Mechanical Properties Of Low-alloy Steels Research Articles

Improving Support Vector Regression for Predicting Mechanical Properties in Low-Alloy Steel and Comparative Analysis

Low-alloy steel is widely employed in the aviation industry for its exceptional mechanical properties. These materials are frequently used in critical structural components such as aircraft landing gear and engine mounts, where a high strength-to-weight ratio is crucial for optimal performance. However, the mechanical properties of low-alloy steel are influenced by various components and their compositions, making identification and prediction challenging. Accurately predicting these mechanical properties can significantly reduce the development time of new alloy steel, lower production costs, and offer valuable insights for design analysis. support vector regression (SVR) is known for its superior learning and generalization capabilities. However, optimizing SVR performance can be challenging due to the significant impact of the penalty factor and kernel parameters. To address this issue, a hybrid method called SMA-SVR is proposed, which combines the Slime Mould Algorithm (SMA) with SVR. This hybrid approach aims to efficiently and accurately predict two crucial mechanical parameters of low-alloy steel: tensile strength and 0.2% proof stress. Detailed descriptions of the modeling processes and principles that are involved in the hybrid method are provided. Furthermore, three other popular hybrid models for comparison are introduced. To evaluate the performance of these models, four statistical measures are utilized: Mean Absolute Error, Root Mean Square Error, R-Squared, and computational time. Using data from the NIMS database and from material tests conducted on a universal testing machine, experiments were carried out to compare the performance of these models. The results indicate that SMA-SVR outperforms the other methods in terms of accuracy and computational efficiency.

Spall properties and damage mechanisms of a low-alloy steel fabricated via laser powder bed fusion

Plate impact experiments are conducted on a representative, low-alloy, 24CrNiMo steel (containing lath martensite substructures) fabricated via laser powder bed fusion and tempering, to investigate its spall strength and damage mechanism within a peak stress range of 5–11 GPa. The Hugoniot elastic limit (2.4 GPa) and spall strengths (3.9–4.2 GPa) are obtained from free surface velocities, and show negligible anisotropy. The microstructure before and after impact loading are characterized by electron backscatter diffraction and scanning electron microscopy. The length, width and orientation angle of cracks are quantified. Spall cracks are large in quantity, but small in mean propagation distance and opening displacement, especially at high peak stress. Cracks develop mainly along the {100} cleavage planes of laths of the same variant rather than along melt pool boundaries. The mismatch between the {100} cleavage planes across the ∼60°〈111〉 lath boundaries leads to high resistance of fine laths against crack propagation. The fine lath substructure is beneficial to the dynamic mechanical properties of low-alloy steels.

Effect of an Overequilibrium Nitrogen Content on the Structure, Phase Composition, and Mechanical Properties of Low-Alloy Steel

Effect of an Overequilibrium Nitrogen Content on the Structure, Phase Composition, and Mechanical Properties of Low-Alloy Steel

On the Influence of Internal and External Factors on the Processes of Corrosion-Mechanical Fracture of High-Strength Low-Alloy Steels

The article studies the influence of internal and external factors on the process of corrosion-mechanical fracture. It is shown that depending on the conditions of hydrogen charging (temperature and chemical composition of the corrosive medium, type of polarization), the mechanical properties of low-alloy steels change dramatically during the initial period of the experiment. With further increase in the holding time in a corrosive medium without polarization, there is no significant change in mechanical properties. It was found that an increase in the level of applied tensile stresses leads to a reduction in the incubation period of microcracks during hydrogen cracking. It was found that the sensitivity of low alloy steels to cracking is largely determined by the relaxation ability of the structure-the relaxation of residual peak micro-stresses localized at the grain boundaries and substructure boundaries reduces the sensitivity to corrosion-mechanical fracture.

The Role of Ferrotitanium as an Inoculant on the Microstructure and Mechanical Properties of Low-Alloy Steel

Abstract In this work, the effects of ferrotitanium (0.5 wt.%) as an inoculant on the microstructure and mechanical properties of 0.24 % carbon-1 % chromium-1 % manganese-0.5 % silicon steel were studied. Optical microscopy and scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS) microanalysis were used for microstructural investigations. The phase structure of the ferrotitanium-added alloys was studied using X-ray diffraction (XRD). Microstructural observations show that a fine upper bainite lath is formed and allotriomorphic ferrite is eliminated by adding ferrotitanium to the main alloy. XRD revealed the presence of ferrite and austenite in the microstructure. Also, a decrease in dendrite arm spacing (DAS) was observed for 0.5 wt.% ferrotitanium-added alloy. Addition of 0.5 wt.% ferrotitanium caused the formation of titanium-molybdenum-carbon precipitates in austenite grain boundaries so that these particles acted as nucleon’s in austenite grain boundary and refined the microstructure. The yield strength, ultimate tensile strength, and percent elongation to fracture of the ferrotitanium-added samples are increased by 65, 68, and 57 %, respectively. Finally, the fracture surface of the alloys showed a cleavage fracture for the inoculated alloy.

