Thermal Bimetallic Strip / Thermostatic Bimetal

Thermobimetallic Strip: Technical Characteristics, Applications, and Features

General Technical Characteristics

A thermobimetallic strip is a composite material consisting of two metal layers with different coefficients of thermal expansion. When the temperature changes, the layers expand or contract at different rates, causing the strip to bend. This property makes thermobimetallic strips suitable for temperature-sensitive applications. The main characteristics of a thermobimetallic strip include:

• Material Composition: Two metal layers with different thermal expansion properties
• Thickness: Varies depending on the application
• Thermal Expansion Coefficient: Different for each metal layer
• Electrical Conductivity: Varies depending on the metals used
• Mechanical Strength: Depends on the material combination and intended application
• Manufacturing Methods: Rolling, bonding, or cladding

The strip is usually supplied in rolls, coils, or sheets, depending on the grade and application, making it suitable for further processing into temperature-sensitive components.

Applications

Thermobimetallic strips are widely used in industries where temperature changes need to be converted into mechanical movement or switching action. Common applications include:

• Thermostats: Used in heating and cooling systems to regulate temperature
• Circuit Breakers: Used as thermal elements that respond to excessive current and overheating
• Temperature Sensors: Convert temperature variations into mechanical displacement
• Bimetallic Relays: Control electrical circuits based on temperature changes
• Automotive Industry: Used in fuel gauges, temperature sensors, thermal switches, and engine control systems
• Industrial Controls: Provide temperature-dependent actuation in various machinery
• Household Appliances: Used in thermal switches and temperature control systems

Features of Thermobimetallic Strips

The main advantage of thermobimetallic strips is their ability to respond to temperature changes through controlled bending. Some key features include:

• Sensitivity to Temperature Changes: Provides a predictable response to temperature variations
• Durability: Suitable grades can withstand repeated thermal cycling
• Corrosion Resistance: Depends on the metals and alloys used in the strip
• Customizable Thickness and Width: Can be selected according to specific application requirements
• Passive Operation: Can operate without an external power source in mechanical applications

The thermal response and mechanical characteristics of the strip depend on its grade, dimensions, metal combination, and operating conditions.

Chemical Composition

The exact chemical composition of a thermobimetallic strip depends on its intended application and selected grade. It generally consists of two bonded metal layers with different coefficients of thermal expansion. The alloys used for the active and passive layers are selected to provide the required thermal response and mechanical properties.

Depending on the type of thermobimetal, the layers can be based on iron, nickel, copper, or other alloys. The exact composition varies between grades and applicable standards.

The exact chemical composition should be determined according to the particular thermobimetal grade and applicable standard.

Mechanical Properties

Thermobimetallic strips exhibit mechanical properties that make them suitable for repeated use in thermal control applications. Typical properties include:

• Flexibility: Ability to bend in response to temperature changes
• Fatigue Resistance: Ability to withstand repeated thermal cycling
• Elastic Modulus: Varies depending on the material combination
• Deflection: Depends on the difference in thermal expansion between the two layers and the strip geometry
• Operational Temperature Range: Depends on the selected thermobimetal grade
• Mechanical Strength: Depends on the alloys, dimensions, and intended operating conditions

Thermobimetallic Tapes GOST

Thermobimetallic tapes according to GOST specifications include:

• TB 107/71
• TB 129/79
• TB 138/80
• TB 148/79
• TB 200/113
• and others

The appropriate grade is selected according to its thermal, mechanical, and electrical characteristics and the requirements of the intended application.

Thermobimetallic DIN EN Tapes

Thermobimetallic tape grades used according to DIN EN specifications include:

• TB 20110
• TB 1577A
• TB 1555
• TB 1545
• TB 1435
• TB 1425
• TB 1511
• TB 1170A
• TB 1109
• TB 0965
• TB 1075
• and others

The exact properties of each grade depend on its alloy composition and applicable technical specification.

Thermal Bimetallic Tapes JIS

Thermal bimetallic tapes according to JIS specifications include:

• TM1
• TM2
• TM3
• TM4
• TM5A
• TM6
• and more

Different JIS grades have different thermal expansion and mechanical characteristics and are selected according to the requirements of the finished component.

Conclusion

Thermobimetallic strips are composite materials used in temperature-sensitive applications where a change in temperature needs to produce mechanical movement or switching action. Their thermal response depends on the combination of metals, difference in thermal expansion, dimensions, and operating conditions.

They are used in thermostats, circuit breakers, relays, sensors, automotive systems, household appliances, and industrial control equipment. Different thermobimetal grades are available for specific temperature ranges, mechanical requirements, and technical applications.