Tension Tests Behavior of API 5L X60 Pipeline Steel in a Simulated Soil Solution to Evaluate SCC Susceptibility

2012 ◽  
Vol 1481 ◽  
pp. 71-80
Author(s):  
A. Contreras ◽  
S. L. Hernández ◽  
R. Galvan-Martinez ◽  
O. Vega-Becerra
Keyword(s):  
Strain Rate ◽  
Soil Solution ◽  
Room Temperature ◽  
Pipeline Steel ◽  
Failure Process ◽  
Low Carbon Steel ◽  
Fracture Type ◽  
Low Carbon ◽  
Surface Fracture ◽  
Tension Tests

ABSTRACTIn this work slow strain rate tests (SSRT) were used for the evaluation of API 5L X60 in contact with a simulated soil solution called NS4 in order to evaluate stress corrosion cracking (SCC) susceptibility. SSRT were carried out in NS4 solution at room temperature to simulate dilute ground water that has been found to be associated with SCC of low carbon steel pipelines. A strain rate of 1x10-6 sec-1 was used. According to the analysis of SSRT results, the X60 pipeline steel is highly resistant to SCC at the conditions studied. A combine fracture type it was observed: ductile and brittle with a transgranular appearance. Some pits close to the fracture zone were observed. The failure process and mechanism of X60 steel in NS4 solution are controlled by anodic dissolution and hydrogen embrittlement which was revealed with the internal cracks observed in the surface fracture. There is a relation between the strength of the steel and the SCC susceptibility, thus, increasing strength in the steel, the SCC susceptibility increases as a function of the pH solution used.

Electrochemical and Tension Tests Behavior of API 5L X60 Pipeline Steel in a Simulated Soil Solution

2013 ◽  
Vol 755 ◽  
pp. 153-161 ◽  
Author(s):  
Luis M. Quej-Aké ◽  
Ricardo Galván-Martínez ◽  
Antonio Contreras-Cuevas
Keyword(s):  
Carbon Steel ◽  
Strain Rate ◽  
Soil Solution ◽  
Electrochemical Impedance ◽  
Pipeline Steel ◽  
Failure Process ◽  
Low Carbon Steel ◽  
Low Carbon ◽  
Tension Tests ◽  
Before And After

In this work electrochemical impedance spectroscopy (EIS) and slow strain rate tests (SSRT) were used for the evaluation of API 5L X60 carbon steel in contact with a simulated soil solution called NS4. EIS monitoring before and after performing the tension tests was carried out. SSRT were carried out in NS4 solution at room temperature to simulate dilute ground water that has been found associated with stress corrosion cracking (SCC) of low carbon steel pipelines. A strain rate of 1x10-6 sec-1 was used. According to the analysis of SSRT, the X60 pipeline steel is highly resistant to SCC. In order to perform the electrochemical test, two working electrodes were considered, a complete specimen, before the SSRT and a fractured specimen after the SSRT. The analyses of results show that the electrochemical response was different in each samples. The corrosion rate (CR) obtained by the two corrosion techniques revealed that the CR of the fractured specimen was higher than the CR of the complete specimen. This behavior is attributed to the fact that the fractured specimen present a high degree of tortuosity and this condition activate the corrosion process. In addition, according to the cathodic Tafel slope, the reduction reacction was influenced by a difusion process. A combine fracture type in SSRT was observed: ductil and brittle with a transgranular appearance. Some pits and internal cracks close to the fracture zone were observed. The failure process and mechanism of X60 steel in NS4 solution are controlled by dissolution and hydrogen embrittlement.

Stress Corrosion Cracking Behavior of X60 Pipe Steel in Soil Environment

2009 ◽  
Vol 1242 ◽  
Author(s):  
Z. Velazquez ◽  
E. Guzman ◽  
M‥A. Espinosa-Medina ◽  
A. Contreras
Keyword(s):  
Strain Rate ◽  
Stress Corrosion ◽  
Soil Solution ◽  
Stress Corrosion Cracking ◽  
Room Temperature ◽  
Cathodic Polarization ◽  
Pipeline Steel ◽  
Corrosion Cracking ◽  
Time To Failure ◽  
Cracking Behavior

