What is Steel? – A Closer Look at Metallurgy’s Most Versatile Metal Alloy

Steel is an essential material that underpins much of modern society’s infrastructure and daily objects. But what exactly makes steel unique? This article will examine steel’s definition, composition, manufacturing process, properties, grading system and everyday usage to understand what sets this alloy apart.

Steel Defined

Steel is an alloy composed primarily of iron with added carbon and often other elements like manganese, chromium, nickel, and vanadium. The exact chemical makeup varies widely across production methods and required mechanical properties for end uses. In the most basic terms, steel takes elemental iron and alloys it with carbon and additional metals to achieve enhanced strength, durability, and corrosion resistance.

Steel Composition

Steel contains between 98-99% iron by weight. The added alloys constitute no more than 2% of steel’s chemical composition but have an outsized impact on its material properties. The carbon content in steel typically ranges between 0.2-2% by weight, with trace amounts of other metals. Specific combinations and ratios of alloying elements define the mechanical qualities of the final steel product.

Steel Manufacturing Process

All steel starts out as iron oxide ores which are smelted at high temperatures to produce pig iron, removing oxygen impurities in the iron ore. Pig iron contains over 90% iron along with carbon and silica. Further processing through lowering carbon content and removing silica impurities yields nearly pure iron. The molten iron is then mixed and melted with the desired alloying elements to produce crude steel. This metal alloy can then be cast and rolled into the required shapes, forms and final products.

Properties of Steel

The alloying process grants steel distinctive useful properties:

  • Strength – Varies across steel grades but is significantly stronger than pure iron. Allows construction of massive yet sturdy structures.
  • Durability – Withstands physical stresses, pressure, impact, temperature extremes, and environmental corrosion. Longer lasting than iron.
  • Malleability – Can be cast, rolled, pressed, machined into different forms. Allows for vast applications.
  • Thermal conductivity – Lower than pure iron but able to hold heat for tasks like cooking pans.
  • Magnetism – Loses the magnetic qualities of iron so it can be used in motors and generators.

Steel Grading System

Not all steel is created equal. There are thousands of different steel grades categorized into four types by the level of additional alloys:

  • Carbon steels – Contain only iron and carbon. Low, medium, high carbon variants.
  • Alloy steels – Have iron, carbon and additional elements. Tuned for strength, wear resistance, hardness.
  • Tool steels – Extreme hardness for cutting and machining applications.
  • Stainless steels – Include chromium for corrosion resistance. Most widely used steel.

Everyday Steel Usage

The versatility of steel has made it the most essential metal in everyday life. Primary uses include:

  • Construction – Buildings, bridges, railroads, stadiums, towers
  • Transportation – Automobiles, aircrafts, ships, trains, trucks
  • Infrastructure – Piping, power/telecom lines, turbines, water systems
  • Appliances – Refrigerators, washing machines, stoves, cookware
  • Consumer goods – Furniture, containers, packaging, tools, electronics

From skyscrapers to computers to cans of soup, steel is an indispensable material that enables modern daily life. Its unique composition and properties solidify steel as the backbone of infrastructure and manufacturing.


Steel is iron that has been alloyed with carbon and other elements to produce a harder, stronger, more versatile metal. Varying the components and production methods creates an exceptionally adaptable material that builds our manmade world. That’s what makes steel such a vital asset.