Q235 Steel Research Articles

Fabrication, Microstructure and Corrosion Resistance of Zn/Al Composite Coating by Arc Spraying

In this work, the Zn/Al composite coating was prepared on the surface of Q345 steel using arc spraying. The simple and efficient cold-pressing technique was used for the composite coating. The cold pressure sealing (CPS) technique is proposed to reduce the porosity of the composite coating. The corrosion behavior of Zn/Al composite coatings without and with cold pressure sealing treatment in a corrosive environment was studied. The microstructures of composite coatings without and with CPS were studied by scanning electron microscope (SEM), and the corrosion properties of composite coating without and with CPS were comparatively investigated. The results showed that the porosity of the composite coating was significantly reduced to 2% by CPS. After 28 days of immersion, the dense corrosion products filled the defect area in the CPS sample. After CPS treatment, the corrosion potential is −0.829 V, and the corrosion current density is 5.636 × 10−6 A/cm2. After cold pressing, the bonding strength of the coating is 13.82 MPa, which is 43% higher than that before the sealing treatment. The Zn/Al composite coating treated by CPS exhibits excellent corrosion resistance in the simulated marine environment.

Ultrafast synthesis of novel coal-based graphene and its anticorrosion properties of epoxy/graphene nanocomposite coatings

Graphene has a wide range of applications in anti-corrosion coatings due to its excellent barrier, shielding, and mechanical properties. However, traditional graphene synthesis methods, including the production of graphene oxide (GO) using Homer's method and then its reduction in the form of reduced graphene oxide (rGO) are time-consuming, energy-consuming, and environmentally polluting, which limits their application in anti-corrosion coatings. This study leveraged the capabilities of flash Joule heating (FJH) to synthesize flash coal-based graphene (FCBG) from Taixi anthracite (TA) within 200 ms without pretreatments or chemical reagents. The FJH had the advantages of low energy consumption and being environmentally friendly. Compared with the rGO, the FCBG prepared by FJH was characterized by fewer defects, larger carbon sheets, and a turbostratic structure. Moreover, carbon steel Q235 was used as the substrate to prepare anti-corrosion coatings by mixing FCBG at different flash voltages with epoxy resin (EP). Based on this, the electrochemical performance of different coatings was compared before and after salt spray corrosion. The results demonstrated that the FCBG composite anti-corrosion coating (EP/FCBG190) prepared using EP and FCBG synthesized at 190 V in the FJH, displayed stronger corrosion resistance than the EP and rGO composite coating (EP/rGO). The FJH synthesis process provides a feasible route for improving the synthesis process of the anti-corrosion coatings and the high value-added utilization of coal.

Microstructure and corrosion behavior of Co-free FeCrNiSi0.4 medium entropy alloy coating fabricated by laser cladding

To improve the performances of engineering components is a hot topic for materials science and engineering communities. In the present work, the Co-free FeCrNiSi0.4 medium entropy alloy (MEA) coating was manufactured onto a Q235 steel substrate using laser cladding. Then, the microstructure, hardness and corrosion resistance of the MEA coating were carefully examined. The results indicate that the MEA coating, without obvious cracks and pores, exhibits a duplex phase microstructure consisting of majority face-centered cubic (FCC) phase and minor hexagonal close-packed (HCP) phase. In 3.5 wt% NaCl solution, the MEA coating displays superior corrosion resistance with a pitting potential of 1.19 V (vs. SCE), which is much higher than that of 304 stainless steel. The remarkable anti-corrosion performance can be attributed to the multiple kinds of oxidation (NiO, Fe2O3, Cr2O3 and SiOx (x < 2)) formed on the passive film and the small difference of Volta potential (∼40 mV) between FCC phase and HCP phase. Moreover, the microhardness of the coating reaches 346 HV, which is 2.1 times higher than that of the Q235 steel. These findings offer an effective route to fabricate a MEA coating with superior corrosion resistance and mechanical property, which thus can improve the service stability of industrial components.

