Cracking Of Steel Research Articles

Effect of Rolling Process Parameters on Transverse Cracks on the Surface of Q345 Steel

This article examines the evolutionary behavior of transverse surface cracks in Q345 steel during the hot‐rolling process under various rolling conditions. “V”‐shaped cracks are prefabricated on the billet surface for laboratory hot‐rolling tests, and a corresponding rolling model is developed to validate its accuracy. The slab rolling model is established based on actual onsite rolling process parameters. The aim is to analyze the effects of different rolling conditions on the surface crack morphology and aspect ratio. The results indicate that variations in roll diameter (1400, 1300, and 1200 mm) influence crack propagation, with cracks unfolding earlier when the roll diameter is 1400 mm. At varying initial rolling temperatures (1300, 1200, and 1100 °C), cracks begin to unfold earlier at the highest temperature of 1300 °C. When examining different friction coefficients (0.4, 0.5, and 0.6), cracks unfold earlier at the highest coefficient of 0.6. Similarly, at different rolling speeds (3, 4, and 5 m s−1), cracks unfolded earlier at the highest speed of 5 m s−1. Analysis of changes in crack depth and aspect ratio during rolling shows that the initial few passes have a greater influence on crack depth and unfolding. In the later stages of rolling, cracks continue to unfold, though the depth shows minimal variation, and the aspect ratio tends to approach zero.

An Empirical Model of the Kinetics of Hydrogen-Induced Cracking in Pipeline Steel, Using Statistical Distribution Models and Considering Microstructural Characteristics and Hydrogen Diffusion Parameters

An Empirical Model of the Kinetics of Hydrogen-Induced Cracking in Pipeline Steel, Using Statistical Distribution Models and Considering Microstructural Characteristics and Hydrogen Diffusion Parameters

Effect of pre-strain on hydrogen-induced delayed cracking and hydrogen trapping behavior in high-strength martensitic steels

Pre-strain is a key factor affecting the critical conditions for hydrogen-induced delayed cracking (HIDC). In this study, the threshold stress and critical hydrogen concentration for HIDC of MS1300 and MS1500 steels with different pre-strains were measured by constant load tensile (CLT) tests. The results demonstrated that although MS1500 has higher strength, its safe service strength is lower than that of MS1300 when the hydrogen content exceeds 0.5 wppm. Additionally, the hydrogen penetration, thermal desorption spectroscopy, and hydrogen microprinting methods were also used to analyze the hydrogen-induced failure mechanism. These studies provide an effective data reference for improving the industrial production process.

Effect of Aggressive Anions on the Stress Corrosion Cracking of Stainless Steel in Hot Pressurized Alkaline Water

Abstract U-bend stress corrosion cracking (SCC) testing of low Cr ferritic (Type 409) and austenitic (Type 304L) stainless steel was conducted in a hot pressured alkaline water to study the effect of aggressive anions (Cl− and HS−) on the relative susceptibility. SCC was only observed in Type 304L when immersed in the solution that contained both aggressive anions. Critical factors were identified based on cross-section examination of the U-bends after exposure using complementary electron microscopy techniques. These factors include: (i) preferential oxidation of deformation bands (arising from cold working), (ii) Ni-S compound formation at the oxide/metal interface and (iii) S and Cl incorporation into the inward growing Cr-rich oxide. These critical factors were considered within an overall slip dissolution-type mechanism to account for the SCC observed.

