What is the composition of steel

 

Iron-carbon alloys are called steel, which with a carbon content of between 0.02% and 2.11%. Steel chemical composition is a huge difference in different steel types. Steel only containing carbon element, which is called carbon steel or ordinary steel. And the steel always with different alloy element to satisfy different use. Such as Manganese, Nickel, Vanadium and etc. The information of elements is as below.

Carbon

It is the most important steel chemical composition. No matter what types of steel, it always at there. The carbon content in steel higher, the yield point and tensile strength will increase. But the plasticity and impact resistance will decrease. When the carbon content is bigger than 0.23%, its weldability would get bad. So if you need the low alloy structural steel to weld, its carbon content is not bigger than 0.20%. More carbon content in it, it will get lower atmospheric corrosion resistance. So the high carbon steel which was put outside is always susceptible to corrosion. By the way, carbon element can increase the cold brittleness and age sensitivity of steel.

Chromium

Chromium element in steel, which increases wear resistance, hardness and corrosion resistance. If the steel has the chromium content is bigger than 13%, it always is called stainless steel. But all steel will rust if not care for it in the right way.

Manganese

It is an important austenitic stabilizing element which could help to create texture structures. And it also increases the stiffness, strength and wear resistance. It is a great deoxidizing agent and desulfurizer in the steel making process. Universal steel with 0.30-0.50% manganese content. People always called it as manganese steel which has the manganese content is bigger than 0.70%. Its hardness and strength are better than universal steel. The elements could increase the hardening capacity and hot-working character. Such as the yield stress of 16Mn steel is higher 40% than A3 steel. The steel with a manganese content at 11%-14%, then it has high wear resistance. So it is used to make excavator buckets, ball mill liners and etc. The higher the content of manganese, the lower the resistance to corrosion and lower welding performance.

Molybdenum

It is a carbonizing agent. That could prevent steel from becoming brittle and keep the strength of steel in high temperatures. It is the main elements for lots of steel. And the self-hardening steel ( A-2,ATS-34) always with 1% or more molybdenum to make it can harden in the air.

Nickel

Nickel element can improve the strength of steel and keep the good ductility and toughness. Nickel has high corrosion resistance to acids and bases. And it has rust and heat resistance at an environment of high temperatures.

Silicon

It is a good material as a reducing agent and deoxidizing agent in the steel making process. So the piping steel always with 0.15%-0.30% silicon content. If the content of Si is more than 0.50%-0.60% in steel, it would be called an alloying element. Si can hugely increase the elastic limit and tensile strength of steel. So it is great material of spring steel. Adding Si to structural steel about 1.0%-1.2%, which can make the strength increase 15%-20%. Si combined with Mo, tungsten, Cr and etc, it could effectively increase the erosion resistance and oxidation resistance. The Si content is 1%-4% of mild steel, that steel has great magnetic inductivity. If there is more Si content, then the welding performance gets decrease.

Tungsten

The tungsten combines with chromium or manganese to make high speed steel. It can increase the abrasion resistance. In M2 high speed steel, it has a lot of tungsten content.

Vanadium

Many steel has vanadium. And it increases the wear resistance and ductility.

Phosphorus

In general, phosphorus is a bad element for steel. It would increase the cold shortness and make the welding performance get worse. And also make plasticity be lower. So the phosphorus content usually is less than 0.045% in steel. By the way, the request for high-quality steel is more strict.

Sulfur

It also is a harmful element. It would make the ductility and toughness get lower. It would cause the cracks during the steel forging and rolling. And sulfur is bad for welding performance and reduce corrosion resistance. So the sulfur content is usually requested lower than 0.055%. And the high-quality steel is less than 0.040%. Adding 0.08% - 0.20% sulfur would make steel get better machinability. Many people call it free cutting steel.

Learn about steel chemical composition information to understand different chemical elements make different effects on the properties of steel.

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