What grade is mild steel plate？

Mild carbon steel is a low carbon steel with relatively low strength and hardness compared to other types of steel.

Carbon steel plates are available in a variety of grades, with each grade having different characteristics and applications. Some common grades of carbon steel plates include ASTM A36, ASTM A572, and ASTM A516. The specific grade chosen depends on factors such as the required strength, hardness, and corrosion resistance for a given application.

Here's a table that includes some common grades of low-carbon steel, medium carbon steel, and high carbon steel, along with their approximate carbon content percentages:

Note that the carbon content percentages are approximate and may vary depending on the specific grade and standard.