teknik metalurgi metallurgy

Zulfiadi Zulhan 2020 MG-3213 Metallurgy of Iron and Steel

Teknik Metalurgi11. Secondary Steelmaking / Ladle Metallurgy

Zulfiadi ZulhanDepartment of Metallurgical EngineeringFaculty of Mining and Petroleum EngineeringInstitut Teknologi BandungINDONESIA

Metallurgy of Iron and Steel (MG-3213)

6th Semester – 2019/2020


Teknik Metalurgi

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Teknik Metalurgi

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Teknik MetalurgiContent

1. Introduction

2. Burden materials preparation for ironmaking

3. Ironmakin in blast furnace

4. Blast furnace technology

5. Smelting reduction (COREX, HISMELT, DIOS, etc.)

6. Direct reduction (HyL I, HyL III, MIDREX, SL/RN, CIRCORED, etc.)

7. Heat and mass balance in ironmaking

8. Midterm Examination

9. Hot metal desulphurization & Steelmaking based on hot metal (de-C, de-Si, De-P,

Mn-removal, LD-Converter / BOF)

10. Steelmaking based on scrap and sponge iron (SIEMENS MARTINS, EAF)

11. Secondary metallurgy (Deoxidation, Desulphurization, Alloying, LF, CHF)

12. Vacuum metallurgy (RH, VD)

13. Stainless steelmaking (AOD, VOD)

14. Continous casting (CCM)

15. Group Presentation

16. Final Examination

4


Teknik Metalurgi

Scrap

COREX / FINEX (Smelting Reduction)

HM de-S

VTD/VTD-OB

RH / RH-OB

CCM

Casting

IngotPrimarySteelmaking

(Oxidation)Ironmaking(Reduction)

Secondary Steelmaking(Reduction + Final Refining + Adjust

Composition & T)

BF

Direct Reduction

EAF

BOF

LF

Ar

Vacuum Pump

Ar

Vacuum Pump

LTS

Iron and Steelmaking Route

5


Teknik Metalurgi

Secondary Metallurgy = Secondary Steelmaking

= Ladle Metallurgy

6


Teknik MetalurgiAims of secondary steelmaking

Secondary Metallurgy is the Hearth of All Production Steps of

Modern Steelmaking

deoxidation

deep decarburization

deep desulphurization

dehydrogenation

denitrogenation

alloying

heating

homogenization

Inclusion modification

control of steel cleanliness

temperature setting for casting

= Vacuum metallurgy

7


Teknik Metalurgi

Typical Impurities Content in Finished Products

Steel product Max. impurity (in ppm)

Inclusion size, D

IF steel [C]10-30, [N]40-50, T.O.40

Automotive and deep drawing [C]30, [N]30, D<100m

Drawn and ironed cans [C]30, [N]30, T.O.20, D<20m

Alloy steel for pressure vessels [P]70

Alloy steel bars [H]2, [N]10-20, T.O.10

HIC resistant steel [S]10, [P]50

Line pipe [S]10-30, [N]35-50, T.O.30, D<100m

Sheet for continuous annealing [N]30

Plate for welding [H]1.5

Ball bearings T.O.10, D<15m

Tire cord [H]2, [N]40, T.O.15, D<10-20m

Non-grain-oriented magnetic sheet [N]30

Heavy plate steel [H]2, [N]30-40, T.O.20, Dcluster <200m, Dsingle

inclusion <15m

Wire [N]60, T.O.30, D<20m

8


Teknik MetalurgiLadle (Brick)

9


Teknik MetalurgiLadle

10


Teknik MetalurgiLadle (Refractory) Heating

11


Teknik Metalurgi

Ladle (Refractory) Preheating / Heating

12


Teknik MetalurgiLadle Drying Curve

RHI

13


Teknik MetalurgiLadle Heat Up Curve

RHI

14


Teknik MetalurgiSlide Gate

15


Teknik MetalurgiSlide Gate Operation Concept

AISE, Steelmaking and Refining Volume, 1998

16


Teknik MetalurgiLadle Cycling Procedure


17


Teknik MetalurgiTemperatur and a[O]

18


Teknik MetalurgiTemperatur and a[O]

19


Teknik MetalurgiTemperature, a[O], Sampling

20


Teknik MetalurgiSampling of Liquid Steel

http://img.remastersys.com

http://img.burrillandco.com

21


Teknik MetalurgiSample delivery system to laboratory

22




Modern Steelmaking

deoxidation



dehydrogenation

denitrogenation

alloying

heating

homogenization




= Vacuum metallurgy

23


Teknik MetalurgiLadle (Monolithic + Brick)

24


Teknik MetalurgiPorous Plug

25


Teknik MetalurgiPorous Plug


26


Teknik Metalurgi3 Degasing

3 Degasing

27


Teknik MetalurgiStirring Power

+

=

oP 1.48

H 1 log

M

T V 14.23

28


Teknik MetalurgiArgon Connection

automatic

29




Modern Steelmaking

deoxidation



dehydrogenation

denitrogenation

alloying

heating

homogenization




= Vacuum metallurgy

30


Teknik MetalurgiDeoxidation

The first step in the refining sequence in the ladle is usually the

deoxidation of the steel with ferromanganese, ferrosilicon,

silicomanganese and aluminum.

(l) Mn as low or high C ferro alloy,

(2) Si as low or high C ferro alloy or as silico manganese alloy,

(3) Al of approximately 98% purity.

31


Teknik MetalurgiC-O-CO-Equilibrium

32


Teknik MetalurgiDeoxidation

Three categories of steel deoxidation.

