ISO 21028-2:2004

INTERNATIONAL ISO
STANDARD 21028-2
First edition
2004-04-15

Cryogenic vessels — Toughness
requirements for materials at cryogenic
temperature —
Part 2:
Temperatures between −−−− 80 °C
and −− 20 °C
−−
Récipients cryogéniques — Exigences de ténacité pour les matériaux à
température cryogénique —
Partie 2: Températures comprises entre − 80 °C et − 20 °C




Reference number
ISO 21028-2:2004(E)
©
ISO 2004

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ISO 21028-2:2004(E)
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ISO 21028-2:2004(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope. 1
2 Normative references. 1
3 Terms and definitions. 1
2
4 Requirements for steels with specified yield strength uuuu 460 N/mm . 2
5 General test requirements. 4
6 Welds. 5
7 Requirements for aluminium and aluminium alloys, copper and copper alloys and
austenitic stainless steels. 5
Annex A (informative) Case proposal — Technical justification for temperature adjustment term . 18
Bibliography . 21

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ISO 21028-2:2004(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 21028-2 was prepared by Technical Committee ISO/TC 220, Cryogenic vessels.
ISO 21028 consists of the following parts, under the general title Cryogenic vessels — Toughness
requirements for materials at cryogenic temperature:
 Part 1: Temperatures below − 80 °C
 Part 2: Temperatures between − 80 °C and − 20 °C
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ISO 21028-2:2004(E)
Introduction
The use of materials at low temperatures entails special problems which have to be addressed. Consideration
has to be given, in particular, to changes in mechanical characteristics, expansion and contraction
phenomena and the thermal conduction of the various materials. The most important property to be
considered is the material toughness at low temperature.
This part of ISO 21028 is based on European Standard EN 1252-2:2001.

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INTERNATIONAL STANDARD ISO 21028-2:2004(E)

Cryogenic vessels — Toughness requirements for materials at
cryogenic temperature —
Part 2:
Temperatures between −− 80 °C and −− 20 °C
−− −−
1 Scope
This part of ISO 21028 specifies the toughness requirements of metallic materials for use at temperatures
between − 20 °C and − 80 °C to ensure their suitability for cryogenic vessels. It is applicable to fine-grain and
2
low-alloyed steels with specified yield strength u 460 N/mm , aluminium and aluminium alloys, copper and
copper alloys and austenitic stainless steels.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 148 (all parts), Metallic materials — Charpy pendulum impact test
ISO 15614-1, Specification and qualification of welding procedures for metallic materials — Welding
1)
procedure test — Part 1: Arc and gas welding of steels and arc welding of nickel and nickel alloys
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
minimum metal temperature
T
M
lowest temperature defined for each of the conditions
 temperature during normal operation,
 temperature during start-up and shut down procedures,
 temperature which may occur during possible process upsets,
 temperature which may occur during pressure or leak testing, and
 ambient conditions
NOTE See also 3.2 and 3.3.

