w Application of Barium-bearing Alloys In Steelmaking

ISIJ International, Vol. 39 (1999), No. 7, pp. 625-636

Revie wApplication of Barium-bearing Alloys In Steelmaking

Kusuhiro MUKAIand Oiyong HANDepartment of Materials Science and Engineering, Faculty of Engineering,Tobata-ku, Kitakyushu, Fukuoka-ken, 804 Japan.

(Received on February 2. 1999.• accepted in final form on 14pri/ 8.

Kyushu

1999)

Institute of Technology, Sensui-cho,

Basedon the understanding of the physico-chemical properties of alkaline earth metals, an overview onthe investigation of application of Ba-bearing alloys in steel is given in the paper. As calcium it is, bariumhas a strong affinity for oxygen and sulfur in steel; barium can also modify the inclusions in the steel. Thebarium-bearing inclusions easily float out from steel. Theresidual barium-bearing inclusions exist in spherical

complexaluminates and randomly distribute in the steel. Themechanical properties such as fatigue, transverseimpact toughness and anisotropic properties of steels treated with barium-bearing alloys are improved. Theeffect of calcium and barium on microstructure of steel is discussed.

Somecharacteristics of production of barium-bearing alloys are also discussed,

KEYWORDS:barium-bearing alloys; deoxidation; inclusion modification; mechanical properties.

of steel in Russia and other countries (Table l).l. Introduction The results of research and application show that

At present the main goal ofsteelmaking industry is to treatrnent of steel with barium-bearing a]loys can de-

improve the properties of steel products. Removaland crease the amount of aluminum used; the deoxidation

improvement of the composition and morphology of products easily float out from the liquid steel; the

inclusions and, accordingly, selection of the proper characteristics of remained incluslons in the steel aredeoxldizer and modifying agent for inclusions are one improved; accordingly, the mechanical properties areof the important measuresfor improvementof properties improved.of steel. Barium-bearing alloys are used for treatment

Tabte l. Composition of Ba-bearing anoys and steels treated with Ba-bearing anoys.

Pre-deoxi-dation

%

Comosition of Ba bearin allo, %

SteelsCa Mg Ba Ai Si RE Fe

Additionof alloy Ref

%AAR201gradeBibid

Lowalloy

Fe-Ni alloy

SWRH62A12Cr*MoVpipe

steel

30CrNiMoSilicon free

HSLA40VPRail

30CrNiWAISI 1518,

35CrNilMo2035MnSiCrPRail

35Mn2Carbon20MnPHigh CrNi17MnSi09Mn2V6API X70

Al 0,17Al 0,35

Al 0.35

SiMn1.3

A1 0.l

15.3210.2

1724.017.07.2

l0.3

15

3-15

105-30

4.5

13.4

53.2

lO

lO

3lO5.5

2016162.2

l0.5

l5-20

52-15

4O~L9

6.24

l .5

0.5

2.5

2.5

l .5

1.5

0.5

15.129.35

13

5,2

16,0

25 O10,4

13O. I-5

9.5

0.5-202.3

1.87

O. l3.5

lO

25,2

0,6

22

1717

3617.5

14-18

1918

21165-15

13

10-50

46.60.5

9820

25.3

4688

13

13

2.0

55.8440.7 lBal ance50.348.045.938.541Balance

Balance

39.712.2

3639.7

50

3040405050474758.048.0

50/60

5-15

16.5

3-5031.2

3.7

5-7

9.6018.2

Balance5-lO

4.2Balance18.8

Balance

Balance3.3

Balance

BalanceBalanceBalanceBalanceBalanceBalance

BalanceBalanceBalance

0.430.2

0.2

0,05

O. 1~.4

0.3~.5

0.4~.6

O. I~).6

O. 130.015-0.023

2222234

56789lOll

1213

1415161718192021

625 @1999 ISIJ

ISIJ International, Vol. 39 (1999). No. 7

Table 2. Physico-chemlcal propertles of Ca, Ba, Mg, Al and Ceas pure metal and In lron melt.

Element, Atomic Atomic radius Densityweight nm g/ml

Ca 40.06

Ba 137.33

Mg 24.305AI 26.98

Ce 140. 12

0.2230,2780,172O, 1430,270

Solubility inElement, Boiling

iron (1600'Ctemp. 'C pi = O. IMPa)

Ca 1484

Ba1625-1637

Mg I090Al 2424Ce 3426

O0170.034[29]

0.0043 [30. 3sr

0.056 [3 l, 35]

Unlimitedunlimited

l .55

3.5 1l .74

2.706.67

Atomic volumecm3/ mol

29.939.24

l3.97

l0.0

20.67

aj • ao(1600•C)5.5 x l0~9 [32]

4.3 x l0~8[33]

4.09 x 10-8 [34]

l .2 x lO~[36]

6.76 x l0-Is [37]**

4.6 x l0-18 [38]***

VaporpressureMPa(1600'C)

O, 1840,0303[23]

2.038[24]

0.0043[2s]

l0-7 [261

ai ' as

(1600'C)5.9 x lO-' [32]

5.5 x 10~8[34]

2x 10~[36]

2.8 x lO~~[391

Melting point

'C839729649660798

3 2ai .ap

(1600'C)

7Ox lO]4[32]

7.76 x 10~t8 [34 35]

*The value is obtained by convertion or extrapolation of the data to Pc. = O. 1013 MPa2 3 2

~* a , a *** aCeAl Oai stands for the activity of element i .

