GB/T 20801.2-2020 PDF English
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Pressure piping code -- Industrial piping -- Part 2: Materials
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GB/T 20801.2-2020: PDF in English (GBT 20801.2-2020) GB/T 20801.2-2020
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 23.040
J 74
Replacing GB/T 20801.2-2006
Pressure piping code - Industrial piping - Part 2:
Materials
ISSUED ON: NOVEMBER 19, 2020
IMPLEMENTED ON: JUNE 01, 2021
Issued by: State Administration for Market Regulation;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Terms and definitions ... 9
4 General rules ... 11
5 Basic principles of material selection ... 13
6 Restrictions on the use of materials ... 13
7 Restrictions on the use of materials under high temperature conditions ... 21
8 Restrictions on the use of materials under low temperature conditions ... 24
9 Material marking and quality certification ... 34
Appendix A (Normative) Material designation and allowable stress ... 36
Appendix B (Informative) Physical properties of materials ... 72
Appendix C (Informative) Risk-based material design and selection ... 78
Appendix D (Informative) Comparison of material standards and designations
between China and foreign countries ... 113
References ... 124
Pressure piping code - Industrial piping - Part 2:
Materials
1 Scope
This Part of GB/T 20801 specifies the basic requirements for materials for
pressure piping components, including the selection of materials, restrictions
on use based on material properties, marking and quality certification.
This Part applies to the selection and use of materials, for pressure piping
components, which are defined in the scope of GB/T 20801.1.
2 Normative references
The following documents are essential to the application of this document. For
the dated documents, only the versions with the dates indicated are applicable
to this document; for the undated documents, only the latest version (including
all the amendments) is applicable to this standard.
GB/T 229 Metallic materials - Charpy pendulum impact test method
GB/T 1220 Stainless steel bars
GB/T 1348 Spheroidal graphite iron castings
GB/T 2882 Nickel and nickel alloys tube
GB/T 3077 Alloy structure steels
GB/T 3087 Seamless steel tubes for low and medium pressure boiler
GB/T 3091 Welded steel pipes for low pressure liquid delivery
GB/T 3098.1 Mechanical properties of fasteners - Bolts, screws and studs
GB/T 3098.6 Mechanical properties of fasteners - Stainless steel bolts,
screws and studs
GB/T 3624 Titanium and titanium alloy seamless tubes
GB/T 4334 Corrosion of metals and alloys - Test methods for intergranular
corrosion of stainless steels
The owner or designer shall select appropriate materials for piping components,
according to the specific use conditions (including manufacturing, fabrication
and installation, media, operating conditions, working environment, testing, etc.)
AND the material use requirements and restrictions specified in this Part,
considering the risk of material damage. This Part does not include material
requirements for welding, non-metal, etc.
4.2 Material and technical requirements
4.2.1 Table A.1 and Table A.2 of Appendix A specify the designations, allowable
stress and application range of the piping component materials. The materials,
which are used for the piping components, shall comply with the requirements
of the material standards, as listed in Table A.1 and Table A.2.
See Appendix B for the physical performance parameters of the material. Refer
to Appendix C, for the selection of commonly used pipeline materials, damage
risks, corresponding material design requirements, engineering measures.
4.2.2 In addition to the materials listed in Table A.1 and Table A.2, the following
materials can be used for piping components; however, they shall meet the
requirements and use restrictions for corresponding materials in this Part:
a) Other designations of materials, which are listed in the applicable material
standards for industrial piping, as listed in Table A.1 and Table A.2;
b) The material meets the published material standards, including chemical
composition, physical properties, mechanical properties, manufacturing
methods and processes, heat treatment and quality control, etc. It is not
lower than the requirements of the corresponding material standards,
which are listed in Table A.1 and Table A.2;
c) Standard applicable materials for piping components, which are listed in
Table 13 of GB/T 20801.3-2020;
d) The foreign standard materials, which are listed in Appendix D,
corresponding to the materials listed in Table A.1 and Table A.2.
4.2.3 Materials with unknown designations shall not be used for piping
components.
