Low Carbon Stainless Steel Research Articles

Experimental and numerical study on the cyclic behavior of web dumbbell-shaped damper fabricated of low-yield-point steel

Current double-conical steel dampers, mainly made from low-carbon steel, stainless steel or high-strength steel, do not perform well in terms of fatigue, energy dissipation, and plastic deformation. To address these limitations, this study proposes a web dumbbell-shaped damper fabricated of LYP225 low-yield-point steel (LYP-WDP). This innovation aims to significantly improve the hysteretic behavior and fatigue performance of double-conical steel dampers. Given the limited experimental research on the hysteretic behavior of LYP-WDP under cyclic loading, this study conducts tests to evaluate its performance. Seven full-scale LYP-WDP specimens with different structural parameters were designed using LYP225 steel and subjected to low-cycle loading tests to assess their behavior under shear deformation. The effects of various design parameters on the performance of LYP-WDP were thoroughly analyzed. Finite element models of the specimens were created, and the simulation results were compared with experimental data. Additionally, formulas for calculating the elastic stiffness and yield strength of the LYP-WDP were proposed. The findings reveal that LYP-WDP has high ductility and stable energy dissipation capacity. The elastic stiffness and load-carrying capacity of LYP-WDP increase with the internal shrinkage ratio when the inner diameter and length of the energy dissipation segment are constant, while a negative correlation is found when the outer diameter and length are fixed. Increasing the length of the straight segment greatly enhances the energy dissipation capacity of LYP-WDP. The test results validate the accuracy of the proposed formulas and provide valuable insights for the design and application of LYP-WDP, marking a significant advancement in the field of damping technology.

Development of a Flow Rule Based on a Unified Plasticity Model for 13Cr-4Ni Low-Carbon Martensitic Stainless Steel Subject to Post-Weld Heat Treatment

This study aims to develop a flow rule for evaluating the relaxation and redistribution of residual stresses during the post-weld heat treatment (PWHT) of hydroelectric runners made from low-carbon martensitic stainless steel (13Cr-4Ni composition). During the PWHT, austenite reforms in the filler metal and surrounding areas of the base metal near welded joints. The evolving inelastic strain rate with reformed austenite led to defining two distinct flow rules in the pure martensitic (α′) and austenitic (γ) phases. A linear rule of mixture was then applied to assess global effective stress based on the inelastic strain rate and current austenite fraction during the PWHT. A unified constitutive model incorporating drag stress and back stress, evolving with creep and plastic deformation mechanisms during the PWHT, described the stress–strain behavior. To validate this analysis, a third flow rule was determined in the 18% tempered austenitic microstructure, compared with the rule of mixture’s effective stress contribution from each phase on the inelastic strain rate. Isothermal constant strain rate tests in stabilized crystalline microstructures evaluated constants specific to their respective flow rules. This study demonstrates the stability of reformed austenite at elevated temperatures during slow cooling and its significant influence on the mechanical properties of 13Cr-4Ni steels. The effectiveness of estimating yield stress using the rule of mixture based on individual phase behaviors is also confirmed.

Numerical Simulation of Reversed Austenite Evolution during Intercritical Tempering of Low-Carbon Martensitic Stainless Steel.

Since the formation of reversed austenite during critical tempering treatment is an important factor affecting the mechanical properties of 13Cr4Ni martensitic stainless steel, a detailed study of the content and morphology of reversed austenite in heat treatment is needed. In this study, the variation curves of a reversed austenite volume fraction with holding time at different tempering temperatures were measured by in situ X-ray diffraction (XRD), and the reversed austenite and carbides of each process were evaluated by transmission electron microscopy (TEM). The austenite content shows a parabolic change with the increase in the tempering temperature; the maximum can reach a peak of about 6.8% at 610 °C, and drops to 0% at 660 °C. It also shows a parabolic change with the extension of the holding time, reaching a maximum of about 9.2% at 5 h of holding time, and a decreasing trend at 10 h of holding time, about 6.8%. The results show that the precipitation of carbides in the microstructure causes elemental segregation at grain boundaries and inside, which is one of the main factors affecting the thermal stability of reversed austenite formation. The kinetic process of reversed austenite during the tempering process was simulated using the JMAK model and the KM model, which can describe the trend of reversed austenite content during the tempering process. Combining the two models, a mathematical model for the room-temperature reversed austenite content under different processes was obtained, and this can predict the room-temperature austenite content.

