Is steel magnetic?

Characteristics and magnetic properties of cast iron

Cast iron is a combination of carbon (C) and iron (Fe), which has a number of characteristics and certain similarities to steel. Steel also contains carbon and iron. When analyzing the characteristics of metal as a chemical element, it is worth paying attention to whether cast iron is magnetic or not? What influences its characteristics and what do they depend on?

General information

It is an alloy of iron and carbon, which must contain at least 2% in the alloy. Has several varieties:

Cast iron

By its nature, iron is a very soft but strong material; in order to cope with its softness and give strength, carbon is added to the alloy. Malleable cast iron - this name does not mean that the metal can be forged, but indicates its ductility.

White cast iron is white when broken. It is heavy, durable and not susceptible to wet corrosion. It has several varieties and is used for the manufacture of malleable materials.

Gray cast iron contains impurities; this epithet refers to an alloy of iron, carbon and silicon. Most of the carbon in the master alloy is in the form of graphite. At the break it is gray in color.

It is worth paying attention to high-strength cast iron, which contains spheroidal graphite. It does not weaken the metal mesh as much and is not considered a stress raiser.

In terms of production volumes, Russia is one of the top three, second only to China and Japan.

Carbon in the alloy is contained in the form:

Graphite is a mineral in the form of nuggets, considered a modification of carbon. You can see this element if you have a pencil in the house, where the graphite is in the form of a rod. Graphite has been known for a long time, its use depends on the industry: it is relatively soft, in ancient times it was used in the manufacture of clay dishes. In an alloy with iron, it is a source of carbon, and changes with increasing temperature, becoming harder but more brittle.

In chemistry, a carbon atom that has a bond with three other atoms. When added to iron, it affects its properties, increasing the hardness of the alloy.

Cast iron frying pans

Cementite, or iron cardite, is brittle, ductile and weakly magnetic. Formed in a material that contains iron even with a small amount of carbon. It is considered a phase and structural component of the alloy.

As a percentage, it does not exceed 2.14%. The melting point is from 1150 to 1200 °C, 300 °C lower than that of iron.

It is worth noting that cast iron is susceptible to dry corrosion. Compared to steel, it may seem that it has a certain advantage in anti-corrosion properties, but this is not the case. Steel and cast iron are equally susceptible to corrosion.

Main characteristics

The properties of cast iron can be classified according to the following points:

1. Chemical.
2. Thermal.
3. Technological.
4. Hydrodynamic.

The chemical characteristics of the metal are its tendency to corrode. It depends on the composition of the alloy and the elements that are included in it, as well as on environmental factors. Elements in the composition of the alloy can either reduce the susceptibility of the metal to corrosion or increase it, it all depends on their effect on the structure of the metal.

The thermal conductivity of iron decreases due to an increase in impurities in its composition. The thermal conductivity of the alloy changes due to the degree of its graphitization.

Fluidity is classified as a technological property; its degree is determined in various ways. This property increases with decreasing viscosity.

The viscosity of the metal decreases with an increase in the content of manganese in the composition, as well as with a decrease in the amount of sulfur and other non-metallic inclusions in the alloy. Viscosity also depends on temperature. It is proportional to the absolute temperature and the experience of contact with it.

There are also magnetic properties of cast iron, which mainly depend on the structure of the metal. They are divided into primary and secondary.

Primary characteristics include:

• magnetic transformation temperature;
• saturation;
• induction;
• permeability in strong fields.

These characteristics do not depend on the shape and distribution, but depend on the number and properties of the phenomenal phases.

Secondary characteristics include:

• permeability in weak and medium fields;
• coercive force;
• induction;
• saturation;
• residual magnetism.

Secondary properties are determined mainly by the shape and distribution of structural components.

There is paramagnetic or non-magnetic cast iron. This is a material that is used when it is necessary to reduce the magnetic properties of a metal, and it is not possible to replace it with an alloy of non-ferrous metals.

More often than others, carbon and iron are diluted:

1. Nickel.
2. Manganese.
3. Copper and aluminum.

Soft magnetic material has magnetic properties. Ferrite and cementite are responsible for them. The magnetic characteristics of the metal and the degree of their expression depend on the amount of cementite. The same amount of graphite in an alloy can determine its different metallic properties. Thus, not all types of cast iron have magnetic properties, but only malleable and high-strength ones.

But gray cast iron with the same matrix does not have similar properties. Therefore, it is classified as a paramagnetic material.

A reduction in the amount of perlite, which is often used in metallurgy in the manufacture of parts, also affects the material in a similar way. Tempering after hardening can improve the magnetic components of the metal.

