Steel is an alloy of iron with C, Si, Mn, P, S and a small amount of other elements. In addition to Fe, the content of C plays a major role in the mechanical properties of steel, so it is collectively referred to as iron-carbon alloy. It is the most important and most used metal material in engineering technology.

Classification and nature

According to different carbon content, iron-carbon alloys are divided into two major categories: steel and pig iron. Steel is an iron-carbon alloy with a carbon content of 0.03% to 2%. Carbon steel is the most commonly used ordinary steel, which is convenient for smelting, easy to process, low in price, and can meet the requirements of use in most cases, so the application is very common. Carbon steel is divided into low carbon steel, medium carbon steel and high carbon steel according to the carbon content.

As the carbon content increases, the hardness of carbon steel increases and the toughness decreases. Alloy steel, also known as special steel, adds one or more alloying elements to the carbon steel to provide special properties such as high hardness, high wear resistance, high toughness, corrosion resistance, and the like. The alloying elements frequently added to steel are Si, W, Mn, Cr, Ni, Mo, V, Ti, and the like. China’s alloy steel resources are quite rich. Except for Cr and Co, the Mn grade is low, and the reserves of W, Mo, V, Ti and rare earth metals are very high.

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