Effect of microstructure on the corrosion-friction behavior of low-carbon martensitic stainless steel

The effect of microstructure on the corrosion-friction behavior of 11Cr4NiMo steel was investigated for three different microstructure states. Quenched martensite and low-temperature tempered martensite with high density dislocations exhibit severe wear under the dual effects of corrosion and abrasion, and their wear mechanism include three-body wear, adhesive wear, and fatigue wear. While high-temperature tempered microstructure mixed structure of tempered martensite, reversed austenite, and M23C6 carbides exhibits weakened wear. Reversed austenite greatly promotes the generation of a dense and stable passivation film with corrosion product of α-FeOOH, and plays a lubricating role and attenuates three-body wear. Utilizing the passivation film induced by corrosion to improve the wear resistance of materials is of great significance in engineering applications.

Corrosion Behaviors’ Investigation of Carbide Coatings Developed for Sulphuric Acid Recovery Systems

In this study, corrosion resistance of cobalt and nickel, which are known to have high corrosion resistance, reinforced tungsten carbide coatings applied to low carbon stainless steel material surfaces to reduce corrosion-induced losses in sulphuric acid recovery systems were investigated. During the recovery of sulphuric acid, aggressive sulphur systems in the baths cause the metal surface to dissolve and therefore a high amount of material loss occurs. In order to minimize corrosion induced material loss, 316 L stainless steel surfaces were coated with an interlayer of 95% nickel and 5% aluminium alloy, and then tungsten carbide coatings were synthesized on the surfaces of substrate materials reinforced with 13% cobalt and 13% nickel, respectively by thermal spraying method to further reduce the corrosion rate. Characterization of the produced coatings were carried out by X-ray diffraction (XRD), scanning electron microscope (SEM), optical microscope, image analyzer, and surface roughness device. The standard potentiodynamic polarization characteristics of the coatings for 1M H2SO4 solution at room temperature were investigated with a potentiostat/galvanostat device. As the obtained results, nickel reinforced tungsten carbide coatings with nickel aluminium interlayer showed the highest corrosion resistance against sulfuric acid environment with 0,41 mm/year corrosion rate. As a result of the article, the corrosion resistance of 316L stainless steels in sulfuric acid systems was improved by 5.02 and 3.15 times, respectively.

Repassivation-oriented pitting corrosion analysis in a cause-effect relationship with microstructure, precipitation, and mechanical behavior of low-carbon medium-chromium ferritic stainless steel

Ferritic stainless steels (FSS), which are potentially ferromagnetic, play a vital role in electromagnetic applications, including solenoid valves, owing to their ferromagnetic properties. This study delves into the microstructure's impact on the localized pitting corrosion behaviour of cold-drawn (CD) low-carbon medium-chromium ferritic/ferromagnetic EN1.4106. Employing potentiostatic-based corrosion analysis, mechanical assessments, and microstructural evaluations on 44 designated specimens subjected to varied annealing conditions, we unveil a nuanced correlation between corrosion resistance and microstructure. Lower reduction rate of 15% versus 45%, extended-enough annealing conditions, and meticulous microstructural control with average grain size of around 45–46 μm, particularly in minimizing dislocation density alongside the local misorientaion of 15° up to at most 35°, significantly enhance corrosion resistance. Overall, this FSS grade demonstrates commendable non-hardenable characteristics with moderate resistance to pitting corrosion in the two of the most corrosive (acidic and chlorinated) environments. The grade notably passivates in sulfuric acid electrolyte solution (SAES) but undergoes active anodic dissolution in sodium chloride electrolyte solution (SCES), ultimately forming a sort of passive-like oxide layer.

