There are three kinds of magnetic materials: hard magnetic materials, soft magnetic materials and semi-hard magnetic materials.
Hard magnetic material
Permanent magnets, formerly made of steel, are now mostly replaced by complex alloys containing iron, nickel, aluminium, cobalt and other elements. Aluminum-nickel-cobalt alloys are well known in the United States, while titanium-cobalt alloys are found in some European countries.
Artificial magnet consisting of barium or strontium added to iron oxide, called pottery iron magnet or fertilizer iron, is also widely used as permanent magnet.
Very powerful magnets can also be made from platinum and cobalt alloys or cobalt with rare earth elements, usually samarium, but both methods are expensive.
Most permanent magnets are hard and fragile, so they are sometimes called hard magnetic materials.
However, mechanical hardness is not a necessary condition for permanent magnets. Some alloys that are easy to elongate or quite soft can also be used to make permanent magnets with reasonable magnetic strength.
Soft magnetic material
The core of a metal used in an electromagnet is the line of force generated by the accumulation of current. The most commonly used core materials are iron (wrought iron, soft iron) with relatively high purity or steel with very low carbon content.
If the direction of magnetization in a machine must change rapidly, for example in an AC machine, the iron core must be made into many thin layers or sheets to reduce the circumferential current (called eddy current) caused by the change of magnetization. A small amount of alloying elements, such as silicon, can usually be added to increase the resistance of the material. This phenomenon can be confirmed in some special cases, such as in expensive alloys of iron and nickel (Permalloys) or iron and cobalt.
In high frequency applications, such as radar instruments, nickel or zinc is very useful in some ceramic magnets or ferric oxide because they have very high resistance.
These materials must be able to rapidly magnetize and lose their magnetization. They are called soft magnetic materials in order to distinguish them from hard magnetic materials or permanent magnets.
Soft magnetic materials are widely used in motors, generators and transformers. Other uses include electromagnetic operating switches (relays) and various parts of electromagnetic valves, inductors, magnetic barriers and electronic and computer instruments.
Semi-hard magnetic materials
The magnetic materials used to record sound and television images must have properties between hard and soft magnetic materials.
This magnetic material must be easy and fast to magnetize in order to record data, but cannot lose magnetization under normal storage and processing conditions. Because if the magnetization is lost, the stored data will be lost.
This material can be metal alloys or oxides, sometimes referred to as semi-hard magnetic materials.
Next, for you to introduce the production of magnetic materials used in the vacuum pump.
Water-ring vacuum pump (hereinafter referred to as water-ring pump) is a kind of coarse vacuum pump. The maximum vacuum it can obtain is 2000-4000Pa, and the air ejector in series can reach 270-670Pa. Water ring pump can also be used as a compressor, known as water ring compressor, is a low-pressure compressor, its pressure range is 1-2*10Pa gauge pressure. Water ring pumps were initially used as self-suction pumps, and then gradually used in petroleum, chemical industry, machinery, mining, light industry, medicine and food and many other industrial sectors. In many industrial processes, such as vacuum filtration, vacuum water diversion, vacuum feeding, vacuum evaporation, vacuum concentration, vacuum moisture regain and vacuum degassing, water ring pumps are widely used. Due to the rapid development of vacuum application technology, the water ring pump has been attached great importance in obtaining rough vacuum. Because the gas compression in the water ring pump is isothermal, it can extract flammable and explosive gases, in addition, it can also extract dust and water containing gases. Therefore, the application of the water ring pump is increasing.