An Alnico magnet is a permanent magnet made by combiming aluminum, nickel, iron, cobalt, and other elements. They come in isotropic, non-directional, or anisotropic, mono-directional, form...
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This article will take an in-depth look at magnets.
The article will bring more understanding on topics such as:
This chapter will discuss what magnets are, their manufacturing and how they function.
Magnets are materials that exert a noticeable force on other materials without physically contacting them. This force is called a magnetic force. The magnetic force can either attract or repel. Most known materials contain some magnetic force, however small in these materials. With some materials the magnetic force is so large that these materials are called magnets. The earth is also a huge magnet itself.
There are two points on all magnets where the magnetic force is greatest. They are known as the poles. On a rectangular bar magnet, the poles are directly across each other. They are called the North Pole or north-seeking pole, and the South Pole or south-seeking.
Magnetism occurs when very small particles called electrons behave in a certain way. All matter is made up of units called atoms and these in turn are made up of electrons and other particles which are neutrons and protons. These electrons tend to spin around the atom’s nucleus, which contains the other mentioned particles. Tiny magnetic forces are caused by the spinning of these electrons and in some instances a lot of the electrons in an object spin in one direction. The result of all these tiny magnetic forces from the electrons is one big magnet.
A magnet can be simply made by taking an existing magnet and rubbing a piece of metal with it. This metal piece being used must be rubbed continuously in one direction. This makes electrons in that metal piece start spinning in the same direction. Electric current is also capable of creating magnets. Since electricity is a ﬂow of electrons, when the mobile electrons move in a wire they carry with them the same effect as electrons spinning around the atomic nucleus. This is called an electromagnet.
Due to the way their electrons are arranged, the metals nickel, cobalt, iron, and steel make very good magnets. These metals can stay magnets forever once they become magnets. Thus carrying the name hard magnets. However these metals and others can behave like magnets temporarily if they have been exposed or come near a hard magnet. Then they carry the name soft magnets.
Most of the materials taking for example, wood, water, and air have magnetic properties which are very weak. Magnets attract objects that contain the former metals very strongly. They also attract or repel other hard magnets when they are brought closer. This result is because every magnet has two opposite poles. The south poles attract the north poles of other magnets, but they repel other south poles and vice versa.
The most common method used in manufacturing magnets is called powder metallurgy. Since magnets comprise different materials, the processes of manufacturing them are also different and unique on their own. For example, electromagnets are made using metal casting techniques, while flexible permanent magnets are manufactured in processes involving plastic extrusion in which raw materials are mixed in heat before being forced through an opening under extreme pressure conditions. Below is the process of magnet manufacturing.
Suitable amounts of iron, boron, and neodymium are heated to melt under a vacuum or in an induction melting furnace using inert gas. The use of the vacuum is to prevent chemical reactions between the melting materials and air. When the molten alloy has cooled, it is broken and crushed forming small metal strips. Afterward, the small pieces are pulverized and crushed into a fine powder which ranges from 3 to 7 microns in diameter. The newly formed powder is highly reactive and is able to cause ignition in air and must be kept away from exposure to oxygen.
The process of isostatic compaction is also called pressing. The powdered metal is taken and positioned in a mold. This mold is also called a die. In order for the powdered material to be in line with the powder particles a magnetic force is exerted, and during the period the magnetic force is being applied, hydraulic rams are used to compress it wholly to within 0.125 inches (0.32 cm) of its planned thickness. High pressures are used usually from 10,000 psi to 15,000 psi (70 MPa to 100 MPa). Other designs and shapes are manufactured by putting the substances in an airtight evacuated container before pressing them into the desired shape by gas pressure.
After the process of isostatic compaction the slug of the powdered metal is separated from the die and put in an oven. Sintering is the process or method of adding heat to compressed powdered metals in order to transform them into fused, solid metal pieces afterward.
The sintering process mainly comprises three stages. During the initial stage process, the compressed material is heated at very low temperatures in order to drive away all moisture or all the contaminant substances that may have been entrapped during the isostatic compaction process. During the sintering second stage, there is a rise in temperature to about 70-90% of the alloy’s melting point. The temperature is then held there for a space of hours or days in order for the small particles to match, bond and fuse together. The final stage of sintering is when the material is cooled very slowly in controlled temperature increments.