4.2.4 The recovered materials shall not be used in piping components.
4.2.5 The selection of other materials shall be subject to technical appraisal and
review & approval, by institutions with corresponding qualifications.
5 Basic principles of material selection
5.1 The materials, which are used for pressure components (except bolts), shall
have sufficient strength, plasticity, toughness. They shall have sufficient
resistance to brittle fracture, at the lowest use temperature. When brittle
materials, which have an elongation rate of less than 14%, are used, it shall
take necessary safety protection measures.
5.2 The selected materials shall have sufficient stability, including chemical
properties, physical properties, corrosion and wear resistance, fatigue
resistance, organizational stability.
5.3 When selecting materials, it shall consider the applicability of the materials
under possible open flames, fires and extinguishing conditions, as well as
changes in material properties and secondary hazards, which are brought
about by this.
5.4 The selected materials shall be suitable for the corresponding
manufacturing, production, installation, including welding, cold and hot
processing, heat treatment requirements.
5.5 When several different materials are used in combination, it shall consider
the possible adverse effects.
5.6 Materials shall be available and economical.
6 Restrictions on the use of materials
6.1 Nodular cast iron, gray cast iron, malleable cast iron
6.1.1 Nodular cast iron
6.1.1.1 When nodular cast iron is used for piping components, its elongation
shall not be less than 15%; the use temperature shall not be higher than 350 °C,
but it shall be higher than -20 °C. The use restrictions of nodular cast iron piping
components, which are listed in Table 13 of GB/T 20801.3-2020, shall comply
with the corresponding requirements of GB/T 13295.
6.1.1.2 Except for GC3 grade pipes, nodular cast iron shall meet the impact
performance requirements of GB/T 1348; the pressure rating shall not exceed
5.0 MPa.
6.1.1.3 Nodular cast iron shall not be used in severe cyclic conditions.
6.1.1.4 In addition to meeting the requirements of 6.1.1.1, 6.1.1.2, 6.1.1.3, the
applicable pressure-temperature ratings of nodular cast iron pipes, fittings,
accessories, pipe flanges, valves shall also comply with the requirements of the
corresponding standards, in Table 13 of GB/T 20801.3-2020.
6.1.1.5 Welding is not allowed, during manufacturing, production, installation.
6.1.2 Gray cast iron and malleable cast iron
6.1.2.1 When the gray cast iron and malleable cast iron, which are listed in
Table A.1, are used for piping components, they shall meet the following
requirements:
a) The use temperature of gray cast iron piping components shall not be
lower than -10 °C and not higher than 230 °C; the pressure rating shall
not be higher than 2.0 MPa;
b) The use temperature of malleable cast iron piping components shall not
be lower than -20 °C and not higher than 300 °C; the pressure rating shall
not be higher than 2.0 MPa;
c) Gray cast iron and malleable cast iron piping components shall not be
used for GC1 grade pipes or severe cyclic conditions;
d) When gray cast iron and malleable cast iron piping components are used
for GC2 grade pipelines, their use temperature shall not be higher than
150 °C; the maximum allowable working pressure shall not be greater than
1.0 MPa;
e) Safety protection measures shall be taken, to prevent overheating, rapid
cold and rapid heat, vibration, mis-operation;
f) No welding is allowed, during manufacturing, production, installation.
6.1.2.2 In addition to meeting the requirements of 6.1.2.1, the applicable
pressure-temperature ratings of gray cast iron and malleable cast iron pipes,
fittings, pipe flanges, valves shall also meet the requirements of the
corresponding standards, in Table 13 of GB/T 20801.3-2020.
6.2 Carbon structural steel
The restrictions on the use of carbon structural steel shall meet the following
requirements:
a) It shall not be used for GC1 grade piping components;
b) When using grade A killed steels, such as Q215A and Q235A, the design
pressure shall not be greater than 1.6 MPa; the design temperature shall
not be higher than 350 °C and not lower than the temperature as shown
6.6.1 Low-carbon (carbon content ≤ 0.08%) non-stabilized stainless steel (such
as 06Cr19Ni10, 06Cr17Ni12Mo2), in a non-solid solution state (including hot
working or welding after solid melting), should not be used in an environment,
where intergranular corrosion may occur. Please refer to Appendix C, for
material requirements.