A metal may or may not have magnetic properties, and the reason is not carbon. Iron is magnetic, and all alloys that contain this element have similar characteristics. But we should not forget that the alloy is influenced not only by iron, but also by carbon, as well as other elements: nickel, copper, manganese, etc. Due to its properties, the material has various applications.

Thus, cast iron is either magnetic or not, it all depends on the alloy, as well as on the presence of cementite in its composition.

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Source: https://DedPodaril.com/lityo/chugun-magnititsya-ili-net.html

What metals are not magnetic and why?

Any child knows that metals are attracted to magnets. After all, they have more than once hung magnets on the metal door of the refrigerator or letters with magnets on a special board. However, if you put a spoon against a magnet, there will be no attraction. But the spoon is also metal, so why does this happen? So, let's find out which metals are not magnetic.

Scientific point of view

To determine which metals are not magnetic, you need to find out how all metals in general can relate to magnets and a magnetic field. With respect to the applied magnetic field, all substances are divided into diamagnetic, paramagnetic and ferromagnetic.

Each atom consists of a positively charged nucleus and negatively charged electrons. They move continuously, which creates a magnetic field. The magnetic fields of electrons in one atom can enhance or cancel each other, depending on the direction of their movement. Moreover, the following can be compensated:

• Magnetic moments caused by the movement of electrons relative to the nucleus are orbital.
• Magnetic moments caused by the rotation of electrons around their axis are spin moments.

If all magnetic moments are equal to zero, the substance is classified as diamagnetic. If only spin moments are compensated - to paramagnets. If the fields are not compensated, use ferromagnets.

Paramagnets and ferromagnets

Let's consider the option when each atom of a substance has its own magnetic field. These fields are multidirectional and compensate each other. If you place a magnet next to such a substance, the fields will be oriented in one direction. The substance will have a magnetic field, a positive and a negative pole.

Then the substance will be attracted to the magnet and can itself become magnetized, that is, it will attract other metal objects. For example, you can magnetize steel clips at home. Each one will have a negative and a positive pole, and you can even hang a whole chain of paper clips on a magnet.

Such substances are called paramagnetic.

Ferromagnets are a small group of substances that are attracted to magnets and are easily magnetized even in a weak field.

Diamagnets

In diamagnetic materials, the magnetic fields inside each atom are compensated. In this case, when a substance is introduced into a magnetic field, the movement of electrons under the influence of the field will be added to the natural movement of electrons. This movement of electrons will cause an additional current, the magnetic field of which will be directed against the external field. Therefore, the diamagnetic material will be weakly repelled from the nearby magnet.

So, if we approach the question from a scientific point of view, which metals are not magnetic, the answer will be – diamagnetic.

Distribution of paramagnets and diamagnets in the periodic table of Mendeleev elements

The magnetic properties of simple substances change periodically with increasing atomic number of the element.

Substances that are not attracted to magnets (diamagnets) are located mainly in short periods - 1, 2, 3. Which metals are not magnetic? These are lithium and beryllium, and sodium, magnesium and aluminum are already classified as paramagnetic.

Substances that are attracted to magnets (paramagnets) are located mainly in the long periods of the Mendeleev periodic system - 4, 5, 6, 7.

However, the last 8 elements in each long period are also diamagnetic.

In addition, three elements are distinguished - carbon, oxygen and tin, the magnetic properties of which are different for different allotropic modifications.

In addition, there are 25 more chemical elements whose magnetic properties could not be established due to their radioactivity and rapid decay or the complexity of synthesis.

The magnetic properties of lanthanides and actinides (all of which are metals) change irregularly. Among them there are para- and diamagnetic materials.

There are special magnetically ordered substances - chromium, manganese, iron, cobalt, nickel, the properties of which change irregularly.

What metals are not magnetic: list

There are only 9 ferromagnets, that is, metals that are highly magnetic, in nature. These are iron, cobalt, nickel, their alloys and compounds, as well as six lanthanide metals: gadolinium, terbium, dysprosium, holmium, erbium and thulium.

Metals that are attracted only to very strong magnets (paramagnetic): aluminum, copper, platinum, uranium.

Since in everyday life there are no such large magnets that would attract a paramagnetic material, and also no lanthanide metals are found, we can safely say that all metals except iron, cobalt, nickel and their alloys will not be attracted to magnets.

So, what metals are not magnetic to a magnet:

• paramagnetic materials: aluminum, platinum, chromium, magnesium, tungsten;
• diamagnetic materials: copper, gold, silver, zinc, mercury, cadmium, zirconium.

In general, we can say that ferrous metals are attracted to a magnet, non-ferrous metals are not.

If we talk about alloys, then iron alloys are magnetic. These primarily include steel and cast iron. Precious coins can also be attracted to a magnet, since they are not made of pure non-ferrous metal, but of an alloy that may contain a small amount of ferromagnetic material. But jewelry made of pure non-ferrous metal will not be attracted to a magnet.

