Mechanical Properties Of Steel Research Articles

Акустические свойства мартенситно-стареющей стали XM-12 после энергетических воздействий

The study of the acoustic properties of maraging steels operated under various energy force and temperature actions is a critical task, since it is the method of acoustic structuroscopy that provides the most reliable connection with the structure, stress-strain state and mechanical properties of steels. The paper is devoted to research of the acoustic properties of the 15-5 PH maraging steel samples under various types of heat treatment under the conditions of mechanical tensile and cyclic loads. Samples of the 15-5 PH maraging steel were studied in three structural states: solid solution annealing and subsequent aging at 470 and 565 °C; during tensile tests; during cyclic tension-compression loading. The research used a unique scientific installation “Information-measuring complex for investigation of acoustic properties of materials and products”. It implements the acoustic mirror-shadow multiple reflections method using electromagnetic-acoustic and piezoelectric transducers based on polyvinylidene fluoride film to excite and receive waves and allows determining the velocity of wave propagation with an error of no more than 2 m/s. The acoustic (wave velocity, elastic moduli, electromagnetic-acoustical (EMA) transformation coefficients, acoustic anisotropy coefficients, acoustoelastic coupling coefficients) and electromagnetic (coercive force and electrical conductivity) characteristics of the samples were examined. The samples were studied in the initial state (before loading); stepwise in the process of tensile loads and subsequent unloading; after tensile tests; during cyclic tension-compression loading. It was revealed that the following acoustic parameters of 15-5 PH steel samples are the greatest structural sensitivity to mechanical tensile load and cyclic loading: transverse wave velocity, Poisson’s ratio, double EMA-transformation coefficient, and acoustic anisotropy coefficient.

Developing the optimal chemical composition of heat-resistant Cr-Ni steel for aerospace equipment

The object of research in this work is the processes of forming the microstructure and mechanical properties of heat-resistant steels depending on their chemical composition. The microstructure and high-temperature mechanical properties of austenitic heat-resistant chrome-nickel steels of the proposed chemical composition were investigated in the work. The microstructure study determined the grain size and topography of inclusions in steels. Based on the results of mechanical tests, a multifactorial experiment was planned, which made it possible to establish the relationship between the mechanical properties of steels with alloying elements selected as factors. The obtained regression equations were used to estimate the quantitative influence of each alloying element on the corresponding mechanical properties. Analysis of the results of the experiment made it possible to determine the optimal chemical composition of steel for gas turbine engines used in the aerospace industry, as well as in the metallurgy of titanium production. It is shown that the state of solid solution and heat-resistant niobium and molybdenum carbides (chromium carbides dissolve at a temperature of 950 °C) are an important factor that significantly affects the structure, mechanical, and service properties of heat-resistant steel. The austenite structure is provided by the required amount of nickel. The resulting indicators of heat resistance of steels of different compositions, tested at temperatures of 850 °C, 950 °C, and 1050 °C, proved the superiority of steel with a higher content of carbon and chromium and a lower content of nickel. The mechanism of steel strengthening and the influence of alloying with carbon, chromium, and nickel on it have been determined. The optimal chemical composition of heat-resistant steel on an iron-nickel basis for operation at a temperature of 950 °C has been established

Dynamic mechanical properties and constitutive model establishment of QSTE420 steel

The uniaxial tensile tests of QSTE420 steel under different strain rates were carried out using an electronic universal material testing machine, a high-speed tensile testing machine and a split Hopkinson tension bar (SHTB) device, the engineering stress-strain curves of steel within the range of 0.001– 1000 s−1 were obtained and the mechanical properties of steel at different strain rates were analyzed. The results show that in the static strain rate range of 10−3– 10−2 s−1, the yield strength and tensile strength of QSTE420 steel exhibit minimal variation, fluctuating between 430– 434 MPa and 507– 515 MPa, respectively; while the uniform elongation and elongation at break remain approximately at 12% and 35%, respectively. In the high strain rate range of 10−1– 103 s−1, both yield strength and tensile strength exhibit a consistent increase in direct correlation with the tensile rate. Specifically, the yield strength increases from 444 to 607 MPa and the tensile strength increases from 523 to 640 MPa as the strain rate escalates from 10−1 to 103 s−1. Moreover, the elongation at break demonstrates a general increasing trend and reaches its peak value of 45.65% at 100 s−1. The morphology of fracture surfaces under different strain rates are observed by Scanning Electron Microscopy (SEM). The fracture appearance analysis reveals numerous dimples in the fracture, indicating a ductile fracture. Furthermore, the comparison demonstrates that steel exhibits enhanced plasticity at a strain rate of 100 s−1. Based on the experimental results, the Johnson-Cook constitutive model was established and modified. The modified Johnson-Cook model exhibits a higher determination coefficient (R2) compared to the original version, signifying an improved fitting accuracy.

