4 - Metals

Abstract

Metals are the most important materials of construction and are available in thousands of types (alloys), in various product forms, made to different quality levels. This chapter describes the metals commonly used in the chemical and hydrocarbon processing industries. It helps the specifier, procurer, receiver, and field user to understand how substitutions may occur and when to flag potential problems with serious consequences. Metals are distinguished from nonmetals by their strength, toughness, electrical conductivity, and thermal conductivity. However, the dominant property that causes metals to be preferred over most nonmetals is their ability to deform in the presence of excessive stress rather than fracture catastrophically. This is the prime reason for the widespread use of metals for structural applications such as plant equipment, piping, and pressure vessels. Alloying enhances mechanical properties, machinability, abrasion resistance, hardenability, corrosion resistance, and magnetic properties. Alloy steels are favored over carbon steels for demanding applications in components where significantly higher strength and hardness are required.