The temperature has a great influence on the fluidity of the grease used in the motor. When the temperature rises, the grease becomes soft, so that the grease adhesion property is lowered and it is easy to be lost. In addition, under higher temperature conditions, the evaporation loss of the grease is also easily increased, and the oxidative deterioration and the condensed oil separation phenomenon are severe. The main cause of grease failure is mostly due to gel shrinkage and evaporation loss of the base oil, that is, the speed of the grease failure process is related to the use temperature. Greases with good high temperature performance can maintain their adhesion performance at higher service temperatures, and the deterioration process is slower. The high temperature performance of the grease can be assessed by indicators such as drop point, evaporation and bearing loss.
Grease dropping point: refers to the lowest temperature at which a certain fluidity is reached under specified conditions, expressed in °C. Dropping points have no absolute physical meaning, and their values vary depending on the device and heating rate. The dropping point of the grease mainly depends on the type and content of the thickening agent, and the dropping point of the grease can roughly reflect the upper limit of the operating temperature. Obviously, the grease has lost its ability to adhere to the metal surface when it reaches the dropping point. Generally speaking, the dropping point of the grease is used at a temperature of 20-30 ° C or lower.
Evaporation of grease: refers to the percentage of the mass of grease lost after evaporation under specified conditions. The degree of evaporation of the grease depends mainly on the type of base oil used, the fraction composition and the molecular weight.
Loss of grease bearing: It is the performance of simulated grease in rolling bearings of automobiles and construction machinery. Method summary: Take the fat sample, load a grease in the bearing 29, another bearing 39, the speed is 660r/min, the bearing temperature is 105, the running time is 10H, and the grease is measured by the amount of grease being pumped on the bearing. The working characteristics, and pay attention to the surface condition of the bearing at the end of the test, obviously, the greater the loss, the worse the high temperature performance of the grease.