effectiveness of barium-bearing ferroalloys in steel smelting

ISSN 0967�0912, Steel in Translation, 2013, Vol. 43, No. 8, pp. 511–514. © Allerton Press, Inc., 2013.Original Russian Text © V.A. Golubtsov, I.V. Ryabchikov, K.I. Yarovoi, V.G. Mizin, V.G. Milyuts, E.Yu. Levagin, 2013, published in “Stal’,” 2013, No. 8, pp. 32–35.

511

It is clear from the theory and practice of metallur�gical production that the refining and modification ofsteel is significantly more effective if binary alloys arereplaced by ternary and more complex ferroalloys [1].

The only Russian producer of fused multicompo�nent ferroalloys is OOO NPP Tekhnologiya. Thiscompany is introducing the production of fast�cooledmodifiers with microcrystalline structure, containingcalcium, barium, and other active elements (Table 1).The modifiers are practically free of chemical hetero�geneity. The gas content is 2–3 times greater than inanalogous alloys with a macrocrystalline structure castin molds [3].

The use of microcrystalline modifiers at variouslarge enterprises permits improvement in the quality ofsteel castings and pressure�treated metal. In the steel�casting shop at OAO Altaivagonzavod, the productionof 20ГФЛ steel with OOO NPP Tekhnologiya modifi�

ers has been introduced. The plant produces railroad cast�ings: lateral frames and sprung beams. INSTEEL® 1.3or INSTEEL® 11 is used to modify the metal in ladletreatment.

The use of INSTEEL® 1.3 modifier more than tri�ples the calcium assimilation of the metal (from 5.0 to15.7%), with a more stable calcium content in themetal. At the same time, there is no slag splashing fromthe ladle during the introduction of powder wire. Theaccelerated solution of the microcrystalline modifierincreases the rate of wire introduction in the ladle from6 to 25 m/min. All the mechanical characteristics ofthe experimental metal are better than for melts mod�ified by ferrocalcium. Thus, KCV–60 is increased by29.0% (Table 2). The rejection rate of the castings isconsiderably reduced.

Further improvements are seen on usingINSTEEL® 11 modifier, which also contains zirco�

Effectiveness of Barium�Bearing Ferroalloys in Steel SmeltingV. A. Golubtsova, I. V. Ryabchikova, K. I. Yarovoia, V. G. Mizin, V. G. Milyutsb, and E. Yu. Levaginb

aOOO NPP Tekhnologiya, Chelyabinsk, RussiabPrometei Central Research Institute, St. Petersburg, Russia

Abstract—The influence of barium�bearing ferroalloys on the mechanical properties of cast and deformedsteel is studied. Such ferroalloys greatly reduce the metal’s content of gases and nonmetallic inclusions,increase the impact strength of steel for railroad castings, and improve the plasticity of high�strength ship�building steel.

Keywords: complex ferroalloys, microcrystalline modifiers, calcium, barium, railroad castings, impactstrength, high�strength steel, nonmetallic inclusions, plasticity

DOI: 10.3103/S0967091213080044

Table 1. Chemical composition of modifiers, wt % (Technical Specifications TU 082�002�7264889–12)*

Microcrystalline modifier Ca Ba Rare�earth elements Al Ti Si

INSTEEL® 1.3 5–8 15–20 – Up to 3.0 – 45–55

INSTEEL® 3.2 9–12 3–6 7–9 6–8 – 40–50

INSTEEL® 3.3 6–8 12–15 9–12 6–8 – 45–55

INSTEEL® 4.4 8–10 7–10 – Up to 3.0 4–6 45–55

INSTEEL® 5.1 10–12 – 10–12 3–4 – 45–55

INSTEEL® 5.2 5–7 – 18–22 3–6 – 45–55

INSTEEL® 6.1 12–14 7–10 – 5–8 – 40–50

INSTEEL® 7 10–14 5–8 5–8 Up to 2.0 1–12 40–50

INSTEEL® 11** 6–10 6–10 – Up to 2.5 – 55–65

* All the modifiers contain up to 1.5 wt % Mg; the balance is Fe.** With 6–10 wt % Zr.

