CCT diagram Research Papers - Academia.edu (original) (raw)

2025, Acta Metallurgica Slovaca

The main objective of this article is to deep the knowledge of the thermal behavior of ferrite-bainite (FB) steel in correlation with the structural aspects that justify the mechanical properties. Samples of a DP-590 steel were tested by dilatometry considering a heating rate of 0.17 °C/s, up to a temperature of 1150 °C and different cooling rates between 0.03 °C/s to 100 °C/s, in air atmosphere. The results of the thermal behaviour were correlated with a microstructural study using optical microscopy in order to establish the final proportion of ferrite and bainite that is achieved at each cooling rate considered. As the cooling rate increases, the diffusion processes are limited so that hard second phases are obtained. In this steel, the presence of bainite was corroborated. The mechanical strength evolution associated with the cooling rate was determined through microhardness measurements. On this base, the steel's continuous CCT curves was built.

2025, Metalurgija

S. Rusz, T. Kubina, I. Schindler, B. Smetana, P. Kawulok, M. Cagala VŠB – Technical University of Ostrava, Faculty of Metallurgy and Materials Engineering, Czech Republic Various physical methods for the determination of phase transformation temperatures were compared using C-Mn and C-Mn-V-Nb steels. The measurement using temperature scanner, variously located thermocouples, dilatometer, diff erent thermal analysis (DTA) and anisothermal plastometric test were completed. The specimens were heated to 1 323 K and 1 473 K in the case of the C-Mn-V-Nb microalloyed steel. The aim of the diff erent heat treatment were to obtain diff erent levels of precipitates’ dissolution. It was found that the better particles’ distribution and precipitation due to the cooling lead to the enlargement of the two-phase region in the material. The good agreement of result gained by used methods was achieved. We found that all used methods can be used for common steels, but the temperature scanner seems no...

2024, Metalurgija

2024

Purpose-The purpose of this paper is to present results of an evaluation of dual-phase and galvanized steel reinforcements in corrosive environments. Design/methodology/approach-Low carbon steels were intercritically annealed at 7408C followed by water quenching to obtain dual-phase structures with 37 per cent volume fraction of martensite dispersed in ferrite matrix. Dual-phase and galvanized steel rebars were embedded in concrete cubes and immersed in 5 per cent NaCl solution for up to 100 days. Corrosion rate, tensile and macro as well as microhardness tests were performed. The dual-phase and galvanized zinc layers were observed under scanning electron microscopy (SEM). Findings-From all of the tests carried out it was found that dual-phase steels exhibited better corrosion resistant properties and superior strength compared to galvanized steels. Originality/value-The results reported show that dual-phase steel can be a good candidate for reinforcement in concrete especially in aggressive and corrosive environments.

2024, MATEC web of conferences

The prediction of hardness distribution in the cross section of welded join made of S1100QL steel is performed in this study on the basis of analytical methods. Analytical CCT diagram and volume fraction of each phases of S1100QL steel as a function of cooling time t 8/5 are determined. A numerical simulation of welding process is performed in ABAQUS. Thermal cycles and temperature field in welded joints are determined. Prediction of hardness distribution in the cross section of the joint is performed on the basis of obtained cooling times t 8/5. Results of numerical simulations are compared with experimentally obtained results.

2024

Dual phase steel is an advanced high strength steel that has a ferrite and martensitic microstructure which are used in various industrial applications, mostly in automotive industry, due to their excellent mechanical properties (high tensile strength, high formability, etc.). These properties depend on their microstructure which is obtained with production conditions and especially chemical composition. Annealing stage is very important section in order to compose final microstructure of dual phase steels. In addition to that chemical composition is an important consideration since alloying content usually designate limits of heat treatment. In this work, annealing treatment was simulated by GLEEBLE 3500 thermalmechanical simulator to determine effect of continuous annealing line and continuous galvanizing line (CAL & CGL) heat cycle characteristics on microstructure and mechanical properties of dual phase steels. Heat treated samples were characterized by using light optical micro...

