High Strength Low Alloy Steel Research Articles

ANALYSIS ON POWER CONSUMPTION FOR LIFE CYCLE SUSTAINABILITY ASSESSMENT IN HARD TURNING OF AISI 4140 STEEL USING SPPP—AlTiSiN-COATED CARBIDE TOOL UNDER VARIOUS CUTTING ENVIRONMENTS

High strength low alloy (HSLA) AISI grade 4140 is grabbing the eyes of automobile industries for its superior properties. However, the production of finished components of HSLA steel by machining under dry environment is challenging owing to high cutting temperature and friction. The usage of low-cost coated carbide tools and environment-friendly cooling-lubrication approach are thereof being given importance for the past few decades for economic and sustainable machining. In this study, the power consumption (Pc) during the hard turning process of AISI 4140 steel was analyzed using an AlTiSiN-coated carbide tool under various cutting environment conditions, including dry cutting, flooded cutting, and nanofluid-MQL cutting. For this study, the nanofluid was prepared by blending MWCNT nanoparticles with an environmentally friendly automotive radiator coolant, which served as the base fluid. Briefly, the cooling-lubrication performance is investigated by comparing the machining responses like machined surface morphology, tool wear, cutting force, and temperature. The variance analysis was adopted to determine the significance level of experimental parameters (speed, feed, nose radius, depth of cut, cutting environments) affecting the Pc. To predict and optimize Pc during hard turning with machining variables, the response surface method (RSM) was proposed. Following the predictive modeling and optimization, the results were applied for economic assessment and for energy saving carbon footprint evaluation. This innovative research also addresses comparative sustainability evaluation in hard turning under different C/L environments using life cycle assessment (LCA) towards cleaner and safer production. Results indicate that cutting speed was the most influential item on Pc enhancement. Furthermore, as compared to dry and flooded turning, lower cutting force, reduced cutting temperature, shorter width of flank wear, and better surface morphology are obtained under nanofluid-MQL machining. It is experienced that nanofluid-MQL machining outperformed towards sustainability improvement concerning techno-economically viable societal acceptable and environment friendliness.

Influence of High-Strength, Low-Alloy Steel on Fatigue Life at a Non-Load-Bearing Transverse Welded Attachment

<div>This study investigated the influence of high-strength low-alloy steel on the fatigue life of a load-bearing member with a non-load-bearing transverse welded attachment (T-joint). It compared high cycle fatigue data to two fatigue design codes, namely BS 7608 and Eurocode EN 1993-1-9. Different base and filler material combinations of varying material strengths were investigated, resulting in a total of three different specimen configurations. Two material combinations had a high-strength steel (Strenx<sup>®</sup> 700 MC D) for the base material, with one combination having a matched filler material and the other having an undermatched filler material. The third material combination had a lower-strength steel (S 355 JR AR) for the base material, with a matched filler material. Tensile tests were performed to confirm the base material mechanical properties and weld quality of the manufactured specimens. The investigation showed that there was no significant benefit to using high-strength steel as the base material for a fatigue loaded T-joint with a non-load-bearing welded attachments.</div>

Achieving enhanced cryogenic toughness in a 1 GPa grade HSLA steel through reverse transformation of martensite

The effect of microstructure on crack resistance and cryogenic toughening in a 3.5 wt% Ni high-strength low-alloy (HSLA) steel was investigated. Multistage heat treatments involving quenching (Q), lamellarization (L), and tempering (T) were applied to prepare the HSLA steels with various microstructures, focusing on the reverse transformation and reconfiguration of martensite, as well as its influence on impact crack formation and propagation behavior by multi-scale characterizations. The results indicate that lamellarization treatment has little influence on tensile properties, but significantly improves impact toughness in the QL and QLT specimens, which exhibit over 30 % increment in Charpy V-notch (CVN) absorbed energy Et tested in range from RT to −196 °C, over 25 °C decrement in ductile-brittle transition temperature (DBTT), and much higher crack propagation energy Ep and higher ratio of Ep/Et, as compared with the as-quenched (AQ) and QT specimens. The lamellarization treatment also contributes to a significant refinement effect on martensitic block size, caused by fresh martensite transformation from the reversed austenite, resulting in an increment in high angle grain boundaries (HAGBs), with introduction of a small amount of retained austenite (RA) as well. Therefore, the impact crack resistance and cryogenic toughness is improved in specimens processed with lamellarization treatment, due to the enhancement in crack deflection and hindering effect of the HAGBs, as well as toughening effect by in situ austenite-to-martensite transformation of the RA. Based on the present study, a 1 GPa grade HSLA steel with high ductility and excellent cryogenic toughness can be produced.