(a) Unkilled Steel deoxidized with ferromanganese to yield 100–200 ppm

dissolved oxygen;

(b) Semi-killed steels deoxidized with:

(i) Si/Mn to yield 50–70 ppm dissolved oxygen,

(ii) Si/Mn/Al to yield 25–40 ppm dissolved oxygen,

(iii) Si/Mn/Ca to yield 15–20 ppm dissolved oxygen.

(c) Fully Killed steels deoxidized with aluminum to yield 2–4 ppm

dissolved oxygen.

33


Teknik MetalurgiAlloying

FeSi

Aluminium

34


Teknik MetalurgiDeoxidation by FeMn


35


Teknik MetalurgiDeoxidation by Si / Mn

Deoxidation by Si alone:


36


Teknik MetalurgiDeoxidation by Aluminium


37


Teknik Metalurgi

Deoxidation by Aluminium and Terner Diagram


38


Teknik Metalurgi

STEEL DEOXIDATION

Steel in the EAF just before tapping

- Mostly Fe

- Oxygen 700 to 1000 ppm

Addition of alloys during/after tap for two reasons:

1) Steel deoxidation

2) Achieve intermediate aim chemistries

BAKERREFRACTORIES

39


Teknik MetalurgiSTEEL DEOXIDATION

[O] + [M] = (MO)

Si, Mn, Al

Reports to the slag as:

SiO2, MnO and Al2O3

Si killed steel: 1000 ppm to 40 ppm (low-C)

1000 ppm to 25-15 ppm (high-C)

Al killed steel: 1000 ppm to < 10 ppm

1000 ppm

BAKERREFRACTORIES

40


Teknik MetalurgiSummary:

The calculation of the amounts of the alloys for

deoxidation and specifications is fairly simple - it is

normally based on the oxygen level in the steel and the

bath weight

Steelmaking is very routine and predictable?!

Wrong!

What is the Reality?

BAKERREFRACTORIES

41


Teknik MetalurgiThe reality of steelmaking

The [O] content in the furnace is not always known - If [O] is

estimated from C analysis, then considerable errors can be

made for low-C steel

The amount of slag carryover from the EAF could be highly

variable (old taphole vs. new taphole)

The flux additions are not adjusted for steelmaking variability -

The slag compositions in the ladle can vary greatly

BAKERREFRACTORIES

42


Teknik Metalurgi

The significance of the amount and composition of EAF carryover slag into the ladle

Extremely Important!

BAKERREFRACTORIES

43


Teknik Metalurgi

EAF slag carryover: Friend or Foe?

Benefits:

Act as fluxing precursor (liquid and hot)

Provide necessary slag volume

Disadvantages

P reversion

Si reversion for Al-killed steel

Poor alloy yields and subsequent late reversion of Mn and Cr

BAKERREFRACTORIES

44


Teknik Metalurgi

The effect of the FeO and MnO in the EAF slag

Contributes oxygen to the system

The efficiency of the Al or FeSi added for steel

deoxidation will be less because it will deoxidize the slag

too

The Mn, Cr and Si added for spec will reduce the FeO

and MnO in the slag so that its recovery in the steel will

be minimized

Deoxidation agents:

CaC2, Al shot,

SiC or FeSi fines

BAKERREFRACTORIES

45


Teknik Metalurgi

CaO

MgO

Al2O3

TiO2

SiO2

MnO

Cr2O3

FeONiO

Cu2O

CO

-40

-60

-80

-100

-120

-140

-160

-180

-200

-220

-240

-260

-280

-3001000400 600 800 1200 1400 1600 1800 2000200

TEMPERATURE (°C)

DG

°(k

Ca

l) S

tab

ility

of th

e o

xid

e

Stability of the oxides

Increasing

Stability 2912°F

The lower the line for the oxide

on the diagram the more stable

it is

The metal of any oxide can only reduce the oxides that are

above it on the diagram

Decreasing

Oxygen PotentialBAKERREFRACTORIES 46


Teknik MetalurgiRefractory/Slag/Metal Interactions

MgO

CaO

Al-Al2O3

FeO

-40

-60

-80

-100

-120

-140

-160

-180

-200

-220

-240

-260

-280

-3001000400 600 800 1200 1400 1600 1800 2000200

TEMPERATURE (°C)

DG

°(k

Ca

l) S

tab

ility

of th

e o

xid

e

Al

Al

Al

Al

Al

Al

Al

Al

Al

Al in Steel vs FeO in Slag Result:

Al fade and

Fe reversion

Al2O3

Inclusions

in the steel

Slag

FeO Al2O3

Steel

Fe Al

BAKERREFRACTORIES

47


Teknik Metalurgi

CaO

MgO

Al-Al2O3

SiO2

MnO

Cr2O3

FeO

-40

-60

-80

-100

-120

-140

-160

-180

-200

-220

-240

-260

-280

-3001000400 600 800 1200 1400 1600 1800200

TEMPERATURE (°C)

DG

°(k

Ca

l) S

tab

ility

of th

e o

xid

e

Refractory/Slag/Metal Interactions

Al + =Al2O3 +

(Fe,Cr,Mn,Si)

Slag

Steel

BAKERREFRACTORIES

48


Teknik Metalurgi

CaO

MgO

Al2O3

TiO2

SiO2

MnO

Cr2O3

FeONiO

Cu2O

CO

-40

-60

-80

-100

-120

-140

-160

-180

-200

-220

-240

-260

-280

-3001000400 600 800 1200 1400 1600 1800200

TEMPERATURE (°C)

DG

°(k

Ca

l) S

tab

ility

of th

e o

xid

e

Scrap quality and Steelmaking

Oxygen Blow

in EAF

Si Mn

Cr

Metal

(Scrap)

