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Chair of Ceramics

Main Research

09/07/2011

Melt corrosion of refractories in metallurgical vessels

Refractories are materials used to line commercial furnaces such as steelmaking vessels, glass tanks and cement kilns. Refractories in metallurgical vessels must resist high temperatures (up to 1650 °C) but also mechanical stresses (erosion, abrasion) and the attack by corrosive atmospheres and liquids (molten metals, slags). The attack of refractories is a complex phenomenon, as the corrosion mechanisms act synergistically.

The research group “Melt corrosion of refractories in metallurgical vessels” deals with the description of the chemical wear. The melt corrosion occurs in two steps for porous, ceramically bonded materials: penetration of the slag into the refractory via open pores and dissolution of the refractory components into the slag. The ion flux j caused by the dissolution process is governed by Fick’s First Law:

D diffusion coefficient
CS solubility limit
C0 initial concentration in the slag bath
d boundary layer thickness

According to the equation above, the corrosion rate is a function of many variables including characteristics of the refractory and the slag as well as predominant process conditions. Thus, to reduce the wear rate of refractories in metallurgical vessels emphasis must be placed on the one hand on product development but on the other hand on the steelmaking practice with regard to slag chemistry and service conditions. The investigations presented here comprise the characterisation of different metallurgical slags (eg ladle, converter, EAF) as the attacking medium and the description of different refractory/slag equilibria.

The objectives of the research area are

  • Description of the main corrosion mechanisms in different metallurgical vessels
  • Establishment and evaluation of new corrosion models
  • Identification of possibilities to reduce the wear-rate: process performance, lining design, product selection, product development

Approach/Methodology

The investigations focus on the characterisation of slags and refractory/slag equilibria using thermochemical (FactSage), mineralogical (XRD, SEM, EDX) and analytical tools.

Characterisation of metallurgical slags

  • Phase constitution in dependence of temperature and atmosphere
  • Melting behaviour (solidus and liquidus temperature, amount of liquid)
  • Physical properties of the slag (eg viscosity, diffusion coefficient)

Characterisation of refractory slag/equilibria

  • Identification of corrosion environments (eg slag chemistry, temperature)
  • Post-mortem investigations of industrial refractories and laboratory scale corrosion tests (cup test, rotary slag test, induction furnace test)
  • Description of the dissolution behaviour of refractories in slags in dependence of process conditions (eg phases formed at the interface, solubility limit)

 

 

Reference

F. Melcher, V. Reiter, H. Harmuth: Investigation of refractory/slag equilibria in steel ladles. Presented in: Calphad XXXVI, Pennsylvania State University, 2007.

Contact : Franz Melcher, Viktoria Reiter