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Recrystallization kinetics and two critical temperatures—the non-recrystallization temperature TNR and the static recrystallization critical temperature TSRCT—of five Nb, Ti, and V microalloyed steel grades are evaluated. The experimental examination is realized by employing isothermal double-hit compression tests and continuous hot torsion tests, both performed on a Gleeble® 3800 thermo-mechanical simulator. The experimental results are used for the critical assessment of predicted TNR using four empirical equations from the literature, and for the validation of simulated TNR and TSRCT. The thermokinetic computer simulations are realized using the mean-field microstructure modeling software MatCalc. Analysis shows that higher microalloying contents increase both critical temperatures, TNR and TSRCT, whereby the effect of recrystallization retardation of Nb is more pronounced than that of Ti or V. The most accurate reproduction of the experimental recrystallization behavior of the five examined steel grades is realized by the employed physics-based simulation approach. [ABSTRACT FROM AUTHOR]

The influence of short‐time heat treatment on the widely used and commercially available ledeburitic cold‐work tool steel 1.2379 (X153CrMoV12; AISI D2) is examined herein. Starting from a soft annealed initial condition, the influence of different austenitizing temperatures and holding times on the metastable microstructural states after heat treatment/hardening is investigated. The experimental implementation of the heat treatment is used in a quenching dilatometer, and a microstructural simulation model is built using these results. As validation of the model, on the one hand, the martensite start temperature (Ms) is used, measured experimentally by dilatometry. Additionally, the carbide content and distribution, as determined by quantitative image analysis, are compared with the simulated data and used as an indicator of the model accuracy. Through the developed simulation model, arbitrary heat treatment‐induced metastable microstructural states can be calculated. As a possible application of this model, the live‐adaption of the industrial heat treatment process in dependence on the batch chemical composition is discussed. [ABSTRACT FROM AUTHOR]

AISI H13 cladding is deposited on the copper–beryllium (CuBe) alloy substrate by direct laser metal deposition via a buffer layer strategy. The SS316L austenite stainless steel is used as the buffer material attempting to reduce the risk of cracking. Single‐ and multi‐layer samples are deposited, including single‐layer SS316L, 1‐layer SS316L + 1‐layer H13, 2‐layers SS316L + 1‐layer H13, and 1‐layer SS316L + 4‐layers H13. The defect‐free single‐layer SS316L cladding is successfully deposited after the parameter pre‐optimization. Two types of defects including porosity and cracking are observed in all multi‐layer systems. The cladding microhardness of the 2‐layer system is rather low (400HV). A 50% increase in the cladding microhardness is observed when depositing on the five‐layer system. The five‐layer system shows a better load‐bearing capability (LBC) compared with the CuBe substrate in the low loading range. As load increases above 10 kN, the five‐layer cladding system shows the worse LBC compared to CuBe due to the low strength of the heat‐affected zone. A 2.7% cladding to substrate thickness ratio allows keeping more than 80% of the original thermal conductivity of the CuBe substrate. [ABSTRACT FROM AUTHOR]

Laser additive manufacturing (LAM) techniques, such as laser‐powder bed fusion (L‐PBF) or laser‐directed energy deposition (L‐DED), allow for the production of complex‐shaped parts by either the local melting of a metallic powder bed by a laser beam (L‐PBF) or a local application and laser beam melting of powder material by a nozzle (L‐DED). In the case of carbon‐martensitic tool steels, their cold crack susceptibility limits their LAM processability and is usually counteracted by substrate preheating. As preheating can increase the oxygen take‐up of the powder and alter the part microstructure, it can be disadvantageous for part quality and powder reusability. In this study, it is investigated a carbon‐martensitic steel designed for the production of parts with low crack density by LAM without preheating, focusing on the microstructure and hardness of the L‐PBF‐ and L‐DED‐manufactured steel. The steel can be LAM‐processed without preheating, resulting in specimens with low crack densities and martensitic microstructure with retained austenite. The hardness of the as‐built material (L‐PBF: 542HV30 and L‐DED: 623HV30) is increased by quenching and tempering up to 693HV30. Direct tempering of the as‐built specimen without previous quenching leads to a shift of the secondary hardness maximum from 500 to 530 °C. [ABSTRACT FROM AUTHOR]

Usually, tool steels are used in quenched and tempered conditions. Due to the phase transition from austenite to martensite and the volume change during the transformation, controlling distortion might be challenging. A newly developed steel focusing on a bainitic structure, even for bigger dimensions, shows a lower hardness at ambient temperature than conventional hot working tool steels but with a lower temperature dependency. Therefore, at service temperature, the mechanical properties are comparable to established grades. Heat treatment is simplified by a simple austenitization and cooling process without special requirements on the cooling rate. Due to a generally lower cooling rate and lower hardness compared to a quench and tempering process, the risk of cracking is reduced while machinability is improved. With the combination of good weldability and rather low hardness after rapid cooling, this grade can also be processed in additive manufacturing and is well suited for a hybrid process of conventional and additive manufacturing. [ABSTRACT FROM AUTHOR]