Thermal cycles, structure and properties of welded joints in structural steels during welding in extreme cold conditions

The article summarizes research on the thermal cycles, structure, and properties of welded joints made from low-alloy and low-carbon steels during arc welding in sub-zero temperatures. This review aims to analyze previous research to create solid recommendations for welding steel bridge structures during winter conditions. The results of a comparison of experimental measurements of thermal cycles of welding samples with different sizes made at room and subzero ambient air temperatures (down to minus 50 °C) are considered. It is shown that in small plates with dimensions of 200 × 250 × 10 mm, due to more intense heat reflection from the edges of the specimen, the thermal cycles of welding at different temperatures do not differ significantly. In more massive samples (sized 450 × 250 × 10 mm), an increase in the cooling rate of the overheated welded joint area is observed compared to room temperature welding. The impact of hydrogen on the development of cold cracks in low-alloy steels during welding at temperatures below freezing is examined. Metallographic analysis has revealed that the structural changes that occur during the welding of various steel grades are notably different and are influenced by the steel’s chemical composition as well as the thermal cycle parameters of the welding process. Dilatometric studies indicate that variations in the levels of alloying elements within different grades significantly influence the kinetics of austenite transformation. Therefore, to identify the best welding techniques for subzero temperatures, it is essential to consider not just how heat disperses in these conditions, but also the kinetics of phase changes and their effects on the structure and properties of the products resulting from austenite decomposition.

Fatigue damage analysis and mitigation for steel structures using UHM-CFRP prestressed technique

Fatigue stresses in steel bridges can lead to crack propagation, gradually decreasing the structural stability of the bridge. Conventional strengthening techniques for structures have shown limited effectiveness in preventing crack growth. The objective of this research is to enhance the fatigue life of cracked steel beams through the application of ultra-high modulus carbon fiber reinforced polymer (UHM-CFRP) plates. Two sets of tests, including quasi-static testing and fatigue testing, were conducted on both cracked and uncracked steel beams. All beams were tested under identical loading conditions, with a total of five beams examined. Control beams were used to compare fatigue life under different loading ranges. One beam was reinforced with UHM-CFRP plates, another utilized prestressed UHM-CFRP plates, and another employed UHM-CFRP plates with end clamps. The experimental study revealed a significant 8 times increase in fatigue lives for cracked steel beams repaired using the UHM-CFRP compared to the control beam. Additionally, the (10 %) prestressed UHM-CFRP plate not only doubled the fatigue life of identical beams compared to UHM-CFRP plates but also significantly reduced residual deflection during fatigue crack growth, highlighting its efficacy in fatigue resistance.

Experimental study on the fatigue behavior of CFRP-strengthened cracked steel plates under eccentric axial tension

In this paper, an experimental investigation has been conducted to study the fatigue behavior of single edge-notch steel plates strengthened with CFRP (laminates/sheets). The plates have been subjected to eccentric fatigue under axial loading conditions. The experimental study includes fourteen specimens and has been tested under axial loading until failure. The constant parameters in the study are steel material grade, steel plate dimensions, and fatigue loading conditions. Meanwhile, the studied parameters are steel plate initial edge crack size, CFRP configurations (length, one or two-sided, and laminates or sheets), and adhesive material strength. The experimental results revealed that the fatigue life for specimens strengthened with CFRP sheets or CFRP laminates can be improved by a factor of 1.15 to 3.87 and 1.47 to 6.32, respectively, compared with the un-strengthened specimens. The results show that using CFRP can be considered an efficient way to repair the initial cracks in steel elements under eccentric axial fatigue loading.

Analysis, Assessment, and Mitigation of Stress Corrosion Cracking in Austenitic Stainless Steels in the Oil and Gas Sector: A Review

