Pearlite Interlamellar Spacing Research Articles

Study on the effect of ultrasonic treatment for fabricating nodular cast iron with improved mechanical properties

In this paper, a novel ultrasonic treatment technique was proposed in nodular cast iron melt with the aim of improving the microstructure and mechanical properties of nodular cast iron. The effects of ultrasound on the microstructures and properties were investigated by comparing experiments with and without ultrasound. The results showed that compared with the NO UT specimen, the mean equivalent diameter of graphite nodules was reduced by 46% in the UT 105 s specimen, while the mean roundness and nodule count per unit area were increased by 33.9% and 43.6%, respectively. In addition, the ultrasonic treatment of melt could increase the pearlite content, refine the matrix microstructure and reduce the pearlite interlamellar spacing from 392.7 nm to 231.3 nm. Compared with the NO UT specimen, the mechanical properties of the UT specimen were improved significantly, and could up to UTS of 739 MPa, YS of 579 MPa and El of 9.4% in the UT 105 s specimen. In this work, the mechanism of ultrasonic action on nodular cast iron also was discussed in detail.

Impact of interlamellar spacing and non-pearlitic features on mechanical properties and cyclic damage initiation in near-eutectoid pearlitic steels

The relationship between microstructural characteristics and mechanical properties was investigated for C72 and C82 pearlitic steel rods patented at temperatures between 500 °C and 600 °C using a lead bath. Results revealed a refinement of interlamellar spacing upon reduction of patenting temperature. At the same time, the fraction of grain-boundary ferrite and Widmanstätten ferrite as common non-pearlitic regions was slightly increased, reaching a maximum of nearly 1.3 vol.-% in the case of C72 steel patented at 500 °C. Reduction of patenting temperature was associated with strengthening, as confirmed by tensile, fatigue and hardness tests. The strengthening was explained in terms of the Hall-Petch effect for ferrite due to increase in the boundary area. The Hall-Petch coefficient, obtained by taking the apparent interlamellar spacing as the mean free path of dislocations, was in the range 70–140 MPa.μm12. To some extent, these low values could be related to the low solute interstitial content of pearlitic ferrite. More importantly, the coefficients are underestimated due to the plate-shaped morphology of pearlitic ferrite, which causes the average mean free path of dislocations be longer than the apparent interlamellar spacing. Scanning electron microscopy examinations after interrupted fatigue tests indicated the preferred occurrence of intrusions and extrusions, as precursors to fatigue crack, in the non-pearlitic ferrite. The enhancement of fatigue limit at lower patenting temperatures—in spite of slight increase in the fraction of ferrite—is justified by the stress shielding effect of pearlite and necessity of crack propagation into pearlitic regions for stable crack propagation. In effect, as long as the fraction of non-pearlitic features remains low, the interlamellar spacing of pearlite serves as the most efficient strength-controlling microstructural parameter. Furthermore, due to the preferred growth of fatigue cracks parallel to lamellae and deflection at colony boundaries, the refinement of colonies at reduced patenting temperatures is an additional contribution to the fatigue strength.

Machine learning assisted materials design of high-speed railway wheel with better fatigue performance

To improve the fatigue fracture resistance of high-speed railway wheels, this paper studies the matching optimization design of microscopic crystal parameters of wheel materials based on machine learning methods. The microscopic crystal parameters of a pearlitic steel of high-speed railway wheel are collected, the relationship between microscopic crystal parameters and material properties of wheel material is studied. Based on machine learning methods including artificial neural network, random forest, support vector machine and K-nearest neighbor, the influence of the microscopic crystal parameters on the material properties of wheel steel is studied. The results show that the artificial neural network has a higher prediction accuracy, the microstructure parameters have a complex effect on fatigue performance of the wheel. When the prior austenite grain size of the structure is 55–65 μm, the pearlite colony size is 27–29 μm, and the pearlite interlamellar spacing is 95–105 nm, the fatigue resistance of the wheel steel is the best, and the fatigue strength is 528 MPa. The optimization result meets the requirements of high-speed railway wheel strength evaluation standard with a higher safetyfactor by finite element simulation.

