Liquid Metal Processing & Casting Conference (LMPC 2022): Electoslag Refining I
Program Organizers: Matthew Krane, Purdue University; Mark Ward, University of Birmingham; Abdellah Kharicha, Montauniversität

Tuesday 8:00 AM
September 20, 2022
Room: Grand Ballroom
Location: Bellevue Hotel

8:00 AM Introductory Comments

8:05 AM  
Electrode Immersion Depth Influence in the ESR Process : an Experimental and Numerical Study: Jeremy Chaulet1; Sylvain Charmond2; Bernard Dussoubs1; Abdellah Kharicha3; Stéphane Hans2; Alain Jardy1; 1Institut Jean Lamour; 2Aubert & Duval; 3Christian Doppler Laboratory for Metallurgical Applications of MHD
    In the Electroslag Remelting (ESR) process, the electrode tip is plunged into the slag bath. Its immersion depth is a key parameter which has a strong influence on electromagnetic phenomena and coupled transfers within the slag. Associating experimental trial remeltings and numerical modeling of the process, some specific impacts of electrode immersion depth are highlighted. The link between electrode immersion and slag resistance is discussed for three regimes, among which electrode excursion plays a specific role. The influence of electrode immersion depth on ingot solidification, especially regarding the quality of ingot skin, is addressed.

8:30 AM  
Validation of Electro-slag Remelting (ESR) Process Simulations for HAYNES®282® Alloy Slab Ingots: Ram Krishnamurthy1; Michael Fahrmann1; 1Haynes International
    Results from a detailed validation study of the process simulation (using the commercial software MeltFlow-ESR®) of the ESR of a 282 alloy 10” thick slab ingot will be presented. As part of this study, Mo pellets were dropped into the crucible during the ESR of this slab at times chosen to reflect the initial transient, steady state and hot-topping stages of the process. The shape and temporal evolution of the solidification front as reconstructed from the locations of the Mo pellet markers compares favorably with predictions from the process simulation. Variations in ingot microstructure (primary / secondary dendrite arm spacings) with spatial extent across the ingot obtained by metallographic analysis are also compared with those predicted by the empirical dendritic kinetics prescriptions employed by MeltFlow-ESR®. Inferences drawn from these results relating to the effectiveness of the process simulations to faithfully capture experimentally observed characteristics will also be presented.

8:55 AM  
Swing Control in ESR- Challenges, Influences and Outlook on a Key Control Parameter to Obtain Superior Ingots: Manfred Ramprecht1; Michael Kubin1; Alexander Scheriau1; Harald Holzgruber1; 1INTECO melting and casting technologies GmbH
     Beside a precise melt rate control, the immersion depth of the electrode in the slag bath represents the most decisive parameter for process stability and subsequently superior product ESR quality. To control the immersion depth in INTECO´s industrial ESR-furnaces the “swing” of the bath-resistance is applied. Deriving the immersion depth from the slag bath resistance calculated from melting power and current is one of the key control mechanism ESR. Depending on the furnace size and configuration (selected type and frequency of power supply) various influences have to be taken into account.This papers gives an overview on the basic philosophy of swing calculation and control and detailed measurements are presented to verify the control algorithm. Based on operational experiences of ESR furnaces ranging from 5t-250t of ingot weight and based on different power supply systems installed, the dependency of resistance and resistance variation on the immersion depth is discussed.

9:20 AM  
Impact of Fill Factor on Electro-slag Remelting Operations: Paul Jablonski1; Martin Detrois1; 1National Energy Technology Laboratory
    Vacuum induction melting (VIM), electro-slag remelting (ESR) and vacuum arc remelting (VAR) are all techniques used to make high quality ingots of complex chemistries. In some cases, all three are used, e.g., alloys for aerospace applications and increasingly those for fossil power applications under extreme conditions. Electroslag remelting startup and operation is a complicated endeavor, dependent upon several factors, especially when using cold startup. A research scale 440 lb capacity ESR furnace was used to melt low resistance (1018 steel) and high resistance (316 stainless steel) electrodes. This, along with various combinations of electrode diameter/crucible size combinations, was used to assess melt parameters and sidewall and other quality aspects of the product ingots. These observations were compared to results from ESR modeling (MeltFlow ESR). It was found that fill factor and electrode resistance had a significant impact on startup condition requirements, steady state voltage and current requirements, among others.

9:45 AM  
Modeling Electrochemical Effects on Electric Current Distribution in Electroslag Remelting (ESR) Process: Ebrahim Karimi Sibaki1; Abdellah Kharicha1; 1Univ of Leoben
    Numerous electrochemical reactions were postulated for chemical elements such as S, O, Al, and Fe to describe metal refinement mechanisms in the ESR. Thus, understanding electrochemical transport of ions (by advection, diffusion, and electro-migration) within the slag bath and electrochemical (Faradaic) reactions at slag-metal-gas-mold interfaces are of great importance. We propose a model that includes the effect of transport/reaction of ions on the distribution of electric current density, and consequently the magnetohydrodynamics (MHD) within the slag bath as well as melt pool. The movement of slag-metal interface and mold current are also taken into account in our model. The former significantly impacts the electrical resistance/power signal, and consequently the melting behavior of the electrode during the process. The latter can affect the thickness of slag skin that in turn determines the surface quality of the final ingot.

10:10 AM Break

10:35 AM  
Effect of AC Frequency on Melting Conditions During Electroslag Remelting: Brendan Connolly1; John Nauman1; Evan Kendall1; 1Ellwood Quality Steels
    Ellwood Quality Steels operates two ESR furnaces: ESR1 utilizing a 25,000A 60Hz inverter power supply and ESR2 utilizing a 50,000A 2.5Hz cycloconverter power supply. This work examines the differences in melting conditions and ingot quality of 760 mm diameter ESR using 60 Hz versus 2.5 Hz alternating current. Metallurgical comparisons include melt pool depth and shape, microcleanliness, segregation and inclusion distribution. Electrical and physical conditions during melting are compared.

11:00 AM  
Slag Degassing for Electroslag Remelting using Cold Start: Martin Detrois1; Paul Jablonski1; 1National Energy Technology Laboratory
    The effect of slag degassing prior to cold start electroslag remelting (ESR) was investigated using various heat treatments of a commercial CaF2 – 30CaO – 30Al2O3 slag. The slag was either degassed in a vacuum heat treatment furnace or in a box furnace in air. Vacuum heat treatment included partial pressure of Ar gas. Several steps and holding times were investigated for each condition and the pressure was monitored for the heat treatment in the furnace with controlled atmosphere. A research scale 440 lb capacity ESR furnace was used for the experiments along with 1018 steel and 316 stainless steel electrodes. Significant differences in ingot sidewall quality were obtained and were primarily located near the bottom. Adjustments in the heat treatment time, ramp rate and temperature for heat treatment in air eventually led to a sidewall quality near those obtained using slag degassed under vacuum and/or in a controlled atmosphere.

11:25 AM Panel Discussion