This comprehensive review examines the phenomena of stress corrosion cracking (SCC) and chloride-induced stress corrosion cracking (Cl-SCC) in materials commonly used in the oil and gas industry, with a focus on austenitic stainless steels. The study reveals that SCC initiation can occur at temperatures as low as 20 °C, while Cl-SCC propagation rates significantly increase above 60 °C, reaching up to 0.1 mm/day in environments with high chloride concentrations. Experimental methods such as Slow Strain Rate Tests (SSRTs), Small Punch Tests (SPTs), and Constant-Load Tests (CLTs) were employed to quantify the impacts of temperature, chloride concentration, and pH on SCC susceptibility. The results highlight the critical role of these factors in determining the susceptibility of materials to SCC. The review emphasizes the importance of implementing various mitigation strategies to prevent SCC, including the use of corrosion-resistant alloys, protective coatings, cathodic protection, and corrosion inhibitors. Additionally, regular monitoring using advanced sensor technologies capable of detecting early signs of SCC is crucial for preventing the onset of SCC. The study concludes with practical recommendations for enhancing infrastructure resilience through meticulous material selection, comprehensive environmental monitoring, and proactive maintenance strategies, aimed at safeguarding operational integrity and ensuring environmental compliance. The review underscores the significance of considering the interplay between mechanical stresses and corrosive environments in the selection and application of materials in the oil and gas industry. Low pH levels and high temperatures facilitate the rapid progression of SCC, with experimental results indicating that stainless steel forms passive films with more defects under these conditions, reducing corrosion resistance. This interplay highlights the need for a comprehensive understanding of the complex interactions between materials, environments, and mechanical stresses to ensure the long-term integrity of critical infrastructure.

Effect of charging temperature of continuous casting slab on the surface cracks of HSLA steel thick plate

In order to investigate the formation mechanism of the surface cracks on high-strength low-alloy (HSLA) steel thick plates, this paper simulated the temperature history of different hot charging processes, and deduced the microstructural transformation behavior and recrystallization austenitization process under different charging temperatures. This paper proposed four hot charging modes and ultimately elucidated the effect of charging temperature on the surface cracks of HSLA steel thick plates. Experimental results showed significant differences in the microstructure and recrystallized austenite grains under different charging temperatures. Analysis revealed that the recrystallized austenite grains were determined by the microstructure. The presence of austenite in the microstructure significantly increased the size of recrystallized austenite grains, thereby disrupting the uniformity of grains. Based on the relationship between charging temperature, microstructure, and recrystallized austenite grain state, the hot charging process of HSLA steel was divided into four temperature zones: high-temperature single-phase zone, high-temperature two-phase zone, medium-temperature three-phase zone, and low-temperature two-phase stable zone. The occurrence of the surface cracks in HSLA steel was caused by the recrystallized austenite mixcrystal structure generated during charging in the medium-temperature three-phase zone. The uneven recrystallized austenite grains caused by undercooled austenite were the direct cause of the surface cracks, while high charging temperature was the root cause. When the charging temperature entered the medium-temperature three-phase temperature zone, recrystallized austenite grains would exhibit mixcrystal structure. These mixcrystal structure deteriorated the surface quality, promoting the formation, deformation, and propagation of surface cracks. To reduce the occurrence rate of surface cracks, for steel grades sensitive to surface quality, the charging temperature should be controlled in the low-temperature two-phase stable zone.

A Limited Evaluation of the Applicability of NACE MR0175/ISO 15156 H2S Limits to Supercritical CO2 Pipelines

In an earlier paper one of the authors raised the question of whether the hydrogen sulfide (H2S) partial pressure threshold of 0.05 psia (0.3 kPa) for cracking of steels from sulfide stress cracking is pertinent to dense phase carbon dioxide (CO2) systems in which there is no free gas phase. This paper presents a limited test of the pertinence of this threshold value in Supercritical CO2. Autoclave tests of four-point bend beam specimens of API 5L Grade X80 line pipe steel at 0.05 psia (0.3 kPa) and 0.20 psia (1.38 kPa) H2S were performed and the samples were examined after testing for cracking. In addition, the test conditions were modeled with the OLI Studio software to determine the H2S fugacities and H2S concentrations in the brine phase. No cracking was found after 30 d of exposure.

The impact of loading rate on chloride induced stress corrosion cracking of 304L stainless steel

Abstract The influence of applied loading rate (dK/dt) on stress corrosion cracking (SCC) behavior in annealed 304L stainless steel immersed in 4.7 M MgCl2 solution was assessed at varying temperatures from 23 °C to 70 °C. Measured crack growth rates obtained under rising K loading (dK/dt > 0) are compared to those obtained during static K testing. A rising K-based loading protocol was found to yield more conservative crack growth rates across all temperatures, with the variation in crack growth rates (and therefore the dependence in loading rate) decreasing with increasing environmental severity.

