Description

Thermal bimetal strips (grades 5J20110, 5J1480, 5J1580, 5J1070) offer precise temperature-sensitive deflection for thermostats, circuit breakers, and thermal actuators. GB/T 4461-92 compliant.

Thermal Bimetal Strip

Temperature-Sensitive Bimetal Material for Thermal Control, Switching and Sensing Applications

Hefei Ke Ningman New Energy Materials Technology Co., Ltd. supplies thermal bimetal strip, a temperature-sensitive composite material designed to produce controlled mechanical movement in response to temperature changes.

Thermal bimetal strip is manufactured by permanently bonding two or more metallic layers with different coefficients of thermal expansion. When temperature changes, the different expansion rates of the bonded layers cause the strip to bend or deflect.

This temperature-responsive behavior makes thermal bimetal strip suitable for thermal switches, thermostats, thermal relays, circuit breakers, temperature regulators, temperature indicators, current protection devices, measuring instruments and automatic control systems.

Depending on the required operating temperature, thermal sensitivity, electrical resistance, deflection and mechanical properties, different bimetal combinations and grades can be selected.

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What Is Thermal Bimetal Strip?

Thermal bimetal strip is a temperature-sensitive composite material consisting of two or more bonded metallic layers with different coefficients of thermal expansion.

When the temperature changes:

Temperature Change → Different Thermal Expansion → Bimetal Bending → Mechanical Movement

The resulting movement can be used to open or close an electrical contact, activate a mechanical mechanism, compensate for temperature changes or indicate a temperature condition.

Unlike a conventional single-metal strip, a thermal bimetal combines materials with different thermal expansion characteristics to create predictable temperature-dependent movement.

How Does Thermal Bimetal Strip Work?

A typical thermal bimetal consists of:

Active Layer

The active layer has a relatively higher coefficient of thermal expansion.

When temperature increases, this layer attempts to expand more strongly than the low-expansion layer.

Passive Layer

The passive layer has a lower coefficient of thermal expansion.

It restricts the expansion of the active layer and contributes to the controlled bending behavior of the composite strip.

Intermediate or Resistive Layer

For selected constructions, an intermediate metallic layer may be incorporated to modify electrical resistance, bonding or other functional characteristics.

The actual layer configuration depends on the specific bimetal grade and application.

Thermal Bimetal Strip Working Principle

When a thermal bimetal strip is heated, the high-expansion layer expands more than the low-expansion layer.

Because the two layers are permanently bonded together, they cannot expand independently.

The difference in thermal expansion therefore produces curvature.

When the temperature decreases, the expansion difference changes and the strip moves in the opposite direction.

This reversible temperature-dependent movement can be used as a sensing or actuating mechanism.

Key Properties of Thermal Bimetal Strip

Thermal Sensitivity

Thermal sensitivity determines how strongly the bimetal responds to a temperature change.

For applications requiring precise thermal actuation, the selected grade should be evaluated according to:

• Operating temperature

• Specific thermal curvature / flexivity

• Required deflection

• Element geometry

• Mechanical loading

Coefficient of Thermal Expansion

The difference between the thermal expansion coefficients of the component layers is fundamental to bimetal operation.

A larger expansion difference can produce stronger thermal movement, depending on the material structure and element geometry.

Flexivity

Flexivity is an important performance parameter for thermal bimetal materials.

It describes the thermal curvature response of the material under specified test conditions.

Higher flexivity can be useful for applications requiring greater thermal movement, while lower-flexivity grades may be selected when a more controlled response is required.

Actual flexivity should be specified according to the applicable material standard and test method.

Electrical Resistivity

Some thermal bimetal applications involve electrical current, such as:

• Thermal relays

• Circuit breakers

• Thermal switches

• Overload protection devices

For these applications, electrical resistivity can be an important material-selection parameter.

Temperature Range

Different thermal bimetal grades are designed for different operating temperature ranges.

When selecting a material, consider:

• Minimum operating temperature

• Normal operating temperature

• Actuation temperature

• Maximum operating temperature

• Thermal cycling conditions

The actual temperature range should always be based on the specific alloy grade and technical specification.

Bonding Strength

Because thermal bimetal relies on two or more metallic layers working together, the bond between the layers is critical.

Insufficient bonding can cause:

• Delamination

• Unstable thermal response

• Mechanical failure

• Reduced service life

Layer bonding should therefore be verified according to the applicable specification.

Thermal Bimetal Strip Material Structure

A typical thermal bimetal construction includes:

The exact alloy combination depends on the required temperature range, flexivity, resistivity and application.

