Surface type heating element having controlled oxide layer and manufacturing method thereof

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Solution Overview

Problem

Existing surface type heating elements for electric ranges face challenges such as material elution at high temperatures, low operation temperatures due to limited melting points, and issues with fracture toughness, thermal expansion, and adhesion to substrates.

Innovation Solution

A surface type heating element made from a NiCr alloy with controlled oxygen content (1-3 wt%) is developed, which allows for high-temperature operation without material elution, while maintaining high fracture toughness, low thermal expansion, and improved adhesive strength.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If metal components with low melting points are used in heating elements, then ease of manufacture is improved, but operation temperature is limited to about 400°C and material elution occurs

Engineering Contradiction:

Improveease of manufactureVSAvoidoperation temperature

Core Design Contradiction:

Ease of manufactureVSTemperature

Solution Approach 1:

The patent uses a composite structure consisting of a metal heating element layer (containing Fe, Ni, Cr, and other elements) combined with a glass-ceramic layer. This composite material approach allows the metal layer to provide electrical conductivity and heating function while the glass-ceramic layer provides high-temperature stability and prevents material elution, enabling operation at temperatures above 400°C without sacrificing manufacturability.

Inventive Principle:

Principle #40Composite materials

2Temperature

If metal components with high melting points are used in heating elements, then operation temperature is improved, but fracture toughness decreases and adhesion to substrate deteriorates

Engineering Contradiction:

Improveoperation temperatureVSAvoidfracture toughness

Core Design Contradiction:

TemperatureVSStrength

Solution Approach 1:

The patent employs a composite material system where the metal heating element layer is combined with a glass-ceramic layer. The glass-ceramic layer compensates for the low fracture toughness of metal components by providing ceramic-level strength and thermal stability, while the layered composite structure maintains good adhesion to the substrate through controlled thermal expansion properties.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent carefully controls the composition parameters of the metal layer (specific ratios of Fe, Ni, Cr, and other elements) and the glass-ceramic layer to optimize the coefficient of thermal expansion. This parameter control ensures that the composite material has matched thermal expansion properties with the substrate, preventing adhesion failure while maintaining high-temperature operation capability and fracture toughness.

Inventive Principle:

Principle #35Parameter changes

3Temperature

If thermal firing is used to manufacture heating elements with high melting point components, then high-temperature operation is achieved, but oxidation of metal components increases electrical resistivity

Engineering Contradiction:

Improveoperation temperatureVSAvoidelectrical resistivity stability

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The patent applies a protective atmosphere (nitrogen or vacuum) during the thermal firing process before oxidation can occur. This preliminary protective measure prevents oxidation of the metal heating element components during the high-temperature sintering process, maintaining low electrical resistivity and stable conductivity while still achieving the necessary high-temperature operation capability.

Inventive Principle:

Principle #10Preliminary action

4Reliability

If protective atmosphere is used during firing to prevent oxidation, then electrical resistivity is maintained, but adhesion between heating element layer and substrate decreases

Engineering Contradiction:

Improveelectrical resistivityVSAvoidadhesion

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent optimizes the composition parameters of the metal layer (specific ratios of Fe, Ni, Cr, and other elements) and the glass-ceramic layer to control the coefficient of thermal expansion. This parameter control ensures that the composite material has matched thermal expansion properties with the substrate, preventing adhesion failure while maintaining high-temperature operation capability and fracture toughness.

Inventive Principle:

Principle #35Parameter changes

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 NiCr alloy-based surface type heating element enables stable operation at 400°C or more, enhances thermal shock resistance, ensures reliable conductivity, and improves the lifetime and reliability of electric range cooktops.

Implementation Method 1

a surface type heating element which generates heat using electricity

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

controlled oxide layer... allows for high-temperature operation without material elution

Methodology Applied

Scientific EffectOxidation: Oxidation

Data Source

PatentUS12273966B2Surface type heating element having controlled oxide layer and manufacturing method thereof

Publication Date: 2025.04.08 LG ELECTRONICS INC

AI summary

Discussed is a surface type heating element including a surface type heating element layer including NiCr alloy powders, necks between powder particles of the NiCr alloy powders, and passivation oxide layers formed on a surface of the NiCr alloy powders.