The Influence of Heatmap Correlation-based Feature Selection on Predictive Modeling of Low Alloy Steel Mechanical Properties Using Artificial Neural Network (ANN) Algorithm

The Influence of Heatmap Correlation-based Feature Selection on Predictive Modeling of Low Alloy Steel Mechanical Properties Using Artificial Neural Network (ANN) Algorithm

Effect of retained austenite on mechanical properties of steel with 15 % Cr

The paper considers the study of influence of retained austenite on the mechanical properties of steel of the austenite-martensitic class based on 15 % Cr after various heat treatment. Significant amount of retained austenite remains in the steel microstructure after quenching and subsequent tempering or heating in the intercritical temperature range that makes difficult to achieve a high yield strength. Destabilization of retained austenite with subsequent transformation into newly formed martensite is provided by multi-stage heat treatment which includes quenching, heating in the intercritical temperature range or above the AC3 point and final tempering. It was established that retained austenite remains in the microstructure of two-phase steel and has the form of blocks and thin layers located in the inter-lath space. Tensile testing of steel based on 15 % Cr showed that multi-stage heat treatment provides a high-strength condition corresponding to strength groups Q125 and Q135. A comparative analysis of deformation behavior of semi-austenitic steel in various states indicates that the beginning of the martensitic transformation after the final tempering shifts into the elastic region during tension and leads to the formation of stress-assisted martensite. It was determined that block-shaped retained austenite in steel with 15 % Cr predominantly undergoes martensitic transformation during tensile and impact tests at a subzero temperature. This is supposed to be the reason for the noticeably lower impact toughness of semi-austenitic steel with 15 % Cr compared to martensitic steel with 13 % Cr at equal strength.

VERIFICATION OF GEOMETRIC MODELS OF THE LPC ROTOR OF THE K-1000-60/3000 TURBINE UNIT BASED ON NATURAL AND CRITICAL FREQUENCIES IN THE ANSYS SOFTWARE COMPLEX

One of the priority tasks of the energy industry is to ensure the reliable and safe operation of steam turbine units of thermal power plants and nuclear power plants. Given the difficult situation in the country, it is impossible to replace outdated equipment that has exhausted its design resource with new ones. As is known, the safety factor of the material taken into account during the design of steam turbine equipment was very approximate. At that time, there were no data on the operation of power equipment, which would have already worked for 200-220 thousand hours. in difficult operating conditions. The situation has changed now. There are power installations that have exhausted or are close to exhausting their design resource. By conducting experimental studies with metal samples of this equipment, it is possible to significantly clarify the physical and mechanical properties of steels and their damage due to operation. Therefore, the problem of extending the resource is becoming increasingly important. Computer modeling has greatly simplified the task of calculating the resource of the equipment. However, such a complex object as a steam turbine requires significant computing resources, and the calculation of equations in all finite element nodes is quite time-consuming. It is necessary to look for ways to rationalize calculation mathematical models. At the same time, the accuracy of the calculation should remain at a satisfactory level. In this work, were created simplified geometric models of the rotor of the LPC turbine unit К-1000-60/3000. The option is considered of replacing the working blades with equivalent distributed masses and toroidal rings. Verification of the obtained models based on critical rotation frequencies confirmed the possibility of replacing the working blades with distributed masses. On the other hand, the presence of toroidal rings of large radii leads to a significant reduction of critical frequencies in comparison with normalized values.

Seismic performance and hysteretic model of corroded steel frame columns in offshore atmospheric environment

Previous studies show that the offshore atmospheric environment corrosion gradually reduces the physical and mechanical properties of steel and eventually deteriorate the seismic performance of steel structures. This paper presents a comprehensive study on the seismic performance of corroded steel frame columns in offshore atmospheric environment. Artificial climate accelerated corrosion tests and cyclic loading tests were carried out on six steel frame columns. The effects of corrosion level and axial compression ratio on the failure mechanism and seismic performance of the columns were investigated in details. The test results indicate that with an increase in corrosion level or axial compression ratio, the displacements associated with plate local buckling, plastic hinge formation and final failure tend to reduce gradually. The bending capacity, ductility and energy dissipation capacity of columns also significantly decrease, and the strength and stiffness degradation effect intensify. Furthermore, a moment-rotation hysteretic model in plastic hinge zone for corroded steel frame columns, considering the cyclic deterioration in strength and stiffness, was established by introducing a two-parameter seismic damage model. The predicted moment-rotation curves and energy dissipations coincided well with the experimental results, verifying the rationality and applicability of the proposed hysteretic model. The research results provide theoretical support for elastic-plastic time history analysis and seismic risk assessment of existing steel frame structures in offshore atmospheric environment.

