Grain Size Of Steel Research Articles

Synergistic regulation of nano-precipitates and reversed austenite in titanium-free maraging steel by low-temperature solution treatment and double aging treatment

To synergistically enhance the strength and toughness of titanium-free maraging steel, a multi-scale characterization method was used to illustrate the effects of low-temperature solution treatment and double aging treatment on the microstructure of titanium-free maraging steel in this paper. After the low-temperature solution treatment and the double aging treatment, the tensile strength of titanium-free maraging steel increased from 1954 MPa to 2160 MPa and the elongation increased by 8.95 %. By the low-temperature solution treatment, the original austenite grain size of the titanium-free maraging steel was refined to 0.69 μm. The double aging treatment promoted the diffusion of Mo and Ni elements, increased the volume fraction of ω phase, Ni3Mo nano-precipitation phase and reversed austenite, and refined the size of ω phase and Ni3Mo by 14.2 % and 7.9 %, respectively. The nanoparticles of titanium-free maraging steel mainly include the ω phase, Ni3Mo and Laves phase. The strengthening mechanism of nanoparticles was quantitatively evaluated from the shear mechanism and Orowan dislocation loop mechanism. The mechanism shows that the ω phase is the main contributor to the overall precipitation strengthening. Therefore, low-temperature solution treatment and double aging treatment provide a potential solution for achieving high strength and high toughness in maraging steel.

Вплив хімічного складу та температури гартування на розмір зерна аустеніту та твердість інструментальної сталі

Alloying elements and impurities influence ambiguously on the factors that determine the process of the austenite structure formation. This does not make it possible to qualitatively predict the direction of their influence on the change of austenite grain dispersion during austenitizing heating and the hardness of tool steel. To date, there is no information on mathematical models that reliably describe the influence of chemical composition and quenching temperature on the specified characteristics of tool steels. The influence of the chemical composition and quenching temperature on the austenite grain size and the hardness of tool steels was studied, with the development of mathematical models of such influence with the determination of the effectiveness of these factors. It was established that the size of the austenite grain and the hardness of the quenched tool steel are mainly determined by the nature and quantity of alloying elements, the degree of distortion of the crystal lattice and the quenching temperature. The main influence on the austenite grain size of tool steels is the quenching temperature and the quantity of carbon, molybdenum and tungsten in the steel. An increase in the heating temperature leads to growth, and the quantity of elements - to the dispersion of the austenite grain. According to the increase in the specific efficiency of the influence of 1% alloying element on the decreasing of the austenite grain size, they can be arranged in the following sequence: W, Mo, C, and the efficiency of their relative influence is, respectively, 1 : 1.4 : 6.7. The hardness of tool steel is mainly determined by the content of carbon, silicon, tungsten and molybdenum in the steel and the degree of distortion of the crystal lattice by them, as well as the quenching temperature. The evaluation of the effectiveness of the factors showed that the influence of carbon is 26%, tungsten – 22%, molybdenum – 20%, tempering temperature – 17% and silicon – 15%. The obtained regression equations can be used by scientists for further research and by practitioners in the selection of materials for making tools. Keywords: steel, chemical composition, temperature, quenching, grain, austenite, hardness

Correlation of austenite grain size with ε-/α′-martensitic transformation and mechanical properties in a high-manganese damping steel

One of the core studies on low stacking fault energy (SFE) high-manganese steel is to maintain excellent damping capacity while achieving high strength and toughness. The austenite grain size (AGS) in high-Mn steel affects its SFE and even the strength-plasticity and damping capacity of the steel, but the detailed mechanism related to martensitic transformation has not been clarified. In this study, Fe-17Mn high-Mn damping steel is used as the material to obtain austenite grains of different sizes by controlling the cold rolling and annealing processes. By using in-situ tensile testing, damping capacity testing, and various microscopic analytical techniques, the influence of AGS on the thermal/deformation induced martensitic transformation, work hardening behavior, mechanical properties and damping capacity of the steel is mainly studied. The results indicate that the refinement of austenite grain increases the SFE of high-Mn damping steel and reduces the amount of thermal induced ε-martensite (εth) and stacking faults (SFs). The deformation induced martensitic transformations (DIMTs) in high-Mn damping steel during tensile deformation include γ→εD, εth→α′ and εD→α′ transformation. The deformation induced ε-martensitic transformation is more helpful to improve the work hardening rate than deformation induced α′-martensitic transformation. Due to the concentration of strain partitioning at grain boundaries, twin boundaries and phase boundaries, refinement of austenite grain can promote deformation induced ε-martensitic transformation and improve the steel strength. However, excessively small austenite grains can suppress deformation induced α′-martensitic transformation leading to a significant decrease in elongation. Under the synergetic effects of grain refinement strengthening and multiple martensitic transformations, when the average AGS is about 4.0 μm, the steel has high strength and high plasticity, with a tensile strength of 919 MPa, a yield strength of 518 MPa and an elongation of 46.4 %. The product of tensile strength and elongation is up to 42.6 GPa·%. At low or high strain amplitudes, the damping capacity of this steel shows an opposite trend with the refinement of AGS. The damping capacity of the steel gradually increases with grain refinement at low strain amplitudes of 0.01 %–0.065 %, mainly due to the reduction of the content of weak pinning points. At high strain amplitudes of 0.065 %–0.1 %, the damping capacity of the steel gradually decreases for the reduction of damping sources with the refinement of grain size.

