Why are pots so brittle, spoons so resilient, and knives so sharp? The pots, spoons used for cooking, and knives used for cutting vegetables are all made of iron. However, the iron used for these items differs significantly. The iron used for making pots is called cast iron. Its "temperament" is very brittle, and it breaks easily when tapped, so it cannot be directly used to make iron pots. In factories, cast iron is melted into molten iron and poured into molds for casting, so it is also called cast iron. The spoons used for cooking are made of wrought iron. Its "temperament" is quite different from that of cast ironāit is resilient rather than brittle. People often use large hammers to forge wrought iron into various shapes, which is why it is also called forged iron. However, knives used for cutting are not made of iron, but of steel. Steel has excellent resilience and ductility, allowing it to be forged, rolled, and cut into a variety of machines and tools.
Why do these three types of ironācast iron, wrought iron, and steelāhave such vastly different "temperaments"? The secret lies in the trace amounts of carbon in the iron. Cast iron has a high carbon content and is hard and brittle, making it difficult to forge into different shapes; wrought iron has a low carbon content and is quite resilient; while steel, with a carbon content between the two, has high hardness and excellent resilience and ductility. From a production perspective, iron from blast furnaces (also known as bellows furnaces or ironmaking furnaces) is cast iron; iron from reverberatory furnaces is wrought iron; and iron from steelmaking furnaces (converter furnaces or electric furnaces) is steel.