Authors:
Dr. Christoph Wöhrmeyer | IMERYS | France
Dr. Ratana Soth | IMERYS | France
Mickael Lievin | IMERYS | France
Rose-Marie Mineau | IMERYS | France
Eric Frier | IMERYS | France
Valerie Germain | IMERYS | France
Chunfeng Liu | IMERYS | France
Xinyue Ma | IMERYS | France
Jean-Michel Auvray | IMERYS | France
Alumina-spinel (A-MA) refractories are well known products for steel ladle applications providing excellent refractoriness and corrosion resistance. Although improved compared to pure alumina refractories, their thermal shock resistance (TSR) still remains significantly below mullite and andalusite based products. However, to minimize interactions with steel, higher amounts of silica containing phases are not desired in direct contact with high quality steel. An improvement of the TSR of A-MA dry-gunning mixes has been reported with the introduction of MagArmour, a porous Calcium Magnesium Aluminate (CMA) aggregate consisting of micro spinel crystallites and hydraulic calcium aluminate phases. However, applied in castables, the water demand slightly increases, and furthermore, without adjusting the matrix composition, shrinkage after firing at 1500°C may occur.
This paper will discuss a novel member of the CMA family of products, a newly designed synthetic aggregate that, like MagArmour, belongs to the CaO-MgO-Al2O3 system, but further optimizes the in-service properties in A-MA castables and bricks, especially with respect to TSR. Special focus is also given to rheological properties and the permanent linear change after firing to ladle service temperature. Micro- and macrostructural properties will be correlated with thermomechanical properties to allow an insight into the underlying mechanisms that lead to the superior TSR, and the desired positive permanent linear change. It will be discussed how this smart aggregate upon firing creates a symbiosis with its surrounding matrix and an entire new microstructure, that involves not only the usual in-situ reactions in the matrix but as well inside this novel spinel-rich aggregate.