What metals do not rust and are not magnetic? These are ordinary food grade stainless steel, gold and silver items.

Source: https://FB.ru/article/435941/kakie-metallyi-ne-magnityatsya-i-pochemu

How to distinguish stainless steel from other metals

How to distinguish one steel grade from another if, for example, AISI 304 and AISI 303 sheets were stored together? A number of simple, inexpensive and non-damaging tests can help solve this problem. It should be noted right away that such tests have a number of serious limitations.

For example, such tests will not help determine which of two sheets of steel of the same grade has been heat treated and which has not. Additionally, there is no easy way to distinguish certain grades of steel from each other. For example, it is impossible to distinguish steel AISI 304 (08Х18Н10) from AISI 316L (03Х17Н14М3), or 304 (08Х18Н10) from 304L (03Х18Н11).

A molybdenum content test will help determine whether molybdenum is present in steel, but without additional information the grade of steel cannot be correctly determined. For example, AISI 316 (10Х17Н13М2) steel, based solely on the results of this test, can be defined as 316L (03Х17Н14М3), 2205 or 904L.

Often, only with the help of more complex tests, in which the metal is exposed to chemical reagents, strength or heat resistance is checked, can the grade of steel be reliably determined. If simple tests do not help, then a full spectral or chemical analysis in the laboratory cannot be avoided.

Reaction to magnet

This test will help determine that austenitic steels (for example, AISI 300 series) do not react to a magnet when approaching it. Other stainless steels, such as ferritic, martensitic and duplex, react to magnets. When performing this test, it should be remembered that some austenitic steels, for example, 304 (08Х18Н10), can be attracted by a magnet if they were produced by cold rolling.

Reaction to nitric acid

Helps differentiate carbon steel from stainless steel. First, you need to place a steel sample in a solution of nitric acid (from 20-50%) at room temperature, or drop the solution onto a clean steel surface. A reaction will begin on the surface of the carbon steel, releasing caustic brown vapor. This reaction does not occur with stainless steel. When working with nitric acid, you must be extremely careful, and you should not inhale the vapors released during the reaction.

Molybdenum content test

Helps determine whether steel contains molybdenum. Steel containing sufficiently molybdenum, for testing as follows: 316 (10x17n13M2), 316L (03x17N14M3), 444, 904L, 2205, all "super -duplicate" alloys (S32760, Zeron 100, S32750, 2507, S32550, S32520, UR52N+). The test can also determine molybdenum in other steels containing approximately 2% Mo.

When conducting a test, it is best to compare an unknown steel with a control sample, for example, AISI 304 (08Х18Н10) and AISI 316 (10Х17Н13М2) steels. For the test you will need an acid-based reagent (you can use either the American “Decapoli 304/316” or “Moly Drop 960”, or domestic analogues, although they are quite difficult to find).

First, it is necessary to prepare the surface of the test sample by cleaning it with sandpaper. Then drop the reagent onto the surface of the steel to be determined and onto the control sample. Dark yellow spots appearing after 2-4 minutes indicate the presence of molybdenum. When carrying out the test, do not forget that its reliability may be affected by the temperature of the samples.

For example, some steels containing about 0.5% molybdenum in impurities may react positively to the test at low temperatures. During the test, you should be careful when working with the reagent and follow the requirements for safe work with acids.

Sulfur content test

Sulfur is a harmful impurity that causes brittleness of steel during hot forming. This test helps determine the level of sulfur in steel. For this test, control samples of AISI CS1020, S1214, 304 or 303 steels will be needed, comparison with which will help in determining the degree of sulfur content. To carry out the test, it is necessary to clean the surface of the test sample using sandpaper, and control samples should be prepared in the same way.

Next, you should soak the photographic paper in a 3% sulfuric acid solution for 3 minutes, apply the photographic paper face to the surface of the test sample, hold for 5 seconds and compare the results of the tested steel and the control samples. A dark brown stain indicates high sulfur content. When testing, it should be taken into account that the reliability of the result is seriously influenced by the density and duration of contact of the paper with the surface.

When performing this test, also remember to be careful when working with acid.

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Source: http://ooo-asteko.ru/kak-otlichit-nerzhaveyku-ot-drugih-metallov/

How effective are magnetic pressure bracelets: mechanism of action and rules of use, types and materials of manufacture, customer reviews

Hypertension is one of the most common problems. There are different ways to get rid of high blood pressure. Among them, magnetic bracelets are gaining more and more popularity.

These devices will help normalize blood pressure, maintain it at the desired level, eliminate headaches and relieve weather dependence.

A pressure bracelet will not only help you feel better, but will also look beautiful and stylish on your hand.