Pearlite Interlamellar Spacing and Vickers Micro-Hardness in the Necking Region of Cold-Drawn Pearlitic Steel Wires

The final aim of this paper is to study the microstructural changes in the necking region of progressively cold-drawn pearlitic steel wires by means of a thorough and detailed analysis of pearlite interlamellar spacing and Vickers micro-hardness in this special region. To this end, a set of progressively cold-drawn pearlitic steel wires belonging to a real manufacturing chain were subjected to standard tension tests, in such a manner that the tests were interrupted before the final fracture, i.e., the test development was aborted just at the necking instant. The microstructural changes during necking were evaluated by measuring the pearlite interlamellar spacing in the necking region, as well as the Vickers micro-hardness in the different points of it. The study of the afore-said microstructural changes preceding the final fracture was the final aim of the research, intending to determine the local areas in the necking region of the specimens in which microstructural changes are most evident, thereby affecting the local mechanical response of a specific cold-drawn steel at the moment of instability under load control during the standard tension test.

Microstructure and mechanical properties of Nb microalloyed high‑carbon pearlitic steels subjected to isothermal transformation

Niobium (Nb) is mainly added to low-carbon steels, in which the main microstructure is ferrite and/or bainite, to refine grains and improve their properties. However, the studies on Nb in high-carbon pearlitic steels are insufficient, and there are some debates regarding the existing studies. High-carbon pearlitic steel is widely used in bars, wires, and steel rails. The role of Nb in high-carbon steels may differ for different steel grades and under different heat treatments. Hence, further detailed studies are required to improve the properties of high-carbon pearlitic steels. In this study, two series of high-carbon pearlitic steels (68C and 75C series) were designed and subjected to isothermal pearlite transformation at different austenitization and isothermal transformation temperatures. The microstructures and mechanical properties of the steels were investigated by optical microscopy, field-emission scanning electron microscopy, electron backscatter diffraction, scanning transmission electron microscopy, and hardness tests. The results showed that the pearlite lamellae were refined by the addition of Nb to high-carbon pearlitic steels, which was attributed to the solute drag effect of Nb. The pearlite colony and nodule sizes also became finer with the addition of Nb because of the finer prior austenite grains and smaller pearlite growth rates. However, the refinement of the pearlite lamellae, nodules, and colonies by the addition of Nb was not significantly enhanced by increasing the Nb content from 0.014 wt% to 0.027 wt% in 75C series samples. In addition, the pearlite interlamellar spacing and colony and nodule sizes of the samples decreased with decreasing isothermal and austenitization temperatures. Moreover, the addition of Nb to high-carbon steels increased their hardness and yield strength. The main strengthening mechanisms of Nb in high-carbon steel are grain refinement strengthening and precipitation strengthening in the samples austenitized at 900 °C, whereas the improvement of strength is mainly attributed to grain refinement strengthening in the samples austenitized at 1180 °C. This study systematically characterized the pearlite morphology of Nb microalloyed high-carbon steels and analyzed the strengthening mechanism, providing a theoretical reference for the development of Nb-containing high-carbon pearlitic steels.

Adiabatic shearing in railway wheel steel of high-speed train

Adiabatic shearing behavior in the web and the rim of high-speed train railway wheel steel was investigated using a split Hopkinson pressure bar (SHPB) with hat-shaped punch shear technique. Different initial microstructure characteristics were observed in the web and the rim specimens experiencing different heat treatment. For the first time we show that the pre-eutectoid ferrite deforms at first and pearlite interlamellar spacing has a significant influence on structural softening sequence during shear band evolution in the railway wheel steel, and shear bands are more prone to emerge in the rim.

On ascertaining hardness‐microstructure relationship in annealed steel for varying carbon content

AbstractPlain carbon steels of five different carbon contents up to eutectoid composition have been provided with the conventional full annealing treatment. Qualitative and quantitative studies of the microstructure are carried out using optical microscopy and field emission scanning electron microscopy techniques. Even under similar cooling rate pertaining to the full annealing treatment (furnace cooling); microstructural modifications of individual microconstituents are feasible with varying chemistry (carbon content) of plain carbon steel. The refinement of microstructure for both proeutectoid α‐ferrite and pearlite is found to be accentuated with increasing carbon content of annealed steels till eutectoid composition. Hall‐Petch type relationship explains adequately the relationship between hardness and the size of the microconstituent both in terms of the grain size of proeutectoid α‐ferrite and the interlamellar spacing of pearlite. Henceforth an empirical relationship is developed for the first time taking into account the rule of mixture to correlate overall hardness, carbon content, grain size of proeutectoid α‐ferrite and interlamellar spacing of pearlite. The empirical relationship originated thereby is found to closely match the experimental results.

Microstructural Evolution of SK85 Pearlitic Steel Deformed by Heavy Cold Rolling.