3• ao

2. Physico-chemical Properties of Barium and OtherRelevant Elements

Alkaline earth elements have strong chemical activity.

Thephysico-chemical properties of Ca, Ba, Mg, CeandA1 are listed in Table 2. Onecan see that the affinity of

them for oxygen and sulfur decreases as follows:

Ca~: Ba>Ce>Mg> Al.

The temperature dependenceof solubility of bariumin liquid iron can be expressed as

log["/.Ba] =6.86 - 18100/T40)

Dueto the low boiling point and high vapor pressureat steelmaking temperature of calcium and magneslum,addition of calcium andmagnesiumin liquid steel inducessplash. Theboiling point of barium is higher than liquid

steel and vapor pressure of barium at 1600'C is muchless than those of calcium and magnesium.In additlon,

calcium andbarium are completely soluble in each other

at the temperature above 842'C (Fig.1).41) So barium

can reduce calcium activity and it's vapor pressure whenthey coexist in alloy.

Figure 2shows the relationship between partial pres-

sure of calcium and mole fraction of calcium of CaSi,

CaAISi and CaA1alloys at different temperatures.42) It

can be seen that silicon reduces the activity of calciumremarkably. The relationship between the partial pres-

sure of calcium of the CaSiBaor CaBaalloy and the

temperature has not been found; the energy of forma-tion of CaSi equals -88.5kJ/m0143); the energy of

formation of BaSi - I II.65 kJ/m0143)' it indicates that the

bond between silicon and barium is even stronger thanthat between silicon and calcium. Silicon promotessolution of barium in lron.

3. Effect of Barium-bearing Alloy on the Modification of

Inclusions

Researchshowsthat addition of barlum-bearing alloys

can modify the oxlde and sulfide incluslons and decreasetheir detrimental effects.

Basedon the facts that the barium-bearing inclusions

lOOo

800

ow600'x:)

h~a'UJ 400I~,E

wh200

Fig. 2.

o

~)

e)

:s

c:;

e)

~~o)

