In order to simulate accelerated industrial working conditions and to predict the degradation of refractories, elaborate testing procedures are performed.
The resistance to thermal and chemical stresses is tested with the dynamic finger test and the static plate corrosion test according to the International Commission on Glass, Technical Committee 11 (the so-called TC11).
In the dynamic finger test, a cylindrical sample is rotated in a platinum crucible together with molten glass. The test is carried out with predefined parameters (temperature, time) and the reduction in diameter at ﬂuxline (three phase contact) is measured. The corrosion rate can also be determined by measuring the decrease in length (forced convection at the rotating cylinder face) as a function of time and at various rotation rates.
In the static plate corrosion test, sample platelets are immersed into the glass melt. After the chosen time the ﬂuxline depth of the corroded samples is measured. This test is carried out with four samples under the same test conditions and is, therefore, an appropriate method to compare and evaluate certain refractory grades together. An international round-robin investigation within the Technical Committee 11 of the International Commission on Glass confirmed the good reproducibility of the static plate corrosion test, and the TC11 recommended it as the standard corrosion test.
Due to the interaction of the glass melt with fused cast AZS, solid stones can be generated.
The defect potential is evaluated by counting this kind of inclusion inside the remaining glass after each corrosion test.
The tendency of fused cast AZS to form bubbles in contact with molten glass is evaluated with an especially developed test procedure in which standard glass is molten in a fused cast AZS crucible.
The number of bubbles contained in the glass samples after test melting is an indication of blistering potential.
The tendency to release bubbles is expressed in bubbles/gram glass, following the terminology of glass defects of the International Commission on Glass.
In order to evaluate the expulsion of glassy phase, a simulation of the load-free preheating stage, which the refractory blocks in a melting furnace undergo, is performed by heating the test material up to temperatures comparable to real furnace operation conditions.
The test procedure follows the recommendations of the Technical Committee 11 of the International Commission on Glass. The experimental data of REFEL refractories show that for temperatures higher than 1500°C there is only limited exudation which decreases slowly with service time.
This test method according to ASTM is performed to evaluate the resistance of refractories in glass melting furnace superstructures to vapour attack. The vapour test method may also be useful for evaluating refractories in other applications where vapour attack occurs.