Question

Question: Recent evidence indicates that the reason the Titanic sank so quickly was that the steel used in its hull was very brittle. Describe the roles of microstructure, carbon content, and impurities on the brittleness of steel. Further, arrange the following steels in descending order of their strength: martensite (M), Bainite (B), Coarse Pearlite (CP), Fine Pearlite (FP), and spheroidite (S).

Answer 1

The microstructure of steel can strongly influence physical properties such as brittleness .A microstructure’s influence on the mechanical and physical properties of a material is primarily governed by the different defects present or absent of the structure. These defects can take many forms but the primary ones are the pores. Even if those pores play a very important role in the definition of the characteristics of a material, so does its composition.Increasing carbon content increases hardness and strength and improves hardenability. But carbon also increases brittleness and reduces weldability because of its tendency to form martensite. Impurites increases the hardness and Tensile strength and brittleness of steel.

Order of strength:-

• spheroidite (S).>martensite (M)>Bainite(B)>Fine pearlite (FP)>Coarse pearlite (CP).