Common Thermal Bimetal Alloy Combinations

Depending on the required properties, thermal bimetal systems can use combinations of:

• Nickel-iron alloys

• Nickel-chromium-iron alloys

• Manganese-copper-nickel alloys

• Copper-based alloys

• Low-expansion alloys

• High-expansion alloys

For example, specific bimetal systems may combine a high-expansion alloy with a low-expansion nickel-iron alloy.

Actual alloy combinations should be specified according to the grade supplied by the manufacturer.

Thermal Bimetal Strip Classification

Thermal bimetal materials can be classified according to several important characteristics.

Classification by Operating Temperature

Depending on the grade, products can be designed for:

• Low-temperature applications

• Medium-temperature applications

• High-temperature applications

Classification by Thermal Sensitivity

Thermal bimetal can also be classified according to flexivity or thermal sensitivity.

Typical categories include:

• High-sensitivity bimetal

• Medium-sensitivity bimetal

• Low-sensitivity bimetal

The actual classification should follow the applicable material standard.

Classification by Electrical Resistance

Depending on the electrical application, thermal bimetal materials may be available as:

• Low-resistance series

• Medium-resistance series

• High-resistance series

This classification can be particularly relevant to electrically heated or current-responsive thermal components.

Thermal Bimetal Strip Product Specifications

The following parameters should be provided according to the actual grade:

All numerical specifications should be taken from your own technical datasheet and applicable material standards.

Thermal Bimetal Strip Dimensions

Thermal bimetal strip can be supplied according to customer requirements.

Typical dimensional parameters include:

Thickness

Specify:

• Nominal thickness

• Thickness tolerance

• Total composite thickness

Width

Specify:

• Standard width

• Custom width

• Width tolerance

Coil Dimensions

For coiled material, specify:

• Inside diameter

• Outside diameter

• Coil weight

• Coil length

Surface Condition

Depending on the product and manufacturing route:

• Bright surface

• Polished surface

• Standard mill finish

• Customized surface condition

Thermal Bimetal Strip Applications

Thermal Switches

Thermal bimetal can act as a temperature-sensitive switching element.

When a predetermined temperature is reached, the bimetal moves and changes the electrical contact state.

Applications include:

• Thermal switches

• Temperature controllers

• Automatic protection devices

• Heating equipment

Thermostats

Thermal bimetal strips can be used in thermostatic mechanisms to respond to temperature changes.

Potential applications include:

• Household appliances

• Heating equipment

• Temperature control systems

• Industrial equipment

Thermal Relays

Thermal bimetal can be used in overload protection mechanisms.

When electrical current produces excessive heating, the bimetal responds to the temperature increase and activates a protective mechanism.

Circuit Breakers and Overload Protection

Bimetal elements are used in selected circuit protection devices to provide thermal overload protection.

The thermal response can be designed to trigger mechanical movement when the element reaches a specified temperature condition.

Temperature Indicators

Thermal bimetal can convert temperature changes into mechanical displacement.

This makes it suitable for selected:

• Temperature indicators

• Temperature gauges

• Mechanical indicators

• Measuring instruments

Temperature Compensation

Thermal bimetal materials can also be used to compensate for temperature-induced dimensional or electrical changes in precision mechanisms.

Applications may include:

• Measuring instruments

• Electrical meters

• Automatic control systems

• Precision mechanisms

Automotive Applications

Depending on the grade and design, thermal bimetal can be used in selected automotive thermal-control and protection components.

Potential applications include:

• Thermal switches

• Temperature indicators

• Circuit protection

• Temperature control mechanisms

Industrial Automation

Thermal bimetal materials can be incorporated into automatic control devices where temperature changes must produce a predictable mechanical response.

How to Choose the Right Thermal Bimetal Strip

Selecting thermal bimetal should be based on the complete application rather than only the nominal operating temperature.

1. Determine the Operating Temperature

Identify:

Normal operating temperature

Actuation temperature

Maximum temperature

Minimum temperature

Thermal cycling range

2. Define the Required Thermal Sensitivity

Determine the required:

Flexivity

Deflection

Response sensitivity

Actuation displacement

3. Determine Electrical Requirements

For electrically active applications, evaluate:

Electrical resistivity

Current

Voltage

Contact configuration

Heating method

4. Determine Element Geometry

The final response depends on:

Strip thickness

Strip width

Element length

Curvature

Mounting configuration

5. Consider Mechanical Loading

The application may impose:

Contact force

Spring force

Vibration

Repeated movement

Mechanical constraint

These factors should be considered when selecting the bimetal grade.

