Because hydrogeninduced cracking is a weld defect that can require costly repairs and rework and possibly result in dangerous weld failures if it occurs in critical applications it is important to take steps to control and minimize the presence of hydrogen in the welding process. Hydrogen embrittlement is often the result of unintentional introduction of hydrogen into susceptible metals during forming or finishing operations. There are ndt techniques focused on identifying, measuring and tracking hic, but total focusing method tfm has shown to be generally the preferred technique. The mechanism of hydrogeninduced cracking most commonly affects vessels and pipes in hydrogen and hydrogen sulfide processing or. Hydrogen induced craking hic, also referred to as hydrogen stress cracking or static fatigue, is a typical form of hydrogen embrittlement. Hydrogeninduced crack growth rate in steel plates exposed to. Another source of hydrogen during the manufacturing process is the galvanising process or. This is a type of deterioration which can be linked to corrosion and corrosioncontrol processes. Hydrogeninduced cracking hic is a far too common type of failure. Naceastm g193 1 includes the following description of hydrogen blistering. Hydrogen cracking its causes, costs and future occurrence. But we do not know whether ae is effective to monitor hydrogen induced cracking hic of pressure vessel made by carbon steel.
Welding of carbon and low alloy steels and hydrogen induced. Environmental cracking can occur with a wide variety of metals and alloys and includes all of the types of corrosion failures listed below. Journal of iron and steel research international 22. Steel pipelines and pressurised equipment can operate satisfactorily for up to 8 to 10 years before any cracks are discovered. Preheating is one of the best step to achieve good solidify microstructure as it slows. Liquid metal crackinglmc, usually a physicochemical process. Hydrogen embrittlement he also known as hydrogen assisted cracking hac and hydrogeninduced cracking hic, describes the embrittling of metal after being exposed to hydrogen. Hydrogeninduced cracking and blistering digitalrefining. Steel pipelines and pressurised equipment can operate satisfactorily for up. Hydrogeninduced cracking an overview sciencedirect topics.
Investigation on acoustic emission of hydrogen induced. Hic usually occurs due to the effects of aqueous hydrogen charging of steel in wet h2s refinery process environments. No external stress on test specimens is usually required to examine this type of cracking. Our last post factors influencing hydrogen induced cracking went over the factors that contribute to hydrogeninduced cracking. Exposure of carbon steel equipment to wet h2s service environments can lead to various forms of attack, e. The hydrogen is first produced as hydrogen atoms h which normally combine rapidly to form hydrogen molecules h 2. Prevention of delayed hydrogen induced cracking joint must be thoroughly cleaned, dried and free from any kind of rust, scale, mill, oil, grease, coating etc. These steps can help reduce the risk of cracking that leads to costly rework, downtime, increased labor needs, poor productivity and most importantly, product failure. Its even more important to protect against this weld defect to. According to this theory, hydrogeninduced cracking occurs in five steps as follows corresponding to the detailed hic mechanisms shown in figure 1 7, 8 hydrogen solubility and hydrogen diffuses in. Induction heating is a good option for minimizing hydrogen in. An overall process of disproportionation can be observed, where light, hydrogen rich products are formed at the expense of heavier molecules which condense and are depleted of hydrogen. Nov 14, 2014 the presence of hydrogen in the weld metal or haz may lead to a form of cracking known as hydrogen.
Sulfide stress cracking mostly occurs in very highly acidic environments. According to this theory, hydrogen induced cracking occurs in five steps as follows corresponding to the detailed hic mechanisms shown in figure 1 7, 8 hydrogen solubility and hydrogen diffuses in. Effect of microstructure on hydrogeninduced cracking of. Hydrogen induced cracking in weldments hydrogen induced cracking, also referred to in the litera ture as cold cracking, delayed cracking, underbead cracking and internal hydrogen embrittlement, is in general one of the most important potential sources of defects in welding hardenable.
Preventing hydrogen induced cracking welding answers. Hydrogen induced cracking hic damage is a degradation mechanism active in the oil and gas industry. Combatting the problem of hydrogen induced cracking in sour service, hic steel plate is carbon steel plates which are tested to assess the susceptibility of the material to hydrogen induced cracking. It involves atomic hydrogen, which is the smallest atom, that diffuses into a metallic structure.
Pdf sulfide stress corrosion cracking and hydrogen induced. The test procedure involves the evaluation of resistance of pressure vessel steel plate and pipework steels to hydrogen reduced cracking caused. Hydrogen induced cracking hic from advanced ndt solutions. Liquid metal cracking lmc, usually a physicochemical process. Hydrogen induced cracking steel features, applications and. Hydrogen induced cracking hic is a common form of wet h2s cracking caused by the blistering of a metal due to a high concentration of hydrogen. Welder associates must define the peculiar interpass temperature.
