chemical composition of ShKh15SG-V steel at stages of melting
and ladle treatment in ladle-furnace and ladle vacuumator

Technology stage Weight share of elements, %

 C Mn Si Cr

Before tapping from ASF * 0.75 0.15 0.13 1.200

At beginning of treatment 0.95 0.17 0.20 0.014
in ladle-furnace
(after addition of FS65)

At end of treatment in 0.99 1.00 0.48 1.430
ladle-furnace

At end of treatment in 0.99 1.00 0.48 1.430
vacuumator

Technology stage Weight share of elements, %

 P S Al Ca, ppm

Before tapping from ASF * 0.011 0.045 0.004 4.0

At beginning of treatment 0.018 0.040 0.040 5.0
in ladle-furnace
(after addition of FS65)

At end of treatment in 0.014 0.009 0.045 13.8
ladle-furnace

At end of treatment in 0.014 0.005 0.033 10.6
vacuumator

* Arc steel furnace.

Table 3. Chemical composition of slag at different stages of
ShKh15SG-V steel production technology

 Period of melting Weight share of elements, %

 CaO MgO [Al.sub.2] Si FeO
 [O.sub.3] [O.sub.3]

Before tapping from ASF 45 15 3 7 2.5

At beginning of treatment 50 9 13 8 1.0
in ladle-furnace
(after addition of FS65)

At end of treatment in 55 7 9 10 0.3
ladle-furnace

At end of treatment in 55 7 10 15 0.3
vacuumator

Table 4. Chemical composition of ferroalloys used in performance of
experimental melts of ShKh15SG-V steel

 Weight share of elements, %

Material C Mn Si P S Ca

MnS25 0.32 71.3 25.0 0.075 0.018 0.010
FMn78 6.30 79.1 1.8 0.230 0.020 0.022
FS65 0.08 0.27 64.0 0.023 0.003 0.420

 Weight share of elements, %

Material Ni Mo Ti Al Cu As

MnS25 0.020 0.023 0.19 0.083 0.016 0.016
FMn78 0.062 0.025 0.08 0.086 0.027 0.030
FS65 0.100 0.036 0.20 2.00 0.083 0.020

 Weight share of elements, %

Material Pb Sn Zn [O] [N] [H],
 ppm
MnS25 0.012 0.0013 0.033 0.023 0.001 15
FMn78 0.014 0.0015 0.035 0.130 0.040 46
FS65 0.015 0.0009 0.037 0.047 0.004 14

Table 5. Technological conditions of deoxidation and alloying of
ShKh15SG-V steel of experimental melts with application of MnS25

 Option Quantity DSP-50 [Ca], Ladle
 of melts ppm

 1 1 Al 4.0 SiMn; Al
 2 4 Al 3.5 SiMn; FS
 3 1 SiMn 3.0 Al
 4 2 -- 4.0 Al
 5 7 FS 4.7 SiMn; FS; Al
 Valid -- FS 4.0 Al
technology

 Option Ladle-furnace [Ca], IA [Ca], [Ca], ppm,
 ppm ppm in finished
 metal

 1 FS; Al 12.0 Al 13.0 10.0
 2 Al 6.8 Al 6.8 6.7
 3 FS; Al 25.0 Al 20.0 10.0
 4 SiMn; FS; Al 10.0 Al -- 8.5
 5 FS; Al 7.3 Al 9.0 7.1
 Valid FS; FMn; Al 13.8 Al 10.6 9.6
technology

 Option % of Yield of
 drop-outs efficient
 O + S + Gl metal

 1 40.9 0
 2 31.3 57
 3 0 100
 4 6.7 100
 5 9.2 89
 Valid 15.9 64
technology

Table 6. Change of chemical composition of slag at stages of ladle
treatment of ShKh15SG-V steel according to option 5

 Weight share of components, %
Melt Sample
number number CaO MgO [Al.sub.2] Si
 [O.sub.3] [O.sub.3]