Today, magnetic bracelets are increasingly used to treat hypertension.

Mechanism of action of the bracelet

All properties of the device are contained in its main operating element - a magnet. The accessory creates a magnetic field, which affects the human body. The technique of treatment with these devices is called magnetotherapy.

It is based on the opinion that malfunctions of organs arise as a result of negative shifts in the human magnetic field. These disorders are caused by adverse environmental influences.

Experts assure that with the help of these accessories you can:

• protect yourself from the adverse effects of the environment;
• tone the body and give it strength and energy;
• get rid of insomnia;
• increase the body's resistance to viruses and bacteria;

Magnetic therapy involves treating the body by exposing it to magnetic fields.

• improve blood circulation in organs and tissues;
• normalize blood pressure.

A magnetic pressure bracelet will help eliminate all signs of hypertension.

The therapeutic effect on the body of the device is explained by the fact that the magnets that are part of it actively interact with iron concentrated in red blood cells.

As a result of the interaction, the speed of movement of red blood cells (erythrocytes) increases and the delivery of oxygen to all organs and tissues improves. This helps reduce blood viscosity and reduce the load on the cardiovascular system.

Types of bracelets

There are different types of pressure bracelets. Among them, those that enjoy special trust stand out. The choice should be made together with your doctor.

Magnetic bracelet will help cope with insomnia

Neodymium

Such magnets are considered rare earth. They are composed of neodymium alloy, boron ferrite and rare earth metals. They are quite powerful, even the smallest of them can lift 10 kg.

Properties such as the ability to normalize blood circulation, improve oxygen metabolism, and relieve muscle tension are highlighted. If you constantly wear a bracelet, you can eliminate chronic depression and fatigue, and improve the functions of the immune system.

The bracelet also has other properties:

• relieves pain in the joints;
• improves the condition of the thyroid gland;
• treats diseases of the stomach and intestines;
• increases sexual power in men;
• strengthens the reproductive system of women;
• helps overcome addiction to alcohol, drugs and cigarettes.

Zirconium bracelets help cope with skin allergies

Zirconium

Zirconium is a metal that is rarely found in nature. It is distinguished by its silver color with a slight golden tint. Its medical properties were discovered only in the last century.

Due to the fact that the metal has bactericidal properties, it is used for the production of dental implants and medical instruments. Zirconium pressure bracelet began to be used not so long ago.

But this remedy quickly became popular due to its properties not only to treat hypertension, but also:

• relieve dermatological diseases and allergic reactions;
• eliminate certain forms of pathologies of the musculoskeletal system;
• normalize sleep and treat depression;
• eliminate headaches and sexual dysfunction.

Bracelets with silver inserts improve the body's defenses

Your health improves from the first days of wearing the accessory. There is a decrease in blood pressure and the disappearance of feelings of fatigue. This device has an unlimited period of use.

Therefore, it is recommended to wear it even in the absence of health problems to prevent them. These bracelets look elegant, light and wear-resistant. The bracelet can be left on even while taking a bath or sleeping.

He won't cause any inconvenience.

Magnetic

These products are made from different metals. Various inserts can be used. You should purchase such a product only from licensed stores that can provide quality certificates. These accessories are not only suitable for women.

There are also pressure bracelets for men. Magnetic products will speed up the movement of blood through the vessels and normalize pressure in the arteries. Some bracelets even help restore male strength.

Accessories with geranium, titanium, and wicker leather are popular among the stronger sex.

Neodymium magnets increase male potency

You can choose a remedy to suit every taste and budget. There is a new development presented by Japanese manufacturers, which offers the purchase of watches with a magnetic bracelet.

Bracelets with inserts from other metals

Different materials are used to make such accessories. Inserts with useful stones and metals can enhance the therapeutic effect. They improve the general condition of the body. The following inserts can be used in bracelets:

• Germanium. This material has vasodilating properties, saturates the blood with oxygen, strengthens the immune system, and provides the body with antiviral and anticancer protection. It removes toxins from the body and saturates cells with oxygen. Scientists have proven that this metal has a positive effect on concentration, improves blood flow and increases the body's resistance to negative factors.

Tourmaline is a rare mineral with healing effects

• Silver. It improves the functions of the immune system, protects against the negative effects of viruses and bacteria on the body.
• Aeroions. These are negatively charged ions that improve blood circulation and increase blood flow to the brain, which helps increase a person's stamina and performance. The wearer of this accessory does not lose strength and energy even after a hard day at work. Drowsiness and apathy go away as soon as negative ions reach the wrist. They also increase the body's ability to withstand stressful situations. A blood pressure treatment bracelet will be especially useful for those whose work activities involve mental stress. Aeroions help normalize hemoglobin levels, lower blood pressure, relieve allergies, sleep disorders, and cardiovascular diseases.