The microstructural evolution of SK85 pearlitic steel cold-rolled up to a 90% rolling reduction was characterized by scanning electron microscopy with electron backscattered diffraction (EBSD) and X-ray diffraction (XRD). SK85 steel exhibits excellent cold rolling performance. The interlamellar spacing of pearlite is refined obviously and a tensile strength of 2318 MPa can be reached for SK85 steel after 90% rolling reduction, an increase of 83% from 1264 MPa before rolling. The EBSD observation indicates that the {001} <110> texture becomes pronounced at a 90% rolling reduction in cold-rolled Sk85 steel. A propagation and multiplication of dislocations occur during rolling as the kernel average misorientation (KAM) angles significantly increase from 0.72° to 2.11°. The XRD analysis reveals that bcc ferrite is transformed into a bct structure at a 90% rolling reduction. The strengthening mechanism was discussed.

Effect of chemical composition and microstructure on the crack growth and machinability of GG20 gray cast iron for brake drum application

The objective of the present study is to investigate the effect of chemical composition and microstructure on machinability, mechanical properties, and crack growth of GG-20 gray cast iron for brake drum application. The effects of a reduction in C and Si on microstructural parameters such as type, size, and aspect ratio of graphite particles, interlamellar spacing of pearlite, and the presence of MnS were investigated. In the following, the effect of different microstructures on mechanical properties and machinability of cast iron were studied. The fracture surface, crack growth, worn surface, chip formation and wear on cutting tools have been studied as well. The results showed that both tensile strength and hardness increased, and the machinability reduced by decreasing C and Si. By reducing the C content from 3.4% to 3.2%, the maximum hardness value and tensile strength were obtained to be 207HB and 286 MPa, respectively. Moreover, the Ra and Rz values were increased to 4.3 μm and 25.8 μm, respectively. With an increase in the length of graphite flakes, the distance between microcracks on the machined chips decreased. In the sample with the lower hardness value, delamination occurred extensively and led to the disappearance of cracks and pores on the worn surface.

Effect of track curvature on the microstructure evolution and cracking in the longitudinal section of lower gauge corner flow lips formed in rails

The microstructure of the flow lips formed at the lower corner of gauge face in the longitudinal section of worn high rails serving in curved tracks has been investigated. The radii of the curved tracks are 1500 m (S1, sharper curve) and 4000 m (S2, milder curve). Sharper curves result in a higher angle of attack (AOA) between rail-wheel thus leading to higher lateral contact forces as well as tangential frictional forces thus facilitating plastic flow. Such conditions favour formation of flow lips where rail material flows from the rail upper gauge face to the lower corner of the gauge face. A combination of optical microscopy (OM), scanning electron microscopy (SEM), electron backscattered diffraction (EBSD) and nano-indentation hardness measurements have been used for the characterization of the flow lip. It is observed that the outermost region of the flow lip consists of a uniformly present white etching layer (WEL) followed by an intermittently present brown etching layer (BEL) where the WEL and BEL thickness is less for milder curves. The WEL has the highest hardness and consists of fine grains of ferrite and particles/fine fragments of cementite. The BEL is relatively softer than WEL and has a similar appearance to WEL, but patches of lamellar structure appear with increasing depth from the outer edge. Beyond the BEL region, layers of deformed pearlitic structure are observed, and a more intact pearlitic structure is observed at a much lower depth for the milder curve than the sharper curve. For both the curvatures at a given depth, the hardness of pearlite bears a Hall-Petch type of relationship to the pearlitic interlamellar spacing. However, the alignment of the deformed microstructure is heavily dependent on the curvature. It has been found to align almost parallel (4°–10°) to the rail longitudinal axis for the milder curvature and at around 21°–35° for the sharper curvature. Cracks originate from the brittle WEL region due to contact fatigue whereas crack propagation is driven by bending stresses. Cracks have been found to move parallel to the alignment of the deformed pearlite along longitudinal direction for the milder curvature. Alignment of pearlite also motivates the crack propagation trajectory for the sharper curvature and hence the crack moves at an angle between 21° and 35° with the longitudinal direction but becomes almost perpendicular after a distance. Shallow cracks travelling parallel to the rail outer edge in S2 can result in spalling of the rail material leading to wear, whereas for sharper curves, cracks run deeper into the railhead. Thus, the tendency for rail failure through 'Reverse Transverse Fracture' – which involves crack initiation at the lower gauge corner and propagation into the railhead – increases with the sharpness of the rail curvature.