After the heating process comes the process of annealing. This is when the sintered material undergoes another step by step controlled heating and cooling process in order to discard any or all residual stresses that are left within the material and make it stronger.
The above sintered magnets consist of some level or degree of machining, ranging from grinding them smooth and parallel or forming smaller parts out of block magnets. The material making the magnet is very hard and brittle (Rockwell C 57 to 61). Therefore this material needs diamond wheels for the slicing processes, they are also used for abrasive wheels for the grinding processes. The process of slicing can be done with great precision and usually removes the need for the process of grinding. The above mentioned processes require to be done very carefully in order to reduce chipping and cracking.
There are cases where the ﬁnal magnet structure or shape is very conducive to processing with a shaped diamond grinding wheel like bread loaves. The end result in the ﬁnal shape is brought past the grinding wheel and the grinding wheel provides accurate and precise dimensions. The annealed product is so close to the finished shape and dimensions that it is desired to be made. Near net shape is the name that is usually given to this condition. A last and final machining process removes any excess material and presents a very smooth surface where needed. Finally in order to seal the surface the material is given a protective coating.
Magnetizing follows the finishing process, and when the manufacturing process is done, the magnet needs charging in order to produce an external magnetic ﬁeld. To achieve this, solenoid is used. A solenoid is a hollow cylinder into which different magnet sizes and shapes can be placed or with ﬁxtures a solenoid is crafted to impart various magnetic patterns or designs.in order to avoid handling and assembling these powerful magnets in their magnetized conditions large assemblies can be magnetized. Consideration should be done to the magnetizing ﬁeld requirements, which are very substantial.
All crucial and important aspects of selection of magnets should be brought under discussion with both engineering and production teams. The magnetizing process on the manufacturing processes of magnets, to this point, the material is a piece of compressed metal. Though it was exerted onto a magnetic force during the process of isostatic pressing, the force did not bring a magnetic effect to the material, it only lined up the loose powder particles. The piece is brought between the poles of a strong electromagnet and afterwards oriented in the direction intended of magnetization. After the electromagnet is energized, the magnetic force aligns the magnetic domains within the material, making the piece a very strong permanent magnet.
The different types of magnets include:
Alnico magnets exist in the cast, sintered, and bonded versions. The most common are cast alnico magnets. They are a very crucial group of permanent magnet alloys. The alnico magnets contain Ni, A1, Fe, and Co with some minor additions of Ti and Cu. The alnicos have relatively very high coercivities because of the shape anisotropy of Pe or Fe, Co particles. These particles are precipitated in a weakly ferromagnetic or non-ferromagnetic Ni—Al matrix. After cooling, the isotropic alnicos 1-4 are tempered for several hours at a high temperature.
Spinodal decomposition is the process of phase separation. Final sizes and shapes of the particles are determined in the very early stages of the spinodal decomposition. Alnicos have the best temperature coefficients so over a temperature change they have the least change in field output. These magnets can operate at the highest temperatures of any magnet.
Demagnetization of the alnicos can be reduced if the working point is improved, such as for making use of a longer magnet than before in order to increase the length to diameter ratio which is a good rule of thumb guide for the Alnico magnets. All external demagnetizing factors must be taken into consideration however. A huge length to diameter ratio and a good magnetic circuit may also be required.
Bar magnets are rectangular pieces of objects, which are made up of steel, iron or any other ferromagnetic substance that have characteristics or strong magnetic properties. They consist of two poles, a north pole and a south pole.
When the bar magnet is suspended freely, it aligns itself so that the north pole points towards the direction of the magnetic north pole of the earth.
There are two types of bar magnets. Cylindrical bar magnets are also called rod magnets and they have a very high thickness in the diameter enabling their high magnetism property. The second group of bar magnets are rectangular bar magnets. These magnets ﬁnd most applications in the manufacturing and engineering sectors as they have magnetic strength and ﬁeld greater than other magnets.