Experimental investigation of steel beam-to-column end-plate joints under static and impact loading

Events like blasts, vehicle impacts, gas explosions, or terrorist attacks can induce dynamic structural responses. Traditional design practices focus on structures' static or quasi-static behavior, neglecting dynamic effects. However, the response of structural members and joints under dynamic loading can differ significantly from that under static loading. For instance, the mechanical properties of steel, such as yield strength and tensile strength, exhibit variations depending on the strain rate. Experimental impact load tests of members and connections are needed to validate FEM models, but a very limited number of such tests have been presented in the literature. This article presents experimental static and impact tests of double-sided extended steel bolted end-plate joints. The tests were carried out on three identical steel specimens of a beam-to-column system, with static tests on one specimen and impact tests on two other specimens. A free-falling concrete-steel package was used as the impact load, with varying values of its weight and the height of the fall. The structural responses of the joints and selected components were measured using advanced measuring equipment for experimental static and dynamic tests. In both static and impact tests, significant deformation of the connection elements, especially the column and end-plate, was observed. Moreover, local buckling appeared in the compression zone of the column web as well as fracture of the end plate below the lower flange of the beam. Based on the results of the deformation measurements, the actual strain rate and dynamic increase factor (DIF) were obtained.

Relation between Microscopic Internal Stress Caused by Phase Transformations and Mechanical Properties in Steels

Relation between Microscopic Internal Stress Caused by Phase Transformations and Mechanical Properties in Steels

Neural network modelling of the Nb effect on mechanical properties of the ferritic bainitic dual-phase steel

ABSTRACT The production of low-alloy advanced high-strength steels such as the dual-phase (DP) steel with ferritic-bainitic microstructure using a hot strip mill is challenging in terms of consistent mechanical properties-based DP steel without violating the hot strip mill rolling capacity. In the present study, the Artificial Neural Network (ANN) technique was employed to develop tensile strength, yield strength and %Elongation models which can cater to complex relationships between the DP steel mechanical properties as a function of steel composition and rolling parameters. Furthermore, ANN models were used to predict the Nb effect on the mechanical properties of the DP steel. Model prediction and validation confirmed that niobium has a notable influence on mechanical properties. Finally. Nb’s role during hot rolling was reviewed and justified.

Effect of combined cold deformation and subsequent heat treatment on the microstructure, texture, mechanical properties and cementite spheroidization in AISI 1070 steel

In this study, the effects of thermomechanical heat treatments on two batches of commercial AISI 1070 steel were investigated. Both samples underwent cold rolling and annealing at 600 °C for 30 min, and their microstructure and crystallographic texture were analyzed using XRD, SEM observations, and EBSD measurements. Tensile testing was also conducted to evaluate the mechanical properties of the steels. The results showed that the lamella pearlitic microstructure of both samples was transformed into α-ferrite matrix with spheroidal cementite particles (Fe3C). Sample A exhibited a strong γ-fiber texture parallel to the rolling plane, with a typical cold-rolled texture and high anisotropic characterization dominated by (111)<uvw> orientation. Sample B, on the other hand, exhibited (111)[12¯1] and GOSS (110)<001> texture components with dominant (111) and (101) grain orientations along the rolling direction. While the yield stress and tensile strength were higher in sample A, sample B had better toughness and elongation properties, indicating that it was more ductile. These findings highlight the importance of controlling heat treatment processes to achieve desired microstructures and mechanical properties in steels and provide insights into the relationship between microstructure, crystallographic texture, and mechanical properties. The results of this research could be useful in optimizing the process and performance of steels in various industrial applications.

The Influence of Steel Variability on the Reliability of Welded Beam‐to‐Column Joints

AbstractBeam‐to‐column joints have a significant impact on the reliability of load‐bearing steel frame structures. Proper characterisation of the joint behaviour affects the distribution of internal forces and bending moments in frame structural members and affects their reliability level. This article addresses the effect of the variability of steel mechanical properties on the overall behaviour and reliability of welded beam‐to‐column joints. Monte Carlo simulations and parametric numerical analyses were performed to investigate the influence of the variability of mechanical properties on the behaviour (failure modes and resistances) of the joint and to generate data for the reliability analysis. Reliability analyses were performed to calculate partial resistance factors (γM1) for welded steel joints using the procedure given in Annex D of EN 1990. The analyses included the FprEN 1993‐1‐1:2022 and JCSS probabilistic models for mechanical properties of steel and two approaches for determining joint plastic bending resistance. It was concluded that FprEN model gives more favourable values of γM1. It was also found that the approach for determining joint plastic bending resistance can have a large effect on the partial resistance factor γM1 and ultimately on the reliability of the joint.

