Production Of High-strength Steels Research Articles

Artificial neural network method in solving smart cities construction fuzzy multi-objective linear programming problems

Nowadays, the increasing demands of smart cities require innovative technologies to optimize resource utilization and minimize costs. This research focuses on the construction sector, specifically the production of advanced high-strength steel. We address practical application problems from the iron and steel factory in Annaba, Algeria, known as fuzzy multi-objective linear programming problems. Two methods are applied: a mathematical model and Artificial Neural Networks (ANNs). Results indicate that the ANN approach offers significant time and effort savings.

Development and Production of New High-Strength Steel

Development and Production of New High-Strength Steel

In situ measurement of austenite grain growth and recrystallization using laser ultrasonics

The development of next generation process models and advanced high-strength steel products for thin slab casting and direct rolling requires quantification of microstructure evolution during thermomechanical processing. Laser ultrasonics is a non-contact in-situ method to record grain growth, recrystallization and phase transformations in metals and alloys. Here, we will present an improved experimental design that facilitates a continuous microstructure measurement through the various stages of simulated hot rolling from reheating to runout table cooling using a Gleeble thermomechanical simulator equipped with a laser ultrasonics for metallurgy (LUMet) system. Austenite grain growth and static recrystallization after hot deformation are quantified based on attenuation of the ultrasound waves whereas austenite decomposition can be recorded with the changes in ultrasound velocity during the phase transformation. Further, the LUMet results for a microalloyed low carbon steel are validated with conventional techniques including optical and electron microscopy as well as double-hit tests. These experimental studies demonstrate the capabilities of laser ultrasonics in the identification of both normal and abnormal grain growth, non-recrystallization temperature, recrystallization, and austenite decomposition kinetics in a single test for a given processing path, as well as its potential for accelerated optimization of process control under industrial rolling conditions.

Formulation of a Mechanical Stress Dependent Macroscopic Magnetic Model for Incremental Permeability Simulation

Electromagnetic based systems receive ever-growing interest for on-line assessment of steel strip properties for major manufacturers, especially when Advanced High Strength Steel (AHSS) products for automotive purposes are considered. Manufacturing AHSS need optimal control of the thermo-mechanical processing using in-line sensors for real time monitoring. IMPOC, 3MA and PropertyMon are some of the well-known electromagnetic sensors. Identification of a mechanical or metallurgical state from a magnetic signal is of great interest, requiring however sophisticated models to mimic the real behaviour and its sensitivity to many influencing parameters. Our paper presents a proposition to add the dependency of mechanical stress to the Jiles-Atherton hysteresis model. Experimental data consist of B(H) curves of carbon steels strips subjected to different levels of mechanical stress applied along the magnetic measurement direction. The JilesAtherton model has then been used to find out a set of stress-dependent coefficients. The variation of coefficients with stress is in close relationship with the variations of coercive field, remanent induction and permeability with stress. A coupled magneto-mechanical approach allows physics-based functions to be proposed to describe the evolution of JilesAtherton coefficients with stress. In this paper, experimental working conditions will be described, as well as the stressdependent Jiles-Atherton model. The model is finally implemented in FEM software, allowing more complex magneto-mechanical situations to be modelled. After matching with measurement, the new model is applied on 3MA modelling where magnetic transient analysis and magnetic AC steady state analysis are linked through incremental permeability.

How the EU project “Online Microstructure Analytics” advances inline sensing of microstructure during steel manufacturing

Weight savings in mobility and transport are mandatory in order to reduce CO 2 emissions and energy consumption. The steel industry offers weight saving solutions by a growing portfolio of Advanced High Strength Steel (AHSS) products. AHSS owe their strength to their largely refined and complex microstructures, containing multiple metallurgical phases. Optimal control of the thermo-mechanical processing of AHSS requires inline sensors for real-time monitoring of evolution and consistency of microstructure and material properties. To coordinate and accelerate European development activities in this domain, the project ”Online Microstructure Analytics (OMA)” was established in 2019, constituting of a consortium of 14 specialised research organisations. The EU-funded OMA project, with a total budget exceeding 6 MEU, focuses on inline sensing techniques to monitor the consistency and homogeneity of microstructure, texture and mechanical properties for automotive steels and in particular for AHSS.

