High Strength Low Alloy Research Articles

Effect of Hydrodynamic Conditions on the Corrosion Mechanism of HSLA X100 Steel by EIS and EN Analysis

In this research work, the influence of the electrolyte hydrodynamic conditions on the corrosion mechanism of the high-strength low-alloy (HSLA) X100 steel used in the petroleum transportation pipelines was analyzed. A Rotary Cylinder Electrode (RCE) was used to simulate the hydrodynamic conditions (1000 and 5000 rpm). Mechanical, microstructural and elemental characterization tests were performed on X100 steel, and the electrochemical impedance spectroscopy (EIS) technique was used to analyze the corrosion mechanism, while the morphology of the corrosion process on the corroded surfaces was obtained by scanning electronic microscopy (SEM). It was found that the increasing rotation rate (υ rot) generates a fully developed flow regime where the system was dominated by a mass transfer process and increases the kinetics of chemical and electrochemical reactions so there is an increase in the corrosion rate (CR). On the other hand, the adsorption of corrosion product films that limits the charge transfer process depended on the magnitude of the shear stress that can generate wear and roughness, as well as a greater number of anodic sites, leaving the metal exposure to the corrosive medium.

Development of a Finite Element Model for the HAZ Temperature Field in Longitudinal Welding of Pipeline Steel

In this study, a novel hybrid heat source model was developed to simulate the welding temperature field in the heat-affected zone (HAZ) of X80 pipeline steel. This model replicates welding conditions with high accuracy and allows flexible three-dimensional adjustments to suit various scenarios. Its development involved the innovative integration of microstructural crystallography information with a multi-scale calibration and validation methodology. The methodology focused on three critical aspects: the weld interface morphology, the location of the Ac1 temperature, and the size of prior austenite grains (PAG). The morphology of the weld interface was calibrated to align closely with experimental observations. The model’s prediction of the Ac1 location in actual welded joints exhibited a deviation of less than ±0.3 mm. Furthermore, comparisons of reconstructed PAG sizes between thermal simulation samples and actual HAZ samples revealed minimal discrepancies (5 μm). Validation results confirmed that the calibrated model accurately describes the welding temperature field, with reconstructed PAG size differences between simulation and experimental results being less than 9 μm. These findings validate the accuracy of the calibrated model in predicting welding temperature fields. This research introduces a novel framework for the development of heat source models, offering a robust foundation for improving welding performance and controlling microstructure in different regions during the welding process of high-strength low-alloy (HSLA) steel.

Thermodynamically consistent damage evolution model coupled with rate-dependent crystal plasticity: Application to high-strength low alloy steel at various strain rates

Thermodynamically consistent damage evolution model coupled with rate-dependent crystal plasticity: Application to high-strength low alloy steel at various strain rates

Parametric Optimisation of Wire Electrical Discharge Machining of 15CDV6 HSLA Steel Using Taguchi Method

15CDV6 steel is a high strength bainitic High Strength Low Alloy (HSLA) steel with low concentrations of chromium, molybdenum, and vanadium as the main alloying constituents. This steel is very robust and well-tempered i.e., it has High strength and good toughness. It is used in the manufacture of transformers, electric motors, nuclear reactors, and its application to the aerospace industry for the manufacture of rocket motor cases is immense. Simplifying any process of machining is very difficult, since it basically includes forecasts of machining parameters and working requirements that are unpredictable and extremely non-linear in nature which influence the overall production Quality and costs. A key component of producing novel products, particularly for the automotive and aerospace sectors, is wire electro discharge machining (Wire-EDM). This technology got success and offers unique advantages for specific applications, such as working with hard, super-tough, brittle, or difficult-to-machine materials, producing intricate shapes, or achieving high precision. The high degree of the obtainable accuracy and the fine surface quality makes Wire-EDM valuable. The right selection of the process parameters or input variables is the considered as most important task in Wire Electro Discharge Machining of 15CDV6 HSLA steel material. The present work concentrates on optimisation of various process parameters are Pulse-on Time, Pulse-off Time, Water pressure and sensitivity on work material 15CDV6 HSLA steel, the output responses considered are Material Removal Rate (MRR), Surface Roughness (Ra), and Power Consumption (PC). Taguchi Method technique used on experimental results for optimisation and same results are analysed using Analysis of Variance (ANOVA) for identify percentage contribution of process parameters. This work helps in analysing the suitable process parameters and machining performance for machining of 15CDV6 steel and also reveals the research work area in which maximum research work can be done in future.

