What is the difference between low-carbon steel and high-carbon steel?

Low-carbon steel has ≤0.2 percent carbon, can be easily welded, but cannot be hardened.

High-carbon steel has 0.7-2 percent carbon, can be hardened, but cannot be easily welded. Welding results in a change in the structure of the material and redistribution of the carbon and thus affects the strength of steel adversely.