This document provides an overview of stress corrosion cracking (SCC) in pipeline steels. It discusses two main forms of SCC that can occur in pipelines - intergranular SCC (IGSCC) and transgranular SCC (TGSCC). IGSCC typically occurs in concentrated carbonate/bicarbonate solutions with a pH of around 9 and results in intergranular cracks. TGSCC occurs in more dilute solutions with a pH around 6.5 and produces transgranular cracks. The document also examines the factors that influence SCC, including environmental conditions, metallurgical factors like microstructure, and mechanical stresses in the pipe. Surface roughness from grit blasting is identified as a factor that can
Explosive Forming is a manufacturing technique that uses explosions to force metal into dies and molds.
The explosives are typically either detonated underwater or in direct contact with the materials.
The technique is useful for short production runs of conventionally difficult-to-manufacture parts.
In Explosive Forming a punch or diaphragm in conventional forming is replaced by an explosive charge.
Chemical energy from the explosives is used to generate shockwaves through a medium (mostly water), which are directed to deform the workpiece at very high velocities.
Explosive Forming is a manufacturing technique that uses explosions to force metal into dies and molds.
The explosives are typically either detonated underwater or in direct contact with the materials.
The technique is useful for short production runs of conventionally difficult-to-manufacture parts.
In Explosive Forming a punch or diaphragm in conventional forming is replaced by an explosive charge.
Chemical energy from the explosives is used to generate shockwaves through a medium (mostly water), which are directed to deform the workpiece at very high velocities.
Electrochemical Machining (ECM) has established itself as one of the major alternatives to conventional methods of machining difficult - to - cut materials of and generating complex contours, without inducing residual stress and tool wear.
This seminar is devoted to the study of influences of variable ECM parameters like applied voltage and feed rate keeping other parameters constant on the surface roughness (Ra) using Response Surface Methodology (RSM).
what is laser hardening
process of laser hardening
hardening of cast iron
process variables
differences with other conventional process
advantages and disadvantages
CED Coating Service is surely the best option for coating. In our PPT, we have described the Process of CED Coating and advantages of using CED Coating for metal components
For more information visit us at : http://www.techedgeco.in
Introduction to casting, Major classifications of casting, Casting terminology, Characteristics of molding sand, Constituents of foundry sand, Patterns and their types, Cores and types of cores, Gating system, Types of gates, Solidification, Riser system, Types of riser, Types of allowances, Directional Solidification, Defects in casting, Riser design(Chvorinov's rules), Advanced casting techniques:Shell molding, Permanent mould casting, Vacuum die casting, Low pressure die casting, Continuous casting, Squeeze casting, Slush casting, Vacuum casting, Die Casting, Centrifugal casting, Investment casting
This Presentation covers the basic concepts of Hot cracks and cold cracks in welding. For more information, please refer the books mentioned in the references slide.... Thank you
Electrochemical Machining (ECM) has established itself as one of the major alternatives to conventional methods of machining difficult - to - cut materials of and generating complex contours, without inducing residual stress and tool wear.
This seminar is devoted to the study of influences of variable ECM parameters like applied voltage and feed rate keeping other parameters constant on the surface roughness (Ra) using Response Surface Methodology (RSM).
what is laser hardening
process of laser hardening
hardening of cast iron
process variables
differences with other conventional process
advantages and disadvantages
CED Coating Service is surely the best option for coating. In our PPT, we have described the Process of CED Coating and advantages of using CED Coating for metal components
For more information visit us at : http://www.techedgeco.in
Introduction to casting, Major classifications of casting, Casting terminology, Characteristics of molding sand, Constituents of foundry sand, Patterns and their types, Cores and types of cores, Gating system, Types of gates, Solidification, Riser system, Types of riser, Types of allowances, Directional Solidification, Defects in casting, Riser design(Chvorinov's rules), Advanced casting techniques:Shell molding, Permanent mould casting, Vacuum die casting, Low pressure die casting, Continuous casting, Squeeze casting, Slush casting, Vacuum casting, Die Casting, Centrifugal casting, Investment casting
This Presentation covers the basic concepts of Hot cracks and cold cracks in welding. For more information, please refer the books mentioned in the references slide.... Thank you
Trabajo realizado por Luis Miguel López, en la asigntura TIC, en el primer curso del Grado de Nutrición Humana y Dietética, Universidad Internacional Isabel I.