2024

Proper heat treatment of steels is one of the most important factors in determining how they will perform in service. Engineering materials, mostly steel, are heat treated under controlled sequence of heating and cooling to alter their physical and mechanical properties to meet desired engineering applications. In this study we have chosen AISI 1020 steel as for our research work and we have tried to find out the mechanical properties (hardness) and micro structural properties by means of appropriate heat treatment process (annealing, normalizing & quenching). Here the steel specimens were heat treated in a furnace at different temperature levels and soaking time; and then cooled in various media (furnace, air, water, oil, and brine). After that the hardness of the specimens were rechecked for the comparison with previous data and the microstructures of the specimens were examined using metallurgical microscope equipped with camera. These results showed that the hardness of AISI 1020 steel can be changed and improved by different heat treatments for a particular application. From the microstructures we have found that the annealed specimens with mainly ferrite structure give the lowest hardness value and highest ductility while quenched specimens give the highest hardness value and lowest ductility. On the other hand, normalized specimens have given the moderate hardness and ductility comparing with hardened and annealed specimens.

2024, ISIJ International

Using the dilatometry technique, g→a transformation kinetics has been determined at different cooling rates in a steel with low carbon and low niobium contents (0.09 and 0.017 mass% respectively). First of all the real and the conventional transformation temperatures of the steel were determined. The real start temperature for proeutectoid ferrite formation (AЈ r3) corresponds to the point where the dilatometric curve starts to diverge from the straight during cooling. The conventional start and finish temperatures for proeutectoid ferrite formation (A r3 and A r1) are given by two points close to the minimum and the first maximum of the curve, respectively. The real start and finish eutectoid transformation temperatures-(AЈ r1) s and (AЈ r1) f-correspond to the second point of inflection and a point close to the second relative maximum of the curve, respectively. Carbon enrichment of the remaining austenite, as the transformation to ferrite advances, is corrected taking into account the dependence on the carbon content of the atomic volume of austenite. On the other hand, the dilatometric data have also been corrected with regard to the different expansion coefficients of austenite and ferrite. In this way it has been seen that the lever-rule method applied to the dilatometric curve is useful for determining transformation temperatures, but not for determining transformation kinetics, since the amount of proeutectoid ferrite calculated with this method was up to 10 % greater than the real amount measured with an image analyser. Finally a model based on Avrami's law has been developed for the real g→a transformation kinetics.

2024, MRS Proceedings

ABSTRACTThis article outlines the use of quenching dilatometry in phase transformation kinetics research in steels under continuous cooling conditions. For this purpose, the phase transformation behavior of a hot-rolled heat treatable steel was investigated over the cooling rate range of 0.1 to 200 °C/s. The start and finish points of the austenite transformation were identified from the dilatometric curves and then the continuous cooling transformation (CCT) diagrams were constructed. The experimental CCT diagrams were verified by microstructural characterization using scanning electron microscopy (SEM) and Vickers micro-hardness. In general, results revealed that the quenching dilatometry technique is a powerful tool for the characterization and study of solid-solid phase transformations in steels. For cooling rates between 200 and 25 °C/s the final microstructure consists on plate-like martensite with the highest hardness values. By contrast, a mixture of phases of ferrite, baini...

2024, Metalurgija

A. Nagode, M. Bizjak, B. Kosec, B. Karpe, B. Zorc, Faculty of Natural Sciences and Engineering, University of Ljubljana, Ljubljana, Slovenia; A. Resnik, Štore Steel d.o.o., Štore, Slovenia; G. Kosec, Acroni do.o.o, Jesenice, Slovenija, I. Budak, Faculty of technical Sicences, University of Novi Sad, Novi Sad, Serbia In this paper the development of a banded microstructure in hot-rolled 34CrNiMo6 steel which consisted of bainitic and martensitic bands is explained. The chemical compositions of the bands were measured with energy dispersive x-ray spectroscopy (EDS), which showed that the martensitic bands contained more alloying elements (Mn, Cr, Mo, Si) than bainitic bands. By using Oberhoffer reagent, the segregations of phosphorus were also revealed. These phosphorus segregations coincided with the positive segregations of the alloying elements. The continuous cooling transformation (CCT) diagrams of steel were calculated. They confirmed the formation of martensite in positive segr...

2024, Metallography

This paper contains information on the high-temperature phase equilibria and transformation behavior of two commercial low-carbon silicon steels (1.4-I .5% Si) determined by dilatometry and metallography. Use of a picric acid etching reagent has enabled the distribution of the a and 3' phases to be determined on specimens cooled relatively quickly from high temperatures, and measurements of the quantity of y present by normal etching in nital are shown to be underestimates. The steels studied contain some y at temperatures from 760°C to at least 1200°C, with the amount increasing with decreasing silicon content and increasing temperature.

