What Is A High Temperature Element Wire?

High temperature element wire, also known as heating element wire, refers to metallic alloys or non-metallic materials that can withstand extremely high temperatures without melting or deteriorating. These wires are commonly used as resistive heating elements in appliances and industrial processes that involve high heat. Key properties that make these wires suitable for high temperature applications include:

– High melting point – Most high temp wires have melting points above 2000°F or 1100°C. This allows them to be operated at red-hot temperatures continuously.

– High resistivity – Materials like nichrome and kanthal have higher electrical resistance, which allows them to heat up quickly when electric current passes through.

– Oxidation resistance – Elements like silicon carbide and molybdenum disilicide form stable oxide layers that protect the wire from oxidation damage at elevated temperatures.

– Good mechanical strength – The alloys and non-metallic compounds maintain adequate strength and flexibility to allow coiling and shaping of the elements.

Common applications of high temperature element wire include household appliances like toasters, ovens, grills, and deep fryers. They are also widely used in industrial furnaces, kilns, metal heat treating, plastic molding equipment, and semiconductor manufacturing processes that require rapid, precision heating up to 2000°F.

Working Temperature Range

High temperature element wires are designed to withstand high heat for extended periods of time. The maximum continuous operating temperature range is typically between 500-1000°F (260-538°C), depending on the alloy used. For example, nickel-chromium alloys like Nichrome can operate at continuous temperatures up to 1100°F (593°C) while iron-chromium-aluminum alloys can withstand up to 1400°F (760°C) continuously.

These wires can also handle temperatures above the continuous rating for short periods of time, up to around 1500-1700°F (815-927°C). However, repeated cycling above the maximum continuous temperature will degrade the wire over time. It’s important to stay within the continuous rating for most normal operation, using the short-term peak temperature sparingly.

Exceeding the short term temperature limit can lead to immediate failure through melting, evaporation, or oxidation. Careful design and testing is necessary to ensure the wire alloy and insulation is properly rated for the operating environment.

Common Alloy Materials

High temperature element wires are commonly made from nickel-chrome, iron-chrome-aluminum, and nickel-iron-chrome alloys:

Nickel-Chrome

Nickel-chrome, also known as nickel-chromium or chromel, is an alloy composed of 60-80% nickel and 15-25% chromium. It is known for having high resistivity and resistance to oxidation. Nickel-chrome has a typical working temperature range of up to 1400°F (760°C). Some key properties are high durability, corrosion resistance, and ability to maintain strength and resistivity at high temperatures.

Iron-Chrome-Aluminum

Iron-chrome-aluminum, also referred to as Kanthal alloy, contains iron, chromium, and aluminum. It has excellent resistance to hot corrosion and oxidation. Iron-chrome-aluminum alloys have working temperatures ranging from 1500-1800°F (815-980°C). They offer high creep resistance and stability.

Nickel-Iron-Chrome

Nickel-iron-chrome, known as nichrome, contains nickel, iron, and chromium. It provides good ductility and higher resistivity than nickel-chrome. Typical working temperatures are around 1400°F (760°C). Key properties include oxidation resistance, microstructural stability, and ease of manufacture.

Key Properties

High temperature element wire is valued for its specialized properties that enable it to withstand extremely high temperatures. The key properties that make it suitable for heating elements and other high-heat applications include:

High electrical resistivity – The alloy materials used in high temperature element wire typically have high resistivity, which allows them to generate heat efficiently when electrical current passes through the wire. The resistance produces the high temperatures needed.

High melting point – These wires can withstand very high temperatures, often up to 3000°F or more before reaching their melting point. This high melting point allows them to maintain their integrity and shape at sustained high temperatures during operation.

High tensile strength – In addition to withstanding high heat, the alloys used in these wires have high strength and creep resistance even at high temperatures. This allows the wire to remain rigid and not sag or deform, which is essential for heating elements.

The combination of these properties allows high temperature element wire to produce and withstand the extreme heat needed for applications like ceramic kilns, furnaces, and other high-temperature industrial processes.

Insulation Materials

Two of the most common insulation materials used for high temperature element wires are magnesium oxide and aluminum oxide. These materials are used because they can withstand extremely high temperatures without melting or decomposing.

Magnesium oxide, also known as magnesia, is an inorganic compound with the chemical formula MgO. It has a high melting point of 2,852°C, making it effective for insulating wires operating at high temperatures. Magnesium oxide provides good electrical insulation and has low thermal conductivity, meaning it prevents heat transfer to surrounding materials. It is often used in thin sheaths or sleeves around the heating element wire.

Aluminum oxide, commonly called alumina, has the chemical formula Al2O3. With a melting point of 2,072°C, it can withstand the high temps needed for heating elements. Aluminum oxide has high dielectric strength, giving it excellent electrical insulating properties. It also has good thermal shock resistance. Alumina insulation is often used as small ceramic beads threaded onto the wire or as a powder coating.