Hydrogen induced cracking hic is most commonly encountered in steels but other metals are susceptible, as shown in table 33. Hydrogeninduced cracking hic is the stepwise internal cracks that connect adjacent hydrogen blisters on different planes in the metal, or to the metal surface. It is a complex process that is not completely understood because of the variety and complexity of mechanisms that can lead to embrittlement. Common causes and cures of hydrogen cracking knowing the means by which hydrogen can enter the weld is a good defense against potential problems. The actual reaction is known as homolytic fission and produces alkenes, which are the basis for the economically important production of polymers. Hydrogen induced cracking hic is a common form of wet h2s cracking. These steps can help reduce the risk of cracking that leads to costly rework, downtime, increased labor needs, poor. Hydrogeninduced cracking hic refers to the internal cracks brought about by material trapped in budding hydrogen atoms. Jun 03, 2018 hydrogeninduced cracking hic refers to the internal cracks brought about by material trapped in budding hydrogen atoms. We will now go over how to prevent hic from happening. The methane molecules create a pressure which leads. This is a problem commonly found in wet h2ssour service operating environments such as in the oil, gas and petrochemical industry. An overall process of disproportionation can be observed, where light, hydrogenrich products are formed at the expense of heavier molecules which condense and are depleted of hydrogen.
It was found that very few papers studied the acoustic emission of hic of carbon steel through literature searches. The factors which contribute to hic are i presence of h2, ii high tensile stress, iii susceptible microstructures, iv temperatures which are between around 200 deg c and 100 deg c, and v time. Sep 02, 2015 mechanism of cracking in the presence of h2s, the process of cracking hic can be divided in to 5 stages 1 corrosion. Hydrogeninduced cracking hic in steel is a risk problem when steels are charged with hydrogen in service as in various hydrogen sulfide environments like sour oil and gas wells and some power plants. Jul 29, 2019 combining action of atomic hydrogen into hydrogen gas is a cumulative process and builds up of hydrogen gas pressure eventually leads to hydrogen induced cracking hlc. This form of cracking is also commonly referred to as hydrogen. If you recall, we mentioned you need all three factors to be present in order to have hic. Hydrogen damage figure 1 is encountered in many steel processes, such as pickling, electroplating and welding. The hydrogen is produced by the cathodic partial reaction of the electromechanical processes which is why the damage caused is designated as electromechanical induced hydrogen cracking. Hic steel hydrogen induced cracking supplier company.
Service failure due to fatigue and brittle fracture of welded components cost the industry. Hydrogeninduced cracking hic is still a challenging issue that requires. Sulfide stress cracking is the worst type of corrosion in the presence of hydrogen sulfide. O ur last post factors influencing hydrogen induced cracking went over the factors that contribute to hydrogen induced cracking. Hydrogen embrittlement he also known as hydrogen assisted cracking hac and hydrogen induced cracking hic, describes the embrittling of metal after being exposed to hydrogen.
Hydrogen induced cracking hic is a phenomenon mainly associated with welds in low alloy steels. Additionally, hydrogen atoms diffuse through metals and coalesce. Hydrogen sulphide gas is a poisonous gas and cannot be emitted into the environment without treatment, thus hydrogen sulphide cracking process has. The hydrogen atom is the smallest of all atoms and hydrogen attack is similarly insidious and hidden from simple inspection techniques. The ssc of medium strength steels has been a continuing source of trouble in the oil fields, and from these troubles has evolved in international standards 6.
The blistering damage tends to form parallel to the surface and to the direction of hoop stress. The presence of hydrogen atoms in a metal degrades some of its mechanical properties, especially its ductility, leading in some cases to embrittlement. Combining action of atomic hydrogen into hydrogen gas is a cumulative process and builds up of hydrogen gas pressure eventually leads to hydrogen induced cracking hlc. Hydrogen production 2 hydrogen diffusion 3 hydrogen trapping in defaults 4 increasing of pressure 5 cracking hydrogen induced cracking hic 10. Hydrogen induced cracking is associated with absorption of hydrogen and a delayed time to failure incubation time during which hydrogen diffuses into regions of high triaxial stress. Hydrogen induced cracking hic and the blistering of carbon steel are both such unexpected corrosion phenomenon. Hic test apparatus is supplied with essential spares for uninterrupted long term testing. Furthermore, a standard model for crack initiation and propagation processes needs to be established. Hydrogen embrittlement is the process by which various metals, most importantly highstrength steel, become brittle and fracture following exposure to hydrogen.
Hydrogeninduced cracking hic is most commonly encountered in steels but other metals are susceptible, as shown in table 33. Hic test specimens are machined with thickness of 530mm, width 20mm, and length of 100mm is suitable for testing as per the nace standard. To avoid the consequences of hydrogeninduced cracking rework, increased labor and material costs, lost productivity and quality issues it is important to implement methods of controlling hydrogen in the welding process. Sulfide stress corrosion cracking and hydrogen induced cracking of a216wcc wellhead flow control valve body article pdf available in case studies in engineering failure analysis. Hic damage is a common degradation mechanism in the oil and gas industry. This occurs when steel is rapidly cooled and allowed to form martensite. In the case of a crystal lattice becoming saturated or coming into contact with atomic hydrogen, many alloys and metals may. Corrosionpedia what is hydrogeninduced cracking hic. Cracking occurs due to a significant loss in ductility in the weld metal andor heat affected zone haz. Hydrogen induced cracking test apparatus is rectangular provided with ready to use connections fittings. The principal distinguishing feature of this type of crack is that it occurs in ferritic steels, most often immediately on welding or a short time after welding.