Milyen a legjobb ajándék? Olyan, amely nem csupán szép és különleges, hanem amikor majd használják, mindig rád, az ajándékozóra gondolnak közben? Olyan, amellyel egy egész családot megajándékozhatsz?
UNDERSTANDING AND MITIGATING DOWNHOLE CORROSION AND WEAR FAILURES westernfalcontx
A discussion on different types of corrosion and wear (and their associated mechanisms) followed by an overview of commercially available mitigation techniques, including their practical downhole applications are the focal points of this paper.
Corrosion of Reinforcement, Carbonation Of Concrete and It's Determination. ..Rushikesh Katkar
The corrosion of reinforcement inside concrete is one of the factors affecting the performance of the structure. Here the presentation will enlighten you about its mechanism and other aspects.
This is a presentation on hydrogen induced cracking ,sulfide stress cracking and test procedure for HIC resistant steel
DENZIL D’SOUZA
denzil22@gmail.com
metalsReviewEffects of Different Parameters on InitiatAbramMartino96
metals
Review
Effects of Different Parameters on Initiation and
Propagation of Stress Corrosion Cracks in Pipeline
Steels: A Review
M.A. Mohtadi-Bonab
Department of Mechanical Engineering, University of Bonab, Velayat Highway, Bonab 5551761167, Iran;
[email protected]; Tel.: +98-9144203460
Received: 27 March 2019; Accepted: 20 May 2019; Published: 22 May 2019
����������
�������
Abstract: The demand for pipeline steels has increased in the last several decades since they were
able to provide an immune and economical way to carry oil and natural gas over long distances.
There are two important damage modes in pipeline steels including stress corrosion cracking (SCC)
and hydrogen induced cracking (HIC). The SCC cracks are those cracks which are induced due to
the combined effects of a corrosive environment and sustained tensile stress. The present review
article is an attempt to highlight important factors affecting the SCC in pipeline steels. Based on a
literature survey, it is concluded that many factors, such as microstructure of steel, residual stresses,
chemical composition of steel, applied load, alternating current (AC) current and texture, and grain
boundary character affect the SCC crack initiation and propagation in pipeline steels. It is also found
that crystallographic texture plays a key role in crack propagation. Grain boundaries associated
with {111}‖rolling plane, {110}‖rolling plane, coincidence site lattice boundaries and low angle grain
boundaries are recognized as crack resistant paths while grains with high angle grain boundaries
provide easy path for the SCC intergranular crack propagation. Finally, the SCC resistance in pipeline
steels is improved by modifying the microstructure of steel or controlling the texture and grain
boundary character.
Keywords: stress corrosion cracking; residual stress; AC current density; crystallographic texture;
intergranular and transgranular cracks
1. Introduction
The demand for energy has increased in recent decades which forced the industry to develop
high resistance pipeline steels [1–3]. Such steels show better mechanical properties and a higher
corrosion resistance compared with normal carbon steels. However, these steels still suffer from two
important failure modes including hydrogen induced cracking (HIC) and stress corrosion cracking
(SCC) [4–6]. There are numerous studies in the literature focused on these failure modes. The SCC has
been recognized as one of the main important failure modes in humid environments and causes a huge
amount of economical loss and environmental disasters all around the world. The SCC susceptibility in
pipeline steels depends on various factors such as the microstructure of steel, distribution of inclusions
and precipitates inside the steel, texture and micro-texture of steel, chemical composition of steel, pH of
the oil and gas which is transported, the pH of soil and environment where the pipeline steel is buried,
and many other factors. Impor ...
Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
Synthetic Fiber Construction in lab .pptxPavel ( NSTU)
Synthetic fiber production is a fascinating and complex field that blends chemistry, engineering, and environmental science. By understanding these aspects, students can gain a comprehensive view of synthetic fiber production, its impact on society and the environment, and the potential for future innovations. Synthetic fibers play a crucial role in modern society, impacting various aspects of daily life, industry, and the environment. ynthetic fibers are integral to modern life, offering a range of benefits from cost-effectiveness and versatility to innovative applications and performance characteristics. While they pose environmental challenges, ongoing research and development aim to create more sustainable and eco-friendly alternatives. Understanding the importance of synthetic fibers helps in appreciating their role in the economy, industry, and daily life, while also emphasizing the need for sustainable practices and innovation.
How to Split Bills in the Odoo 17 POS ModuleCeline George
Bills have a main role in point of sale procedure. It will help to track sales, handling payments and giving receipts to customers. Bill splitting also has an important role in POS. For example, If some friends come together for dinner and if they want to divide the bill then it is possible by POS bill splitting. This slide will show how to split bills in odoo 17 POS.
Students, digital devices and success - Andreas Schleicher - 27 May 2024..pptxEduSkills OECD
Andreas Schleicher presents at the OECD webinar ‘Digital devices in schools: detrimental distraction or secret to success?’ on 27 May 2024. The presentation was based on findings from PISA 2022 results and the webinar helped launch the PISA in Focus ‘Managing screen time: How to protect and equip students against distraction’ https://www.oecd-ilibrary.org/education/managing-screen-time_7c225af4-en and the OECD Education Policy Perspective ‘Students, digital devices and success’ can be found here - https://oe.cd/il/5yV
Model Attribute Check Company Auto PropertyCeline George
In Odoo, the multi-company feature allows you to manage multiple companies within a single Odoo database instance. Each company can have its own configurations while still sharing common resources such as products, customers, and suppliers.
The Art Pastor's Guide to Sabbath | Steve ThomasonSteve Thomason
What is the purpose of the Sabbath Law in the Torah. It is interesting to compare how the context of the law shifts from Exodus to Deuteronomy. Who gets to rest, and why?
We all have good and bad thoughts from time to time and situation to situation. We are bombarded daily with spiraling thoughts(both negative and positive) creating all-consuming feel , making us difficult to manage with associated suffering. Good thoughts are like our Mob Signal (Positive thought) amidst noise(negative thought) in the atmosphere. Negative thoughts like noise outweigh positive thoughts. These thoughts often create unwanted confusion, trouble, stress and frustration in our mind as well as chaos in our physical world. Negative thoughts are also known as “distorted thinking”.
1. Stress Corrosion Cracking of
Pipeline Steels
Term paper for the course of
CORROSION AND ENVIRONMENTAL DEGRADATION OF MATERIALS
IIT KHARAGPUR
METALLURGICAL AND MATERIALS ENGINEERING
2. Introduction
Stress corrosion cracking has been attributed to many engineering failures, some of which
have resulted in loss of life and others in significant economic losses. Corrosion and stress
corrosion mechanisms are the most frequent causes of pipelines disasters, they cause from
15% to 20% of failures of gas pipelines. Stress corrosion cracking is a dangerous, often
discussed mechanism, probably the most complicated from the point of view of prevention
and safety.
Especially complex mechanisms including combinations of mechanical fatigue and corrosion
are the main features of SCC. Numerous factors affect the process: fracture resistance of a
material, its composition, microstructure and inhomogeneity, quality of the surface
affecting the initiation period, service conditions (global and local stresses), quality of
insulation etc. Natural barriers against the fracture process are reduced or destroyed by the
corrosion. The process significantly differs from those of mechanical fatigue in the air as well
as surface corrosion.The main reasons why stress corrosion cracking is complicated can be
summarized as follows:
SCC damage cannot be detected by usual internal inspection methods indicating
changes of walls thickness.
Cracks, creating usually networks, are very thin.