Site-specific analysis of precipitates during the coiling of an HSLA steel containing V and Nb

Precipitation in a high-strength low-alloy steel containing V and Nb additions during coiling at 500 °C, was investigated by advanced characterization techniques including electron backscattered diffraction, focused ion beam, transmission electron microscopy and atom probe tomography. During coiling, nano precipitates were preferentially formed around dislocations and grain/sub-grain boundaries in the high Kernel Average Misorientation (KAM) areas associated with bainite. Precipitates were frequently observed around cementite in the low KAM areas with cementite which were identified as granular bainite. Interphase clusters were found in the low KAM areas associated with ferrite. The site-specific methods reveal the co-existence of different kinds of precipitates. Analysis of the results indicates that the precipitation of microalloy particles close to cementite could lower the precipitation hardening contribution that could be achieved through microalloying.

Effects of tempering temperature on the precipitation behaviors of nanoparticles and their influences on the susceptibility to hydrogen embrittlement of a Cr–Mo–V steel

This paper presents an experimental study of tempering treatment to optimize the precipitation behavior of nano-sized particles for improving the resistance to hydrogen embrittlement (HE) of an AISI 4330-type low-alloy high-strength steel. The precipitates and dislocations in the microstructure, which serve as irreversible and reversible hydrogen traps, were quantitatively investigated using TEM, X-ray diffraction and hydrogen permeation techniques. It was found that V-rich M2C precipitates of less than 2 nm size appeared when tempered at 610 °C, a tempering temperature associated with the lowest HE susceptibility of the tempered steel. Furthermore, the hydrogen could promote movement of the multiple dislocation at the low-temperature tempering process but pin the separated dislocation at higher temperature tempering process. The interaction of the dislocations (i.e., multiple dislocation or separated dislocation) with nanoprecipitates and hydrogen atoms produced the hydrogen-induced hardening/softening behavior in a hydrogen-charging environment.

Quantification and Analysis of Niobium Carbide Precipitation in Cold‐Rolled High‐Strength Low‐Alloy Steel during Annealing Process

High‐strength low‐alloy (HSLA) steels are widely used to their excellent mechanical properties. Despite this, the precipitation process occurring during annealing after cold rolling has not been extensively studied. Herein, the precipitation of niobium carbide (NbC) is examined during both hot‐rolling and annealing processes. Field emission transmission electron microscopy and inductively coupled plasma optical emission spectroscopy are employed for the analyses, with a particular focus on using the residual electrochemical extraction method for quantification. The NbC precipitates formed during hot rolling and annealing are individually assessed. The findings indicate that new NbC precipitates form during annealing process after cold rolling, and these precipitates are smaller than those formed during hot rolling. This study offers valuable insights into the precipitation process of NbC in cold‐rolled HSLA steel and has implications for the development of improved steel processing techniques.

Design for material properties of additively manufactured metals using topology optimization

In metal Additive Manufacturing (AM), the deposited material is subjected to a series of heating and cooling cycles. The locally occurring temperature extremes and cooling rates determine solid-state phase fractions, material microstructure, texture, and ultimately the local material properties. As the shape of a part determines the local thermal history during AM, this offers an opportunity to influence these material properties through design. In this paper, we present a way to obtain desired properties by controlling the local thermal history. This is achieved through topology optimization of the printed part while considering its entire transient thermal history. As an example of this approach, this work focuses on high strength low alloy steels, where resulting phase fractions significantly influence mechanical properties such as yield strength and ductility. These solid-state phase fractions depend on cooling rates in a particular critical temperature range. The phase composition and hence the local yield strength in target regions can be controlled by constraining the cooling time in this range. Numerical examples illustrate the capability of the proposed approach in adapting part designs to achieve various desired material properties.