Influence of pulsed-arc welding conditions on change of parameters of weld and haz of welded joints and mechanical properties of low-alloy steels

The Paton Welding Journal, 2020, №12. International Scientific-Technical and Production Journal «The Paton Welding Journal» «The Paton Welding Journal» has been published monthly since 2000 in English, ISSN 0957-798X. «The Paton Welding Journal» is a cover-to-cover English translation of the «Avtomaticheskaya Svarka» (Automatic Welding) journal. The «Avtomaticheskaya Svarka» journal has been published monthly since 1948 in Russian, ISSN 005-111X.

Modeling and Composition Design of Low-Alloy Steel's Mechanical Properties Based on Neural Networks and Genetic Algorithms.

Accurately improving the mechanical properties of low-alloy steel by changing the alloying elements and heat treatment processes is of interest. There is a mutual relationship between the mechanical properties and process components, and the mechanism for this relationship is complicated. The forward selection-deep neural network and genetic algorithm (FS-DNN&GA) composition design model constructed in this paper is a combination of a neural network and genetic algorithm, where the model trained by the neural network is transferred to the genetic algorithm. The FS-DNN&GA model is trained with the American Society of Metals (ASM) Alloy Center Database to design the composition and heat treatment process of alloy steel. First, with the forward selection (FS) method, influencing factors—C, Si, Mn, Cr, quenching temperature, and tempering temperature—are screened and recombined to be the input of different mechanical performance prediction models. Second, the forward selection-deep neural network (FS-DNN) mechanical prediction model is constructed to analyze the FS-DNN model through experimental data to best predict the mechanical performance. Finally, the FS-DNN trained model is brought into the genetic algorithm to construct the FS-DNN&GA model, and the FS-DNN&GA model outputs the corresponding chemical composition and process when the mechanical performance increases or decreases. The experimental results show that the FS-DNN model has high accuracy in predicting the mechanical properties of 50 furnaces of low-alloy steel. The tensile strength mean absolute error (MAE) is 11.7 MPa, and the yield strength MAE is 13.46 MPa. According to the chemical composition and heat treatment process designed by the FS-DNN&GA model, five furnaces of Alloy1–Alloy5 low-alloy steel were smelted, and tensile tests were performed on these five low-alloy steels. The results show that the mechanical properties of the designed alloy steel are completely within the design range, providing useful guidance for the future development of new alloy steel.

Incipient corrosion behavior and mechanical properties of low-alloy steel in simulated industrial atmosphere

Low-alloy steel is widely used in the structures. However, the corrosion problem is very common for low-alloy steel, which would result in the degradation of mechanical properties and the decrease of effective area of steel member. In this paper, the incipient corrosion behavior and mechanical properties of low-alloy steel were studied. Dog-bone steel specimens were artificially corroded through salt spray tests. Based on the experimental results, the incipient corrosion process was detailed presented, and different characterizations of the bottom surface and the top surface of the corroded specimen were analyzed. Then the stochastic distribution function and the time-dependent model of mass loss ratio were presented. At last, through the tensile coupon tests, the influence of corrosion levels on the final elongation ratio, elastic modulus, yielding stress and ultimate strength of low-alloy steel was presented and analyzed.

Effects of the welding inclusion and notch on the fracture behaviors of low-alloy steel

Effects of the welding inclusions and notches on the deformation and fracture behaviors of low-alloy steels were investigated by combining the tensile performance testing and acoustic emission (AE). The micro-structures and fracture surfaces of the hot-rolled and welded samples were observed by OM and SEM. It was found out that the welding inclusions and notches would result in negative impacts on the mechanical properties of low-alloy steel. During the fracture process of the welds, there were four groups of the AE frequencies, representing three kinds of deformation and fracture behaviors: plastic deformation of the welding matrix, fracture of the welding matrix, and fracture or interface detachment of the welding inclusions. Plastic deformation of the welding matrix mainly took place in the plastic stage and the late hardening stage. Fracture of the welding matrix and inclusions were concentrated in the first half of the hardening stage.

