Magnet Technical Information
Designing with magnetic material: Polymagnets and conventional magnets
The field of magnetics uses specialized terminology to detail the technical characteristics of magnetic material. Mechanical designers, however, require more practical data to design products with magnetics. The Polymagnet website and datasheets provide practical data on strength, size and behavior for each magnet design - including the conventional magnet of the same size. Rather than using theoretical magnet strength data, the Polymagnet.com datasheets show measured data for a typical magnet under standard ambient conditions with different metal thicknesses.
Magnetic fields interact with ferrous metals and other magnets. The strength of magnetic system depends greatly on the geometry of the system. Critical parameters include the type of magnet, type of target (magnet or type of metal), thickness of the target and gap between the surface of the magnets or to the ferrous metal.
Magnetic Material Used for Polymagnets
Polymagnets are available in two permanent magnet materials, Neodymium and Samarium Cobalt.
Neodymium ("Neo", NIB, NdFeB) is the strongest type of magnetic material. It is primarily made from Iron with smaller amounts of Neodymium and Boron. Some grades of magnets include small amounts of Dysprosium and Cobalt as well as other trace elements. Neodymium is available in a wide range of strength "grades" and working temperatures. The chart below shows the magnetic grades that are available. The true measure of a magnets capability is the measured data shown on the Polymagnet datasheets.
|Magnet Grade||Residual Flux Density (Br)||Coercive Force (Hc)||Intrinsic Coercive Force (Hci)||Max.Energy Product (BH)max||Max Working Temp Tmax|
|N40||12.5-13.1 KGs||11.0 KOe||12 KOe||38-41 MGOe||80 C|
|N45||13.2-13.8 KGs||11.0 KOe||12 KOe||43-46 MGOe||80 C|
|N50||13.9-14.6 KGs||10.5 KOe||12 KOe||47-51 MGOe||80 C|
|N52||14.2-14.9 KGs||10.5 KOe||12 KOe||49-53 MGOe||80 C|
|N40M||12.5-13.1 KGs||11.5 KOe||14 KOe||38-41 MGOe||100 C|
|N45M||13.2-13.8 KGs||12.2 KOe||14 KOe||43-46 MGOe||100 C|
|N50M||13.9-14.6 KGs||13.0 KOe||14 KOe||47-51 MGOe||100 C|
|N40H||12.5-13.1 KGs||11.5 KOe||17 KOe||38-41 MGOe||120 C|
|N45H||13.2-13.8 KGs||12.2 KOe||17 KOe||43-46 MGOe||120 C|
|N50H||13.9-14.6 KGs||13.0 KOe||16 KOe||47-51 MGOe||120 C|
Samarium Cobalt (SmCo) magnets are strong permanent magnets made from an alloy of Samarium and Cobalt.An SmCo magnet has less strength than Neodymium of the same size, but it is more appropriate for applications that require high temperatures. SmCo magnets are resistant to corrosion and generally do not require a plating except to provide protection from wear.
For mechanical design, the most important characteristic is the measured force curve available on the Polymagnet datasheet. Another important characteristic is the maximum working temperature for that type of magnet.
Neodymium's strength will gradually degrade if exposed to temperatures above the rated working maximum.
In most practical applications, temperature is the primary factor that affects the strength of a Neodymium magnet. The magnetic properties of permanent magnets are not affected by typical shock and vibration. External magnetic fields are very unlikely to affect a permanent magnet since the magnetic field required to magnetize or demagnetize Neodymium or Samarium Cobalt is very strong – only specialized magnetizing equipment can create such a strong magnetic field.
SmCo has a very high working temperature and is typically used in harsher environments where temperature and corrosion resistance are important. While standard SmCo magnets have less strength than Neodymium magnets of the same size, patterning with Polymagnet technology focuses the available magnet energy to approach the holding strength of standard Neodymium. The SmCo Polymagnet datasheets provide a strength comparison between the SmCo Polymagnet and conventional magnets made from Neodymium and SmCo.
Polymagnet magnetization technology produces patterned magnets with the same temperature and lifetime characteristics as conventional magnets. All magnets should be treated with care since Neodymium and Samarium Cobalt materials are brittle.
Magnets are available off the shelf in a wide variety of shapes and sizes. The industry's manufacturing technique for magnets is to machine a larger block of material into the finished shape and size. Machining of magnet material is limited to specialized equipment to grind and cuts with abrasive tools. A finished and plated magnet should never be machined with standard machining equipment.
Custom magnet shapes are available as a special order. The CMR sales organization will provide a quote on custom sized magnets. In addition, custom Polymagnet design services are available - please contact a sales representative listed on the Contact page or complete the Contact form.
A Starrett FMS2500 Force Measurement System is used to conduct controlled measurements of the magnet's holding force. The system utilizes aluminum adapters and fixtures to ensure that the magnet is held parallel to the target metal, or complement magnet, throughout the test. Real world testing may give lower forces due to the magnet tilting away from target during engagement and disengagement.
Finished Neodymium magnets are always supplied with a protective coating. When exposed to the atmosphere, uncoated Neodymium magnets will corrode and lose magnetic strength. Most standard Polymagnet.com magnets are available with standard Nickel plating.
The standard coating for Neodymium is a 3-layer Nickel-Copper-Nickel plating. Standard Nickel plating is the best and least expensive option for most applications. Other coatings are available and include epoxy, plastic or CVD coatings such as Parylene. Each coating has a different mechanical characteristic and is best for a different environment. CMR's sales group will recommend that best coating option for applications with most harsh conditions or unique mechanical requirements.
Importance of Licensed Magnet Material
Polymagnet.com uses only manufacturers of licensed magnetic material. This magnetic material is manufactured under precisely controlled conditions and is the highest quality material available. High quality material offers stable performance within the working temperature range and consistent material provides predictable performance.
RoHS and REACH Certification
Neodymium magnets supplied by Polymagnet.com are “RoHS” and RoHS II compliant. Such magnets do not exceed the designated levels of Cadmium, Hexavalent Chromium, Mercury, Lead, Polybrominated Biphenyls or Polybrominated Diphenyl Ethers.
Additionally, typical neodymium magnets supplied via CMR do not contain Deca Brominated Diphenyl Ether (Deca BDE) legislated under the provisions of the European Commission Decision of 13 October 2005 (2005/717/EC), do not contain as intentional additives Perfluoroocantylsulfonates (PFOS) legislated under the provisions of the European Parliament and Council Directive 2006/122/EC (30th amendment to EU Directive 76/769/EEC), and do not require any exemptions per “RoHS2.”
Typical neodymium magnets supplied by CMR do not contain Substances of Very High Concern (SVHC) as listed by the European Chemicals Agency (ECHA) under the provisions of Regulation (EC) No. 1907/2006 of the European Parliament and of the council concerning the Registration, Evaluation, Authorization, and Restriction of Chemicals (REACH) per the ECHA 15/06/2015 and previous updates.
To the extent a customer specifies a coating other than standard nickel-copper-nickel, CMR makes no statement as to RoHS and REACH compliance of such coating, but will work with our customers to evaluate RoHS and REACH on a case-by-case basis.
Additional information regarding RoHS or REACH compliance may be requested through the Contact Us form.