People with a pacemaker should not wear magnetic bracelets

• Tourmaline. This is one of the rarest gems. It produces positive waves that create a state of calm and tranquility and eliminate sleep disturbances. Wearing such a product helps to normalize metabolic processes in the body, eliminates heart rhythm disturbances, strengthens the myocardium, stabilizes blood circulation, eliminates waste and toxins, slows down aging, and enhances recovery processes.
• Infrared rays. Inserts emitting these rays have a positive effect on hematopoietic processes, eliminate and remove toxic substances from the body, relax muscle spasms, and increase the pain threshold. Although these rays are not visible to the naked eye, they penetrate the body and affect all internal organs. With the help of these waves you can protect yourself from radioactive radiation and strengthen your immune system.

If there are open wounds on the body, it is prohibited to use the bracelet.

• Nano stone. The stone contains several dozen types of elements beneficial to the body. The compound has a positive effect on the immune system, the circulatory system, relieves hypertension, and eliminates the symptoms of osteochondrosis. Radiation from such inserts is an excellent prophylactic against many diseases. Wearing the accessory will eliminate fatigue, headaches, and protect against radiation from electrical appliances. The bracelet is useful not only for people with health problems, but also for everyone else, as it will help prevent the development of disorders.

Typically, inserts are located on the inside of the accessory. These pressure bracelets are suitable for women and men.

The video presents the opinion of doctors on the effect of magnetic bracelets on blood pressure:

Contraindications for use

Despite many positive properties, like all medicinal products, magnetic bracelets have contraindications. You cannot purchase and wear such an accessory in the following cases:

• if you have a pacemaker or other devices in your body;
• if there are open wounds;
• in infectious processes accompanied by acute fever;
• for severe purulent diseases;
• in the presence of pathologies of the circulatory system;
• in acute heart failure;
• in case of individual intolerance to individual components;
• for bleeding disorders;
• during the recovery period after surgical interventions on internal organs;
• during pregnancy and breastfeeding, since the full impact of magnetic radiation on the body of the fetus and newborn has not been fully studied;
• in the presence of cancer.

To get the maximum effect, the bracelet should not be worn constantly, but intermittently.

To get the maximum benefit from the device, women's and men's magnetic pressure bracelets must be worn correctly.

During the treatment process you should adhere to the following recommendations:

• Drink plenty of fluids. At least two liters per day.
• Alternate periods of wearing the bracelet and resting from it.
• Consult a qualified healthcare practitioner before use.

Whether to trust these products or not, everyone decides for themselves. But the effectiveness of bracelets has been tested by many. It is much easier to get rid of troubling ailments with the help of an accessory, rather than using pills for many years. You can purchase the remedy in pharmacies or online stores.

Source: https://dp3.ru/sosudy/naskolko-effektivny-magnitnye-braslety-ot-davleniya-pokazaniya-i-protivopokazaniya-k-primeneniyu.html

Is cast iron magnetic?

Cast iron and steel - two types of iron-carbon compounds - are widely used in a wide variety of industries. But sometimes it becomes necessary to distinguish cast iron from steel, for example, during repairs, because these alloys have different properties and, accordingly, require different handling.

Methods for determining cast iron

You can identify cast iron by the density of the product. Weigh the object and then determine how much water it displaces. This way you will calculate its density and draw a conclusion about the material.

The fact is that the density of the main steel grades lies in the range of 7.7 - 7.9 grams/cm3, while the density of the most common gray cast iron does not exceed 7.2 grams/cm3. But this method is unreliable, since there is also white cast iron, the density of which varies between 7.6 and 7.8 grams/cm3.

Therefore, it can only be used if you are firmly convinced that the product is made of either steel or gray cast iron.

You can use a magnet. It sticks to cast iron worse than to steel. But this method cannot be called accurate, since some types of alloy steels with a high nickel content almost do not attract a magnet.

Therefore, it is more reliable to use one of the following methods: determine cast iron using the type of sawdust or shavings formed, as well as using a grinding machine. Take a finely cut file and run it over the surface of the product several times. Try to collect the tiny sawdust that forms on a sheet of paper. Fold the paper in half and rub vigorously. If it is cast iron, then the paper will be noticeably stained; if it is steel, there will be practically no marks left.

You can also drill the product a little with a thin drill (of course, not from the front side, but in a place that is not obvious). This produces a small amount of chips.

By its appearance and properties, you can accurately determine what material the part is made of. If it is cast iron, the shavings will literally crumble in your fingers, turning into dust.

If it's steel, the shavings will look like a coiled spring and may even scratch your fingers if you try to break them.