Assessment on wire-arc additive manufactured high strength low alloy steel cylindrical component

Large structural parts are widely manufactured through wire-arc additive manufacturing (WAAM) due to its high deposition rate, flexibility, and low cost. There are a variety of industries where high strength low alloy (HSLA) steel is used, including naval, tool and die manufacturing, construction, and offshore structures. The present article examines the mechanical properties and microstructural evolution of a developed HSLA component. The microstructural analysis was done in the component’s top (TR) and bottom (BR) regions. It reveals almost similar microstructural constituents but with more polygonal ferrite in the TR and bainitic structure in the bottom, with acicular ferrite in both regions. The inclusions in both regions were characterized using energy-dispersive X-ray spectroscopy. This demonstrates that manganese (Mn), as a strong deoxidizer, reacts with oxygen and dissolves entirely within the inclusion, forming a Mn depletion zone. Additionally, grain coarsening was observed in the building direction. The average grain size in the TR and BR was 13.12 μm and 6.54 μm, respectively. Within the regions considered, only 2.47%, 4.06%, and 0.65% variations were observed between yield strength, ultimate tensile strength, and elongation to fracture.

Fracture and Fatigue Crack Growth Behaviour of A516 Gr 60 Steel Welded Joints

The facture and fatigue behaviour of welded joints made of A516 Gr 60 was analysed, bearing in mind their susceptibility to cracking, especially in the case of components which had been in service for a long time period. With respect to fracture, the fracture toughness was determined for all three zones of a welded joint, the base metal (BM), heat-affected zone (HAZ) and weld metal (WM), by applying a standard procedure to evaluate KIc via based on JIc values (ASTM E1820). With respect to fatigue, the fatigue crack growth rates were determined according to the Paris law by the standard procedure (ASTM E647) to evaluate the behaviour of different welded joint zones under amplitude loading. The results obtained for A516 Gr. 60 structural steel showed why it is widely used in the case of static loads, since the minimum value of fracture toughness (185 MPa√m) provides relatively large critical crack lengths, whereas its behaviour under amplitude loading indicated a need for further improvement in WM and HAZ, since the crack growth rate reached values as high as 4.58 × 10−4 mm/cycle. In addition, risk-based analysis was applied to assess the structural integrity of a pressure vessel, including comparison with the high-strength low-alloy (HSLA) steel NIOVAL 50, proving once again its superior behaviour under static loading.

Proposal of an alternative method for residual stress measurements in clad nickel alloy after shot peening

Cladding of Ni-based superalloy 625 is often used to enhance mechanical resistance and corrosion performance of the high strength low alloy pipeline, for use in CO2 injection units in oil wells. It is well known that the use of the shot peening can improve its properties by creating a thin surface layer with compressive residual stresses. In this regard, the aim of this work is to propose an alternative method to evaluate the residual stresses of clad Ni-based superalloy 625 based on the deflection measurements of a thin strip separated from the shot peened samples by EDM cutting. The stress distribution in shot peened layer was measured by XRD sin2ψ method with electrolytic removal of surface layers. Measurements by the alternative and XRD method showed that the difference between the average stress values determined by these methods is 4%.

Numerical Simulation of Fatigue Crack Growth and Fracture in Welded Joints Using XFEM-A Review of Case Studies.

