EXPLANATION:PLAIN carbon steel is an alloy of iron and carbon.It has good machinability and malleability.It is different from cast iron as regards the PERCENTAGE of carbon.It contains carbon from 0.06 to 1.5% whereas cast iron possesses carbon from 1.8 to 4.2%.Depending upon the carbon content, plain carbon steel can be divided into the following types:DEAD carbon steel — up to 0.15% carbonLow carbon or mild steel — 0.15% to 0.45% carbonMedium carbon steel — 0.45% to 0.8% carbonHigh carbon steel — 0.8% to 1.5% carbon