RH-Degasser Final Version 2015

RH-DEGASSER

SOUTH AMERICA & CARIBBEAN

Sample Brochure Created By: Heinz Wieduwilt / Sales & Marketing Director

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Basics of Vacuum Degassing

History:

In the late 1950‘s development of recirculating systems:

DH (Dortmund Hoerde) and later RH (Ruhrstahl Heraeus) process due to initial need for low

hydrogen steels Early 19070‘s trend to ULC (ultra low carbon) steels with C<30ppm, IF (interstitial free) steels with N&C<30ppm

Metallurgical functions:In deep vacuum reaction of C + FeO+ -> Fe + CO results in

Carbon: <15ppm (0.0015%) Oxygen: <10ppm (0.0010%)Final de-O2, de-N2, de-H2, alloy-adjustment, steel-cleanliness (inclusion-removal)Precise alloying of expensive alloys such as Ti, Vn, Nb (microalloys)

Typical RH Steel grades:Heavy Plate & Mild Strips:

H<2ppmRail Steel: H ~1-2ppmCase hardening steel, heat treatable steel, ball bearing steel: C<10ppm, H<2ppm. Tube steel, Electric steel, IF-steel: C<10-30ppm.

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Degassing Processes

Recirculating Processes:

DH = Dortmund Hörde

DH-OB = DH with Oxygen Blowing

RH = Ruhrstahl Heraeus

RH-OB = RH with Oxygen Blowing (with tuyeres in lower vessel)

RH-OTB = RH with Oxygen Top Blowing (same RH-KTB)

RH-KTB = RH Kawasaki Top Blowing (oxygen, powders)

RH-PB = RH with Powder Blowing (desoxydants, alloys)

Non-Recirculating Processes:

VOD = Vaccum Oxygen Degassing

VD = Vaccum Tank Degassing

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Comparison of various Degassing Systems

Metallurgical Process RH-OB RH VOD VD LF

Decarburization level (ppm) 10-15 15 20-30 30-40 30-40

Decarburization rate Highest Satisfactory for Highlow carbon

Decarburization time to 10-15 12-15 15-18 15-20 15-2050ppm [min]

Hydrogen, Nitrogen removal

Inclusion Removal

Desulfurization

Aluminum heating yes no yes no no

Relative Capital Cost 1.0 0.7-0.8 0.4-0.6 0.4-0.5 0.3-0.4(RH-OB = 1.0)

Maintenance Cost Decreasing

decarburization(rarely practised)

All systems are reasonably satisfactory

Only possible with lime-injection or RH-PB

Excellent desulfurizationbut must be separate from

Type of Degasser

Approx. 20-30% slowerthan RH, RH-OB,VOD

All systems improve cleanliness, VOD, VD & LF require rinse-cycle

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Principle of RH-Degassing

RH-OB process

RH-OTB RH-KTB process

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RH-OB Plant

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Basics Metallurgical Process / RH-degasser

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Basics Metallurgical Process / RH-degasser

Process: -- 2 snorkels immersing into the steel melt - Vacuum-evacuation of the main chamber - Steel is rising into the lower vessel equivalent to ferrostatic pressure at 1 mbar to

~1.4m height - Circulation-effect is produced by bubbling Ar in the inlet-snorkel - Dissolved gases & Ar released into the vacuum - Steel accelerates through the inlet-snorkel (~1.5m/sec or ~180mt/min) -> heavy

erosion - Steel returns to ladle trough the outlet snorkel - Additions are made through 2-chamber vaccum-lock & alloy chute - Temperature-loss is low (RH-vessel preheated) -Advantages: -- Shortening of the primary metallurgy process

short treatment times -> high availability - Achievable metallurgical results:

~1.5ppm H, ~15ppm C, ~10ppm O - High alloy-recovery yields - Homogenisation, improved cleanliness

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1 bar (1000 mbar)

Steel bath

Deep vacuum (2 mbar)

Steel bath

Picture 1: Balance of gas between steel bath & atmosphere -> no combination

Picture 2: Imbalance of gas between steel bath & atmosphere -> no combination due to lack of nucleation

Picture 3: Theoretical homogenous nucleation -> too slow combination

Degassing behavior of dissolved gases (example H)

Homogenous nucleation

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Degassing behavior of dissolved gases (example H)

Picture 4: Heterogenous

Picture 5: Heterogenous nucleation at the surface of an Ar-bubble -> improved steel

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RH Circulation Rate

The circulation rate W is a function of some parameters like snorkel diameter, gas flow-rate and height from argon nozzle to refractory bottom

W = 0,0038 x DE0,3 x DA

1,1 x G0,31 x H0,5 [mt/min]

W = Circulation rate in mt/min. DE = Inner diameter of the inlet-snorkel in cm. DA = Inner diameter of the outlet-snorkel in cm.

