Q.What are the differences between cast iron, wrought iron and steel ?

Step 1. Cast iron. Hard and brittle; contains about 4% carbon; used for making pipes, manufacturing automotive parts, pots, pans and utensils. Obtained by remelting, re-moulding and cooling pig iron.

Step 2. Wrought iron. Very soft; contains less than 0.2% carbon (the lowest of the three); used for making pipes, bars for stay bolts, engine bolts and rivets.

Step 3. Steel. Neither too hard nor too soft (intermediate between cast and wrought iron); contains between 0.2% and 2% carbon; used across buildings and infrastructure, tools, ships, automobiles and weapons -- by far the broadest range of applications of the three, reflecting its balanced mechanical properties.

Step 4. Underlying reason for the differences. All three are essentially the same base metal (iron) differing chiefly in CARBON CONTENT: carbon is trapped interstitially in the iron lattice (Section 8.6.7), and progressively more carbon makes the metal progressively harder and more brittle, which is why the softest form (wrought iron) has the least carbon and the hardest/most brittle form (cast iron) has the most.

Direct recall of the comparison table given at the end of Section 8.9.2, tied to the underlying carbon-content/interstitial-compound explanation from Section 8.6.7

• Reversing which form has the highest and lowest carbon content (cast iron has the MOST, not wrought iron).
• Listing only the carbon percentages without the corresponding hardness/application differences the question also asks for.