Liquid Metal Processing & Casting Conference (LMPC 2022): Electoslag Refining & Vacuum Arc Remelting
Program Organizers: Matthew Krane, Purdue University; Mark Ward, University of Birmingham; Abdellah Kharicha, Montauniversität
Monday 3:30 PM
September 19, 2022
Room: Grand Ballroom
Location: Bellevue Hotel
Session Chair: Abdellah Kharicha, Montauniversität
VAR and ESR Steels -a Critical Appraisal: John Campbell1; 1University of Birmingham
Vacuum arc remelting (VAR) and electro-slag remelting (ESR) processes are widely regarded as closely competitive processes for the production of clean metals, particularly steels and Ni alloys. A critical review of the detailed mechanisms involved in the melting process draws attention to the serious defects which can be present in VAR ingots, rendering the material unfit for safety critical applications. It is deeply regretted that this is a serious and hugely unwelcome conclusion. In contrast, ESR is found to be largely free from serious defects, and can be recommended as a reliable remelting process capable of producing reliable products.
Comments on the Columnar/Equiax Transition in Remelted Ingots: Alec Mitchell1; 1University of British Columbia
The columnar/equiax transition (CET) during solidification is often observable in ingots remelted by ESR or VAR. It is associated with enhanced segregation, porosity and larger non-metallic inclusion sizes. It is therefore advisable that the process melting parameters avoid the effect. These actions influence the process cost hence requiring definition of the CET onset. We outline the causes of the CET in alloys commonly remelted: also relate it to the solidification rate and temperature gradient. Most present melting operations cause the ingot central regions to solidify under conditions close to the CET onset driven either by dendrite fragmentation or the presence of nucleating particles depending on the alloy composition. It is suggested that melting conditions can be optimised by using the CET onset information together with suitable process models.
Manufacturing Large Superalloy Ingots for Advanced Energy Systems: John De Barbadillo1; Brian Baker1; Corey O'Connell1; 1Special Metals
The US Department of Energy, through the Office of Fossil Energy, has funded programs to demonstrate the US capability to make full-scale components for advanced energy applications such as Advanced Ultra-supercritical coal-fired steam boilers and turbines. The application which operates in the 700-800°C temperature range, requires large-diameter, heavy-wall pipes and bends, forged fittings such as “wyes” and shaft rotors. Recently completed work under contract DE-FE002564 included the manufacture of 915 mm diameter VIM/VAR and VIM/ESR/VAR ingots of INCONEL® alloy 740H® and a 915 mm diameter VIM/ESR/VAR 36” ingot of Haynes® 282® alloy. Both nickel-base alloys contain approximately 20% γ', and hence large ingots of these alloys are sensitive to solidification segregation, auto-aging and thermal stress cracking. This paper describes the melting and remelting of the ingots and presents remelting simulations that were used to guide parameter selection and verification testing. A brief overview of the extruded or forged products will be provided.