G = Argon flow-rate in Nl/min

Trends:

W → treatment time ↓ → achieve quicker H, O, C, N – levels

Wmax ~ 1.5m/sec

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Vacuum De-oxidation in RH or VD (fully killed

Pre

ssur

e in

mba

r, O

xyge

n in

ppm

Total oxygen content

dissolved oxygen

Pressure

Treatment-time in min.

‘Light Treatment’: -- cost-savings by reduced Al-consumption for fully-killed steels

- 1st step: oxygen-reduction by CO-recombination under vacuum → after 10mins O<20ppm

- main reduction of oxygen already at pressure between 50-5mbar - Improved cleanliness: under further treatment also other non-metallic

inclusion swept to slag

- 2nd step: Al-killing → O<10ppm

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Vacuum Decarburization (ULC- & IF-steels)

- extremely low C-contents < 15ppm possible - carbon removal follows a logarithmic time law: - Ct = Co x exp (-k x t)

Ct = carbon level at the time t, in ppm Co = initial carbon level, in ppm t = treatment time, in min. k = decarb. factor in 1/min, usually 0.1 - 0.2

k ~ W (circulation rate) ~ Ar gasflow & snorkel ID

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Examples: k=0.2 → C(10mins) = 30ppm → C(16mins) = 10ppm k=0.1 → C(32mins) = 10ppm

Realistic figures little slower

Vacuum Decarburization (ULC- & IF-steels)

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Vacuum Decarburization with RH-OTB (ULC-steels)

Carbon- & Oxygen contents before (open circles) and after (full circles)

as obtained by RH-OTB treatment

‘Forced Decarburization’: -

- Effective decarburization under constant oxygen-supply→ even high C-contents no problem→ final deox. with Al & reheating

-Advantage of RH-OTB: - steel can be tapped with higher C-

content (100-300ppm) → BOF/EAF treatment-time shorter + higher Fe-yield (lower FeO-slag) → lower O-content in tapped steel

Oxygen-Rule: - When initial oxygen is high also final

oxygen is high (case A) - When initial oxygen is low also final

oxygen is low (case B)

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Vacuum Hydrogen-removal (heavy plate steel)

∆H %

=

Hydrogen-removal for 2 initial H-values & 2 Ar-flowrates

at vacuum of 2mbar

- Hydrogen-removal essential for large forging & heavy plate steel(too ↑ H can result in sudden failure)

- H-removal follows a logarithmic law: ---- [H]f = H-content after degassing - [H]I = H-content before degassing - kH = constant for H-removal - t = time -- Results: - Fully killed steel: Hf 1.4-2.0 ppm - Part. killed steel: Hf 0.8-1.3 ppm - Achieving same degree of H-removal takes longer for lower initial H-content - Doubling of Ar-flowrate just saves 2mins achieving same results

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Wear-factors on RH-degasser

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RH Drying & Heat Up Diagrams

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Heat-Up of RH/DH Vessel

Heating Up

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Heat-up curve after installation and repair

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TYPES OF MAGNESIA CHROMITE BRICKS

A direct-bonded magnesia chromite brick is characterized by an excellent thermal shock resistance due to its heterogeneous microstructure. This brick type offers a high proportion of chromite – periclase (MgO) direct bonding which additionally leads to a high hot strength.

OXICROM is a pretreated co-clinkered magnesia chromite sinter. Based on the optimal and very intensive distribution of the chromite spinel within the microstructure the brick provides high corrosion resistance especially against acidic slag. Furthermore the high proportion of direct bonding results in a high hot strength.

The very high density of the magnesia chromite fused grain, the highly compact microstructure together with strong ceramisation and evenly distributed chromite spinel leads to an excellent corrosion resistance. These bricks are the preferred product for areas with highest corrosion attack.

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TECHNOLOGY & KNOW-HOW

In order to adapt our products to the individual requirements of our customers´processes and the steel shell geometry, our construction office is equipped with the most modern CAD systems. Our construction engineers, many of whom also act as service engineers, therefore implement their experiences gained in practice, in the

We are the reliable refractories partner for leading OEM (Original Equipment Manufacture) companies. Our lining systems are technically sophisticated and state of the art.