2024, Materials

The paper deals with the dilatometric study of high-alloy martensitic tool steel with the designation M398 (BÖHLER), which is produced by the powder metallurgy process. These materials are used to produce screws for injection molding machines in the plastic industry. Increasing the life cycle of these screws leads to significant economic savings. This contribution focuses on creating the CCT diagram of the investigated powder steel in the range of cooling rates from 100 to 0.01 °C/s. JMatPro® API v7.0 simulation software was used to compare the experimentally measured CCT diagram. The measured dilatation curves were confronted with a microstructural analysis, which was evaluated using a scanning electron microscope (SEM). The M398 material contains a large number of carbide particles that occur in the form of M7C3 and MC and are based on Cr and V. EDS analysis was used to evaluate the distribution of selected chemical elements. A comparison of the surface hardness of all samples in ...

2024, Journal of Alloys and Compounds

The intercritical annealing and isothermal bainitic processing response was studied for three Nb and V microalloyed Transformation-Induced Plasticity (TRIP)-assisted 980 MPa grade steels. Their mechanical and microstructural properties were compared to industrially produced TRIP 800 steel. Depending on the isothermal holding temperature and microalloying, the experimental steels reached properties comparable to the reference steel. The retained austenite content did not show direct correlation to elongation properties. Niobium was found to be more effective microalloying element than vanadium in increasing the elongation properties, which were investigated by measuring true fracture strain from tensile test specimens.

2024

Production of forgings contains complex and demanding processes that consist of a number of forging operations which can also include post-forge heat treatment. An optimized manufacturing line is a prerequisite for obtaining prime-quality products which in turn are essential for profitable operation of a forging company. Problems may, however, arise from modifications to the manufacturing route due to changing customer needs. To prevent the production line from being temporarily suspended for changeover and optimization. The use of material-technological modelling with the required modifications can be tested and optimized under laboratory conditions outside the plant without disrupting the production. Thanks to material-technological modelling, the process parameters can be well controlled and varied rapidly in response to changes in market requirements. Outcomes of the modelling runs include ideal parameters for the manufacturing process of the forging part and results of microstr...

2024

A mathematical model for calculating phase transformations in steels during rapid heating and cooling is presented. It is based on a rule of additivity. The isothermal kinetics are modelled by Johnson-Mehl-Avrami law. The model des6ribes the kinetics of austenitization during heating. the state of austenite at the end of heating (carbon content, grain size), the kinetics of transformations during cooling. the final microstructure and hardness. The model is worked out firstly on dilatometric specimenswithout thermal gradients in order to validate the modelling and the input data. Thenthe application of the model to massive cylinders heated up and cooled down with high thermal gradients is presented.

2024, Journal of achievements in materials and manufacturing engineering

Purpose: Refinement of austenitic steel and low alloyed C-Mn-Si-Nb steel microstructure by free-forging. Design/methodology/approach: In this study severe hot deformation was applied on low alloyed 0.2C-1.5Mn-2Si-0.05Nb steel and austenitic 0.07C-18Cr-2Mn.-10Ni steel. Steels were processed in a full-hydraulic press. Different temperatures of preheating, dwells and strain levels were applied. Microstructure was characterised using optical metallography, scanning and transmission electron microscopy. Findings: After optimization of processing fine grained structures with convenient phase composition were obtained. Multiple free-forging followed by recrystallization annealing was successfully used for refinement of austenitic Cr-Ni steel and improvement of mechanical properties. While free-forging of low alloyed C-Mn-Si-Nb steel still has not satisfied expected increase of strength and ductility. Research limitations/implications: Free-forging usually results in formation of very heterogeneous structures. In submitted study relatively fine grained and uniform structures were obtained. Grain size below a few micrometers can not be probably achieved using above mentioned technology. Originality/value: Obtained results can be used for development of forging technology in service conditions.

2024, Metallurgical Research & Technology

The paper demonstrates the capability of the developed phase transformation model to design the cooling conditions in the Stelmor process allowing for obtaining different types of microstructures in wire rod of 32CrB4 steel. The model based on modified JMAK equation was developed using the results of the tests conducted in a DIL 805 A/D/T dilatometer. The model is composed of sub-models of ferritic, pearlitic, bainitic and martensitic transformations. Its predictive capability was confirmed in industrial conditions by performing trials with different settings of fans involved in the cooling process on the Stelmor line of CMC Poland. Excellent performance of the model was achieved through the modification of commonly used equations which allows accurate predictions of the phase transformations start and finish temperatures, as well as volume fraction of microstructural constituents, in a wide range of cooling rates. It was demonstrated that the model can effectively be applied to des...

