Section 6 Castings for boilers, pressure vessels and piping systems
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Clasifications Register Rules and Regulations - Rules for the Manufacture, Testing and Certification of Materials, July 2022 - Chapter 4 Steel Castings - Section 6 Castings for boilers, pressure vessels and piping systems

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.

6.1.3 Castings which comply with these requirements are acceptable for liquefied gas piping systems where the design temperature is not lower than 0°C. Where the design temperature is lower than 0°C, and for other applications where guaranteed impact properties at low temperatures are required, the castings are to comply with the requirements of Ch 4, 7 Ferritic steel castings for low temperature service or Ch 4, 8 Stainless steel castings.

6.2 Chemical composition

6.2.1 The chemical composition of ladle samples is to comply with the limits specified in Table 4.6.1 Chemical composition of steel castings for boilers, pressure vessels and piping systems.

6.3 Heat treatment

6.3.1 Castings are to be supplied:

  1. fully annealed; or

  2. normalised; or

  3. normalised and tempered; or

  4. quenched and tempered.

6.4 Mechanical tests

6.4.1 A tensile test is to be made on material representing each casting, unless a batch testing procedure has been agreed, see Ch 4, 1.6 Test material and test specimens.

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

6.5.1 The Non-Destructive Examination of castings is to be carried out in accordance with the appropriate requirements of Ch 4, 1.7 Visual and surface Non-Destructive Examination 1.7.7 to Ch 4, 1.7 Visual and surface Non-Destructive Examination 1.7.10 and Ch 4, 1.8 Volumetric Non-Destructive Examination 1.8.1 to Ch 4, 1.8 Volumetric Non-Destructive Examination 1.8.11, and additionally as agreed between the manufacturer, purchaser and Surveyor.

6.6 Mechanical properties for design purposes

6.6.1 Nominal values for the minimum lower yield or 0,2 per cent proof stress at temperatures of 100°C and higher are given in Table 4.6.3 Mechanical properties for design purposes (see 6.6.1) . These values are intended for design purposes only, and verification is not required except for materials complying with National or proprietary specifications where the elevated temperature properties used for design purposes are higher than those given in Table 4.6.3 Mechanical properties for design purposes (see 6.6.1) .

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

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