ABSTRACTStress corrosion cracking (SCC) susceptibility of API X60 pipeline steel in a soil solution by slow strain rate tests (SSRT), and surface fracture analysis was investigated. The SSRT were performed at strain rate of 25.4 × 10-6 mm/sec in a glass autoclave containing the soil solution called NS4 with pH of 3 and 10 at room temperature and 50°C. Both anodic and cathodic polarization potentials of 200 mV referred to Ecorr was applied. The results of ratio reduction area (RRA), time to failure ratio (TFR) and elongation plastic ratio (EPR) indicate that X60 pipeline steel was susceptible to SCC at pH 3 and cathodic polarization of -200 mV at room temperature and 50°C. Scanning electron microscopy (SEM) observations of these specimens showed a brittle type of fracture with transgranular appearance. The SCC process and mechanism of X60 steel into NS4 solution was hydrogen based mechanism. With the different applied potentials the dominance of SCC process changes. At low pH the temperature effect on SCC susceptibility is more noticeable at 20°C. However at high pH this effects changes, being the steel more susceptible to SCC at 50°C.

Crystallographic Texture Control Helps Improve Pipeline Steel Resistance to Hydrogen-Induced Cracking

2010 ◽  
Author(s):  
V. Venegas ◽  
O. Herrera ◽  
F. Caleyo ◽  
J. M. Hallen ◽  
T. Baudin
Keyword(s):  
Grain Boundaries ◽  
Crystallographic Texture ◽  
Pipeline Steel ◽  
Low Carbon Steel ◽  
Rolling Process ◽  
Warm Rolling ◽  
American Petroleum Institute ◽  
Low Carbon ◽  
Steel Rolling ◽  
Hydrogen Induced Cracking

Low-carbon steel specimens, all within API (American Petroleum Institute) specifications, were produced following different thermomechanical paths. After austenization, the samples were rolled and recrystallized. The rolling process was carried out using different reduction-in-thickness degrees and finishing temperatures. The investigated steels showed similar microstructural features but differed considerably in their crystallographic textures and grain boundary distributions. After cathodic hydrogen charging, hydrogen-induced cracking (HIC) was detected in the hot-rolled recrystallized steels, whereas the cold and warm-rolled recrystallized steels proved resistant to this damage. Among the investigated specimens, the HIC-stricken show either the strongest {001}ND texture fiber, the smallest fraction of low-angle grain boundaries, or the weakest {111}ND (γ) texture fiber ({hkl}ND representing crystallographic orientations with {hkl} planes parallel to the steel rolling plane). In contrast, the HIC-resistant steels show the weakest {001}ND texture fiber, the largest fraction of low-angle grain boundaries, and the strongest γ fiber. These results support the hypothesis of this and previous works, that crystallographic texture control, through warm rolling schedules, helps improve pipeline steel resistance to hydrogen-induced cracking.

Hot Deformation Studies of a Low Carbon Steel Containing V

2013 ◽  
Vol 554-557 ◽  
pp. 1224-1231 ◽  
Author(s):  
Cecilia Poletti ◽  
Martina Dikovits ◽  
Javier Ruete
Keyword(s):  
Strain Rate ◽  
Hot Deformation ◽  
Flow Instability ◽  
True Strain ◽  
Low Carbon Steel ◽  
Dynamic Effect ◽  
Rate Sensitivity ◽  
Low Carbon ◽  
Compression Tests ◽  
Deformation Parameters

Low alloyed steels produced by continuous casting are thermomechanically treated to achieve final high mechanical properties, meaning a good combination of strength and toughness. The hot deformation mechanisms of a micro-alloyed steel containing up to 0.1wt% of V is studied by means of hot compression tests using a Gleeble®3800 device. Austenitization of samples is carried out at 1150°C during 2 minutes followed by cooling to the deformation temperature at 1Ks-1in the range of 750 – 1150°C. The studied strain rate range is from 0.01 to 80 s-1and the total true strain achieved is of 0.7. In situ water quenching is applied after the deformation to freeze the microstructure and avoid any post dynamic effect. The Ar3temperature is determined by dilatometry experiments to be 725°C for the used cooling rate. The stress values obtained from the compression tests are evaluated at different strains to determine the strain rate sensitivity and flow instability maps and thus, to predict the formability of the material in the range of studied deformation parameters. These maps are correlated to the microstructure at specific deformation parameters.

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