Numerical simulation of fatigue crack growth in welded joints is not well represented in the literature, especially from the point of view of material heterogeneity in a welded joint. Thus, several case studies are presented here, including some focusing on fracture, presented by two case studies of mismatched high-strength low-alloyed (HSLA) steel welded joints, with cracks in the heat affected zone (HAZ) or in weld metal (WM). For fatigue crack growth, the extended finite element method FEM (XFEM) was used, built in ABAQUS and ANSYS R19.2, as presented by four case studies, two of them without modelling different properties of the welded joint (WJ). In the first one, fatigue crack growth (FCG) in integral (welded) wing spar was simulated by XFEM to show that its path is partly along welded joints and provides a significantly longer fatigue life than riveted spars of the same geometry. In the second one, an integral skin-stringer panel, produced by means of laser beam welding (LBW), was analysed by XFEM in its usual form with stringers and additional welded clips. It was shown that the effect of the welded joint is not significant. In the remaining two papers, different zones in welded joints (base metal-BM, WM, and HAZ) were represented by different coefficients of the Paris law to simulate different resistances to FCG in the two cases; one welded joint was made of high-strength low-alloyed steel (P460NL1) and the other one of armour steel (Protac 500). Since neither ABAQUS nor ANSYS provide an option for defining different fatigue properties in different zones of the WJ, an innovative procedure was introduced and applied to simulate fatigue crack growth through different zones of the WJ and evaluate fatigue life more precisely than if the WJ is treated as a homogeneous material.

Through a Controlled Quenching to Achieve a Good Combination of Mechanical Properties in Low‐Yield Ratio 900 MPa High‐Strength Low‐Alloy Steels

Two distinct heat treatments, that is, intercritical quenching combined with low‐temperature tempering (QT) to control the initial quenching temperature, and salt‐bath quenching combined with partitioning (Q&P) to regulate the final quenching temperature, were employed on high‐strength low‐alloy (HSLA) steels to achieve multiphase microstructures characterized by high strength, low yield ratio, and good impact toughness. Comprehensive experiments involving tension test, low‐temperature impact, microstructural observation, and in situ tension have been conducted to compare the microstructures and mechanical properties. It is found that both kinds of specimens can achieve a good match between high strength‐toughness and low yield ratio. The microstructures are composed of lath martensite with ferrite for QT specimen and tempered martensite with bainite for the Q&P specimen, a combination of “soft” and “hard” phases thus resulting in a yield ratio lower than 0.85 for 900 MPa low‐alloy steels. Notably, the Q&P specimen exhibited a markedly superior uniform elongation of 6.1% compared to the QT counterpart of 3.2%, a phenomenon attributed to the work hardening rate during deformation. A combination of strong and weak lath structures in tempered martensite and bainite can induce dislocation propagation and the carbides can act as obstacles to dislocation motion, jointly enhancing work hardening.

Effect of Rapid Heating and Quenching on Microstructure and Mechanical Properties of High Strength Low Alloy Steel

Effect of Rapid Heating and Quenching on Microstructure and Mechanical Properties of High Strength Low Alloy Steel

Effect of Heat Treatment on Impact Transition Temperature of High Strength Low Alloy Steel (HSLA) Steel Rods

This study is carried out to investigate the ductile to brittle fracture behavior of special high strength low alloy steel (HSLA), which is used in aerospace applications. As aerospace materials are subjected to temperature variations during their actual use therefore it is very important to know their fracture behavior with change of temperature. Alloy having 0.3 %C, 0.88 % Mn and 1.0% Si was heat treated to obtain tempered martensite and ferrite and tempered martensite structures. Impact toughness tests were carried out at temperature range from – 60 °C - 200 °C in as received, fully quenched, and tempered and quenched and tempered in two phase (a+ γ) state. Then the effect of different heat treatments on impact transition temperature was studied.