1) To be published.
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ISO 21028-2:2004(E)
3.2
temperature adjustment term
T
S
term relevant to the calculation of the design reference temperature T (3.3) and dependent on the
R
pressure-induced principal membrane stress at the appropriate minimum metal temperature
3.3
design reference temperature
T
R
temperature used for determining the impact energy requirements, themselves determined by adding the
temperature adjustment term T (3.2) to the minimum metal temperature T (3.1):
S M
TT=+T
RM S
NOTE All applicable combinations of the temperatures T and T are to be considered, and the lowest possible T
M S R
value used for the determination of the required material impact test temperature (3.4).
3.4
impact test temperature
T
KV
temperature at which the required impact energy has to be achieved
NOTE See Clause 5.
3.5
impact energy
KV
energy determined from Charpy V-notch tests performed in accordance with ISO 148.
3.6
reference thickness
e
B
thickness of a component used to relate the design reference temperature T (3.3) of the component with
R
its required impact test temperature T (3.4)
KV
See Figures 1 to 5.
NOTE The reference thickness is based on the nominal thickness (including corrosion allowance) and shall be as
defined in Table 6. For butt-welded components, it is the nominal wall thickness of the component at the edge of the weld
preparation
2
4 Requirements for steels with specified yield strength uu 460 N/mm
uu
4.1 General
This method, based on fracture mechanics, may be used to determine the requirements to avoid brittle
2
fracture in C, CMn, fine-grain and low-alloy steels with a specified minimum yield strength u 460 N/mm .
In this procedure, the impact test temperature T is not equal to the design reference temperature T .
KV R
Parent material, welds and HAZ shall meet the impact energy (KV) and impact test temperature T
KV
requirements given in Table 1 for design reference temperatures T and reference thicknesses. Values of T
R R
shall be calculated from T using the values of T given in 4.2.
M S
2
For materials with a specified minimum yield strength > 310 N/mm , the impact energy at T given in
KV
Figure 1 and Figure 2 shall be 40 J.
Where 27 J is specified in the product standard, Figure 3 for the post-weld heat-treated condition applies.
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ISO 21028-2:2004(E)
2 2
For the as-welded case with minimum yield strength in the range > 310 N/mm and u 360 N/mm , Figure 4
applies.
2
For minimum yield strength > 360 N/mm , Figure 5 applies.
Table 1 — Impact energy requirements
Required impact energy KV
Specified min. yield
(on 10 mm ×× 10 mm test Figure defining required T
××
KV
strength of base material
pieces)
Non-welded/
As-welded
2
N/mm J Post-weld heat-treated
(A-W)
(PWHT)
< 310 27 1 2
40 1 2
> 310, u 360
27 3 4
40 1 2
> 360
27 3 5
4.2 Temperature adjustments
T is a temperature adjustment which may be used if the pressure-induced principal membrane stress does
S
2
not exceed the percentage of the maximum allowable design stress or 50 N/mm given in Table 2.
Table 2 — Temperature adjustments
b
Percentage of maximum allowable design stress Membrane stress
Condition
2
>>>> 75 % ; uuuu 100 % uuuu 75 % uuuu 50 % uuuu 50 N/mm
Non-welded, post-weld heat
0 °C + 10 °C + 25 °C + 50 °C
a
treated
As-welded and reference
0 °C 0 °C 0 °C + 40 °C
thickness < 30 mm
a
Also applicable for equipment where all nozzles and non-temporary welded attachments are first welded to vessel components and
these sub-assemblies are post-weld heat-treated before being assembled into the equipment by butt-welding, but the main seams are
not subsequently post-weld heat-treated.
b
In this case, the membrane stress should take account of internal and external pressure and dead weight.
4.3 Procedure for base material <<<< 10 mm thick
Minimum T values are given in Table 3 which shall be used when the base material is less than 10 mm thick
R
and the testing temperature T is 20 °C. The impact energy requirements are as specified in the relevant
KV
materials standards.
If these materials are to be used below the T values given in Table 3, the testing shall be performed in
R
accordance with the relevant curve for 10 mm in Figure 1 to Figure 5. The required energies for the sub-sized
specimens are given in Table 4.
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ISO 21028-2:2004(E)
Table 3 — Minimum T values for base material <<<< 10 mm thick and T = 20 °C
S KV
As-welded Post-weld heat-treated
Thickness
(A-W) (PWHT)
mm °C
8 − 20 − 35
6 − 25 − 40
4 − 40 − 55
2 − 55 − 70
5 General test requirements
5.1 General
Where impact tests are required they shall be Charpy V-notched tests in accordance with ISO 148. The
impact energy requirements shall be met in the base material, heat-affected zone and weld metal. The
specimen position shall be in accordance with ISO 15614-1. From each sample three specimens shall be
tested for each of the required positions and test temperatures. The mean value of the three specimens shall
be at least equal to the impact energy requirement. Only one specimen may show a lower value, but this
value shall not be less than 70 % of this requirement.
The required values for base material refer to the transverse direction. If transverse properties are not
obtainable, the minimum impact energy requirements specified for transverse test pieces shall be multiplied
by a factor of 1,5 for C, CMn, fine-grained and low-alloyed steels with a minimum specified yield strength
2
u 460 N/mm . For other materials refer to the product standard.
5.2 Sub-sized specimens
If the base material is less than 10 mm thick the energy requirements shall be as given in Table 4.
Alternatively, where proportional reduced energy requirements are preferred, Table 5 shall be applied.
Table 4 — Impact requirements for sub-sized Charpy V-notched specimen if base material
<<<< 10 mm thick
Specimen geometry
mm × mm
10 × 10 10 × 7,5 10 × 5
27 J 22 J 19 J
40 J 32 J 28 J
5.3 Sub-sized specimens for components from which it is impossible to extract specimens
of section size equal to reference thickness
There are cases of unusually shaped components and/or weld procedure and production plates where the
Charpy V-notched specimen extracted is either < 10 mm or not representative of the section thickness.
In these cases sub-sized specimens shall be tested at lower impact test temperatures, in order to model the
behaviour of a full thickness specimen, using temperature shifts in accordance with Table 5.
Impact tests should be performed on the maximum thickness which can be extrac
...