V15656 1 46.83 18.20 16.4 15.70
 2 59.95 6.36 10.0 17.44
 3 53.75 7.00 12.8 17.22
 4 50.83 13.40 10.2 17.20
V15710 1 48.20 7.60 9.8 15.40
 2 53.00 8.00 7.6 15.30
 3 53.00 9.40 8.9 16.30
 4 50.40 10.40 13.2 15.40
V15775 1 57.50 10.70 16.4 14.77
 2 >61.80 6.82 14.2 15.30
 3 55.43 11.91 15.9 15.82
 4 53.09 11.24 16.5 15.10

 Weight share of components, %
Melt Sample
number number MnO FeO S CaF2

V15656 1 0.37 <0.15 0.47 8.72
 2 0.30 0.92 0.12 13.55
 3 <0.30 0.54 0.09 9.68
 4 <0.30 <0.15 0.20 6.00
V15710 1 <0.30 0.84 0.51 12.20
 2 <0.30 0.78 0.24 15.67
 3 <0.30 0.15 -- --
 4 <0.30 <0.15 0.71 7.74
V15775 1 0.54 0.15 0.82 8.13
 2 0.50 1.15 0.24 7.94
 3 0.48 <0.15 0.14 8.72
 4 0.46 <0.15 0.49 8.72

Note. Sample 1--after treatment of metal with SFM in ladle; sample
2--in ladle-furnace after renovation of slag; sample 3--at end of
treatment in ladle-furnace; sample 4--after degassing.

Table 7. Content of elements in course of experimental melts of
ShKh15SG-V steel

 Mn, %
Melt
number Furnace Ladle-furnace Vacuumator Ladle
 at
 tapping 1 * 2 * 3 *

Option 1

V14608 0.09 0.84 1.06 1.07 1.06 1.04

Option 2

V14618 0.12 1.04 1.09 -- 1.04 1.05
V14680 0.13 1.07 1.05 -- 1.05 1.00
V14690 0.12 1.04 1.03 -- 1.00 1.01
V14859 0.11 1.04 1.13 -- 1.10 1.08
Average 0.12 1.05 1.07 -- 1.05 1.04

Option 3

V15114 0.13 0.88 1.13 -- 1.07 1.07

Option 4

V15294 0.14 0.17 1.04 -- 1.01 0.99
V15678 0.09 0.99 1.06 -- -- 1.00
Average 0.12 0.58 1.05 -- 1.01 0.99

Option 5

V15155 0.16 1.07 1.07 1.04 1.03 1.01
V15656 0.17 1.08 1.07 1.06 1.05 1.06
V15710 0.13 1.03 1.01 -- 1.04 1.03
V15743 0.09 1.02 1.02 -- -- 0.96
V15744 0.13 1.03 1.02 -- -- 0.98
V15775 0.09 1.02 1.01 1.02 -- 0.97
V15788 0.14 1.01 1.00 -- 0.94 0.93
Average 0.13 1.04 1.03 1.04 1.02 0.99

 Si, %
Melt
number Ladle-furnace Vacuumator Ladle

 1 * 2 * 3 *

Option 1

V14608 0.20 0.19 0.35 0.46 0.45

Option 2

V14618 0.51 0.45 -- 0.48 0.49
V14680 0.56 0.50 -- 0.50 0.50
V14690 0.51 0.43 -- 0.50 0.51
V14859 0.51 0.56 -- 0.57 0.57
Average 0.52 0.49 -- 0.51 0.52

Option 3

V15114 0.15 0.60 -- 0.58 0.57

Option 4

V15294 0.09 0.42 -- 0.46 0.44
V15678 0.32 0.44 -- -- 0.44
Average 0.21 0.43 -- 0.46 0.44

Option 5

V15155 0.46 0.44 0.46 0.47 0.48
V15656 0.49 0.47 0.46 0.50 0.51
V15710 0.49 0.46 -- 0.48 0.48
V15743 0.67 0.56 -- -- 0.56
V15744 0.43 0.50 -- -- 0.51
V15775 0.63 0.61 0.59 -- 0.60
V15788 0.44 0.47 -- 0.48 0.45
Average 0.52 0.50 0.50 0.48 0.51