If a bar magnet is broken from the middle, both pieces will still have a north pole and a south pole, even if this is repeated several times. A bar magnet’s magnetic force is strongest at the pole. When two bar magnets are brought close to each other, their unlike poles definitely attract and like poles will repel each other. Bar magnets attract ferromagnetic materials such as cobalt, nickel, and iron.
Bonded magnets have two main components: a non-magnetic polymer and a hard magnetic powder. The latter can be made from all sorts of magnetic materials, including alnico, ferrite and neodymium, cobalt and iron. Two or more magnetic powders can also be mixed together thereby forming a hybrid mixture of the powder. The properties of the powder are carefully optimized through chemistry and step by step processing which aims to utilize a bonded magnet no matter what the materials are.
Bonded magnets have numerous advantages in that the near net shape manufacturing requires no or low finishing operations when compared to other metallurgical processes. Therefore value added assemblies can be made economically in one operation. These magnets are a highly versatile material and they consist of multiple processing options. Some advantages of bonded magnets are that they have excellent mechanical properties and great electrical resistivity when compared with sintered materials. These magnets are also available in different complex sizes and shapes. They have good geometric tolerances with very low secondary operations. They are also available with multipole magnetization.
The term ceramic magnet refers to Ferrite magnets. These ceramic magnets are part of a permanent magnet family. They are the lowest cost available when compared to other magnets. Materials that make ceramic magnets are iron oxide and strontium carbonate. These ferrite magnets have a medium magnetic strength ratio and they can be used at high temperatures. One special advantage they have is that they are corrosion resistant and very easy to magnetize, making them the first choice for a lot of consumers, industrial, technical and commercial applications. Ceramic magnets have different grades with the commonly used being Grades 5. They are available in different shapes such as blocks and ring shapes. They can also be custom manufactured to meet the customer’s specific requirements.
Ferrite magnets can be used at high temperatures. The magnetic properties of ceramic magnets drop down with temperature. They also require special machining skills. Another added advantage is that they do not need to be protected from surface rust because they comprise a film of magnet powder on their surface. On bonding, they are often attached to products by making use of superglues. Ceramic Magnets are very brittle and hard, breaking easily if dropped or smashed together, so extra caution and care are needed when handling these magnets.
Electromagnets are magnets in which an electric current causes the magnetic field. Usually they consist of a wire that is wound into a coil. The current creates a magnetic field through the wire. When the current is turned off the magnetic field disappears. Electromagnets consist of wire turns which are usually wound around a magnetic core that is made from a ferromagnetic field. The magnetic ﬂux is concentrated by the magnetic core, producing a more powerful magnet.
An advantage of electromagnets compared to permanent magnets is that a change can be applied quickly to the magnetic field by regulating the electric current in the winding. However, a major drawback of electromagnets is that there is a need for a continuous supply of current to maintain the magnetic field. Other drawbacks are that they heat up very fast and consume a lot of energy. They also discharge huge amounts of energy in their magnetic field if there is an interruption on the electric current. These magnets are often used as components of various electrical devices, such as generators, relays, electro-mechanical solenoids, motors, loudspeakers, and magnetic separation equipment. Another great use in industry is for moving heavy objects and picking up iron and steel crap. Some few properties of electromagnets are that magnets attract ferromagnetic materials like nickel, cobalt, and iron and like most magnets like poles move away from each other while unlike poles attract each other.
Flexible magnets are magnetic objects designed to flex without breaking or otherwise sustaining the damage. These magnets are not hard or stiff, but can actually be bending. The one above shown in figure 2:6 may be rolled up. These magnets are unique because other magnets cannot bend. Unless it is a flexible magnet, it won't bend without deforming or breaking. A lot of flexible magnets have a synthetic substrate that has a thin layer of ferromagnetic powder. The substrate is a product of very flexible material, like vinyl. The synthetic substrate becomes magnetic when the ferromagnetic powder is applied to it.