2024, Mechanics and Mechanical Engineering

Engineering materials, mostly steel, are heat treated under controlled sequence of heating and cooling to alter their physical and mechanical properties to meet desired engineering applications. This paper presents a study of the influence of austenitization temperature, cooling rate, holding time and heating rate during the heat treatment on microstructure and mechanical properties (tensile strength, yield strength, elongation and hardness) of the C45 steel. Specimens undergoing different heat treatment lead to various mechanical properties which were determined using standard methods. Microstructural evolution was investigated by scanning electron microscopy (SEM). The results revealed that microstructure and hardenability of the C45 steel depends on cooling rate, austenitization temperature, holding time and heating rate.

2024, Materials

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

2024

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

2024, Science & military

The article is a result of investigations which deals with the phase transformations of tool steel X155CrMoV12. The experimental data obtained was used to evaluate the resulting Continuous Cooling Transform (CCT) diagram, which consists of seven dilation curves. All experimental samples from dilatometric analyzes were then subjected to microstructural analyzes and hardness measurements to characterize the microstructure and hardness for each heat treatment mode tested. Atomic Force Microscopy (AFM) microscopy was also used to study the carbides present in steels and their size and shape for all selected cooling modes.

2023

It is known that the mechanical properties of steels are dependent on the final microstructure resulting from phase transformation during heat treatments. Hot rolled mine support profiles are produced generally from unalloyed quality steels. After the hot rolling, heat treatments of quenching and tempering result in a tempered martensite microstructure with high strength and toughness. The retained austenite phase may also be expected in the microstructure due to the lack of alloying elements. In this study a microstructural characterization of a mine support profile is carried out before and after the quenching and tempering to investigate the effect of heat treatments on the microstructure. A dilatometric analysis is performed to detect the phase transformation temperatures. Dilatometric analysis is carried out at different cooling rates from austenite phase region. Depending on the different cooling rates, ferrite, pearlite and bainite phases are determined using dilatation curves, light microscope, and Vickers hardness tests. The results indicate that critical temperatures can be determined by dilatometric analysis.

2023

In this study, the suitability for producing dual phase steel from hot rolled medium carbon steel for mining industry and the effect of annealing temperature on hardness and microstructure has been investigated. The critical equilibrium temperatures and phase diagram were calculated using Thermo-Calc software for 0.37C-0.87Mn steel. In experimental studies using dilatometer, microstructures containing ferrite and martensite were produced by intermediate quenching method with annealing at different temperatures followed by water quenching. Before the intermediate quenching, the specimens were first quenched to form martensite from austenitizing temperature of 1100 °C. Fully martensitic samples were then annealed respectively at 725, 730, 740, 750 °C for 15 min and quenched. During the annealing, the austenite nucleates and grows at former boundaries of the martensite plates resulting fibrous microstructure of martensite and ferrite. Microstructural investigations were carried out using light microscope and scanning electron microscope to investigate the effect of the increasing annealing temperature on the microstructure. Vickers test was applied to specimens. The calculations and experimental results show that hot rolled medium carbon steels are suitable to produce a dual phase microstructure. It was observed that increasing annealing temperature increases the amount of martensite and hardness because martensite is the main phase controls the hardness value of steel. It is observed that the A1 and A3 temperatures are very close and the percentage of austenite is much more than conventionally produced dual phase steels. It is related to including more carbon content than conventionally produced dual phase steel.

2023

This study aim is to determine the influence of Cu addition on microstructure and strength of low carbon steel. 0.1% C steel, which contained Cu were used as specimens. The temperatures for heat treatment were determined using a software. The type of specimens was heat treated at specific temperatures in order to obtain 20% and 80% of martensite. Specimens were austenised at 1000 °C for 30 second and followed by water quenching to obtain martensitic structure. The base steel used as the base metal as specimen. The hardness increases with increasing temperature for both of steels. It is found that the hardness, yield strength and ultimate tensile strength of Cu was higher than Base steel. Changes of hardness of annealed samples almost the same in both steels. On the other hand, it is found that addition of Cu can improve tensile strength, total elongation and strength-ductility balance of the steel although no significant effect on yield stress and uniform elongation. Total elongation for Cu steel is 19%, and base steel the elongation values are 15% respectively. Although the martensite content is the same. Total hardness for Cu steel is 390 Hv and 281.8 Hv. However, the Cu steel has the highest hardness than base steel. Therefore, the addition of Cu will increase the hardness, strength and elongation of steel.

