Silicon carbide elements are key components in high-temperature electric furnaces and play an essential role in multiple industries including metallurgy, glassware production, ceramics production and electronics.
Silicon carbide heating elements come in various varieties to meet specific industrial requirements. This article delves into their key attributes that help you select an element suited to your application needs.
Motståndskraft mot höga temperaturer
Silicon carbide (SiC) is an extremely hard crystalline compound of silicon and carbon with unparalleled wear-resistance, and has traditionally been used for cutting tools, sandpaper, pumps, rocket engines and semiconducting substrates for light emitting diodes (LEDs). Furthermore, ceramic plates in bulletproof vests feature this material.
Silicon carbide’s durability, combined with its superior thermal conductivity and corrosion-resistance makes it a popular choice for industrial furnace heating elements. Silicon carbide elements can provide uniform heating across large furnaces in demanding environments where operating at higher temperatures is crucial.
These elements typically take the shape of cylinders, tubes or bars and are constructed by fusing high-purity silicon carbide grains at temperatures exceeding 2150oC to create hot zones with cold ends infused with silicon metal to lower its temperature for use at lower operating temperatures.
Eurotherm’s IFC-GD and Alpha Rod elements come in various lengths, diameters, and resistance levels to meet various applications. Their simple design also facilitates easy installation and connection to power supplies; with power connections made at the base of each element away from any potentially reactive hot zones and thus eliminating risks related to exposed graphite being exposed at power connections.
Low Corrosion Resistance
Silicon carbide is an extremely resilient ceramic substance, highly resistant to corrosion and environmental stresses. Unfortunately, however, its durability cannot last indefinitely; corrosion occurs from surface flaw formation causing strength loss as well as increasing fracture probabilities under mechanical or thermal stresses.
SiC’s corrosion resistance depends on numerous factors, including its presence of oxides, the composition and concentration of its solution and temperature of exposure. SiC typically exhibits lower corrosion resistance at higher temperatures or in less oxidizing environments due to slow diffusion of oxygen through its surface oxide layer that limits its rate of oxidation progression.
Silicon carbide’s tetrahedral arrangement of Si and C atoms renders it insoluble in water, alcohol and acidic solutions – making it an ideal material to use in kilns, furnaces and other industrial equipment subject to high temperatures and pressures.
High Resistance to Electrical Currents
SiC is an electrical current-resistant refractory material with many furnace applications. Compared with conventional refractory metals, silicon carbide offers greater temperature flexibility for use in large box and trolley furnaces used in industrial processes.
Manufacturing moissanite involves using the Lely process, in which SiC powder is sublimed into high-temperature species of silicon and carbon under an argon gas atmosphere at 2,500degC before being deposited onto a substrate at slightly lower temperatures for deposition into single crystal hexagonal solids with hexagonal crystal structures – and later cut into gemstones for use as moissanite.
Resistance of silicon carbide elements varies with temperature and time, rising as they reach working temperature before gradually declining over their service lives. Therefore, multiple elements must be connected in parallel in order to attain an optimum power-to-resistance ratio; this requires constant monitoring in order to keep all elements aligned correctly.
The applicants have devised an innovative way of mitigating this problem by employing nitrogen as a dopant during silicon carbide production, which serves to promote (3-silicon carbide formation with lower electrical resistivity than its a-silicon counterpart. By taking advantage of this effect, heating elements with resistance curves that fall to the right of supply voltage/transformer voltage curve (at point A in Figure 6) may dissipate maximum permitted power over their entire lifespan.
Long-Term Reliability
Silicon carbide elements are designed to perform reliably over the long haul in even extreme conditions, thanks to their resistance to chemical corrosion and their longevity properties. Their long lifespan makes them popular choices in aerospace and defense equipment including satellites and missiles where reliable operation is crucial. Silicon carbide materials also withstand high temperatures and radiation exposure without suffering damage, prolonging equipment longevity further still.
Silicon carbide heating elements depend on their operating environment for long-term reliability; process vapors in particular can chemically attack elements or condense on them at their cold ends, restricting flow and leading to breakage. To extend their longevity, a well-designed extraction system should be installed which extracts these volatile vapors before they reach these critical points in the chamber and cause damage.
Eurotherm’s silicon carbide heating elements are tailored specifically for industrial needs, with SC, W, DM, and SCR types all offering solutions to various industrial tasks. For instance, SC Type is ideal for applications that require uniform heating across large areas while minimizing temperature variance; while WG and DM types offer superior resistance against sudden temperature changes while offering superior resistance against thermal shock and stability; finally SCR Type allows advanced thermal management for high-end applications like aerospace while GC Type offers reliable performance for continuous high temperature operations such as in metallurgy or glass production environments.
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