Evaluating the Role of Technology Adoption in Enhancing the Growth and Performance of Sail Post-Reform

With the help of modernisation and digitalisation, SAIL has been making efficient use of its resources to maintain sustainability in the domestic as well as global market. The technological reformations taken up by the higher authority with the financial support of the government plays an eminent role in maintaining the sustainability of the organisation. This study critically focuses on the secondary quantitative data collection and statistical analysis to show the performance and growth of the SAIL. This study aims to deliver the information about the SAIL performance after expansion opportunity in the country by the support of government and dents the technology integration importance for developing the potential of competitiveness in the market. Moreover, it explores the knowledge about the safety practice through adoption of technology in the steel plant that helps their employees to get information about safety guidelines and also provides information technology roles that help administration to make decisions. It explores the information about the technology support to enable the high strength steel production.

Production of a Non-Stoichiometric Nb-Ti HSLA Steel by Thermomechanical Processing on a Steckel Mill

Obtaining high levels of mechanical properties in steels is directly linked to the use of special mechanical forming processes and the addition of alloying elements during their manufacture. This work presents a study of a hot-rolled steel strip produced to achieve a yield strength above 600 MPa, using a niobium microalloyed HSLA steel with non-stoichiometric titanium (titanium/nitrogen ratio above 3.42), and rolled on a Steckel mill. A major challenge imposed by rolling on a Steckel mill is that the process is reversible, resulting in long interpass times, which facilitates recrystallization and grain growth kinetics. Rolling parameters whose aim was to obtain the maximum degree of microstructural refinement were determined by considering microstructural evolution simulations performed in MicroSim-SM® software and studying the alloy through physical simulations to obtain critical temperatures and determine the CCT diagram. Four ranges of coiling temperatures (525–550 °C/550–600 °C/600–650 ° C/650–700 °C) were applied to evaluate their impact on microstructure, precipitation hardening, and mechanical properties, with the results showing a very refined microstructure, with the highest yield strength observed at coiling temperatures of 600–650 °C. This scenario is explained by the maximum precipitation of titanium carbide observed at this temperature, leading to a greater contribution of precipitation hardening provided by the presence of a large volume of small-sized precipitates. This paper shows that the combination of optimized industrial parameters based on metallurgical mechanisms and advanced modeling techniques opens up new possibilities for a robust production of high-strength steels using a Steckel mill. The microstructural base for a stable production of high-strength hot-rolled products relies on a consistent grain size refinement provided mainly by the effect of Nb together with appropriate rolling parameters, and the fine precipitation of TiC during cooling provides the additional increase to reach the requested yield strength values.

Research on Roll Shape Design for Quarter Wave Control of High-Strength Steel

Quarter wave defects often occur in high-strength steel production in wide rolling mills, which seriously affect product quality and production stability. The existing shape control actuators, such as roll bending, roll shifting, and CVC roll shape, can not adjust the high-order wave, and the upgraded CVCplus roll shape also has limited effects on the quarter wave. Therefore, the MVCplus roll shape is developed based on the superposition principle in order to realize the local roll shape modification at the wave position. Two cosine curves are superposed on the CVC roll shape within the strip width to decrease the reduction at the quarter of the strip width, and maximum reduction is achieved at the position of maximum wave height. The new roll shape can significantly reduce the quarter wave defects in practical application, and has little effect on the adjustment characteristics of the original CVC roll shape.

Microstructures and Properties Investigation on DP980 Dual-Phase Steel CMT + P Welded Joints.

The increasing demand for the lightweight production of advanced high-strength steel puts forward higher requirements for the quality of welded joint forming. The common CMT welding process has certain limitations and is difficult to meet the needs of lightweight manufacturing. In this study, the CMT + P welding technology was used to weld the DP980 dual-phase steel plate with 1.2 mm thickness. The ER120S-G welding wire was used as the filling material to conduct a 70° angle lap welding experiment. The effects of wire feeding speed (3 m/min~5 m/min) and welding speed (350 mm/min~600 mm/min) on the forming, microstructures, and mechanical properties of DP980 dual-phase steel welded joints were analyzed. The results show that the CMT + P welding process can produce lap weldments with good formability and properties. The welded joints can be divided into the weld zone, the HAZ, and the base metal zone, where the HAZ can be divided into the coarse-grained zone and the softened zone. The role of the elements Ni and Si is to promote the production of martensite and to increase the ferrite strength in welded joints. As the wire feeding speed increases, the grain size of the coarse grain zone in the HAZ increases from 31.90 μm to 50.93 μm; while the welding speed increases, the grain size of the coarse grain zone decreases from 45.48 μm to 35.73 μm. The average microhardness of the weld zone is 420 HV. In contrast, the average microhardness of the softening zone in HAZ is reduced to 250 HV. When the wire feeding speed is 4 m/min and the welding speed is 550 mm/min, the tensile properties of the weldment are optimal, its tensile strength can reach 973 MPa, and the tensile fracture is ductile fracture.

