Nichrome wire: characteristics and applications

Modern technology puts serious requirements on the indicators of compliance of its composite materials with real working conditions. One of the high-tech alloys is nichrome. The wire and devices containing it are resistant to aggressive operating circumstances.

Discovery story

The alloy is a compound of nickel with 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 United States. Today its various modifications are applied, including three-component ones based on iron.

Basic properties

The material for modern heating equipment for domestic and industrial use is, of course, nichrome wire. Its properties correspond to the highest technological requirements.

1. Electrical resistivity: within 1100-1400 Ohm * m.
2. The melting point is about 1400 ° C, which allows it to function at 800-1100 ° C. The maximum permissible value for operation depends on the composition. So, the iron content reduces it to 850-900 ° C, for a pure two-component it is 1100 ° C.
3. Density: 8000-8500 kg / m ³ .
4. High strength (σ _in = 650-700 MPa); indicators remain in the conditions of acidic aggressive environment and significant temperatures.
5. Good ductility together with exponential hardness allows rolling and drawing.

Distinctive features

Among the most demanded electrical products on the market is nichrome wire. The resistivity of this component of electric heating equipment is exceptionally high, which makes it possible to have 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. She is also responsible for the corresponding dark color of the material, which is replaced by a characteristic white-gray during mechanical removal of the oxidized layer.

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

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

Nichrome wire is stiff, does not succumb to simple force influence.

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

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

Brand Nomenclature

Existing brands differ in composition, represent an assortment of nichrome alloy. The wire has widespread use, which is determined by the individual properties of each.

• Group 1 - resistor material: X20H80, X20H73YUM-VI, N80HYUD-VI, X15H60.
• Group 2 - metal for heating elements for domestic and industrial use with high heat resistance characteristics: Kh20N80-N-VI, Kh15N60-N, KhN70Yu-N, Kh20N80-N, KhN20YUS.
• Group 3 - for operation at temperatures up to 900˚: 5010, 2520.

In this case, the diameter of the nichrome wire of the first group is 0.009-0.4 mm, and for the second - 0.2-7.5 mm.

"Kindred" are cantals or fechral alloys of chromium, aluminum and iron. They are also characterized by high electrical resistance, resistance to heat in the range of 1250-1400 ° C, but lower reliability, although low cost (X23U5, X13U4, X23U5T, X27U5T, X15U5).

Decoding marks

The properties and purpose of nichrome products are determined by its chemical composition. Consider the main ones.

• X20N73YUM-VI: chromium - 20%, nickel - 73%, aluminum - 3%, molybdenum - 1.5%, manganese - up to 0.3%, titanium - up to 0.05%, iron - 2%, carbon - up 0.05%; smelted using the vacuum induction method;
• 70-: 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;
• 20: 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.

Types of products

The choice of any alloy, which is characterized by high-quality technological and mechanical characteristics, must be justified and regulated. Especially when it comes to high cost. 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 commercially available in the form of wire or ribbons, the choice of which depends on the diameter, cross-section, length, features of use.

Corresponding hire is the starting point for the industrial manufacture of ribbon zigzags, wire spirals.

Technical specifications

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

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

The nominal values ​​of the main parametric characteristics 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 the wire (nichrome) per 100 meters of production 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 manufactured by manufacturers is represented in the range of 0.05-12 mm, and the tape - 0.15-3.2 mm.

Application

Quality always justifies the cost. The same goes for nichrome alloy. Wire and tapes made of this material are widely used in areas where any other metals could not replace them. High electrical resistance, oxidation resistance, high-quality mechanical characteristics, including for aggressive environments, high-temperature working conditions - all this allows its use in various fields.

In industry:

• Thermocouples of metallurgical electric heating furnaces.
• Structural elements for induction smelting equipment.
• Industrial ventilation dryers.
• Details of boilers and heat exchangers.
• Electrical Engineering: Resistors and Rheostats.
• Some electrodes for welding.
• Single and multicore electric wires.

It is the main structural element for all modern household appliances:

• TENY in electric kettles, boilers, boilers, heaters.
• Heating elements in hair dryers, curling irons, irons.
• Car candles and heating systems.
• E-Sigs.

Perhaps the price is the only drawback of nichrome material. A two-component nickel-chromium wire will be more expensive. The iron content and a decrease in the amount of nickel, in turn, regulate a lower cost, but do not provide the capabilities that X20H80. The choice depends on your technical needs.

When choosing products from nichrome, it is important to operate with information on the chemical composition of the brand of interest, its electrical conductivity and resistance, physical characteristics of diameter, cross-section, and length. It is important to be interested in documentation of compliance, as well as to be able to visually distinguish the alloy from its "competitors". Properly selected material is the key to the reliability of equipment and the technology of its use.