Improving mechanical properties in high-carbon pearlitic steels by replacing partial V with Nb

The effects of combined addition of niobium (Nb) and vanadium (V) on the transformation, microstructure and mechanical properties of high-carbon pearlitic steels were investigated. In-situ observations on a high-temperature laser scanning confocal microscope (LSCM) were conducted to study the pearlitic transformation, the results from which indicate that single V or combined Nb and V addition led to higher transformation temperature and more pearlitic nucleation sites. But the growth rate of pearlite was significantly impeded due to the smaller diffusion coefficient of carbon, resulting in the refinement of the interlamellar spacing and nodule size of pearlite. In addition, compared to the base steel, single V addition in high carbon pearlitic steels was beneficial to the increase of strength, but it deteriorated the toughness, whereas the composited addition of Nb and V resulted in the increase of strength without the expense of the toughness. It is concluded that replacing part V with similar content of Nb is very promising since the impact toughness of the Nb + V steel is increased by 21% without the expense of the strength compared to the V-microalloyed steel. Nb and V strengthened pearlitic steels primarily due to the precipitation of M(C,N), thinner pearlite interlamellar spacing and smaller pearlite nodule size. Compared to the V steel, the improvement of toughness in Nb + V steel was mainly attributed to the smaller nodule size and more uniform grain size distribution. In summary, under the premise of similar microalloying element amount in high-carbon (∼0.77 wt%) pearlitic steels, replacing part V with Nb is beneficial to obtain the finest microstructure and the best comprehensive mechanical properties.

Effect of Niobium on Microstructure and Mechanical Properties of a Hypereutectoid Steel

High-carbon steels have been used to high-strength steel wire and strands for prestressing concrete. The necessity of high-strength levels at increasingly larger diameters of wire rods is a technological challenge. Two steels with and without Nb were obtained in a steel mill, submitted to detailed microstructural (previous austenitic grain size, pearlite interlamellar spacing and colony size) and mechanical characterization through tensile tests and hardness. Hot torsion and dilatometry tests were performed to simulate steels processing and to verify the influence of Nb on phase transformation. Adding Nb to steel resulted in a refinement in austenitic grain size and pearlite colonies but had no effect on pearlitic interlamellar spacing. There was a decrease at the start transformation temperature austenite/pearlite and therefore an increase in the hardenability of the Nb-added steel. Finally, Nb addition proved to be a technical and economical way to increase tensile strength and to reduce the variability of the mechanical properties.

Microstructure and strength in ultrastrong cold-drawn medium carbon steel

Via traditional wire drawing, the medium carbon ferrite-pearlite (MCFP) steel wires can achieve the ultrahigh strength beyond 4 GPa normally for high-carbon pearlitic steel wires, but have a 30–60% lower production cost. The microstructural evolution and mechanical properties of medium carbon ferrite-pearlite steel wires have been investigated by means of scanning electron microscopy, transmission electron microscopy and tensile testing. The tensile strength of medium carbon ferrite-pearlite steel wires increases from 750 MPa up to 4120 MPa when the drawing strain increases up to ε = 6.4, which represents the highest strength reported so far – to our knowledge for a carbon steel with such low carbon content. At low and medium strains (ε ≤ 1.95), the proeutectoid ferrite forms dense dislocation walls (DDWs) via dislocation activities, including sliding, accumulation, interaction, and tangling. With the drawing strain increase, the reorientation of DDWs to the drawing direction forms the coarse proeutectoid ferrite lamellae. Finally, the proeutectoid ferrite deformed to high strains is characterized by a lamellar morphology and the average lamellar spacing of proeutectoid ferrite is about 55 nm at ε = 6.4. The interlamellar spacing of pearlite and thickness of cementite decreases with the drawing strain increases. The dislocation density in ferrite lamellae increases with the drawing strain increases, and the dislocation density in ferrite lamellae is 7.8 × 1015 m−2 at ε = 4.19. A higher dislocation density of 3.1 × 1016 m−2 can be obtained at ε = 6.4 by means of extrapolation and TEM investigations. The stress contributions of proeutectoid ferrite and pearlite to the flow stress are estimated based on quantified structural parameters. Based on the assumption that the stress contributions from different strengthening mechanisms are linearly additive and the general rule of mixtures, a good agreement between the measured and estimated flow stresses has been found in a large range of flow stress. The good application of the general rule of mixture to the medium carbon ferrite-pearlite steel wires indicates the importance of quantitative characterization of microstructural evolution and parameters with the strain.