The Influence of Austenite Grain Size on the Mechanical Properties of Low-Alloy Steel with Boron

This study forms part of the current research on modern steel groups with higher resistance to abrasive wear. In order to reduce the intensity of wear processes, and also to minimize their impact, the immediate priority seems to be a search for a correlation between the chemical composition and structure of these materials and their properties. In this paper, the correlation between prior austenite grain size, martensite packets and the mechanical properties were researched. The growth of austenite grains is an important factor in the analysis of the microstructure, as the grain size has an effect on the kinetics of phase transformation. The microstructure, however, is closely related to the mechanical properties of the material such as yield strength, tensile strength, elongation and impact strength, as well as morphology of occurred fracture. During the study, the mechanical properties were tested and a tendency to brittle fracture was analysed. The studies show big differences of the analysed parameters depending on the applied heat treatment, which should provide guidance to users to specific applications of this type of steel.

Influence of Short Austenitization Treatments on the Mechanical Properties of Low-Alloy Steels for Hot Forming Applications

The current work elucidates an improvement of the mechanical properties of tool-quenched low-alloy steel by employing extremely short austenitization durations utilizing a press heating arrangement. Specifically, the influence of different austenitization treatments—involving austenitization durations ranging from three to 15 seconds—on the mechanical properties of low-alloy steel in comparison to an industrial standard furnace process was examined. A thorough set of experiments was conducted to investigate the role of different austenitization durations and temperatures on the resulting mechanical properties such as hardness, bending angle, tensile strength, and strain at fracture. The most important finding is that the hardness, the bending angle as well as the tensile strength increase with shortened austenitization durations. Furthermore, the ductility of the steels exhibits almost no difference following the short austenitization durations and the standard furnace process. The enhancement of the mechanical properties imposed by the short heat treatments investigated, is related to a refinement of microstructural features as compared to the standard furnace process.

Effect of Heat Treatment Parameters on the Mechanical and Microstructure Properties of Low-Alloy Steel

This study examines the effect of heat treatment at three different temperatures of 800°C, 950°C and 1100°C on the microstructure and mechanical properties of low-alloy steel with an addition of manganese, chrome and lead. To determine an impact of the applied heat treatment operations, testing of mechanical properties and microstructural examinations of the steel with 0.23%, 0.24%, 0.29% and 0.31% C were conducted. This work shows that the mechanical strengths of the alloy steel are improved with increasing the heat treatment temperature. In addition, the microstructure trends toward recrystallized ferrite grains as the heat treatment temperature increases.

Experimental research on the effect of induction reheating on the microstructure and mechanical properties of hot-rolled low-alloy steel plate

Electric induction reheating is used to control the temperature of hot-rolled steel products. To investigate the effect of this on microstructure and mechanical properties, hot-rolled low-alloy steel plate was cooled, reheated, and then either quenched or normalized. Analysis of the microstructure and mechanical properties showed that this process had a greater effect on quenched steel plate than on normalized steel plate. Reheating was found to affect the precipitation of alloy carbonitrides, and the recovery and recrystallization of deformed austenite. In the single-phase region, the lower cooling temperature resulted in better mechanical properties. In normalized steel plate, the interlamellar spacing of pearlite (ISP) increased from 118nm to 165nm after induction reheating. In steel plate quenched with a 70oC temperature difference, induction reheating reduced the strength difference from 80MPa to 23MPa. Our results provide useful references for optimizing electric induction and improving the uniformity of the mechanical properties of low-alloy steel.

The analysis of phase transformation of undercooled austenite and selected mechanical properties of low-alloy steel with boron addition

The paper presents continuous cooling transformation (CCT) diagram of selected low-alloy boron steel with high resistance to abrasion. Tests were performed on samples with dimensions of Ø 3mm×10mm. Samples were prepared from examined material in as – delivery conditions, then were austenitized at 930°C for 20min, and then cooled with the rates of V800-500=0.17, 0.33, 1, 5, 10, 25 and 47°C/s. During the dilatometric research, the critical temperatures were defined as well as the critical points specified for different cooling rates were designated. In addition, metallographic documentation of received microstructures after dilatometric investigations was prepared and hardness measurement was performed. Moreover, examinations of the basic parameters of strength, impact test and abrasion resistance test were performed and a tendency to brittle fracture was analyzed. The studies show big differences of the analyzed parameters depending on the applied heat treatment, which should provide guidance to users to specific applications of this type of steel.