EAF

Slag

Al

Al2O3

Ti

TiO2

SiO2 MnO

Cr2O3

BAKERREFRACTORIES

49


Teknik Metalurgi

Slag/Metal Interactions:

Metal

Slag

FeO

MnOSiO2

Al, Si, Mn

FeO, MnO, SiO2

BAKERREFRACTORIES

50


Teknik Metalurgi


Metal

Slag

Al, Si, Mn

FeO

BAKERREFRACTORIES

51


Teknik Metalurgi


Metal

Slag

Al, Si, Mn

BAKERREFRACTORIES

52


Teknik Metalurgi


Metal

Slag

FeO

Al, Si, Mn

BAKERREFRACTORIES

53


Teknik Metalurgi


Metal

Slag

FeO

Al, Si,

MnFe

Al2O3

SiO2

MnO

BAKERREFRACTORIES

54


Teknik Metalurgi

Metal

Slag

Fe Al2O3

SiO2, MnO

(burp!)

BAKERREFRACTORIES

55


Teknik Metalurgi


Metal

Slag

Al, Si

MnO

BAKERREFRACTORIES

56


Teknik Metalurgi


Metal

Slag

Al, Si

MnO

BAKERREFRACTORIES

57


Teknik Metalurgi


Metal

Slag

Al, Si

MnO

BAKERREFRACTORIES

58


Teknik Metalurgi


Metal

Slag

MnO

Al, SiMn

Al2O3

SiO2

BAKERREFRACTORIES

59


Teknik Metalurgi

Metal

Slag

Mn Al2O3

SiO2

(hic!)

BAKERREFRACTORIES

60


Teknik Metalurgi

How to get rid of these oxides

Metal

Slag

FeO

MnOSiO2

Al, Si, Mn

FeO

CaC2

Al shot

FeSi fines

SiC

MnO SiO2

BAKERREFRACTORIES

61


Teknik Metalurgi

How do we know when the slag is deoxidized?

Do we need chemical analysis?

BAKERREFRACTORIES

62


Teknik Metalurgi

CaO

MgO

Al2O3

SiO2

CaF2

White

FeO - Black

MnO - Green

Brown

LOOK AT THE SLAG COLOR:

BAKERREFRACTORIES

63




Modern Steelmaking

deoxidation



dehydrogenation

denitrogenation

alloying

heating

homogenization




= Vacuum metallurgy

64


Teknik Metalurgi

Ladle Desulphurization (by TOP SLAG)

Proses desulfurisasi merupakan proses reduksi, maksudnya unsur sulfur yang terlarut

dalam lelehan baja direduksi menjadi ion sulfida.

Menurut Oeters, elektron yang dibutuhkan untuk membentuk ion sulfida ini diberikan oleh

ion oksigen menurut persamaan reaksi berikut ini:

S + O2- = S2- + O

Kation yang umumnya digunakan untuk mengikat ion sulfida adalah ion Ca2+ karena dapat

membentuk senyawa kalsium sulfida (CaS) yang stabil

Jika ion oksigen yang digunakan untuk mereduksi sulfur diikat oleh ion kalsium dalam

bentuk CaO dan ditambahkan sebagai senyawa untuk membentuk terak maka reaksi

desulfurisasi yang terjadi adalah:

(CaO) + S = (CaS) + O

Untuk mencegah oksigen yang dihasilkan terlarut kembali ke dalam baja serta dapat

merubah suasana reduksi menjadi oksidasi, maka ditambahkan deoksidator seperti

silikon, aluminium dan karbon. Dalam hal aluminiun sebagai deoksidatornya, maka reaksi

desulfurisasi adalah sebagai berikut:

3 (CaO) + 2 Al + 3 S = 3 (CaS) + Al2O3

65


Teknik MetalurgiLadle Desulphurization

66


Teknik MetalurgiSulphide Capacity

67



68



69


Teknik MetalurgiOptical Basicity

oxygen of number x componen of fraction olem

oxygen of number x componen of fraction olemX

=

= XAOx. AOx + XBOy. Boy + …

Oxide Optical Basicity ()

Na2O 1.15

CaO 1.00

MgO 0.78

CaF2 0.67

TiO2 0.61

Al2O3 0.61

MnO 0.59

Cr2O3 0.55

FeO 0.51

Fe2O3 0.48

SiO2 0.48

70


Teknik MetalurgiSulphide Capacity of Slag

KTH Model, 1999

( )[ ]

OSS

Metal

SlagS

alog-flogClog1,375T

935-

%S

%SlogLlog

+++=

=

RT(ln Cs) = 58.8157*T – 118535 – {XAl2O3.157705.28 – XCaO*33099.43 +

XMgO*9573.07 – XMnO*36626.46 + XSiO2*168872.59} – { CaOOAleractionint

32 -x + MnOOAl

eractionint32 -

x +

232 SiOOAleractionint

-x + 2SiOCaO

eractionint-

x + 2SiOMgOeractionint-

x + 2SiOMnOeractionint-

x + 2SiOFeOeractionint-

x + CaOFeOeractionint-x + MnOFeO

eractionint-x +

MgOCaOOAleractionint

32 --x + 232 SiOCaOOAl

eractionint--

x + MnOMgOOAleractionint

32 --x + 232 SiOMgOOAl

eractionint--

x +

232 SiOMnOOAleractionint

--x + 2SiOMgOCaO

eractionint--

x + 2SiOMnOCaOeractionint

--x + 2SiOMnOMgO

eractionint--

x + 2SiOMgOFeOeractionint

--x +

232 SiOOAlFeOeractionint

--x + 2SiOMnOFeO

eractionint--

x + 2SiOFeOCaOeractionint

--x }

71


Teknik Metalurgi

System x interaction

Al2 O3 – CaO CaOOAl

eractionint32-

x = yAl3+

. yCa2+

. [9,82827968.104

+ 55,07340941 . T]