Analytical model for concrete crack width of steel lined reinforced concrete penstock

Cracking in steel lined reinforced concrete penstock (SLRCP) poses substantial challenges to both serviceability and safety, particularly when crack width exceeds specified limits. Despite its critical implications, accurately calculating crack width remains a persistent challenge. To address this issue, a multi-layer steel-concrete ring analytical model is derived through the concept of orthotropic and thick-walled cylinder theories. In this model, the cracked concrete is assumed to be an orthotropic material incorporating both elastic modulus reduction and tensile softening behavior based on its cracking characteristic of radial penetrating cracks uniformly distributed on the circumference. The steel liner and reinforcing steel bar are modeled as continuous steel rings using equivalent stress theory, while thick-walled cylinder theory is applied due to geometric features and bearing characteristics. Crack width is determined through equilibrium of force and compatibility of deformations at steel-concrete interfaces, utilizing these assumptions and the developed calculation model. To validate the proposed model, data from prototype observations and large-scale model tests of SLRCPs were systematically collected. The crack width results obtained from the proposed model exhibit strong agreement with the collected data, confirming its accuracy and reliability. In conclusion, the proposed analytical model provides an effective solution for calculating the crack width of SLRCP and offers valuable insights for durability evaluation.

Experimental Study of Avalanche Damage Protection Methods for Main Steel Gas Pipelines.

This paper conducted an experimental study of reduced models of a main gas pipeline for avalanche damage considering operational conditions. Two options were considered as a method of avalanche damage prevention: single steel rings at the crack edges and steel winding with a winding pitch of 0.25 m. For the tension force, 5% of the steel wire breaking force was taken, which was equal to 1 mm. The ambient environment was simulated by a climatic chamber, where two options of temperature loads were considered: +20 °C and -10 °C. It was found that reinforcement with single rings of pipeline models under conditions of positive (+20 °C) and negative (-10 °C) temperatures showed that the crack opening width in the ring direction decreased 1.63 times and 1.9 times, accordingly. The crack length (longitudinal direction) decreased 2.18 times and 2.45 times, accordingly. The reinforcement of the pipeline models with prestressed wire winding on the crack propagation under conditions of positive (+20 °C) and negative (-10 °C) temperatures showed that the width of the crack opening in the ring direction decreased 1.5 times and 1.46 times, accordingly. The crack length (longitudinal direction) decreased 1.4 times and 1.44 times accordingly, which is a positive moment in addressing the issue of the localisation and stoppage of a crack fracture in main gas pipelines. Simultaneously, the analysis of the prestressed pipelines model test results on crack fracture propagation showed that single rings are more effective, which decreased the crack opening width by 1.1 times and the crack length up to 1.5. Therefore, the experimental results obtained positively complement the available methods of crack localisation in main gas pipelines, which can be used by engineers and research communities when designing or reinforcing existing operating main steel gas pipelines.

Fracture behavior of additively manufactured corrax maraging stainless steel

Additively manufactured a low carbon Fe–Cr–Ni–Al Corrax stainless steel has ultra-high strength, but the mechanism at work when the steel cracks is still unclear. In this study, Corrax stainless steel was tensile tested to fracture and cracks in the vicinity of the fracture surface were analyzed by scanning electron microscope and electron-backscattered diffraction. The results show that the cracks propagated at angles of 45–60° to the tensile axis. Some cracks were transgranular, and high-angle grain boundaries had little effect on crack propagation. Crack propagation was inhibited in regions with lower Taylor factors. Kernel average misorientation value analysis established that the crack propagation process is accompanied by significant plastic deformation. The influence of particles and unfused pores on crack propagation is also discussed.

