Silicon carbide (SiC) is an extremely hard chemical compound produced as powder and crystal for use in industrial furnaces. However, natural instances of SiC also occur as moissanite gemstones.
Molybdenum disilicide (MoSi2) and SiC are two key materials used for high-temperature heating elements. Both materials boast the ability to withstand oxidation under aggressive environments without succumbing to corrosion.
SC Type
Silicon carbide (SiC) is an extremely durable ceramic material with superior thermal conductivity and resistance, making it the ideal material to create electric furnace heating elements. SiC furnace elements play a pivotal role in many industrial processes including ceramics, glass production and metal processing applications. They excel in environments featuring high temperatures and aggressive chemicals as they withstand high levels of heat without damage or degradation – however there are different types of SiC furnace elements tailored to various application requirements.
The SC Type features a single spiral configuration designed to maximize SiC material’s thermal efficiency and durability, making this element particularly suitable for applications requiring uniform heating over large surfaces such as large box and trolley furnaces used in metal processing or ceramic production. Furthermore, its ability to withstand high temperatures makes this element an excellent choice for use in metallurgical processes, where harsh petrochemical environments could potentially expose it.
The element is equipped with a protective film designed to improve anti-oxidant performance and extend service life, produced using special technology that produces lower resistance rates at its cold end, saving energy while avoiding over-temperature in the furnace body. Furthermore, an aluminum braid prevents electrical arcing while making connections easy between power source and element.
H Type
H-Type silicon carbide heating elements are non-metallic high temperature electric heaters which offer exceptional oxidation resistance and thermal shock strength, making them ideally suited to applications that require uniform heat distribution over large areas, such as box furnaces. Their unique construction also enables rapid temperature fluctuations, making this an excellent solution for applications which need precise temperature regulation.
These elements are cylindrical in form, ranging in diameter from 0.5 to 3 inches and lengths up to 10 feet in diameter. They feature two helical slots at either end for electrical connections; their ends meet short of each other to form an approximation of twisted hairpin shapes; connected via aluminum braid that is resistant to high temperature oxidation, they come equipped with clips and clamps to fasten securely to power supplies and thyristors.
When employing a fixed current limit, the element’s minimum resistance must be near to its operating point (point A in Figure 5), but may not always correspond with its maximum transformer or supply voltage rating; this could result in operating at higher power factors than intended, leading to overshoot when reaching setpoint.
W Type
W-shaped elements differ from SC and H types by being constructed of one silicon carbide rod joined to three high-purity silicon carbide rods at one end, creating a W shape. This design provides efficient energy use with even heating over large surface areas – ideal for industrial applications that demand spatial temperature uniformity.
W-shaped silicon carbide heating elements can also be used to manage and sustain thermal conditions in various industrial furnaces, including metal heat treatment furnaces and ceramic and glass manufacturing furnaces. Their more durable design helps them withstand chemical corrosion and environmental stresses more effectively.
TOPE INTL’s W-shaped silicon carbide heating element can be integrated with various electrical systems and can withstand both high voltage currents and extreme temperatures. Connected to its power source using aluminum braid, this element boasts superior flexibility and resistance to oxidation at higher temperatures; furthermore, maintenance and replacement tasks are simple for easy long-term service life for silicon carbide heating elements like this W-shaped one from TOPE INTL.
Non-metallic heating elements are widely utilized in electric furnaces and high temperature equipment used in industries like powder metallurgy, ceramics, refractories, and metallurgical machinery. Furthermore, this heating element type can also be utilized in processes requiring operation under reduced or other process atmospheres.
MoSi2
MoSi2 is becoming an increasingly popular material choice in the heating industry due to its recyclable properties, making it ideal for applications requiring high thermal properties and corrosion resistance as well as its lower cost than SiC. Furthermore, its thermal shock resistance compares favorably with that of ceramics.
MoSi2 can be combined with glass or silica-bearing oxide phases in order to combat low-temperature oxidation, as seen with conventional SiC elements, in order to create composite materials with network structures. To do this, as much silica-bearing oxide or glass phase as possible should remain at MoSi2 grain boundaries so as to limit “pest” oxidation; an ideal volume fraction between 20-55% should ensure effective protection.
MoSi2/SiC composites are then infiltrated into a graphite crucible at 1900degC in an argon atmosphere and rapidly cooled during a rapid cooling cycle, followed by rapid infiltrator cooling cycles to achieve highly porous ceramic with exceptional physical (bulk density, apparent porosity), mechanical (modulus of rupture by three-point bending and tensile stress), oxidation resistance properties and temperature capability for up to 1800degC operations in both reducing and oxidizing atmospheres. This MoSi2 can operate in multiple furnace atmospheres simultaneously at temperatures of 1800degC with good performance on all fronts!
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