1 PHYSICAL PROPERTIES OF METALS What is a metal? Technically, it is an element which has the following properties: It is solid at room temperature (mercury is an exception) It is opaque (that is, you can’t see through it) It conducts heat and electricity It reflects light when polished It expands when heated, contracts when cooled It usually has a crystalline structure Some metals – gold, silver, copper, and zinc, for example – are often used in essentially pure form. However, most metals used for industrial purposes are actually alloys, not pure metals. An alloy is a metal to which another metal (or metals), or a non-metallic element such as carbon or silicon, has been added to modify the physical or mechanical properties of the pure metal. Iron, aluminum, titanium, and magnesium are used predominantly in alloy form. Pure iron, in fact, is something of a laboratory curiosity. Steel and cast iron are properly considered alloys of iron. Even though a low-carbon steel may contain more than 99% iron, and not more than 0.30% carbon, that little bit of carbon makes a lot of difference. The distinction between ”metal” and ”alloy” is seldom observed in the everyday world, since alloys always have the general properties listed above as applying to metals. When we speak of ”low-alloy” or ”high alloy” steels we are not overlooking the fact that steel is an alloy of iron and carbon; instead, we are indicating that the low-alloy steel includes relative small percentages of other metals, and that high-alloy steels contain substantial amounts of other metals (most frequently, chromium or nickel). Hard- Surfacing, Building Fusion Welding Carbon Welding Non-Ferrous Metals Heating & Heat Treating Braze Welding Welding Cast Iron Welding Ferrous Metals Brazing & Soldering Equipment Set-Up Operation Equipment For OXY-Acet Structure of Steel Mechanical Properties of Metals Oxygen & Acetylene OXY-Acet Flame Physical Properties of Metals How Steels Are Classified Expansion & Contraction Prep For Welding OXY-Acet Welding & Cutting Safety Practices Manual Cutting Oxygen Cutting By Machine Appendices Testing & Inspecting