6.6.2 Ultra-low carbon stainless steel has a tendency of intergranular corrosion,
when used for a long time above 425 °C. For material requirements, see
Appendix C.
6.6.3 For low-carbon/ultra-low-carbon austenitic stainless steels and other dual-
designation steels, its mechanical properties at room temperature shall meet
the higher value of the mechanical properties of the two designations; the
chemical composition shall meet the requirements of ultra-low-carbon grade. If
the use temperature is not higher than 538 °C, the allowable stress is selected
according to the low-carbon grade; if the use temperature is higher than 538 °C,
the allowable stress is selected according to the ultra-low carbon grade.
6.6.4 According to the requirements of the design documents, austenitic
stainless steel can be subjected to intergranular corrosion test, according to
GB/T 4334, OR stress corrosion test or pitting corrosion test, according to
relevant standards. The test method, specimen state, sampling ratio,
qualification index shall be defined in the design document.
6.7 Plate-welded pipe
6.7.1 Plate-welded pipes shall be formed by longitudinal coils of steel plates,
which have one or two longitudinal straight welds. Limited by the width of the
steel plate, plate-welded pipes of larger diameter can be formed by lateral
rolling the steel plates. Except for GB/T 3091 and SY/T 5037, the negative
deviation of the thickness of the plate-welded pipe shall not be greater than 0.3
mm; the size deviation of the plate-welded pipe shall be in accordance with the
relevant standards, such as GB/T 9711.
6.7.2 Steel pipes shall be manufactured by electrofusion welding process.
Except for GB/T 3091 and SY/T 5037, plate-welded pipes shall be of full
penetration structure. Carbon steel, pipeline steel, low-temperature carbon
steel, nickel steel, alloy steel shall be double-sided submerged arc welding or
gas shielded welding; stainless steel shall be double-sided gas shielded
welding, which is added with wire or not.
6.7.3 The chemical composition of the weld shall be close to or equivalent to
that of the base metal; its performance shall not be lower than that of the base
metal. The PSL2 plate-welded pipe in GB/T 9711 shall be subjected to an
impact test, which is not higher than the minimum design temperature AND not
lower than -30 °C. For steel pipes requiring impact tests, it shall include the
base metal, welds, heat-affected zone.
6.7.4 Except for the PSL2 plate-welded pipes in GB/T 9711, low-temperature
carbon steel plate-welded pipes, which require an impact test lower than or
equal to 0 °C, shall be normalized steel plates. Carbon steel and low-
temperature carbon steel plate-welded pipes, which have a thickness greater
than or equal to 20 mm, shall be subjected to post-weld stress relief heat
treatment. All chromium-molybdenum alloy steel plate-welded pipes shall be
subjected to post-weld stress relief heat treatment. Unless otherwise specified
by the owner or design, austenitic stainless steel and Duplex stainless steel
plate-welded pipes shall be solution-treated after welding.
6.7.5 Except for GC3 grade pipelines and the plate-welded pipes of GB/T 3091,
SY/T 5037, local or 100% radiographic or ultrasonic testing shall be carried out,
on the welds of plate-welded pipes; it shall comply with the corresponding
requirements in 6.3.2 of GB/T 20801.5-2020.
6.7.6 Welded pipes, which are used under severe cyclic conditions, shall adopt
a welding process with filler metal, AND be subject to local or 100%
radiographic or ultrasonic testing; it shall comply with the corresponding
requirements in 6.3.2 of GB/T 20801.5-2020.
6.8 Aluminum and aluminum alloy
6.8.1 The mechanical properties of aluminum and aluminum alloys are related
to thickness and delivery status. The properties and allowable stresses, which
are listed in Table A.1, are only applicable to the specified range of the
corresponding standards.
6.8.2 If the material standard does not specify the tensile and yield strength,
this Part requires supplementation in the purchase contract.
