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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
RH GUNNING MANIPULATOR
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RH GUNNING MANIPULATOR
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
RH GUNNING MANIPULATOR
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RH GUNNING MANIPULATOR
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
Fireclay BrickMortar
Insulation BrickInsulation Board
Mortar
Opening BlockMCr-BrickMortarRamming Mix
Fireclay BrickMortar
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
Insulation BrickInsulation Board
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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Refractory Diagnostics
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Hardware components for diagnostics system
Control and visualization unit
Measuring unit
Inside view of the measuring unit
Refractory Diagnostics