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JY REFRACTORIES CFD

Research and development Proper mixing in the steel melt improves the efficiency of the RH degasser process. Mixing and phase dispersions are influenced by turbulent fluid flow in the bath. A quantitative approach is based on fluid mechanics – especially as related to turbulent flow. Such computations involve computer-oriented numerical methods.

CFD-modelling is employed for:

■ Optimizing the refractory design ■ Interpretation of results ■ Process prediction

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Application technology

Our engineers’ expertise is available to solve customers‘ problems world-wide.

The identification and analysis of customer problems are key input factors in our product development.

Our product portfolio is keyed to the different customer requirements. We provide the expertise for RHI degassers from the lining to the gunning

Our experienced supervisors are on hand to meet our customers’ needs:

■ Training the customers’ refractories division ■ Supervising installations ■ Commissioning ■ Introduction and assessment of new products ■ Devising customer-specific solutions to refractories-related application issues

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RH GUNNING MANIPULATOR

for hot or cold refractory repair for snorkels in vacuum plants automatically spraying inside more economical

Advantages ■ Reduces physical strain on operating personnel ■ Shorter repair times ■ Minimum preparation ■ Higher performance of the lining ■ Easy to use ■ Low wear and tear part costs ■ 90° deflecting funnel provides optimal gunning position and reduces the amount of rebound material

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Description:

The degassing gunning machine is built for automatic/manual spraying inside of the nozzles of RH-Degassing Units.

After spraying the inside of one nozzle the spraying unit will be rotated by 180 degrees. In this position, the remaining untreated surfaces of the degassing nozzles may be treated the same way as mentioned above,

Dimensions

Height approx. 4500 mm Working area width approx. 2500 mm Working area depth approx. 2500 mm Weight approx. 2000 kg

Technical Data

Voltage 3x200-500 V

Frequency 50/60 Hz

Installed power approx. 10 kW

Control voltage 24 V DC

Controlled by PLC (Siemens)

Air pressure 6 bar

Air consumption approx. 8 m3/min

Water pressure min. 4 bar

Water consumption approx. 350 l/h

Operating Parameter setting automatic mode inside gunning

Remote control manual mode


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A new gunning technology of VELCO GmbH

By means of this new technology the well-proved dry gunning process gets an efficient progress regarding less dust nuisance, reduced rebound and more intensive mixing.

At the GUNMIX® system (EP 1153861) the gunning material is moistened in the mixing head by a fog of compressed air and water. By means of this unit the development of dust and rebound is reduced considerably. The water addition is exactly adjusted and can be measured. The gunning capacity is exactly adjusted by a gear motor with speed regulation. This makes it possible to keep an exact mixing ratio of gunning material and water.

New fields of application arise when LCC-, ULC- or NCC-materials will be applied in the dry gunning procedure. Due to the better moistening by GUNMIX® these materials can be processed by adding a small amount of liquid binding agent (water glass, acid or water). Compared with the conventional installation by casting, the comprehensive encasing works (building of templates) are omitted.

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With GUNMIX® the gunning water is dispersed by compressed air, the water-drops will be atomized and distributed homogeneously in the mixing head. Thats why even finest material components can be moistened. (see picture with / without GUNMIX®).

GUNMIX - Mixing nozzle with hand piece and Spraying nozzle


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Advantages by using the GUNMIX®-system:

better working conditions due to less dust development better gunning result due to better moistening and non- arising of nests savings of costs due to less rebound

Now slurry materials can be worked in the dry gunning process, i. e. less water, only 15 % instead of 25 %, same physical values, rebound less than 5 %, less working costs.

By means of the GUNMIX®-system low cement castables must no longer be pumped, but can be worked in the dry gunning process; less personnel costs at exactly the same material characteristics.

Conventional gunning concrete can be applied with exact water quantities, less rebound

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PREFABRICATED snorkels

JL’s ready-for-use components – for your convenience:

■ Fast installation ■ Made by specialists ■ Ready for use, preheated

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PREFABRICATED Alloy Chute

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MgO%

Al2O3

%CaO%

SiO2

%Fe2O3

%Cr2O3

%

Bulk density g/cm3

Por. Vol%

CCS N/mm2

69.5 4.0 0.9 0.7 6.4 18.5 3.24 15.0 45

63.5 5.4 0.8 0.6 10.3 19.0 3.14 17.0 50

57.0 6.4 0.8 1.1 11.7 22.5 3.30 15.0 45

57.0 6.5 1.1 0.5 12.5 21.0 3.22 16.5 50

60.4 6.3 0.9 1.4 12.0 19.0 3.20 16.5 60

--- 41.0 --- 54.0 1.5 TiO2 1.7 2.23 16.5 60

0.5 35.0 0.4 60.0 2.0 K2O 2.8 1.05 --- 6

--- 38.0 0.7 49.0 1.0 0.90 --- ---

--- --- 43.0 44.0 --- --- 0.24 --- 1.4

--- 44.0 --- 56.0 --- --- 0.10 --- ---

--- 44.0 --- 56.0 --- --- 0.13 --- ---

--- 63.0 --- 37.0 --- --- 0.14 --- ---

BONDING

93.8 0.2 0.8 0.6 0.6 1.9 phosphate

91.0 0.6 1.6 1.9 1.0 2.0 phosphate

53.4 6.4 1.2 0.6 19.0 18.0 phosphate

91.4 0.1 1.2 0.6 0.5 3.9 phosphate

--- 46.0 0.3 44.0 2.0 --- chem.ceram.

--- 95.0 4.1 0.6 0.5 TiO2 0.3 hydraulic

1.5 94.5 --- 0.2 1.2 --- hydraulic

--- 97.0 2.5 0.1 0.1 --- hydraulic

81.0 2.8 11.0 1.1 TiO2 2.7 hydraulic

--- 81.0 --- 8.0 1.0 --- chem.ceram.

--- 79.5 --- 13.0 1.7 --- chem.ceram.

88.0 1.0 4.3 5.4 0.4 P2O5 0.7 phosphate

TYPE

ramming mix

gunning mix

castable

mortar

gunning mix

castable

castable

castable

gunning mix

mortar

CHEMICAL PROPERTIES [wgt %] PHYS. PROP.

BRICKS

PRODUCT

ramming mix

ramming mix

INSTALLATION & REPAIR MIXES

Product Guide

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MCr-BrickMortarRamming MixExpansion GapCastable

Fireclay BrickMortar

Insulation BrickInsulation Board

Mortar

MCr-Brick

MortarRamming MixExpansion Gap



Mortar

Opening BlockMCr-BrickMortarRamming Mix


Insulation Board

Mortar

Elbow, Gas Duct

Safety Lining

Upper Vessel

Alloy Chute & Burner Opening

Insulation Lining

Safety Lining

Working Lining

Working Lining

Working Lining

Safety Lining

Insulation

Insulation Lining

Product Guide

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MCr-BricksElectro-FusedMCr-BricksDirectbondedMortarRamming Mix

Expansion Gap

Fireclay BrickMCr-BrickMortarRamming Mix


Mortar

MCr-BricksElectro-FusedMCr-BricksDirectbondedMortarRamming MixExpansion Gap

Alumina Mix

Alumina Mix

MgO-MixAlumina Mix

Safety Lining

Insulation Lining

Snorkel Maintenance

Snorkels Working Lining

Backfilling Mix

Outside Casting Mix

Product Guide

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Snorkels

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RH Estimated Lifetime & Consumption / During start up phase

Conditions: Snorkels welded to vessel -> not changeable Operation: 1.-3. month: stop & go, cannot be defined 4.-12. month: 20heats/day, some interruptions Standard: 25heats/day, continuous operation

Life-Time Performance

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CONDITIONS FOR ACHIEVING HIGH REFRACTORY LIFETIME

■ Argon supply should not be disconnected during the vacuum treatment ■ Temperature of liquid steel should exceed liquidus by at least 50 °C ■ Temperature of liquid steel should not exceed solidus by more than 120 °C before the treatment beginning ■ Treatment time should not exceed 40 minutes per heat ■ Slag basicity (C/S) should be in the range of 1.5 to 2.5 ■ Slag has to be viscous, not solid ■ Snorkels have to be gunned every 4-5 heats ■ Inner temperature of the vessel must not be lower than 900 °C ■ Snorkel and flange should be made of P265GH (boiler plate HII) ■ Minimum 7 heats per day

HIGH REFRACTORY LIFETIME

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Snorkel Skull Cleaning

Snorkel Scull Cleaning Device ‘Wright Rockmaster’ mounted on the maintenance-platform

HIGH REFRACTORY LIFETIME

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Refractory Diagnostics

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Hardware components for diagnostics system

Control and visualization unit

Measuring unit

Inside view of the measuring unit


Documents

RH-Degasser Final Version 2015