Al2 O3 – MgO MnOOAl

eractionint32-

x = yAl3+

. yMn2+

. [4,33987403.105

+ 2,49121594.102

.T. (yAl3+

- yMn2+

)]

Al2 O3 – SiO2 232 SiOOAl

eractionint

-x = yAl

3+. ySi

4+. [1,86850468.10

5]

CaO – SiO2 2SiOCaO

eractionint

-x = yCa

2+.ySi

4+[9,72717695.10

4 + 72,8749746.T]

MgO – SiO2 2SiOMgO

eractionint

-x = yMg

2+.ySi

2+.[6,97403222.10

5– 2,24084556.10

2.T]

MnO – SiO2 2SiOMnO

eractionint

-x = yMn

2+. ySi

4+.[-3,2291147.10

5 + 2,1202998.10

2.T + 1,34860658.10

5.(yMn

2+- ySi

4+)]

FeO – SiO2 2SiOFeO

eractionint

-x = yFe

2+.ySi

4+.[-3,85381423.10

5+ 2,09908747.10

2.T + 1,6193563.10

5. (yFe

2+- ySi

4+))

FeO – CaO CaOFeO

eractionint

-x = yFe

2+.yCa

2+.[1,74180413.10

2+ 9,3184392.10

1.T – 1,14946043.10

5.(yCa

2+- yFe

2+)]

FeO – MnO MnOFeOeractionint-

x = yFe2+

.yMn2+

.[8,47784954.105

– 3,48193022.102

.T]

Al2 O3 – CaO – MgO MgOCaOOAl

eractionint32

--x = yAl

3+.yCa

2+.yMg

2+.[4,1659555.10

6– 1,06656631.10

3.T – 3,04080189.10

6.yAl

3+)

Al2 O3 – CaO – SiO2 232 SiOCaOOAl

eractioniint

--x = yAl

3+.yCa

2+.yMg

2+.[-2,03579264.10

6+ 6,86044695.10

2.T]

Al2 O3 – MgO – MnO MnOMgOOAl

eractionint32

--x = yAl

3+.yMg

2+.yMn

2+.[-1,56149723.10

6+ 2,72278645.10

3.T – 1,22741846.10

7.yAl

3+]

Al2 O3 – MgO – SiO2 232 SiOMgOOAl

eractionint

--x = yAl

3+.yMg

2+.ySi

4+.[1,56192588.10

5– 2,90498555.10

2.T + 9,49447247.10

5.yAl

3+]

Al2 O3 – MnO – SiO2 232 SiOMnOOAl

eractionint

--x = yAl

3+.yMn

2+.ySi

4+.[1,5658486.10

6– 6,62494162.10

2.T – 5,32290311.10

6.yAl

3+]

CaO – MgO – SiO2 2SiOMgOCaO

eractionint

--x = yCa

2+.yMg

2+.ySi

4+.[-1,52649771.10

6+ 6,25663842.10

2.T + 1,48525598.10

6.yCa

2+)

CaO – MnO – SiO2 2SiOMnOCaO

eractionint

--x = yCa

2+.yMn

2+.ySi

4+.[-1,17989159.10

6+ 6,21243714.10

2.T – 1,19111179.10

6.yCa

2+]

MgO – MnO – SiO2 2SiOMnOMgO

eractionint

--x = yMg

2+.yMn

2+.ySi

4+.[9,10360927.10

6– 4,42600708.10

3.T – 2,86966462.10

6yMg

2+]

FeO – MgO – SiO2 2SiOMgOFeO

eractionint

--x = yFe

2+.yMg

2+.ySi

4+.[1,5501739.10

6– 1,12815899.10

3.T + 1,43235112.10

6. yFe

2+]

FeO – Al2 O3 – SiO2 232 SiOOAlFeO

eractionint

--x = yFe

2+.yAl

4+.ySi

4+.[-2,62147542.10

6+ 1,46552872.10

3.T – 2,7752503.10

6.yAl

3+]

FeO – MnO – SiO2 2SiOMnOFeO

eractionint

--x = yFe

2+.yMn

2+.ySi

4+.[-8,24444429.10

5+ 1,64329498.10

2.T + 7,22404274.10

5.yFe

2+]

CaO – FeO – SiO2 2SiOFeOCaO

eractionint

--x = yCa

2+.yFe

2+.ySi

4+.[-1,22135555.10

6+ 6,50216976.10

2.T – 1,50675926.10

6.yCa

2+]

72


Teknik MetalurgiSulphur Distribution Ratio

73



74




75


Teknik Metalurgi

Kinetics of Slag-Metal Reactions in a Gas-Stirred Bath

Slag metal reactions in steelmaking

can be stimulated by gas stirring.

Consider the transfer of sulphur

from metal to slag.

Deo, Boom, Principles of Steelmaking Metallurgy, 1993

76


Teknik Metalurgi

Kinetics of Slag-Metal Reactions in a Gas-Stirred Bath


77


Teknik MetalurgiCase 1: Metal Phase Control

In a gas-stirred system , number of moles transferred per unit time per unit

are:

)(Jflux momentum )(Jflux diffusive J DtDmD +=

Momentum flux approaches zero value at the interface:

( )i

m

b

m

D

mDmD CC k J J -==

At temperature of steelmaking, chemical reactions are extremely fast.

