The load-bearing capacity and wear resistance of industrial gear oil can be determined by three testing methods, namely SH 0306 (CL-100 gear machine method, commonly known as FZG test, the gear used in the test was originally provided by the German FZG company and is now domestically produced), GB11144 (Timkentesting machine method), and four ball machine test. Among these three methods, I think the SH 0306 test is the closest to the actual operating conditions of the gear transmission device. The oil temperature in its test program is 90 ℃, which is high, followed by TMK, and the oil temperature is 40 ℃. Anyway, the friction pair used in the TMK test is in 'line' contact, while the friction pair used in the four ball machine test is in 'point' contact, both of which are too extreme.

On the other hand, the evaluation methods for the bearing capacity and abrasion resistance of vehicle gear oil, namely SH0518 (L-37 method) and SH 0519 (L-42 method), have oil temperatures of 135-150 ℃ for L-37 test and 90-110 ℃ for L-42 test. From the temperature of the test oil alone, the requirements for extreme pressure anti-wear performance of vehicle gear oil are more stringent than those of industrial gear oil, which inevitably requires the addition of more extreme pressure anti-wear agents in the vehicle gear oil. Therefore, the corrosion level requirements for vehicle gear oil are looser than those for industrial gear oil, which are level 3 and level 1, respectively. The inherent reason for this is that extreme pressure anti-wear agents and corrosion inhibitors are more effective in improving the anti-wear performance of the oil. The 'antagonistic effect'. Similarly, there is no requirement for anti emulsification performance in the standards for vehicle gear oil, which is an important property of industrial gear oil. Of course, the low chance of water pollution caused by contact with water during the use of vehicle gear oil is also a reason.

Someone once proposed the concept of 'effective extreme pressure' of gear oil and expressed it as:

EPe=∑A-∑B

In the formula: EPe - effective extreme pressure;

∑ A - Contribution of Load Additives to Extreme Pressure;

∑ B - Reduction of extreme pressure by corrosion inhibitors, etc.

Attempting to express and quantify the above formula through synergistic and antagonistic effects, viscosity pressure relationships, and the sensitivity of base oils to adsorbent additives, but due to the complexity of the entire lubricant product system and the multitude of influencing factors, 'effective extreme pressure' still remains a concept to this day. However, for the research and development of gear oil or other lubricating oils, we should know that the core of lubricant additive formulation technology is to find synergistic effects, avoid antagonistic effects, and synergistic effects can reduce the amount of additives used and improve the technical and economic indicators of the oil.

Let's talk about the testing method for industrial gear oil again. In the standard of working gear oil, although the TMK test involves the test piece (ring, block) in a state of linear contact friction, which does not match the actual operating state of the gear, it is a difficult test to pass. It is sensitive to the structure of load additives, and some special structural additives have high OK loads. In addition, load-bearing capacity actually includes extreme pressure, wear resistance, and friction improvement. Extreme pressure does not necessarily mean good load-bearing capacity. Excessive extreme pressure can lead to corrosive wear and deteriorate wear resistance. To deal with FZG testing, certain structures of phosphorus containing extreme pressure agents are indispensable.