Weld Point of Lubricating Fluids

Description

An extreme fluid crash test recording the maximum peak load at which the lubricating film breaks down and the metal parts weld together.

The worst-case scenario for any mechanism is the welding of parts right during operation. When the load exceeds all design limits, the oil is completely squeezed out of the contact patch, and steel begins to rub against steel with colossal heat generation. Determining the Weld Point in the RENA laboratory is a true extreme crash test for your gear or industrial fluid. This analysis proves how powerful the extreme pressure (EP) additive package in the product is and what maximum shock load your gearbox or axle can withstand before a complete emergency seizure. The test is performed on a precision four-ball friction machine (FBT-3). Unlike calculated indicators (such as the load wear index), here we are interested in only one, the final and most destructive indicator. The operator subjects a pyramid of four steel balls, immersed in the test oil, to short 10-second impacts at a rotation speed of 1760 rpm. With each new cycle, the axial load on the system is ruthlessly increased (e.g., 250, 315, 400, 500 kgf). Upon reaching extreme pressures, the temperature at the micro-contact points instantly soars above the melting point of steel. The film of sulfur-phosphorus additives breaks down completely, and direct contact of bare metal surfaces occurs. Friction causes instantaneous local melting, and the balls physically weld to each other into a single steel monolith. The machine stops abruptly, and the load that caused this failure is recorded as the weld point.