Achieving superior aluminum-steel dissimilar joining via ultrasonic spot welding: Microstructure and fracture behavior

High-strength dissimilar welded joints of AA2024-T3 alloy with an AA1230 coating and galvanized high-strength low-alloy (HSLA) steel were attained through ultrasonic spot welding (USW) in this study. The tensile lap shear failure loads over a welding energy range between 2000 J and 3000 J were observed to meet or surpass the values specified in the AWS D17.2 standard. The highest average tensile lap shear strength was obtained to be ∼169 MPa due to the formation of a ∼30–70 μm thick Al-Zn diffusion layer without the presence of intermetallic compounds. The substrate failure from the softer AA1230 coating on the AA2024 side under tensile loading and cyclic loading at higher cyclic loads was observed, which reflected a robust sticking capability. The partial failure from AA1230 coating consisted of characteristic shear dimples, allowing high plasticity upon shear deformation. While the 1000 J welds failed mainly via substrate failure from AA1230 and transverse through-thickness (TTT) cracking in AA2024, the cohesive failure across the Al-Zn diffusion layer and adhesive failure from the Al-Fe-intermetallic/Al-Zn-diffusion layer interface were observed in the welds made at 3000 J, corresponding to the superior bonding strength and longer fatigue life.

Effects of heat input on microstructure evolution and corrosion resistance of underwater laser cladding high-strength low-alloy steel coating

The effects of heat input on the microstructure evolution and corrosion resistance of the high-strength low-alloy (HSLA) steel coating obtained by wire-feed underwater laser cladding were studied. Optical digital microscope, scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), transmission electron microscope (TEM), electron back-scattered diffraction (EBSD), electrochemical tests, laser microscope and other characterization methods were used. As the heat input increased, the smoothness of the underwater cladding coating improved, with little changes in elemental distribution and phase composition. However, the content of acicular ferrite increased, while the amounts of lath bainite, lath martensite, and granular bainite decreased. As the heat input increased from 0.4 to 0.55 kJ/mm, the grain size increased from 25.3 to 55.9 μm, the proportion of low-angle grain boundaries rose from 61.3 % to 69.1 %, and the texture intensity of the (110) crystal plane increased from 16.22 to 23.83. Meanwhile, the dislocation density decreased from 4.9 × 1014 to 4.1 × 1014 m−2. These changes enhanced the corrosion resistance of underwater coating. As the heat input increased from 0.4 to 0.55 kJ/mm, the corrosion current density decreased from 2.13 × 10−5 to 3.35 × 10−6 A/cm2, and the corrosion potential increased from −0.823 to −0.529 V. Additionally, the depth-to-width ratio of the corrosion pits decreased from 0.255 to 0.053. This study laid the foundation for high-quality in-situ underwater repairs of ships and submarines made of high-strength steel.

Experimental and Numerical Characterization of Local Properties in Laser-Welded Joints in Thin Plates of High-Strength–Low-Alloy Steel and Their Dependence on the Welding Parameters

Laser welding on thin plates of high-strength steel is increasing in various industrial applications. The mechanical behavior of welded joints depends on their local properties, which in turn depend on the welding parameters applied to join the base material. This work characterizes the local properties of butt-welded joints of thin plates of high-strength–low-alloy (HSLA) steel. This study focuses on the effect of welding parameters on the microstructure, tensile response, microhardness, and weld bead profile. For this purpose, a factorial experimental design was formed, covering a heat input range from 53 to 75 J/mm. This study identified the main effects and interactions of welding speed and laser power on the weld bead profile and on its width. The microstructure, weld bead width, hardness, and tensile mechanical properties were significantly influenced by heat input. Furthermore, numerical simulations on real weld bead profiles revealed high values of the stress concentration factor and suggested a correlation with heat input.

