Introduction
Non-metallic inclusions have a substantial effect on material properties, especially in dynamic loaded tool steels and engineering steels as well as for corrosion resistant steels. They mainly limit material properties such as fatigue, deformability, the pitting corrosion potential, surface quality and polishability of steel. The usual praxis to improve these material properties are, for highest requirements, remelting techniques such as Electro-Slag-Remelting (ESR). During these special refining steps, especially larger inclusions can be successfully removed.
However, remelting processes have a high energy consumption, which in the case of ESR, strongly depends on the slag composition and slag properties. Process parameters (such as slag quantity and remelting rate) and material properties (such as electrical conductivity, viscosity, solidification behavior) influence the specific energy consumption; however, the exact correlations are rarely investigated.
Objectives and Motivation
- Fundamental correlations between specific slag properties and the energy consumption during ESR
- Determination of the influence of slag parameters on formation of slag skin and on the surface quality of the ESR ingots
- Detailed analysis of the correlations between remelting experiments, physical and chemical material properties and the change of non-metallic inclusions
The planned methodology of the current project consists of three blocks. First, different electrodes and slags will be produced, and material data will be derived from available literature. The electrode material will be manufactured by the involved compamy partners from standard ingot or continuous-cast material from their industrial processes with typical quantities and compositions of non-metallic inclusions. This will be the basis for further investigations with the final goal of setting up correlations with the specific energy consumption during ESR.
The second part of the planned research work contains remelting trials at an ESR laboratory unit in the technical centre of our scientific project partner, University of Applied Sciences - Upper Austria (Wels Campus, see figure 1). Among others, slag compositions will be varied during these experiments. Standardized slag types and specific (newly developed) slag systems will be used in the course of the project to compare explicitly chosen remelting parameters. During the ESR tests, slag temperature will be measured, and the surface flow pattern will be documented.
Following the experimental activities, the third part of the project is focused on the analysis of the remelting trials as well as on a generation of correlations with physical and chemical slag properties and with the change of non-metallic inclusions (see figure 2).
Results and application
At the end of the project, comprehensive statements are expected, which process parameters and slag properties mainly influence the specific energy consumption during ESR. Based on that, slag compositions with an improved combination of energy consumption and steel cleanliness level should be derived.
By means of extensive process parameter analysis and using the correlations with specific material properties, a deeper and extended understanding is expected regarding possibilities to influence the energy consumption and the steel quality during ESR in a sustainable way and to make these possibilities ready for use in practical applications.