Anisotropic ductile fracture of a stainless steel under biaxial loading: Experiments and predictions

The anisotropic ductile fracture behavior of a stainless steel is investigated using a combination of experiments and analysis. The material is SS-304L, an austenitic, low-carbon stainless steel, received in the form of tubes of 2.38 mm dia. and 0.15 mm thickness. The tubes are inflated under volume control in a custom apparatus. At the same time, the axial force on the tubes is kept proportional to the pressure induced by the inflation. This leads to quasi-proportional stress paths in the meridional-hoop engineering stress space. A total of 15 discrete paths are successfully tested. Stereo-type Digital Image Correlation is used to measure the strains. In every case, the tubes develop a series of instabilities before bursting. The failure is oriented along the meridional or the hoop direction of the tube, depending on which stress is greater. A mild plastic anisotropy is detected in these experiments. Hence these results are then used for calibrating the anisotropic yield criterion Yld2004-3D. This is introduced in a finite element model of the experiments, which includes a thickness imperfection designed to capture the two failure orientations observed in the experiments. The numerical model using the Yld2004-3D criterion reproduces the experiments well, e.g., it captures the experimental stress-strain and induced strain paths better than von Mises. It is then used to probe the conditions at the onset of fracture (hybrid method). It is found that most paths lead to essentially proportional loading during deformation. A significant anisotropy in the fracture behavior is detected, with the meridional-stress-dominated paths being able to develop much higher strains than the hoop-dominated ones. These results are then captured by the DF2016 ductile fracture criterion, modified to use the anisotropic yield criterion Yld91. The proposed criterion is flexible enough to represent the fracture anisotropy very well, without being unnecessarily complex. The fracture forming limit curve (i.e., the fracture envelope in strain space) predicted by the DF2016/Yld91 model is also found to be very close to the experiments. The results and findings of this work help establish a framework to reliably design components and processes when significant fracture anisotropy is expected.

Visualization and Location Determination of Pit Initiation Sites in Martensitic Stainless Steel during Corrosion-Fatigue Cyclic Plastic Deformation

Low-carbon martensitic stainless steels, such as 13%Cr4%Ni, are widely used in manufacturing hydraulic turbine runners. High tensile strength steel, such as cast CA6NM or wrought S41500 martensitic stainless steel, has an acceptable resistance to corrosion and cavitation, and reduces the weight and cost while offering a more efficient design. During operation, the combined effect of cyclic loading (fatigue) and corrosion reduces the fatigue strength and can initiate cracks at localized corrosion surface defects.In this study, we determined the bulk and localized corrosion behavior of wrought (S41500) and cast (CA6NM) 13%Cr4%Ni stainless steel before and after plastic deformation.Susceptibility to pitting corrosion was studied using open circuit potential and potentiodynamic polarization measurements in 0.020 M NaCl. Localized corrosion behavior was studied using a scanning droplet cell (SDC) and oil immersed scanning electrochemical cell microscopy (OI-SECCM). The bulk and localized electrochemical measurements after different surface preparation methods (mechanical polishing, followed by etching or electro-etching in different media) were compared.The surface defects including micro-voids and inclusions of different types were characterized. The location of pit initiation was then determined using scanning electron microscopy and profilometry imaging. A three-electrode microcell with a working electrode of 1 mm² was designed and hyphenated with optical microscope to allow in situ tracking of pit initiation and growth. Chronopotentiometry and chronoamperometry controlled pit initiation, while optical microscopy demonstrated dynamic release of corrosion products and measured oxide repassivation kinetics.Finally, the in situ technique was developed further to include a microtensiometer fatigue apparatus to study the synergy effect between corrosion and fatigue. Location of pit initiation was compared with and without plastic deformation. Videos of pit initiation and growth will be presented.

