Today I learned something new. A customer gave me a picture of a bearing, as shown in the figure below. Inside the black bearing, the balls are one next to each other. Without the retainer, it is ok, but there is actually a cylindrical "foreign body" hidden inside!

It's strange, what kind of bearing is this, and how is it used? Ha ha, the group isn't short of experts. A colleague from a bearing manufacturer immediately recognized that this is a self-lubricating high-temperature bearing. A high-temperature self-lubricating bearing is a type of bearing that can achieve high-temperature lubrication without the need for external lubricating grease. To achieve high-temperature lubrication, the lubricant must maintain its physical and chemical properties at high temperatures without evaporating. This typically requires a solid form of the lubricant. Graphite is a common choice, as it has a simple manufacturing process, is heat-resistant and corrosion-resistant, and maintains stable physical and chemical properties at high temperatures. It is also cost-effective and provides excellent lubrication. The 'foreign object' in the picture is self-lubricating graphite. Typically, two graphite blocks are symmetrically or nearly symmetrically assembled (with the maximum distance between the two graphite blocks in the circumferential direction). The two graphite blocks, along with the steel balls, rotate together, and some graphite powder is worn into the groove to serve as a lubricant. When the bearing stops rotating, the wear also stops, ensuring that lubrication and consumption occur simultaneously.

This bearing is used in environments with extremely high temperatures, typically reaching 300°, and in some cases, up to 800℃. The surfaces of the bearing and dust cover are usually coated with manganese phosphate, which enhances the bearing's corrosion resistance and performance at high temperatures. However, students who pay close attention will notice that, due to the absence of a cage and the uneven distribution of balls caused by solid lubricants, this bearing has limited load-bearing capacity and cannot operate at very high speeds (ranging from tens to hundreds of revolutions). I hope this article helps you understand this type of bearing!