2023

Medium Mn steels (C = 0.15-0.19 wt.%, Mn = 5.00-5.20 wt.%) with variation of Si content (1.9, 2.45, 3.4 wt.%) were prepared using vacuum induction melting furnace. The cast billets were forged and cooled to room temperature in air. Microstructural investigation of the forged alloys showed fully martensitic structure along with minor content of retained austenite. With Si content, the hardness of forged steel were found to be increasing. The transition temperatures (Ac1, Ac3, Ms, and Mf) were determined using differential scanning calorimetry (DSC) measurements. Increase of Si content raised Ac1 and Ac3 and caused reduction in Msand Mf. The forged samples were austenized at 900 °C for 15 min, followed by isothermal holding at 700 °C for 1 and 4 h and water quenched. The microstructure consisted of ferrite, martensite, and retained austenite. Microhardness measurements of heat-treated steels also showed significant enhancement of mechanical strength with increase of Si content.

2023

Interest in 2219 Al alloys as potential structural materials for aircraft and space applications, is mainly due to their high strength to weight ratio. These wrought alloys are generally used after deformation processing followed by a sequence of heat treatments. Thus a clear understanding of the process parameters related to thermo-mechanical treatments (plastic working and age-hardening heat treatments) imparted before the final use is necessary for obtaining the desired mechanical properties. Microalloying (< 0.1 wt.%) with elements such as Sn, In, Cd, Ag, Si, etc. is currently being explored for achieving still higher strength to weight ratio. The materials seldom also demand reasonably good impact strength or toughness properties with high strength and hardness. The present research is hence aimed at investigating the influence of rolling and age-hardening on the combined hardness and impact properties of 2219 Al alloy with trace and varying (0, 0.06 and 0.1 wt.%) contents o...

2023, MRS Proceedings

2023, Journal of Thermal Analysis and Calorimetry

This work deals with determining temperatures of phase transformations in steel S34MnV in a low-temperature region (below 900°C). Although S34MnV is a significant tool steel, in the literature, there are only a few works dealing with the study of the thermo-physical properties of this steel. For the study of phase transformation temperatures of steel S34MnV, a differential thermal analysis and dilatometry were used in this study. Both methods are used to determine the phase transformation temperatures of steel. Dilatometry, however, unlike differential thermal analysis, is commonly used to determine the temperature of nonequilibrium phase transformations during cooling. Temperatures of the eutectoid phase transformation (A c1) and temperatures of the end of the ferrite to austenite transformation (A c3) were obtained at heating, and temperatures of the start of the ferrite formation (A r3), the temperature of the start of the pearlite formation (A r1) and the temperature of the start of the bainite formation (B S) were obtained at cooling using these methods. The temperatures obtained using the both methods were compared and discussed. The original thermophysical data on steel S34MnV were obtained under precisely defined conditions. For the complexity of the study of the steel, a metallographic analysis of samples was also conducted after thermal analysis, which enables determining the phases occurring in the final structure and their quantity. The experimentally obtained data were compared with data calculated by the software QTSteel.

2023, Journal of Metallurgy

The transformation of iron carbide cementite was investigated on spheroidal graphite containing different contents of manganese. The isothermal maintain were carried out at 600, 650, 700, and 750 • C for periods of up to one hour. It was... more

2023, Archives of Civil and Mechanical Engineering

In this study, dual-phase (DP, ferrite + martensite) microstructures were obtained by performing intercritical heat treatments (IHT) at 750 and 800 °C followed by quenching. Decreasing the IHT temperature from 800 to 750 °C leads to: (i) a decrease in the volume fraction of austenite (martensite after quenching) from 0.68 to 0.36; (ii) ~ 100 °C decrease in martensite start temperature (Ms), mainly due to the higher carbon content of austenite and its smaller grains at 750 °C; (iii) a reduction in the block size of martensite from 1.9 to 1.2 μm as measured by EBSD. Having a higher carbon content and a finer block size, the localized microhardness of martensite islands increases from 380 HV (800 °C) to 504 HV (750 °C). Moreover, despite the different volume fractions of martensite obtained in DP microstructures, the hardness of the steels remained unchanged by changing the IHT temperature (~ 234 to 238 HV). Applying lower IHT temperature (lower fraction of martensite), the impact ener...

