6.2 Material requirements
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Statutory Documents - IMO Publications and Documents - International Codes - 1983 IGC Code - International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk - Chapter 6 Materials of Construction - 6.2 Material requirements

6.2 Material requirements

 The requirements for materials of construction are shown in the tables as follows

Table 1 : Plates, pipes (seamless and welded), sections and forgings for cargo tanks and process pressure vessels for design temperatures not lower than 0°C.
Table 2 : Plates, sections and forgings for cargo tanks, secondary barriers and process pressure vessels for design temperatures below 0°C and down to -55°C.
Table 3 : Plates, sections and forgings for cargo tanks, secondary barriers and process pressure vessels for design temperatures below -55°C and down to -165°C.
Table 4 : Pipes (seamless and welded), forgings and castings for cargo and process piping for design temperatures below 0°C and down to -165°C.
Table 5 : Plates and sections for hull structures required by 4.9.1 and 4.9.4.

Fig. 6.1 Orientation of weld test specimen

Table 6.1

PLATES, PIPES (SEAMLESS AND WELDED)1, SECTIONS AND FORGINGS FOR CARGO TANKS
AND PROCESS PRESSURE VESSELS FOR DESIGN TEMPERATURES NOT LOWER THAN 0°C
CHEMICAL COMPOSITION AND HEATTREATMENT CARBON-MANGANESE STEEL   Fully killed
Fine grain steel where thickness exceeds 20 mm    
Small additions of alloying elements by agreement with the Administration  
Composition limits to be approved by the Administration  
Normalized, or quenched and tempered2    
TENSILE AND TOUGHNESS (IMPACT) TEST REQUIREMENTS
PLATES Each “piece” to be tested  
SECTIONS AND FORGINGS Batch test  
TENSILE PROPERTIES Specified minimum yield stress not to exceed 410 N/mm3  
CHARPY V-NOTCH TEST      
PLATES Transverse test pieces. Minimum average energy value (E) 27 J  
SECTIONS AND FORGINGS Longitudinal test pieces. Minimum average energy value (E) 41 J  
TEST TEMPERATURE: Thickness t (mm) Test temperature (°C)  
  t ≤ 20 0  
  20 < t ≤ 40 -20  

1 For seamless pipes and fittings normal practice applies. The use of longitudinally and spirally welded pipes should be specially approved by the Administration.

2 A controlled rolling procedure may be used as an alternative to normalizing or quenching and tempering, subject to special approval by the Administration.

3 Materials with specified minimum yield stress exceeding 410 N/mm2 may be specially approved by the Administration. For these materials, particular attention should be given to the hardness of the weld and heat affected zone.

Table 6.2

PLATES, SECTIONS AND FORGINGS1 FOR CARGO TANKS, SECONDARY BARRIERS AND PROCESS PRESSURE VESSELS FOR DESIGN TEMPERATURES -0°C AND DOWN TO -55°C
Maximum thickness 25 mm2
CHEMICAL COMPOSITION AND HEAT TREATMENT
Carbon-manganese steel Fully killed Aluminium treated fine grain steel
Chemical composition (ladle analysis)
C
0.16% max.3 		Mn
0.70 - 1.60% 		Si
0.10 - 0.50% 		S
0.035% max. 		P
0.035% max. 		 
Optional additions: Alloys and grain refining elements may be generally in accordance with the following:
Ni
0.80% max. 		Cr
0.25% max. 		Mo
0.08% max. 		Cu
0.35% max. 		Nb
0.05% max. 		V
0.10% max.
Normalized or quenched and tempered4
TENSILE AND TOUGHNESS (IMPACT) TEST REQUIREMENTS
PLATES Each "piece' to be tested
SECTIONS Batch test
CHARPY V-NOTCH TEST Test temperatures 5°C below the design temperature or -20°C whichever is lower
PLATES Transverse test pieces. Minimum average energy value (E) 27J
SECTIONS AND FORGINGS1 Longitudinal test pieces. Minimum average energy value (E) 41J

1 The Charpy V-notch and chemistry requirements for forgings may be specially considered by the Administration.

2 For material thickness of more than 25 mm, Charpy V-notch tests should be conducted as follows:

Material thickness (mm) Test temperature (°C)
25 < t ≤ 30 10° below design temperature or -20° whichever is lower
30 < t ≤ 35 15° below design temperature or -20° whichever is lower
35 < t ≤ 40 20° below design temperature

The impact energy value should be in accordance with the table for the applicable type of test specimen. For material thickness of more than 40 mm, the Charpy V-notch values should be specially considered.Materials for tanks and parts of tanks which are completely thermally stress relieved after welding may be tested at a temperature 5°C below design temperature or -20°C whichever is lower.For thermally stress relieved reinforcements and other fittings, the test temperature should be the same as that required for the adjacent tank-shell thickness.

3 By special agreement with the Administration, the carbon content may be increased to 0.18% maximum provided the design temperature is not lower than -40°C.

4 A controlled rolling procedure may be used as an alternative to normalizing or quenching and tempering, subject to special approval by the Administration.
Guidance:For materials exceeding 25 mm in thickness for which the test temperature is -60°C or lower, the application of specially treated steels or steels in accordance with table 6.3 may be necessary.