H

20 40WEIGHT

60PER

70CENT80

BARIUM90

B42-

7120

6lcp 6050

~~~,~

\\

\\\( \\

-4 5.4 174

pf&C.C.]

3350~~!~&_i_P)\~\\\

ec 2(F, ~C] x

/ ~\ \\pf \\

oca

Fig.

806020 40ATOMICPER CENTBARIUU

l. Phasediagram of Ba-Ca.41]

2000

- CQ-Si //

' /--- Ca-A[-Si {xA[= xsi} /--- Ca-Al

1900 /l,

//

/// / /

'/ / /// //''l

////'

1800/ / ll

///'/ ll ///' // /

//1700 / //./

ll / /,l /

// / /

PCa' 2Qtu / /1600 f

/ .ll. /

l'

ll//',i-~IP

//

.l

.1'

1500pCo= Iotm / l'

//.ll

//',.11'

i~oO5,l

pco ' 0,5 atm

og 7 5O,9 3

100Ba

Mole fraction of Ca, xca

Relationship between p'artial pressure of Ca. Pc*• andmole fraction of Ca, xc=*• of Ca-Si. Ca-Al-Si and

CaAl alloys at different temperatures.421

C 1999 IS[J 626

ISIJ International, Vol. 39 (1999), No. 7

had not been found in their samples of steel treated withbarium-bearing alloys, some researchers have claimedthat barium does not react with other elements, it acts

as a diluent of calcium; it decreases the vapor pressureof calcium, increases the solubility of Ca and, accord-Ing]y, increases the recovery of calcium.44~46)

Mozurovet al.47) injected AIBa alloy with argon into

ba]1-bearing steel predeoxidized with aluminum in the

ladle of capacity of 200 to 220ton. In the samplestaken 2to 3mln after injection of AIBa alloy no barium-bearing inclusions were found. The main inclusions

werehomogeneouscalcium aluminates contalning grains

of MgO•A1203spinel. The main incluslons in the

samples taken 4 to 6min after injection of AIBa alloy

contained great amount of barium (lO to 30"/*) and

MgO•A1203 spinel. By the end of the Injection of AIBaalloy, the steel contained O. I "/o Al and little Ba(O.002 "/.),

the inclusions contained muchless barium (1 .9 to 8.0 o/,).

Authors havecometo the conclusions: Minimumcontentof Inclusions in the steel product was obtained by the

injectlon of A]Ba in comparison with injection of CaSi;

barium deoxldizes and desulfurizes the steel only undercertain clrcumstances.

To clarify the effect of barium upon the modeofre'action of Ca in CaSiBadeoxidants, trials in a 25kgsc'ale and 10 to 30ton electric-furnace were carried outby Jager and Holzgruber.2) They have come to the

conclusions that l) A high efficiency of calcium deoxi-

dation can be sust'ained over a longer reaction period

whenusing CaSi alloys containing between lOwt~/* and20wt"/* Ba. 2) Increasing additions of CaSiBaresult in

avery effective reduction of B-type Al203 rich inclusions.

The CaSiBa treatment of the steel also reduces the

amountof MnSand FeSA-type Inclusions. Themajorlty

of inclusions are small and globular D-type, which arewell distributed and do not show a tendency to formstringers as is often noticed whenaluminumis used solely

for the final deoxidation.Figure 3shows the change of the content of different

oxides with elapsed-time after addition of different

alloys.48) A Iarge numberof big (200pm) and mediumsize inclusions were found in the sarnples taken im-mediateiy after the addition of 1-5 kglton of CaSiBaA1alloy In liquld steel. In these inclusions the contents ofthe oxides vary in the range: 15-60 "/* Si02, 4-25 "/. CaO,460"/o BaO.Barium wasnot found in the inclusions ofthe samples taken at Imin after addition of the abovealloy. FromFig. 3an inference wasmadethat barium-bearing inclusions flow up quickly. The inclusions in

the steel treated with barium-bearing alloy are silicates

containing small amountof calcia. Similar results werereported by Tanget al.49) Figure 4is the electron probeX-ray images of inciusions in the sample taken lOsecafter addition of CaSiBaalloy. The complex inclusions

consist of CaO•BaO•xSi02and CaO•BaO•xA1203-ySi02' Nobarium-bearing inclusions were found in the

samples taken at 3min after addition of CaSiBa orCaSiBaMgalloys. The total barium contents in these

samples are quite low, 2~l ppm. It indicates that the

big globular barium-bearing complex inclusions float upquickly.

627

ca,

ou(,IJ

xO

80

40

o

(b (c ) O102,3A4

SiCa SiBa_-~IA

A: sjCaBaAt

A•--Ar \A- C3d,

o 20

Fig. 3.

40 60 O 20 40 eo o 20 40 60

Time 5

Content of inclusions in liquid steel vs. tlme.48,

l. Si02; 2. CaO;3 BaO: 4. A1203.

Fig. 4. Electron microprobe X-ray im'ages of (Ba, Ca) silicate

Incluslons.49)

An 100-ton open hearth furnace industrial trial ontreatment of steel with barium-bearing and calcium-bearing alloys w'as done by Zaslavskii et a!.50,sl) Thecompositions of barium-bearing and calcium bearingalloys used are listed in Table 3. The deoxidation andmodification schemesof the steel with alloys are listed

in Table 4. Table 5shows the chemical analysis of the

samples taken from different heights of the 6.2-ton ingot

treated with alloys. Thesulfur decreased for l0-1 5"/~ for

schemeNo. 2 (addition of CaSi in stream) and scheme

4(addltion of CaSiBain the stream). The sulfur did notchange after addltion of BaSi in the stream (scheme3), There are not muchdifferences of oxygen contents

between dlfferent schemes. Table 6 Iists the grade

O1999 ISIJ


Table 3. Compositions of Ba bearing and Ca-bearing alloys.

Alloy Comosition, %

Si Ba Al Fe CaCaSiBaSiCaSiBa

55,l

50,654.7

0.93

26.5015. I l

l .38

2.86

l .50

805

l 169

953

31.90

1.00

l6.42

Table 4. Diffcrent deoxidation and modification schcmesfor steel 40Cr,so]

Deoxidation andmodification

Amount added,

9~(,

Addition in ladle Addition in the steel streamscheme Al CaSi CaSi BaSi CaSiBa

l234

0,02

o020,020,02

0.2

0.2

0202

0,14O.14

0.28

Table 5. Composition in different parts of ingot under different deoxidation and modification schemessol


scheme S Al

ComSi

osition,

Ca

%Ba [O]

1 0.053 0,005 0.27 0.002 trace B- 0.034

C- 0.0074

O0070.01 13

0.00420.005

D- 0.0033

2 A- 0.049

B- 0.048

D- 0.047

0,005 0.33 A - OOO5

B- 0.005

D- 0.006

trace B- 0.0029

C- 0.0036

D- OOO333 A - O053

B- 0.054

D- 0.05 1

0.005 0.3 l o002 0,0050,005

o.OO5

B- 0.0039

C- 0.0035

D- 0.0033

4 A - 0.048

B- 0.045

D- 0.046

0,005 OA3 A- O005