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STEEL IN TRANSLATION Vol. 43 No. 8 2013

GOLUBTSOV et al.

nium. The calcium assimilation is 17.2%. The impactstrength KCU–60 and KCV–60 is increased by 18.7 and21.2%, respectively. Reduction and microalloying ofthe steel by zirconium evidently facilitates the forma�tion of small carbonitrides in the metal and consider�ably reduces the primary grain size and dispersionalgrain�boundary hardening of the metal. Nitride for�mation begins with the deposition of ZrN and thenVN, as shown in [3]. As a result, the nitrogen concen�tration in solution falls practically to zero at the end ofsolidification. That prevents the appearance of AlNphases, roles out local aggregation of the nitride inclu�sions, and ultimately improves the mechanical char�acteristics of the metal.

Modification with ferrocalcium to produce high�strength steel does not ensure the required plasticity ofthe metal or eliminate microcrack formation on ingotdeformation. The use of INSTEEL® 5.1 modifier withcalcium and rare�earth metals at OOO OMZ�Spetsstal’ increases the crack resistance of (10–25)�tingots in deformation thanks to change in the compo�sition of the nonmetallic inclusions and the formationof cerium and lanthanum oxysulfides [4].

The benefits of barium�bearing ferroalloys are evi�dent in the production of rail steel [5, 6] and wheelsteel [7, 8]. On that basis, industrial trials withINSTEEL® 3.2 modifier (Table 1) are undertaken.The basic steel is produced in a DSP�120 arc furnaceand then refined and vacuum�treated in a 60�t ladle, inaccordance with current technology. During ladletreatment some of the ferrocalcium is replaced by

INSTEEL® 3.2 or INSTEEL® 5.1 modifier. Table 3presents the calculated and actual concentrations ofcalcium and cerium in the metal.

It is evident from Table 3 that the barium�bearingmodifier practically doubles the residual cerium con�tent and its degree of assimilation in the metal (cases 2and 3). Introducing barium has practically no effect onthe calcium assimilation. The barium also improvesthe mechanical characteristics of the high�strengthsteel; increasing the quantity of barium�bearing mod�ifier further improves the mechanical characteristics ofthe steel (Table 4, case 3). Modification with bariumincreases the constriction in the Z direction by 9.7%,on average.

To explain the influence of barium on the steelproperties, we must consider the physicochemicalaspects of the relation between alkaline�earth ele�ments and iron. Solutions of those elements in liquidiron are far from ideal: specifically, mutual repulsionoccurs between the atoms of these elements. Experi�mental determination of the mixing enthalpy of Fewith an alkaline�earth element (Ca, Sr, or Ba) isimpossible because the components are completelyimmiscible in the liquid state. Accordingly, to assessthe integral enthalpies of formation (ΔH) of liquid cal�cium or barium alloys with iron, the binary systemsFe–Ca and Fe–Ba are regarded as components of theternary systems Fe–Si–Ca and Fe–Si–Ba [9]. Withincrease in the number of the element from calcium tobarium, the solubility in liquid iron declines [10]. Theenthalpy of alloy formation between Fe and an alka�

Table 2. Mechanical characteristics of experimental metal (with INSTEEL® additives) and traditional steel (with FeCa)