6. Consider Thermal Cycling

For products repeatedly exposed to heating and cooling, evaluate:

Response repeatability

Hysteresis

Fatigue

Long-term stability

Stabilization requirements

Thermal Bimetal Strip Manufacturing Process

A typical manufacturing process may include:

Alloy Preparation → Layer Processing → Surface Preparation → Bonding → Rolling → Heat Treatment → Stabilization → Slitting → Dimensional Inspection → Thermal Testing → Final Inspection

The exact process depends on the bimetal construction and material specification.

Key manufacturing controls may include:

• Layer thickness

• Bonding quality

• Total thickness

• Surface condition

• Thermal response

• Electrical resistance

• Dimensional tolerance

Thermal Bimetal Quality Control

Quality control is especially important because thermal bimetal performance depends on the relationship between multiple bonded layers.

Typical inspections may include:

Chemical Composition

Verify each alloy layer according to the applicable specification.

Dimensional Inspection

Check:

• Thickness

• Width

• Length

• Tolerance

• Coil dimensions

Thermal Performance

Depending on the grade:

• Flexivity

• Deflection

• Actuation temperature

• Thermal response

• Temperature stability

Electrical Properties

For applicable grades:

• Electrical resistivity

• Resistance consistency

• Bonding Inspection

Verify the integrity of the bonded interface.

Surface Inspection

Check for:

• Cracks

• Delamination

• Scratches

• Oxidation

• Surface defects

Material Documentation

Depending on customer requirements:

• Material Test Report

• Chemical composition

• Dimensional inspection report

• Thermal-property test report

• Electrical-property report

• Certificate of conformity

Thermal Bimetal Strip vs Conventional Metal Strip

Thermal Bimetal Strip Supplier

Hefei Ke Ningman New Energy Materials Technology Co., Ltd. supplies thermal bimetal strip materials for temperature-sensitive and automatic-control applications.

Our supply capabilities can support:

• Thermal bimetal strip

• Temperature-sensitive bimetal

• High-sensitivity bimetal

• Low-expansion / high-expansion bimetal combinations

• Custom strip dimensions

• Different electrical resistance ranges

• Different thermal sensitivity requirements

• Technical documentation

• Custom material specifications

For a quotation, provide your required:

Alloy Grade + Thickness + Width + Thermal Range + Flexivity + Resistivity + Quantity + Application

Our technical team can evaluate the requirements and recommend an appropriate thermal bimetal material.

How to Request a Thermal Bimetal Strip Quote

Please provide:

• Bimetal grade

• Active layer material

• Passive layer material

• Intermediate layer, if required

• Thickness

• Width

• Coil dimensions

• Required thermal sensitivity

• Operating temperature

• Actuation temperature

• Electrical resistivity

• Application

• Quantity

• Applicable ASTM / GB/T / EN or customer specification

• Inspection requirements

For customized applications, drawings and technical specifications can also be provided for review.

Request a Quote

Frequently Asked Questions

What is thermal bimetal strip?

Thermal bimetal strip is a composite material made by bonding two or more metals with different thermal expansion coefficients. Temperature changes cause the strip to bend or deflect.

How does thermal bimetal work?

When temperature changes, the bonded metal layers expand at different rates. This difference generates mechanical curvature that can be used for switching, sensing, compensation or temperature control.

What is thermal bimetal used for?

Thermal bimetal is used in thermostats, thermal switches, thermal relays, circuit breakers, overload protection devices, temperature indicators and automatic control systems.

What is the difference between thermal bimetal and ordinary bimetal?

Thermal bimetal is specifically engineered to produce predictable mechanical movement in response to temperature changes by combining materials with different thermal expansion characteristics.

What factors determine thermal bimetal sensitivity?

Important factors include the thermal expansion difference between the layers, material properties, layer thickness, total thickness, element geometry, temperature range and mechanical constraints.

What is flexivity in thermal bimetal?

Flexivity is a measure of the thermal curvature response of a bimetal material under specified conditions. It is an important parameter when selecting thermal bimetal for temperature-sensitive applications.

Can thermal bimetal strip be customized?

Yes. Depending on the material system and manufacturing capability, thickness, width, alloy combination, thermal characteristics, electrical resistance and other specifications can be customized.

What information should I provide when buying thermal bimetal strip?

Provide the required alloy grade, thickness, width, operating temperature, actuation temperature, thermal sensitivity, electrical resistivity, application and quantity.