How to distinguish nichrome wire from steel. How to identify nichrome wire at home

Nichrome is one of seven groups of precision (with specified properties) alloys, whose production is regulated by GOST 10994-74. This group includes 16 grades of metals with high current resistance, of which ten are used for the production of heaters and six for sensors and resistors with constant resistance in a given temperature range.

According to the mentioned regulatory document, the definition of nichrome includes the following alloy characteristics:

• maximum operating heating temperature – up to 1,100, 1,150, 1,200, 1,220 and 1,400 °C;
• resistivity – from 0.99–1.07 to 1.37–1.47 units;
• the basic elements of the chemical composition are nickel and/or chromium with a mass fraction of 55–78 and 15–23%, respectively.

On the Internet you can often come across the question of how to determine nichrome at home.
Let us say right away that it is impossible to do this by the appearance of the metal. To identify nichrome wire, you need to know the basic properties of these alloys. First of all, these substances are non-magnetic. If the permanent magnet does not attract the wire, you may have nichrome. This reservation is due to the fact that it is not the only non-magnetic alloy. If a current is passed through a nichrome wire, it will quickly heat up to a characteristic red glow, releasing strong thermal radiation.

A more accurate answer, including determining the grade of the alloy, can only be obtained using laboratory equipment. For this reason, the full characteristics of nichrome products must be indicated in the accompanying documentation, including their labeling and purpose.

How much does nichrome cost in Belarus?

Ready-made spirals UD regular ( nichrome

) 0.5 Ohm (10 pcs.) 10 rub.
Ready-made UD conventional spirals ( nichrome
) 0.5 Ohm (10 pcs.) 9 rub.

Interesting materials:

How does the wireless buttonhole microphone work? How does a wireless lavalier microphone work? How does Liquidless Barometer work? How does a bio toilet work on a train? How does boiler heating work? How does a magnetic field sensor work? How does the shock sensor work? How does the GLONASS fuel level sensor work? How does a diffuser work? How does the display port work?

Nichrome from a soldering iron

Disassemble the soldering iron and find the same nichrome wire. We actually found one, but it was very thin. You can find out the cross-section of the wire by winding 10 turns of thread tightly pressed together around a pencil. Our turns took 1 mm.

This means that the cross-section of our thread is 0.1 mm. You can buy a lot of such cheap soldering irons, but the nichrome spiral in them may differ in length. Disassembling a household soldering iron to obtain nichrome is a really working scheme. But what to do if you don’t have a soldering iron?

A similar spiral is found in hair dryers. Different models have nichrome threads of different diameters, but they are definitely there. Nichrome can be found in a heater built on the principle of a fan. This option will be slightly more expensive than the previous one.

And finally, the most difficult way is to get this metal out of an electric stove with an open spiral. Today we told you that nichrome winding is not such an expensive undertaking. If you decide to find a thread in a soldering iron, then it can reach 2.5 m. This will turn out to be far from 1 winding.

Purchase and selection

They sell finished products with various windings. The thread is made in the form of wire, tape, foil.

To purchase wire, you can place an order at the department for the production of rolled metal products. All you have to do is check your phone number and call. The Internet will provide all available information. Let's consider other options for purchasing wire:

• stores specializing in heating elements;
• shops selling household goods;
• On the market;
• in your house from old electric heating devices.

Nichrome thread has found wide application in medicine. It has the properties of not oxidizing, it is used in plastic surgeries, in surgery for intracavitary actions.

The products are used in pharmacological institutes and research laboratories. When using easel figured cutting, strings are made from nichrome. At home, string devices are made for cutting wooden figures. Houses with platbands, having a beautiful old ornament, are made with such homemade stringed instruments from nichrome threads.

tokar.guru

Distinctive characteristics

Among the most popular electrical products on the market is nichrome wire. The resistivity of this component of electric heating technology is extremely high, which allows it to have a wide demand.