Ultra low cycle fatigue behavior of Q690 high-strength steel welded T-stub joints: Experiments and fracture prediction analysis

The paper presented an experimental and numerical investigation of the ultra low cycle fatigue behavior of high-strength steel welded T-stub joints. The normal and funnel T-stub joints in Q690 high-strength steel were tested under monotonic tensile loading and ultra low cyclic loading. The cyclic response of normal T-stub joints varying from bolt diameter, flange size and weld form were studied. It is found that fracture mode of the T-stub joints is basically the same under tensile loading and cyclic loading, i.e., cracking behavior occurs at the weld toe of the flange and tensile-shear failure is observed. The different configuration parameters of normal T-stub joints in the study show no significant influence on the fatigue life of the joints. Comparing the ultra low cycle fatigue results between normal and funnel T-stub joints indicates that the funnel T-stub joints have better energy dissipation capacity. In addition, the ultra low cycle fatigue performance of Q690 steel and ER80-G weld metal under various stress states were analyzed and discussed. In order to numerically generate the overall fracture behavior of the T-stub joins, the Lode parameter enhanced cyclic void growth model was adopted in the numerical simulation and the model parameters were calibrated according to the test results of Q690 steel and weld metal. Comparison with the experimental monotonic and cyclic tests of welded T-stub joints shows that the Lode parameter enhanced cyclic void growth model can provide accurate predictions of the ultra low cycle fatigue of the joints.

Improved true stress-strain model of high-strength steels for fracture simulation in fire

Fracture prediction of high-strength steel at elevated temperatures is particularly essential for the performance-based design of high-strength steel structures in fire. Accurate prediction of fracture behavior of high-strength steels in fire requires a precise true stress-strain model up to a large strain level (>1.0 mm/mm). This research investigates improved true stress-strain models of Q550, Q690, Q890, Q960, S690, and S960 high-strength steels at elevated temperatures up to 800 °C. The true stress-strain models are calibrated from test data and finite element analysis results. The calibrated true stress-strain model is improved in the following two aspects. First, to ensure the rationality of the true stress-strain models, they were examined by Considère’ Construction together with the physical law of ductile metals. Furthermore, by modifying the weight function, the true stress-strain models can accurately simulate the post-necking behavior of high-strength steels at high temperatures. Based on the research results, the true stress-strain behavior of three regions, including the elastic region, strain-hardening region, and post-necking region, need different forms of functions to express. They were linear function, combined exponential and linear functions, and weighted upper-bound and lower-bound functions, respectively. It was observed that the variation of the weighting factor in the weighting function may be related to the post-necking softening behavior of high-strength steels. For the investigated high-strength steels, at lower temperatures (< 550 °C), the weighting factor decreased with the increase of true strain, resulting in a significant softening of high-strength steels after the onset of necking.

Strength Analysis of Corroded Seawater Pipeline Based on Finite Element Method

The residual strength of corroded defective pipelines is an important manifestation of pipeline-bearing capacity. The change of residual strength of Q235 steel and B10 Cu-Ni alloy pipeline caused by the change of defect depth, length, and width in the case of grooved corrosion defect was analyzed and studied by the finite element method. The results show that the effect of corrosion defect depth on the residual strength is greater than the defect length and width. At the same time, Q235 steel has better pressure-bearing performance than B10 Cu-Ni alloy.

PICKLING – PASSIVATION MECHANISM AND PROCESS OPTIMIZATION OF Q235 STEEL PIPELINE

Pipe cleaning is currently the most effective method to improve the cleanliness and corrosion resistance of pipes. In this paper, a new method of pipe cleaning is proposed, combining mechanical and chemical cleaning, offline tank cleaning and online cycle cleaning. Through experiments and characterization of the morphology changes, the mechanism of pickling and passivation of Q235 steel was explored, and the entire process of microstructure and morphology changes on the pipe wall’s surface was analyzed to verify the feasibility of this technology. The cleaning process was optimised using response surface analysis to determine the optimum cleaning conditions. This study is of great relevance to the effective operation of continuous-casting equipment over a long period of time.

Mechanical properties of Q345 structural steel after pre-fatigue loading

This study investigates the residual mechanical properties of Q345 structural steel previously damaged by pre-fatigue loading. Fatigue damage is induced by subjecting Q345 structural specimens to various loading cycles without causing fracture under three pre-fatigue loading stress levels, which is referred to herein as pre-fatigue damage. Subsequently, tensile tests are performed on these specimens to obtain the stress–strain curves and associated parameters, including yield strength, ultimate strength, elastic modulus, and ductility. Based on the test results, the effect of pre-fatigue loading on the mechanical properties of Q345 structural steel is comprehensively discussed and analyzed. Significant differences are observed in the fracture positions and morphological features of the Q345 steel structure after pre-fatigue loading. Additionally, pre-fatigue loading significantly affects the residual strength and ductility of Q345 structural steel. In particular, the residual ductility of Q345 structural steel reduced significantly after being subjected to different cyclic loadings. However, the effect of pre-fatigue loading on the elastic modulus of Q345 structural steel is almost negligible.

