Page 322 - Chemical engineering design

Commonly used grades of austenitic stainless steel
Composition per cent
Specification no. Table 7.7. MATERIALS OF CONSTRUCTION 297
C Si Mn Cr Ni Mo Ti Nb
BS 1501 AISI max max max range range range
801B 304 0.08 2.00 17.5 8.0
20.0 11.0
810 C 304 ELC 0.03 1.00 2.00 17.5 10 min
20.0
801 Ti 321 0.12 1.00 2.00 17.0 7.5 min 4 ð C
20.0
801 Nb 347 0.08 1.00 2.00 17.0 9 min 10 ð C
20.0
821 Ti 0.12 1.00 2.00 17.0 25 min 4 ð C
20.0
845 B 316 0.08 1.00 2.00 16.5 10 min 2.25
18.5 3.00
845 Ti 0.08 0.06 2.00 16.5 10 min 2.25 4 ð C
18.5 3.00
846 0.08 1.00 2.00 18.0 11.0 3.0
20.0 14.0 4.0
S and P 0.045 per cent all grades.
AISI American Iron and Steel Institute.

Table 7.8. Comparative strength of stainless steel
Temperature ° C 300 400 500 600
Typical design mild steel 77 62 31
stress N/mm 2
stainless
18/8 108 100 92 62

Mechanical properties

The austenitic stainless steels have greater strength than the plain carbon steels, particu-
larly at elevated temperatures (see Table 7.8).
As was mentioned in Section 7.3.7, the austenitic stainless steels, unlike the plain
carbon steels, do not become brittle at low temperatures. It should be noted that the
thermal conductivity of stainless steel is significantly lower than that of mild steel.
Ž
Ž
Typical at 100 C values are, type 304 (18/8) 16 W/m C
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mild steel 60 W/m C
Austenitic stainless steels are non-magnetic in the annealed condition.
General corrosion resistance
The higher the alloying content, the better the corrosion resistance over a wide range of
conditions, strongly oxidising to reducing, but the higher the cost. A ranking in order of