Alloying Elements of Steel
As we know, steel is an alloy of element of which the base is normally iron. Many different elements and components are added to steel in order to change the properties of the steel.
The effect of adding Chromium to steel gives it a corrosion resistance, and as such Chromium can be found in high quantities in stainless steel. In fact, grade of stainless steel are actually defined by their chromium content. The chromium actually creates a surface on the steel which prevents the steel from oxidising. Other effects of adding chromium include reducing the machinability of the alloy and increasing its strength.
Alloying molybdenum also increases the corrosion resistance, as well as being capable of increasing the hardeness, toughness and Tensile Strength. Molybdenum can also increase the resistance to chlorides and reduce pitting.
Vanadium affects the grain structure of the steel. By reducing the grain structure of the steel, it can be help to increase the ductility, the carbides can also increase hardness and strength
Manganese can improve the ability to heat treat the steel, it achieves this by allowing a slower quench.
Nickel combined with chromium makes good austenitic steel
Copper is a often a residual element but can increase corrosion resistance in seawater or sulfuric acid
Sulphur and Phosphor
Sulphur and Phosphor can improve machinability, However tend to have a detrimental effect on corrosion resistance.
Cobalt can become radioactive when exposed to radioactive isotopes. And as Cobalt can be a residueal metal in steel, nuclear grade steels sometimes have limits on cobalt content, typically <0.2%.
Small amounts of Calcium can improve machinability without the effects on other properties that Sulphur and Phosphor can have.