Page 310 - Chemical engineering design

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MATERIALS OF CONSTRUCTION
3. Corrosion resistance
4. Any special properties required; such as, thermal conductivity, electrical resistance,
magnetic properties
5. Ease of fabrication forming, welding, casting (see Table 7.1)
6. Availability in standard sizes plates, sections, tubes
7. Cost
Table 7.1. A guide to the fabrication properties of
common metals and alloys

Machining Cold working Hot working Casting Welding Annealing temp. ° C

Mild steel S S S D S 750
Low alloy steel S D S D S 750
Cast iron S U U S D/U
Stainless steel
(18Cr, 8Ni) S S S D S 1050
Nickel S S S S S 1150
Monel S S S S S 1100
Copper
(deoxidised) D S S S D 800
Brass S D S S S 700
Aluminium S S S D S 550
Dural S S S S 350
Lead S S
Titanium S S U U D
S Satisfactory, D Difficult, special techniques needed.
U Unsatisfactory.

7.3. MECHANICAL PROPERTIES
Typical values of the mechanical properties of the more common materials used in the
construction of chemical process equipment are given in Table 7.2.

7.3.1. Tensile strength
The tensile strength (tensile stress) is a measure of the basic strength of a material. It is
the maximum stress that the material will withstand, measured by a standard tensile test.
The older name for this property, which is more descriptive of the property, was Ultimate
Tensile Strength (UTS).
The design stress for a material, the value used in any design calculations, is based on
the tensile strength, or on the yield or proof stress (see Chapter 13).
Proof stress is the stress to cause a specified permanent extension, usually 0.1 per cent.

7.3.2. Stiffness
Stiffness is the ability to resist bending and buckling. It is a function of the elastic modulus of
the material and the shape of the cross-section of the member (the second moment of area).