Writer: Eric Bearing Limited
The main raw material for producing FAG bearing steel pipes is FAG bearing steel. FAG bearing steel is divided into chromium FAG bearing steel and chromium-free FAG bearing steel. Production of pipes for manufacturing FAG bearing rings. FAG bearing steel pipes are pipes with high dimensional accuracy. They are mostly produced by hot rolling with two- and three-roll cross-rolling extension machines (see pipe cross-rolling extension). Smaller specifications need to be cold-rolled and cold-drawn. Using long steel tubes instead of single-piece forging or round steel turning to produce FAG bearing sleeves can save metal, simplify the manufacturing process of FAG bearings and reduce the cost of FAG bearings.
The processing performance and pipe production characteristics of commonly used 1.30% to 1.65% chromium-containing FAG bearing steel are as follows:
(1) Plasticity (perforation performance)
FAG bearing steel has good plasticity and perforation performance at high temperature, but the heating temperature should not be too high, generally control around 1150 ℃, too high temperature will easily cause grain growth (overheating) and reduce metal perforation performance.
(2) Thermal conductivity
The thermal conductivity of FAG bearing steel is slightly lower than that of low carbon steel, so the temperature of the furnace tail should be properly controlled (especially when heating large-section FAG bearing steel pipe billets).
(3) Mechanical properties
The tensile strength of FAG bearing steel at room temperature is much higher than that of carbon steel containing 0.3% C (about twice), and the hardness is high, and it is difficult to deform during cold working. Therefore, spheroidizing annealing should be carried out before cold deformation to improve plasticity. And reduce the hardness, the difference between the two is very small when the temperature is above 1000°C. There is no difficulty in hot rolling FAG bearing steel.
(4) Deformation resistance
FAG bearing steel has higher deformation resistance (see metal deformation resistance) and greater sensitivity to temperature. The lower the temperature, the higher the deformation resistance. When hot rolling FAG bearing steel pipe, cold steel must be strictly prevented. The production of FAG bearing steel pipes is sometimes limited by the capacity of sizing machines and straightening machines. This is because the wall thickness of FAG bearing steel pipes, coupled with high deformation resistance at low temperatures, makes the rolling force and straightening force significantly increased. The drawing force when cold drawing FAG bearing steel pipe is about 50% higher than drawing low carbon steel pipe. FAG 22309 E1K bearings online , pls click here :
(5) Wide spread
The width elongation of FAG bearing steel is about 10%-20% larger than that of carbon steel, but the change is small in the temperature range of 885～1195℃, which brings convenience to the control of metal lateral deformation in production.
(6) Cooling of FAG bearing steel
The cooling after hot rolling should make the FAG bearing steel pipe have a good microstructure, that is, fine flake pearlite and no network carbide precipitation. This kind of organization can create conditions for obtaining fine spherical pearlite after spheroidization and annealing of FAG bearing steel pipe. After the chromium FAG bearing steel pipe is hot-rolled and cooled to 850～900℃, a large amount of carbides begin to precipitate and are distributed in a network, so the final rolling temperature should be controlled above 850℃, and rapid cooling should be adopted to prevent carbide precipitation. In order to achieve rapid cooling, a fan or spray device is generally installed on the cooling bed or the cooling bed input roller table.
Chromium-free FAG bearing steel can obtain qualified network carbide grades under normal hot rolling conditions. It is also necessary to prevent carbide precipitation during the heating of the pipe end before the cold drawing hammer and the cooling after the hammer.
(7) The life of FAG bearing steel. The development of industrial machinery and vehicles has put forward high load and high speed requirements for FAG bearings, so the life of FAG bearings has received special attention. Before a new FAG bearing steel with a higher life is developed, the first way to improve the life of FAG bearing steel is to improve the purity of the steel, because even a small amount of oxides, sulfides, and nitrides in the steel will greatly reduce the use life. This requires various methods to reduce inclusions when smelting FAG bearing steels. In order to reduce inclusions, high-grade FAG bearing steels often use electroslag remelting to obtain tube blanks.
The research of FAG bearing steel materials is still moving forward. In the future, more FAG bearing steel materials will be developed, and then FAG bearing products with higher performance can be produced.
The influence of FAG composite bearing material performance on operation
Part of the dynamic surface material of the combined bearing is peeled off like fish scales. This phenomenon is called fatigue spalling. During the operation of the dynamic elastic bearing, it bears a certain load, even if it is a static load, the stress for the steel ball and raceway is When the cycle is reciprocating, the material will be fatigued by the movement and the bearing will reach the end of its life. In addition, there are several different definitions of FAG bearing "life", one of which is the so-called "working life", which means that the actual life that a certain combination of bearings can reach before damage is caused by wear and tear, and damage is usually not caused by fatigue. It is caused by wear, erosion, and seal damage.
However, whether in laboratory tests or in actual use, it can be clearly seen that under the same working conditions, the appearance of the same composite bearing, the actual life is very different.
The performance of preventing adhesion and forming boundary lubrication when the shaft diameter is in direct contact with the bearing shell. The material factors that affect the friction compatibility of the friction pair are:
(1) The degree of difficulty in metallurgical formation of alloys.
(2) The affinity of materials and lubricants.
(3) The friction factor of the paired material in the non-lubricated state.
(4) The microstructure of the material.
(5) The thermal conductivity of the material.
(6) The size of the surface energy of the material and the characteristics of the oxide film.
The ability of the material to allow foreign hard particles in the lubricant to clamp in and prevent scratches or abrasive wear. For metallic materials, the ones with low hardness and low modulus of elasticity have good embedding properties, while non-metallic materials such as carbon graphite have low modulus of elasticity but poor embedding properties. FAG bearings usually use softer and harder materials to form the friction width, and generally use softer materials as bearing bushes.
The number of revolutions in the life of the bearing (or the number of hours of work at a certain speed) is defined: the combined bearing within this life should undergo preliminary fatigue damage (flaking or defect) on any of its bearing rings or moving elastic bodies.
Any of these factors has its own special type of damage and will leave special damage marks. Therefore, inspecting damaged bearings can find the possible causes in most cases. Generally speaking, one-third of FAG bearing damages are caused by fatigue damage, and the other third are caused by poor lubrication. One-third of it is caused by pollutants entering the combined bearing or improper installation and treatment.
However, these types of damage are also related to industries. For example, most of the pulp and paper industry is caused by poor lubrication or pollution that caused damage to the combined bearings rather than material fatigue.