Metal Calcium assimilation

Mechanical characteristics

relative elongation δ, %

relative constric�tion ψ, %

impact strength KCU–60, J/cm2

impact strength KCV–60, J/cm2

According to the OST 32.183–2001 standard (NV ZhT TM 02–98) ≥18 ≥25 ≥24.5 ≥16.7

FeCa 5.0

INSTEEL® 1.3 15.7

INSTEEL® 11 17.2

19–3227.3

�� 42–5346.0

�� 18.2–65.047.4

�� 9.1–25.017.7

��

20–3128.3

�� 44–5548.1

�� 35.8–80.662.0

�� 15.6–25.618.9

��

18–32.026.3

�� 39–5347.8

�� 51.3–106.373.6

�� 16.9–35.022.9

��

Table 3. Calcium/cerium content and assimilation in experimental metal

Modification of metal Calculated content introduced with modifier, ppm

Content in metal, ppm Assimilation, %

Case 1: FeCa : INSTEEL® 5.1 = 1 : 1 218/54.8 21.2/13.8 9.5/26.5




EFFECTIVENESS OF BARIUM�BEARING FERROALLOYS IN STEEL SMELTING 513

line�earth element increases in the same sequence.Thus, the maximum heat of reaction of Ca, Sr, and Bawith liquid iron (calculated by means of a cellularmodel) is 128, 185, and 212 kJ/g�at, respectively,according to [11]. Calculation by the Gromakovmethod gives the maximum value of ΔH at 1700 Kwhen Ca and Ba dissolve in iron: 130 and 300 kJ/g�at,respectively [9]; according to the Kohler equation, thecorresponding values are 400 and 1000 kJ/g�at. Forlow Ca and Ba concentrations in the steel, the Kohlerequation gives more reliable results for ΔH [9]. Thus,among the alkaline�earth elements, barium has a dis�tinctive combination of properties: minimum solubil�ity in liquid iron; high boiling point (1637°C), exceed�ing the steel temperature; and minimum enthalpy ofsolution in iron.

When barium�bearing ferroalloy is introduced inliquid steel, the iron and silicon present in the ferroal�loy dissolve, while the insoluble barium, with relativelyhigh density (3.3 g/cm3), interacts strongly with theiron and greatly perturbs the structure of the liquidsteel; the system enters a state of extreme disequilib�rium. The iron vigorously repels the barium from themelt; as a result, it is strongly dispersed (to the level ofnanoparticles and individual atoms). Under the activeof the repulsive forces, the relatively large bariumatoms (rBa = 0.217 nm) are forced to penetrate throughdense rows of heavy and smaller iron atoms (rFe =0.124 nm) [12]. This is associated with powerfulatomic interaction, whose effect is felt throughout themelt. Accordingly, ladle treatment of ferrocarbon meltby barium�bearing ferroalloys may be classified asnanomodification of the steel with barium.

Barium is a strong surfactant and, in steel casting,is able to protect its surface from the air, on account ofmultiple increase in its surface concentration [13].The intense reaction of barium with iron and its greatdispersion facilitate deep reduction of the metal andcoagulation of oxide compounds with barium, on theone hand [7]; and the formation of tiny barium�bear�ing compounds, on the other. The removal of the most

harmful high�alumina inclusions from the steel isfacilitated by the large heat of formation of bariumaluminate BaO ⋅ Al2O3 from oxides, which is almost anorder of magnitude greater than that for CaO ⋅ Al2O3[15]; and by the considerable reduction in wettingangle of Al2O3 by liquid steel in the presence of barium[13]. Industrial tests indicate that, in the modificationof rail steel by silicobarium, barium suppresses thedeposition of Al2O3�rich inclusions [15]. In the treat�ment of 45X steel by silicobarium, inclusions ofcorundum and barium sulfide emerge from the volumeof the melt at the surface [16]. With its distinctive set ofproperties, barium is able to rapidly condition thewhole mass of metal. Experiments show that thereduction of steel by barium is faster than for alumi�num, which is highly soluble in iron [17].

We know that more thorough removal of impuritiesfrom the melt results in greater supercooling. Barium,which serves as a getter in vacuum engineering,ensures great reduction in the gas content of liquidsteel. The rapid formation of barium�bearing inclu�sions and their removal from the metal may be attrib�uted to the high reactivity of barium and the formationof fusible oxides and eutectics [14]. Accordingly, theremoval of gases and nonmetallic inclusions from steelby barium increases the supercooling and delays itstransition to the solid state, with the formation of non�equilibrium structures. In prolonged holding, thenonequilibrium structures relax, with improvement inthe metal’s physicomechanical properties.

