Surface Heating Element Buffer Layer to Reduce Thermal Stress
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Solution Overview
Problem
Existing surface type heating elements for electric ranges face challenges such as low operating temperatures, material elution, thermal shock, and limited substrate material options due to high melting point requirements, as well as issues with thermal expansion mismatch and oxidation at high temperatures.
Innovation Solution
A surface type heating element design featuring a buffer layer with a controlled thermal expansion coefficient between 50 and 100 × 10^-7 m/°C, combined with a NiCr alloy layer, which reduces thermal stress and oxidation risks, and allows for high-temperature operation up to 450 °C without substrate deformation, using materials like glass frit and NiCr alloys with specific composition ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If metal components with low melting points are used in the heating element, then the heating element can be manufactured easily, but the operation temperature is limited to about 400°C and metal elution occurs
Solution Approach 1:
The heating element uses a composite structure combining a metal powder layer (Ni, Cu, or their alloys) with a ceramic layer (alumina or zirconia). The metal powder layer provides electrical conductivity and heating function, while the ceramic layer provides high-temperature stability and structural support, enabling operation above 400°C without metal elution.
Solution Approach 2:
The invention changes the physical state of metal from bulk metal components to metal powder particles embedded in a ceramic matrix. This parameter change allows the metal to maintain its heating functionality while the ceramic matrix prevents elution and enables higher operating temperatures.
2Temperature
If ceramic materials are used in the heating element, then high-temperature operation is enabled, but the materials are brittle and susceptible to thermal fatigue and thermal shock
Solution Approach 1:
The composite structure of metal powder embedded in ceramic matrix combines the high-temperature stability of ceramics with the thermal shock resistance and fracture toughness of metals. The metal particles act as stress-absorbing inclusions that prevent crack propagation, improving reliability under thermal cycling.
Solution Approach 2:
The heating element has non-uniform composition with metal powder distributed throughout the ceramic matrix. The metal-rich regions provide ductility and thermal shock resistance, while the ceramic-rich regions provide high-temperature stability, creating local quality variations that optimize overall performance.
3Temperature
If high-temperature firing is used to manufacture the heating element, then high melting point materials can be utilized, but the substrate material is limited and manufacturing complexity increases
Solution Approach 1:
The invention uses low-temperature sintering (800-950°C) instead of high-temperature firing, changing the processing temperature parameter. This allows the use of glass-ceramic substrates with lower melting points, expanding substrate material options and simplifying manufacturing while still achieving dense, reliable heating elements.
Solution Approach 2:
The heating element structure has distinct functional layers: a glass-ceramic substrate providing mechanical support, a buffer layer for thermal expansion matching, and a composite heating layer with metal powder and ceramic matrix. This local quality differentiation allows each layer to be optimized for its specific function, enabling low-temperature processing.
4Adaptability or versatility
If the heating element layer and substrate have different coefficients of thermal expansion, then material selection is flexible, but thermal stress increases and adhesion decreases
Solution Approach 1:
A buffer layer is introduced as an intermediary between the heating element layer and the substrate. This buffer layer has thermal expansion properties that match both layers, acting as a stress-absorbing transition zone that reduces thermal stress and prevents delamination while maintaining material selection flexibility.
Solution Approach 2:
The buffer layer is made of glass-ceramic composite material that can be formulated to have intermediate thermal expansion coefficients. This composite structure allows tuning of thermal properties to match both the metal-ceramic heating layer and the substrate, minimizing thermal stress.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables reliable high-temperature operation, improved fracture toughness, reduced thermal shock, and extended product lifetime by minimizing thermal stress and oxidation, while allowing for a broader range of substrate materials and reducing manufacturing time and energy consumption.
Implementation Method 1
a surface type heating element layer 30 formed by sintering a predetermined powder containing an oxide powder and disposed on the buffer layer 20
Implementation Method 2
the buffer layer 20 and having a thermal expansion coefficient of (50 to 100)×10^-7 m/°C
Data Source
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AI summary
The present disclosure relates to a surface type heating element which generates heat using electricity and a method of manufacturing the surface type heating element. The surface type heating element according to an embodiment of the present disclosure includes: a substrate; a buffer layer disposed on the substrate and having a thermal expansion coefficient of (50 to 100)*10-7 m/°C; and a surface type heating element layer disposed on the buffer layer and including a NiCr alloy, and thus it can be used even at a high operating temperature of 450 °C or more, suppresses the elution of the material itself, and allows thermal stress caused by a difference in coefficient of thermal expansion between the surface type heating element layer and the substrate to be reduced while having high fracture toughness, a low coefficient of thermal expansion, and heat resistance.