2023, The Scientific Bulletin of "Valahia" University

An important category of widely used steels is chromium alloy improvement steels (STAS 9382/4-89) intended for the execution of shafts, axles, cams, sprockets and sprockets subjected to operation at important demands. The properties of these steels are determined both by the chemical composition and by the way of plastic elaboration and deformation, but also by the way in which the structural transformations to the thermal treatments of tempering and recovery result. The properties of a certain steel are largely determined by the granulation size of the secondary structure, which in turn is dependent on the size of the austenitic granulation, respectively the hereditary granulation. At a given steel mark, the mode of heating (slow or fast) at the austenitization temperature is decisive regarding the dimensions of the austenitic grain respectively of the nature of the secondary granulation and of the operating properties. Studies and research were conducted on steels with an average content of 0.5% C (OLC 50, 40Cr10, 40Cr30), respectively alloys and chromium alloys. The experimental results show that the number of germs increases with the increase of the heating rate at austenitization. Along with the influence it has on the number of germs, the speed of heating manifests its effects on the critical temperatures of transformation. The presence of chromium additions is manifested by phenomena of carbide stabilization.

2023, Journal of Materials Engineering and Performance

The high temperature thermal expansion coefficient (TEC) and elastic modulus of five steels used in mill rolls production were investigated by dilatometer and impulse excitation techniques (IET). The measurements were provided at heating from room temperature till temperatures of about 1000°C and subsequent cooling. The obtained data were attributed to the properties of predominating phases (austenite, martensite, pearlite, and bainite). The TEC and elastic modulus of corresponding phases were similar for all investigated steels despite the difference in their chemical composition. The steels with a chromium content of 2.95 wt.% and more show enhanced ability to quench hardening. This is an important prerequisite for production of high quality mill rolls.

2023, Metals

The present work presents a theoretical and experimental study regarding the microstructure, phase transformations and mechanical properties of advanced high-strength steels (AHSS) of third generation produced by thermal cycles similar than those used in a continuous annealing and galvanizing (CAG) process. The evolution of microstructure and phase transformations were discussed from the behavior of intercritical continuous cooling transformation diagrams calculated with the software JMatPro, and further characterization of the steel by scanning electron microscopy, optical microscopy and dilatometry. Mechanical properties were estimated with a mathematical model obtained as a function of the alloying elements concentrations by multiple linear regression, and then compared to the experimental mechanical properties determined by uniaxial tensile tests. It was found that AHSS of third generation can be obtained by thermal cycles simulating CAG lines through modifications in chemistry ...

2023, Journal of Materials Engineering and Performance

2023

2023, IOP conference series

Paper deals with phase transformations and austenitizing behaviour of the OCHN3MFA high strength steel. Dilatation analysis of a series of samples was performed at various cooling rates, selected in the range from 100 °C s-1 to 0.01 °C s-1. Acquired experimental data were used to evaluate dilatometric curves in order to map the temperature ranges of austenite to ferrite, bainite or martensite. Then, all experimental samples from dilatometric analysis, were subjected to microstructural analysis and hardness measurements to characterize the microstructure and hardness for each tested heat treatment regime.

2023, Science & Military

The article deals with phase transformations and austenitizing behavior of the X155CrMoV12 tool steel. Dilatation analyses of a series of samples were performed at various cooling rates, chosen in the range from 10 °C·s-1 to 0.1 °C·s-1. Acquired experimental data were used for evaluation of dilatometric curves in order to map the temperature ranges of phase transformations of the austenite to pearlite, bainite or martensite. All experimental samples from dilatometric analyses were then subjected to microstructural analyses and hardness measurements to characterize the microstructure and hardness for every tested heat treatment regime. The second part of this article, entitled "EXPERIMENTAL DETERMINATION OF CONTINUOUS COOLING TRANSFORMATION DIAGRAM FOR HIGH STRENGTH STEEL X153CRMOV12", deals with these analyses of the cooling curve microstructure.

2023, Materials

2023, Metalurgija

The article deals with phase transformations and austenitizing behavior of the X155CrMoV12 tool steel. Dilatation analyses of a series of samples were performed at various cooling rates, chosen in the range from 10 °C/s to 0,1° C/s. Acquired experimental data were used for evaluation of dilatometric curves in order to map the temperature ranges of phase transformations of the austenite to pearlite, bainite or martensite. All experimental samples from dilatometric analyses were then subjected to microstructural analyses and hardness measurements to characterize the microstructure and hardness for each tested heat treatment regime.

