What is Alloy Steel ?

Alloy steel may be defined as steels to which elements other than carbon are added in sufficient amounts to produce improvements in properties. The most common alloying elements added to steel are chromium, nickel, manganese, silicon, vanadium, molybdenum, tungsten, phosphorus, copper, titanium, zirconium, cobalt, columbium, and aluminum. Each of these elements confers certain qualities upon the steels to which it is added. They may be used separately or in combination to produce desired characteristics in the steel.

Like carbon, a number of alloying elements are soluble to produce alloys with improved strength, ductility, and toughness. Also carbon besides forming an intermetallic compound with iron, combines with many alloying elements and form alloy carbides. These alloy carbides as well as iron-alloy carbides are usually hard and lack in toughness. Some alloying elements are added to prevent or restrict grain growth. Aluminum is considered the most effective in this respect. Others are zirconium, vanadium, chromium, and titanium. Structurally , the addition of alloying elements almost always affects the austenite-ferrite transformation mechanism by changing the temperature at which the transformation from gamma to alpha iron takes place. Some alloying elements lower and some raise the critical temperature.

The compositional and structural changes produced by alloying elements change and improve the physical, mechanical and processing properties of iron and steel. In general, alloy steels can give better strength, ductility, and toughness properties that cannot be obtained in carbon steel. Consequently, the production, the design engineer should consider alloy steels in designs subject to high stresses and or impact loading.

Almost all alloy steels are produced with fine - graded structures. Fine - graded steels have less tendency to crack during heat treatment but have better toughness and shock-resistance properties. Course - grained steels exhibit better machining properties and may be hardened more deeply than fine - grained steels.

Also see :

Effects of Alloying elements

classification Of Alloy Steels

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