 Ca, ppm
Melt
number Furnace Ladle-furnace Vacuumator Ladle
 at
 tapping 1 * 2 * 3 *

Option 1

V14608 4 6 6 12 13 10

Option 2

V14618 4 11 5 -- 5 7
V14680 3 7 7 -- 5 4
V14690 4 5 4 -- 7 7
V14859 3 7 11 -- 10 9
Average 3.5 7.5 6.8 -- 6.8 6.7

Option 3

V15114 3 6 25 -- 20 10

Option 4

V15294 -- -- -- -- -- 9
V15678 4 4 10 -- -- 8
Average 4 4 10 -- -- 8.5

Option 5

V15155 3 9 5 10 8 7
V15656 8 5 6 6 8 10
V15710 4.9 5 6 -- 6 6
V15743 6 5 5 -- -- 5
V15744 4 6 8 -- -- 9
V15775 4 5 6 6 -- 6
V15788 4 5 12 -- 14 7
Average 4.7 5.7 6.9 7.3 9 7.1

Melt Al, %, S, %, [O.sub.2]/
number ladle ladle [N.sub.2],
 ppm, rolled
 stock

Option 1

V14608 0.024 0.002 8/80

Option 2

V14618 0.025 0.003 8/70
V14680 0.025 0.003 8/70
V14690 0.029 0.006 10/70
V14859 0.034 0.005 8/70
Average 0.028 0.004 8.5/70

Option 3

V15114 0.033 0.003 10/90

Option 4

V15294 0.028 0.003 9/70
V15678 0.022 0.007 9/80
Average 0.025 0.006 9/75

Option 5

V15155 0.041 0.004 10/80
V15656 0.030 0.003 9/70
V15710 0.028 0.004 10/80
V15743 0.029 0.003 10/80
V15744 0.022 0.003 9/80
V15775 0,024 0,004 9/80
V15788 0,024 0,005 9/90
Average 0.028 0.004 9.4/80

* Sample numbers.

Table 8. Results of metal quality assessment of experimental melts of
ShKh15SG-V steel according to scales of GOST 801--78

 Number, pcs
Technology Type of Yield
 option Group control Lot Speci- of
 mens efficient
 metal, %

 1 I Delivery 1 11 0
 Investigation 1 11 0
 [SIGMA] 1 22 0

 2 I Delivery 3 25 33
 Investigation 1 8 0
 [SIGMA] 4 33 25
 V Delivery 1 12 100
 Investigation 2 22 100
 [SIGMA] 3 34 3
 I+V [SIGMA] 7 67 57

 3 V Investigation 1 8 100

 4 I Delivery 1 6 100
 V Same 1 9 100
 I+V [SIGMA] 2 15 100

 5 I Investigation 1 12 0
 II Delivery 2 24 100
 III Same 1 6 100
 V >> 5 45 100
 I+II+III+V -- 9 87 89

 Valid I+II+III+V Delivery 309 3538 64
technology

 Kind of non-metal
 inclusions

 O
Technology Type of
 option Group control Specimens
 Average with drop-out
 number
 pcs %

 1 I Delivery 2.0 0 0
 Investigation 1.8 1 9.1
 [SIGMA] 1.9 1 4.5

 2 I Delivery 2.2 9 36.0
 Investigation 2.4 3 37.5
 [SIGMA] 2.3 12 36.4
 V Delivery 2.6 0 0
 Investigation 2.7 1 4.5
 [SIGMA] 2.65 1 2.9
 I+V [SIGMA] -- 13 19.4

 3 V Investigation 1.9 0 0

 4 I Delivery 1.8 0 0
 V Same 2.7 1 11.1
 I+V [SIGMA] -- 1 6.7

 5 I Investigation 2.0 1 8.3
 II Delivery 1.95 0 0
 III Same 2.1 0 0
 V >> 2.45 2 4.4
 I+II+III+V -- -- 3 3.4

 Valid I+II+III+V Delivery -- 160 4.5
technology

 Kind of non-metal
 inclusions

 S
Technology Type of
 option Group control Specimens
 Average with drop-out
 number
 pcs %

