Solder
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Solder is a low-melting-point metal alloy used in soldering to join two pieces of metal together. It is melted and flowed into the joint between the two metal pieces, creating a strong and permanent bond once it cools and solidifies.
Solder typically consists of a mixture of tin and lead, or tin, silver, and copper. Different types of solder are available for various soldering applications. Different melting temperatures and compositions suit different metals and environments.