Classification of Metallic Engineering Materials

Abstract

Materials are classified under the three categories of (i) metals (ii) non-metals and composites. Of these, metals and its alloys broadly meet all requirements to be considered as the most suitable engineering material. Amongst metals, the largest use in the petrochemical industry is of ferrous metals and alloys like carbon and low alloy steels and stainless steels. Once selected, it is necessary to finalize the material specification as per requirement and adhere to the same for all procurements during construction and maintenance. Though limited to some specific services, non-ferrous metals and alloys are also used in petrochemical industry. In the first part of the chapter, a brief description and composition of the commonly used grades of carbon and alloy steels are given, followed by those of the conventional and high performance austenitic, ferritic and duplex stainless steels. Compositions of some important non-ferrous alloys have also been included. In the second part, the importance of standardization and material specification has been discussed which sets the requirements with regard to chemical analysis, mechanical properties heat treatment, dimensional tolerance, etc., that a product should satisfy. In a way, specification is considered as a contract between users and manufacturers.