Therefore, a pseudo or instantaneous thermodynamic equilibrium may be

assumed to exist at the interface during small time interval (Dt → 0)

pi

s

i

m

eq

s

eq

m L C

C

C

C==

Lp is equilibrium constant, sometimes denoted as

partition or distribution coefficient.

( )i

sp

b

mmDmD C L C k J J -== ( )i

sp

b

mmm

m C L C k A

V

dt

dC - J -==

78


Teknik MetalurgiDesulphurization Kinetics

( )

+= .t

w w. L / w. L

K - exp

]S[ - ]S[

]S[ - ]S[

mssss

p

fi

ft

t = time in minutes

[S]f = final sulphur content (wt.-%)

[S]i = initial sulphur content (wt.-%)

Ws = weight of slag (kg)

Wm = weight of liquid steel (kg)

Ls = Sulphur distribution ratio

Kp = desulphurization rate constant (1/minutes)

79


Teknik Metalurgi

Effect of gas flowrate and stirring power on the desulfurization rate constant.


80


Teknik MetalurgiExample of Desulphurization Model

160

100 1630

50

2 Units

Units Total Slag 4000 kg

C 0.160 % Weight 25 kg/t

Si 0.400 % CaO 54 %

Mn 1.400 % Al2O3 28 %

Al 0.060 % 0.058 SiO2 12 %

P 0.010 % MgO 5 % 0.008081649 1.033898565 1.038072319

Nb 0.000 % FeO 0.5 % 0.000359542

V 0.000 % MnO 0.5 % 1.068981045 0.389967162 0.556802117

Ti 0.000 % Total 100 % 4.644831934

Cr 0.030 % 1.10388371 1.032164815

Cu 0.030 % Sulphur capacity 0.00264 1.563386514 1.143556402Ni 0.030 % LS = (S)/[S] 166 1.060999062 1.013086434

Ca 0.000 % S final 19.5 0 4.15661E-05

N 90 ppm 19 60 0.000102333

O 3 ppm De-S degree % 60.6 0.208582737 27.13841208

0.084280581

0.000194984

t (minute)Vacuum

Pressure [mbar]

Argon flow

[Nl/min]S [ppm]

0 1000 400 50 20.90666183 1626.17 3.98003

1 500 400 49 35.17474264 1623.717 6.43318

2 200 400 48 53.88289911 1621.371 8.779

3 100 400 46 67.7671052 1619.124 11.0263 = Important area to be filled

4 50 400 44 71.84048012 1616.967 13.1831

5 30 400 41 73.96115058 1614.893 15.2571 = Slag composition

6 20 400 39 80.0143901 1612.895 17.2552

7 5 400 37 89.30498093 1610.966 19.1839 Note: If more than 2 percent FeO and MnO in the slag,

8 2 400 34 96.22714066 1609.101 21.0493 please check Oxygen content in steel (Oxygen content

9 2 400 32 108.4234328 1607.293 22.8568 muss be higher than 10 ppm)

10 2 400 29 150.8364698 1605.538 24.6115

11 2 400 28 148.6251858 1603.832 26.3181

12 2 400 26 146.2743986 1602.169 27.9809

13 2 400 25 143.7874626 1600.546 29.6036

14 2 400 24 141.1674356 1598.96 31.1899

15 2 400 23 138.4171054 1597.407 32.743

16 2 400 22 135.5390162 1595.884 34.2657

17 2 400 22 132.5354918 1594.389 35.7608

18 2 400 21 129.4086581 1592.92 37.2305 Zulfiadi Zulhan

19 2 400 21 126.1604637 1591.473 38.677

20 2 400 20 122.7926983 1590.048 40.1021

7 21 2 400 20 119.307011 1588.642 41.5076

22 2 400 20 115.7049254 1587.255 42.8949

0 23 2 400 20 111.9878551 1585.885 44.2654

0 24 2 400 20 108.1571161 1584.53 45.6202

0 25 2 400 20 104.2139394 1583.19 46.9604

Desulphurization

Start composition

Steel Weight [tons]

Slag at Start

Start Temp. (oC)Sulphur at tapping [ppm]

Sulphur at start [ppm]

0

10

20

30

40

50

60

0 5 10 15 20 25

Time [minutes]

Su

lph

ur

[pp

m]

1

10

100

1000

Pre

ss

ure

[m

ba

r];

Ar

flo

w [

Nl/m

in]

Sulphur at time t Sulphur final Ar Pressure

De-S

This area is not suggested

for desulphurization,

because the slag viscosity is

high and CaO is already over

saturated

Optimum Slag

composition

CaO sat. = 0,8

CaO sat. = 1,2

CaO sat. = 1,1

CaO sat. = 1,0

CaO sat. = 0,9

81


Teknik MetalurgiDesulphurization by Powder Injection


82


Teknik MetalurgiPowder Injection

83


Teknik Metalurgi

Desulphurization (Top Slag vs. Powder Injection)

84




Modern Steelmaking

deoxidation



dehydrogenation

denitrogenation

alloying

heating

homogenization




= Vacuum metallurgy

85


Teknik MetalurgiKey to Steel (Stahlschlüssel)

86



87



88


Teknik Metalurgi

Example of Steel Grade (Stahlschlüssel)

89


Teknik Metalurgi

Example of Steel Grade (Stahlschlüssel)

90


Teknik MetalurgiAlloying

C Si Mn P S Ni Cr Mo Nb V Al Cu [N] [H] a[O] [O]tot Temp

% % % % % % % % % % ppm % ppm ppm ppm ppm Liquidus

Specification0,58

0,63

1,60

2,00

0,60

0,90< 0,020

<

0,020

<

0,025< 0,03 0,00 0,00 0,00 < 300

<

0,02060 3 5 20

1477

AIM 0,60 1,80 0,75 0,010 0,005 1,90 0,55 0,25 0,00 0,00 200 60 3,0 5 20

Overheat

EAF Tapping 0,07 0,01 0,20 0,015 0,020 0,01 0,01 0,01 0,00 0,00 0 80 6 500 500 150

