BS EN 993-11:2007 pdf free.Methods of test for dense shaped refractory products – Part11:Determination of resistance to thermal shock.
Introduction
Thermal shock of refractory materials used in furnaces is influenced by three main factors:
– brick dimensions;
– heating/cooling conditions;
– material properties.
Thermal shock tests are usually intended to test material properties. This is done by standardizing brick dimensions and heating conditions through which a relative order of the quality of different types of bricks can be established. However, in case of thermal shock, this can lead to complications in the field of engineering.
The major complication is that, depending on the type of heating conditions, various material properties are involved. This can be best illustrated on the basis of thermal stress parameters, which are a measure for critical crack initiation.
BS EN 993-11 describes two alternative methods for determining the resistance to thermal shock of dense shaped refractory materials by an air quenching method, which proved to give the most reliable results when compared with the behaviour of refractories in furnace linings.
Method B can also be applied to unshaped refractory materials.
2 Normative references
EN 993-6, Methods of test for dense shaped refractory products – Part 6: Determination of modulus of rupture at ambient temperature
4 Principle
4.1 Method A
The test piece is homogeneously heated to 950 °C in an electric furnace then removed, placed on a steel plate and exposed to blowing air. After quenching, the test piece is subjected to a stress of 0,3 MPa in a bending machine. This cycle is repeated until failure of the test piece occurs.
The resistance to thermal shock is defined by the number of cycles withstood by the test piece before breaking.
4.2 Method B
The test piece is homogeneously heated to 950 °C in an electric furnace then removed, placed on a steel plate and exposed to blowing air. After quenching this is repeated 4 times. After cooling down, the residual cold MOR and the residual sonic velocity are determined.
The resistance to thermal shock is defined by the percentage residual MOR and residual sonic velocity related to the MOR and sonic velocity of non-quenched test pieces.BS EN 993-11 pdf download.