6.8.3 The welding structure of the material, in the work-hardened state, shall
adopt the allowable stress of the corresponding designation in the annealing
state; the welding structure of the material, in the precipitation hardened state,
shall adopt the allowable stress of the corresponding designation in the welding
state.
6.8.4 The performance and allowable stress of aluminum and aluminum alloy
pipe fittings are related to the blank, process and heat treatment state; it can
refer to the performance and allowable stress of seamless pipes, welded pipes,
plates, rods, forgings of the same designation. The performance and allowable
stress, which are listed in Table A.1, are typical examples.
6.9 Nickel and nickel alloys
6.9.1 The mechanical properties of nickel and nickel alloys are related to the
processing and heat treatment conditions. The properties and allowable
stresses, which are listed in Table A.1, are only applicable to the specified range
of the corresponding standards.
6.9.2 The performance and allowable stress of nickel and nickel alloy pipe
fittings are related to the blank, process, heat treatment state. It may refer to
the performance and allowable stress of seamless pipes, welded pipes, plates,
rods, forgings of the same designations. The performance and allowable stress,
which are listed in Table A.1, are typical examples.
6.9.3 The tensile strength of joints, which are welded by ENiCrMo-3 or
ERNiCrMo-3 of 625 nickel-based alloy, shall not be less than 758 MPa.
6.9.4 Thermal history of 625 nickel-based alloy, at 538 °C ~ 760 °C, may cause
the reduction of room temperature toughness and stress relaxation cracks, in
the welding area, see Appendix C.
6.10 Pipe support material
6.10.1 The standards, materials, allowable stresses, which are listed in Table
A.1 and Table A.2, also apply to pipe supports.
6.10.2 The other requirements of the pipe support material shall be in
accordance with the provisions of Chapter 8 of GB/T 20801.3-2020.
6.11 Low melting point metals
6.11.1 Low melting point metals, such as lead and zinc, as well as their alloys,
shall not be used in pipelines for conveying combustible media.
6.11.2 Low melting point metals, such as lead and zinc, shall be prevented from
liquid-metal corroding the austenitic stainless steel and nickel-based alloys,
during heat treatment, welding or high-temperature use. Refer to Appendix C.
7 Restrictions on the use of materials under high
temperature conditions
7.1 Upper limit of material's use temperature
7.1.1 Table A.1 and Table A.2 specify the upper limit of the material's use
temperature, under normal circumstances.
7.1.2 When determining the upper limit of the use temperature of the material,
it shall consider the influence of the medium and the environment.
7.2 Principles for the selection of high-temperature materials
7.2.1 General requirements
7.2.1.1 For materials, which are used for a long time under high temperature
conditions, it shall consider the influence of organization or performance
changes, on the reliability of the material.
7.2.1.2 For materials, which are used for a long time under high temperature
conditions, it shall consider the excessive deformation, excessive displacement,
deterioration of material structure and performance, stress relaxation of bolts,
due to creep. See Table 5 of the GB/T 20801.3-2020, for the creep threshold
temperature of typical metal materials. Other metal materials can be found in
Appendix C.
7.2.1.3 For materials, which are used under high temperature conditions, it shall
consider the material damage, which is caused by high temperature and
chemical corrosion.
7.2.1.4 For materials strengthened by heat treatment, if they are used at
temperatures close to or higher than the tempering temperature for a long
period of time, it shall consider the reduction in material strength.
7.2.2 The use of carbon steel and chromium-molybdenum alloy steel
under high temperature conditions
7.2.2.1 The high-temperature strength reduction factor W of welded joints,
under high-temperature creep conditions, is in accordance with the provisions
of 4.2.7 in GB/T 20801.3-2020.
7.2.2.2 Refer to Appendix C, for the high-temperature graphitization tendency
of carbon steel, carbon-manganese steel, low-temperature nickel steel, as well
as the softening (pearlite spheroidization) tendency of chromium-molybdenum
alloy steel.
