Through the magnetic fluid formed under the action of the magnetic field, the non-magnetic abrasive particles suspended in it can be pressed against the rotating workpiece for grinding and polishing under the action of the flow force and buoyancy of the magnetic fluid, thereby improving the quality and efficiency of finishing. It can obtain a machined surface with Ra≤0.01μm without a metamorphic layer, and can polish workpieces with complex surface shapes. Because the magnetic field lines of the magnetic field and the magnetic fluid formed by them do not directly participate in the removal of materials, it is called magnetic field-assisted processing.
Magnetic fluid is composed of magnetic particles, surfactants and liquid carriers (such as water, oil, etc.). The average particle size of the magnetic particles is about 10urn, which is surrounded by organic molecules of stable surfactants, and becomes a stable magnetic particle colloid, suspended in an oil-based or water-based liquid carrier. For example, CY3-1 metal magnetic fluid is made of Fe3O4 magnetic material (mass fraction 10%-30%) with a particle diameter of 7.5-10nm, dispersed in mineral oil with surfactant oleic acid (mass fraction 40%-60%) In the carrier, its saturation induction intensity is 0.023T, density is 1.2g/mL, and dynamic viscosity is 20×10-3Pa·s. Because the magnetic moment of the magnetic particles is very large, they will not be precipitated by gravity, and their magnetization curve has no hysteresis, and the magnetization can increase with the increase of the magnetic field strength, so as to realize the control of the workpiece force and the processing amount.
This magnetic grinding process originated in the United States in the 1940s, and was developed by researchers in the former Soviet Union and Bulgaria in the late 1950s and early 1960s. By the 1970s, it has been shown that this technology can be used in the finishing of most heavy workpieces. Since the late 1980s, Japan has further studied its processing principle and equipment, and its application in the field of finishing has been developed. In the 1990s, researchers in Japan, the United Kingdom and the United States continued to expand its technology and equipment. And perfect, and apply the finite element method to simulate the magnetic polishing process, analyze the motion characteristics of magnetic fluid and abrasive particles under magnetic induction, which greatly promotes the development and application of this process.