Pipelines pressure fluctuations, destroying surface oxide films, accelerate the SCC
process, particularly in basic environments.
Various SCC mechanisms can occur in environments of different acidity including
diluted ground solutions (preferably transgranual SCCTGSCC), in a big range of
potentials including cathodic polarization.
Mechanism
There are two forms of SCC penetrating from the external surface of buried pipelines. One is
intergranular SCC (IGSCC) and is usually called the “high pH SCC” or “classical SCC”. The
other is transgranular SCC (TGSCC), and is designated “near-neutral pH SCC” or “low pH
SCC” or “non-classical SCC”.
Intergranular stress corrosion cracking of high pressure gas pipelines occurs most commonly
as a result of hoop (circumferential) stresses due to internal operating pressures and results
in longitudinally orientated cracks. Stress corrosion testing of pipelines, usually on long test
pieces, is most commonly performed in the axial direction of the pipe. The primary
corrosion mitigation of the external surface of high pressure steel gas pipelines is protective
coatings with secondary protection usually by cathodic protection. Adhesion and resistance
to cathodicdisbondment of the coating is critical for its integrity and grit blasting is an
important process in achieving this adhesion.
3. High pH SCC and near-neutral pH SCC of pipelines
There are many similarities between the two forms of pipeline SCC. Cracks of both forms
usually occur on the outside surface in colonies, mostly oriented longitudinally along the
pipe, primarily at the bottom of the pipeline. These cracks coalescence to form long shallow
flaws, that can lead to ruptures. The fracture surfaces are usually covered with black
magnetite film or an iron carbonate film. However, there are many differences between the
two forms of pipeline SCC.
High pH SCC, engendered by concentrated bicarbonate or carbonate-bicarbonate solutions
associated with pH of 9, has usually an intergranular morphology, and the cracks are sharp,
with little lateral corrosion. Near-neutral pH SCC, engendered by dilute ground water with a
relatively low pH of around 6.5, has a trangranular, qua quasi-cleavage crack morphology
with very little branching. The transgranular cracks are generally wide with appreciable
lateral corrosion of the crack sides. Moreover, the near-neutral pH SCC occurs over a wider
potential range than high pH SCC which has only narrow width of no more than 100 mV.
Figure 1:Example of SCC on gas pipeline in acid
environment.
Figure 2:Potential-pH diagram showing the regimes for
IGSCC and TGSCC at 24◦C in solutions containing
different amounts of CO32−,HCO−3and CO2to achieve
different pH values
SCC requires the simultaneous action of the following three factors:
potent environment at the pipe surface
susceptible pipe material
stress
If any of these can be eliminated or reduced, then SCC can be prevented.
Environmental conditions
SCC failures have been mostly associated with high electrical resistivity tape coatings. The
composition of the groundwater solution depends on the amount of cathodic protection
current reaching the pipe surface. The ground water is not be changed if the coatingdoes
not allow the cathodic protection current to pass through, or if there is high electrical
resistances within the soil or the solution in the crevice between the pipeline surface and
the coating, or if there is no significant cathodic protection current reaching the
4. exposedsurfaces. The natural ground water solution has a pH from 6 to 7 resulting from the
equilibrium between HCO3-and CO32−. This solution can cause TGSCC.
However, a substantial cathodic current at thepipeline surface causes hydroxyl ions to be
generatedand accumulated, and the pH increases according toreaction:
O2 + 2H2O + 4e = 4OH−
The solution chemistry also relates to the conversionof bicarbonate to carbonate ions. With
time, the solutionbecomes concentrated and the concentration of carbonate is high, which
leads to the tendency for thesolution to passivate the steel surface, and IGSCC canoccur.
There is a difference of the polarization curve measuredin the high pH solution and the
near-neutral solution.In the high pH solution, the curve exhibits anactive-passive transition
over a certain potential rangeas illustrated in Fig. 3 from the work of Parkins.This transition
has been shown to be associated withIGSCCof ferritic steels in various environments.
Incontrast, the near-neutral pH environments do not promotepassivation and do not exhibit
an active-passivetransition (Fig. 4).