7.2.2.3 Refer to Appendix C for the temper brittleness sensitivity of chromium-
molybdenum alloy steel.
7.2.3 The use of stainless steel under high temperature conditions
7.2.3.1 Under the high-temperature creep conditions (see 3.2 of GB/T 20801.3-
2020), the high-temperature strength reduction factor W of stainless steel
welded joints shall be in accordance with the provisions of 4.2.7 in GB/T
20801.3-2020.
7.2.3.2 Refer to Appendix C, for the brittleness sensitivity of ferritic stainless
steel, martensitic stainless steel, duplex stainless steel, at 475 °C.
7.2.3.3 Refer to Appendix C, for the σ-phase embrittlement sensitivity of
of carbon steel, low temperature steel, chromium-molybdenum alloy steel,
ferritic stainless steel, duplex stainless steel, shall meet the requirements of
Table 6 and Table A.1.
8.1.3.2 The welding procedure qualification of materials shall meet the
requirements of Table 8, Table 11, Table 12.
8.1.3.3 When carbon steel (including carbon-manganese steel) meets low-
temperature low-stress or low-temperature stress-reducing conditions, the
minimum use temperature for exemption from impact test may be lower than
that specified in 8.1.3.1, AND it shall meet the following requirements:
a) For the carbon steel (including carbon-manganese steel), that meets the
low-temperature stress-reducing conditions, the reduction of the minimum
use temperature, at which the material can be exempted from the impact
test, is 11 °C; meanwhile the minimum use temperature shall not be lower
than -30 °C, BUT shall meet the following requirements:
1) The pipeline shall undergo a hydraulic test, which is not less than 1.5
times the design pressure;
2) Except for the nominal wall thickness less than or equal to 13 mm, the
piping system shall be protected against external loads (such as
maintenance load, impact load, thermal shock load, etc.);
3) Low-temperature stress-reducing conditions are applicable to GC2
grade pipelines, as well as the GC3 grade pipelines in areas, where the
ambient temperature is not higher than -20 °C but not lower than -30 °C;
meanwhile, the applicable carbon steel materials do not contain carbon
structural steel and bolt materials; the existence of ferrite and austenite
dissimilar metal welded joints is not allowed in the piping system.
Note: The lowest ambient temperature is the lowest value of the monthly average
lowest temperature over the years.
b) For GC2 grade pipeline, which conforms to low-temperature low-stress
conditions, the minimum use temperature shall not be lower than -104 °C;
the applicable carbon steel materials do not contain carbon structural steel
and bolt materials; the existence of ferrite and austenite dissimilar metal
welded joints is not allowed in the piping system.
with thread diameter less than or equal to M52, which has the minimum
tensile strength of the material as specified in the standard, of less than
655 MPa, the impact test shall meet the requirements of Table 11;
b) For the notch of the bolt material with a thread diameter larger than M52
and the impact specimen of austenitic stainless steel, the lateral
expansion shall meet the requirements of Table 12.
9 Material marking and quality certification
9.1 Material marking
9.1.1 The marking of materials shall comply with the requirements of the
corresponding standards and contracts.
9.1.2 The content of the marking shall include at least the manufacturer's mark
and the name of the material (code). The marking of the following piping
components shall also include the furnace batch number or code of the material:
a) Piping components for GC1 grade pipelines;
b) The piping components subjected to the impact test according to the
requirements of this Part;
c) Chromium-molybdenum alloy steel (except bolt materials) piping
components;
d) Austenitic stainless steel (H-type) piping components used under high
temperature conditions;
e) Nickel and nickel alloy, titanium and titanium alloy piping components.
9.1.3 Materials shall be marked piece by piece. The markings shall be clear and
firm. Materials, which have a nominal diameter less than or equal to DN40, can
be marked with labels or other alternative methods.
9.2 Quality certification
The quality certification of the material shall meet the following requirements:
a) The materials shall have corresponding quality certification documents;
b) The quality certification documents shall include the standards and the
inspection and test results, which are specified in the contract; they shall
be traceable;
c) Quality certification documents (certificates), that do not include inspection
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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