Acoustic Emission Response and Damage Process for Q235 Steel in an in Situ Tensile Test

Q235 steel is widely used in engineering and construction. Therefore, it is important to identify the damage mechanism and the acoustic emission (AE) response of the material to ensure the safety of structures. In this study, an AE monitor system and an in situ tensile test with an optical microscope were used to investigate the AE response and insight into the damage process of Q235 steel. The surface of the specimen was polished and etched before the test in order to improve the quality of micrographs. Two kinds of AE responses, namely a burst and a continuous signal, were recorded by the AE monitor system during the test. Based on the in situ test, it was observed that the damage of Q235 steel was induced by the crystal slip and the inclusion fracture. Since the crystal slip was an ongoing process, continuous AE signals were produced, while burst AE signals were possibly produced by the inclusion fracture which occurred suddenly with released higher energy. In addition, a great number of AE signals with high amplitude were observed during the yielding stage and then the number and amplitude decreased.

Comprehensive studies on the behaviors of high strength steel T-stubs with thin-walled flange at elevated temperatures

This paper presents the experimental, numerical, and theoretical studies aimed at investigating the fire behaviors of high strength Q690 steel T-stub connections. The experiments determined failure modes, load–displacement curves, ultimate displacement, ductility factors, and load capacities of the specimens at elevated temperatures. The rupture of the flange disappeared at temperatures exceeding 600 °C. A finite element model was established using ABAQUS software, validated by the experimental results, to explore the effect of bolt preload and bolt grade on the fire behaviors of T-stubs. The first yield resistance derived from experimental and numerical findings was compared with EC3 predictions, highlighting a severe underestimation by EC3 for high-strength steel T-stubs with thin-walled flanges. A theoretical model was subsequently proposed and validated against numerical and experimental outcomes, serving as the basis for a novel design method. This model accurately anticipates the progression of the plastic hinge line and the first yield resistance, suggesting the use of 2.0% yield strength of high-strength steel to calculate the first yield resistance of steel T-stubs.

Advanced Algorithms to Predict Time-Dependent Atmospheric Corrosion Wastage of Low-Alloy and High-Strength Steels Based on Chemical Compositions

The mathematical relationship between corrosion degree and time is referred to as a corrosion model. Existing corrosion models can only be used to predict the corrosion wastage of a certain material based on its available historical corrosion data, but the corrosion wastage of newer steel grades cannot be obtained if the data are not available. To solve this problem, two advanced algorithms, i.e., generalized regression neural network (GRNN) and optimizing grey model (OGM (1, N)), are introduced, based on which corrosion models can be obtained for steel classes even in the absence of historical corrosion data, as long as the chemical compositions of the material are known. First, the theoretical basis and operational procedures of GRNN and OGM (1, N) are introduced. Grey relational analysis of corrosion wastage influencing factors is subsequently conducted. Last, the time-dependent atmospheric corrosion wastages of Q345 and Q460 steels, two typical structural steel grades but their corrosion models have not been well established, are predicted based on their chemical compositions by these two advanced algorithms. The results show that the main chemical compositions that influence the atmospheric corrosion wastage of steels are C and S. Both GRNN and OGM (1, N) can accurately predict the corrosion wastage of the steels, and the predicted results can be fitted by quadratic function or power function, where the goodness of fit is greater than 0.95, which indicates a high fitting accuracy.

Effect of zinc oxide on corrosion resistance of magnesium ammonium phosphate cement-based coating

In order to improve the anticorrosive performance of magnesium ammonium phosphate cement (MAPC) coating, a small amount of zinc oxide was added to the MAPC coating to modify and coat the surface of Q235 steel. The anti-corrosion resistance and mechanism of MAPC coating modified by zinc oxide were analyzed based on electrochemical test results, and the morphology and composition changes of the coating before and after immersion were observed and tested using X-ray diffraction (XRD), scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), and a thermogravimetric analyzer (TG-DTG). Low field nuclear magnetic resonance testing was used to determine the porosity of the coating and the corrosion resistance of the modified coating was tested by a neutral salt spray test. The results show that after immersion in a 3.5% NaCl solution for 28 days, the MAPC coating with 3% (mass fraction) zinc oxide exhibited a corrosion current density of 2.96 × 10-4 μA/cm2 at a corrosion potential of −0.870 V, demonstrating a favorable outcome with a positive shift.; Meanwhile, the 28 days polarization resistance of the modified coating was 97436 Ω∙cm2, which was 78% higher than that of the blank. The shielding performance of the coating was enhanced, and the charge transfer resistance was also significantly improved. The porosity of the modified coating before and after immersion was lower than that of the blank group. After 1440 h of neutral salt spray testing, there was no swelling or peeling on the coating surface, and there was no trace of corrosion on the internal substrate.

