常见问题

Magnet Basics

A permanent magnet is a solid material that produces its own consistent magnetic field because the material is magnetised. Unlike permanent magnets, the magnetic field exerted by an electromagnet is produced by the flow of electric current. The magnetic field disappears when the current is turned off. Typically, an electromagnet consists of many turns of copper wire which form a solenoid. When an electric current flows around the solenoid coil, a magnetic field is created. If an iron core is inserted into the bore of this solenoid, then magnetism is induced into it and it becomes magnetic, but when the current stops flowing it immediately becomes nonmagnetic. 

There are five types of modern permanent magnets, each made from different materials with different characteristics. The strongest magnets, referred to as rare earth magnets, are commonly known as neodymium magnets which are made from an alloy of neodymium, iron and boron (NdFeb) and samarium cobalt magnets which are made from samarium, cobalt and small amounts of iron, copper and other materials. Other types of permanent magnets include ferrite magnets, made from a compound of ceramic material and iron oxide (SrO.6Fe2O3) and alnico magnets made from aluminium, nickel and cobalt and flexible rubber. 

A magnet’s poles are the surfaces from which lines of magnetism leave a magnet and reconnect on return to the magnet. The pole of a magnet is the area which has the greatest magnetic field strength in a given direction. Each pole is either north facing or south facing.
If you break a magnet into two pieces each piece will still have a north pole and a south pole. No matter how small the piece of magnet is, it will always have a north pole and a south pole. Despite some claims on the internet there is no such thing as a monopole magnet.

Both the north pole or south pole of a magnet are equal in holding power and both will stick to magnetic material such as steel or iron. The like poles of two magnets (e.g. north facing north or south facing south) will always repel each other while opposite poles (e.g. north facing south or south facing north) will always attract. We supply self-adhesive and countersunk magnets with either pole on the magnetic face.

Rare earth magnets are made out of the rare earth group of elements in the periodic table and are famous for their strength. The most common are neodymium-iron-boron (NdFeb) and samarium cobalt (SmCo) varieties. Despite the name, rare earth elements are relatively abundant in the earth’s crust, however, they are not typically found in economically exploitable deposits and are often dispersed, deriving the term ‘rare earth.’

There are many different grades of neodymium commercially available ranging from N35 to N55, along with other high-temperature variations. The ‘N’ grade relates to the maximum energy product of the magnet, a measure of the magnet’s strength. For example, an N35 neodymium magnet will have a maximum energy product of 35 Mega-Gauss Oersted (MGOe) and an N55 will have a maximum energy product of 55 Mega-Gauss Oersted. Generally speaking, the higher the grade, the stronger the magnet.
You will sometimes see variations of the ‘N’ rating with one or two letters following the number, these denote high-temperature grades and each will have a different maximum operating temperature.

Most magnets can be bonded in place with two-part epoxy adhesives. We recommend Araldite Rapid which sets hard in about 5 minutes. We also recommend Loctite Industrial strength Adhesive which has a similar setting time. Both these have a proven track record of reliably bonding magnets to most surfaces with the exception of certain polythene type plastics.

Magnets can be machined. Hard magnet materials are difficult to machine. Magnets should be machined before magnetization as far as possible. Neodymium magnets should be machined before coating as well. In general, it is best to order the magnets in their final shape and avoid machining by yourself.

No, permanent magnets are not affected by time. But, they can lose their magnetic properties (non reversible) when exposed to heat (above working temperature), mechanical stress or stronger magnetic field.

Permanent magnets magnetic characteristics decrease when exposed to heat. These loses are reversible and when the magnets return to room temperature, magnetic properties return to “normal”. All magnets characteristics are normalized to 20°. The effect of heat is different to each type of magnet and even different grades of the same type of magnet. For example neodymium magnets are more affected by heat then samarium cobalt magnets.

The information above is specifically about heat affect within the working temperatures. Exposing the magnets to temperatures above working temperature will cause irreversible losses of magnetic properties.

The strength of a magnetic field drops off exponentially over distance.The bigger the distance, the bigger the drop in pull force. The distance between the magnet and its objective is called “air gap” and it could be through any non magnetic material such as plastic, wood etc.

Yes. You can magnetize magnets that have lost his magnetic properties as long as the magnet did not lose its inner particles alignment, as in case it was exposed to extreme heat.

Ferromagnetic metals will be attracted, such as iron, nickel, cobalt and gadolinium, including materials that contain these elements such as steel.

We use gaussmeter, Magnetometers, or Pull-Testers in our magnetic laboratory. At home you can use small steel weights and use them to test the pulling strength of the magnet.

The strongest type of magnets available for commercial use is the neodymium magnets, and the strongest grade is the N55 grade neodymium.

No, both have the same strength.

The Curie temperature of a magnet is the temperature above which it becomes completely demagnetize.

Yes. Most of the magnets we sell are custom made according to the customer requirements. You can order different shapes, sizes, grades etc. You can decide what finishing, plating, marking and more.