Bayesian approach to pyrometry during intercritical annealing of advanced high strength steel

Precise thermal control during intercritical annealing is essential to the production of advanced high strength steels (AHSS). Measuring the temperature of the steel strip through pyrometry requires detailed knowledge of the spectral emissivity of the steel strip, which is imperfectly known since it varies with wavelength, direction, temperature, surface roughness, and oxidation, the latter depending on alloy composition and processing conditions. This study presents a Bayesian pyrometry methodology in which temperature and spectral emissivity are described as unknown stochastic variables that are inferred simultaneously. Additional information about the spectral emissivity obtained through ex situ characterization are incorporated into the inference through maximum likelihood priors. While standard pyrometry methods provide a point estimate of surface temperature, the Bayesian framework infers the posterior probability density, which will allow galvanizers to better assess the reliability of the pyrometrically-inferred temperature.

Creation of an Effective Technology for the Production of Cold-Rolled High-Strength Low-Alloy Steels with High and Stable Properties. Part 2. Cold-rolled Products

Creation of an Effective Technology for the Production of Cold-Rolled High-Strength Low-Alloy Steels with High and Stable Properties. Part 2. Cold-rolled Products

Creation of an Effective Technology for the Production of Cold-Rolled High-Strength Low-Alloy Steels with High and Stable Properties. Part 1. Hot-rolled Products

Creation of an Effective Technology for the Production of Cold-Rolled High-Strength Low-Alloy Steels with High and Stable Properties. Part 1. Hot-rolled Products

Influence of high-speed sintering on the structure and properties of powder steels

As the technology of sintering steels is carried out at different temperatures and conditions, the for-mation of their structure and properties are somewhat different. Proper sintering technology allows the pro-duction of highdensity and high-strength powder steels. In most cases, the reason for the decrease in the pro-perties of powder steels is that the diffusion process, which occurs as a result of low sintering temperatures and low sintering times, is weak or non-existent. As we know, density and many physical and mechanical properties of the product increase as the pores close by dif-fusion during sintering. Proper welding technolo-gy allows the production of high-density and high-strength powder steels. Keywords: sintering; technology; powder; steel; structure; properties; oil; gas; industry.

Investigation of Microstructure and Mechanical Properties of Newly Developed Advanced High Strength TRIP Steel

In this research, the heat treatment and production of high-strength advanced TRIP1100 steel were investigated and then the mechanical properties of the welds of this steel were evaluated by spot welding. For this purpose, the effect of rolling process and heat treatment of alloy steel sheets to achieve the ultra-high strength TRIP1100 steel microstructure was discussed. Microstructural examinations by Scanning Electron Microscopy (SEM) identified ferrite with bainite phases and martensite in matrix. The microstructural characteristics were examined using SEM microscopy with Electron Backscatter Diffraction (EBSD) analysis. The EBSD results showed that the type and orientation of the grains changed and the fraction of high-angle to low-angle boundaries in the present steel varied due to the presence of different phases. The EBSD results showed the acceptable rate of primary austenite in the structure according to the phaseology of this method. Having desirable mechanical properties was one of the most important results of this study, which at the same time maintained impact resistance and mechanical strength.

Behavior of synchronous reduction and nitridation of iron/vanadium oxides with NH3–H2 mixtures

Ferrovanadium nitride, which comprises V and N, is an important alloy additive for the production of high-strength low-alloy steel. As an efficient reducing agent and nitrogen source, ammonia gas is widely used in the preparation of metal nitrides. In this study, ferrovanadium nitride alloy powder is prepared by reducing and nitriding VO2/Fe2O3 in NH3–H2 gas mixtures with different nitriding potentials. Thermodynamic analysis indicate that the reduction and nitridation of VO2 and Fe2O3 is feasible. VO2 is converted into VN, whereas Fe and Fe4N can be formed depend on the reaction conditions. Lower temperatures and higher nitriding potentials are beneficial to the formation of Fe4N. Based on Rietveld refinement analysis, the formation of Fe4N and the atomic occupancy of V and N in vanadium oxynitride, which is associated with the temperature, reaction time, and nitriding potential, is determined. A ferrovanadium nitride alloy powder with an O content of 0.26 wt.% is prepared by reducing and nitriding VO2/Fe2O3 at 900 °C for 1 h at a nitriding potential of 4.4 × 10−3 Pa−0.5.

