High temperature resistant heating plateUsually refers to the working temperature atAbove 300 ° CEven up to1800°CHeating elements or equipment substrates. The material selection is a systematic project that requires comprehensive consideration of multiple factors.

1、 CommonHigh temperature resistant heating plateMaterial Classification

We can understand it from two levels:Material of heating elementAndMaterial of substrate/carrier boardBoth require high temperature resistance, but the emphasis is different.

（1） Material of heating element (the part that truly generates heat)

This type of material determines the maximum temperature and electric thermal conversion efficiency of the heating plate.

　　Resistance wire (for low and medium temperature heating plates,<600 ° C)

　　Common materials:Nickel chromium alloys (such as Cr20Ni80) and iron chromium aluminum alloys (such as Cr25Al5).

　　Features:Mature technology with low cost. Nickel chromium wire has good antioxidant properties and long lifespan; Iron chromium aluminum wire has good high-temperature strength, but it is prone to brittleness at high temperatures. Mainly used for small heating plates in laboratories or industrial drying equipment.

　　Silicon carbon rod (working temperature: 600 ° C-1600 ° C)

　　Material:Silicon carbide (SiC).

　　Features:At high temperatures, the resistance has a positive temperature coefficient and has an automatic current limiting protection function. Has good resistance to rapid cooling and heating, but gradually oxidizes and becomes finer at high temperatures, ultimately leading to fracture. Suitable for muffle furnaces, experimental electric furnaces, etc.

　　Silicon molybdenum rod (working temperature: 700 ° C-1800 ° C)

　　Material:Molybdenum disilicide (MoSi ₂).

　　Features:CurrentlyOne of the most mainstream high-temperature heating elementsAt temperatures above 400 ° C, a dense quartz glass (SiO ₂) passivation film will form, preventing further oxidation and exhibiting excellent oxidation resistance. It is brittle at room temperature and should be avoided from collision. Commonly used in high-temperature sintering furnaces, crystal growth furnaces, etc.

　　Molybdenum, tantalum, tungsten and other metal heating elements (working temperature:>1500 ° C)

　　Material:Pure metal or alloy.

　　Features:High melting point, capable of achieving ultra-high temperature heating (up to 2000 ° C or above) in vacuum or inert atmosphere. But theyHighly prone to oxidationIt must be used in a protective atmosphere or vacuum. Expensive cost and difficult processing. Used in fields such as special metallurgy and semiconductor single crystal furnaces.

　　Non metallic heating element

　　Graphite:Good conductivity, can be used as a heating element in vacuum or inert atmosphere (~2500 ° C), but it is prone to oxidation at high temperatures and requires protection.

　　Carbon fiber/carbon felt:New materials have fast heating and good high-temperature strength, but they are also afraid of oxidation.

（2） Substrate/carrier board material (the part that carries the heating element and comes into contact with the heated object)

This type of material needs to have excellent high temperature resistance, thermal conductivity, and mechanical strength.

　　Mica board (working temperature:<500 ° C-800 ° C)

　　Features:Made from natural or synthetic mica, it has good insulation, uniform thermal conductivity, excellent flexibility, and low cost. It is the most commonmedium and low temperatureThe material of the heating plate substrate is widely used in household appliances (electric heaters, ovens), industrial heating pads, etc.

　　Ceramic board (working temperature: several hundred ° C to>1600 ° C)

　　Common types:

　　Aluminum oxide ceramics (Al ₂ O3):Commonly used high-temperature substrates, with a content of 95% -99%. Excellent insulation, thermal conductivity, and mechanical strength, with moderate cost. Suitable for most industrial heating applications.

　　Aluminum nitride ceramics (AlN):Thermal conductivitygood(much higher than alumina), with a thermal expansion coefficient that matches silicon chips, it is an ideal material for electronic packaging and heat dissipation substrates, but成本高昂.

　　Silicon carbide (SiC):High hardness, good thermal conductivity, high temperature resistance, corrosion resistance, but high brittleness, difficult processing, and high cost. Used for working conditions.

　　Features:High temperature resistance, insulation, and good chemical stability. yeshigh temperatureThe substrate of the heating plate.

　　Metal substrate (working temperature:<500 ° C)

　　Common materials:Aluminum alloy, stainless steel.