An important feature of the metal is its resistance to high-temperature oxidation under normal and aggressive conditions. Chrome plays a key role here. The element forms a corresponding oxide film on the surface, which performs a protective function. It is also responsible for the corresponding dark color of the material, which is replaced by a characteristic white-gray when the oxidized layer is mechanically removed.

It is worth noting that direct contact with acids still destroys it, even more than corrosion-resistant tungsten.

The two-component alloy has no magnetic characteristics. They arise for its multicomponent modifications, but have weakened indicators.

Nichrome wire is rigid and does not lend itself to simple force.

We systematize information on how to identify nichrome wire, mainly how to distinguish it from externally similar materials:

1. White is the color of new metal, dark is the color of previously worked metal.
2. Negative or minimal magnetism.
3. Rigidity.
4. Destruction by acids, resistance to oxidation under the influence of high temperatures.

History of discovery

The alloy is a combination of nickel and chromium, with variations in the addition of iron, manganese, aluminum, and silicon.

Initially, it had two ways of origin. The roots lie in scientific research regarding the alloying of metals and the modification of their properties. Ni and Cr are components of high-quality corrosion-resistant and heat-resistant steels.

As a two-component alloy of nickel and chromium, it was discovered in 1906 in the USA. Today, its various modifications are used, including three-component ones based on iron.

Technical specifications

When choosing nichrome products, it is important to consider the following features:

• nominal resistivity;
• diameter, section and weight;
• actual resistance and operating temperature limits depending on physical parameters.

The nominal values ​​of the main parametric characteristic are determined by GOST and depend on the brand and composition.

The diameter of the nichrome wire determines its cross-section, the weight of the coil and the corresponding objective resistance.

Thus, the weight of wire (nichrome) per 100 meters of product is directly proportional to its size, and the diameter and cross-sectional area are inversely proportional to the actual resistance.

The operating temperature depends not only on the chemical composition, but also on the parametric characteristics.

The diameter of the wire produced by manufacturers appears to be in the range of 0.05-12 mm, and the tape - 0.15-3.2 mm.

Heat capacity, linear expansion, density and thermal conductivity of nichrome

The table presents the following physical properties of nichrome: specific heat at 25°C, average coefficient of thermal linear expansion in the temperature range from 20 to 1000°C and density of nichrome at 25°C.

It should be noted that the considered grades of nichrome have similar values ​​of physical properties. The density of nichrome is in the range of 8200...8660 kg/m 3 and increases with increasing nickel content in the alloy. The coefficient of thermal linear expansion of nichrome at 20...1000°C has the value (17...18)·10 -6 deg -1. The specific heat capacity of nichrome, depending on the brand, is 440...460 J/(kg deg).

Specific heat capacity, linear expansion and density of nichrome

The thermal conductivity of nichrome is similar in value to the thermal conductivity of stainless steel. The table shows data on the thermal conductivity of the considered alloys at various temperatures in the range from 0 to 600°C.

The thermal conductivity of nichrome increases when heated. With increasing nickel content in the alloy, its thermal conductivity coefficient increases. For example, an alloy containing 10% Cr and 90% Ni has the highest thermal conductivity of the alloys considered, equal to 17.4 W/(m deg) at 20°C.

Decoding stamps

The properties and purpose of nichrome products are determined by their chemical composition. Let's look at the main ones.

• Х20Н73УМ-VI: chromium – 20%, nickel – 73%, aluminum – 3%, molybdenum – 1.5%, manganese – up to 0.3%, titanium – up to 0.05%, iron – 2%, carbon – up to 0.05%; melted using the vacuum induction method;
• ХН70У-Н: Cr – 27%, Ni – 70%, Al – 3%, Mn – up to 0.3%, Cs – up to 0.03%, Ba – up to 0.1%, Fe – up to 1.5% , C – up to 0.1%; designed for electric heating elements;
• ХН20УС: Cr – 20%, Ni – 20%, Al – 1%, Zn – up to 0.2%, Ca – up to 0.1%, Si – 2.5%, Fe – 50%, C – up to 0, 08% – for heaters of industrial furnaces.

