SFB 761 „Stahl ab initio

SFB 761 „Stahl ab initio“

25.08.2009„MSE“ Berlin

Uni. Prof. Dr.-Ing. D. SenkDipl.-Ing. A. Lob

Smelting and Soldification of Fe-Mn-C Steel

Senk, Lob

SFB 761 „Stahl ab initio“ Subarea B1

Smelting and Solidification of Fe-Mn-C SteelSubtask: Manganese Vaporisation

Picture: A. Lob

25.08.09, No. 1

Senk, Lob

Smelting and Solidification of Fe-Mn-C SteelSubtask: Manganese Vaporisation


25.08.09, No. 2

1. Presentation of the System Fe-Mn-C

2. a. Calculation of the Vapour Pressure for the Sytem Fe-Mn;b. Temperature Dependence

3. Experimentsa. Melting Furnaceb. Parameters for Manganese Vaporisationc. Pressure Dependenced. Atmosphere Dependencee. Temperature Dependece

4. Outlook for further Experimentsa. Thermal Convection

5. Abstract

Senk, Lob

Choice of chemical composition:SFE depending on forming mechanism- TRIP-Steel

TRansformationInduced Plasticity (I IV V)

- TWIP-Steel Twinning Induced Plasticity (II III VI VII)

→ high contents of manganese (high [Mn]-activity) means high vaporisation losses


Mechanism Map for SFB 76125.08.09, No. 3

Senk, Lob


25.08.09, No. 4

MnMn app ⋅=*MnMnMn xa ⋅= γ

056.0027.0)1(352.0ln 2 ±+−⋅= MnMn Xγ

[3]16001.3

[2]16001.3

[1]15901.38

LiteratureTemperature (°C)Activity coefficient of

Mn

[1] Hultgren, R.; Orr, R. L.; Anderson, P. D.; Kelly, K. K.: Selected Values of Thermodynamik Properties of Metals and Alloys, John Willey, New York, London (1963) pp. 726-732

[2] Bužek, Z.; Schlinderova, V.: Freiberger Forschungsheft B, 117 (1969) pp. 75-90[3] Sigworth, G. K.; Elliott, J. F.: Metal Science, 8 (1974) pp. 298-310

Distribution of iron and manganese activities in the system Mn-Fe (Thermo®-Calc)

vapour pressure pure Mn = 48,7 mbar vapour pressure pure Fe = 0,046 mbar

vapour pressure of the system Fe-Mn

→ pressure below 14,85 mbar would increase manganese vaporisation

pMn* (Fe-Mn) = 14,85 mbar ( chemical composition I)

Calculations; Pressure Dependence

Senk, LobCalculations; Temperature Dependence


Manganese vs. Mn pressure for different Temperatures in the system Mn-Fe (Thermo®-Calc)

→ high temperatures let increase Mn pressure and the vaporisation losses

25.08.09, No. 5

Senk, Lob

Vacuum-Induction-Furnace 4 at IEHK

frequency: 3 kHzmaximum power input: 150 kWvacuum: ≥ 3·10-3 mbar capacity: 100 kgspecial features: adjustable atmosphere

programmable temp.charging during vacuum

features: - online and clean measurem. = Hydris®-System

- steam condenser


25.08.09, No. 6

Experiments; Melting Furnace

→ production of clean high manganese steel→ adjustment of parameters avoiding

high manganese losses

Senk, Lob 25.08.09, No. 7

( ) 543213.210

nnliq

nnn aCTTCpCAmdt

dm+−++⋅=

Experiments; Parameters

Parameters:- melting weight (m)- reaction area (A)- pressure (p)- temperature (T)- activity (a)- convection- atmosphere

Adjustment of the following parameters to decrease manganese losses:

Reasons to decrease manganese losses:

- the manganese dust can damage the vacuumtechniques, see figure

- high manganese losses cause high costs of alloying materials(electrolyt manganese = 4700 Euro / t; stand July 09)


Contamination as a result of manganesevaporisation in the VI 4

→ reduce manganese losses to protect vacuum techniquesand to reduce raw material costs

→ reduce manganese losses by adjustment of melting parameters

Senk, Lob

Manganese losses for different pressures vs. time

→ other parametershave to be constantfor all experiments!

