Mechanical Properties Of Alloy Steels Research Articles

Study on correlation and scaling protocol between indentation stress-strain and uniaxial stress-strain

Most important mechanical structures produce complex local material changes during the moulding and servicing process. Obtaining the specific local mechanical properties of materials and conducting field tests are problems in structural integrity evaluation. The instrumented indentation technique (IIT) is a solution to these problems. However, the core challenge with the IIT is the quantitative correlation between indentation response and uniaxial stress-strain (USS) response. In this study, we investigate the scaling relationship between indentation stress-strain (ISS) and uniaxial stress-strain (USS). A new protocol for obtaining the mechanical properties of alloy steels using ISS curves is proposed, which can directly obtain the plastic stage of the USS curves from the ISS curves. We used a finite element inversion method based on existing theories. Models with different mechanical properties (USS curves) were established using the ABAQUS software to obtain the corresponding ISS curves. We then explored the relationship between the two; the strain-scaling factor and stress-scaling function were specifically identified. Our work proposes an ISS protocol for power-law-hardening materials. Two alloy steels (SA508 and 42CrMo) were experimentally verifieds. The predicted results are approximately consistent with the practical curves and the error was within ± 10%. Because of the universality and reliability of the protocols, it is expected to provide a theoretical reference and technical approach for the development of IITs and structural integrity evaluation of important mechanical structures.

Effects of Alloying Element and Heat Treatment on Mechanical Properties of Alloy Steels

The effects of Cr and Ni on three different types of steel with different carbon ratios under constant conditions such as the welding current 120A, voltage 80V, Diameter 10 mm and angle 60 degree was observed. Nickel percentage of up to 0.147% and Chromium 0.083% contributed to affecting the mechanical properties of the steel. Undissolved carbide particles refine the austenite grain size. In the presence of nickel, chromium carbide is less effective in austenite grain refinement than chromium carbide in absence of nickel at temperature below 975°C. Nickel does not produce any austenite grain refinement but presence of nickel promotes the formation of acicular ferrites. It was also found that Ni and Cr as chromium carbide also refines the ferrite grain size and morphology. Cr as chromium carbide is more effective in refining ferrite grain size than nickel. The microstructure of the base metal as a reference material was analysed before heating to support the results of chemical analysis. Nickel percentage of up to 0.147% and Chromium 0.083%. Molybdenum was 0.03% which contributed to affecting the mechanical properties of the steel.Keyword: Alloy steel, Heat treatment, Chromium, Nickel, Grain size

Austenite Grain Growth Behaviors of La-Microalloyed H13 Steel and Its Effect on Mechanical Properties

Controlling austenite grain size is an effective method to improve mechanical properties of alloy steels. This article shows that La addition can effectively restrain the growth of austenite grains in H13 steel and make the grain size distribution more uniform. When holding at 1050 °C from 10 to 180 minutes, the average austenite grain of La-microalloyed H13 steel increases by 35.7 pct, while that of La-free H13 steel increases by 66.7 pct. With the extension of austenitizing time, the decrease in the strength and the plasticity of tempered La-microalloyed H13 steel is considerably less than those of tempered La-free H13 steel. Austenitized at 1050 °C for 180 minutes, the tensile strength and the elongation to failure of the tempered La-microalloyed steel are 1895 MPa and 9.3 pct, respectively. The addition of La increases the amount of undissolved carbide V8C7 and refines the carbide, and La2O2S particles with high melting point are detected. Because of the combined effect of these fine dispersed second-phase particles, the pinning effect on grain boundary migration increases, and the grain growth is restrained. Some martensitic substructures transform from twin configuration to dislocation configuration because of La addition, and the lath bundles of martensite are refined. As a result, the strength and the toughness of the steel are improved.

Experimental investigations on Deformation, Densification and Mechanical properties of sintered Fe-C-Mn low alloy P/M steels under hot upsetting

The present research work pertains to the study of deformation and densification characteristics and mechanical properties of Mn added low alloy steels. The sintered and hot upset powder metallurgy (P/M) low alloy steels such as Fe-0.2%C, Fe-0.2%C-0.5%Mn and Fe-0.2%C-2.0%Mn were used for the plastic deformation, densification and mechanical properties of the alloy steels. The surface morphology of the specimens was correlated to the deformation, densification and mechanical properties of the low alloy steels. It is observed that addition of Mn affects the plastic deformation property of the material and enhances the mechanical strength of the P/M alloy steel.