 1 I Delivery 2.0 0 0
 Investigation 1.9 0 0
 [SIGMA] 1.95 0 0

 2 I Delivery 1.8 0 0
 Investigation 2.0 0 0
 [SIGMA] 1.9 0 0
 V Delivery 2.3 0 0
 Investigation 2.2 0 0
 [SIGMA] 2.25 0 0
 I+V [SIGMA] -- 0 0

 3 V Investigation 2.1 0 0

 4 I Delivery 1.5 0 0
 V Same 2.5 0 0
 I+V [SIGMA] -- 0 0

 5 I Investigation 2.0 0 0
 II Delivery 1.55 0 0
 III Same 2.0 0 0
 V >> 2.3 0 0
 I+II+III+V -- -- 0 0

 Valid I+II+III+V Delivery -- 5 0.1
technology

 Kind of non-metal
 inclusions

 G
Technology Type of
 option Group control Specimens
 Average with drop-out
 number
 pcs %

 1 I Delivery 3.3 5 45.5
 Investigation 2.5 3 27.3
 [SIGMA] 2.9 8 36.4

 2 I Delivery 1.9 6 24.0
 Investigation 1.7 0 0
 [SIGMA] 1.8 6 18.2
 V Delivery 2.3 1 8.3
 Investigation 1.8 1 4.5
 [SIGMA] 2.05 2 5.9
 I+V [SIGMA] -- 8 11.9

 3 V Investigation 2.4 0 0

 4 I Delivery 1.5 0 0
 V Same 2.3 0 0
 I+V [SIGMA] -- 0 0

 5 I Investigation 1.9 2 16.7
 II Delivery 2.0 1 4.2
 III Same 1.7 0 0
 V >> 2.35 2 4.4
 I+II+III+V -- -- 5 5.7

 Valid I+II+III+V Delivery -- 398 11.2
technology

 Kind of non-metal
 inclusions

 O + S + G
Technology Type of
 option Group control
 pcs %

 1 I Delivery 5 45.5
 Investigation 4 36.4
 [SIGMA] 9 40.9

 2 I Delivery 15 60.0
 Investigation 3 37.5
 [SIGMA] 18 54.5
 V Delivery 1 8.3
 Investigation 2 9.0
 [SIGMA] 3 8.8
 I+V [SIGMA] 21 31.3

 3 V Investigation 0 0

 4 I Delivery 0 0
 V Same 1 11.5
 I+V [SIGMA] 1 6.7

 5 I Investigation 3 25.0
 II Delivery 1 4.2
 III Same 0 0
 V >> 4 8.9
 I+II+III+V -- 8 9.2

 Valid I+II+III+V Delivery 563 15.9
technology

Note. 1. Here O--oxides; S--sulfides; G--globules. 2. Normative
requirements of GOST 801--78, number, not more than:

 O S G

I, II groups (profile up to 40 mm) 2.0 2.0 2.0
III, IV groups (profile up to 80 mm) 2.5 2.5 2.5
V groups (profile up to 80 mm) 3.0 3.0

Figure 6. Characteristics of process of ShKh15SG-V steel alloying
and deoxidating using FMnS25 ferromanganese silicon: 1--at tapping
from DSP-60; 2--before treatment in ladle-furnace; 3--at end of
treatment in ladle-furnace; 4--after degassing

 ([J.sub.Ca]/ ([J.sub.Mg]/
 [J.sub.Al]) * [J.sub.Al]) *
 [10.sup.3] [10.sup.3]

Valid technology with 441 458
treatment of metal using
synthetic lime-alumina
slag

Treatment of metal by 136 1259
magnesium-containing
hardener in combination
with synthetic slag
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Title Annotation:ELECTROMETALLURGY OF STEEL AND FERROALLOYS
Author:Panchenko, A.I.; Logozinsky, I.N.; Salnikov, A.S.; Mazuruk, S.L.; Kasian, S.A.; Kazakov, S.S.; Skrip
Publication:Advances in Electrometallurgy
Article Type:Report
Date:Jul 1, 2008
Words:7389
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