A Study on the Effects of Cold Deformation on CMnSi Steel Structures Utilised in the Shipbuilding Industry

Abstract This article analyses the effects of deformation on the structure of CMnSi steel at various deformation levels. After hot forging, the structure of CMnSi steel comprises coarse-sized alpha and pearlite particles. The average grain size of steel after forging was 100 μm. After hot rolling, the grain size gradually decreases, with the average size of the ferrite and pearlite grains measured as 60 μm. After that, CMnSi steel was subjected to cold deformation at levels of 40%, 60%, and 80%. The grain size of the CMnSi steel sample after 80% cold deformation reached level 7, corresponding to about 25 μm. For a deformation level of 40%, the grain size was level 5, corresponding to 40 μm, while a deformation level of 60% produced a grain size of 35 μm, corresponding to level 6. In addition, scanning electron microscopy showed that after 80% deformation, smaller particles with a size of about 5 μm appear inside the parent particles. Moreover, energy-dispersive X-ray spectroscopy analysis revealed the carbide appearance in the form M23C6, with M being a mixture of Fe and Mn. These carbides have a fine size of about 1–2 μm and contribute to the prevention of particle growth during subsequent heat treatments.

Comparison of Young’s Modulus determination from Ultrasonic Testing and Three-Point Bending Testing

This study investigates the comparison of Young’s modulus value from ultrasonic testing and three-point bending testing. Five specimens from ABS material were created using FDM 3D printer with parameters of 200 μm layer thickness, solid print strength, and cross print pattern. Five specimens from stainless steel 316 were fabricated from conventional plate using waterjet cutting machine. Ultrasonic tests were done on each sample from ABS and stainless steel 316 by following ASTM A578. The three-point bending experiments of ABS and stainless steel 316 specimens were following ASTM D790, and ASTM E290, respectively. Ultrasonic testing and three-point bending testing were done on both materials to find the Young’s Modulus values. The results obtained from both experiments were compared to each other as well as to a standard value. The results show that Young’s modulus values from ultrasonic testing are more comparable to the standard value than that from three-point bending testing. These are due to build orientation of ABS, and grain size of stainless steel 316 which have some effect on Young’s Modulus values.

Identifying grain size in ASTM A36 steel using ultrasonic backscattered signals and machine learning

Ultrasonic nondestructive techniques can be useful tools in the microstructural classification of metallic alloys. Among the most common techniques for characterizing materials, backscattered signal analysis stands out because it does not require a back surface echo. This study classifies five ASTM A36 steel samples with varying grain sizes using ultrasonic waves. For each sample, ultrasound signals were obtained using two ultrasonic array probes with center frequencies of 5 and 10 MHz. An extensive feature engineering process was conducted using the tfresh package in Python, which extracts a wide range of features from time series data, transforming raw ultrasound signals into a structured format. Seven machine learning models were evaluated based on accuracy, precision, recall, and F1 score, with performances ranging from 70 to 100%. The XGBoost model exhibited the best performance with 10 MHz probe signals, achieving 100% accuracy. An additional validation test was conducted to evaluate the models’ generalization capability, considering inter-specimen variabilities. Despite a slight reduction in prediction metrics, the XGBoost model maintained good performance, with accuracy between 89% and 100% across all frequencies. Such findings demonstrate that backscattered grain noise can effectively identify grain sizes provided that an adequate machine learning model is used.