Hydrogen induced cracking hic on steel for corrosion. Hydrogen induced cracks either follow a linear or stepwise path within the material, hence the term stepwise cracking. Susceptibility to hydrogeninduced cracking of api 5l b and x52ms lowcarbon. Hydrogen induced cracking hic is a failure mechanism resulting in sudden exposures and cracks due to growing laminations inside the base material and welds. Sulfide stress cracking is a function of hydrogen sulfide concentration as low as ppm, hydrogen sulfide partial pressure, stresses, material yield strength, temperature and ph. Also high strength structural steels which are welded are exposed to a certain hydrogen pickup which means a risk at fracture and blistering due to hic.
Processes or conditions involving wet hydrogen sulfide, i. Hydrogen blistering and hydrogen induced cracking hic. The presence of hydrogen in the weld metal or haz may lead to a form of cracking known as hydrogen. Mechanism of cracking in the presence of h2s, the process of cracking hic can be divided in to 5 stages 1 corrosion. Hydrogen induced cracking hic occurs when carbon steel is exposed to hydrogen sulphide h 2 s and is the direct result of electrochemical corrosion reactions between the sour service or wet h 2 s environment. Common causes and cures of hydrogen cracking fabricating. Hic test, hydrogen induced cracking test, step wise cracking. Damage due to hydrogen embrittlement and stress corrosion. Examples of internal hydrogen embrittlement include processes such as casting, carbonizing, surface cleaning, pickling, electroplating, electrochemical.
Hydrogen induced cracking hic assessment in a gas processing plant case study mohammed a abufour, mohammad. Hydrogen sulphide cracking is a type atom cracking process that helps in breaking down hydrogen atoms from sulphur atoms in aqueous hydrogen sulphide, which is available in crude oil and natural gas. Part of the hydrogen produced by the cathodic corrosion reaction may permeate the steel by diffusion, and the balance is dissolved in the process. Hydrogen induced cracking hic is wet h2s cracking in steel in the form of blisters or blister cracks. Hydrogeninduced cracking susceptibility in highstrength. Its even more important to protect against this weld defect to prevent dangerous product failures. Hydrogeninduced craking hic, also referred to as hydrogen stress cracking or static fatigue, is a typical form of hydrogen embrittlement. These internal cracks may propagate by a process called hydrogeninduced cracking hic or hydrogen blistering. Hydrogen embrittlement he also known as hydrogen assisted cracking hac and. It is characterized by the brittle fracture of a normally ductile alloy under sustained load in the presence of hydrogen. Hic usually occurs due to the effects of aqueous hydrogen charging of steel in wet h2s refinery process. Cracking occurs due to a significant loss in ductility. These internal cracks may propagate by a process called hydrogen induced cracking hic or hydrogen blistering. The hic may promote one mode of fracture in an alloy rather than another form normally observed in benign environments.
Moreover the rapidity of the stovepipe process allows a modification to this in using the quick application of the softening hot pass to become an integral part of the welding technique for avoiding root pass hydrogen cracking, but to the best of the authors knowledge this aspect has not been incorporated into a published prediction scheme. Hydrogen cracking may also be called cold cracking or delayed cracking. Factors influencing hydrogen induced cracking welding answers. The consequences and control of hydrogen in the welding process. It involves the ingress of hydrogen into a component, an event that can seriously reduce the ductility and loadbearing capacity, cause cracking and catastrophic brittle failures at stresses below the yield stress of susceptible materials. Andreikiv applied ae to monitor the extending process of 9khf and 4340 steel specimen exposed to 0.
In the case of a crystal lattice becoming saturated or coming into contact with atomic hydrogen, many alloys and metals may lose their mechanical properties. Cold cracking is also called hydrogeninduced cracking or simply hydrogen cracking because hydrogen trapped in the weld and heataffected zone is responsible for this type of cracking. A comparative study of hydrogeninduced cracking resistances of. Sulfide stress cracking an overview sciencedirect topics. Factors influencing hydrogen induced cracking welding. The methane molecules create a pressure which leads to embrittlement and even cracking of the metal. Hydrogen induced cracking in flux cored electrode welds. About one inch from either side of joint must be cleaned using specific type of cleaning process. The formation of subsurface planar cavities, called hydrogen blisters, in a metal resulting from excessive internal hydrogen pressure. Hydrogen induced cracking is a mechanical fracture caused by penetration and diffusion of atomic hydrogen into the internal structure of steel, which changes into molecular. Hydrogen induced cracking hic when corrosion of steel occurs in an acid solution e. Hydrogen combines with carbon within the alloy and forms methane. It is also called hydrogen assisted cracking hac and delayed cracking since it does not occur right after welding, but a few hours or days after the weld has completely cooled down to ambient temperature.