Probe of Interrelation of Indicators of Static Plasticity and Strength of Heat-treated Alloyed by Steels

Investigated the relationship between the parameters of static plasticity and strength based on the mechanical properties of alloy steels. Well known theoretical and applied interest is the relationship between indicators static plasticity and hardness. For establishing considered the mechanical properties of alloy steels after different modes of sorbitizing and quenching with autotempering. In the study had used previously proposed dimensionless coefficients. In most of the reviewed options steels after sorbitizing and quenching with autotempering there is a close correspondence of the calculated and experimental values temporal tear resistance.

An Integrated System Approach for Solving Multi-Objective Scheduling Problems and Advanced Control of an Experimental Hot-Rolling Mill

AbstractCommon to most industries, the metal industry is having to ‘rethink’ its short and long term strategies when it comes to producing metals to customers’ specifications. Indeed, metal producers are having to balance the requirements for more consistent and higher quality rolled products with those that are associated with greater efficiencies in energy costs and impact on environment. In the light of these considerations, the performance of key industrial systems such as hot-rolling mills must be carefully analysed in search of further improvements. Criteria for optimising hot-rolling of steel include system efficacy, advanced control strategies, optimal rolling schedule and product quality. This paper is the result of the authors’ extensive study on the use of advanced technologies and new integrated approaches in the field of optimal scheduling for the hot-rolling process. The proposed design is based on 1. a multi-objective optimisation-based Population Adaptive Immune Algorithm (PAIA); 2. physically-based models and Symbiotic data-driven modelling for the accurate prediction of mechanical properties of alloy steels; 3. advanced control, including Adaptive Fuzzy Generalised Predictive Control (AFGPC) to guarantee the optimal performance of the mill during the rolling process. Hence, the overarching aim of this research work is to integrate knowledge about both the stock and the rolling process to identify the optimal hot-deformation profiles in order to compute the most suitable rolling schedule and systematically ‘chart’ the optimal routes for processing and hence achieve ‘right-first-time’ production of these alloy steel via the desired final microstructure and mechanical properties.

A hierarchical Mamdani-type fuzzy modelling approach with new training data selection and multi-objective optimisation mechanisms: A special application for the prediction of mechanical properties of alloy steels

In this paper, a systematic data-driven fuzzy modelling methodology is proposed, which allows to construct Mamdani fuzzy models considering both accuracy (precision) and transparency (interpretability) of fuzzy systems. The new methodology employs a fast hierarchical clustering algorithm to generate an initial fuzzy model efficiently; a training data selection mechanism is developed to identify appropriate and efficient data as learning samples; a high-performance particle swarm optimisation (PSO) based multi-objective optimisation mechanism is developed to further improve the fuzzy model in terms of both the structure and the parameters; and a new tolerance analysis method is proposed to derive the confidence bands relating to the final elicited models. This proposed modelling approach is evaluated using two benchmark problems and is shown to outperform other modelling approaches. Furthermore, the proposed approach is successfully applied to complex high-dimensional modelling problems for manufacturing of alloy steels, using ‘real’ industrial data. These problems concern the prediction of the mechanical properties of alloy steels by correlating them with the heat treatment process conditions as well as the weight percentages of the chemical compositions.

Mamdani-Type Fuzzy Modelling via Hierarchical Clustering and Multi-Objective Particle Swarm Optimisation (FM-HCPSO)

In this paper, a systematic data-driven fuzzy modelling approach is proposed, which integrates transparent fuzzy systems (linguistic fuzzy systems) with an effective evolutionary computing based algorithm - the new structure Particle Swarm Optimisation (nPSO). In this modelling mechanism, a new data clustering technique via an improved hierarchical clustering algorithm is designed for the initial fuzzy model generation. Multi-objective optimisation techniques are then employed for the improvement of the generated fuzzy model, which takes into account both the accuracy and the interpretability performances of the fuzzy system. This proposed modelling approach is tested on two benchmark problems and a high-dimensional modelling problem using real industrial data. This latter concerns the prediction of the mechanical properties of alloy steels. Experimental results show that the proposed approach is very effective in eliciting accurate as well as interpretable Mamdani-type fuzzy models.

FUZZY PREDICTIVE MODELLING USING HIERARCHICAL CLUSTERING AND MULTI-OBJECTIVE OPTIMISATION FOR MECHANICAL PROPERTIES OF ALLOY STEELS

In this paper, a systematic data-driven fuzzy predictive modelling mechanism is proposed. In this mechanism, a hierarchical clustering algorithm, the agglomerative complete-link clustering algorithm, is first employed to extract an initial fuzzy model. Then, the initial model is improved and optimised through a two-step operation using evolutionary algorithms (EAs), which takes into account both the accuracy and the interpretability performance of the fuzzy system. The proposed modelling approach is tested on a high dimensional problem using real data from the steel industry which concerns the prediction of the mechanical properties of alloy steels, in particular the Tensile Strength (TS). Experimental results show that the proposed approach is effective in eliciting accurate and interpretable models while ensuring their future easy maintenance.