Finally, you can judge a material by the size, shape and color of the sparks produced when a sander is passed along the edge of the product. The higher the carbon content, the brighter and stronger the sheaf of light yellow sparks will be. And the carbon content in cast iron is much higher than in steel.

If in doubt, it is better to use pieces of cast iron and steel as standards and compare the shape and properties of sawdust (shavings), as well as the type of sparks produced, with what is obtained when processing these samples.

There is China and China. At IKEA, all the stainless steel is made in China, but the holders of the brand (the Swedes, and now, it seems, the Dutch) tightly control the production. As a result, it seems to me that the price/quality ratio of very unassuming IKEA pots and pans is one of the best on our market. Everything works on an induction panel, if stated.

Most of the world's BRAND electronics are made in China. As for other “household” garbage, I can name some knife manufacturers.

It’s worse when the brand itself is Chinese, but even here there is rapid progress: there are things
(for example, in electronics, in the production of buses) that the Chinese, under state control, have begun to do very well.

But when our business sharks come into play, creating “German” brands and sticking Western-style labels on the products of Chinese unknown and uncontrolled artisans, then hold on.

I heard that during the times of perestroika cooperatives in Odessa, the highest chic was considered not to be counterfeiting sneakers under the branded “Addidas”, but to make them look like a Chinese counterfeit “Addidas”. This style has been preserved by all those who rise from their knees - everywhere. Trash and cattle, robbing their own.

Hospadi! When will this notorious “magnet” disappear from culinary communities? The classic “food-grade stainless steel” - steel “18/10” - is not attracted by any “permanent magnets”, but it is perfectly suitable for induction cookers.

Members

1967 messages

• City: Ukraine
• Name: Sergey Savelievich

How to distinguish cast iron from steel.

Look carefully at the crankshaft; cast iron is cast; steel is usually forged from a whole piece of steel. It can be almost unmistakably determined by its appearance. By the way, what engine does the crankshaft come from? And once again, by the way, the vast majority of crankshafts are cast iron. Obviously casting is cheaper and easier than forging.

#16 Sergey19

Source: https://chistodoma.online/kuhnya/magnititsya-li-chugun.html

Magnetic and non-magnetic materials

February 24, 2015.
Category: Electrical engineering.

In the magnetic circuits of various electrical machines, transformers, instruments and apparatus of electrical engineering, radio engineering and other branches of technology, a variety of magnetic and non-magnetic materials are found.

The magnetic properties of materials are characterized by the values ​​of magnetic field strength, magnetic flux, magnetic induction and magnetic permeability.

The relationship between magnetic induction and magnetic field strength, expressed graphically, forms a curve called a hysteresis loop. Using this curve, you can obtain a series of data characterizing the magnetic properties of the material.

An alternating magnetic field causes the appearance of eddy currents in magnetic materials. These currents heat the cores (magnetic cores), which leads to the consumption of some power.

To characterize a material operating in an alternating magnetic field, the total value of power expended on hysteresis and eddy currents at a frequency of 50 Hz is referred to 1 kg of material weight. This value is called specific losses and is expressed in W/kg.

The magnetic induction of a particular magnetic material should not exceed a certain maximum value, depending on the type and quality of the material. Attempts to increase induction lead to increased energy losses in a given material and its heating.

Magnetic materials are classified as soft magnetic and hard magnetic.

Magnetic soft materials

Soft magnetic materials must meet the following requirements:

1. have a large relative magnetic permeability µ, which makes it possible to obtain a large magnetic induction B with the smallest possible number of ampere-turns;
2. have the lowest possible losses due to hysteresis and eddy currents;
3. have stable magnetic properties.

Soft magnetic materials are used as magnetic cores of electrical machines, transformer cores, chokes, relay electromagnets, electrical measuring instruments, and the like. Let's look at some soft magnetic materials.

Electrical hardware

obtained by electrolysis of sulphide or ferric chloride, followed by melting in vacuum of the electrolysis products. Powdered electrolytic iron is used for the production of magnetic parts, similar to the production of ceramics or plastics.

Carbonyl iron

obtained in the form of a powder as a result of the thermal decomposition of a substance that includes iron, carbon and oxygen [Fe(CO)5].

At a temperature of 1200 °C, carbonyl iron powder is sintered and used to manufacture the same parts that are made from electrolytic iron. Carbonyl iron is characterized by high purity and ductility; used in the electrovacuum industry, as well as in instrument making for the manufacture of laboratory instruments and devices.

The two types of highly pure iron we considered (electrolytic and carbonyl) contain no more than 0.05% impurities.

Electrical steel sheets

is the most common material in electrical engineering and transformer manufacturing. Electrical steel is alloyed with silicon to improve its magnetic properties and reduce hysteresis losses. In addition, as a result of the introduction of silicon into the steel composition, its resistivity increases, which leads to a decrease in eddy current losses.

