Kurzfassung

In generic use, monolithic refractory materials are mixed and installed on site into aggregates for thermal treatment, e.g. steel ladles. After installation, the monolithic refractory materials are being dried and heated up, but often not up to the later service temperature (typically for steel ladles, heating-up before first tapping of liquid steel is finished when 1100 C is attained, but liquid steel is tapped into steel ladles at up to 1750 C). In this example, the first tapping of liquid...In generic use, monolithic refractory materials are mixed and installed on site into aggregates for thermal treatment, e.g. steel ladles. After installation, the monolithic refractory materials are being dried and heated up, but often not up to the later service temperature (typically for steel ladles, heating-up before first tapping of liquid steel is finished when 1100 °C is attained, but liquid steel is tapped into steel ladles at up to 1750 °C). In this example, the first tapping of liquid steel into a relined ladle boosts the temperature of the monolithic refractory material from 1100 °C to 1750 °C at the hot face.
The common opinion about monolithic refractory materials with cement bonding is that their hydraulic bonding system is responsible for strength in the green state, and that they are being dehydrated completely during the heating-up procedure. However, refractory installations generally work in a temperature profile. It is therefore obvious that a monolithic refractory lining is heterogeneous over the thickness of the lining, where only the first few centimetres can develop a ceramic bonding, followed by a dehydrated and thus mechanically weak transition zone, and at the cold face even hydrate phases may still be found. Accordingly, there is also a strength profile over the thickness of the lining.
During their use, these refractory linings undergo mechanical loading and subsequent wear, which removes parts of the hot face and brings material from the transition zone to the hot face of the installation. The life of a monolithic refractory lining is thus highly dynamic, and the development of mechanical strength in the material depends not only on temperature, but also on time. It is therefore the objective of the research project to understand and optimise the sintering behaviour of monolithic refractory materials in function of temperature and time, to generate strong refractory linings in a highly dynamic environment.
Three major deliverables are derived from the reported features of monolithic linings:
 How do the transition zone and the dehydrated zone affect the thermo-mechanical properties (strength) of the refractory lining, as the time- and temperature-dependent development of mechanical strength plays an important role?
 How can the time- and temperature-dependent development of mechanical strength due to sintering be enhanced by addition of sinter-active micro-particles? The goal is to improve the sintering behaviour of monolithic refractories at low temperatures.
 What is the long-term evolution of the hydrated phases at the cold side of the installation and does it affect the stability of the refractory lining? This will deliver new insights in the role of CA2 on the long-term stability of hydrous phases.
Project partner and goals:
 Thermo-mechanical characterisation of monolithic refractories by means of thermo- mechanical loading, strength evolution, fracture toughness etc. in the dehydrated zone and in a temperature gradient, supported by FEM calculations (FGF)
 Development of a testing scheme to determine the elasticity range of monolithic re- fractories during mechanical loading in a temperature gradient and the material fatigue during thermo-cycling by means of RFDA and X-ray diffraction dilatometry (ICiMB)
 Development of monolithic refractories with enhanced properties in the transition zone/dehydrated zone by systematic understanding of the influence of sinter-active micro-particles on the sintering behaviour and on the strength (Hochschule Koblenz)» weiterlesen» einklappen