Section 9 Stainless steel forgings
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules for the Manufacture, Testing and Certification of Materials, July 2022 - Chapter 5 Steel Forgings - Section 9 Stainless steel forgings

Section 9 Stainless steel forgings

Parent topic: Chapter 5 Steel Forgings

9.1 General

9.1.1 Forgings in austenitic and duplex stainless steels are acceptable for the construction of marine structures, machinery, pressure vessels and piping systems in ships. They may also be accepted for elevated temperature service in boilers. The allowable number and size of indications in the reference area are given in Table 5.2.3 Steel forgings surface inspection. This Table is also applicable to austenitic stainless steel and ferritic-austenitic (duplex) stainless steel forgings, for the purposes of assessing surface indications.

9.1.2 Austenitic stainless steel forgings are suitable for applications where the design temperature is not lower than -165°C.

9.1.3 Austenitic stainless steels are also suitable for service at elevated temperatures. Forgings for such applications are to comply with the requirement of Table 5.9.1 Chemical composition of stainless steel forgings and the requirement of Ch 5, 9.5 Mechanical properties for design purposes.

9.1.4 Duplex stainless steels forgings are suitable for applications where the design temperature is not lower than -20°C.

9.1.5 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.

9.1.6 Ultrasonic acceptance criteria detailed in Table 5.3.3 Acceptance criteria for ultrasonic testing of shafts and machinery components – DGS Method – Normal probes, Table 5.3.4 Acceptance criteria for ultrasonic testing of shafts and machinery components – DAC Method – Normal probes, Table 5.4.5 Ultrasonic acceptance criteria for crankshafts: DGS Method – Normal probes and Table 5.4.6 Ultrasonic acceptance criteria for crankshafts: DAC Method – Normal probes are intended for C, CMn, and alloy steel forgings, and do not apply to austenitic stainless steel or ferritic-austenitic (duplex) stainless steel forgings. Examples of standards for acceptance criteria for stainless steel or duplex stainless steel forgings are detailed below, and quality levels are to be agreed with the surveyor. Other National or International Standards may be used, upon agreement with the surveyor.

  • ASTM A745/A745M;
  • EN 10228-4.

9.2 Chemical composition

9.2.1 The chemical composition of ladle samples is to comply with the requirements given in Table 5.9.1 Chemical composition of stainless steel forgings.

9.2.2 Consideration will be given to the use of steels whose compositions are outside the scope of Table 5.9.1 Chemical composition of stainless steel forgings.

9.3 Heat treatment

9.3.1 All materials are to be supplied in the solution treated condition.

9.4 Mechanical tests

9.4.1 Tensile test specimens are to be taken in accordance with the appropriate requirements of Ch 5, 1.7 Mechanical tests.

9.4.2 The results of all tensile tests and impact tests are to comply with the requirements of Table 5.9.2 Mechanical properties for acceptance purposes: stainless steel forgings or the approved specification.

9.4.3 For austenitic stainless steel forgings, impact tests may be omitted subject to prior agreement with LR.

9.5 Mechanical properties for design purposes

9.5.1 Where austentic stainless steel forgings are intended for service at elevated temperatures, the nominal values for the minimum one per cent proof stress at temperatures of 100°C and higher given in Table 5.9.3 Mechanical properties for design purposes: austenitic stainless steels may be used for design purposes. Verification of these values is not required except for material complying with a National or proprietary specification in which the elevated temperature properties proposed for design purposes are higher than those given in Table 5.9.3 Mechanical properties for design purposes: austenitic stainless steels.

9.6 Non-Destructive Examination

9.6.1 Non-destructive examination is to be carried out in accordance with the requirements of the approved forging drawing and specification or as otherwise agreed between the manufacturer, purchaser and Surveyor.

9.7 Corrosion tests

9.7.1 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.

9.7.2 Where corrosive conditions are anticipated in service, for duplex stainless grades pitting corrosion tests are required in accordance with Ch 2, 9.2 Pitting corrosion test . Unless otherwise specified, the test temperatures shall be 20°C for S31803 and 30°C for S32750.

Table 5.9.1 Chemical composition of stainless steel forgings

Type of steel Chemical composition % (see Note)
C Si Mn S P Cr Mo Ni Others
Austenitic
304L 0,03 1,000 2,000 0,030 0,045 18,0–20,0 - 8,0–13,0 -
304 0,08 18,0–20,0 - 8,0–11,0 -
316L 0,03 16,0–18,0 2,0–3,0 10,0–15,0  
316 0,08 16,0–18,0 2,0–3,0 10,0–14,0  
317 0,08 18,0–20,0 3,0–4,0 11,0–15,0  
347 0,08 17,0–20,0 – 9,0–13,0 Nb >10xC ≤1,10
 
Duplex
UNS S 31803 0,03 1,00 2,00 0,020 0,030 21,0–23,0 2,5–3,5 4,5–6,5 N 0,08–0,20
UNS S 32750 0,03 0,80 1,20 0,020 0,035 24,0–26,0 3,0–5,0 6,0–8,0 N 0,24–0,32 Cu 0,50

Note Where a single value is shown (and not a range of values), the value is to be taken as maximum.

Table 5.9.2 Mechanical properties for acceptance purposes: stainless steel forgings

Type of steel Tensile strength N/mm2 minimum 1,0% proof stress N/mm2 minimum Elongation on 5,65 √So % minimum Reduction of area % minimum Charpy V-notch impact tests
Test temperature oC Average energy J
Austenitic
304L 485 170 30 50 –196 41
304 515 205
316L 485 170
316 515 205
317 515 205
347 515 205
Duplex
UNS S 31803 620 450 25 45 –20 (see Note) 41
UNS S 32750 800 550 15 40
Note Charpy V-notch impact tests are to be carried out at a temperature 5°C below design temperature or -20°C, whichever is lower.

Table 5.9.3 Mechanical properties for design purposes: austenitic stainless steels

Grade Nominal 1% proof stress (N/mm2) at a temperature of
100°C 150°C 200°C 250°C 300°C 350°C 400°C 450°C 500°C 550°C 600°C 650°C 700°C
304L 168 150 137 128 122 116 110 108 106 102 100 96 93
316L 177 161 149 139 133 127 123 119 115 112 110 107 105
316LN 238 208 192 180 172 166 161 157 152 149 144 142 138
321 192 180 172 164 158 152 148 144 140 138 135 130 124
347 204 192 182 172 166 162 159 157 155 153 151 — —
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