Vaccume Degassing

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Project Guide:-Mr. Naveen SinghManager QA (SMS)

Presented By:-Rakesh Yadav (4636)Akash Sharma (4635)Manoj Sahu ()Bhushan Sahu ()Umed Diwan ()

JAYASWAL NECO INDUSTRIES LIMITED

SILTARA , RAIPUR (C.G.)

MINOR PROJECT PRESENTATIONON

VACUUM DEGASING

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Phases In Steel Making

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Blast FurnaceHot Metal Chemical Composition C% - 4 Si% - 0.8 S% - 0.06(max) Mn% - 0.5

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Electric Arc Furnace EAF is prime station of SMS. It is

melting unit of SMS. It’s capacity is 40 ton.

Decarburization & Dephosphorization of steel is carried out by oxidation process.

Basicity of slag is maintained between 1.8 to 2.5 .

Impurity of steel in the form of slag are drained out through slag door.

Estimated oxygen is blow to get desired tap carbon.

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Approximate 80-90% chemistry adjustment is done at EAF during tapping.

EAF is backbone of SMS. Productivity of shop significantly depend upon the performance of EAF.

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Ladle Refining FurnaceLRF is for secondary steel making. Almost

100% chemistry is met here.Steel purification and homogenenization is

accomplished. Refining of steel is done at LRF through

deoxidation and desulphurization. Continuous Argon purging of hot metal is

done. Basicity of slag is maintained 2.5 to 3.0 to

achieve FeO level less than 1%.Calcium treatment is done to change the

morphology of inclusion.

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Normal process time at LRF is 50-60 minutes.

After the required alloy addition heat is transferred for CCM or VD as per requirement.

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Vacuum Degasing A Vacuum Degassing System or Degasser

is used in the secondary refining of steel - subjecting molten metal to a vacuum to remove oxygen, hydrogen and nitrogen to produce ultra-low carbon steel for the automotive, electrical, construction, and rail markets. Vacuum degassing is normally performed in the ladle and the removal of dissolved gases results in cleaner, stronger, higher quality, more pure steel.

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Degasser Principle:

Sieverts law:- Dissolution of diatomic gasses in

steel is directly proportional to partial pressure.

[hH]^2 =Kp H2

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Sources of inclusion of gases:1.Hydrogen : # By absorbed moisture

associated with the raw materials (Lime) used in steelmaking.

# By hot metal (2–5 ppm) and scrap (2–7 ppm).

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2. Nitrogen: # By atmosphere (Mainly)

through air bubbles entrained during tapping.

# By Nitrogen impurities of ferroalloys.

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3. Oxygen: # By Oxygen blowing in furnace. # By atmospheric exposer.

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Effects of inclusion of gases Hydrogen :- Hair Cracks. Nitrogen :- Surface Cracks. Oxygen :- Blow Holes & Pin Holes.

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VACUUM DEGASSING PROCESSES :

Vacuum degassing is practiced in the steel industry for several purposes. They are : -

To remove gases.To improve cleanliness by inclusion

floatation.To produce steel of low carbon content ( <

0.03%)To maintain homogeneity of temperature

and chemistry.To control pouring temperatures, especially

for continuous casting operations.

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Vacuum degassing processes, in the broadest sense, refer to the exposure of molten steel to a low-pressure environment to remove gases (chiefly hydrogen and oxygen) from the steel. The effectiveness of any vacuum degassing operation depends upon the surface area of liquid steel that is exposed to low pressure and slag’s fluidity obtained from LRF.

Hydrogen and Nitrogen removal is a diffusion and partial pressure phenomenon. Oxygen removal is a function of chemical reaction of oxygen with carbon and the partial pressure of carbon monoxide.

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Introduction to VD of JNILMake – METECConsisting of six steam ejectors with

three condensers for vacuum creation.VD also have O ring for sealing of

chamber.Cover car with heat shield and

flooding valve.Argon purging line.Wire injection machine.Emergency hole.

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Steam Line:-

VD Line Diagram

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Ejector valve opening sequence:-EJECTORS PRESSURE

TIME1. 4+4A 735-200 Torr

1.5-2 min2. 3A+3+4A+4 200-65 Torr

1 min 3. 4+3+2 65-6 Torr

2 min4. 4+3+2+1 6 -0.4 Torr

30-60 sec

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Argon Purging:-

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Water Line:-

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Holding time norms for different grades:-

Grade Holding Time

1.Ball Bearing Grade 17-20 min (SAE 52100)

2. Free Cutting Steel No holding (12L14 & EN-1A) Only 5 min

VD process

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3. Semi Free Cutting No holding

Steel Only 5 min

(EN8M & EN15AM) VD process

4. Alloy steel & all carbon 10 min

steel

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Example For Ball Bearing SteelInclusion at LRF- Oxygen- 20-30 ppm Hydrogen- 1.52 ppm Nitrogen- 80-90 ppm After VD- Oxygen- 10 ppm Hydrogen- 1.1-1.2 ppm Nitrogen- 50-60 ppm

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VD TREATMENT PROCESS VD treatment to be done after achieving

vacuum of 1 torr for specified holding time.After VD treatment send sample for

chemistry confirmation and take temperature.

Feed Al wire as per chemistry required.Then add Ca-Si wire.Now add alloys as per chemistry.Add 120kg Of RADAX to prevent temp loss.Then send final sample and take

temperature.Lift heat for CCM.