Analysis of the Temperature Evolution at Necking during Tensile Deformation of H240LA Steel Sheets

The study of localized necking based on strain analysis using Digital Image Correlation (DIC) is the most widely used technique in sheet metal forming to study the FLD (Forming Limit Diagram). However, due to the heat generated by plastic deformation during the forming operations, another way is to analyze the temperature field of the specimen during the test by using Digital Infrared Thermography (DIT). A series of Nakazima tensile tests of high-strength low-alloy steel were tested using DIC and DIT synchronized systems. In this study, a thermomechanical numerical model was developed in ABAQUS/Standard in order to study the energy balance between the different effects of heat generation by plastic deformation, and transient conductive and convective heat transfers through the sample and to the environment. Analysis of the predicted energy balance during the tests allowed to understand the temperature evolution observed both at the beginning and at the development of the unstable necking until fracture. The numerical results are consistent with the analysis obtained from experimental temperature field, making feasible the use of DIT systems to study new necking detection criteria.

Effects of Intercritical Heat Treatment on the Temper Embrittlement of SA508 Gr.4N Ni-Cr-Mo High Strength Low Alloy Steels for Reactor Pressure Vessels

To analyze the effects of intercritical heat treatment on the temper embrittlement of SA508 Gr.4N steels, two model alloys with different phosphorus (P) contents were fabricated. Each sample was heat treated by applying a conventional heat treatment process (quenching-tempering) with/without an intercritical heat treatment process (IHT) and a step-cooling heat treatment for temper embrittlement. Then their microstructure and mechanical properties were evaluated. The microstructure of the SA508 Gr.4N model alloy was composed of tempered lower bainite and martensite, and nano-sized precipitates formed both inside and at boundaries. The grain size was reduced when IHT was applied. There was a small difference in tensile properties according to the heat-treatment conditions and P contents, but the difference in Charpy impact properties was large. The heat treatment for temper embrittlement (TE) increased the impact transition temperature, and a very significant increase was observed in steels with a high P content. The increase in transition temperature owing to TE was reduced when IHT was applied. The fractograph analysis of Charpy fractured specimens at transition temperatures showed that an increase in intergranular fracture was main reason for the TE, and that IHT reduced the formation of intergranular fracture. The AES results showed that P-Ni was segregated at grain boundaries, and the level of segregation was reduced by applying IHT. This occurred because the formation of prior austenite grain boundaries by IHT dispersed the P at grain boundaries, and reduced the amount of P segregation.

The effect of vanadium micro-alloying on the microstructure of welded joints in high-strength structural steels

The balance between high strength and toughness in high-strength-low-alloy (HSLA) steels can be defined by the thermal cycles in the heat-affected zone (HAZ) of a welded joint, during a double-pass welding process with secondary heating in the inter-critical zone (IC CG HAZ). After multiple heating cycles in the temperature range between Ac1 and Ac3, the steel undergoes a strong loss of toughness and resistance to fatigue, mainly caused by the formation of residual austenite (RA). This study aims to investigate the influence of vanadium addition on the behavior of IC GC HAZ in S355-grade HSLA steel. The welding thermal cycles were simulated, considering five different inter-critical temperatures, between 720 and 790 °C. The addition of vanadium as a micro-alloy to an S355 structural steel was found to increase the mechanical strength of the IC GC HAZ zone of a welded joint without compromising toughness and fatigue resistance. This result is obtained through the generation of a bainitic microstructure with dispersion of fine regions of residual austenite and a fine and uniformly distributed precipitation.Graphical abstract

Descaling Abilities of Two Low-Alloy High-Strength Steels Under Different Heating Processes

Descaling Abilities of Two Low-Alloy High-Strength Steels Under Different Heating Processes

Predicting sulfide stress cracking in a sour environment: A phase-field finite element study

Sulfide stress cracking (SSC) is a leading cause of failure in sour service environments, where the presence of wet hydrogen sulfide (H2S) causes hydrogen embrittlement and significantly influences the performance and lifespan of casing and tubing pipes. This work presents a numerical investigation on predicting the onset and growth of SSC in a sour environment using a coupled deformation–diffusion phase-field finite element framework, which incorporates the role of sub-surface hydrogen concentration due to H2S exposure and mechanical loading effects on the crack growth response. The numerical results agree with the experimental data from the notched slow strain rate testing performed on high-strength low alloy steel (HSLA) in a sour environment at room temperature. Recently, the oil and gas industry has been heading towards unconventional gas well applications that expose crucial parts of a well construction, such as production casings, to high internal pressures and a sour environment. To simulate such conditions, a numerical study is conducted that examines the onset and growth of SSC in pre-notched pressurized pipes subjected to H2S exposure. The geometry and boundary conditions used for the pre-notched pipes adhere to the API 579 standard for fitness for a service assessment of equipment containing identified flaws or damage. The findings of this comprehensive numerical investigation provide valuable insights into the effectiveness of a coupled phase-field approach for SSC and demonstrate its potential as an engineering tool for structural integrity assessments that consider environmental effects.