Many production methods are applied for manufacturing these magnets, however almost all of them involve the application of ferromagnetic powder to a synthetic substrate. The ferromagnetic powder is mixed together with an adhesive binding agent until it sticks to the synthetic substrate. Flexible magnets come in different types for example sheets of different designs, shapes, and sizes are usually used. Motor vehicles, doors, metal cabinets and buildings make use of these flexible magnets. These magnets are also available in strips, the strips are thinner and longer as compared to sheets.
On the market they are usually sold and packaged in rolls. Flexible magnets are versatile with their bendable properties and they can wrap around machines so easily as well as other surfaces and components. A flexible magnet is supported even with surfaces which are not perfectly smooth or flat. Flexible magnets can be cut and shaped into desired shapes and sizes. Most of them can be cut even with a traditional cutting tool. Flexible magnets are not affected by drilling, they will not crack but they will form holes without damaging the surrounding magnetic material.
An Industrial magnet is a very powerful magnet that is used in the industrial sector. They are adaptable to different kinds of sectors and they can be found in any shape or size. They are also popular for their numerous grades and qualities for keeping the properties of residual magnetism. Industrial permanent magnets can be made of alnico, rare earth, or ceramic. They are magnets which are made of a ferromagnetic substance which is magnetized by an outward magnetic field, and are capable of being in a magnetized state over a long period of time. Industrial magnets maintain their state without outward assistance, and they consist of two poles that show a rise in intensity near the poles.
Samarium Cobalt Industrial magnets can withstand high temperatures of up to 250 °C. These magnets are very resistant to corrosion since they do not have iron trace elements in them. However this magnet type is very costly to produce due to the high production cost of cobalt. Since cobalt magnets are worth the results they produce of very high magnetic fields, samarium cobalt industrial magnets are usually used in high operating temperatures, and make motors, sensors, and generators.
Alnico Industrial Magnet consists of a good combination of materials which are aluminum, cobalt, and nickel. These magnets may also include copper, iron, and titanium. In comparison to the former, alnico magnets are more heat-resistant and can withstand very high temperatures of up to 525 °C. They are also easier to demagnetize because they are highly sensitive. Industrial Electromagnets are adjustable and can be switched on and off.
The industrial magnets can have uses such as:
They are used to lift sheet steel, iron castings, and iron plates. These strong magnets are used in numerous manufacturing companies as high-powered magnetic devices that make work for the workers easy. The industrial magnet is put on top of the object and afterwards the magnetis is turned on to hold the object and make the transfer to the desired location. Some of the advantages of using industrial lifting magnets are that there is a very lower risk of muscle and bone problems amongst the workers.
Making use of these industrial magnets helps manufacturing workers shield themselves from injuries, removing the need to physically carry the heavy materials. Industrial magnets improve productivity in numerous manufacturing companies, because the lifting and the carrying of heavy objects manually is time-consuming and physically draining for workers, their productivity is greatly affected.
The process of magnetic separation involves separating components of mixtures by making use of a magnet to attract magnetic materials. Magnetic separation is very useful for the selection of a few minerals which are ferromagnetic, that is minerals that contain cobalt, iron, and nickel. Many of the metals, including silver, aluminum, and gold are not magnetic. A very large diversity of mechanical ways are usually used to separate these magnetic materials. During the process of magnetic separation, the magnets are arranged inside two separator drums which contain liquids, because of the magnets, the magnetic particles are being driven by the drum movement. This creates a magnetic concentrate for example an ore concentrate.
The process of magnetic separation is also used in electromagnetic cranes that separate magnetic material from unwanted materials. This brings to light its use for waste management and shipping equipment. Unnecessary metals can also be separated from goods with this method. All materials are kept pure. Various recycling facilities and centers make use of magnetic separation to remove components from recycling, separate metals, and to cleanse ores, magnetic pulleys, overhead magnets, and magnetic drums were the historical methods for recycling in industry.
Magnetic separation is very useful in mining iron. This is because iron is highly attracted to a magnet. This method is also applied in processing industries to separate metal contaminants from products. This process is also crucial in pharmaceutical industries as well as food industries. The magnetic separation method is most commonly utilized in situations where there is a need to monitor pollution, control pollution, and the processing of chemicals. The weak magnetic separation method is also used to produce smarter iron-rich products that can be reused. These products have very low levels of contaminants and a high iron load.
