The temperature at which the lubricating grease is heated under the specified conditions to reach a certain fluidity is called the drop point, which is expressed in degrees Celsius.

The dropping point of lubricating grease is only a conditional indication of the melting point of lubricating grease, so it has no physical significance. For lubricating grease with a dropping point below 100 ℃, the upper limit of the temperature at which they can work is 15% lower than the dropping point ­ 20 ℃.

However, due to the appearance of grease with a drop point much higher than 100 ℃, such as lithium base grease (170 ­ 200 ℃), compound calcium base grease (230 ­ 260 ℃),

Composite lithium base grease (greater than 260 ℃) and composite aluminum base grease (250 ­ 260 ℃. This indicator has lost its practical significance.

For example, the upper temperature limit at which lithium base grease can work is 110 ­ 130 ℃, and the upper limit of temperature at which the compound calcium base grease can work is 150 ­ 160 ℃.

Sometimes the type of grease thickener can be roughly judged according to the drop point, for example, the drop point of calcium base grease is 70 ­ 90 ℃, drop point of lithium grease 160 ­ 200 ℃, drop point of composite soap base grease 230 ­ 260 ℃ or higher. However, it is important to estimate the high temperature that the grease may use according to the drop point. If the dropping point of the grease is close to or lower than the temperature of the lubricating part, the grease will melt from the lubricating part and be lost.

Although the dropping point of grease has no exact physical meaning, when studying grease, we often hope to obtain a high dropping point, because a high dropping point means a wide range of applications. The primary indicator of high-temperature grease is the drop point. If there is no high drop point, there is no condition for high-temperature grease. Of course, high-temperature grease with good performance should have good anti-oxidation stability and low evaporation loss in addition to high drop point.

There are three methods to determine the drop point: lubricating grease and solid hydrocarbon drop point determination method sh/t 0115 ­ 92. Determination of dropping point of lubricating grease gb/t4929 ­ 85 and lubricating greases determination of drop point over a wide temperature range gb/t 3498 ­ 83. The first two methods can only measure the drop point below 250 ℃, while the latter can measure the drop point of various types of grease up to 330 ℃. The corresponding foreign methods for measuring the dropping point of lubricating grease include ASTM d566 in the United States, ASTM d2265 (wide temperature method), DIN 51801 in Germany and JIS k2220 5.4 in Japan.