Research on Thermal Properties and High Temperature Exposure Behavior of Non-Skid Coating Fabricated by Twin Wire Arc Spraying

Conventional non-skid coatings for marine construction contain polymeric materials. These materials are generally susceptible to high temperature environments because of their low thermal conductivity and thermal resistance. A metal-based non-skid coating has great potential for high temperature applications, yet, there has only been limited research. In this study, twin wire arc spray (TWAS) was used to fabricate Al and Al-3%Ti coatings on a high strength low alloyed (HSLA) steel substrate. The purpose of this study is to confirm the feasibility of TWAS Al-based coating for non-skid areas on marine construction. The static coefficient friction of TWAS Al-based coatings exhibited excellent and uniform values compared with a conventional epoxy-based non-skid coating. The specific heat and thermal conductivity of TWAS Al-based coating was measured and compared with that of the substrate. The thermal property values of the TWAS Al-based coating were reported for the first time in this study. The TWAS Al-based coating had A continuous interface with the substrate and the general microstructural features of a thermal-sprayed metal coating. After exposure to 500℃ for 24 hours, the an Fe-Al intermetallic compound and oxide were formed inside of the coating and coating-substrate interface. The adhesion strength indicated that the TWAS Al-based coating sustained its strength after the isothermal exposure test. The Vickers hardness of the TWAS Al-3%Ti coating was higher than that of the Al coating. The solid solution hardening of Ti atoms in the as-deposited coating and the precipitation hardening of the TiAl3 compound in the heat-treated coating contributed to the improvement of in Vickers hardness. Thus, the TWAS Al-3%Ti coating is proven to be a promising nonskid coating for high temperature applications.

Mechanism of the Interaction Between Hydrogen, Microstructure, and Mechanical Properties in Low-Alloy High-Strength Marine Steel

Mechanism of the Interaction Between Hydrogen, Microstructure, and Mechanical Properties in Low-Alloy High-Strength Marine Steel

Microstructure and corrosion behavior of 10CrNi3MoV high-strength low-alloy steel coating via underwater wire-feed laser cladding

The underwater local dry wire-feed laser cladding was successfully used to prepare 10CrNi3MoV high-strength low-alloy steel coating for the first time and the influences of water environment on the surface morphology, cross section, microstructure and corrosion behavior of cladding layer were studied. Compared with the in-air cladding layer, the surface flatness of the underwater cladding layer was poor. There were no defects such as lack of fusion and cracks between the cladding layers and substrate. Besides, the heights of cladding zone and heat affected zone in underwater cladding layer were 94.8 % and 88.5 % that of in-air cladding layer, respectively. Due to the presence of more lath martensite, smaller grain size, higher kernel average misorientation and lower texture strength of (100) lattice plane, the electrochemical corrosion performance of underwater cladding layer was poor. The corrosion mechanisms of both underwater and in-air cladding layers were pitting corrosion, but corrosion degree of underwater cladding layer was more serious and corrosion rate was faster. There were less α-FeOOH, Cr2O3 and NiFe2O4 in underwater cladding layer, which reduced the compactness of corrosion products film. Therefore, the protection ability of the corrosion products film of the underwater cladding layer became weak.

Variations in microstructure and mechanical properties along thickness direction in a heavy high strength low alloy steel plate

A thermal-mechanical control process (TMCP) followed by tempering at 600 °C was applied to produce 420 MPa grade high strength low alloy (HSLA) steel heavy plates. The microstructure and mechanical properties through the thickness were analyzed using various techniques including optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron back-scattered diffraction (EBSD), tensile and impact tests. Microscopy analyses showed that a fine-grained structure with an average grain size of 6–10 μm could be obtained by TMCP. After subsequent tempering, the microstructure near the surface of the plate was dominated by bainite, while the microstructure of the core was mainly characterized by aggregated carbides and ferrite. In addition, the density of high-angle grain boundaries (HAGB) on the surface was significantly higher than that in the core. Tensile tests showed a decrease in both yield and tensile strengths from 530.1 and 626.9 MPa on the surface to 384.3 and 496.7 MPa in the core, respectively. The contribution of different strengthening mechanisms to the variations in strengths along the thickness was clarified. In addition, the deformation of ferrite and the initiation of micro-voids during tensile tests were also analyzed.

