Materials of Construction
Material properties are of great importance in all aspects of rotating
equipment design and manufacture. It is essential to check the up-to-date
version of the relevant British Standards or equivalent when choosing or
assessing a material. The most common materials used for rotating
equipment are divided into the generic categories of carbon, alloy, stainless
steel, and non-ferrous.
12.1 Plain carbon steels – basic data
Typical properties are shown in Table 12.1.
Table 12.1 Plain carbon steel: properties
Low C steel
General structural steel
12.2 Alloy steels – basic data
Alloy steels have various amounts of Ni, Cr, Mn, or Mo added to improve
properties. Typical properties are shown in Table 12.2.
Engineers’ Guide to Rotating Equipment
Table 12.2 Alloy steels: properties
12.3 Stainless steels – basic data
Stainless steel is a generic term used to describe a family of steel alloys
containing more than about 11 per cent chromium. The family consists of
four main classes, subdivided into about 100 grades and variants. The main
classes are austenitic and duplex. The other two classes, ferritic and
martensitic, tend to have more specialized application and so are not so
commonly found in general rotating equipment use. The basic
characteristics of each class are given below.
• Austenitic The most commonly used basic grades of stainless steel are
usually austenitic. They have 17–25 per cent Cr, combined with 8–20 per
cent Ni, Mn, and other trace alloying elements which encourage the
formation of austenite. They have low carbon content, which makes them
weldable. They have the highest general corrosion resistance of the family
of stainless steels.
• Ferritic Ferritic stainless steels have high