Localised Web Bearing Behaviour of Cold-Formed Austenitic Stainless-Steel Channels: Review of Design Rules and New Insight under Interior Loading

Stainless steels are modern high-performance construction materials exhibiting excellent corrosion resistance, recyclability, ductility, and durability which make them appealing to use in the construction industry. However, when used as structural sections, they are subjected to localised failure in the web. This study aims to examine the structural behaviour of cold-formed low-carbon content standard austenitic 304L and 316L stainless steel channels under localised interior bearing loads. The results of 21 tests on unlipped channels with different cross-section sizes and thicknesses are presented. A nonlinear quasi-static Finite Element (FE) model is then developed. The FE model is validated against experimental test results and demonstrated good agreement in terms of bearing strength and failure modes. In addition, the experimental and FE results are used to compare the results against the results predicted in accordance with the American specification SEI/ASCE 8:2002 and European Standard EN 1993-1-4:2006. It is found that the current design equations are unreliable and too unconservative to use for cold-formed austenitic stainless steel unlipped channels, especially when compared to SEI/ASCE 8:2002, as much as 41%.

The Phase Transformation in a Low-Carbon 13Cr4Ni Martensitic Stainless Steel during Two-Stage Intercritical Tempering

The microstructure evolution of a low-carbon 13Cr4Ni martensitic stainless steel during two-stage intercritical tempering at 630 °C and 590 °C has been investigated by X-ray diffraction, thermodilatometry, and transmission electron microscopy. It was found that the amount and size of reversed austenite increase remarkably after second-stage tempering at 590 °C. However, there is no remarkable variation in the chemical composition and nucleation site of the reversed austenite during the first- and second-stage tempering. The dynamics of the phase transformation and elements distribution imply that the martensite-to-austenite phase transformation during second-stage tempering is controlled by diffusion. The unstable austenite transformation into martensite during the cooling process of the first-stage tempering induces high density dislocations and inhomogeneous element distribution, which facilitate the nucleation and growth of the reversed austenite in the second-stage intercritical tempering. Additionally, some lathy reversed austenite spheroidizes to granular during second-stage tempering.

Detecting balling defects using multisource transfer learning in wire arc additive manufacturing

Abstract Wire arc additive manufacturing (WAAM) has gained attention as a feasible process in large-scale metal additive manufacturing due to its high deposition rate, cost efficiency, and material diversity. However, WAAM induces a degree of uncertainty in the process stability and the part quality owing to its non-equilibrium thermal cycles and layer-by-layer stacking mechanism. Anomaly detection is therefore necessary for the quality monitoring of the parts. Most relevant studies have applied machine learning to derive data-driven models that detect defects through feature and pattern learning. However, acquiring sufficient data is time- and/or resource-intensive, which introduces a challenge to applying machine learning-based anomaly detection. This study proposes a multisource transfer learning method that generates anomaly detection models for balling defect detection, thus ensuring quality monitoring in WAAM. The proposed method uses convolutional neural network models to extract sufficient image features from multisource materials, then transfers and fine-tunes the models for anomaly detection in the target material. Stepwise learning is applied to extract image features sequentially from individual source materials, and composite learning is employed to assign the optimal frozen ratio for converging transferred and present features. Experiments were performed using a gas tungsten arc welding-based WAAM process to validate the classification accuracy of the models using low-carbon steel, stainless steel, and Inconel.

Effect of laser shock processing on residual stress evolution in martensitic stainless steel multi-pass butt-welded joints

Laser shock processing (LSP) is an innovative approach, which effectively improves the mechanical behavior of metallic structures by introducing compressive residual stress. To evaluate the residual stress evolution in low-carbon 13Cr4Ni martensitic stainless steel multi-pass butt-welded joints induced by LSP, a two-step numerical simulation including welding analysis, at first, followed by LSP calculation with the simulated welding stress results being taken into account, was performed based on ABAQUS software. Effects of LSP parameters such as power density, spot size, overlapping rate and numbers of laser shock on the residual stress variations, were systematically investigated. To validate the reliability and accuracy of the numerical simulation, experiments of welding and LSP were conducted in sequence. The residual stress after welding and LSP were investigated by x-ray diffraction method. Results demonstrate that the simulated results show a good agreement with the experimental datas. The welding residual stress distribution is uneven. Larger tensile stresses appear on the weld surface and its adjacent heat-affected zone, which could be converted into high-level compressive stress after LSP. Furthermore, an ideal residual stress field can be obtained after two successive laser shocks with an overlap rate of 75% when the power density, spot diameter, and pulse width are 7.6 GW cm−2, 4 mm, and 25 ns, respectively.