* master thesis D. Rzehak


25.08.09, No. 8

Experiments; Pressure Dependence


→ experiments show a contrary pressure dependence→ possible: the low pressure decreases the convection above the melt

and decreases the vaporisation of manganese atoms

Senk, Lob

pressure 800 mbar pressure 10 mbar

boiler of VI 4 boiler of VI 4

brown deposit

- highly flammable incontact with air

- no melting view“ blind-melting”

black deposit

- lowly flammable incontact with air

- melting view≥ 400 mbar sufficient≥ 150 mbar low vaporisation

EDX at GFE

EDX at GFE


25.08.09, No. 9

Experiments; Pressure Dependence


→ pressure is essential for melting

Senk, Lob

Temperatur

[Mn]-Ist20

21

22

23

24

25

0 20 40 60 80 100

Zeit (min)

[Mn-

Geh

alt (

Gew

.-%)

10001100120013001400150016001700

Tem

pera

tur (

°C)

Temperatur

[Mn]-Ist

20

21

22

23

24

25

80 100 120 140

Zeit (min)

[Mn]

-Geh

alt (

Gew

.-%

)1000

1100

1200

1300

1400

1500

1600

Tem

pera

tur (

°C)

dm/dt (Ar.) = 1,08 Gew.-%/hcomplete = 1,79 Gew.-%

dm/dt (air) = 1,04 Gew.-%/hcomplete = 0,85 Gew.-%

[Mn]-content vs. timefor argon atmosphere


25.08.09, No. 10

Experiments; dependence of atmosphere


[Mn]-content vs. time at air

→ no effect of the atmosphereon manganese vaporisationcan be observed

Senk, Lob

Temperature

[Mn]-current

p=800mbar

[Mn]-setpoint

21

21,5

22

22,5

23

23,5

24

24,5

25

0 5 10 15 20 25

Time (min)

Man

gane

se c

onte

nt (w

t.%)

1300

1350

1400

1450

1500

1550

1600

1650

1700

Tem

pera

ture

(°C

)

[Mn]-setpointTemperature

p=10mbar

[Mn]-current

21

21,5

22

22,5

23

23,5

24

24,5

25

0 5 10 15 20 25

Time (min)

Man

gane

se c

onte

nt (w

t.%)

1300

1350

1400

1450

1500

1550

1600

1650

1700

Tem

pera

ture

(°C

)

[Mn]-content vs. time for 1600 °C

dm/dt (T = 1500 °C ± 30 K) = 2,16 Gew.-%/h= 0,9 Gew.-% (complete)

dm/dt (T = 1600 °C ± 30 K) = 4,32 Gew.-%/h= 1,8 Gew.-% (complete)


25.08.09, No. 11

Experiments; temperature dependence


[Mn]-content vs. time for 1500 °C

→ high melting temperatureslet increase the manganeselosses in the melt

Senk, Lob

200 mm

400 mm

200 mm


25.08.09, No. 12

Experiments; Convection (thermal)


Further experiments for the determination of manganesevaporisation in the system

Fe-Mn-C:- Application of a cover to avoid

cold sources

Condenser in the VI 4 at IEHK

→ elimination of thermal convectionabove the melt to decrease manganese losses

Senk, Lob 25.08.09, No. 13


Abstract

- Melting in the System Fe-Mn-C with [Mn]- Contents of 12-30 wt.% is leading to Manganese Losses

- Manganese Losses depends on the high Vapour Pressure

- the Vapour Pressure depends on Parameters like Temperature, Pressure, Activity, Convection

- Experiments show a contrary Pressure Dependence

- Atmosphere has no effect on Manganese Losses

- high Temperatures let increase the Manganese Losses

- further Experiments should shoe the Effect of thermal Convection onManganese Vaporisation in the System Fe-Mn-C

Senk, Lob


25.08.09, No. 14

Thank you for your attention

Institute for Ferrous Metallurgy RWTH Aachen University

Univ.- Prof. Dr.- Ing. D. Senk ([email protected])

Dipl.- Ing. A. Lob ([email protected])

www.iehk.rwth-aachen.de

http://abinitio.iehk.rwth-aachen.de

Senk, Lob

Mn-Verdampfung

(atm) LuftT=1600 °Cp = 1 bar

I, Magma 1

(atm) ArgonT = 1600 °Cp = 0,8 barI, Versuch 8

(T) T = 1600 °Cp = 0,8 barI, Versuch 8

(T) T = 1500 °Cp = 0,8 bar

I, Versuch 14

(p) T = 1500 °Cp = 0,8 bar

I, Versuch 14

(p) T = 1500 °Cp = 0,01 barI, Versuch 16

(a) T = 1500 °Cp = 0,01 bar

III, Versuch 19

(a) T = 1500 °Cp = 0,01 bar

VIII, Versuch 25

(a) T = 1500 °Cp = 0,01 barI, Versuch 16

(k) T = 1500 °Cp = 0,01 bar

I, Versuch x (Spülstein)

(k) T = 1500 °Cp = 0,01 bar

I, Versuch x (Spülst., Deckel)

(p) T = 1500 °Cp = 0,4 bar

I, Versuch 20

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SFB 761 „Stahl ab initio