To understand metal, start with iron. Iron is the most abundant metal element on earth and the basic chemical element of iron. For centuries, iron stoves have been heating limestone and iron ore that have been excavated from the ground. The intense heat melts the rock and iron ore, accompanied by several chemical reactions, the lighter liquid rock rises to the top, and the heavier liquid iron sinks to form pig iron. This pig iron is an intermediate step to the final product.
Historically, wrought iron is a building product made from this pig iron. The wrought iron is mainly pure iron (with some slag and a small amount of carbon added). The wrought iron is actually "forged" (ie processed or hammered) into strips that have been used as building materials for thousands of years. The wrought iron has toughness and toughness and is easy to weld. Due to the lack of carbon content required for tempering, the hardness of wrought iron is not sufficient as a good tool for tools or weapons.
The other end product of pig iron is the alloy. The alloy is a combination of two or more elements, at least one of which is a metal. Most of the metals used in construction are alloys. For example, steel is an alloy in which iron and carbon are the main elements. In general, iron-carbon alloys with a carbon content of up to 2.1% are considered to be steel, and iron-carbon alloys with a large carbon content are cast iron.
Cast iron is made by remelting pig iron in a blast furnace, removing undesirable elements such as phosphorus and sulfur, adjusting the carbon content, and adding other elements. The resulting alloy, commonly referred to as grey cast iron, has high corrosion resistance and high compressive strength, but is often brittle and difficult to weld. Historically, cannons and shells were made of grey cast iron and some early bridges.
Steel is an alloy that has great uses in today's construction industry. Hot-rolled steel, the most common is the steel beam and steel column in the construction project. It is in the steel mill to transform the steel into a typical shape by rolling hot steel between large rolls: W, S, C, angle, pipe section, pipe Wait. Most thermoformed steels have a yield strength of 36,000 psi or 50,000 psi.