A review of electroslag remelting composite technologies

Abstract

Electroslag remelting (ESR) is an important metallurgical process for producing high-purity materials with homogeneous compositions and sound microstructures, and its typical products are ingots or simple castings. The core principle involves the resistive melting of a consumable electrode within a slag pool, followed by the refining of molten metal droplets as they traverse the slag, and subsequent sequential solidification in a water-cooled mold. However, conventional ESR processes face limitations in producing large or complex-shaped components, enhancing production efficiency, achieving highly specialized microstructures, and meeting ultra-high purity demands for advanced applications. Advanced composite ESR technologies have been developed to overcome these limitations by innovatively modifying key process aspects. For instance, electrode systems are improved using vibration, rotation, or multiple electrodes. Enhanced mold design and solidification control are achieved through techniques including conductive molds, mold rotation, and ingot withdrawal. Precise control of the process is realized through the use of protective gas, vacuum, or elevated pressure, as well as the application of external fields such as magnetic fields or ultrasonic vibration. This review comprehensively summarizes these advanced techniques, examining their principles and characteristics, and discussing their specific advantages and challenges.

1. Introduction

High-performance materials are a critical requirement for modern engineering and manufacturing [1]. Additionally, manufacturing demands processes capable of producing large, complex, near-net shape components to minimize machining and material waste [2, 3]. Electroslag remelting (ESR) is identified as a key secondary metallurgy technique [4], offering unique capabilities for refining metals and alloys and producing high-integrity components [5]. The ESR process, whose technical principle is illustrated in Fig. 1 [6], progressively melts a consumable electrode through Joule heating generated by an electric current passing through a reactive molten slag. This configuration promotes efficient heat generation, provides atmospheric shielding, facilitates refining reactions, enables effective sequestration of non-metallic inclusions, and ensures controlled heat transfer during solidification in a water-cooled copper mold [7]. As a result, materials produced via ESR demonstrate improved cleanliness, minimized segregation, refined solidification structures, and enhanced mechanical properties compared to those produced by conventional methods. These characteristics make ESR materials highly suitable for applications in aerospace, power generation, tooling, and heavy industries [8].

However, conventional ESR processes have limitations that restrict their use for sophisticated industrial needs. For instance, the production of very large ingots using a single electrode is inherently challenging. Fabricating complex geometries using conventional molds is often impractical; precisely controlling solidification behavior and microstructural evolution remains challenging; and achieving ultra-low levels of gases and impurities is particularly difficult for certain advanced alloys [9-11]. To overcome these limitations, substantial research and development have been conducted, and various advanced or “composite” ESR techniques have emerged. Key innovations include: electrode systems that use dynamic actuation or multiple units; mold designs that feature conductive materials or withdrawal systems; process atmospheres with precise control (e.g., pressure, composition); and external physical fields (e.g., magnetic, ultrasonic) that manipulate process dynamics. These composite manufacturing technologies aim to enhance refining and microstructure control, facilitate near-net shape manufacturing, enable the production of functionally graded materials or composite structures, and allow for the processing of novel alloys [12, 13]. This paper reviews the significant progress in advanced ESR technologies. Section 2 discusses electrode system modifications. Section 3 covers mold design and solidification control innovations, including external field assistance. Section 4 details process atmosphere and pressure control techniques. This review integrates recent findings, examines fundamental principles and pertinent challenges, and delineates future research directions within this developing field.