One of the main applications of deformable hard magnetic alloys — production of permanent magnets. In this article, we will look at what steels are used in this industry and what properties they have.
Steels based on the Fe-Ni-Al and Fe-Co-Ni-Al systems belong to the group of dispersion-hardening materials that are manufactured by dispersive hardening. This method of production involves artificial “aging”, during which the supersaturated solidified solution is thermomagnetically treated after annealing. This makes it possible to distribute particles of strong and weakly magnetic phases in accordance with the directions of the applied magnetic fields.
Magnets made from the presented alloys, such as 20NU, 22NU, 24KNU, etc., have high strength and plasticity. They are used in the manufacture of electric motors, electrical measuring devices and radio equipment.
Cobalt-platinum materials have the highest plasticity. They are suitable for manufacturing parts of any configuration and size, including wire or foil a few microns thick. Due to their high cost, they are mainly used for the manufacture of miniature and subminiature magnetic systems. The material is heat treated to a highly coercive state not when it is released, but during the manufacture of the required pieces of equipment.
Iron-Palladium and iron-platinum materials also have high magnetic properties and the ability to cold deformation. At the same time, cold deformation can be used not only to change the size and shape of the metal, but also to give it the required magnetic properties.
Iron-Cobalt-Vanadium alloys, such as 52KFA, 52KFB, 52KFV and 52KFTM, are used for the production of small-sized magnets. They are available in the form of wire with diameters from 0.5 to 3.0 mm, strips and tapes with a thickness of 0.2 to 1.3 mm and a width of not more than 20.1 mm.
52KF steels are materials who magnetic properties are formed during cold deformation. At the same time, the magnetic qualities of wire significantly exceed the characteristics of sheet metal. This is due to the difference in structures and the difference in the stress state during deformation.
The 12GN alloy is available in the form of cold-rolled sheets or strips with a thickness of 0.8 mm. After tempering, it retains high plasticity and can be subject to additional machining, including repeated processing cold deformation.
Cunico alloys based on the Cu-Ni-Co system and kinife based on Cu-Ni-Fe are easily magnetized, and the distribution of their magnetic axes coincides with the direction of deformation. They have a high coercive force and crystallographic structure. They are made in the form of strips, sheets and wires. They are used for the production of permanent magnets, as well as magnetic recording media.
Iron-chromium-nickel materials such as 36NHTYU, have increased plasticity and a high degree of rectangular hysteresis loop. It is used to create small-sized permanent magnets designed for use in extreme climatic conditions and subject to various mechanical loads (shock, vibration, etc.). They are also used for the production of elements with a given magnetic stiffness. They are manufactured in the form of wire with a diameter of 0.2 to 2.0 mm or cold-rolled strip with a thickness of 0.005 to 1.0 mm.
Metals based on the Mn-Al system are characterized by high coercive strength, low oxidizability, corrosion resistance and low specific gravity. They are easy to machine. Cold deformation, as well as metal alloying, are used to improve magnetic properties with iron, cobalt, titanium, molybdenum or carbon.
Precision alloys based on Mn-Ca have good plasticity, low residual induction and high coercive force. Maximum magnetic properties are achieved by preliminary cold deformation and final annealing at a temperature of 450°C.
High-carbon materials based on the Fe-Al-C system are cooled at a critical rate and then tempered to achieve the required magnetic properties. Such precision alloys can be alloyed with chromium and molybdenum. Despite the presence of carbon, these materials are easy to be hot deformed at a temperature of 1180-1200°C and machined. They are used in low-power magnetic systems, including measuring instruments and DC motors.