Microstructure, mechanical properties and wear resistances of 40CrNiMoA steel affected by cyclic quenching treatment

The microstructure evolution and mechanical properties of hot-rolled (HR) 40CrNiMoA steel affected cyclic quenching treatment were investigated in this work. The results reveal that the average austenite grain size of 40CrNiMoA steel is refined and more uniformly distributed after cyclic quenching. With first pass of cyclic quenching (CQ1), the austenite grain size of 40CrNiMoA steel reduces from 9.14 μm(HR) to 4.51 μm(CQ1). Concurrently, the ultimate tensile strength and hardness experience a notable increase from 1081 MPa to 2314 MPa and 362HV to 620HV, respectively. With the decrease of grain size, the ultimate tensile strength and hardness of the sample increased significantly, and the elongation remained basically unchanged. The wear resistance ranking of the samples, from strong to weak, is CQ1 > CQ2 > CQ0 > HR. The 40CrNiMoA steel undergoes a single pass of cyclic quenching treatment, and considering economic factors, its mechanical properties and wear resistances undergo significant enhancement, thereby exerting a substantial impact on its overall performance.

Effects of Initial Grain Orientation and Annealing Parameters on Grain Size, Texture, and Magnetic Properties of Ultra-Thin Grain-Oriented Silicon Steel

Effects of Initial Grain Orientation and Annealing Parameters on Grain Size, Texture, and Magnetic Properties of Ultra-Thin Grain-Oriented Silicon Steel

Microstructure Prediction of 80MnSi8-6 Steel After Hot Deformation Based on Dynamic Recrystallization Kinetics and FEM Simulation

The microstructure evolution during hot deformation of 80MnSi8-6 nanobainitic steel was investigated through hot compression tests at deformation temperatures of 900–1250°C and strain rates of 0.1–20 s−1. The flow curves revealed strain-hardening behavior at the beginning of deformation followed by softening effects caused by microstructure evolution. A Johnson–Mehl–Avrami–Kolmogorov (JMAK) model for grain growth and dynamic recrystallization was developed, and the kinetics were determined. Critical and peak strains were identified, and coefficients for the microstructure evolution models were determined using linear regression. The analysis of S-curves revealed that decreasing the temperature delays the onset of recrystallization and that the strain rate significantly effects the recrystallization rate at lower temperatures. Constitutive modeling and determination of the Zener–Hollomon parameter allowed the determination of the influence of hot processing conditions on material behavior during deformation. Microstructure analysis showed that, at higher deformation temperatures, grain growth occurs simultaneously with grain refinement. Coefficients for the JMAK model were implemented in QForm software. Simulation results were compared with experimental measurements exhibited good arrangement, which confirms the accuracy of the JMAK model in predicting the microstructure evolution. This study demonstrated how microstructure evolution modeling and FEM simulations combined can be used to predict the grain size of 80MnSi8-6 steel after hot deformation.

The durability increasing of high-wear cast parts of mining and processing equipment

The analysis of the operation of rapidly wearing parts of the ore-grinding equipment was carried out. It has been established that unloading grates and ladles are fast-wearing parts of layered fracture mills and determine their downtime between repairs. The possibility of improving the mechanical properties of medium-carbon steel 40HL due to the reduction of harmful impurities is shown. The effects of modification with aluminum, vanadium, calcium, and rare earth metals on structural formation, mechanical, and operational properties of steel are investigated. It was established that the complex modification of cast steel 40HL (0.04…0.1% vanadium, 0.15% silicon calcium and 0.15% rare earth metals) allows to significantly increase its mechanical properties and wear resistance. The separate and joint influence of aluminum, vanadium, calcium and rare metals on the austenite grain size and hardening of steel was studied. The proposed modification technology makes it possible to obtain a fine grain, through-hardening of castings and ensure reliable and long-lasting operation of ball mills.

Influence mechanism of solution temperature on microstructure evolution and tensile properties of Ti microalloyed high strength steel CGLC700

The influence mechanism of solution temperature on the strength and toughness of Ti microalloyed steel CGLC700 was studied. The microstructure changes of Ti microalloyed steel were observed by micro-electron microscopy, and the mechanical properties were evaluated by tensile test. The appropriate solution temperature can promote the solid solution of Ti atoms and the formation of small-sized TiN, TiC and other particles, hinder the movement of dislocations, and improve the tensile properties of steel. When the solution temperature is 1240 °C (2#), the grain size of steel is the lowest, the proportion of high angle grain boundary is the highest, and the tensile properties of steel are the best. Ti microalloyed steels increased tensile strength by 4.12%, yield strength by 2.85% and elongation by 28.4%. Too low or too high solid solution temperatures weaken the strengthening effect of the microalloying elements and led to a reduction in the tensile properties of the steel. This can be attributed to the low solid solution of Ti at low solid solution temperatures and the growth of second phase particles and inclusions at too high solid solution temperatures. This study provides a theoretical basis for optimizing the heat treatment process of Ti microalloyed steel.