B- O005

D- OOO57

0,0050,0050,005

B- 0.0027

C- 0.0037

D- 0.0038Note: A, B, CandDrepresent the iongitudinal distances (percent) from the top of the ingot A: 17%; B:45%; C: 93%; D:97%.

Table 6. Assessmentof oxides and sulfides in different parts of ingot.51]


scheme

Location of sampletaken

[S] % Gradeof sulfideStringer

Gradeof oxide

globular

l

ABCD

mean

o,053 3.0

4,02,0

3,0

3,0

0.5l*.5

3.0

l .25

30303,0

3,0

3,0

2

ABCD

mean

o049o048

o,047

3035253.5

3.l

2.5

3.5

5.0

504.0

3

ABCD

mean

O0530.054

O05 l

352.5

153.0

2.7

2,0

3,0

4,53,5

3.2

4

ABCD

mean

o0480,045

0.046

3.0

2.5

2.5

3,02,7

3.0

3.0

4.04.5

3.8

Note: A, B, Cand Dare the sameas in Table 5.

Gradeof sulfide and grade of oxide stand for the assessmentof the population of sulfide and oxide, respectively.

assessment of oxides and sulfides in different parts ofingot. Wecan see that there is no remarkable differencein the inclusions in the steel treated with 4deoxidationand modification schemes. Inclusions in the stee] treated

with scheme I have both stringer and globLrlar mor-phologies. Inclusions in the steel treated with scheme

2, 3and 4are globular in shape.Figure 5shows the morphology of the sulfides in the

samples of the steels treated with 4schemes.Thesulfides

in the samplesof the steel treated with schemeI are small

MnSparticles distributing in eutectic form, and con-tacting with oxides particles which are near giobular or

@1999 ISIJ 628


Frg. 5. Micrographs of sulfides in the steels tre'ated with four

schemes.5o)

a, b, c, d-Correspond to schemes l, 2, 3and 4

Fig. 6. Micrographs of inclusions in the steels treated withfour schemes.so)

a-scheme 1; bscheme2;

scheme4

(a)

(b)

(c)

(d)

c, dscheme3; eg-

20um e+

clusters in shape.

The morphology and the electron probe analyses ofInclusions of the steels treated with four schemesareshownin Figs. 6to 8. The inclusions of the steel treatedwith scheme I are A1203 rich calcium aluminates orcalcium alumino-sllicates, MnSand (Mn,Ca)S (Figs.6(a), 7(a)). In the steel treated with scheme2the inclusionsconsist mainly of round calcium aluminates surroundedby (Ca,Mn)S or MnS(Figs. 6(b), 7(b)). In the steel

treated with scheme3inclusions consist of irregular lowcalcia or low BaOand A1203rich aluminates, someofthem are surrounded by sulfides and isolated MnS.Almost all of the inclusions in the steel treated withscheme4 are globular. Under the bright field of mi-

croscope both homogeneousor heterogeneous complexoxides were observed. Most of the sulfides precipitate

on the periphery of the complex oxides but still there

are someisolated sulfide inclusions.

The heterogeneous inclusions are agglomerativeinclusions of BaO, CaOand Al203 with (Ca, Ba) alu-

minates and sulfides. The homogeneousinclusions arecomplexaluminates consisting of CaO,BaOand A1203,the manganesefree sulfides precipitate on the peripheryof the aluminates (Figs. 8(b), 8(c)).

The results of Zaslavskii et a!.so,s 1) and other researchindicate that the ability of the alloys for modification ofInclusions increases as follows: BaSiCalcium has stronger modification ability for inclusionsthan barium. Barium strengthens the modification ability

of calcium. It would be favorable to use calciun-bariumcomplex alloy.

Zaslavskii et al.51) also counted the inclusion pop-ulation of I OOOfields of view in the steel treated with 4schemes under microscope. The size distribution ofoxide inclusions in the steel treated with 4 schemesis

shown in Fig. 9. The distribution of oxide inclusionsalong the height of the ingotsl) js shownin Fig. 10. FromFig. 9it can be seen that the volumefraction of inclusionsincreases in the steel treated with scheme2; the volumefraction of inclusions decreases in the steel treated withscheme4; the volume fraction of inclusions decreases

Fig. 7.

~1!,._..dl

Al MnCa SK* mapof elements in the inclusions.50)

a-~~d correspond to a -d in Fig. 6.

629

Ba

C 1999 ISIJ

ISIJ International, Vol, 39 (1999), No. 7

even remarkably in the stee] treated with scheme3. FromFig.10 it can be seen that the distribution of the oxideinclusions are not uniform along the height of the ingot.

The distribution of the oxide Inclusions Is relatively

Lmiform in the steel treated with scheme3 (with BaSialloy). The inclusion population is less in the top andmuchmore in the lower part of the ingots treated withscheme2and scheme4.

Fig. 9.

S

(a) (C)(b)

20urn

Fig. 8. K. mapof elements in the inclusions.50]

21c correspond to c--g in Fig. 6

o>Il,

cO*~i

:,

CG,

1:,

O

9x 10~3

I)1:lj

6x l0~3dLl fllA

r/ I 'l:fl / // l3x

l0~3

o

/~~̂~\

~~_~.~

l~

,

1.6-3,2 )6.8-13.6 )26.eh53

>3,2~ 6,e >13.6- 26.8

Inc[usi,on size,prQ

The size distributlon of oxide inclusions in the steels

lrcaled wllh 4schemes,51}

l to 4 reprcsent the schemcNo, in Table 4.

4. Effect of Barium-bearing Alloys on the MechanicalProperties of Steel

Hilty et al.i) have done one of the pioneer's work onthe application of barium as a complex deoxidizer.13.6 kg induction furnace heats of mediumcarbon steel

were melted and deoxidized with identical amounts ofaluminumandcalcium either as aluminumplus calcium-silicon, aluminumplus a calcium-siliconbarlum alloy,

or as a calcium-siliconbarium-aluminum alloy. TheA1addition was O.050/0 and that of Ca 0.0250/0. Com-position of the three different calcium alloys were listed

in Table 7. Si contents of the heats were adjusted withferrosilicon to compensatefor the varying amounts ofsiiicon added by the different calcium a]loys. In all

instances, the calcium alloys were added to the surfaceof the molten metal in the furnace as a final addition,after which the heats were held for one minute and thentapped into small ingot molds. In the case of CaSi andCaSiBaalloys, the Al addition was madejust prior tothe calcium alloys. Chemical analyses of the three heats

are tabulated in Table 8.

Typica] inclusions observed in metallographic speci-

3x'If2

:> 2xlo 2o

,,$

co11'

:,

