What are the more complex issues in the research and development of industrial gear oil compared with vehicle gear oil?
September 06, 2022
This article is devoted to the complexity of industrial gear oils. Compared with vehicle Gear Oil, industrial gear oil is more complicated because its equipment operates in various environments, such as easy contact with water, humidity, dust pollution, etc., involving many industries, such as steel, mining, construction, non-ferrous metals, etc. , There are many kinds of viscosity, large span, as low as 68#, as high as 1000# or even higher, special gear materials, such as worm gears and worms. In this way, it brings a series of problems to industrial gear oil, such as how to improve its oxidation stability and thermal stability to ensure a long oil change period, how to ensure its anti-emulsification performance and anti-foaming performance after the oil is contaminated , bearing wear, bearing corrosion, etc., and even some special users have put forward higher requirements for the cleanliness of the oil.
In addition to the most basic type difference between closed gears and open gears, more complex situations can be understood with just one example: we classify worm gear oil into industrial gear oil, and worm gear and worm are actually a kind of hyperbolic gear In the extreme form, the gear shaft can achieve maximum offset, the material of the worm is usually harder steel, and the worm wheel is bronze (an alloy of copper and tin or lead). Theoretically, the gear teeth are in point contact under pure sliding conditions, the relative sliding speed of the tooth surface is high, the temperature of the tooth surface is high, the oil film is easily damaged, and the lubrication conditions are harsh. The friction characteristics of steel-copper and steel-steel friction pairs are definitely different, so there are differences in the emphasis of the formula, which complicates the selection of additives. Speaking of open gear oil, it is suitable for open gears, semi-closed gears and some low-speed gear devices. It is divided into ordinary type and extreme pressure type. It must have good adhesion, and it is open gear oil. The most important property is that the gear oil can keep the oil film on the tooth surface and prevent the oil droplets from splashing and dripping. Therefore, it is necessary to add an adhesive. To make it more complicated, it is also divided into dilution type and type. Non-diluted, concomitantly, the adhesive tends to stick to dust, causing abrasive wear. Imagine the operating environment of open gear oil in an environment like a ball mill for ore or coal! Furthermore, in the research and development process of industrial gear oil, some test methods and test equipment are also a confusing factor. For example, the standard TIMKEN testing machine, its OK load is very sensitive to the structure of the load additive (extreme pressure anti-wear agent). Experienced test operators know that the material, hardness and direction of processing marks of the test ring block, will affect the result of the OK load. Studies have shown that the repeatability of the OK load is very general, repeatability: Base Oil, ± 10 pounds; medium extreme pressure oil, ± 15 pounds; high extreme pressure oil, ± 20 pounds. Therefore, the TIMKEN test is used to distinguish base oil and extreme pressure oil, and has a certain degree of reliability, and we have to doubt the extreme pressure level of the oil. As mentioned above, the cleanliness of industrial gear oil has become a new concern of users, and the foam performance is a difficult use performance of industrial gear oil. Too much Anti-foaming Agent will affect the extreme pressure and anti-wear agent. performance, and will adversely affect the cleanliness. All of the above are topics that we cannot avoid in the future.
The bearing capacity and anti-wear ability of industrial gear oils are determined by three test methods, namely SH 0306, GB11144 (Timken﹤TMK﹥ test machine method) and four-ball machine test. Among these three methods, I think the test of SH 0306 is the closest to the actual operating conditions of the gear transmission. In the test procedure, the oil temperature is 90°C, which is the highest, followed by TMK, which has an oil temperature of 40°C. In any case, the friction pair of the TMK test is a "line" contact, and the friction pair of the four-ball machine test is a "point" contact, which are too extreme. In contrast, the evaluation methods for the bearing capacity and scratch resistance of vehicle gear oil, namely SH0518 (L-37 method) and SH 0519 (L-42 method), the oil temperature of L-37 test is 135-150 ℃, L-42 The oil temperature of the test is 90-110℃. From the temperature of the test oil, the extreme pressure and anti-wear performance requirements of vehicle gear oil are more stringent than that of industrial gear oil, which is bound to add more to the vehicle gear oil. Therefore, the corrosion level requirements of the gear oil should be looser than that of the gear oil, which are grade 3 and grade 1 respectively. The internal reason is that the extreme pressure anti-wear agent and Corrosion Inhibitor are in the The "counterfeit effect" exhibited by the oil's anti-wear properties. In the same way, there is no requirement for anti-emulsification performance in the standard of vehicle gear oil, but anti-emulsification is an important property of industrial gear oil. Of course, in the process of using vehicle gear oil, there is a chance of being polluted by water in contact with water. Less is also a reason. Someone once put forward 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 loading additive to extreme pressure; ∑B—The reduction of extreme pressure by corrosion inhibitors, etc. Attempts to express and quantify the above formula in terms of synergistic effect and confrontation effect, viscosity-pressure relationship, susceptibility of base oil to adsorbent additives, etc., but because the whole system of lubricating oil products is too complicated, there are many influencing factors. , so, "effective extreme pressure" is still a concept. Even so, for the research and development of gear oil or other lubricants, we should know that the core of Lubricant Additive formulation technology is to find synergistic effects and avoid confrontation effects. Synergistic effects can reduce the amount of additives and improve the technical and economic indicators of oil products. . Let's go back to the test method of industrial gear oil. In the standard of gear oil, although the TMK test is in the state of linear contact friction of the test piece (ring, block), which is not consistent with the actual operating state of the gear, it is a test that is difficult to pass. The structure of additives is very sensitive, and some additives with special structures have higher OK loads. In addition, the bearing capacity actually includes extreme pressure, anti-wear and friction improvement. Good extreme pressure does not mean good bearing. Too high extreme pressure will lead to corrosive wear and deteriorate the wear resistance. For the FZG test, certain structures of phosphorus-containing extreme pressure agents are indispensable.
