High-temperature industrial furnaces are widely used in metallurgy, heat treatment, glass processing and other industries, with a working environment often exceeding 800℃, which puts forward extremely high requirements for the high-temperature resistance, stability and durability of heating elements. Cartridge heaters used in high-temperature industrial furnaces must be strictly selected in terms of material, structure, power and surface load to ensure long-term stable operation under extreme high-temperature conditions.
The first key selection criterion is the sheath material. Ordinary 304 stainless steel sheath can only withstand a maximum temperature of 500℃, which is far from meeting the needs of high-temperature industrial furnaces. Incoloy 800, 840 high-temperature alloy and 310S stainless steel are the ideal sheath materials for high-temperature cartridge heaters. These materials have excellent high-temperature oxidation resistance and creep resistance, can maintain structural integrity at 900-1100℃, and are not easy to soften, deform or oxidize and peel off. For ultra-high temperature industrial furnaces above 1000℃, Incoloy 840 alloy sheath is the first choice, which has stronger thermal stability and can resist the corrosion of high-temperature gas and dust in the furnace.
The second selection criterion is the internal insulation material. Ordinary magnesium oxide powder will crystallize and age at high temperatures, leading to a decline in insulation performance and even short circuit faults. High-temperature cartridge heaters must use high-purity fused magnesium oxide powder with high temperature resistance, which has good thermal conductivity and insulation performance at ultra-high temperatures, and can maintain stable physical and chemical properties for a long time. The compactness of the filling is also crucial, and high-pressure compaction process is adopted to eliminate internal gaps, avoid air oxidation of the heating wire and improve thermal conductivity.
The third selection criterion is power and surface load matching. High-temperature industrial furnaces have large heat dissipation, and the power of cartridge heaters needs to be reasonably configured according to the furnace volume, heat preservation effect and target temperature. Excessive power will lead to excessive surface load, causing the heating wire to burn out quickly; too low power cannot reach the set temperature. Generally, the surface load of high-temperature cartridge heaters is controlled at 15-25W/cm², and for closed furnace environments with poor heat dissipation, the surface load should be reduced to 10-15W/cm² to prevent local overheating.
The fourth selection criterion is structural design. Cartridge heaters for high-temperature industrial furnaces should adopt a fully sealed structure to prevent high-temperature gas and dust in the furnace from entering the interior and damaging the insulation layer. The lead wires need to use high-temperature resistant ceramic or metal armored wires, which can withstand high temperatures above 800℃ without aging and cracking. In addition, the installation method should be reasonable, usually embedded in the furnace wall or fixed with a bracket to avoid direct contact with high-temperature flame and ensure uniform heating.
In addition, the heating wire material is also a key factor. High-temperature nickel-chromium alloy or iron-chromium-aluminum alloy heating wire with high melting point and stable resistance value should be selected to avoid resistance drift and power attenuation at high temperatures. Before leaving the factory, high-temperature cartridge heaters need to undergo high-temperature aging test to simulate the actual working environment and eliminate early failure products. Strictly following these selection criteria can ensure that cartridge heaters operate safely and stably in high-temperature industrial furnaces, reduce the frequency of replacement and maintenance, and ensure the normal progress of industrial production.
