Section
6 Castings for boilers, pressure vessels and piping systems
6.1 Scope
6.1.1 This Section
gives the requirements for carbon-manganese and alloy steel castings
for boilers, pressure vessels and piping systems for use at temperatures
not lower than 0°C.
6.1.2 Where it
is proposed to use alloy steels other than as given in this Section,
details of the specification are to be submitted for approval. In
such cases, the specified minimum tensile strength is not to exceed
600 N/mm2.
6.2 Chemical composition
6.3 Heat treatment
6.3.1 Castings
are to be supplied:
-
fully annealed; or
-
normalised; or
-
normalised and tempered;
or
-
quenched and tempered.
6.4 Mechanical tests
6.4.2 The tensile
test is to be carried out at ambient temperature, and unless agreed
otherwise with the Surveyor the results are to comply with the requirements
of Table 4.6.2 Mechanical properties for
acceptance purposes: steel castings for boilers, pressure vessels and piping
systems.
Table 4.6.1 Chemical composition of steel
castings for boilers, pressure vessels and piping systems
Type of steel
|
Chemical composition %
|
C max.
|
Si max.
|
Mn
|
S max.
|
P max.
|
Residual elements
|
Carbon-manganese
|
0,25
|
0,60
|
0,50-1,20
|
0,040
|
0,040
|
Cr
|
0,30 max.
|
Mo
|
0,15 max.
|
Cu
|
0,30 max.
|
Ni
|
0,40 max.
|
Total
|
0,80 max.
|
|
|
|
|
|
|
Cr
|
Mo
|
V
|
Residual elements
|
|
|
|
|
|
|
|
|
|
|
|
|
Cr
|
Cu
|
Ni
|
1/2 Mo
|
0,20
|
0,60
|
0,50–1,00
|
0,040
|
0,040
|
–
|
0,45-0,65
|
–
|
0,30
max.
|
0,30
max.
|
0,40
max.
|
1 Cr
1/2 Mo
|
0,20
|
0,60
|
0,50-0,80
|
0,040
|
0,040
|
1,00-1,50
|
0,45-0,65
|
–
|
–
|
0,30
max.
|
0,40
max.
|
2
1/4 Cr1 Mo
|
0,18
|
0,60
|
0,40-0,70
|
0,040
|
0,040
|
2,00-2,75
|
0,90-1,20
|
–
|
–
|
0,30
max.
|
0,40
max.
|
1/2 Cr 1/2 Mo
1/4 V
|
0,10–0,15
|
0,45
|
0,40-0,70
|
0,030
|
0,030
|
0,30-0,50
|
0,40-0,60
|
0,22-0,30
|
–
|
0,30
max.
|
0,30
max.
|
Table 4.6.2 Mechanical properties for
acceptance purposes: steel castings for boilers, pressure vessels and piping
systems
Type of
steel
|
Yield
stress minimum N/mm2
|
Tensile strength N/mm2
|
Elongation on 5,65 % minimum
|
Reduction of area % minimum
|
Carbon-manganese
|
275
|
485-655
|
22
|
25
|
1/2 Mo
|
260
|
460-590
|
18
|
30
|
1 Cr
1/2 Mo
|
280
|
480-630
|
17
|
20
|
2
1/4 Cr1 Mo
|
325
|
540-630
|
17
|
20
|
1/2 Cr 1/2 Mo
1/4 V
|
295
|
510-660
|
17
|
20
|
Table 4.6.3 Mechanical properties for design
purposes (see 6.6.1)
Type of steel
|
Nominal minimum lower yield or 0,2% proof stress N/mm2
|
Temperature °C
|
100
|
150
|
200
|
250
|
300
|
350
|
400
|
450
|
500
|
550
|
600
|
Carbon-manganese
|
225
|
214
|
201
|
186
|
163
|
156
|
152
|
–
|
–
|
–
|
–
|
1/2 Mo
|
242
|
236
|
226
|
207
|
186
|
175
|
169
|
158
|
145
|
136
|
126
|
1 Cr
1/2 Mo
|
240
|
–
|
212
|
–
|
196
|
–
|
184
|
–
|
160
|
–
|
117
|
2
1/4 Cr1 Mo
|
323
|
312
|
305
|
296
|
290
|
280
|
273
|
258
|
240
|
211
|
180
|
1/2 Cr 1/2 Mo
1/4 V
|
264
|
–
|
244
|
–
|
230
|
–
|
214
|
–
|
194
|
–
|
144
|
6.4.3 Where it
is proposed to use a carbon-manganese steel with a specified minimum
tensile strength intermediate to those given in this Section, corresponding
minimum values for the yield stress, elongation and reduction of area
may be obtained by interpolation.
6.4.4 Carbon-manganese
steels with a specified minimum tensile strength of greater than 490
N/mm2, but not exceeding 520 N/mm2, may be accepted
provided that details of the proposed specification are submitted
for approval.
6.5 Non-Destructive Examination
6.6 Mechanical properties for design purposes
6.6.2 In such cases,
at least one tensile test at the proposed design or other agreed temperature
is to be made on each casting or each batch of castings. The test
specimen is to be taken from material adjacent to that used for tests
at ambient temperature, and the test procedure is to be in accordance
with the requirements of Ch 2 Testing Procedures for Metallic Materials. The
results of all tests are to comply with the requirements of the National
or proprietary specification.
6.6.3 Values for
the estimated average stress to rupture in 100 000 hours are given
in Table 4.6.4 Mechanical properties for design
purposes (see 6.6.3): estimated average stresses to rupture in 100,000 hours
(N/mm2 ) and may be used
for design purposes.
Table 4.6.4 Mechanical properties for design
purposes (see 6.6.3): estimated average stresses to rupture in 100,000 hours
(N/mm2 )
Temperature °C
|
Type of steel
|
½Mo
|
1Cr½Mo
|
2¼Cr1Mo
|
½Cr½Mo¼V
|
430
|
308
|
–
|
–
|
–
|
440
|
276
|
–
|
–
|
–
|
450
|
245
|
–
|
222
|
277
|
460
|
212
|
–
|
199
|
237
|
470
|
174
|
236
|
177
|
206
|
|
|
|
|
|
480
|
133
|
186
|
156
|
181
|
490
|
103
|
148
|
139
|
159
|
500
|
84
|
120
|
124
|
140
|
510
|
71
|
100
|
111
|
124
|
520
|
60
|
84
|
99
|
109
|
|
|
|
|
|
530
|
–
|
70
|
–
|
96
|
540
|
–
|
58
|
–
|
85
|
550
|
–
|
–
|
–
|
75
|
560
|
–
|
–
|
–
|
66
|
|