Flexural behavior and reliability analysis of rectangular concrete-filled cold-formed steel tabular beams

Concrete-filled steel tube (CFST) has been widely investigated for columns, whereas it has been less explored for beams. This study investigates the behavior and reliability of CFST beams under bending, both experimentally and theoretically. Experiments were performed on nine rectangular CFST beams and three steel tube (ST) beams under bending. The experimental results showed that local buckling was the failure of both ST and CFST beams. The load−deflection behavior of CFST beams was significantly better than that of ST beams. Load-carrying capacity and stiffness of CFST beams was found to be approximately 3.0 and 1.29 times those of ST beams, respectively. The mechanical properties of steel were much more efficiently exploited in CFST beams than in ST beams. The mean ductility of 8.19 classified CFST beams to be highly ductile. The average plastic hinge length approximately equals the height of CFST beams. An available model was used to predict the moment capacity of CFST beams, and the results confirmed the accuracy of the model. Results of reliability analyses showed that mean moment capacity was independent on any individual variable or a combination of variables. In contrast, the standard deviations heavily depended on the considered variables. Consequently, the reliability index due to variable of steel thickness is the highest at 32.2, followed that due to the steel strength at 24.5, whereas those due to other variables varied from 8.0 to 9.3.

Development of AI based analysis tools for online monitoring of steel-making process

Mechanical properties of steel are closely monitored during the manufacturing process through various non-destructive techniques. The IMPOC device implements one of them and is used by steel manufacturers at several locations of the production line. It provides a fast electromagnetic measurement that is strongly correlated with the microstructural state of the steel, hence its use to check online the uniformity of the semi-final or final product. Tata Steel, CEA LIST and SSSA have worked together to analyse IMPOC datasets corresponding to various situations in terms of steel coils and process conditions. A data driven model has been built from field measurements using a specific neural network architecture. This model proves useful to investigate the complex relations between numerous process parameters and the IMPOC value. This communication presents the approach followed to build the data driven model using neural networks and to check its relevance. The relationship between the measurement on one side and the process parameters and material composition on the other side are then investigated by means of several sensitivity analysis and feature importance techniques.

A mini-review of surface severe plastic deformation methods and their effects on steel and stainless steel

Surface severe plastic deformation is an important technology for the preparation of bulk ultrafine grain or even nanocrystalline materials. Based on the technical achievements made in the field of surface severe plastic deformation at home and abroad, this article presents the basic principles of various kinds of surface severe plastic deformation techniques in detail. In addition, the effects of surface severe plastic deformation on the microstructure and mechanical properties of steel and stainless steel are reported. The current status of research on the effects of surface severe plastic deformation on fatigue properties and the tribological and biological properties of steel and stainless steel are summarized. The problems of the current surface severe plastic deformation technology for steel and stainless steel are pointed out, and the future development trend is foreseen.

Effects of Mo and Controlled Cooling on Microstructure and Properties of Thick‐Wall High‐Strength Pipeline Steel

Herein, the effect of molybdenum (Mo) and postrolling cooling processes on the mechanical properties and microstructure transformation characteristics of an X80 thick‐wall high‐strength pipeline steel are deeply investigated. The results reveal that the yield strength and tensile strength of the steel are enhanced with Mo addition at the equalization temperature of 480 °C at a cooling rate of 25 °C s−1, accompanied by the improvement in the yield ratio. However, when the postrolling cooling temperature is reduced to 380 °C, the mechanical properties of steels with Mo‐free and 0.29 wt% Mo are comparable. The mechanistic study indicates that the Mo addition would inhibit the transformation from deformed austenite to polygonal ferrite, and promote the transformation of acicular ferrite/granular bainite at medium–low temperatures, as well as significant differences in the volume fraction, size, and morphology of martensite/austenite (M/A) in the matrix. Notably, the volume fraction of M/A decreases from 7.2% to less than 1.0% with Mo content increasing, while its average size also reduces from 1.5 to less than 1.0 μm. And the fine, spheroidal, and dispersed M/A is found to play a vital role in the high‐strength and excellent low‐temperature toughness of the steel.