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The accurate identification of non-metallic inclusions (NMIs) within steel matrices is critical for high-quality steel production. This study employs synchrotron radiation-based X-ray absorption photoemission electron microscopy (X-PEEM) to investigate NMIs in ultra-high-strength steels. Ca-L 2,3 -edge X-ray absorption spectra were acquired for six NMIs at both room temperature and 400 °C, allowing a comprehensive exploration of structural changes, chemical compositions, and phases. Complex X-PEEM images were analyzed using advanced chemometric techniques, including Principal Component Analysis (PCA), K-means clustering, Fuzzy-means clustering (FMC), and Multivariate Curve Resolution–Alternating Least Squares (MCR-ALS). These methods allowed for the segmentation of X-PEEM images into distinct compositional zones. K-means clustering effectively identified regions of interest (ROIs) within NMIs, while PCA facilitated the microstructure variances of NMIs. Additionally, K-means and FMC revealed detailed compositional variations at the nanoscale. MCR-ALS proved particularly useful in uncovering changes in NMIs after annealing. This study pioneers the integration of X-PEEM with advanced chemometric methodologies, providing qualitative and quantitative spectromicroscopic insights. It significantly enhances our understanding of NMIs formation and alteration processes in ultra-high-strength steels, contributing to the advancement of materials science and steel production optimization. Furthermore, the methodologies and findings presented here serve as a guide for analyzing similar data sets of steel samples, offering valuable insights for future research and industrial applications in steel engineering. [Display omitted] • Unraveling the Secrets of Steel: Chemometric Insights into Non-Metallic Inclusions Using Advanced X-PEEM. • Chemometric Exploration of NMIs in Ultra-High-Strength Steels: An X-PEEM Spectromicroscopic Approach. • From Synchrotron Radiation to Chemometric Excellence: Probing Non-Metallic Inclusions in Steel Matrices. • Breaking New Ground: X-PEEM and Chemometrics Uncover the Complexity of NMIs in Ultra-High-Strength Steels. • Innovative Chemometric Strategies Transforming X-PEEM Imaging for Enhanced Steel Material Analysis. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Multiple properties of steel were predicted by nonlinear programming-based model. • One model could predict multiple properties simultaneously. • The potential boundaries of three properties were calculated. Abstract Extracting the valuable information about the connections between the overall properties and the related factors from the industrial big data of materials is of significant interest to the materials engineering. At present, most data-driven approaches focus on building a relation model for a single property of the materials, where it may ignore the restrictive boundaries of other properties. In this paper, we propose a machine-learning-based method using nonlinear programming for multiple properties of the materials, and solve the problem by using the Interior Point Algorithm. The key idea is to take the mapping functions corresponding to the properties of the materials as the constraints of the nonlinear programming problem, thus it is capable of processing the restrictions of these properties. Moreover, with our method, the possible boundaries of these properties under certain conditions can be calculated. Experiments results on steel production data demonstrate the rationality and reliability of the proposed method. [ABSTRACT FROM AUTHOR]

Differential quenching of the whole one-piece wheel is shown to be more effective than quenching of only the contact surface at the wheel rim. Hybrid strengthening by differential bulk quenching and surface plasma hardening is very promising in increasing the crack resistance of steel. The martensitic structure of the treated layer in hybrid strengthening is very disperse, thanks to decrease in size of the initial austenite grain. In bulk-quenched components, surface plasma strengthening creates a composite working layer characterized by high wear and crack resistance, whereas the core is relatively soft and plastic. [ABSTRACT FROM AUTHOR]

This study presents a possibility to predict the connection between the cooling regime and the properties of steel. An important factor to enhance the properties of steel is the speed of the cooling regime. To be in accordance with the experimental results, this study considered a correlation between the speed of cooling for laminated steel with a low carbon content and other properties of steel. It is important to choose the optimal cooling regime because the steel was laminated at high temperature.