2023, MRS Proceedings

2023, ISIJ International

Present study aims to predict the effect of Ti, B, Cu and Ni on continuous cooling transformation diagrams of low carbon (0.04-0.05 wt%) steels by artificial neural network model. The predicted results are validated with dilatometric studies. Comparison of the phase fields in different continuous cooling transformation diagrams demonstrated that in Ni containing 1.5 wt% Cu-added Ti-B microalloyed steel it is possible to achieve dual phase (ferrite-martensite) microstructure in directly air-cooled condition (i.e., at cooling rate close to 1°C/s) by suppressing pearlite formation. Addition of Cu has remarkably improved the hardness of the dilatometric samples.

2023, Rem: Revista Escola de Minas

The variation in critical temperatures for the formation of austenite when increasing the heating rate was studied by dilatometry. The analysis was performed at heating rates between 10 and 90ºC/s. Empirical equations are herein proposed for calculating Ac3 with respect to the heating rate. The results showed that an increase in the heating rate had no influence on Ac1, but Ac3 increased 115ºC. The equations proved to be of a more general use, as they also predicted the results of works on other steels with high values of correlation coefficients.

2023, Metals

Continuous cooling transformation (CCT) diagrams of base metals are common in welding. They can be built using physical or numerical simulations, each with advantages and limitations. However, those are not usual for weld metal, considering its variable composition due to the dilution of the weld into the base metal. Wire Arc Additive Manufacturing (WAAM) is a distinctive case in which the interest in materials comparable with weld composition raises attention to estimating their mechanical properties. Notwithstanding, this concept is still not used in WAAM. Therefore, the aim of this work was to address a methodology to raise MC-CCT (Multiple Cycle Continuous Cooling Transformation) diagrams for WAAM by combining physical and numerical simulations. A high-strength low-alloy steel (HSLA) feedstock (a combination of a wire and a shielding gas) was used as a case study. To keep CCT as representative as possible, the typical multiple thermal cycles for additive manufacturing thin walls...

2023, Metals

In the present work, a Cr+Mo+Si low-alloyed low-carbon steel was fabricated at laboratory scale and processed to produce multiphase advanced high-strength steels (AHSS), under thermal cycles similar to those used in a continuous annealing and galvanizing process. Cold-rolled steel samples with a microstructure constituted of pearlite, bainite, and martensite in a matrix ferrite, were subjected to an intercritical annealing (817.5 °C, 15 s) and further isothermal bainitic treatment (IBT) to investigate the effects of time (30 s, 60 s, and 120 s) and temperature (425 °C, 450 °C, and 475 °C) on the resulting microstructure and mechanical properties. Results of an in situ phase transformation analysis show that annealing in the two-phase region leads to a microstructure of ferrite + austenite; the latter transforms, on cooling to IBT, to pro-eutectoid ferrite and bainite, and the austenite-to-bainite transformation advanced during IBT holding. On final cooling to room temperature, auste...

2023, Materials & Design

Two medium carbon steel grades were used in the present investigation. One of them was microalloyed with vanadium. Both steel grades were subjected to a controlled closed die forging followed by cooling in sand, air or oil mediums. Final microstructures and mechanical properties were evaluated by optical microscopy, scanning electron microscopy, hardness and tensile tests. The results indicated that the microstructures of all close die forging and cooling conditions are dominated by ferrite and pearlite phases with different morphologies and grain sizes according to both chemical composition and cooling rate. Oil quenching leads to a formation of relatively fine ferrite and pearlite in medium carbon steel (MC) or martensite in medium carbon microalloyed steel (MC-MA). Relatively fine ferrite, pearlite and martensite increase strength but decrease ductility. The cooling rate has a remarkable effect on the microstructure and mechanical properties at room temperature.

2023, Materials

2023, Metalurgija

The article deals with phase transformations and austenitizing behavior of the X155CrMoV12 tool steel. Dilatation analyses of a series of samples were performed at various cooling rates, chosen in the range from 10 °C/s to 0,1° C/s. Acquired experimental data were used for evaluation of dilatometric curves in order to map the temperature ranges of phase transformations of the austenite to pearlite, bainite or martensite. All experimental samples from dilatometric analyses were then subjected to microstructural analyses and hardness measurements to characterize the microstructure and hardness for each tested heat treatment regime.