Surface damage
Wear occurs due to surface damage at the contact point between the rock minerals and the steel plate. This damage can be classified into two types: “cutting,” which is severe, and “plastic deformation,” which is milder. The SSAB model evaluates wear resistance by comparing how steel with different hardness levels performs under identical surface damage conditions. In the figure below, two curves illustrate the relative differences in wear caused by cutting and by plastic deformation.
Cutting and plastic deformation.
Cutting occurs when hard abrasive particles penetrate the steel surface, removing material in the form of steel chips. If the edge of an abrasive particle fractures, the newly exposed sharp edge continues the cutting process, further contributing to material removal.
Plastic deformation occurs when softer abrasive particles slide over the steel surface. These particles may initially have rounded edges or quickly become rounded as they are forced to slide against the surface. The pressure from the sliding abrasives pushes the steel material sideways, creating a plastic plowing effect. Wear occurs over time as repeated deformation eventually causes a steel chip to be worn off.
What hardness of the abrasive causes specific types of damage? In SSAB’s model, the relative ratio (Hr) is used to determine which curve to follow. This ratio is calculated by comparing the hardness of the abrasive materials (Ha) to the hardness of the steel (Hp).
When the hardness ratio between the mineral and the steel exceeds the threshold value, the relative wear follows the curve for cutting surface damage. Conversely, when the ratio is below the threshold, the relative wear follows the plastic deformation curve.
The transition between cutting and plastic deformation is very interesting from a wear perspective, since even a slight increase in hardness can lead to a significant improvement in wear resistance.
This relationship is illustrated in the chart below, which compares three minerals with different hardness values: 400, 600 and 1000 HV. The relative wear rate (RW) is at a high level along the red curve and low along the blue curve. The point at which this transition takes place depends on the mineral's hardness and the corresponding steel hardness.
Relative wear curve with multiple minerals.
The information in this report is only applicable to SSAB’s products and should not be applied to any other products than original SSAB products.
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