Engineering Question #1216

luke kujawa, a 12 year old male from armada asks on January 28, 2003,

What is the chemical composition of basic aluminum, steel, and brass, and which metal conducts heat the best and why?

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The answer

Barry Shell answered on January 28, 2003

Aluminum is sometimes pure aluminum metal, but is usually alloyed with other metals that are added in small amounts. The Wikipedia entry for aluminum alloys shows their composition.

Steel is mostly made of the element iron. There are hundreds of different kinds of steel alloys which are mostly iron with small amounts of other elements. A chart of some steels is at the Carolina Knife Company. Most steel contains some carbon and silicon, but can contain many other elements. If the steel has more than 10% chromium it is called stainless steel.

Brass is made from about 70% copper and 30% zinc. Sometimes there are other metals in brass. You can find lists of alloys of brass with a web search.

Of the metals above, aluminum conducts heat best, followed by brass, then steel. Here's a table showing the thermal conductivity of metals. Different alloys have different heat conducting properties, too. The reason metals conduct heat so well is the same reason they conduct electricity well. The best electrical conductors are also the best heat conductors. The reason has to do with the easy mobility of electrons within the crystalline structure of the metal at an atomic scale.

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