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Different Grades & Their Target Composition

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Grade:- EN1A(Free Cutting Steel)# Liquidus Temperature:- 1516 Deg.

Chemical Compositions At VD

C% .07

Mn% 1.15

P% .60

S% .275

Si% .04

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Grade:- 16/20 Mn Cr5

# Liquidus Temperature:- 1509 Deg.


C% .18

Mn% 1.15

P% ---

S% .025

Si% .2

Cr% 1.06 Al% .025

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Grade:- SUP 11A # Liquidus Temperature:- 1516 Deg.


C% .59

Mn% .85

P% ---

S% ---

Si% .25

Cr% .85 Al% .025 B% .0025

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Grade:- EN 353 # Liquidus Temperature:- 1511 Deg.


C% .16

Mn% .75

P% ---

S% .025

Si% .25

Cr% .77 Ni% 1.0 Mo% .11 Al% .025

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Grade:- 12L14(Free Cutting)# Liquidus Temperature:- 1516 Deg.


C% .07

Mn% 1.15

P% .050

S% .275

Si% .04

Pb% .25

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Grade:- 15B25



C% .26

Mn% 1.02

P% ---

S% ---

Si% ---

Cr% .17

Al% .025

Ti% .025

B% .0027

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Grade:- 17 Cr 3# Liquidus Temperature:- 1514 Deg.


C% .17

Mn% .75

P% ---

S% .025

Si% .2

Cr% .75 Al% .025

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Grade:-SAE 19 Mn B 4 # Liquidus Temperature:- 1508 Deg.

Chemical Compositions At VD C% .25

Mn% 1.05

P% --- S% --- Si% .2 Cr% .5 Al% .025 Ti% .025 B% .0027

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Grade:- C-70# Liquidus Temperature:- 1492 Deg.


C% .69

Mn% .75

P% .02

S% .02

Si% .28

Al% .015

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Grade:- EN 8A# Liquidus Temperature:- 1502 Deg.


C% .35

Mn% .80

P% ---

S% .025

Si% .25

Al% .025

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Grade:- EN 15A


Chemical Compositions At VD C% .37

Mn% 1.5

P% ---

S% .020

Si% .25

Cr% .08 Al% .025

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Grade:- EN 18C



C% .37

Mn% .75

P% ---

S% .025

Si% .25

Cr% 1.00 Al% .025

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Grade:- SUP 7# Liquidus Temperature:- 1470 Deg.


C% .57

Mn% .85

P% ---

S% ---

Si% 1.95

Cr% ---

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Grade:- SUP 9A



C% .60

Mn% .85

P% ---

S% ---

Si% .25

Cr% .85 Al% .025

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Grade:- 55 Si 7# Liquidus Temperature:- 1474 Deg.


C% .55

Mn% .85

P% ---

S% ---

Si% 1.75

Cr% ---

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Grade:- SAE 9254# Liquidus Temperature:- 1470 Deg.


C% .55

Mn% .75

P% ---

S% ---

Si% 1.45

Cr% .70

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Grade:- EN 8M# Liquidus Temperature:- 1494 Deg.


C% .38

Mn% 1.18

P% ---

S% .15

Si% .20

Cr% ---

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Grade:- EN 18/41 Cr 4# Liquidus Temperature:- 1498 Deg.


C% .41

Mn% .75

P% ---

S% .025

Si% .2

Cr% 1.00 Al% .025

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C% .41

Mn% 1.60

P% .02

S% .085

Si% .25

Cr% .13 Al% .012

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C% .43

Mn% 1.50

P% .02

S% .02

Si% .28

Cr% .13 Al% .025

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Grade:- EN 18D# Liquidus Temperature:- 1496 Deg.


C% .40

Mn% .73

P% ---

S% .025

Si% .25

Cr% .98 Al% .025

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Grade:- EN 19/SAE 4140(WRM)# Liquidus Temperature:- 1495 Deg.


C% .4

Mn% .78

P% ---

S% ---

Si% .2

Cr% 1.00 Mn% .22 Al% .025

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Grade:- SCM 420H# Liquidus Temperature:- 1512 Deg.


C% .19

Mn% .65

P% ---

S% .025

Si% .25

Cr% 1.00 Mo% .17 Al% .025

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Grade:- S 55 C# Liquidus Temperature:- 1495 Deg.


C% .55

Mn% .70

P% ---

S% .025

Si% .25

Al% .025

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Grade:- S 45 C# Liquidus Temperature:- 1495 Deg.


C% .44

Mn% .75

P% ---

S% .025 Si% .2

Cr% .025

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ADVANTAGES

Production of high quality steel. High Control on chemistry. Minimum defects.

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LIMITATIONS

1.Low capacity ladles Ladle No. Capacity 1-6 39 to 40

ton (max)

7 & 8 42 ton

Solution:- Placed order for 42 tons capacity ladle.

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2. Time consuming:- VD is lengthy process, hence

some times we have to hold the EAF. Because single LRF is unable to prepare heat.

Solution:- Ongoing project of second LRF,

so that we don’t need to hold EAF.

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VD ABNORMALTIES

1.Vacuum delay due to leakage. Actions:- (a) Check point (b) O ring check (c) Smoke Test (d) Checking of spring of

NRV(Non Returning Valve)

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2. Ladle lining erosion and puncher This mainly occurs in slag

zone.

Action:- (a) Emergency hole (b) Lift the ladle in tilt

position as soon as possible.

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THANK YOU

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Vaccume Degassing

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