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Microstructure of Steel

By Materials & Welding

 

 





 

ASM Heat Treating Society                

Microstructure of Steel

The solidification and as-cast microstructure of steel is a function of chemical composition and cooling rate.


For plain carbon and low alloy steels the solidification structure consists of austenite grains. However, during cooling to room temperature after solidification, a peritectic and then solid-state transformation occur that almost entirely conceal the original as-cast structure. For carbon steel, the austenite transforms into ferrite and pearlite if the composition is hypoeutectoid and into cementite and pearlite for hypereutectoid steel. Depending on cooling rate and composition, low-alloy steels can have various microstructures consisting of different forms and combinations of pearlite, bainite, martensite, cementite, and ferrite. High-alloy steels may have an austenite structure even after cooling to room temperature.

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