Modeling 3D finite element analysis of a semi-elliptical crack on stress corrosion cracking of API X52 pipeline

In this study, an external semi-elliptical crack was modeled in a 3D API 5 L X52 pipeline with stress corrosion cracking (SCC). To make the crack, the finite element method (FEM) was used to obtain the failure pressure (Pf) and its mechanical behavior. The longitudinal crack had a constant length (2c) and varied with depth (a). The properties of X52 steel subjected to SCC using the slow strain rate technique (SSRT) were considered. True stress-strain curves were obtained in air and in an NS4 solution with pHs of 3.5 and 9.5 at temperatures of 25 and 50 °C. According to the SCC index calculated from the mechanical properties of the SSRT, the X52 steel is susceptible to SCC at pH 3.5 and 50 °C. The mechanical properties of the tensile test using the stress-strain curves decreased as the pH and temperature changed, compared to those carried out at room temperature. This was due to the corrosion and hydrogen embrittlement produced by the solution on the X52 steel. The failure pressure is sensitive to the stress-strain curve; if the stress-strain curve decreases, the failure pressure also decreases. Corrosion defects, such as longitudinal cracks in X52 steel, which could be susceptible to SCC in an NS4 solution, decrease the failure pressure (Pf) and its capacity to withstand pressures of up to 75 % in pipe-grade steel that transports hydrocarbons.

Analytical model for evaluating bond strength of steel rebar in cracked concrete considering confinement effect

This study delves into the intricate relationship between concrete cracking and bond strength, a critical factor in transferring forces between concrete and steel rebars. While previous research has often overlooked the impact of concrete cracking on bond strength and overestimated the beneficial effects of external confinement, this study aims to fill these gaps. A new failure criterion is introduced to predict bond strength of steel rebar in cracked concrete, considering the influence of concrete crack roughness and steel rebar surface features on force transfer at their interface. This criterion incorporates an interlock capacity coefficient that considers crack kinematics and the mentioned factors, enhancing the evaluation of effective compressive strength of cracked concrete in the limit analysis. Leveraging the Mohr-Coulomb failure criterion, an adaptable failure criterion accounts for crack kinematics, concrete damage, and confinement level to assess force transfer at the concrete/steel rebar interface. The developed criterion offers a practical calculation method to estimate bond strength in cracked reinforced concrete (RC) members with various confinement setups. Validation of this criterion and approach involved comparison against experimental results from 127 specimens, confirming its effectiveness and reliability in predicting bond strength in real-world scenarios.

Chloride-Induced Stress Corrosion Cracking of Friction Stir-Welded 304L Stainless Steel: Effect of Microstructure and Temperature

Dry storage canisters of used nuclear fuels are fabricated using SUS 304L stainless steel. Chloride-induced stress corrosion cracking (CISCC) is one of the major failure modes of dry storage canisters. The cracked canisters can be repaired by friction stir welding (FSW), a low-heat input ‘solid-phase’ welding process. It is important to evaluate the ClSCC resistance of the friction stir welded material. Stress corrosion cracking (SCC) studies were carried out on mill-annealed base materials and friction stir welded 304L stainless U-bend specimens in 3.5% NaCl + 5 N H2SO4 solution at room temperature and boiling MgCl2 solution at 155 °C. The engineering stress on the outer fiber of the FSW U-bend specimen was ~60% higher than that of the base metal (BM). In spite of the higher stress level of the FSW, both materials (FSW and BM) showed almost similar SCC failure times in the two different test solutions. The SCC occurred in the thermo-mechanically affected zone (TMAZ) of the FSW specimens in the 3.5% NaCl + 5 N H2SO4 solution at room temperature, while the stirred zone (SZ) was relatively crack-free. The failure occurred at the stirred zone when tested in the boiling MgCl2 solution. Hydrogen reduction was the cathodic reaction in the boiling MgCl2 solution, which promoted hydrogen-assisted cracking of the heavily deformed stirred zone. The emergence of the slip step followed by passive film rupture and dissolution of the slip step could be the SCC events in the 3.5% NaCl + 5 N H2SO4 solution at room temperature. However, the slip step height was not sufficient to cause passivity breakdown in the fine-grained SZ. Therefore, the SCC occurred in the partially recrystallized softer TMAZ. Overall, the friction-stirred 304L showed higher tolerance to ClSCC than the 304L base metal.