Frequency–Time Domain Analysis Based on Electrochemical Noise of Dual-Phase (DP) and Ferrite–Bainite (FB) Steels in Chloride Solutions for Automotive Applications

The automotive industry uses high-strength (HS), low-alloy (HSLA) steels and advanced high-strength steels (AHSSs) to manufacture front and rear rails and safety posts, as well as the car body, suspension, and chassis components of cars. These steels can be exposed to corrosive environments, such as in countries where de-icing salts are used. This research aims to characterize the corrosion behavior of AHSSs based on electrochemical noise (EN) [dual-phase (DP) and ferrite–bainite (FB)]. At room temperature, the steels were immersed in NaCl, CaCl2, and MgCl2 solutions and were studied by frequency–time domain analysis using wavelet decomposition, Hilbert–Huang analysis, and recurrence plots (RPs) related to the corrosion process and noise impedance (Zn). Optical microscopy (OM) was used to observe the microstructure of the tested samples. The results generally indicated that the main corrosion process is related to uniform corrosion. The corrosion behavior of AHSSs exposed to a NaCl solution could be related to the morphology of the phase constituents that are exposed to solutions with chlorides. The Zn results showed that DP780 presented a higher corrosion resistance with 918 Ω·cm2; meanwhile, FB780 presented 409 Ω·cm2 when exposed to NaCl. Also, the corrosion mechanism of materials begins with a localized corrosion process spreading to all the surfaces, generating a uniform corrosion process after some exposition time.

Impact of boron and titanium on the mechanical properties and recrystallization behaviour of low carbon cold rolled and batch annealed HSLA steels

This study investigates the impact of boron (B) on the mechanical properties and recrystallization behaviour of cold rolled and batch-annealed titanium (Ti) microalloyed high-strength low-alloy (HSLA) steels. HSLA steels are essential in industries such as automotive and construction due to their superior mechanical properties and cost-effectiveness. The addition of microalloying elements, particularly Ti, has shown significant promise in enhancing these properties through mechanisms like precipitation strengthening and controlled recrystallization. However, the role of B in this context remains underexplored. Here, three alloy compositions were systematically examined: a reference low carbon steel base alloy with no Ti or B (Ref), the base alloy with added Ti (Ref + Ti), and the base alloy with both Ti and B additions (Ref + Ti + B). The findings showed that microalloying with Ti + B can provide excellent strength improvements in the hot rolled strip, mainly due to increased hardenability that promotes the formation of finer ferrite grains with a high dislocation density. However, the recovery and recrystallization behaviour is such that it is not possible to reproduce these benefits after cold rolling and batch annealing, highlighting the complexity of optimizing microalloying strategies for cold-rolled and batch annealed products. The insights gained from this study provide a deeper understanding of the mechanisms governing the recrystallization of Ti and B microalloyed HSLA steels, paving the way for the development of advanced materials with tailored properties for critical applications.

On the role of the retained porosity on the shock response of additively manufactured high-performance steel: Experiments, constitutive model and finite-element predictions

Experiments have shown that for quasi-static and moderate strain-rates (of the order of 102–103/s) the mechanical response of additively manufactured (AM) and traditionally processed high-strength steels is similar whereas the impact behavior is markedly different. In this paper, we reveal that the main reason for this difference is the retained porosity in the AM material. Fully-implicit finite element calculations are presented in which we simulate both the launching of the impact plate and the impact between the two plates. The constitutive model used is the elastic/plastic model for porous ductile materials with matrix displaying tension-compression asymmetry and Johnson-Cook hardening law that accounts for both strain-rate effects and plastic history. It is shown that even a very small initial porosity changes the wave front, decreases the Hugoniot while increasing the shock rise time, when compared to a void free material. Furthermore, quantitative comparisons between simulation results and plate impact data for both the AM and the wrought AF9628 steel are provided. The good agreement show that the model captures the impact response and illustrates the model capabilities to provide information on field variables that cannot be directly measured.Additive manufacturing (AM) of metals is rapidly advancing as a robust method for production of geometrically complex parts. To enhance understanding of material performance and open up additional application opportunities, dynamic characterization of newly printed alloys is required to validate their effectiveness. In this paper, we present results from plate impact testing of AF9628 steel, a newly developed high-strength low alloy martensitic steel for structural applications which require resistance to high-rate deformation. We put into evidence differences in the shock structure between the AM and the traditionally processed material. To gain understanding, we conduct fully-implicit finite element (FE) calculations in which we model both the launching of the impact plate and the impact between the two plates, respectively. An elastic/plastic damage model that accounts for the effects of the tension-compression asymmetry in plastic deformation and its influence on porosity evolution is used. The FE results reveal that even a very small amount of initial porosity leads to an increase in the shock rise time, explaining the observed trends. Furthermore, quantitative comparisons between simulation results and plate impact data for both the AM and the wrought AF9628 are provided. The good agreement show that the model captures the impact response and illustrates the model capabilities to provide information on field variables that cannot be directly measured.

