Section
8 Stainless steel castings
8.1 Scope
8.1.1 This Section gives the requirements for castings in austenitic and duplex
stainless steels for machinery, marine structures and piping systems in ships.
8.1.2 Austenitic stainless steels castings are suitable for applications where the
design temperature is not lower than –165°C.
8.1.3 Duplex stainless steels castings are suitable for applications where the
design temperature is not lower than -20°C.
8.1.4 Where it
is proposed to use alternative steels, particulars of the specified
chemical composition, mechanical properties and heat treatment are
to be submitted for approval.
8.2 Chemical composition
8.3 Heat treatment
8.3.1 Austenitic
stainless steel castings are to be solution treated at a temperature
of not less than 1000°C and cooled rapidly in water.
8.3.2 Duplex stainless
steels castings are to be solution treated at a temperature of not
less that 1100°C and cooled rapidly in water.
8.4 Mechanical tests
8.4.1 One tensile
test specimen is to be prepared from material representing each casting
or batch of castings. In addition, where the castings are intended
for liquefied gas applications, where the design temperature is lower
than −55°C, one set of three Charpy V-notch impact test
specimens is to be prepared.
Table 4.8.1 Chemical composition of stainless
steel castings
| Type of steel
|
Chemical composition %
|
| C
|
Si
|
Mn
|
S
|
P
|
Cr
|
Mo
|
Ni
|
Others
|
| Austenitic
|
| 304L
|
0,03
|
0,20-1,5
|
0,50-2,0
|
0,040
|
17,0-21,0
|
—
|
8,0–12,0
|
—
|
| 304
|
0,08
|
—
|
8,0–12,0
|
—
|
| 316L
|
0,03
|
2,0–3,0
|
9,0–13,0
|
—
|
| 316
|
0,08
|
2,0–3,0
|
9,0–13,0
|
—
|
| 317
|
0,08
|
3,0–4,0
|
9,0–12,0
|
—
|
| 347
|
0,06
|
—
|
9,0–12,0
|
Nb
≥ 8 x C
≤0,90
|
| (see
Note 1)
|
|
| Duplex
|
UNS J
92205
(see Note 3)
|
0,03
|
1,00
|
1,50
|
0,020
|
0,035
|
21,0–23,0
|
2,5–3,5
|
4,5–6,5
|
N
0,15–0,20
Cu
1,00
|
Note
1. When guaranteed impact values at low
temperature are not required, the maximum carbon content may be 0,08%
and the maximum niobium may be 1,00%.
Note
2. Where a single value is shown (and not
a range of values), the value is to be taken as maximum.
Note
3 The grade UNS J 92205 is the cast
equivalent of UNS S 31803.
|
Table 4.8.2 Mechanical properties for
acceptance purposes: stainless steel castings
| Type of steel
|
Tensile strength
N/mm2 minimum
|
1,0% proof stress
N/mm2 minimum
|
Elongation on 5,65 % minimum
|
Reduction of area %
minimum
|
Charpy V-notch impact test
|
| Test
temperature °C
|
Average
energy J minimum
|
| Austenitic
|
| 304L
|
430
|
215
|
26
|
40
|
–196
|
41
|
| 304
|
480
|
220
|
| 316L
|
430
|
215
|
26
|
40
|
–196
|
41
|
| 316
|
480
|
220
|
| 317
|
480
|
240
|
| 347
|
480
|
215
|
22
|
35
|
–196
|
41
|
| Duplex
|
| UNS J
92205 (see Note 1)
|
600
|
420
|
20
|
35
|
0
(see Note 2)
|
41
|
Note 1. The grade UNS J 92205 is the cast equivalent
of UNS S 31803.
Note 2. Charpy V-notch impact tests are to be carried out at a
temperature 5°C below design temperature or 0°C, whichever is
lower.
|
8.5 Corrosion tests
8.5.1 Where corrosive conditions are anticipated in service, for grades 304, 316
and 317, intergranular corrosion tests are required in accordance with Ch 2, 9.1 Intergranular corrosion test. Such tests may also be required for grades 304L, 316L
and 347.
8.5.2 Where corrosive conditions are anticipated in service, for duplex stainless
pitting corrosion tests are required in accordance with Ch 2, 9.2 Pitting corrosion test . For UNS J 92205 the test temperature is
to be 20°C.
8.6 Non-Destructive Examination
|