LF Start 0,35 1,30 0,30 0,015 0,020 0,05 0,01 0,01 0,00 0,00 200 90 6 <15 <50 90

LF End 0,58 1,60 0,60 0,015 0,010 0,05 0,01 0,01 0,00 0,00 300 100 7 10 30 140

VD Start 0,58 1,60 0,60 0,015 0,010 0,05 0,01 0,01 0,00 0,00 300 100 7 10 30 140

VD End 0,60 1,80 0,80 0,015 0,005 0,05 0,01 0,01 0,00 0,00 400 40 3 3 20 70

SPRING STEEL 60S2A

C Si Mn P S Ni Cr Cu Nb V Al Ti [N] [H] a[O] [O]tot Temp

% % % % % % % % % % ppm ppm ppm ppm ppm ppm Liquidus

Specification0,06

0,08

0,15

0,30

1,25

1,35< 0,015

<

0,005< 0,25 < 0,25 < 0,25

0,04

0,05

0,08

0,10

200

300

100

300< 60 < 1,5 < 5 < 20 1520°

AIM 0,07 0,25 1,30 0,015 0,005 0,25 0,25 0,20 0,05 0,09 300 300 50 1,5 5 20

Overheat

EAF Tapping 0,05 0,01 0,15 0,010 0,015 0,20 0,20 0,20 0,00 0,00 0 0 50 5 500 500 150

LF Start 0,05 0,10 0,80 0,010 0,013 0,20 0,20 0,20 0,00 0,00 200 0 60 6 < 15 < 50 100

LF End 0,06 0,20 1,25 0,010 0,008 0,20 0,20 0,20 0,00 0,00 300 0 70 7 10 40 150

VD Start 0,06 0,20 1,25 0,012 0,008 0,20 0,20 0,20 0,00 0,00 300 0 70 7 10 40 150

VD End 0,07 0,25 1,30 0,012 0,004 0,20 0,20 0,20 0,05 0,09 300 300 50 1,5 5 20 60

API 5L-X60

91


Teknik MetalurgiAlloying Chemical Composition

Temperature change in °C

per 1% addition of pure

element using commercial

alloys (temperature of the

melt 1600°C)

Stolte, G., Secondary Metallurgy, Stahl und Eisen, 2002

92


Teknik MetalurgiTemperature drop by Addition

Ghosh, A., Secondary Steelmaking, 2001

93


Teknik MetalurgiAlloy Yield


94


Teknik MetalurgiTemperature drop rate for 200t Ladle


95




Modern Steelmaking

deoxidation



dehydrogenation

denitrogenation

alloying

heating

homogenization




= Vacuum metallurgy

96


Teknik Metalurgi

Treatments:

• Desulphurisation

• Temp. Control

• Trimming

• Alloying

L T S

(Ladle Treatment Station)

Water-cooled

Ladle Cover

Argon Stirring &

Powder Blowing

Lance

Ladle

Car

Argon BrickSlide Gate

Alloying

Hopper

Ladle Treatment Station

97


Teknik MetalurgiLadle Furnace (LF)

After removal of phosphorous and carbon by oxygen blowing, which is

done in oxygen converter (BOF) or in electric arc furnace (EAF), the melt

is tapped.

All further necessary steps to produce high quality steel economically are

executed in the ladle. But this practice has its limitation in the

temperature loss of the melt, especially if a high amount of of ferroalloys

has to be added or a degassing treatment is required. In this case, the

melt has to be tapped at 1700 to 1750°C. It reduces the precondition for

removal of phosphorous in the furnace. Furthermore, the specific

consumption of iron, oxygen and lime in the BOF is increased.

To avoid these negative effects, most of steelmakers have installed a

heating device between BOF/EAF and continous caster.

98



Since the beginning og the 1970s, the ladle furnace has become used

more and more, firstly in EAF shops and a little later in BOF plants. Today

most steel plants are equipped with a ladle furnace

The aim is to increase the overall productivity.

The principle function of a ladle furnace is similar to that of an EAF.

The roof of ladle furnace is similar to an electric arc furnace. The roof is

equipped with three electrodes, an alloying chute, a wire feeding

machine, (a powder blowing device), an emergency stirring lance as well

as a facility for sampling and temperature/oxygen activity measurement.

99



▪ Heating of liquid steel at max.

5°C/min

▪ Alloying

▪ Stirring of the heat (rapid

dissolution of alloys)

▪ Desulphurization

▪ Increase the degree of

cleanliness

▪ Buffer function (minimization of

return heats from the continuous

caster)

100


Teknik MetalurgiLadle Furnace


101



102


Teknik MetalurgiCapacity of Transformer

Ladle furnace is equipped with a transformer which modifies the electrical energy

of the power station into the required condition.

C = capacity of transformer; c = specific energy in kWh/(t.°C); for steel 0.23

x = requested heating rate of the melt, normally 4 or 5 °C/min. The temperature

losses of the melt caused by the ladle refractory and the radiation through the

top slaf during the heating period must be added.

Y = ladle content in ton; F = conversion factor, 60 min/h; cos = 0.7

The electrical efficiency (cable, trafo ~ 0.9) determines how much of the consumed

electrical energy reaches the electric arc.

The thermal efficiency (therm ~ 0.6) describes how much of this energy enters

the liquid steel (heating energy).

