Abrasion In Refractory
Part 1. The nature of abrasion
Part 2. Testing for abrasion resistance
Part 3. Estimating the severity of abrasive conditions
Part 4. Monolithic refractories designed for abrasive conditions
Part 5. R-MAX extreme service products
An abrasive is often a mineral used to shape or finish a workpiece through rubbing. Ceramic abrasives are used to cut, grind, and polish other materials. Abrasives are usually- but not always- harder than the material being worked upon.
What is Refractory Hardness?
The hard matter is characterized by strong intermolecular bonds. By definition, hardness is a measure of the resistance of a material to plastic deformation induced by either mechanical indentation or abrasion. There are several methods used to determine the hardness, most measure deformation of a compressive load from a sharp object.
The most elementary method to measure scratch hardness was developed by Friedrich Mohs. Mohs hardness uses a simple observation of whether a material is able to scratch 10 minerals of increasing hardness.
Thus, the material is rated on the Mohs scale of mineral hardness between 1 and 10, with a 1 being soft and 10 the hardest, which is a diamond.
This table shows some common materials and their Mohs rating. Note that concrete is mid-scale, with a minimum rating of 5. For purposes of our discussion on refractory castables, we will assume that typical refractory concretes, otherwise known as castables, also have a Mohs rating of 5.