Our interpretation of barium’s influence on steelalso explains the significant (6–7%) increase in theplastic properties of rail observed two months aftertheir manufacture from barium�modified steel [6].

CONCLUSIONS

(1) We have shown that modification of steel withbarium�bearing ferroalloys has the following conse�quences:

Table 4. Influence of modification on mechanical characteristics of the metal*

Modification of metal Relative elongation, %

Relative constriction, %

Impact strength KCV–20, J/cm2

Relative constriction in the Z direction

Modification with FeCa

Case 1: FeCa : INSTEEL® 5.1 = 1 : 1



* Sample from top/bottom of sheet.

17.817.7�� 66.6

67.5�� 208.6

208.6�� 56.2

60.2��

17.917.8�� 65.9

65.5�� 197.2

197.6�� 57.5

56.4��

18.118.1�� 66.2

66.8�� 202.4

204.8�� 57.9

56.2��

19.519.8�� 67.5

69.0�� 208.0

215.0�� 61.3

63.5��

514


GOLUBTSOV et al.

⎯effective removal of gases, corundum, and high�alumina inclusions from the metal;

⎯increase in the impact strength of cast 20ГФЛrail steel at –60°C by ~30%;

⎯increase in plasticity of high�strength shipbuild�ing steel in the Z direction by ~10%.

(2) The very effective treatment of steel by barium�bearing ferroalloys may be attributed to the distinctivephysical and physicochemical properties of barium.

REFERENCES

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2. Ryabchikov, I.V., Shub, L.G., Usmanov, R.G., et al.,Improving the performance of modifiers by improvingtheir chemical composition and structure, Stal’, 2010,no. 1, pp. 58–59.

3. Volkov, A.E., Petrovskii, V.A., and Borisov, V.T., Localaggregation of nonmetallic inclusions in dendritic cells onelectrosteel solidification, Stal’, 1987, no. 4, pp. 23–27.

4. Golubtsov, V.A., Milyuts, V.G., and Tsukanov, V.V.,Influence of modification on the content of nonmetal�lic inclusions in shipbuilding steel, Tyazh. Mashinostr.,2013, no. 1, pp. 60–9.

5. Fomin, N.A., Vorozhishchev, V.I., Monastyrskaya, V.Ya.,et al., Production of high�purity rail steel, Stal’, 1991,no. 3, pp. 27–30.

6. Deryabin, A.A., Pavlov, V.V., Mogil’nyi, et al., Effec�tiveness of nanomodification of rail steel with barium,Steel Transl., 2007, vol. 37, no. 11, pp. 966–973.

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modifiers, Steel Transl., 2009, vol. 39, no. 12,pp. 1078–1083.

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10. Ageev, Yu.A. and Archugov, S.A., Solubility of alkaline�earth metals in liquid iron and its alloys, Zh. Fiz. Khim.,1985, vol. 59, no. 4, pp. 838–841.

11. Dubrovin, A.S., Metallurgiya spetsial’nykh splavov(Metallurgy of Special Alloys), Chelyabinsk: Izd.YuUrGU, 2002.

12. Emsley, J., The Elements, Clarendon: Oxford Univer�sity Press, 1998, 3rd ed.

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16. Zherebtsov, D.A., Chumanov, I.V., and Goikhen�berg, Yu.N., Refining of 45X steel by ferrosilicobarium,Elektrometallurgiya, 2012, no. 5, pp. 20–25.

17. Shi, Y., Chen, B., Fu, J., and El Gammal, T., Experi�mental study on deoxidation of barium and bariumalloy, J. Mater. Sci. Technol., 1999, vol. 15, no. 5,pp. 400–404.

Translated by Bernard Gilbert

effectiveness of barium-bearing ferroalloys in steel smelting

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