Microstructure evolution and strain hardening behavior of thermomechanically processed low-C high-manganese steels: an effect of deformation temperature

Effects of reduced (– 40 °C), ambient (20 °C), and elevated (200 °C) deformation temperatures on the microstructure evolution and strain hardening behavior of two low-C thermomechanically processed high-manganese steels were studied. The microstructure was characterized by means of scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM) techniques. The temperature-dependent tendency of austenite to strain-induced ε/α′-martensitic transformation and mechanical twinning was qualitatively and quantitatively assessed using the EBSD technique. The steel containing 26 wt% of Mn showed the beneficial strength–ductility balance at reduced deformation temperature -40 °C due to the intense Transformation-Induced Plasticity (TRIP) effect which resulted in the formation of significant ε- and α′-martensite fractions during tensile deformation. The mechanical properties of steel containing 27 wt% of Mn were more beneficial at elevated deformation temperature 200 °C due to the occurrence of intense Twinning-Induced Plasticity (TWIP) effect expressed by the presence of significant fraction of mechanical twins. Moreover, at the highest deformation temperature 200 °C, the evidence of thermally activated processes affecting the mechanical behavior of the higher Mn steel was identified and described.

Heating duration effects on post-fire structural steel mechanical properties

Post-fire mechanical assessment of steel structures is challenging due to the changes in mechanical properties from the heating and cooling phases of a fire. While the effects of cooling rate and temperature of exposure have been researched in depth, the effects of heating duration are not comprehensive. This paper investigates the effects of heating duration on post-fire A572 Gr. 50 steel mechanical properties over a temperature range of 500–800 °C for durations of 0.5 and 2.0 h. Specimens are subjected to tensile testing in accordance with ASTM A370, Vickers microhardness testing, and optical microscopy. The findings suggest that heating duration has an influence on the post-fire mechanical properties of steel at elevated temperatures (700, 800 °C). At these temperature exposures, retention of yield stress, retention of ultimate stress, and microhardness all decrease. Members subjected to 700 °C for 0.5 h have more retention in yield stress and microhardness compared to those exposed for 2.0 h, while the 800 °C conditions show little difference in mechanical properties between exposure times. The results of this study show that the duration of fire exposure is an important factor when estimating the mechanical properties of fire-exposed steels, in addition to the temperature and cooling rate.

Mechanical properties and constitutive model of Q460 steel during the fire-cooling stage

The mechanical properties of steel under fire-induced elevated temperatures is fundamental and crucial for structural fire-resistance design and analysis. Mechanical properties of high-strength steel (HSS) during the fire-heating and post-fire stages have been extensively investigated, while those during the fire-cooling stage were rarely studied. This study investigated the mechanical properties of HSS Q460 during the fire-cooling stage by steady-state tensile experiments Results show that the mechanical performance of HSS Q460 at the fire-cooling stage is not only related to the test temperature (Tt) but also the peak heating temperature (Tp) before cooling for tests. The strength of HSS Q460 at identical Tt shows an overall download trend with the increase of Tp. The mechanical properties of HSS Q460 at the fire-cooling are similar to those at the fire-heating stage when Tp is not greater than a certain value. This value is 600 °C for Young’s modulus and yield strength f0.2, and 400 °C for yield strength f1.0, f2.0 and ultimate strength. When Tp exceeds certain values, the Young’s modulus and strengths at the fire-cooling stage are less than those at the fire-heating stage. Moreover, the mechanical properties of HSS Q460 were compared with those of HSS Q690, indicating that the degradation rules of mechanical properties of HSSs Q460 and Q690 differ during the fire-cooling stage. Besides, formulas were proposed to calculate the mechanical properties and stress–strain relationship of the HSS Q460 during the fire-cooling stage.

Mechanical properties of carbon steel under uniaxial static tension

With the continuous development of science and technology, carbon steel is widely used in production and life. Especially at the practical application level, in the engineering application, the analysis of the mechanical properties of carbon steel materials has become increasingly prominent. The tensile test is a mechanical property test in which a standard tensile specimen is pulled to fracture at a specified tensile speed under the continuous action of static axial tensile force. The force and elongation are continuously recorded during the tensile process so as to obtain its strength criterion and plasticity criterion. In this paper, the characteristics of mechanical properties of the high, medium, and low carbon steels under uniaxial static tension are discussed. The reasons for the different mechanical properties of steels with different carbon content are explained from a microscopic perspective. The study provides some basic assistance to those who need relevant information.