Why nichrome

Most often, the creators of coils are faced with the question, what is better for winding kanthal or nichrome? Both of these materials are widely used for making windings. But when it came to which one was better, the pros were divided on this matter. Each has its pros and cons.

If we collect objective information, we get the following:

1. Nichrome is an alloy of nickel and chromium, with possible small admixtures of other metals. A wire made of such material will be quite soft and flexible. This wire will not turn black quickly.
2. Kanthal is an alloy of iron, aluminum and chromium. If you come across the name fechral, ​​then you should know that we are talking about the same material. Such wire, which does not contain nickel, is springy and does not have such a long service life. This material is cheaper than nichrome.

So how do you choose which one is better?

Nichrome heaters (NiСг)

“Nichromes” (Ni-Cr and Ni-Cr-Fe alloys) are used both in industry and in household appliances.

“Nichromes” are characterized by: excellent mechanical properties in the “cold” and “hot” states, as well as after long-term use, therefore they do not require winding on a ceramic tube; high homogeneity of the alloy structure. The maximum operating temperature for nichrome (in particular the best alloy X20N80) is 1200 °C.

A word of caution if you are using nichrome heaters:

• in sulfur-containing atmospheres at temperatures above 650 °C, the so-called “green rot” effect appears, leading to intense destruction of alloys of this class;
• In an atmosphere containing carbon, in the temperature range of 600-900 °C, intensive destruction of alloys of this class occurs. During operation of nichrome heaters, the surface protective film peels off, forming scale, which leads to contamination of heated surfaces and heat-treated parts.

Nichrome retains its plasticity after cooling: the spiral can be removed, the shape adjusted, or bent differently, i.e. it is advisable to use it in cases where winding on a ceramic tube is impossible for some reason, for example, when laying a wound spiral in narrow ceramic grooves. Nickel-chrome alloys can work in contact with any brand of fireclay without interacting with it.

Delivery form:

• in the form of a wire;
• in the form of a tape;
• in bays.

Calculation of a nichrome spiral

Those who very often have to deal with replacing nichrome heating elements and making homemade spirals will pay attention to a somewhat unified approach to the very problem of winding a spiral, when the diameter of the winding rod and the diameter of the nichrome wire are known. To calculate spirals made of nichrome under 220V, we proceed from the calculation that the resistivity of nichrome is equal to - 1.1 x OM x mm²/m. Based on this, you can quickly determine the length of the winding turn to turn, depending on the thickness of the wire and the diameter of the rod used for winding on which you are going to wind your spiral. A table is provided with ready-made spiral winding lengths and the diameters of the rods used for winding the spiral turn to turn.

You just need a little adjustment depending on what you have available.

If you want to calculate a spiral for a different voltage, then this is not difficult to do, for example, you need to determine the length of a spiral for a voltage of 127V from nichrome with a diameter of 0.3 mm, while you have a rod for winding a spiral with a diameter of 4 mm.

From the table it can be seen that the length of the spiral at a voltage of 220V is equal to 22 cm, from this we make a proportion where 220V = 22 cm, and 127V = X cm. Then from here 127V x 22 / 220V = 12.7 cm.

If you want to use the spirals in a closed form, then the winding length of the spiral from that obtained in the table must be increased by 1/3 of the value; this will save you from rapid overheating and failure of the spiral.

Fechral heaters

Fechral heaters (FeCgAl)

“Fechral” (Fe-Cr-Al alloy) is a more advanced material than nichrome, widely used in resistance electric furnaces for all industries (mechanical engineering, foundries and heat treatment shops, ceramics and glass production, drying shops). Fechral heaters are used in electric furnaces up to temperatures of 1400 °C. They are an analogue of material A-1 from KANTHAL.