Comparative Study on the Elongation of Low-Carbon Steel and Stainless Steel at Different Creep Temperatures

Creep at high temperature leads to gradual deformation under constant loads. In this paper, a comparative study of the fatigue effect of stainless steel and low carbon steel was made, whereby each sample had a constant weight of 24 kg and the experiments on elongation were performed at temperatures 660℃, 700℃, and 740℃ at a constant time of 10 minutes for each experiment. It was found that the highest elongation rate found to be 0.76% for stainless steel metal at a temperature of 740℃. On the other hand, the amount of elongation for low-carbon steel metal at the same temperature found to be 1.9%. This difference in the amount of elongation observed due to the difference in the microstructure of the two metals. The hardness test showed that the maximum value for stainless steel specimens found to be 225 BHN at 660℃, while for low carbon steel specimens 106BHN at 660℃.

Effect of Cu on the Microstructure and Mechanical Properties of a Low-Carbon Martensitic Stainless Steel.

Reversed austenite is of vital importance in low-carbon martensitic stainless steel because it improves impact toughness. However, a proper amount of reversed austenite is obtained by tempering at a critical temperature, which reduces the strength of the steel. Therefore, how to improve strength-toughness matching is an important problem. Copper (Cu) is an effective strengthening element in steels. However, there is little in-depth discussion on the role of Cu on the microstructure and mechanical properties of low-carbon martensite steel. In this work, the effect of different Cu content on the reversed austenite formation, tensile strength, and impact toughness of a low-carbon martensitic stainless steel (0Cr13Ni4Mo) was systematically investigated through use of a transmission electron microscope (TEM), transmission Kikuchi diffraction (TKD), atom probe tomography (APT), and other characterization methods and mechanical property tests. The results showed that the addition of Cu decreased the phase transition temperatures of martensite and austenite and increased the volume fraction of the reversed austenite. APT results indicated that Cu-rich clusters first formed with alloying elements such as ferrum (Fe) and nickel (Ni) and then grew to be precipitates through rejection of the alloying elements. The Ni atoms diffused towards the interface between the precipitates and the martensite matrix, which provided heterogeneous nucleation sites for the reversed austenite. Cu precipitations strengthened tensile strength during tempering. However, it generated temper brittleness in the steel at a tempering temperature of 450 °C, resulting in the impact energy of the 3Cu-steel being only 7 J. A good combination with higher tensile strength (863 MPa) and ductility (192 J) was obtained when tempering at 600 °C in the presence of Cu-rich precipitates and a sufficient volume fraction of the reversed austenite. The results provide guidance for the design of steels with reversed austenite and Cu and promote the development of high-strength and high-toughness steels.

Fatigue Crack Growth Behavior of Nitrogen-Alloyed Low-Carbon Austenitic Stainless Steel at Room Temperature

Fatigue Crack Growth Behavior of Nitrogen-Alloyed Low-Carbon Austenitic Stainless Steel at Room Temperature

Unified viscoplasticity model for type 316 stainless steel subjected to isothermal and anisothermal-mechanical loading

316FR-type low carbon stainless steel is usually used for many advanced gas cooled reactor (AGR) power plants which are subjected to operating temperatures in the range of 500–650 °C under thermo-mechanical loading, which may lead to isothermal low cycle fatigue (LCF) and thermal mechanical fatigue (TMF) damage. The strain controlled thermo-mechanical fatigue test with and without holding time was carried out for 316FR-type stainless steel under the temperature cycling between 500 °C and 650 °C, and the strain ranges are Δε = ± 0.4%, ±0.8%, ±1.0% and ±1.2%, respectively. Within the framework of Abdel Karim and Ohno model, an improved unified viscoplastic constitutive model (UVM) is proposed to simulate the cyclic plastic behavior of 316FR stainless steel. The improved UVM includes strain rate sensitivity, temperature rate dependence, static recovery, average stress evolution and strain range dependence of cyclic hardening. And then based on the radial return mapping and backward Euler integration methods, the implicit stress integration algorithm and the new expressions of the consistent tangent modulus are derived respectively, the improved UVM is implemented by a User Material Subroutine into ABAQUS software again. The good correlation between simulation results and experimental data is obtained.

