bimetalen

A bimetal (or bimetalen in some languages) refers to an object made from two distinct metals that are bonded together to form a single component. The two metals retain their separate properties, but together they create characteristics that neither metal alone would provide. Common forms include laminated bimetals (two metal layers bonded together) and bimetal strips (a pair of metals joined along a common edge).

Manufacturing methods for bimetals include mechanical bonding, diffusion bonding, soldering or brazing, and rolling or lamination to form thin, layered composites. The choice of metals is driven by desired properties such as hardness, strength, corrosion resistance, and, importantly, the difference in thermal expansion between the two metals.

A key phenomenon is the differential thermal expansion: if the two metals expand by different amounts with temperature change, a bimetal strip or plate bends or curls. This behavior is exploited in mechanical thermostats, thermal switches, and self-actuating devices where temperature changes need to trigger motion without electronics. Bimetal strips are also found in some measuring instruments and timekeeping devices.

Bimetal can also describe coins that use two different metals in a single coin, typically with a metal core surrounded by a different outer ring. This construction improves durability and provides anti-counterfeiting features; for example, many modern euro coins are bimetallic.

Historically, the concept extends to bimetallic monetary standards, where two metals (commonly gold and silver) serve as monetary metals. In modern engineering, however, the term more often refers to the two-metal composite used for mechanical and thermal applications.