uc

~ lxl0-2

,,

O

o

~'lll~l

ll//

il

///1jl

T///~.=.//' '~

,~ ~.-,..

-=;~f~̂~.'~

O 50 IOOHeight from the top of ingot.'f.

Fig. lO. Thedistribution ofoxide inclusions along the heightof the ingot,5 1)

l to 4represent the schemeNo, in Table 4.

Allo

CaSiCaSiBaCaSiBaAl

Table 7. Compositions of Caalloys employed for laboratory evaluation of Ba effcct ("/~). 1)

Ca29.4415.32

1O.20

Si

60.4755.8440.7 l

Al

l .44

19.00

Fe6.53

9.60

l8.20

Ba

15.129.35

DeoxidationCaSi + AlCaSiBa+ AlCaSiBaAl

Cao42

o400.42

Table 8. Composition of laboratory steels evaluating Ba effect (o/o),1]

Mno85

o83o.85

P0.01

0.01

0.01

S0.0 i60.0200.0 16

Si

0.23

0.2 lO23

Al

o035o.0380,036

(c) 1999 ISIJ 630

ISIJ International, Voi. 39 (1999), No. 7

Tablel,

9. Mechanical properties of test heats (grade Bsteel) madeby laboratory of a commerci'al foundry.

Deoxidation YP(Mpa)

TS(Mpa)

El.

(%)RA. Cha '' V**Im act (J)

(%) 21 1"C - 40"C

O68 kg/ton Al as Aluminum0.68 k /ton Al as CaSiBaAlAllo

271.O

306.8496.4502.0

25.533.5

3553

34.857.9

95l4.9

Table 10. Mechanical properties reported by foundry A (AAR201 grade steel).1]

DeoxidationYP

(Mpa)TS El. Ch "V"Im act (J)R,A,

(MPa) (9;{o) 2~, I'C - 31.7'C(%)

(mean) 324, ll .59 kg/ton Al +i 36 kg/ton CaSiTi(Std,Dev) 13,8

(mean) 337,90.23 kg/ton Al +0,45 kg/ton CaSiBaAl

(Std,Dev) 15,9

537.8 53.0 40.7 - 54.2 19.030 O13.8 4.020

558.5 52 O 54.2 -63.7 23.028.5

19.3 4O15

23.0

25.8

menscut from the ingots showedthat the CaSiBaAlwasthe most effective of a]1. Only small round inclusions

were found in the specimens.

The CaSiBaAlalloy was then tested in the laboratoryof a commercial steel foundry. In this case, it wascomparedwith plain A1 deoxidation for its effect oninclusions. Two136kg induction furnace heats of grade

Bsteel were treated with O.68kg per ton of A1 as a final

deoxidation addition. In one heat the Al was added asAl. In the other It wasaddedIn the form of the CaSiBaA1alloy. Although the sameamount of Al was added in

both instances, the resu]tant inclusions were totally

different and also were the mechanical propertles (Table9)

.

Hilty et a/.1) also summarizedthe application of the

CaSiBaAl alloy in foundry practice of eight foundries.

Three foundries have reported that the most significant

effect relating to deoxidation with this complexdeoxidizer is a marked improvement in resistance to

impact, particularly at low temperatures.Foundry A previously employeda deoxidation treat-

ment for AAR201 grade B steel consisting of 1.59kg

per ton of Al plLIS 1.36kg per ton of a CaSITi alloy.

Afterwards, they change to a practice utiiizing 0.23 kg

per ton of Al plLIS 2.3 kg per ton of a CaSiBaAlal]oy of

the composition, 10 '/* Ca, 40 o/o Si, 10 o/. Ba, and20 o/* A].

Thus, their total Al addition is 0.68kg per ton instead

of the I .59 kg formerly employedto assure freedom fromporosity and type 2inclusions. A statistical summaryoftheir experience with the two practices on AAR201 grade

Bsteel is glven in Table 10. In spite of the difference in

the Al additions, the two practices produced virtually

identical tensile ductility is accounted for by the small

increase in yie]d and tensile strength in the CaSiBaA1practice. Morenoteable is the increase in impact prop-erties with the latter practlce. Similar experience was re-

ported by this foundry for grade Csteel.

Figure ll shows the impact toughness of the casting

steels AISI 1518 (S "/o) and 35CrNilMo treated

with dlfferent deoxidation and modification agents.11)

The irnpact toughness at room temperature of casting

steel AISI 1518 treated with CaSiBaAl is 5-fold of that

of the steel treated with aluminum, 3-fold of that of the

steel treated with CaSi and 2-fold of that of the steel

treated with rare earth meta]s. The authorsll) haveindicated that impact toughness of casting steel mainly

631

120

lOO

80

~~*~h 60

~$ 40

20

o

IIlllll

AISI 1518 l 35CrNilMo

llllll

~~ ll

~~

c:9

V_~ ~

~:c,Q ~ ~_ l V~5

l:~

Fig. Il. Impact toughness of the casting steels treated withdiffei'ent deoxidation and modification agents. I I '

depends not on the grain size and inclusions but onstructure of the steel. Whenthe steel is deoxidized withAl or CaSi or Rare earth metals, the flake-shape ferrite

precipitates a]ong columnar grain boundary. While thesteel is deoxidized with CaSiBaAl, the structure of steel

is polygonal ferrite and pearlite. Difference in structureresults in different values of impact toughness.

Figure 12 shows the effects of deoxidation and mod-ification agents on the transverse Impact toughness ofslabs of different steels AISI 1518 and 35CrNlIMOatdlfferent temperatures.1 1) The transverse Impact tough-

ness of both steels is improved by the treatment withCaSiBaA1alloy.

Figure 13 shows the comparison of the longitudinal

and transverse impact toughness of 16mmthick plate ofpipe llne steel API X70 treated with CaSiBaalloy (Ca15-200/0, Ba 14-18"/., Si 55-60"/*) in mold with thoseof untreated steel at different temperatures. The valuesof transverse hTrpact toughness of the plate treated withCaSiBaalloy reach the range of values of longitudinal

impact toughness of the plate without treatment withalloys. The transverse toughness of the untreated steel is

quite low.

The tensile strength tests and the impact tests byZaslavskii et al.51) show that different deoxidation andmodification schemes in Table 4 (i,e, the different

characteristics of the inclusions) do not affect muchoneither the ductility or the longitudinal impact toughnessof the steel. The characterlstics of inciusions do affect

O1999 ISIJ

ISIJ International, Vol. 39 (1 999), No, 7

Fig. 12.

~

~

-80 -60 -40

Effects of different deoxidr

A-AISI 1518; b-35CrNi

a l40a ~~GE'~'~~:l b

150l20

o

lOO l

h\ 1oo SiCaB(lAl

50 I80 ,,

Al,

o 60-80 -60 -40 -20 O 20-20 O 20

Temperature,

'C

ion and modification agents on transverse impac'L toughness of steel slab. I l)

l Mo

8.S4

300

200

Long

Trans.

~oh