=

cos

Fc x y ]MVA[C

trafo,cabletherm

103


Teknik Metalurgi


104



105



106


Teknik Metalurgi

Typical LF Treatment Pattern


107


Teknik Metalurgi


108


Teknik Metalurgi

CAS – OB (Composition Adjustment by Sealed Argon Bubbling – Oxygen Blowing)

Developed by Nippon Steel Corp.Stolte, G., Secondary Metallurgy, Stahl und Eisen, 2002

109


Teknik Metalurgi

Increase Temperature by Oxygen Blowing


110


Teknik MetalurgiCAS OB (SMS MEVAC)

111


Teknik Metalurgi

HALT = Heating Advanced Ladle

Treatment


112


Teknik Metalurgi

IR-UT (Injection Refining Up

Temperature), Sumitomo JapanBethlehem Steel, USA


113


Teknik MetalurgiExample

130t liquid steel in ladle will be heated in CAS-OB plant from 1550°C to

1600°C. Oxygen blowing rate is 2000 Nm3/h. Calculate the amount of

oxygen and aluminium needed for this purpose. Oxygen and aluminium

yield is 80% and 90% respectively.

114


Teknik MetalurgiLF vs. CAS-OB


115




Modern Steelmaking

deoxidation



dehydrogenation

denitrogenation

alloying

heating

homogenization




= Vacuum metallurgy

116


Teknik MetalurgiInclusions

Inclusions are non-metallic particles embedded in matrix of metals and

alloys.

Inclusions haven been found to be harmful to the mechanical

properties and corrosion resistance of steel, especially for high strength

of steel clean steel.

However, no steel can be totally free from inclusions.

117


Teknik MetalurgiClean Steel

Definition of “clean steel” is dependent upon the final product application.

In general, requirement of clean steel become more severe / stringent as

the applied / final product thickness is reduced

Non-metallic inclusions (NMI) become important when they are

responsible for producing defects during steel processing or the final

product application.

Inclusions (D < 4 m) are always present in cast products and rarely

produce product defects.

Significant amount of larger inclusions (20-150 m) product defect

problem tend to occur.

Some times, one single large inclusion is enough to cause a

catastrophic defect in the whole steel product.

118


Teknik MetalurgiClean Steel

Larger inclusions can results from excessive stirring practices

slag entrainment into steel

reoxidation of bath

refractory erosion

There are two types of non-metallic (oxide) inclusions:

1. Endogenous inclusions:

- occurring naturally and can only be minimized but not completely

eliminated.

2. Exogenous inclusions:

- derived from entrainment of slag of refractory erosion

- always process related and can be eliminated by implementing

suitable processing procedures.

119


Teknik MetalurgiEndogenous Inclusions

Resulted from the reaction between dissolved oxygen with deoxidants such

as Al, FeSi, SiMn or FeMn. Product is oxide inclusions.

Endogenous inclusions are always in chemical equilibrium with liquid steel

constituents.

For Al-killed steel, dissolved oxygen is ~ 3 ppm, number of inclusions that

can be precipitated during cooling from liquid steel to solid steel is low.

Cooling of MnSi-killed steel, change of dissolved oxygen during

solidification ~ 30 ppm (number of inclusions precipitated during cooling is

relatively large.

Endogenous inclusion can be solid or liquid. If all solid clusters is removed,

inclusion diameters are between ~1 and 5 m.

If reoxidation occurs just prior to casting, inclusion diameter: ~1 to ~60 m.

120


Teknik MetalurgiEndogenous Inclusion

121


Teknik MetalurgiExogenous Inclusions

Exogenous inclusions are mostly complex particulate oxides of entrained

slag resulted from excessive turbulence at slag-metal interface.

At steelmaking temperature, exogenous inclusions are usually liquid and

spherical with sizes ranging from ~10-300 m.

Turbulence slag-metal interface is caused by pouring streams, vigorous

stirring.

If slag entrainment takes place just prior to casting, there may not be

enough time to be removed from liquid steel and results an extensive

dispersion of large particles (>100 m).

Poorly controlled practices in the mould, tundish, and ladle are chiefly

responsible for the presence of large exogenous inclusions in cast

produduct.

122


Teknik MetalurgiExogenous Inclusion

123


Teknik MetalurgiReoxidation

Reoxidation increases oxygen content of steel bath.

▪ reduces deoxidant efficiency

▪ Increases opportunity for nozzle blockage at caster

It occurs during and after deoxidation, main oxygen source:

o air entrainment

o oxygen-containing ladle slag

o chemically unstable refractory

o ladle glaze or bottom slag that results from earlier heats in ladle.

Prevention:

✓ Steel bath is fully covered at all times with a suitably thick slag layer.

Exposure to atmosphere during metal transfer from ladle to tundish and

from tundish to mould, even for a few second, can reoxidised of steel.

✓ Extended refractory nozzles and / or gas shrouding.

✓ Reduce FeO + MnO in Slag, reduce slag carry over.


Teknik MetalurgiSource of Non Metallic inclusion

Non metallic inclusion arise from three sources:

1. Deoxidation inclusions resulting from the addition of deoxidants, and

reoxidation inclusions resulting from exposure of the liquid steel to the

atmosphere or to an unstable refractory

2. Refractory derived inclusions arising from sands (e.g. well filler) and

chemically or mechanically erodable refractory materials that line and

protect steel-processing vessels

3. Slag-derived inclusions that results from high metal flow rates at the

steel / slag interface and emulsification of the covering slag followed

by entrainment of the liquid slag droplets into the bulk liquid steel

Stuart Millman: Corus, UK, 2004

Deoxidation inclusions are a natural feature of steel processing but

reoxidation inclusions, refractory derived inclusions and slag derived liquid

inclusions may be reduced or eliminated completely by optimising steel

the steel processing operations.