Proposal and Assessment of a Multiple Cycle-Continuous Cooling Transformation (MC-CCT) Diagram for Wire Arc Additive Manufacturing of Thin Walls

Continuous cooling transformation (CCT) diagrams of base metals are common in welding. They can be built using physical or numerical simulations, each with advantages and limitations. However, those are not usual for weld metal, considering its variable composition due to the dilution of the weld into the base metal. Wire Arc Additive Manufacturing (WAAM) is a distinctive case in which the interest in materials comparable with weld composition raises attention to estimating their mechanical properties. Notwithstanding, this concept is still not used in WAAM. Therefore, the aim of this work was to address a methodology to raise MC-CCT (Multiple Cycle Continuous Cooling Transformation) diagrams for WAAM by combining physical and numerical simulations. A high-strength low-alloy steel (HSLA) feedstock (a combination of a wire and a shielding gas) was used as a case study. To keep CCT as representative as possible, the typical multiple thermal cycles for additive manufacturing thin walls were determined and replicated in physical simulations (Gleeble dilatometry). The start and end transformations were determined by the differential linear variation approach for each thermal cycle. Microstructure analyses and hardness were used to characterise the product after the multiple cycles. The same CCT diagram was raised by a commercial numerical simulation package to determine the shape of the transformation curves. A range of austenitic grain sizes was scanned for the curve position matching the experimental results. Combining the experimental data and numerically simulated curves made estimating the final CCT diagram possible.

Correlation between microstructure and fatigue properties of hot-rolled thick-plate complex-phase steel

Complex-phase (CP) steels, with a multiphase microstructure, offer an excellent combination of high strength, ductility, and formability, making them an attractive alternative to conventional high-strength low-alloy (HSLA) steels in the automotive industry. However, the microstructure and fatigue property relation in CP steels is complex. This limits the full exploitation of CP steels in applications, such as heavy-vehicles, where excellent fatigue performance of thick-plates after punching holes is the critical parameter. In this work, we initiate the study of the relation between microstructure and fatigue properties of a commercial CP steel (800CP) and compare it with a conventional HSLA (500MC) steel. Fatigue property, tensile property, and fatigue crack growth rate (FCGR) testing are conducted and the performance of the two steels is rationalized using detailed microstructure characterization, before and after fatigue testing. FCGR testing shows that, despite a higher yield strength of the 800CP, both steels have a similar propagation rate due to a more tortuous crack propagation path and a higher quantity of secondary crack formation in the 800CP microstructure. The high cycle fatigue (HCF) testing shows that the fatigue limit in the 800CP is 25% higher. This increase in fatigue limit is attributed to the improved resistance to fatigue crack initiation in the 800CP due to its larger fraction of bainite.

Automated classification of granular bainite and polygonal ferrite by electron backscatter diffraction verified through local structural and mechanical analyses

Differentiation of granular bainite and polygonal ferrite in high-strength low-alloy (HSLA) steels possesses a significant challenge, where both nanoindentation and chemical analyses do not achieve an adequate phase classification due to the similar mechanical and chemical properties of both constituents. Here, the kernel average misorientation from electron backscatter diffraction (EBSD) was implemented into a Matlab code to differentiate and quantify the microstructural constituents. Correlative electron channeling contrast imaging (ECCI) validated the automated phase classification results and was further employed to investigate the effect of the grain tolerance angle on classification. Moreover, ECCI investigations highlighted that the grain structure of HSLA steels can be subdivided into four grain categories. Each category contained a different nanohardness or substructure size that precluded a nanoindentation-based phase classification. Consequently, the automated EBSD classification approach based on local misorientation achieved a reliable result using a grain tolerance angle of 5°.Graphical abstract

Multi-performance evaluation of high-throughput accelerated corrosion test for high-strength low-alloy 921A steel

Multi-performance evaluation of high-throughput accelerated corrosion test for high-strength low-alloy 921A steel