What is carbon steel, how to classify it, and weldability?

Carbon steel is an iron-carbon alloy with iron as the main component and carbon as the main alloying element. In the industrial field, especially low carbon steel is the most widely used. Carbon steel can be made into various plates, pipes and materials of various shapes, such as Angle steel, channel steel, I-steel, garden steel and flat steel.

According to the different carbon content, carbon steel can be divided into three categories:

Mild steel: the carbon content does not exceed 0.3%.

Medium carbon steel: carbon content of 0.3% to 0.6%.

High carbon steel: more than 0.6% carbon content.

In addition, according to the different quality, carbon steel can also be divided into two categories:

Ordinary carbon steel: contains more harmful impurities, such as sulfur and phosphorus.

High quality carbon steel: contains less harmful impurities.

According to different mechanical properties, carbon steel can be divided into three categories:

Class A steel (represented by A or A) : Mechanical strength is guaranteed only.

Class B steel (indicated by B or B) : Only the chemical composition is guaranteed.

Special steel (represented by inner or C) : both mechanical strength and chemical composition are guaranteed.

Here is some information about the weldability of carbon steel:

Low carbon steel has the best weldability, because of its good plasticity, generally no special treatment before and after welding.

The weldability of medium carbon steel is slightly worse, and for larger, thicker or more complex components, pre-welding and post-welding slow cooling treatment are needed to reduce stress and prevent cracks.

The weldability of high carbon steel is poor, mainly because of its strong rigidity and easy to produce cold cracks (that is, cracks that occur during the cooling process after welding).