Evolution behaviour of inclusions via oxide metallurgy of NM450 ultrahigh-strength steel

NM450 (450 HBW-grade, low-alloy, wear-resistant steel) is an ultrahigh-strength steel, in most cases, the inclusions in NM450 have a negative effect on its toughness, strength, and weldability. However, the detrimental effect of inclusions can be reduced by inclusion modification. In this study, the effect of oxide metallurgy on the evolution of inclusions in NM450 ultrahigh-strength steel was investigated, and it was found that as the O content increased in the steel before treatment, the Ti content in the formed inclusions increased. By extending the deoxidation time after adding Ti, the ratio of inclusions smaller than 10 μm in the steel increased, whereas that of larger inclusions gradually decreased. In the Ti–Ce and Ti–Ca composite deoxidation, the former had a higher and more stable yield, but the Ca treatment was more conducive to the nucleation of sulphides, thus reflecting the oxide metallurgical effect. The addition of Ce was prone to adhesion to the crucible wall, which may have an adverse effect on actual production. This work provides a theoretical reference for broadening the scope of application of high-strength steel products, improving product quality.

Formation of carbonitrides and precipitation of alloying elements during thermomechanical treatment of high-strength low-alloy steels. Atomistic modeling

Understanding the processes that control the formation of precipitates of alloying element, their composition and morphology is important for the choosing of optimal regimes of thermomechanical treatment, providing the required structural state and properties of low-alloyed steels. The use of modern methods of atomistic modeling and ab initio calculations to study the mechanisms and conditions of precipitation depending on the steel composition and temperature is discussed. The enthalpy of formation of Ti, V, Nb carbides and nitrides in γ-Fe was calculated using the methods of the theory of the electron density functional and the temperatures of their dissolution were determined in dependence on the composition of the steel. The results obtained agree with the experimental data and obtained by the CALPHAD method. Calculations of the electronic structure, enthalpy of mixing, energy of effective interactions between atoms of alloying and impurity elements have been performed. It was shown that an essential factor determining the nature of the interaction between alloying elements was the magnetic state of iron. It has been established that the enthalpy of mixing, which expresses the tendency of the system to decomposition, increases with the transition of α-Fe from the ferromagnetic to the paramagnetic state. In ferromagnetic α-Fe energetically, the formation of precipitates of Cu, as well as particles of a mixed composition of Cu‒Al, Cu‒Ni and an ordered phase of NiAl are preferable. It has been shown that precipitates Cu-based can be formed during technological times. The transition of α-Fe to the paramagnetic state results in increase of interactions between alloying elements (the exception is the interaction of Cu‒Cu and Cu‒Ni). As a result, additional combinations of alloying elements appear, the interaction between which lead to the formation of precipitates. At the same time, in γ-Fe, precipitates can be formed only based on Mo and Nb. The role of magnetism in the formation of precipitates and their influence on the γ→α-transformation is discussed. It has been shown that the results obtained make a base for enhancement technologies of high-strength low-alloyed steel production.

Investigation into the dephosphorization of ferromanganese alloys for the production of advanced high-strength steel

Advanced high-strength steels (AHSS) are sophisticated materials being developed by the steel industry to mitigate challenges related to the performance of motor vehicles. To meet the requirements of AHSS, the ferromanganese alloys (FeMn) utilized in the production of the steel are required to contain acceptable levels of unwanted impurities, i.e. P, S, N, H, and C. The focus of the current study was to investigate dephosphorization of ferromanganese to produce a low-P alloy that could be effectively utilized in the production of AHSS. The study involved conducting laboratory-scale testwork to study the efficiency of CaO-based slag systems to dephosphorize FeMn alloys. The addition of Na2O, CaF2, and BaO to MnO-CaO-SiO2 slag was considered. The test work was carried out in a 25 kW induction furnace at temperatures of 1350°C, 1400°C, and 1450°C. The P partition coefficient (Lp) remained small at <1, which is an indication that dephosphorization had not been achieved. The baseline slag, comprising 40%CaO-40%SiO2-20%MnO, reported higher Lpvalues. Addition of Na2O and CaF2 did not show any further benefit. Substituting half of the CaO by BaO, resulted in similar Lpvalues to those of the baseline slag under conditions of 1350°C and 1450°C at 30 minutes. In summary, based on the Lpvalues obtained, the conditions investigated with the CaO-based slags appeared to have been unfavourable for dephosphorization of FeMn alloys, as most of this impurity element remained in the alloy.