Both magnesium oxide and aluminum oxide insulations stand up to the extreme temperatures that high temperature element wires must operate at continuously. Their high melting points and electrical insulation properties make them well-suited for sheathing and insulating these specialized wires.

Manufacturing Process

High temperature element wire goes through a specialized manufacturing process to achieve its high heat resistance and durability. The process begins with the drawing process, where the raw metal alloy is pulled through a series of dies to reduce its diameter down to the desired wire gauge.^[1]

Once drawn down to size, the element wire undergoes an annealing process where it is heated to a high temperature, then cooled, to relieve internal stresses from the drawing process. This annealing makes the wire more malleable and ductile.^[1]

After annealing, the element wire is cut to length and fitted with terminals or other connections. A protective insulation, such as magnesium oxide, may be applied. The finished wire is then ready for use in heating elements and other applications requiring high temperature durability.

^{[1] https://www.thermalcorporation.com/}

Applications

High temperature element wire is commonly used in various high heat applications such as:

Electric heaters – The heating elements in electric heaters like space heaters, water heaters, and electric ovens utilize high temperature element wire to generate the necessary heat. The wire’s ability to withstand high temperatures makes it ideal for converting electricity into heat safely and efficiently in residential and commercial heating applications.

Furnaces – High temperature element wire is a key component in furnaces used for metal processing, glassmaking, and other industrial processes requiring extremely high temperatures. The wire heats up when electrical current passes through it, allowing furnaces to reach temperatures of over 1,000°C in some cases. Proper selection of element wire alloy and insulation is critical for performance and safety.

Kilns – Kilns used for firing ceramics or annealing glass rely on high temperature element wire to generate the heat required inside the kiln chamber. From small hobbyist kilns to large industrial kilns, the element wire loops are designed to withstand repeated heating cycles at temperatures exceeding 1,200°C. The wire’s longevity and reliability make it well-suited for kiln applications.

Advantages Over Other Materials

High temperature element wires made from nickel-chromium and nickel-iron alloys offer some key advantages over wires made from other materials like copper or tungsten.

High temperature wires can withstand much higher temperatures than copper wires. Copper has a working temperature up to about 200°C before annealing, whereas nickel-chromium alloys can work up to about 1300°C. This allows high temperature wires to be used for heating elements and other applications requiring high heat.

High temperature nickel alloy wires are also more ductile and flexible than tungsten wires. Tungsten is very brittle and prone to breakage when bent or flexed. The nickel alloys can be bent and shaped easily without damage. This makes them easier to work with for forming heating elements and coils.

According to this Quora discussion, a thin tungsten wire filament can reach higher temperatures than a thick copper wire when used in lighting applications: https://www.quora.com/Which-one-is-better-as-a-filament-a-thick-copper-wire-or-a-thin-tungsten-wire-Why

However, the flexibility and ductility of the nickel alloys makes them preferable for many heating element applications where shaping, bending, and longevity are important.

Cost Analysis

The cost per foot of high temperature element wire varies significantly depending on the gauge, or thickness, of the wire. Thinner gauges, like 20 AWG, can cost around $1-2 per foot, while thicker gauges like 6 AWG may cost $5-10 per foot.

Compared to standard building wire like copper, high temperature element wire is substantially more expensive due to the specialized alloys and insulation required. Building wire costs around $0.50-2 per foot, while high temp wire starts around $1 per foot and goes up dramatically for the thicker gauges.

High temperature element wire is also more costly than other types of heating elements, like Nichrome wire. Nichrome wire provides lower maximum temperatures, around 1400°F vs 2300°F for high temp alloys, but costs around $0.50-1 per foot. So applications requiring extremely high temperatures must pay a premium for wires like Kanthal that can withstand those temperatures.

When selecting high temperature element wire, users must balance performance needs with budget constraints. While thinner gauges are less expensive, they may not be suitable for high wattage applications. Heavier gauges can handle more power but have a higher upfront cost. Overall, high temperature wires deliver capabilities not possible with standard building wire, but at a higher price point.

Safety Considerations

High temperature elements can reach extremely high temperatures, so proper safety precautions need to be taken to avoid risks like overheating and electric shocks. According to the Evenheat Knife Oven datasheet, the special high temperature alloy wire used can reach up to 2350°F, far higher than standard resistance wire.

To prevent overheating, the element wire should be properly rated for the expected operating temperature. The insulation and wiring should all be capable of withstanding the maximum temperature without melting or catching fire. There should be adequate space and ventilation around the heating element as well. Periodically inspecting elements for signs of damage or deterioration is also important.

Proper insulation is critical for safety. Ceramic insulators are typically used. The thickness and material depends on the temperature rating. Using insufficient insulation can allow electricity to arc or leak. Regular inspection and replacing damaged insulation can help prevent electric shocks.