Response modification factor of high strength steel frame with D-eccentric brace using improved pushover analysis method

The high-strength steel frame with D-eccentric brace presents a novel structural system that demonstrates exceptional plastic deformation capabilities when exposed to high levels of earthquake hazards. This system employs ordinary steel links with a yield strength below 345 MPa, while the frame beam and column utilize high-strength steel (yield strength above 460 MPa, such as Q460 or Q690 steel) to reduce cross-sectional dimensions while ensuring elasticity of non-energy consuming components. The resulting structure exhibits outstanding ductility and energy-dissipating capacity. The response modification factor (R), a crucial parameter in performance-based seismic design, plays a significant role in achieving appropriate and cost-effective seismic designs. Unfortunately, the 2016 edition of China's code for Seismic Design of Buildings (GB50011-2010) did not consider the concept of R and instead employed a constant value for all structural systems, which is unreasonable. Therefore, a comprehensive investigation of the R value for the high-strength steel frame with D-eccentric brace is imperative to enhance structural performance design, provide guidance for future designs, and promote the widespread implementation of this structure in seismic regions, where it exhibits superior seismic performance. This study utilizes the performance-based seismic design approach to design structures with varying numbers of stories (4, 8, and 12), link lengths (900, 1000, and 1100 mm), and different steel strengths (Q460 and Q690). An improved pushover analysis method is employed to calculate the R values for each prototype, considering the number of structural stories (N) and the link length (e). The derived values of each performance coefficient serve as valuable references for future performance designs of novel structural systems.

Experimental and theoretical investigations of three Mannich-base imidazoline quaternary ammonium salts as efficient inhibitors for Q235 steel in sulfuric acid

Three Mannich base imidazoline quaternary ammonium salt corrosion inhibitors were designed and successfully synthesized, and their inhibition properties and mechanisms for Q235 steel in H2SO4 solution were investigated by experiments and theoretical calculations. It is found that three inhibitors act as mixed inhibitors to effectively inhibit the corrosion of Q235 steel in H2SO4 solution by chemisorption, and the maximum corrosion inhibition efficiency reaches 96.9 %, 97.3 % and 98.2 %, respectively. Theoretical calculations reveal that three inhibitors exhibit multi-center adsorption features and spontaneously adsorb on the surface of Q235 steel through horizontal orientation.

Corrosion behaviors and mechanical properties of Q235 steel pipes collapsing due to corrosion after 25-year service in urban industrial atmospheric environment

Since the period required for testing the atmospheric corrosion of steel is long, most studies have focused on the corrosion behavior in less than three years, making exploring long-term atmospheric corrosion particularly valuable. This study investigates the corrosion behaviors, corrosion models, and mechanical properties of Q235 welded steel pipes collapsing due to corrosion after 25-year service in an urban industrial atmospheric environment using SEM, XRD, electrochemical methods, 3-D noncontact surface profilometry, and static tensile testing. The typical morphologies of α-FeOOH, γ-FeOOH, and Fe3O4 and the effect of the content of various corrosive materials on the corrosion rate of the steel pipes are identified and analyzed. Then, the influence of different corrosion degrees on the mechanical properties of the steel pipes is examined by considering the morphologies of the rust pits. The results show that the wetting–drying cycles affect the structures of the rust layers and their protective properties. The rust layers on the sheltered surface are thicker but less protective than those on the exposed surface. In the wet state, FeSO4 accelerates ion transfer, while Fe3O4 facilitates electron transfer. These processes collectively contribute to the corrosion of Q235 steel. Moreover, as the time-of-wetness of the rust layers on sheltered specimens increases, the corrosion rate of Q235 steel also accelerates. The corrosion model combines pitting and uniform corrosion and gradually changes from predominated by pitting to thickness as the corrosion degree increases. The corrosion morphology impacts the mechanical properties of the welded steel pipes, and the influences of the thickness loss and maximum rust pit depth on these properties are profound.