Magnetic stripe technology has allowed data to be stored on a plastic card. This was achieved by charging tiny bits magnetically within a magnetic stripe on one end of the card. This magnetic stripe technology has led to the build of the credit and debit card models. This has greatly replaced cash transactions in various countries all over the world. Magnetic stripe can also be called a magstripe. The creation of magnetic stripe cards which have very high durability and uncompromised data integrity, financial institutions and banks have been able to execute all kinds of card based transactions and processes.
Magnetic stripes are in uncountable numbers of transactions every day and are being made useful in numerous types of identification cards. People who specialize in card reading find it easy to quickly extract details off of a magnetic card, which is then sent to a bank for authorization. However, in the past years, a brand—new technology has increasingly come to rival magnetic card transactions. Many professionals refer to this modern method as the contactless payment system because it involves cases where transaction details may be transferred, not by a magnetic stripe, but by signals sent from a small chip. The company Apple Inc. has pioneered contactless payment systems.
These rare earth magnets are permanent magnets. They produce very strong magnetic fields, and The magnetic field produced by these neodymium magnets is over 1.4 teslas. Neodymium magnets have numerous applications outlined below. They are used in the making of hard disk drives which contain tracks and segments that feature magnetic cells. All of these cells are magnetized whenever the data is written to the drive. Another use of these magnets is in loudspeakers, headphones, microphones, and earphones.
The current-carrying coils that are found in these devices are used together with permanent magnets to alter electricity into mechanical energy. Another application is that the small sized neodymium magnets are mostly used to place dentures perfectly in place. These magnets are used in residential and commercial buildings on the doors for safety reasons and total security. Another practical use of these magnets is in making therapy jewelry, necklace, and jewelry. Neodymium magnets are greatly used as anti-lock brake sensors, these anti-lock brakes are installed in cars and numerous vehicles.
This chapter will discuss the applications of magnets.
Magnets are used in many and different ways at different situations and for different purposes. They have different sizes and can range from very small to very large giant like structures computers we use in our day to day lives contain magnets. Magnetic elements are present on hard disks and facilitate the extraction of computer data which is ‘read‘ by the computer code. Magnets are also found inside Televisions, radios, and speakers.
The small coil of wire and a magnet inside a speaker changes the electronic signal to sound vibrations. Generators also use magnets to transform mechanical energy into electrical energy. And they are always present where there are other types of mechanical or electrical motors which use magnets to change electrical energy to mechanical energy.
These magnets can also help cranes to move large metal pieces which cannot be lifted by humans. Magnets are being used in the separation and filtering processes of metallic ores from crushed rocks. They are also used in food processing industries to separate small metallic pieces from grains. There are various applications of these magnets only to mention the few above.
These are some major drawbacks of the magnets above. Molds and the sintered afterward make ferrite magnets. Therefore, they are very difficult to machine, so as a result, most ferrite products have very simple shapes and huge dimensional tolerances. The Samarium Cobalt magnet is very brittle, making it difficult to process small-sized products. Most magnets become denatured at very high temperatures and this is a major drawback of magnets. In addition, neodymium magnets are easily corroded and therefore need to be painted.
Magnets come in different forms, from simple bar magnets to very large permanent industrial magnets. Every type of magnet has two poles and even if they are cut in half, they will still have these two poles. Magnets are of great importance to the human community, but however they can be demagnetized at excessive temperatures and pressure.
An Alnico magnet is a permanent magnet made by combiming aluminum, nickel, iron, cobalt, and other elements. They come in isotropic, non-directional, or anisotropic, mono-directional, form...
A ceramic magnet, also known as a ferrite magnet, is a permanent magnet made by combining iron oxide and strontium carbonate. They are a man made magnet produced by heating the two elements to...
Flexible magnets are composite materials with magnetic components arranged in an elastomer matrix. They are made from a combination of rubber polymer resin and ferrite powder by forming it through...
A Neodymium (Nd-Fe-B) magnet is a common rare earth magnet composed of neodymium (Nd), iron (Fe), boron (B), and transition metals. They have superior performance in applications because of their strong...