Everyone deals with steel almost every day, but is your classification of steel really clear?
How did steel come from?
The main raw material for iron making is iron ore. The main component of iron ore is Fe2O3, which has no carbon. The second raw material for iron making is coke. Part of the coke in the iron making process remains in the molten iron, causing carbon in the molten iron.
The production of iron and steel is made from iron ore and iron is used as raw material for steelmaking. The process of steelmaking is mainly the process of removing carbon. It is not possible to remove carbon. Steel needs a certain amount of carbon to achieve the best performance.
In order to improve the performance of steel, some alloying elements need to be added on the basis of smelting carbon steel.
- Pig iron (cast iron) – containing C is 2.0 to 4.5%
- Steel (carbon steel) – containing C is 0.05 to 2.0%
- Wrought iron (pure iron) – containing C less than 0.05%
Iron ore → pig iron → steel
Therefore, steel is an alloy of iron and C (carbon), Si (silicon), Mn (manganese), P (phosphorus), S (sulfur), and a small amount of other elements.
In addition to Fe (iron), 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 important metal material in engineering technology.
According to the carbon content, it can be divided into:
According to the carbon content, carbon steel is divided into low carbon steel, medium carbon steel and high carbon steel. As the carbon content increases, the hardness of carbon steel increases and the toughness decreases.
- 1) Low carbon steel – carbon content ≤ 0.25%.
- 2) Medium carbon steel – carbon content > 0.25% ≤ 0.60%.
- 3) High carbon steel – carbon content > 0.60% according to the total content of alloying elements: in order to improve the performance of steel, on the basis of smelting carbon steel, some alloying elements are added and the steel is refined into alloy steel, such as chrome steel, manganese steel, chromium manganese steel, chrome-nickel steel. Alloy steel, also known as special steel, has some special properties, such as high hardness, high wear resistance, high toughness, corrosion resistance and so on. The alloying elements frequently added to steel are Si, W, Mn, Cr, Ni, Mo, V, Ti, and the like.
According to the total content of its alloying elements, it can be divided into:
- 1) Low alloy steel – the total content of alloying elements is ≤ 5%.
- 2) Medium alloy steel – the total content of alloying elements is 5% to 10%.
- 3) High alloy steel – total content of alloying elements > 10%.
Alloy steels are classified according to use:
- 1) Alloy structural steel: used as engineering components (pipes and supports, etc.); various mechanical parts (shafts, gears, springs, impellers, etc.).
- 2) Alloy tool steel: used as measuring tools, molds, tools, etc.
- 3) Special performance steel: such as stainless steel, heat-resistant steel, etc., with special physical or chemical properties.
Source: China Pipe Fittings Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)