ISO 3845:2024 低炭素エネルギーを含む石油およびガス産業 | ページ 2

3.9

hydrogen-induced cracking

HIC

planar cracking that occurs in carbon and low alloy steels (3.12) when atomic hydrogen diffuses into the steel and then combines to form molecular hydrogen at trap sites

[SOURCE:ISO 15156-1:2020, 3.12, modified — Note 1 to entry has been removed.]

3.10

hydrogen permeation

process of atomic hydrogen diffusion through a metal

3.11

longitudinal weld

straight weld running along the longitudinal axis of a pipe

3.12

low alloy steel

steel with a total alloying element content of less than about 5 % mass fraction, but more than specified for carbon steel

[SOURCE:ISO 15156-1:2020, 3.15]

3.13

measured strain

ε₁, ε₂, ε₃

surface strain (3.24) as measured by various techniques in one or more of three known directions at the surface

3.14

microstructure

structure of a metal as revealed by microscopic examination of a suitably prepared specimen

[SOURCE:ISO 15156-1:2020, 3.16]

3.15

modulus of elasticity

Young’s modulus

E

ratio of tensile or compressive stress (3.26) to corresponding strain (3.24) below the elastic limit

3.16

plastic deformation

permanent deformation caused by straining beyond the elastic limit

3.17

Poisson’s ratio

v

dimensionless material constant (approximately constant for steel) given by the ratio of contraction/expansion per unit length tangential to the direction of loading over the expansion/contraction per unit length in the direction of loading

3.18

principal strain

ε_p

maximum and minimum strain (3.24) levels existing at a point on the test surface acting at 90° to each other as calculated from measured strain (3.13) values

3.19

residual stress

σ_res

stress (3.26) present in a component free of external forces or thermal gradients

[SOURCE:ISO 15156-1:2020, 3.18, modified — The symbol σ_res has been added.]

3.20

sour environment

environment where hydrogen sulfide exists in the presence of water

3.21

specific service

conditions of application for the materials/components for which testing is defined to match the customer’s requirements

Note 1 to entry: Fitness-for-purpose has also been historically used to define these same requirements.

3.22

specified minimum yield strength

SMYS

minimum yield strength (3.34) permitted for a given grade of material in product specifications

3.23

stepwise cracking

SWC

cracking that connects hydrogen-induced cracks on adjacent planes in a steel

Note 1 to entry: This term describes the crack appearance. The linking of hydrogen-induced cracks to produce stepwise cracking is dependent on the local strain (3.24) between the cracks and the embrittlement of the surrounding steel by dissolved hydrogen. HIC/SWC is usually associated with low-strength plate steels used in the production of pipes and vessels.

[SOURCE:ISO 15156-1:2020, 3.21]

3.24

strain

ε

dimensionless ratio of the change in length per unit length (e.g. mm/mm)

Note 1 to entry: It is normally expressed in parts per million ( × 10⁶) of microstrain (µε).

3.25

strain gauge

device using electrical resistance, which changes in proportion to applied strain (3.24)

3.26

stress

σ

applied force per unit area existing on any object as a result of external mechanical or thermal influences acting in that direction

3.27

stress-oriented hydrogen-induced cracking

SOHIC

staggered small cracks formed approximately perpendicular to the principal stress (3.26) (residual or applied) resulting in a “ladder-like” crack array linking (sometimes small) pre-existing HIC

Note 1 to entry: The mode of cracking can be categorized as SSC (3.28) caused by a combination of external stress and the local strain (3.24) around hydrogen-induced cracks. SOHIC is related to SSC and HIC/ SWC (3.23) . It has been observed in parent metal of longitudinally welded pipe and in the heat-affected zone (HAZ) (3.7) of welds in pressure vessels. SOHIC is a relatively uncommon phenomenon usually associated with low-strength ferritic pipe and pressure vessel steels.

[SOURCE:ISO 15156-1:2020, 3.23]

3.28

sulfide stress cracking

SSC

cracking of metal involving corrosion and tensile stress (3.29) (residual and/or applied) in the presence of water and H₂S

Note 1 to entry: SSC is a form of hydrogen stress cracking (HSC) and involves the embrittlement of the metal by atomic hydrogen that is produced by acid corrosion on the metal surface. Hydrogen uptake is promoted in the presence of sulfides. The atomic hydrogen can diffuse into the metal, reduce ductility, and increase susceptibility to cracking. High-strength metallic materials and hard weld zones are prone to SSC.

[SOURCE:ISO 15156-1:2020, 3.24]

3.29

tensile stress

ratio of load to original cross-sectional area

Note 1 to entry: These stresses include axial or longitudinal, circumferential or hoop and residual.

3.30

ultrasonic testing

testing of material by ultrasound for the presence of imperfections (3.3)

3.31

welding

joining of two metallic materials, usually by fusion techniques

3.32

weldment

portion of a component on which welding (3.31) has been performed, including the weld metal (3.33) , the heat-affected zone (HAZ) (3.7) , and the adjacent parent metal

[SOURCE:ISO 15156-2:2020, 3.24, modified — The abbreviated term for"heat-affected zone", HAZ, has been added.]

3.33

weld metal

portion of a weldment (3.32) that has been molten during welding (3.31)

3.34

yield strength

stress (3.26) at which a material exhibits a specified deviation from the proportionality of stress to strain (3.24)

Note 1 to entry: The deviation is expressed in terms of strain by either the offset method (usually at a strain of 0,2 %) or the total-extension-under-load method (usually at a strain of 0,5 %).