Mild steel

Mild Steel is a steel with carbon content from about 0.05 up to 2.1 percent by weight. 

no minimum content is specified or required for chromium, cobalt, molybdenum, nickel, niobium, titanium, tungsten, vanadium, zirconium, or any other element to be added to obtain a desired alloying effect;

the specified minimum for copper does not exceed 0.40%;

or the maximum content specified for any of the following elements does not exceed the percentages noted: manganese 1.65 per cent; silicon 0.60 per cent; copper 0.60 per cent.