Final answer:
Modern thermal irons are made of fine steel because this material, produced by refining iron and adding specific elements, possesses properties like strength and hardness that are ideal for such applications, while avoiding brittleness from excess carbon.
Step-by-step explanation:
Modern thermal irons are commonly made of fine steel due to the enhanced properties that steel offers when compared to pure iron. This material is made from iron by removing impurities and adding various other elements to produce alloys that are tailored for specific applications. Elements such as manganese, chromium, nickel, tungsten, molybdenum, and vanadium are added to give steel its desirable properties like strength, durability, and resistance to corrosion.
Most steels contain a small but significant amount of carbon, which can range from 0.04% to 2.5%, which is critical in determining the steel's characteristics. For instance, mild steel, with up to about 0.25% carbon, is stronger and harder than pure iron, which is used for a variety of applications including construction and manufacturing. However, excessive carbon content would make the iron brittle, which is why it must be controlled during the steel-making process.