Experimental Investigation of Suitable Cutting Conditions of Dry Drilling into High-Strength Structural Steel.

Dry machining is one of the main ways to reduce the environmental burden of the machining process and reduce the negative effect of the cutting fluid and aerosols on operators. In addition, dry machining can reduce overall machining costs and, in the case of large workpieces, reduce the extra work associated with removing residual cutting fluid from the workpiece and adjacent area. For high-strength structural steel products, it is typical to drill holes with larger diameters of around 20 mm. Therefore, this work is devoted to the investigation of the dry drilling process carried out on a workpiece made of S960QL steel with a helical drill with a diameter of 21 mm. The aim was to find suitable cutting conditions for dry drilling with regard to process stability and workpiece quality. An experiment performed with a coolant served as a comparison base. A dry drilling experiment was performed with cutting speeds from 30 to 70 m·min−1 and feeds from 0.1 to 0.3 mm·rev−1, and with the results of this experiment, the same experiment with flood cooling was performed. During the drilling process, spindle torque values were recorded using the indirect spindle current recording method. The macroscopic chip morphology was studied to understand the cutting process. The chip thickness ratio was measured, as well as the maximum diameter of spiral chips. On the final workpiece, the qualitative and dimensional parameters of the holes were evaluated, such as the diameter, cylindricity and surface roughness, depending on the change in the cutting conditions and cutting environment. Evaluation of the obtained data led to the following conclusions. When drilling the S960QL material, there is only a very small increase in the drilling torque during dry drilling compared to drilling with cutting fluid. The increase in friction demonstrated by the chip thickness coefficient is significant. The influence of the environment on the dimensional accuracy showed a tendency for a slight increase in the holes’ diameters during dry machining. In comparison, the cylindricity of the dry-drilled holes shows a lower deviation than the holes drilled with cutting fluid. The surface roughness of the holes after dry drilling is affected by the increased friction of the outgoing chips, despite the resulting parameters being very good due to the drilling technology standards. This work provides a comprehensive view of the dry drilling process under defined conditions, and the results represent suitable cutting conditions to achieve a stable cutting process and a suitable quality of drilled holes.

Towards Bioleaching of a Vanadium Containing Magnetite for Metal Recovery.

Vanadium – a transition metal – is found in the ferrous-ferric mineral, magnetite. Vanadium has many industrial applications, such as in the production of high-strength low-alloy steels, and its increasing global industrial consumption requires new primary sources. Bioleaching is a biotechnological process for microbially catalyzed dissolution of minerals and wastes for metal recovery such as biogenic organic acid dissolution of bauxite residues. In this study, 16S rRNA gene amplicon sequencing was used to identify microorganisms in Nordic mining environments influenced by vanadium containing sources. These data identified gene sequences that aligned to the Gluconobacter genus that produce gluconic acid. Several strategies for magnetite dissolution were tested including oxidative and reductive bioleaching by acidophilic microbes along with dissimilatory reduction by Shewanella spp. that did not yield significant metal release. In addition, abiotic dissolution of the magnetite was tested with gluconic and oxalic acids, and yielded 3.99 and 81.31% iron release as a proxy for vanadium release, respectively. As a proof of principle, leaching via gluconic acid production by Gluconobacter oxydans resulted in a maximum yield of 9.8% of the available iron and 3.3% of the vanadium. Addition of an increased concentration of glucose as electron donor for gluconic acid production alone, or in combination with calcium carbonate to buffer the pH, increased the rate of iron dissolution and final vanadium recoveries. These data suggest a strategy of biogenic organic acid mediated vanadium recovery from magnetite and point the way to testing additional microbial species to optimize the recovery.