Sheet thickness depending on the steel grade is 0.3 and 0.5 mm. Electrical steel, cold rolled and then annealed in a hydrogen atmosphere, has particularly high magnetic properties. This is explained by the fact that the metal crystals are located parallel to the rolling direction. This steel is designated by the letters KhVP (cold-rolled high permeability, textured).

Steel sheets have dimensions from 1000 × 700 to 2000 × 1000 mm.

The grades of electrical steel used to be designated, for example, as follows: E3A, E1AB, E4AA. The letter E means electrical steel; letter A – reduced power losses in an alternating magnetic field; letters AA - especially low losses; letter B – increased magnetic induction; numbers 1 – 4 show the amount of silicon contained in steel as a percentage.

According to GOST 802-54, new designations for electrical steel grades have been introduced, for example: E11, E21, E320, E370, E43. Here the letter E stands for electrical steel; first numbers: 1 – lightly doped with silicon; 2 – medium doped with silicon; 3 – highly alloyed with silicon and 4 – highly alloyed with silicon.

The second digits in the designation of grades indicate the following guaranteed magnetic and electrical properties of steels: 1, 2, 3 – specific losses during magnetization reversal of steels at a frequency of 50 Hz and magnetic induction in strong fields; 4 – specific losses during magnetization reversal of steels at a frequency of 400 Hz and magnetic induction in average fields; 5, 6 – magnetic permeability in weak fields (H less than 0.01 A/cm); 7, 8 – magnetic permeability in medium fields (H from 0.1 to 1 A/cm). The third digit 0 indicates that the steel is cold-rolled, textured.

Permalloy

an alloy of iron and nickel. Approximate composition of permalloy: 30–80% nickel, 10–18% iron, the rest copper, molybdenum, manganese, chromium. Permalloy is easily processed and is available in sheet form. It has very high magnetic permeability in weak magnetic fields (up to 200,000 H/cm). Permalloy is used for the manufacture of telephone and radio communication parts, transformer cores, inductors, relays, and parts of electrical measuring instruments.

Alsifer

an alloy of aluminum, silicon and iron. The approximate composition of alsifer is: 9.5% silicon, 5.6% aluminum, the rest is iron. Alsifer is a hard and brittle alloy, so it is difficult to process. The advantages of alsifer are high magnetic permeability in weak magnetic fields (up to 110,000 H/cm), high resistivity (ρ = 0.81 Ohm × mm²/m), and the absence of scarce metals in its composition. Used for the manufacture of cores operating in high-frequency installations.

Permendur

an alloy of iron with cobalt and vanadium (50% cobalt, 1.8% vanadium, the rest iron). Permendur is available in the form of sheets, strips and tapes. It is used for the manufacture of electromagnet cores, dynamic loudspeakers, membranes, telephones, oscilloscopes and the like.

Magnetodielectrics

These are magnetically soft materials, crushed into small grains (powder), which are isolated from one another by resins or other binders. Electrical iron, carbonyl iron, permalloy, alsifer, magnetite (feO Fe2O3 mineral) are used as magnetic material powder.

Insulating binders are: shellac, phenol-formaldehyde resins, polystyrene, liquid glass and others. The magnetic material powder is mixed with an insulating binder, thoroughly mixed, and from the resulting mass the cores of transformers, chokes, and radio equipment parts are pressed under pressure.

The granular structure of magnetodielectric materials causes low losses due to eddy currents when these materials operate in magnetic fields of high-frequency currents.

Hard magnetic materials

Hard magnetic materials are used to make permanent magnets. These materials must meet the following requirements:

1. have a large residual induction;
2. have a high maximum magnetic energy;
3. have stable magnetic properties.

The cheapest material for permanent magnets is carbon steel (0.4 - 1.7% carbon, the rest is iron). Magnets made of carbon steel have low magnetic properties and quickly lose them under the influence of heat, shock and shock.

Alloy steels have better magnetic properties and are used for the manufacture of permanent magnets more often than carbon steel. These steels include chromium, tungsten, cobalt and cobalt-molybdenum.

For the manufacture of permanent magnets, alloys based on iron - nickel - aluminum have been developed in technology. These alloys are characterized by high hardness and brittleness, so they can only be processed by grinding. The alloys have exceptionally high magnetic properties and high magnetic energy per unit volume.

Table 1 shows data on the composition of some hard magnetic materials for the manufacture of permanent magnets.