~~~s lOO

' SiCaBatreated; o untreated

lr SiCaBa treated ; untreated

-'r '~~-8- -~ ~[~::'ll JL"

/JL o

QJt'

o~It

'L

;$'1' ~~LOOO/

/

~/////A/

r __dL.

/ ~r~-/ JL~'

JL A_/~' ll 1./t k/:i /o 41A

f l~/A 41

o A /IAlo / ,~l~l:o/

schemelk, = 40A7

scheme2k = 7.32

l7

kv

~~s 4f!*,,

2,T5 5.91

2 2.28

32

l .7 3.28

5.44e38.34

l .5 0.93

5.97

l~/

o-150 -100 -50 o loo50

Temperature,

'C

Fig. 13. Comparisonorthelongitudinal and transverse impacttoughness of API x70 steel piate with those ofuntreated steel at different temperatures.2*,

remarkably on the transverse ductility and impacttoughness of the steel. Themoreglobularized the sulfide

and oxide inclusions, the higher are the values of the

transverse ductility and impact toughness of the steel.

Figure 14 shows the effect of the different deoxidationand modification schemesin Table 4on the indexes ofanisotropy of ductility and impact toughness (ratio of10ngitudinal properties to transverse properties) for steel

ATS40 Cr. The anisotropy of the properties of the stee]

treated with scheme2and scheme4decreases remark-ably, but that wlth scheme3does not decrease much.The tendency of the effect of the different alloys on theanisotropy of the properties of the steel is the sameas on the globularization of the inclusions. It meansthat

SiBa CaSi SiCaBa.

5. Effect of Calcium and Barium on Microstructure ofSteel

Astudy on influence of modification with calcium andbarium on microstructure of carbon and low alloy steels

by Kovalenko et a/.60) has cometo the following con-clusions:

At a temperature of 900-1 050'C St3sp and 45 steels

containing 0.0070/0 Ca and 0.0100/0 Ba have smaller

maximumgrains than the comparedcarbon steel, as aresult of which grain slze variation decreases. Thus, for

45 steel containing 0.007-0.0100/0 Ca the reduction in

the degree of grain size variation at a temperature of

C 1999 ISIJ 632

scheme3k = 18.34

scheme4k =5.39

l .4 ,,

Fig. 14. Effect of the different deoxidation and modificationschemes on the indcxes of anisotropy of ductile

strength and impact toughness, k~, !*-~' /*-,,.,,.51)

k~-ratio of longitudinal (5 to transverse 5;

kc-ratio of longitudinal ~to transverse tp;

k,,*.,-ratio of longitudinal ak~ to transverse ak.5. ~and ak~ are the values of elongation, reductionof area and impact toughness of the specimen,respectively;ki,,* is a integrated value obtained from values of ki.

k~ and k~*.,.

1OO0-1100'C reaches 20 o/o. Theeffect of barium on this

index is less pronounced.

A study of the low temperature recrystallization offerrite of carbon steel indicates the start of this processat 540-620'C, depending on chemical compositlon.Modification with calcium and barium does not alter the

temperature of the start of recrystallization; hardness andthe rate of its decrease are practically identical for the

reference and the modified steel.

