HYDROGEN CONTROL OF LARGE BOTTOM POURED FORGING INGOTS AT ELLWOOD QUALITY STEELS Bjorn Gabrielsson – Ellwood Group, Inc. Brendan Connolly – Ellwood Quality Steels Steve Lubinski – Ellwood Quality Steels Sean Cowden – Ellwood Quality Steels Hongliang Yang – ABB R&D Metallurgy

Outline Evolution of vacuum treatment of liquid steel New Castle Complex EQS Production Flow and KPI Sandwich Pouring of Ingots >47 Mton Hydrogen in Steel EQS Vacuum Station CFD Simulation Model Validation Hydrogen Pick-up during Bottom Pouring Conclusion

Revolution of Vacuum Treatment of Liquid Steel 1911 German chemist Albert Sievert published his work on the solubility of gases in metal 1950 Bochumer-Verein (Germany), first vacuum tank FAILED 1952 Bochumer-Verein (Germany), first stream degassing 1955 Air Liquide (France), development of porous plug 1956 Bethlehem Steel (USA), first multi-stage steam ejector vacuum pump 1958 Finkl (USA), VTD with He inert gas lance stirring 1959 Dortmand-Hoerder vacuum lift process (Germany) 1959 Ruhrstahl-Heraeus vacuum lift process (Germany) 1964 Germany/USA simultaneously developed ladle slide gates 1965 ASEA-SKF Process (Sweden), vacuum treatment with electromagnetic stirring THE REST HAS JUST BEEN A LONG EVOLUTION

New Castle, PA Complex

New Castle, PA Complex

EQS Production Flow and KPI Value EAF Gross T-T-T 52.7 minutes/heat EAF Power On Time 36.1 minutes/heat EAF Power Off Time 16.6 minutes/heat Productivity 27.3 heat/day Dec 1985 – August 2018 more than 8,300,000 Mton of forging and ring rolling ingots

Sandwich Pouring Process for Ingots >47 Mton Implemented at EQS in 2015 Up to four ladles of steel into one ingot Maximum ingot produced to date 170 Mton with 4x ladles

Hydrogen in Steel

Hydrogen in Steel

EQS Vacuum Station

CFD Simulations PARAMETER CASE 1 CASE 2 CASE 3 Heat size, Mton 45 EMS type None ORT34 EMS Current, A 1000 1350 EMS stir direction Up Vacuum pressure, mbar 1.0 Ar flow rate, Nl/min 80 Slag amount, kg 600

CFD Simulations R/2

CFD Simulations – Top Surface Velocity m/sec m/sec m/sec

CFD Simulations – Bulk Metal Velocity

CFD Simulations – Argon Bubble Dispersion and Velocity m/sec m/sec m/sec

CFD Simulations - Summary RESULT CASE 1 (Ar-gas only) CASE 2 (Ar-gas + 1000A EMS) CASE 3 (Ar-gas + 1350A EMS) Stirring power density, W/ton 65 600 700 Free metal surface, % 7.4 22.5 27.9 Average surface velocity, m/s 0.14 0.41 0.53 Average bulk metal velocity, m/s 0.11 0.48 0.71 Bubble dispersion and residence time Low Medium High Thanks to increased stirring power: Free metal surface 3.8 times larger Surface velocity 3.8 times larger Bulk metal velocity 6.5 times larger Argon bubble dispersion and retention time improved significantly

Model Validation – Mixing Time

Model Validation – Free Metal Surface

Model Validation – Hydrogen Results

Hydrogen Pickup – Secondary Steelmaking Comparison of H pickup for heats tested after vacuum treatment and heats tested just before bottom pouring On average <0.1 ppm difference – virtually no H pickup during secondary steelmaking

Hydrogen Pickup – Data Analysis Data collection for > 30,000 heats produced at EQS Level 2 process control system combined with “Business Intelligence” software for massive data mining Analysis of in-process and final hydrogen content against large set of possible variables

Hydrogen Pickup – Ladle Refractories 5+ heats on all components = baseline (0% contribution to hydrogen pickup) Non-shrouded heats excluded, Total 34,519 heats

Hydrogen Pickup - Atmosphere 100% reference is average of 20,338 shrouded heats produced since Ar-shroud upgrade (2015) Non-shrouded heats total 1,939 over same time period

Hydrogen Pickup – Bottom Pour Tile Mortar

Hydrogen Pickup – Teeming Flux

Ultra Low Hydrogen Practice Careful ladle planning ensures inner nozzle, slide gate and collector nozzle are not new Vacuum treatment at < 1 mbar with combined EMS and Ar-gas stirring Strict limitation on alloying and slag additions after vacuum treatment Argon Shrouding of the lower ladle stream Ladle-to-ladle shrouding of the upper ladle stream(s) Preheating of bottom pour refractory to 500°C Preheating of ingot mold Flux addition by direct pouring into hot mold for residual moisture removal AVERAGE OF 35% REDUCTION IN HYDROGEN PICKUP

Conclusion

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