Leimauspitoisuus

Leimauspitoisuus refers to the ability of a lubricant to prevent metal-to-metal contact between moving surfaces under high pressure. This property is crucial in preventing scuffing, scoring, and seizure of machine parts, especially in applications where loads are high and speeds can vary. It is essentially a measure of a lubricant's capacity to withstand extreme pressure conditions.

Lubricants achieve leimauspitoisuus through the action of specific additives, often called extreme pressure (EP) additives. These additives are typically compounds containing sulfur, phosphorus, or chlorine. Under high pressure and temperature conditions that occur at the points of contact between metal surfaces, these additives react with the metal to form a thin, sacrificial film. This film has a lower shear strength than the base metal, allowing it to deform or shear under pressure, thereby preventing the direct welding and tearing of the metal surfaces.

The effectiveness of a lubricant's leimauspitoisuus is often assessed through standardized tests. Common methods include the four-ball EP test, which measures the load-carrying capacity before seizure occurs, and the Timken OK load test, which determines the maximum load a lubricant can withstand without failure. A higher leimauspitoisuus value in these tests indicates a greater ability of the lubricant to protect against wear and damage under extreme conditions. Applications where leimauspitoisuus is particularly important include gears, bearings, and metalworking operations.