Assessing strength of ferrite and martensite in five dual phase and two martensitic steels via high throughput nanoindentation to elucidate origins of strength

This paper describes the main findings from an experimental investigation into overall and local strength of four dual-phase (DP) steels classified based on their tensile strength (TS) levels from DP590, to 780, to 980, to 1180, a martensitic steel (MS) 1700, and a high-strength low-alloy (HSLA) steel in rolled and additively manufactured (AM) conditions. The DP steels and the MS steel consist of ferrite and martensite, while the HSLA steel is solely martensitic. High throughput nanoindentation mapping is employed to measure the mechanical hardness of individual phases contributing to strength of the steels. A clustering methodology for correlating measured hardness and phase maps is conceived to infer hardness per phase. With increasing fractions of martensite, the hardness values of both ferrite and martensite are found to increase with more rapid increase in the hardness of ferrite than martensite. The phases increasingly dislocate with the fraction of martensite as rationalized by crystal plasticity modeling of strength of the steels. Initial slip resistances and a set of hardening parameters associated with the slip in ferrite and martensite are established to model the flow stress behavior of the steels. In modeling the co-dependent nature of crystallographic slip in ferrite and martensite, the initial dislocation densities are inferred and correlated with the measured hardness values. The hardness of martensite in the rolled HSLA steel is comparable to the hardness of martensite in the MS steel, while martensite in the AM HSLA steel is softer owing to the tempering occurring during the AM process.

Mechanical and Metallurgical Characteristics of Wire-Arc Additive Manufactured HSLA Steel Component Using Cold Metal Transfer Technique

Recently, the application of wire-arc additive manufacturing (WAAM) for the production of metallic products is gaining traction. WAAM is associated with the direct energy deposition technique and therefore has a higher deposition rate (approximately 4 kg/h). For this reason, it is of greater interest than powder-based additive manufacturing techniques. Industrial applications such as marine and offshore structures and pressure vessels for space programs commonly utilize high-strength low-alloy (HSLA) steel. HSLA steel components produced by casting methods exhibit defects due to oxidation. Therefore, cold metal transfer (CMT)-WAAM was adopted in this study to fabricate HSLA steel components. The metallurgical properties were analyzed using microscopic and diffraction techniques. The effects of the evolved microstructures on mechanical properties, such as strength, microhardness, and elongation to fracture, were evaluated. To analyze and test the structure, two regions were selected, namely, top and bottom. Microstructural analyses revealed that both regions were primarily composed of acicular ferrite, polygonal ferrite, and bainitic structures. The bottom region exhibited superior mechanical properties compared with the top region. The improved strength at the bottom region can be ascribed to the formation of a high density of dislocations and finer grains.

Modeling of Dynamic Recrystallization Kinetics of a High Strength Low Alloy Steel During Hot Rolling

Modeling of Dynamic Recrystallization Kinetics of a High Strength Low Alloy Steel During Hot Rolling