Simultaneously Improving the Strength and Plasticity of Additively Manufactured 316L Stainless Steel by Adding Aluminum

Due to the special layer‐by‐layer printing process of additive manufacturing (AM), the heat dissipation in the printed material tends to flow mainly along the building direction, which results in the formation of coarse columnar grains in AM metals. The coarse grains are detrimental to the mechanical properties of AM metals, and are not conducive to the lightweight development of AM metal components. This article proposes a printing strategy for adding aluminum to 316L stainless steel. Based on the aluminum‐reinforced strategy, low melting point MnSiO3 particles are transformed into high melting point Al‐containing particles (such as Al2O3), and the grain size of 316L stainless steel produced by direct energy deposition (DED) is refined, resulting in a significant improvement of tensile strength. What is more, the increase in tensile strength of Al‐reinforced 316L does not sacrifice its plasticity. Attributed to the twinning‐induced plasticity effect and good adhesion between Al2O3 particles and matrix, the plasticity of Al‐reinforced 316L is synchronously improved. To be more specific, compared to DED‐316L without adding Al, the yield strength and tensile strength of samples with adding 0.5%wt Al are individually improved by 14.8% and 16.2%; at same time, the uniform elongation and total elongation are increased by 80.4% and 13%, respectively. The printing strategy proposed in this article is expected to provide reference for the strengthening and toughening of AM metals, thereby contributing to the lightweight development of AM components.

Review on the application of stainless-clad bimetallic steel in the marine environment

PurposeStainless-clad bimetallic steels (SCBS) are widely investigated in some extremely environmental applications areas, such as polar sailing area and tropical oil and gas platforms areas, because of their excellent anticorrosion performance and relatively lower production costs. However, the properties of SCBS, including the mechanical strength, weldability and the anticorrosion behavior, have a direct relation with the manufacturing process and can affect their practical applications. This paper aims to review the application and the properties requirements of SCBS in marine environments to promote the application of this new material in more fields.Design/methodology/approachIn this paper, the manufacturing process, welding and corrosion-resistant properties of SCBS were introduced systematically by reviewing the related literatures, and some results of the authors’ research group were also introduced briefly.FindingsDifferent preparation methods, such as rolling composite, casting rolling composite, explosive composite, laser cladding and plasma arc cladding, as well as the process parameters, including the vacuum degree, rolling temperature, rolling reduction ratio, volume ratios of liquid to solid, explosive ratio and the heat treatment, influenced a lot on the properties of the SCBS through changing the interface microstructures. Otherwise, the variations in rolling temperature, pass, reduction and the grain size of clad steel also brought the dissimilarities of the mechanical properties, microhardness, bonding strength and toughness. Another two new processes, clad teeming method and interlayer explosive welding, deserve more attention because of their excellent microstructure control ability. The superior corrosion resistance of SCBS can alleviate the corrosion problem in the marine environment and prolong the service life of the equipment, but the phenomenon of galvanic corrosion should be noted as much as possible. The high dilution rate, welding process specifications and heat treatment can weaken the intergranular corrosion resistance in the weld area.Originality/valueThis paper summarizes the application of SCBS in marine environments and provides an overview and reference for the research of stainless-clad bimetallic steel.

Study on Influence of Rare Earth Ce on Micro and Macro Properties of U75V Steel.

Non-metallic inclusions in steel have great influence on the continuity of the steel matrix and the mechanical properties of steel. The precipitation sequence of Ce inclusions in molten steel is predicted by thermodynamic calculations. The results show that Ce content will affect the precipitation sequence of rare earth inclusions in molten steel, and the formation of CeO2, Ce2O3 and CeAlO3 will be inhibited with the increase in Ce content. Our laboratory smelted the test steel without rare earth additive and the test steel with rare earth Ce additive (0.0008%, 0.0013%, 0.0032%, 0.0042%). It was found that the MnS inclusions and inclusions containing Al, Ca, Mg and Si oxides or sulfides in the steel after rare earth addition were modified into complex inclusions containing CeAlO3 and Ce2O2S. The size of inclusion in steel was reduced and the aspect ratio of inclusion was improved. The addition of Ce also improved the grain size of U75V steel and significantly refined the pearlite lamellar spacing. After mechanical property testing of the test steel, it was found that when Ce is increased within 0.0042%, the tensile and impact properties of U75V steel are also improved.