This study presents a possibility to predict the connection between the cooling regime and the properties of steel. An important factor to enhance the properties of steel is the speed of the cooling regime. To be in accordance with the experimental results, this study considered a correlation between the speed of cooling for laminated steel with a low carbon content and other properties of steel. It is important to choose the optimal cooling regime because the steel was laminated at high temperature. [ABSTRACT FROM AUTHOR]

Results of experimental investigations concerning a quantitative assessment of the influence of corrosion intensity in sheets applied to side surface of tanks for liquid fuels on values of mechanical properties of steel they have been made from, have been presented and analysed. Noticeable reduction of steel yield point as well as growth of its brittleness have been observed mainly in sheet zones with not uniform and pitting corrosion. The reason for such an occurrence is associated to impairment of cementite skeleton of steel, as well as to accumulation of micro‐damages and micro‐notches, both inside of material structure and on its surface, what resulted in local stress concentrations. Santrauka Pateikti ir aptarti eksperimentinių tyrimų, susijusių su lakštų, naudotų skystojo kuro talpyklų išoriniams paviršiams, rūdijimo intensyvumo poveikio į plieno, iš kurio jie buvo pagaminti, mechaninių savybių skaitiniu įvertinimu, rezultatai. Vertas dėmesio plieno takumo ribos sumažėjimas, taip pat jo trapumo padidėjimas, buvo pastebėti lakštų srityse, pakenktose tolygiojo ir taškinio rūdijimo. Tokio atvejo priežastis siejama su plieno cementito griaučių gadinimu, taip pat su mikropažaidų ir mikrogriovelių sankaupa, abiems esant medžiagos sandaroje ir ant jos paviršiaus. Tai sukėlė vietinių įtempių santalką. First Published Online: 14 Oct 2010 Reikšminiai žodžiai: rūdijimas, plieninės skysčių talpyklos, plieno savybės, tempiamasis stipris, smūginė laikomoji galia, trapumas, mikrogrioveliai.

Results of experimental investigations concerning a quantitative assessment of the influence of corrosion intensity in sheets applied to side surface of tanks for liquid fuels on values of mechanical properties of steel they have been made from, have been presented and analysed. Noticeable reduction of steel yield point as well as growth of its brittleness have been observed mainly in sheet zones with not uniform and pitting corrosion. The reason for such an occurrence is associated to impairment of cementite skeleton of steel, as well as to accumulation of micro-damages and micro-notches, both inside of material structure and on its surface, what resulted in local stress concentrations. [ABSTRACT FROM AUTHOR]

Effects of such thermochemical processes as carburising, nitriding and boriding on properties of maraging steel grades have been investigated. Despite certain improvements in the properties of the obtained surface, at present, carburising and boriding cannot be recommended owing to problems in the layer quality and difficulties in dimension control processes. Nitriding has proved to be the most suitable process and subsequent surfacing with a TiN layer on the previously nitrided substratum of maraging steel provided additional improvement in properties. [ABSTRACT FROM AUTHOR]

The algorithm and computer program are completed to simulate the quenching of complex cylinders, cones, spheres, etc. Numerical simulation of steel quenching is a complex problem, dealing with estimation of microstructure and hardness distribution, and also dealing with evaluation of residual stresses and distortions after quenching. The nonlinear finite volume method has been used in numerical simulation. By the established computer program, mechanical properties and residual stresses and strains distributions in the quenched specimen can be given at every moment of quenching. [ABSTRACT FROM AUTHOR]

The effect of chromium additions to an Fe-14Co-10Ni-0.1Mo-0.16C (AF1410 based) secondary hardening steel was evaluated by mechanical and physical properties and by microstructural examination. This unique behavior was extended to encompass a large range of aging temperatures and times that may be encountered during commercial thermal treatment and/or welding. In the aging range of 482 to 550 °C, an increase in chromium from 2 to 3% in the AF1410 based steel resulted in a substantial strength decrease concomitant with an increase in toughness. This behavior is related to a peak hardening shift, early M2C carbide coarsening, and an increase in reverted austenite for the 1 wt% Cr increase. The increased aging kinetics resulting from the 3Cr steel caused a faster dissolution of Fe3C and rapid changes in chromium partitioning in the (Mo,Cr)2C carbide resulting in a coherency loss with a corresponding decrease in lattice parameter. The kinetics of the secondary hardening reaction, for the two steels, was determined by resistivity data for changes in aging parameters (time/temperature). [ABSTRACT FROM AUTHOR]

The effect of 1 % Cr addition on the resistivity during preaging and peak aging of an AF1410 based steel was examined by analytical and modeling approaches. The increased kinetics of aging resulting from a chromium addition, due to a variety of complex microstructural changes,was analyzed by Avrami-Mehl and Wert-Zener formulations, which were modified so that the exponent was a function of time. Using a eneralized Avrami equation, it was shown that the nucleation rate, N(t), at short aging times was large but became a rapidly declining function as N(t) approaches zero in a supersaturated system. A mathematical solution, using AF1410 steel carbide growth data at 510 °C, confirmed reported experimental evidence of second-stage carbide nucleation at 1 to 2 h. [ABSTRACT FROM AUTHOR]