Advantages of fechral heaters compared to nichrome:

• the price is three times less, which ultimately leads to a reduction in the cost of the furnace;
• longer service life at the same operating temperature as nichrome (depending on operating conditions from two to four times);
• absence of scale, as a result of which the spirals do not need to be closed;
• longer service life in reducing atmospheres;
• higher specific surface power;
• lower density.

The combined effect of all the above factors leads to a significant reduction in the weight of the heater and, ultimately, to a reduction in its cost.

The plasticity of fechral increases with increasing temperature; at temperatures of 800-1000 °C, the alloys are easily deformed under their own weight, so heating elements must be installed on ceramic tubes. When heated to a temperature of 900-950 °C and above, rapid grain growth occurs, leading to irreversible embrittlement of the metal, so repairs of spirals are carried out with great care, without removing the spiral from the furnace.

At temperatures above 1000 °C, fechral can only work in contact with high-alumina refractory materials (with an aluminum oxide content of at least 50%). The performance of fechral is ensured by the protective film of Al2O3 formed on its surface, therefore, when working in non-oxidizing environments, this protective film must be periodically renewed by annealing in an oxidizing environment (in air).

Delivery form for fechral heaters:

• in the form of wire - fechral wire;
• in bays;
• in the form of spirals of various diameters, both on ceramic tubes and without ceramic tubes - fechral spiral;
• in the form of ready-made heating elements, equipped with current leads made of the same material, but of a larger diameter, with ceramic installation insulators and fastening fittings - fechral heaters.

ni-cr.ru

What is the value of nichrome wire?

Nichrome wire has the following valuable qualities:

• high heat resistance: nichrome is used in devices in which an element made of this metal can heat up to a very high temperature;
• not susceptible to corrosion;
• the strength and hardness of nichrome, mechanical stability, however, at the same time it is very elastic;
• high level of electrical resistivity and fairly low temperature coefficient;
• fairly light weight;
• remarkable resistance to a variety of aggressive substances.

Types of products

The choice of any alloy that is characterized by high-quality technological and mechanical characteristics must be justified and regulated. Especially when it comes to high costs. Such a high-tech and expensive material is nichrome wire. GOST 8803-89, 12766.1-90, 12766.3-90, 12766.4-90 defines the requirements, features of marking and application. In accordance with the standards and depending on the type, the metal is presented for sale in the form of wire or strips, the choice of which depends on the diameter, cross-section, length, and features of use.

The corresponding rolled products are the starting material for the industrial production of zigzag tapes and wire spirals.

Where can I get nichrome wire?

There are several options for how and where you can purchase a nichrome product.

Today, in almost every locality there is a help desk for goods and services. By contacting it, you can obtain information from the operator about which organization sells nichrome and its contact numbers. This information can also be found on the Internet. However, in this situation, the chances of purchasing a normal product are practically zero , because if anyone undertakes to deliver the material, it will only be one and a half to two meters. Organizations mainly specialize in wholesale sales. But it’s still worth clarifying.

If such a product is sold in another city, then you can use it. However, this option requires additional payment for shipping. You can purchase wire in specialized stores. These could be “Radio Components”, “Skillful Hands” and other similar pavilions. The sellers of such private stores, who sell various spare parts, know each other very well. Therefore, if such a “private trader” does not have nichrome wire in stock, he can tell you where to purchase it. By the way, you can find it in an ordinary hardware store. Spirals for electric stoves are made of nichrome.

Not a single locality can do without a bazaar where you can buy anything. The most important thing is to carefully go around the entire market and you can even ask the sellers. You may also come across such a product made of nichrome.

find an old device somewhere , for example, a laboratory rheostat. In itself it is of no value, but it has a small amount of nichrome wound on it.

Nichrome wire is a high-quality plastic product due to its remarkable technical characteristics. Buying or getting it in any other way, although difficult, is possible. You just need to take the initiative and try all the above methods.

Source: elektro.guru