Low temperature aluminisation of alloy steels by pack cementation process

The pack aluminisation process is normally applied at temperatures >973 K at which the mechanical properties of alloy steels would degrade. Thus, the present study was undertaken to apply this process to aluminising the alloy steels at temperatures <973 K in order to increase their high temperature oxidation resistance while maintaining their microstructure and hence mechanical strength and creep resistance. A type of commercial alloy steel P92 (9Cr–1Mo) was used for the present study. Pack powder mixtures consisting of Al, AlCl3 (anhydrous) or NH4Cl and Al2O3 were used to carry out the process. The aluminising temperature was varied from 773 to 973 K, pack Al content from 1 to 30 wt-% and aluminising time from 1 to 16 h to investigate their effects on the coating growth kinetics in the AlCl3 activated packs. It was observed that all the coatings formed in the AlCl3 activated packs were of a single layer structure with Fe2Al5 as the main coating phase. It was established that the interrelationship between the thickness h (in μm) of this coating layer and aluminising temperature T (in K), time t (in h) and pack Al content W (in wt-%) can be described by h=83005·9W1/2t1/2e−73330/(RT). In the NH4Cl activated packs, it was found that coating formation and dissolution took place simultaneously at 923 K and stable growth of a coating layer was only possible when the pack Al content was sufficiently high. However, the coatings formed in these packs had highly uneven regions.

Electrochemical and mechanical properties of alloy steels implanted by nitrogen ions

The alloy steels 1Cr13, 1Cr18Ni9 and 6Cr3Mo1V were implanted by nitrogen ions (with doses in the range of 5 × 10 16−4 × 10 17 cm −2). Potentiodynamic curves for 1Cr13 and 1Cr18Ni9 steels were measured in a solution of H 2SO 4. In the case of 1Cr13 steel the corrosion current was only slightly reduced, whereas in the case of 1Cr18Ni9 steel the corrosion current was reduced greatly. Potentiodynamic curves for the 6Cr3Mo1V steel were measured in a solution of CH 3COONa· 3H 2O. The corrosion current decreased with increasing dose. The dependence of microhardness and wear on the dose of implanted atoms is also presented.

Interrelations of compositions, transformation kinetics, morphology, and mechanical properties of alloy steels

The strong influence of the fine-scale microstructural features on mechanical properties has become increasingly evident during the past decade. This is particularly true for fracture toughness of quenched and tempered alloy steels. Large differences in microstructure can be produced by isothermal, rather than athermal, treatments in the bainite and upper martensite temperature ranges. The kinetics of transformation, as well as the kinds and volume fractions of transformation products can be varied o ver wide ranges by relatively small changes in chemical composition. The effects of the common alloying elements on transformation kinetics, both separately and in various combinations were determined experimentally. The synergistic effects of individual elements added as pairs of elements were not predictable from a knowledge of the effects of the individual elements. Isothermal treatments, coupled with variations in the kinds and amounts of alloying elements, produced different morphologies, compositions, and volume fractions of the transformation products. The effects of such microstructural differences on tensile properties, fracture toughness, and fatigue characteristics were evaluated. Beneficial effects were found, such as substantial increases in fracture toughness, with small changes in alloy content or with heat treatments that differed from those conventionally used.

An investigation of the effect of chemical composition on the mechanical properties of alloy steels using statistical methods

An investigation of the effect of chemical composition on the mechanical properties of alloy steels using statistical methods

Ultrafine-grained microstructures and mechanical properties of alloy steels

Ultrafine-grained microstructures can be developed in a variety of alloy steels by coldworking followed by annealing in theα +γ region. Because the annealing temperatures are relatively low and the recrystallized structure is two-phase, grain growth is restricted. Specimens with grain sizes in the range 0.3 to 1.1 μ.m (ASTM 20 to 16) were obtained in manganese and nickel steels by annealing 1 to 400 hr at temperatures between 450° and 650°C (840° to 1200°F). The expected improvement in yield strength through grain refinement was observed in almost all alloys. Other tensile properties depend on factors such as grain size, austenite stability, and specimen geometry, that determine which of three types of plastic behavior will occur. Transformation of austenite during straining improves the mechanical properties of ultrafine-grained specimens.

The effect of neutron irradiation on the structure and mechanical properties of alloy steels

We have studied the effect of neutron irradiation at temperatures of 200–500°C with various integral doses (1.5·1020·1021 neutrons/cm2) on the properties and microstructure of some steels with different chemical compositions and initial structures. We have shown the effect of alloying by various elements on the sensitivity of the steel to irradiation and the temperature of annealing of radiation defects of hardening.