Table 1

Chemical composition of magnetically hard materials

Name of material	Chemical composition in weight percent	Relative weight per unit magnetic energy
Carbon steel Chromium steel Tungsten steel Cobalt steel Cobalt-molybdenum steel Alni Alnisi AlnicoMagnico	0.45 C rest Fe 2 – 3 Cr; 1 C 5 W; 1 C 5 – 30 Co; 5 – 8 Cr; 1.5 – 5 W 13 – 17 Mo; 10 – 12 Co 12.5 Al; 25 Ni; 5 CH 14 Al; 34 Ni; 1 Si 10 Al; 17 Ni; 12Co; 6 CH24 Co; 13 Si; 8 Al; 3 Dc	26,7 17,2 15,8 5,1 – 12,6 3,8 3,6 3,4 3,11

Non-magnetic materials

In various instruments and devices used in electrical engineering, it is necessary to have a material that does not have magnetic properties. Plastic and non-ferrous metals (aluminum, brass, bronze) are suitable for such purposes. However, these materials have low mechanical strength, and some of them are in short supply. In this regard, they are being replaced by non-magnetic steel and non-magnetic cast iron.

The approximate composition of non-magnetic steel is: 0.25 - 0.35% carbon, 22 - 25% nickel, 2 - 3% chromium, the rest is iron. Non-magnetic steel is used for coupling and fastening of transformers, chokes, inductors and the like.

The approximate composition of non-magnetic cast iron is: 2.6 - 3% carbon, 2.5% silicon, 5.6% manganese, 9 - 12% nickel, the rest is iron.

Non-magnetic cast iron is used for the manufacture of covers, casings, bushings, oil switches, cable couplings, and casings for welding transformers.

Source: https://www.electromechanics.ru/electrical-engineering/633-magnetic-and-non-magnetic-materials.html

Is cast iron magnetic or not: how to determine by the properties of the metal

Cast iron is widely used in the production of a variety of industrial and household products, as well as for the construction of building and architectural structures. The main elements of the alloy composition are iron and carbon (in a concentration of 2%). Cast iron may also contain chromium, nickel, copper, manganese or aluminum. The percentage and type of impurities determines the physical and chemical characteristics of the material. It depends on them whether cast iron is magnetic or does not have such a property.

Varieties of alloy

The introduction of two or more percent carbon into molten iron is used to reduce the increased softness of cast iron and increase its strength. They are produced in large volumes in Russia, Ukraine and most other countries of the world.

Cast iron batteries

There are three types of cast iron:

1. Malleable. It is characterized by high plasticity.
2. Grey. It got its name because of the grayish tint in the fracture area. Contains silicon. Carbon in the alloy is present in the form of the natural mineral graphite, which becomes both hard and brittle when heated. Varieties of gray cast iron include high-strength, containing spherical graphite.
3. White. The fracture site has a whitish tint. Resistant to wet corrosion, characterized by significant weight and high strength. Forged products are made from it. Carbon in the alloy is in the form of cementite. Formed during metal smelting, it is iron cardite. This form of carbon is weakly magnetic.

Magnetic properties

There are primary and secondary ability of cast iron to be magnetic.

The first type is associated with quantitative and qualitative indicators of ferromagnetic phases, in particular, with magnetic induction, the influence of strong magnetic fields on permeability, and temperature indicators at which magnetic transformation occurs.

Secondary magnetic properties are determined by the structure of the metal, its hysteresis characteristics, for example, residual magnetism, permeability in the zone of influence of medium and weak magnetic fields.

Depending on the ability of cast iron to magnetize, the alloy can be:

Ferromagnetic. Contains carbon in the form of graphite. This type of alloy is also called soft magnetic; it includes gray and malleable cast iron, and in high-strength cast iron the ability to be magnetic is most pronounced. Hardening allows you to enhance the magnetic properties of the metal.

Non-magnetic. Another name for this type of alloy is paramagnetic. It is in demand when it is necessary to use metal with low magnetic properties. Parts of oil switches, transformer boxes and other products are made from non-magnetic cast iron if it is necessary to minimize power losses in electrical equipment. And also a paramagnetic alloy is used to prevent magnetic field deformation, for example, in the production of stands for magnets.

Austenitic paramagnetic cast iron may have the following composition:

• chromium, nickel group of alloys (niresist);
• nickel-manganese group containing aluminum and copper in various concentrations (nomag), with minimally pronounced magnetism; less resistant to high temperatures and moisture;
• manganese, has a low cost, contains the same metals as the alloys of the previous group, but is inferior to them in strength and a number of other physical characteristics.

The higher the magnetic properties, the more globular graphite there is in cast iron, the lower the concentration of pearlite, the lower the level of coercive force of the metal, and the larger the size of the ferrite grains. High values ​​of magnetic induction and permeability in high-strength and malleable types of cast iron products determine its ability to be well magnetized.

Source: https://DedAntikvar.com/interesnoe/obladaet-li-chugun-magnitnymi-svojstvami