In addition, because Babbitt metal melts at a low temperature, it can be poured into a mold fitted around a steel shaft without harm to the shaft. Once cooled, the metal forms a bearing in which the shaft rotates with little wear. Most kinds of solders are alloys of lead and from one third to two thirds tin. Alloyed, these metals melt at a lower temperature than either does by itself. Brazing solder, which forms stronger joints than ordinary solder, is made of equal parts of copper and zinc.
Silver is added for jewelry work.
This metal makes a good fuse in an electric circuit, for when it is heated by an excess of current that might damage electrical apparatus or cause a fire, it melts, stopping the flow of current. Safety plugs made of similar alloys are used in boilers, water heaters, and pressure cookers. When the internal heat in such vessels passes the danger point, the plug melts, allowing steam to escape before the vessel explodes. Sprinkler systems hold water under pressure with a safety plug that melts and releases the water when fire causes the room temperature to rise. Some fire alarm systems use a similar safety plug.