Physical and electrical properties of alloys

Grades	Resistivity range	Tensile strength, Н/мм2 MPa, no more	Elongation, %, no less
Cr20Ni80	1,02- 1,14	1000 ( 102)	20

Heating cable (wire) with a current-carrying core made of nichrome and an external insulation shell is widely in demand, both in the industrial and consumer sectors of the market. Flexible insulated heater is used to create heating systems for various technical devices and units, building structures, and also to maintain consistently high temperatures of technological environments and processes.

 Nichrome of the grades Ni80Cr20, Ni80Cr20-N, Ni60Cr15 are used for the production of flexible insulated heaters. Nichrome of these grades is characterized by extreme heat resistance and stability of mechanical properties, both at low and high temperatures up to 950-1380°C, including frequent heating and cooling. The nickel-chromium alloy wire covered by the fiber insulation material has strong plasticity, and the wire can be used repeatedly.

Structurally, a flexible insulated heater consists of two necessary elements: a central current-carrying core and a heat-resistant electrical insulation shell. The thickness of the shell cover depends on the core cross section and the purpose of the cable. The cross-section of the core is regulated by the wire grade.

The shell materials for electrical and thermal insulation of high temperature heating cables made of nichrome have special requirements for the following parameters: heat resistance; linear density; elasticity (resistance to multiple bends); mechanical strength; ability to maintain mold stability without shrinkage at high temperatures; deformation resistance under compression; resistance to high-voltage breakdown voltage. Glass, quartz and silica filament, enamel, and polyvinyl chloride (PVC) are used as insulation materials.

The most widely used are glass filament (single and double), quartz filament (made of quartz fibers) and silica filament (silica). The insulation filaments are tightly and evenly wound in one or more layers directly on the core with a round (nichrome wire) or rectangular (nichrome strip) cross section.

Heat resistance of insulation is a key parameter of the heating wire, since it determines the ability of the wire to perform its functions efficiently and safely for a long time at high heating temperatures of the current-carrying core. Heat resistance of enamel insulation (maximum operating temperature) is 220°C, and for PVC this value is 70°C. Fiberglass insulation is able to work at conductor temperatures up to 600°C, quartz - up to 1200°C, while surpassing other insulating materials in terms of strength and elasticity.

Supply form and specification High temperature electric heating wires in any insulation can be divided into two types according to the shape of the cross-section of the current-carrying core: round and strip. Nichrome wire with a diameter of 0.1 to 2.0 mm is used for round wire. Nichrome strip with a thickness of 0.09 to 0.2 mm and a width of 2 to 16 mm is used for strip wire.