Table 6.3

PLATES, SECTIONS AND FORGINGS1 FOR CARGO TANKS, SECONDARY BARRIERS AND PROCESS PRESSURE VESSELS FOR DESIGN TEMPERATURES BELOW -55°C AND DOWN TO -165°C2
Maximum thickness 25 mm3
Minimum design temp. (°C) Chemical composition4 and heat treatment Impact test temp. (°C)
-60 1.5% nickel steel - normalized -65
-65 2.25% nickel steel - normalized or normalized and tempered5 -70
-90 3.5% nickel steel - normalized or normalized and tempered5 -95
-105 5% nickel steel - normalized or normalized and tempered5, 6 -110
-165 9% nickel steel - double normalized and tempered or quenched and tempered -196
-165 Austenitic steels, such as types 304, 304L, 316, 316L, 321 and 347 solution treated7 -196
-165 Aluminium alloys; such as type 5083 annealed Not required
-165 Austenitic Fe-Ni alloy (36% nickel) Heat treatment as agreed Not required
TENSILE AND TOUGHNESS (IMPACT) TEST REQUIREMENTS
PLATES Each "piece" to be tested
SECTIONS AND FORGINGS Batch test
CHARPY V-NOTCH TEST  
PLATES Transverse test pieces. Minimum average energy value (E) 27J
SECTIONS AND FORGINGS Longitudinal test pieces. Minimum average energy value (E) 41J

1The impact test required for forgings used in critical applications should be subject to special consideration by the Administration.

2 The requirements for design temperatures below -165°C should be specially agreed with the Adminstration.

3 For materials 1.5% Ni, 2.25% Ni, 3.5% Ni and 5% Ni, with thickness greater than 25 mm, the impact tests should be conducted as follows:

  Material thickness (mm) Test temperature (°C)
  25 < t ≤ 30 10° below design temperautre
  30 < t ≤ 35 15° below design temperautre
  35 < t ≤ 40 20° below design temperautre
NOTES

In no case should the test temperature be above that indicated in the table.The energy value should be in accordance with the table for the application type of test specimen. For material thickness of more than 40 mm, the Charpy V-notch values should be specially considered.For 9% Ni, austenitic stainless steels and aluminium alloys, thicknesses greater than 25 mm may be used at the discretion of the Administration.

4 The chemical composition limits should be approved by the Administration.

5 A lower minimum design temperature for quenched and tempered steels may be specially agreed with the Administration.

6 A specially heat treated 5% nickel steel, for example triple heat treated 5% nickel steel, may be used down to -150°C upon special agreement with the Administration, provided that the impact tests are carried out at -196°C

7 The impact test may be omitted subject to agreement with the Administration.

Table 6.4

PIPES (SEAMLESS AND WELDED1), FORGINGS2 AND CASTINGS2 FOR CARGO
AND PROCESS PIPING FOR DESIGN TEMPERATURES
BELOW 0°C AND DOWN TO -165°C
Maximum thickness 25 mm
Minimum design temp. (°C) Chemical composition 5 and heat treatment Impact test
Test temp. (°C) Minimum average energy (E) (J)
-55 Carbon-manganese steel. Fully killed fine grain. Normalized or as agreed 6 4 27
-65 2.25% nickel steel. Normalized or normalized and tempered 6 -70 34
-90 3.5% nickel steel - normalized or normalized and tempered 6 -95 34
-165 9% nickel steel 7. Double normalized and tempered or quenched and tempered -196 41
Austenitic steels, such as types 304, 304L, 316, 316L, 321 and 347 solution treated8 -196 41
Aluminium alloys; such as type 5083 annealed   Not required
TENSILE AND TOUGHNESS (IMPACT) TEST REQUIREMENTS
Each batch to be tested
Impact test – Longitudinal test pieces
NOTES

1 The use of longitudinally or spirally welded pipes should be specially approved by the Administration.

2 The requirements for forgings and castings may be subject to special consideration by the Administration.

3 The requirements for design temperatures below -165°C should be specially agreed with the Administration.

4 The test temperature should be 5°C below the design temperature or -20°C whichever is lower.

5 The composition limits should be approved by the Administration.

6 A lower design temperature may be specially agreed with the Administration for quenched and tempered materials.

7 This chemical composition is not suitable for castings.

8 Impact tests may be omitted subject to agreement with the Administration.

Table 6.5

PLATES AND SECTIONS FOR HULL STRUCTURES
REQUIRED BY 4.9.1 AND 4.9.4
Minimum design temperature of hull structure (°C) Maximum thickness (mm) for steel grades in accordance with 6.1.9
A B D E AH DH EH
0 and above1 Normal practice
-5 and above2
-5 and below 0 15 25 30 50 25 45 50
-10 and below -5 X 20 25 50 20 40 50
-20 and below -10 X X 20 50 X 30 50
-30 and below -20 X X X 40 X 20 40
Below -30 In accordance with table 6.2 except that the thickness limitation given in table 6.2 and in 2 of that table does not apply.
NOTES

“X” means steel grade not to be used.

1 For the purpose of 4.9.4.

2 For the purpose of 4.9.1.

Parent topic: Chapter 6 Materials of Construction
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