125125


Teknik MetalurgiOperating Practice: Primary Steelmaking

Low and consistent oxidation state of steel and slag is required at tap to

limit downstream demands on oxidation

Dissolved oxygen in liquid steel at tap is monitored by CELOX

Amount of slag carry over to ladle must be limited

Slag conditioning using slag deoxidants: CaC2, Al pellet


126


Teknik MetalurgiTapping Oxygen from Furnace

127


Teknik MetalurgiFeO + MnO in ladle slag

128


Teknik MetalurgiOperating Practice: Secondary Steelmaking

Ladle refractory: chemically and physically stable at steelmaking

temperature.

Previous use of ladle leaves it contaminated after casting by a slag glaze

embedded onto and into ladle refractory walls together with slag on ladle

bottom. Ladle glaze can contain chemical elements that may generate

harmful inclusions on its next use. Therefore, for steelplant producing a

range of steel qualities, ladle-washout casts will often employed on a clean

steel route to replace a previous ladle glaze with a more benign one.

At tap, dissolved oxygen in steel can be reduced immediately by adding

primary deoxidants and alloying agents into ladle. Highest efficiency and

consistency is assured when all deoxidation and alloying additions are

entrained directly into steel bath by mixing energy of tapping stream.

129


Teknik Metalurgi

Schematic Representation of Mechanism of Glaze Formation on Ladle Walls

130



Deoxidation reactions are generally very fast, but removal of oxidation

products, particularly those < 50 m is relatively slow. Sufficient time

must be provided, using appropriate stirring conditions, to help bring

inclusions into contact with ladle slag or each other.

Extended inclusion flotation time must comply with logistical constraints

of plant operations.

Late additions of deoxidant or alloys to ladle must be avoided to ensure

that newly formed inclusions are allowed adequate time for their

removal, particularly during final stage of steel processing.


131


Teknik MetalurgiNon-Metallic Inclusion Size Post-deoxidation

132


Teknik Metalurgi

133



Synthetic slag addition to ladle top dilutes the reducible oxides in carried

over tapping slag and also forms a physical form between the steel

surface and surrounding atmosphere.


Effect of slag composition on

the soluble oxygen content as

function of silicon content of Si-

killed medium carbon steel at

1580oC

134


Teknik Metalurgi

135


Teknik Metalurgi

136


Teknik MetalurgiInclusion Modification

Inclusion control:

1. Minimizing the occurrence of inclusions

2. Modifying the inclusions to globular shape and desirable properties

Inclusion modification by treatment of liquid steel with calcium

Calcium is introduced into molten steel as CaSi based alloy powder,

either by powder injection of by feeding through hollow metallic tubes.

Calcium treatment of steel is a common practice for modification of

alumina inclusions in aluminium killed steels, and to prevent nozzle

clogging during continuous casting operations.

With calcium treatment, alumina and silica inclusions are converted to

liquid calcium aluminates or calcium silicates which are globular in shape.

137


Teknik MetalurgiReactions of Calcium in Steel


138


Teknik Metalurgi


139


Teknik Metalurgi


140


Teknik MetalurgiWire Injection

141


Teknik MetalurgiCa (wire) injection


142


Teknik Metalurgi


143


Teknik MetalurgiSoft Bubbling for Clean Steel

Soft bubbling stirring in minutes

To

tal o

xyg

en

co

nte

nt in

pp

m

Dillinger Hütte, Germany: Soft bubbling ~ 0.2 L /(min.ton steel)

144


Teknik MetalurgiSaran untuk SOP untuk Clean Steel / Pola Operasi

EAF:

1. Aim karbon ditingkatkan dan aim oksigen diturunkan pada saat akan

tapping dari Furnace, sesuai dengan steel grade yang diproduksi.

2. Mengontrol kandungan oxygen terlarut dengan CELOX

3. Mengurangi/mencegah slag bawaan (slag carry over) dari furnaceLF:

1. Menambahkan CaC2 / Al shot untuk mengurangi jumlah oksida dalam

slag (FeO + MnO < 2%)

2. Slag/Metal Mixing: stirring energy yang tinggi diinginkan pada tahap

awal untuk mendapatkan kesetimbangan kimia antara metal dan slag,

pelarutan dari alloy dan aglomerasi dari inclusi.

3. Mengatur komposisi slag yang optimum untuk mendapatkan slag yang

mempunyai oksigen rendah (SiO2 rendah)

4. Mengusahakan untuk tidak menambahkan lagi deoksidator diakhir

proses di LF

5. Melakukan soft bubbling ~ 10 menit

145


Teknik MetalurgiSaran untuk SOP untuk Clean Steel / Pola Operasi

Tundish:

1. Inertisasi tundish, jika memungkinkan.

2. Menggunakan tundish flux yang sesuai (CaO-Al2O3-SiO2, dengan

SiO2 <10%), bukan sekam padi

3. Melakukan pengukuran TOS

CCM:

1. Flow control dalam mould

2. Constant casting speed

3. Menggunakan powder viskositas tinggi

146


Teknik MetalurgiThank you for your attention!

Zulfiadi Zulhan

Department of Metallurgical Engineering

Institut Teknologi Bandung

Jl. Ganesha No. 10

Bandung 40132

INDONESIA

Telefon : +62 (0) 22 250 2239

Fax : +62 (0) 22 250 4209

Mobil : +62 (0) 813 22 93 94 70

E-Mail: [email protected]

mailto:[email protected]

teknik metalurgi metallurgy

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