A study of microstructure showedthat modificationwith alkallne earth metals does not cause any change

ISIJ International, Vol.

in the amountof the constltuents of the structure or in

the rating of ferrite-pearlite bandlng in the hot rolledsteels. Calcium and barium hardly affect the value ofthe Acl (Arl) and Ac3 (Ar3), which indicates the slight

microalloying effect of these additions.

The modifying additions have a more appreciableInfluence on the structure of pearlite, increasing Its

fineness in the steels studied. An electron microscopestudy of hot rolled St3sp, 45 and 17MnlSl steels showedthat this influence begins to appear with O.0040/0 Ca.Calcium reduces the distance between the cementite

Fig. 15.

I/~t :

39 (1999), No. 7

plates (Fig. 15). Thus, in 17MnlSi steel this distance wasreduced from 0.0028mmin reference specimens to0.0018mmin steel with 0.0070/0 Ca. The influence ofbarium on the interlameliar spacing is I.5-2 tlmes smallerthan the influence of calcium.

An important consequence of modification withcalcium and barium is the more uniform distributionof austenite decomposition products of deformed steels

as a result of suppression of columnar crystallizationand lower heterogeneity with respect to carbon. Figure16 shows the favorable effect of modifiers on the mi-crostructure of low alioy steels after annealing andnormalizing. This is also confirmed by the more uni-form distribution of microhardness in the structure ofthese steels.

Influence of calcium on fineness (a) and compacted- ':.

,

h,.J~ ~ .:;~;1~.~•1It. , cness (b) ofhot rolled 17MnlSi steel.60) Jk ' L ' - '- ' 50~m

I-withoul addilions; II-wilh 0.0070/0 Ca: Fig. 16. Microstructure of 25Mn2Sisteel (a. b) and 15Mn2SiNote: (a) shows the distance between the cementic 60,steel (c, d) after annealing

plates: a. cwithout additions; b-0.0070/0 Ca;(b) showspearite slructurc, d-0.00050/0 Ba

Table ll. Compositions of Ba-be'arlng alloys produced by difi~rent countries.52)

,~: lr

~i 1,

~IIL

1' ab 'I~

.~

t

ta4

a •b

f

d~;" '

_j

>~~~'~~~,

fL:~:~~~~;:~/:;~'

tt/' ~

/;~.~

JL

.~d'_ ' 50~mL, .

Alloy

SiBa25

SiBa30SiBa35BaAl

SiCaBalO

SiCaBa12SiCaBal5SiCaBaSiCaBaSiCaBaSiCaBaAlSiCaBaAlSiCaBaAlSiCaBaAlSiCaBaAlSiCaBaMnSiCaBalOSiCaBal3SiCaBal7

Element ( %)Si

55 - 60

55 - 6055 - 60

balance

balancebalance

57 ~ 625748

38 - 4039484540

54 ~ 57balancebaiancebalance

Ca

~2

~15

~:13

~~13

~4- 17

2017

lO- 13

lO7.5

13ll

65~ 8.5

2017

17

Ba25 - 30

30 - 35

> 3540 - 45

~: lO

~ 12;~ 15

14 - 18

1616

9- 12

lO8.2

10lO

6.5 ~ 8.5

lO

13

17

Al

~3

~3~3

45 - 50

~2.0

~2.5

~30l .25

14

19 - 21

212.5

2020

~2.4

~2.5

~3.0

Fe

~ 15

~ lO

~ lO

~ lO

~ 12

~ 15

~ lO

~ lO

~ lO

Others

Mg0.6

Mn8- lO

Note

FormerUSSRstandard

TY14 5- 108 - 78lbid

ibid

FormerUSSRstandard

TY14- 5- 35 - 73FormerUSSRstandard

TY14- 5- 139 - 82ibid

ibid

U.S.A.FranceGermanyU.S A.

GermanyFormerUSSRJapanJapanJapanChinaChinaChina

633 ,'~ 1999 ISIJ


6. Brief Overview on Production of Barium-bearingAlloys

For better application of barium-bearing alloys it

maybe useful for the users to knowsomecharacteristics

of bariLun alloy production. The main cornpositions ofbarium-bearlng al]oys produced by different countries

are listed in Tab]e ll .5'-) Barium-bearing alloys contain

a lot of silicon, because they are produced on the basis

of production of ferrosilicon. SiBa alloys containing upto 300/0 of barium are used for treatment of cast iron

and steel. For different cases it Is expedient to addcalcium, magneslmTiand aluminum to the alloys; these

elements would strengthen the effects of modification anddeoxidation of the SIBa a]10ys. Barlum content changesin the range of I to 300/0; alLlmlnum, magnesiumandcalcium in the range of 0.3 to 150/0. Melting points ofthese alloys changein the range of I 100 to 1300'C, while

those for calcium sllicon I 050 to 1200'C. Denslty ofbarium-bearing alloys is around 3000-3 500kg/m3,which is heavier than that of calcium siiicon alloy,

20002500kg/m3, so they 'are e'asily to be assimilatedin steel.

According to constitution, the barytic ore can bedivided into three groups53).

I .Monobarytic or essentially-barytic ore (average

content BaS04>60 o/o).