Effects of RE on Microstructure and Mechanical Properties of Low-Alloy Steel

The effect of rare earth element on structure and mechanical properties of SS400 steel were studied by metallographic examination, scanning electron microscope (SEM), tensile test and impact test. The results show that rare earth can refine microstructure of SS400 steel. Fracture is changed from cleavage to ductile fracture by adding RE to SS400 steel. And the mechanical properties of SS400 are improved. The impact toughness value of SS400 steel (containing 0.02 RE) increases by 39.66% at -40°C, and at 0°C the impact toughness value increases by 31.05%, respectively comparing with that of steel without RE.

Influences of Hot Rolling Conditions on the Microstructure and Mechanical Properties of Low-Alloy Steel

The thermomechanical control processing (TMCP) was conducted through the adjustment of the rolling technological parameters to the test steel. The influence of the finishing temperature, cooling rate and alloying elements to the microstructure and mechanical properties was investigated by comprehensive utilization of grain refining strengthening and second phase strengthening.The results show that the microstructure was mainly composed of bainite, ferrite and second phase TiC; at the finishing temperature of 870°C, the yield strength was 596.7 MPa, the tensile strength reached 748.5 MPa, the elongation ratio was 20.17%; at high cooling rate of 16°C/s, the yield strength achieved 616.7 MPa, the tensile strength reached 785.5 MPa, the tensile ratio reduced for 0.78, and the elongation ratio enhanced to 20.92%. And the quantity of bainite increased with the raise of finishing temperature from 800°C to 870°C, which improved the hardness and wear resistance of the steel.

Ductile-brittle transition in steels at near-solidus temperatures

A complex study of the nature of the little-investigated phenomenon of high-temperature brittleness of steels, i.e., the ductile-brittle transition observed in the temperature range t = (0.92–0.98)tmelt, is described. Regular features in the behavior of mechanical properties of low-alloy steels in this temperature range are considered. The effects of the chemical composition (carbon, impurities), preliminary plastic deformation, high-temperature annealing, and test medium on the mechanical properties are studied. Special features of the fracture mechanism at the studied temperatures are described.

Corrosion resistance and mechanical properties of low-alloy steels under atmospheric conditions

The corrosion resistance and mechanical strength of four newly developed low-alloy steels (LAS) were compared with a carbon steel (SS400) and a weathering steel (Acr-Ten A) using a laboratory-accelerated test that involved cyclic wet/dry conditions in a chloride environment (5 wt.% NaCl). The new LAS were designated 1605A, 1605B, 1604A, and 1604B. After 72 cycles of cyclic corrosion tests, the susceptibility of the steels to corrosion could be listed in the following order based on their weight loss (from high to low): SS400 > Acr-Ten A > 1604B ⩾ 1604A > 1605B ⩾ 1605A. The change in mechanical properties by corrosion was the least for SS400, Acr-Ten A was second, and effects of corrosion on the mechanical properties of the other four low-alloy steels were similar. Finally, the characteristics of the rust layers on each LAS sample were observed by SEM, and analyzed by FTIR and EPMA. The results indicated that most of the rust layers on the test steels were composed of a loose outer rust layer and a dense inner rust layer. The outer rust layer of each steel was composed of α-FeOOH, γ-FeOOH, magnetite (Fe 3O 4), H 2O, and amorphous ferric oxyhydroxide (FeO x (OH) 3−2 x , x=0–1), while the inner rust layer was composed mainly of Fe 3O 4 with a little α-FeOOH. In addition, it was apparent that the copper and chromium alloying additions were enriched, respectively, at the rust-layer/substrate interface and in the rust layers. Finally, combining the results of the accelerated tests and the rust layer analysis showed that low-alloy steels, such as 1605A and 1605B, have better weathering steel properties than Acr-Ten A for use in the humid and salty weather.

Mechanoelectrical heat treatment of low-alloy steels with 0.3?0.6% C

The use of elevated heating rates in heat treatment of steel products promotes structural states in them that are characterized by improved mechanical and operating properties and in most cases cannot be attained under conditions of conventional heating in furnaces. In the present work the structure and mechanical properties of low-alloy steels after their thermal strengthening by the method of mechanoelectrical heat treatment (MEHT) are described.

Investigation of the mechanical properties of low-alloy steels

Investigation of the mechanical properties of low-alloy steels