Effect of Ultrasonic Shot Peening on Microstructure and Corrosion Properties of GTA-Welded 304L Stainless Steel

Austenitic stainless steels used in structural applications suffer from stress corrosion cracking due to residual stresses during welding. Much research is being conducted to prevent the stress corrosion cracking of austenitic steels by inducing compressive residual stresses. One method is ultrasonic shot peening (USP), which is used to apply compressive stress by modifying the mechanical properties of the material’s surface. In this study, 304L stainless steel was butt-welded by gas tungsten arc welding (GTAW) and subsequently subjected to compressive residual stress to a depth of 1 mm from the surface by a USP treatment. The influence of USP on microstructural changes in the base metal, the HAZ and weldment, and the corrosion properties was analyzed. A microstructural analysis was conducted using SEM-EDS, XRD, and EBSD methods alongside residual stress measurements. The surface and cross-sectional corrosion behavior was evaluated and analyzed using a potentiodynamic polarization test, electrochemical impedance spectroscopy (EIS) measurements, a double-loop electrochemical potentiokinetic reactivation (DL-EPR) test, and an ASTM A262 Pr. C test. The surface was deformed and roughened by the USP. The deformed areas formed crevices, and the inside of the crevices contained some cracks. The crevices and internal cracks caused pitting, which reduced the resistance of the passivation film. The cross-section was subjected to compressive residual stress to a depth of 1 mm from the surface, and the outermost area of the cross-section had fine grain refinement, forming a solid passivation film that improved the corrosion resistance.

Relating rolling contact fatigue (RCF) life to the microstructure evolution in aerospace grade bearing steels: A comparison of Cronidur-30 with AISI 440C

This article presents an extensive analysis of the microstructural evolution under various heat treatment conditions, mechanical properties (hardness), and rolling contact fatigue (RCF) life assessment and sub-surface crack analysis are studied on high nitrogen bearing steel Cronidur-30(Cr-30). An optimum solutionising temperature range has been identified which ensures desirable hardness as well as low retained austenite content. The microstructure consists of primary M2 (C, N) and secondary M23C6 carbides. Sizes of carbides in Cr-30 are significantly smaller than in AISI 440C and this plays a critical role in enhancing the RCF life of Cr-30. A larger area fraction of fine carbides results in branches and subsequent sub-branches of cracks in Cr-30 steel. However, the AISI 440C sample exhibits extensively interconnected cracks due to the presence of larger carbides. The tempering response of Cronidur-30 exhibited a peak hardness of 61 HRC at both lower (150 °C) and higher (475 °C) temperatures. Higher temperature tempering showed L1 life improvement of over 0.5 fold compared to lower temperature tempering.

Evaluation of the “nickel effect” in sulfide stress cracking of low alloy steels

The “nickel effect” refers to the cause of the 1 wt %Ni maximum limit in low alloy steels for the oil and gas production industry to avoid sulfide stress cracking (SSC). The Ni restriction dates to the first edition of the NACE MR 0175/ISO 15156 standard in 1975 and the specific reasons for that limitation remain disputed. This work evaluates the nickel effect with electrochemical tests in the presence and absence of tensile loads at anodic and cathodic potentials and at the open circuit potential (OCP). Thiosulfate was used as a satisfactory alternative to H2S bubbling. The effect of nickel on hydrogen transport and trapping was analyzed with gaseous hydrogen permeation tests. A strong influence of Ni, even at Ni contents below 1 wt%, on SSC initiation at OCP due to trench formation was observed. Compared to other common alloying elements, Ni had a modest role in hydrogen trapping.