2. Baryto-quarzitic ore (30 to 60 o/o BaS04,40 to 60(yo

Si02)'3. Baryto-lime ore (25 to 600/0 BaS04, 10 to 500/0

CaC03).Rese'arch54) on process of deoxidatlon of barium oxlde

'and barium Sulfate with silicon indicates that the processconsist of the following steps of interactlon; formationof barium silicates (up to I ,-OO'C); formation of si]icon

carbide and b'arium orthosilicates (Llp to 1800'C); re-

actlon between the silicon carbide and barium ortho-silic'ate forms bariLnn silicides (higher than 1800'C). Sothe formation of metallic phase depends to great extent

on the interaction betweenthe silicate slag of hlgh basicity

and silicon carbide. C,alclum sllicides are produced based

on this scheme, but this schemeis more favorable for

productlon of barium sllicides.

The experience of Ermakovskii Ferroal]oy Worksof

former Soviet Union on production of barium-bearingalloys in electric furnace of 1200kVAmaybe importantfor the users of barium-bearin_~: a]]oys. Somecharacteris-

tics of the production can be described as follows.5s)

The raw materials consist of barytlc ore (40 o/o BaS04,460/0 SiO_,), silicolde, Iime, coke and steel turnings. Thetechnology for production of silicon-barium alloys is

similar to that for ferrosilicon (750/0 Si). Under the

condition of the optimum addition of deoxidant the

electrodes could be immersed deeper; the tap hole ofthe rurnace COLL]d be opened easily; the metal fiows

smoothly 'and the elcctric regime of the furnace is stable.

Additlon ofsteel turni ngs Increases the recovery of silicon

for 7- 12o/o. but decreases the tr'ansfer of barium to alloy

tbr 6to 7[Vo. Sm'all addition of lime (-20/0) to the rawm'ateri'al is favorable for the process-decrease of the

consumption of the electrlc ener_~y for 5 to 100/0 and

1OO

~~;)

h~) 80>o

1::

'!)

~q,

~s 60

21:,

Q'

oBa, ~.

Fig. 17. Production indexes of fenosllrcon and alloys

containing different contents of barium in 1200kVAelectric furnace. 55,

I-recovery of barium in alloys;

2-productivity of furnace (P);

3-recovery of silicon in alloys:

4-specific electric energy consumption (A)

increase of the recovery of barium.Theproduction indexes dependgreatly on the amount

of the barytic ore added in the raw materials and theconcentratlon of barium in the alloy. Figure 17 showsthe production indexes of ferrosilicon and alloys con-taining different contents of barium in 1200kVA eiec-

tric furnace. In comparlson with the productlon of fer-

rosillcon (75 o/o Si), production of ferrosilicon containing40/0 Ba leads to 70/0 increase of productivity, and 50/0

decrease of electric energy consumption and Increaseof recovery of silicon In a]10y. Intensification of the

process depends to great extent on the complex reac-tion of barium and sulfur for deoxidation of silica in

consequenceof decrease of smelting temperature, vis-

cosity and surface tension of silica. It promotes the

great increase of the proportion of the favorable reac-tions in liquid phases. In this case silicon could bedeoxidized from the me]t without transfer of silica to

gaseous phase. S1lica is deoxidized through the reactionSi02(1) +2SiC=3Si(1)+2CO(g). Besides, the fluidity ofthe slag is increased, which promotes the regular flow ofthe siag and the ailoy from furnace.

Whenthe concentration of barlum increases to morethan 40/0 in the alloy, the productlon indexes areworsening. This is because the energy consumption for

deoxidatlon of bariLml is more than that for deoxida-tion of sillcon. Whenthe produced alloy contains 200/0

barium, the energy consumption is the sameas for the

production of ferrosillcon (750/0 Si); when the alloy

contains 300/0 barium, the energy consumption is 7.2010

hlgher than that for the production of ferrosilicon

(75 o/o Sl).

According to the data of trial sme]ting of SiBa alloys

uslng the electric furnace of I ,_OOkVAthe technical-

economicindexes of smelting of SiBa and SiCaBaalloys

and the sanitary condltion are better than those ofsmelting of calclum silicon alloy. Since the melting pointof barium silicide is signlficantly lower than th•at ofcalcium silicidess6). and also due to defective structureof barium orthosilicate,57) the deoxidation rates ofsilicon and barium are greater than those of silicon andcalcium.

(~)' 1999 ISIJ 634


20

Ba

80

~{e ~2~'

40 600 60 c).

(~ 700

~i~800

~~~

~~~60 900 o40

Ito~~o

.

1000

,~BaAl2Si280 L~j 20

!30~}1~~b !lOo

POO90Q

Si60 80

86~o

Al20 40IOO

Al,

at. 9:~0

Fig. 18. Projection drawin_~ of liquidus for Ba-SiAl sys-

tem.

58)

Al

0.2n;{~ o8

\n,

06

04hnv'

.~~

0.6

~, f

0.8

f~~ _~~/

oA

_4~_

c)

,

0.2

Si Ba0.2 O4 0.6 0.8

Fig. 19. Projection drawing of the curves ol' mixing iso-

enthalpy for A1--Si-Ba system 5'),

There are a little information on thermodynamicsofbarium a]loys, a projection drawing of liquidus ofBa-Si-AI system is shownIn Fig. 18.s8) Figure 19 showsthe projection drawing of the curves of mixing isoen-

thalpy for Al-Si-Ba system.59)

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o 1999 ISIJ 636

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