Figure 3:Potentiodynamic polarization curves showing
the potential range for IGSCC in concentrated
carbonate bicarbonate solution at 90◦C.
Figure 4:Fast and slow sweep rate polarization curves at
24◦C for a linepipe steel in simulated ground water
saturated with CO2, pH=5.8.
Metallurgical conditions
Asahi showed that, for a range of pipeline
steels from X52 to X80 grades,
thermomechanical controlled processing or
quenched and tempered steels with finegrained bainitic structures, or acicular
ferrite, uniform microstructures, were
more resistant to IGSCC than controlled
rolled steels with ferrite-pearlite structures.
It is well established that the mill scaled
Figure 5:SCC in zones with different microstructure in heat
affected zone of X60 steel pre-strained to 1% plastic
deformation.
5. surfaces on pipeline steels are more susceptible to SCCthan polished surfaces.
Moreover, if appropriately applied, grit blastingleaves the pipe surface in a state of
compression thatis beneficial in at least delaying, if not preventing, theincidence of SCC in a
variety of system.
Mechanical conditions
In order to propagate for SCC cracks, there must be an appropriate stress at the crack tip.
Beavers found that pressure fluctuations may be necessary for cracks to occur not only with
near-neutral pH SCC but also with high pH SCC. Parkins showed that cyclic loading
significantly decreased the threshold stress for IGSCC below that associated with a static
load.
The effect of surface roughness, from grit blasting, on the intergranular stress corrosion
cracking resistance of X70 gas pipelines was investigated using slow strain rate testing in
carbonate/bicarbonate solution at 75 °C.
Time to failure ratios decreased
with increasing surface roughness
indicating reduced stress corrosion
cracking resistance. The reduced
resistance
to
cracking
with
increasing roughness would be
predominantly associated with
stress concentration effects related
to the surface roughness resulting
from the grit blasting. Crack
concentration
decreased
with
increasing roughness, which is likely
to be associated with the
concentration of surface damage from the grit blasting using varying sized grit. The stress
concentration factors associated with the roughened surfaces may be similarto corrosion
pits, where Beavers et al. stated that 0.25 mm wide pits, 0.65 μm deep, had a stress
concentration of approximately 2.1.
Figure 6:Effect of roughness, Ra, on time to failure for all grit blasted
samples. Note the surface roughness is not relevant to the as formed
samples.
Discussion
The reduced resistance to stress corrosion cracking with increasing surface roughness was
likely to be associated with the stress concentration effect of the grit blasted
surfaces.Surface structural inhomogeneities, either different microstructure zones in the
steel or sulphide and other inclusions were priority initiation sites of microcracks.
6. Both stress concentration and compressive residual stresses from grit blasting are likely to
contribute to stress corrosion cracking behaviour. As formed pipe surfaces, with no grit
blasting, resulted in some of the lowest time to failure ratios and hence some of the lowest
resistances to stress corrosion cracking. These also showed some of the deepest cracks.
References
Peter Kentish, Stress corrosion cracking of gas pipelines – Effect of surface roughness,
orientations and flattening, Corrosion Science,Volume 49, Issue 6, June 2007, Pages 2521–
2533.
I. Černý, V. Linhart, An evaluation of the resistance of pipeline steels to initiation and early
growth of stress corrosion cracks, Engineering Fracture Mechanics, Volume 71, Issues 4–6,
March–April 2004, Pages 913–921.
B.W. Pan, X. Peng, W.Y. Chu , Y.J. Su, L.J. Qiao, Stress corrosion cracking of API X-60 pipeline
in a soil containing water, Materials Science and Engineering: A, Volume 434, Issues 1–2, 25
October 2006, Pages 76–81.
M.A. Arafin, J.A. Szpunar, A new understanding of intergranular stress corrosion cracking
resistance of pipeline steel through grain boundary character and crystallographic texture
studies, Corrosion Science, Volume 51, Issue 1, January 2009, Pages 119–128.