Corrosion inhibition performance of Punica granatum L extract on Q235 steel in H2SO4 environment: Electrochemical, morphological, and quantum chemical studies

The corrosion inhibitor used in this experiment was the extract of Punica granatum L (PGLE), which was obtained using the pure water extraction method. The inhibition performance of PGLE on Q235 steel in H2SO4 environmental was investigated using electrochemical methods, morphology studies and quantum chemical calculation. The corrosion inhibition properties of PGLE were found to be excellent, with a corrosion inhibition efficiency of approximately 95% at 200 mg/L, and it exhibits characteristics of a mixed-type corrosion inhibitor. The electrochemical impedance (EIS) test revealed a remarkable increase in the charge transfer resistance with the increment of PGLE concentration, and the surface of Q235 steel was covered by a tight and well-organized protective layer of PGLE. The surface morphology test indicates a noticeable decrease in the average surface roughness upon the adsorption of PGLE extract onto the Q235 steel. According to the adsorption isotherm analysis, the adsorption behavior of PGLE on Q235 steel conformed to the Langmuir adsorption. Additionally, adsorption might be physical or chemical. Quantum chemical calculations also showed that PGLE has excellent corrosion inhibition properties.

Quantitative detection of crack depth in V-groove weld using laser-generated surface acoustic waves

Thick-walled structures are widely used in kinds of high-end equipment. As the most conventional method adopted to manufacture large-scale structures, multi-pass butt-welds are one of the most critical areas prone to defects. In this paper, we focus on the quantitative detection of crack depth in a V-groove weld using laser-generated surface acoustic waves. A two-dimensional finite-element method with Q345 steel is adopted to reveal the complicated propagation characteristics of laser-generated surface acoustic waves with surface cracks. The displacement fields are discussed to show the wave transmission, reflection, and mode-conversion phenomena. The main propagating wave modes—P, R, R′, R′r, and R′t waved—are distinguished with the help of the out-of-plane displacement under different crack depths in the time domain. It is found that R′r can be used to locate the cracks and R′t can be used to quantify the depth of the cracks.

Lightweight Design and Optimization of the Road Wrecker’s Loading Platform

Aiming to realize the lightweight design of the road wrecker’s loading platform, an efficacious method combining material substitution and size optimization is proposed in this paper. The finite element model is established at first. According to the wrecker’s working process, two typical working conditions are determined. Following the proposed stiffness and strength judgment bases, the FEA of the loading platform is carried out under typical working conditions. Finally, on the premise of meeting the basic performance of the materials, the part thickness is reduced by replacing Q235 steel with Q460 high-strength steel. The optimal size is obtained after size optimization based on OptiStruct software. The improved results show that the total mass of the new loading platform decreased by 30.8% compared with the previous structure. The promoted structural performance meets the requirements, which verifies the practicability of the lightweight design method.

Expired flunarizine hydrochloride as corrosion inhibitors for Q235 steel in hydrochloric acid medium: Experimental and computational investigation

The corrosion of carbon steel is always a very serious issue, and the addition of corrosion inhibitors is an effective approach to prohibiting the corrosion of carbon steel. Because expired drugs are environmentally friendly, green, and non‐toxic; thus, this work provides a new idea for the treatment of expired drugs. The expired flunarizine hydrochloride (FH) is used as corrosion inhibitors for Q235 steel, investigating the corrosion inhibition efficiency of expired FH with different concentrations for carbon steel and illustrating the corrosion inhibition mechanism. Electrochemical impedance and Tafel curves are used to investigate the corrosion inhibition of carbon steel under 1 M HCl solution with different concentrations of the expired FH, and the corrosion efficiency is calculated according to the immersion tests, and the corrosion inhibition efficiency is more than 88.5%. Scanning electron microscopy (SEM), Fourier transform infrared spectrometer (FTIR), and Raman spectroscopy strongly support the results of the electrochemical experiment. Besides, the simulation results also provide the strong supports for the experimental results.

Effect of Temperature on the Morphology and Corrosion Resistance of Modified Boron Nitride Nanosheets Incorporated into Steel Phosphate Coating

In this study, the impact of various temperatures (25 °C, 45 °C, and 55 °C) on q235 steel specimens was studied to analyze the influence on the morphology and corrosion resistance of modified boron nitride nanosheets incorporated into the phosphate coating. The morphology and surface modification of the coating were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). SEM results showed that the S-45 steel sample produced a higher number of nucleation sites and reduced grain size with a denser, more robust, and more corrosion-resistant phosphate coating compared to the S-25 and S-55 samples, respectively. The potentiodynamic polarization results demonstrate that the S-45 steel sample exhibited the best corrosion resistance performance with an electric current density of 5.48 × 10−8 A/cm2, an order of magnitude lower than the S-25 and S-55 samples, respectively. The coating weight results showed that the S-45 steel specimen achieved the densest and most uniform coating (32.14 g/m2).