Product
AlNiCo magnet, main composition of aluminum, nickel, cobalt, iron, copper and titanium, is the first generation of permanent magnet commercially manufactured. They are still extensively used relying upon its decisive advantages of excellent thermal stability and corrosion resistance,though it is with lower (BH)max than rare earth magnet and the lowest coercive force in permanent magnet family. The AlNiCo alloy cost per gram is much cheaper than SmCo magnet,but its reversible temperature coefficient is lower than or equivalent to most grade of SmCo magnet, particularly its coefficient of coercive force of most grades is plus. The application of AlNiCo magnet mainly covers electroacoustics, actuator, meter, relay, sensor, DC motor and amplifier for defense, aerospace,electric power supply, automotive, musical instrument and others. It is specially tailored for temperature-sensitive component such as automotive and electronic sensors.
Our source, established in 1980 with annual output capability of 1800 metric ton, approx. 20% of the world output, is the biggest producer of both cast and sintered AlNiCo magnet in China with fully equipped R&D centre. Also she is standing at the leading position among AlNiCo magnet producers on quality improvement, cost control and new product development. Quality assurance systems ISO9001 and ISO/TS16949 have been introduced and authenticated by the third party. By right of advanced management for instance lean production and 6 sigma in producing processes and great volume of purchasing raw material, the product possesses competitive price. The creative grade LNGT88 is with maximum energy product 11MGOe what has doubled the commonly used AlNiCo5. Today the source has set up steady cooperation with SIEMENS, GE, SCHNEIDER and other prestigious companies.
Cast AlNiCo Magnet and Sintered AlNiCo Magnet
Casting and sintering processes are the 2 basic methods of producing AlNiCo magnet. Generally casting process is more commonly applied for manufacturing AlNiCo magnet to achieve magnet with higher magnetic property. Sintering process is suitable for manufacturing small figure and/or complex geometry magnet. Furthermore, sintered AlNiCo magnet is with stronger structure property and closer dimension of net shape. Also sintering process is the more efficient method to manufacture big quantity products. Both cast AlNiCo magnet and sintered AlNiCo could be available at isotropic or anisotropic property. The anisotropy of AlNiCo magnet is taken place in heat treatment process by cooling down product at a controlled rate and being induced by an external magnetic field.
Magnet Shape And Dimensional Tolerance
The best properties of cast AlNiCo magnets are achieved in shape of columnar or single crystal structure with the direction of magnetization parallel to the grain axis. In principle any geometry requirement of AlNiCo magnet is available by casting or sintering process and subsequent machining process. As AlNiCo magnets are coarse-grained, hard and brittle, except surface finishing by grinding, usually other machining process on magnet is not recommended. Before grinding, the dimensional tolerance of un-ground AlNiCo magnet is as follows:
¡öSintered AlNiCo Magnet
Dimension |
Tolerance |
0-3.2mm |
¡À0.10mm |
3.2-16mm |
¡À0.20mm |
16-32mm |
¡À0.40mm |
¡öCast AlNiCo Magnet
Dimension |
Tolerance |
0-25mm |
¡À0.40mm |
25-75mm |
¡À0.80mm |
75-125mm |
¡À1.2mm |
125-175mm |
¡À1.6mm |
175-225mm |
¡À2.0mm |
225-275mm |
¡À2.4mm |
Other definitions on tolerance of concentricity, roundness, squareness, perpen-dicularity and others please refer to MMPA standard No. 0100-00 or DIN17410 or ISO2768. After grinding process, precise deviation even ¡À0.015mm could be achieved.
Thermal property
Among permanent magnets family,AlNiCo magnet is with the best thermal stability. It is with the highest maximum working temperature and the highest Curie temperature respectively up to 550¡æ and 850¡æ. Most grades of AlNiCo magnet are with the lowest reversible temperature coefficient of remanence from -0.03%/¡æ to -0.014%/¡æ. Only few grade AlNiCo magnet is with negative reversible temperature coefficient of intrinsic coercivity -0.02%/¡æ,others are with plus reversible temperature coefficient +0.02~+0.03%/¡æ depending on material composition. Heating treatment on magnetized AlNiCo magnet can produce an irreversible loss about 5% of magnetic strength,but will prevent further force loss if AlNiCo magnet is used within maximum working temperature 550¡æ.
Other characteristics
The corrosion behavior of AlNiCo magnet is dependent on their composition and working condition. AlNiCo magnet is with excellent resistance against motor oil,organic solvents,petrol and alcohol. It displays limited resistance against hydrogen peroxide,acetic acid and organic acids with concentration below 10%. Inorganic acids,salt water,citric acid,tartaric acid and strong alkaline solutions can corrode AlNiCo magnet.
Usually AlNiCo magnet does not need to be coated. Sometimes coating of nickel or zinc and spraying of paint will be applied for clean or decoration purpose. Plastic coating on AlNICo magnet is suggested when it will directly touch foods due to cobalt content though AlNiCo magnet itself is non toxic and environmentally neutral.
Influenced by its low coercivity,AlNiCo magnet could be easily demagnetized. Due to this shortage,the design of AlNCo magnet is suggested with long aspect ratio. Also magnetization after being assembled into the final magnetic circuit is recommended to eliminate demagnetization in transportation,warehousing and assembling processes. For some applications,intentionally reducing magnetic output by 5% to 10% in advance could reduce or even eliminate the effect of external fields.