CARTECH 316/316L

Abstract CarTech 316/316L is a chromium-nickel-molybdenum austenitic stainless steel. It is a low-carbon version of the conventional CarTech 316. In this low-carbon austenitic stainless steel, control of carbon to 0.03 % has been shown to minimize carbide precipitation during welding. CarTech 316/316L can be used in the as-welded conditions in a variety of corrosive applications. This datasheet provides information on composition, physical properties, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: SS-1353. Producer or source: Carpenter Technology Corporation.

Electrochemical characterization of 13Cr low-carbon martensitic stainless steel - corrosion study with a mini-cell setup

13Cr low-carbon martensitic stainless steels also known as supermartensitic stainless steels (SMSS) have superior properties than conventional martensitic stainless steels. The SMSS have better weldability and corrosion resistance. Nevertheless, corrosion resistance depends on phases transformations which are induced generally by heat treatments. In this work, the electrochemical properties of a SMSS were evaluated as a function of the tempering temperature (400 °C–700 °C). The susceptibility to intergranular corrosion was determined throught the degree of sensitization (DOS) using the Double Loop - Electrochemical Potentiokinetic Reactivation technique (DL-EPR) in a conventional three electrodes corrosion cell. On the other hand, the pitting susceptibility was evaluated by potentiodynamic polarization using a homemade corrosion mini-cell (based on a sessile electrolyte droplet), thus avoiding crevice problems typically seen with conventional arrangements. Imaging the microstructure with SEM, XRD analysis and thermodynamic and kinetic simulations were performed to understand the microstructural transformations and their relationship with corrosion resistance. The most severe sensitization occurs at the temperature where reversed austenite transformation is highest.

Extreme high-speed-rate laser directed energy deposition of high strength low carbon stainless steel coating with layered heterogeneous structure

In this work, a ferritic stainless steel coating was manufactured via extreme high-speed-rate directed energy deposition (EHLDED). Microstructural features and tensile behavior were investigated and analyzed. The microstructural analysis confirmed that EHLDED coating was characterized by alternating patterns of columnar dendrites and fine equiaxed dendrites. The average size of the dendrites was less than 1 μm. High-resolution transmission electron microscopy showed that there were a large number of dislocation lines (DLs) and dislocation tangles (DTs) enriched at inter-dendritic solidification structures attributed to the ultrahigh cooling and solidification as well as molten pool movement. In addition, a small percentage of predominantly nanosize carbides with the size ranging from 50 to 90 nm were also observed in dendrites and inter-dendritic solidification structures. The EHLDED coating sample manufactured at the deposition speed of 40 m/min showed a higher strength of 1084 MPa with the ductility 1.27%. Results reveal that the ultra-fine dendrites accompanied with nanosize carbides prepared by EHLDED contributed to achieving high strength of low carbon stainless steel coatings.

Flower-like Superhydrophobic Surfaces Fabricated on Stainless Steel as a Barrier against Corrosion in Simulated Acid Rain.

Functionalisation of the metal surface of low-carbon ferritic stainless steel (from hydrophilic to hydrophobic properties) was achieved by flower-like hierarchical structures on a steel substrate prepared by a low-cost immersion method. The flower-like structured hydrophobic layers on the steel substrate were obtained by immersing the samples in an ethanolic solution of stearic acid with the addition of various concentrations of expired vitamin E ((+)α-tocopherol). The stability and corrosion-inhibiting effect of the hierarchically structured (such as natural cornflower) hydrophobic layers were studied systematically during short and long immersion tests, 120 h (five days) in an acidic environment (pH = 3) using potentiodynamic measurements, electrochemical impedance spectroscopy and chronopotentiometry. The surfaces of the samples, their wettability, surface morphology and chemical composition were characterised by contact angle measurements, SEM, ATR-FTIR and EDAX. After 120 h of immersion, the inhibition efficiency of the flower-like structured hydrophobic layers on the steel substrate in the selected corrosion medium remained above 99%, and the hierarchical structure (flower-like structure) was also retained on the surface.