Assessment of the metal grain size of 12Cr1MoV steel by LIBS coupled with acoustic wave information

A modelling scheme that integrates spectral and acoustic data was put forth as a means of enhancing the precision of grain size detection in 12Cr1MoV steel.

Study on Austenite Grain Growth Behavior of GCr15 Bearing Steel

The effects of austenitizing temperature and holding time on the austenite grain growth behavior of GCr15 bearing steel are reflected in this paper. SEM and EBSD deeply reveal the effect of austenite grain size on the misorientation angle of grain boundary. The results show that both the holding time and the austenitizing temperature will make the austenite grain size grow to a certain extent. However, the change of temperature will cause a greater change in grain size. The grain size will also have different growth trends in different austenitizing temperature ranges. The grain size of Gcr15 test steel is combined with the Sellars model to derive its growth kinetics model.

Dependences of grain size of low-carbon corrosion-resistant 07Kh16N4B steel on degree of deformation in recrystallization temperature range

The recrystallization temperature of 1050 °C of corrosion-resistant 07Kh16N4B steel is determined. The dependences of the grain size on the degree of deformation up to 70 % at deformation temperatures of 1050, 1100, 1150 °C are constructed. The dependencies have the form of non-monotonic curves and are characterized by the presence of two abrupt increases in grain size. When constructing the dependence, it is taken into account that the maximum level of actual deformation at low degrees of total deformation is not in the center of the deposited sample, but at a certain height along the line between the center and the end face, the position of which is determined by mathematical modeling. The intervals of critical degrees of deformation are determined and recommendations are given on the degrees of compression depending on the deformation temperature.

Effect of N on hot deformation behavior of high-Mn austenitic steel

The present study dealt with the hot compression deformation behavior of Fe−18.5Mn–7Cr−0.6C and Fe−18.5Mn–7Cr−0.6C−0.21 N high-Mn austenitic steels within a temperature range of 900–1200 °C, a strain rate range of 0.01–5 s−1, and a true strain of 0.7. The accurate constitutive equations were established according to their flow curves, and the deformation microstructures were also analyzed. The results revealed that the dominant softening mechanism for the two test steels without substantial peak stress (higher Zenger-Holloman parameter values) could also be dynamic recrystallization (DRX) rather than dynamic recovery (DRV). The addition of N enhanced the strain rate sensitivity of high-Mn austenitic steel at low temperatures and high strain rates. Furthermore, the addition of N increased the high temperature strength and hot deformation activation energy (Q) of high-Mn austenitic steel. Moreover, the addition of N could also increase the DRX volume fraction and refine the DRX grain size of high-Mn austenitic steel.

Prediction of Surface Microstructure, Grain Size, Martensite Content, and Microhardness of 316L Austenitic Stainless Steel in Surface Mechanical Grinding Treatment Process

Prediction of Surface Microstructure, Grain Size, Martensite Content, and Microhardness of 316L Austenitic Stainless Steel in Surface Mechanical Grinding Treatment Process

Effect of zirconium and niobium on the microstructure and mechanical properties of high-strength low-alloy cast steels

The aim of this work is to study the effect of zirconium and niobium on the refinement of grain size and mechanical properties of micro-alloyed cast steels in heat treated conditions. Five micro-alloyed cast steels with different compositions, as steel without microalloying elements and micro-alloyed steel with (i) 0.05% Zirconium (Zr), (ii) 0.05% Zirconium (Zr) and 0.05% Niobium (Nb), (iii) 0.10% Zirconium (Zr), and (iv) 0.10% Zirconium (Zr) and 0.10% Niobium (Nb) were investigated. The heat treated samples are normalized at 1000 °C followed by air cooling and were characterized to study the characteristics of carbide precipitates by SEM and TEM and mechanical properties were evaluated by tensile test as per ASTM A370. Among these five cast steels, steel containing 0.10% Zr and 0.10% Nb showed a higher tensile strength of 1184 MPa and yield strength of 740 MPa with reasonable impact energy of 42 J compared to other steels under the same heat treated conditions. Due to the combined addition of Zr and Nb elements in the micro-alloyed steel, a remarkable improvement of mechanical properties particularly strength and impact energy was observed. As evident from microstructure investigation, these improved mechanical properties in the present steel could be attributed due to the effective refinement of ferritic grain size in the normalized condition.