The higher the carbon content, the higher the hardness of the steel, but its plasticity and toughness are poor.
Sulfur is a harmful impurity in steel. High sulfur content in steel, when subjected to high-temperature and high-pressure processing, makes it prone to brittleness, commonly referred to as hot brittleness.
Phosphorus can significantly reduce the plasticity and toughness of steel, especially at low temperatures. This phenomenon is known as cold brittleness. In high-quality steel, sulfur and phosphorus should be strictly controlled. However, from another perspective, in low-carbon steel, higher sulfur and phosphorus content can make it easier to machine, improving the steel’s machinability.
Manganese can improve the strength of steel, weaken or eliminate the adverse effects of sulfur, and enhance the hardenability of steel. High-alloy steel (high manganese steel) with a high manganese content exhibits good wear resistance and other physical properties.
Silicon can increase the hardness of steel, but it decreases plasticity and toughness. Electrical steel, containing a certain amount of silicon, can improve its soft magnetic properties.
Tungsten can enhance the red hardness and thermal strength of steel and improve its wear resistance.
Chromium can improve the hardenability and wear resistance of steel, as well as enhance its corrosion resistance and oxidation resistance.
Vanadium can refine the grain structure of steel, improving its strength, toughness, and wear resistance. When it is melted into austenite at high temperatures, it increases the hardenability of the steel. Conversely, when it exists in carbide form, it reduces hardenability.
Molybdenum can significantly enhance the hardenability and thermal strength of steel, prevent temper brittleness, and improve remanence and coercivity.
Titanium can refine the grain structure of steel, thereby improving the strength and toughness of steel. In stainless steel, titanium can eliminate or reduce intergranular corrosion.
Nickel can improve the strength and toughness of steel, enhance hardenability, and, at high content, significantly alter some physical properties of steel and alloys, improving the corrosion resistance of steel.
When steel contains a small amount of boron (0.001-0.005%), it multiplies the hardenability of the steel.
Aluminum can refine the grain structure of steel and inhibit the aging of low-carbon steel. It can also improve the oxidation resistance, wear resistance, and fatigue strength of steel by enhancing toughness at low temperatures.
Copper primarily enhances the atmospheric corrosion resistance of ordinary low-alloy steel, especially when used in combination with phosphorus.