　　Features:Thermal conductivityJiaEasy to machine and install. But it is usually not insulated and needs to be insulated with heating elements (such as resistance wires). Commonly used in applications that require rapid heat transfer and mechanical strength, such as the lower layer of copper-clad ceramic substrates (DBC).

　　composite material

　　For example:The "mica+ceramic" composite board aims to combine the advantages of both and is used for specific temperature ranges.

2、 Selection criteria and decision-making process

When selecting materials for high-temperature resistant heating plates, the following factors should be systematically considered and prioritized:

　　1. Maximum operating temperature (primary factor)

This is the hardest constraint condition. It is necessary to ensure the long-term service temperature of the selected materialaboveYour maximum process temperature, with a certain safety margin (usually recommended margin ≥ 50 ° C-100 ° C).

　　< 300°C：Optional ordinary mica board or metal substrate.

　　300°C - 800°C：High performance mica board or 95% alumina ceramic board is preferred.

　　800°C - 1200°C：Aluminum oxide ceramic plate must be selected as the substrate, and silicon carbon rod can be chosen as the heating element.

　　> 1200°C：Aluminum oxide or ceramic substrate (such as SiC) and heating element silicon molybdenum rod must be selected. If>1500 ° C, MoSi ₂ or metal heating element+vacuum/protective atmosphere should be considered.

　　2. Atmosphere and environment (extremely critical)

The performance of materials varies greatly in different atmospheres.

　　Oxidative atmosphere (air):The vast majority of metals will oxidize and fail, requiring the use of ceramic or special alloys (such as Inconel) materials. Silicon molybdenum rods exhibit excellent performance in this environment.

　　Reductive atmosphere (H ₂, CO):Many oxides can be reduced, leading to material failure or contamination of the workpiece. At this time, materials such as graphite, molybdenum, tungsten, etc. should be selected, or a protective layer should be applied on the surface.

　　Vacuum environment:Avoiding oxidation issues, but considering the material's evaporation rate and thermal radiation. Metal and graphite are commonly used choices.

　　Corrosive atmosphere (acid, alkali, salt spray):Chemical inert materials such as high-purity alumina ceramics, platinum, or special coatings should be selected.

　　3. Power density and thermal distribution

　　Power density (W/cm ²):Heating power per unit area. The higher the power density, the higher the requirements for the material's thermal conductivity and heat shock resistance. Ceramic substrates typically can withstand higher power densities than mica plates.

　　Uniformity of thermal distribution:If uniform heating is required, the thermal conductivity of the substrate is crucial. Metal substrates and aluminum nitride ceramics have advantages in this regard. The arrangement of the heating element also directly affects the heat distribution.

　　4. Insulation requirements

If the heating plate needs to be equipped with an electric heating circuit or isolated from the heated conductive object, then the substrateElectrical insulationIt's just necessary. Mica and ceramics are excellent insulators, while metal substrates do not possess this characteristic.

　　5. Mechanical strength and thermal shock resistance

　　Mechanical strength:The ability of a material to resist external forces such as vibration and impact. Metals and certain ceramics (such as SiC) have higher strength.

　　Thermal shock resistance:The ability of a material to resist cracking under rapid temperature changes. This depends on the thermal expansion coefficient and thermal conductivity of the material. For example, quartz glass has an extremely low coefficient of thermal expansion and thermal shock resistance; And glass is very poor. Silicon molybdenum rods are very brittle at room temperature, so extra care should be taken when handling them.

　　6. cost budget

Cost is a practical consideration factor. Roughly speaking, from low to high:Mica plate<metal substrate<alumina ceramic<aluminum nitride ceramic ≈ SiC<MoSi ₂ heating element<molybdenum/tungsten heating elementWe need to find the best balance between performance and cost.

Summary and selection process diagram

　　Core idea:​First set the temperature, then consider the environment, balance performance, and finally weigh the cost.

　　Clarify process parameters:The highest temperature? Atmosphere? (Air/Vacuum/H ₂?)? ）Do you need insulation? What is the required power density?

　　Screening for heating elements:Determine the available types of heating elements (such as silicon molybdenum rods, resistance wires, etc.) based on temperature and atmosphere.

　　Select substrate:Select matching substrates (such as mica, alumina ceramics) based on temperature, atmosphere, thermal conductivity, and insulation requirements.

　　Comprehensive evaluation:Evaluate factors such as mechanical strength, lifespan, and supplier support.

　　Make a decision:The chosen solution is based on meeting all technical requirements.

Through such systematic analysis and selection, we can ensure to find a reliable, efficient, and economical solution for high-temperature resistant heating plates for your application.