The Precipitation of Niobium Carbide and Its Influence on the Structure of HT250 for Automobile Wheel Hubs

Improving the strength of grey cast iron wheel hubs will improve the safety of automobiles and have a great significance for energy saving and environmental protection. This paper systematically compares the calculation results of Python-based precipitation calculation and JmatPro software simulation with experiments. The results show that with a low mass fraction of niobium (0.098%) cuboid Niobium Carbide (NbC) precipitates do not form in the liquid phase; however, an elongated NbC niobium-rich phase may form during the solidification process and in the solid phase. However, cuboid NbC precipitates can be precipitated from the liquid phase when the niobium mass fraction is higher (0.27%, 0.46%). These results indicate that with the increasing niobium content the amount, particle size, and initial precipitation temperature of niobium carbide precipitated in the matrix structure will increase. According to the observation and statistical analysis of the microstructure, it is found that tensile strength will be improved with an increase in niobium content due to the refinement of the graphite and pearlite interlamellar spacing. In this paper, adding less than 0.32% of Nb to grey cast iron is recommended, considering the comprehensive cost and the effect of niobium in the material structure.

Experimental Study on Rare Earth and Magnesium Composite Treatment of 49MnVS3 Non‐quenched and Tempered Steel

Nowadays, under the context of severe resource shortage, it is urgent to develop non‐quenched and tempered steel. Herein, a new method of combining rare‐earth cerium (Ce) and magnesium (Mg) to treat the 49MnVS3 steel with low oxygen and rather high sulfur is proposed. The inclusions modification, microstructure evolution, and mechanical properties change of 49MnVS3 steel with different Ce and Mg content composite treatment are investigated by optical microscope (OM), scanning electron microscope (SEM)–energy‐dispersive spectrometer (EDS), electron probe microanalyzer (EPMA), and tensile and impact tests. The results indicate that the small spherical Ce–Mn–Mg–O–S composite inclusions replace the Al2O3 wrapped MnS composite inclusions and elongated MnS inclusions after Ce and Mg joint treatment. After Ce and Mg composite treatment, the proportion of ferrite is significantly improved. Meanwhile, the interlamellar spacing of pearlite is refined. Attributed to modified inclusions and optimized microstructure, the strength and impact toughness are gradually enhanced. In contrast to Ce–Mg free steel, the impact energy of 4# steel with 0.0122 wt% Ce and 0.0012 wt% Mg addition is increased by 33%. In the current study, the optimal mass fractions of Ce and Mg are 0.0122 and 0.0012 wt%, respectively.

Investigation on the relationship between microstructure and wear characteristic of rail materials

The purpose of this study was to investigate the relationship between the microstructure and the wear characteristic of rail materials. Different rail materials with different austenite grain sizes (40–135 µm), pearlite colony sizes (5.4–10.6 µm) and pearlite interlamellar spacings (0.16–0.33 µm) were obtained through heat treatment. Rolling-sliding wear tests were performed. With the increases in the microstructure size (i.e., pearlite interlamellar spacing, pearlite colony size and austenite grain size), the wear rates of rail material were increased. The pearlite colony size has the most significant influence on wear resistance, followed by the pearlite interlamellar spacing and the austenite grain size. With the increase in the microstructure size, the lengths of rolling contact fatigue cracks were decreased but the crack angles were increased.

Strain localization and deformation behavior in ferrite-pearlite steel unraveled by high-resolution in-situ testing integrated with crystal plasticity simulations

This paper attempts to study the microstructural stress-strain evolution and strain localization in the ferrite-pearlite steel by high-resolution experimental-numerical integrated testing. Ferrite crystal orientations measured by electron backscatter diffraction (EBSD) were mapped onto precise scanning electron microscopy (SEM) micrographs of ferrite and cementite lamellar morphologies. Furthermore, in-situ SEM tensile testing was employed to map strains during the deformation using digital image correlation (DIC) at high spatial resolutions. Finally, spectral solver-based crystal plasticity (CP) simulations loaded by the local SEM-DIC boundary conditions were performed and compared to the experimental data. Crucially, all microstructure data was carefully aligned, and strains were filtered to the same spatial resolution, measured to be as small as ~75 nm. This integrated methodology yields new insights in the high degree of plastic strain partitioning between ferrite grains and pearlite colonies, and ferrite and cementite lamellae inside pearlite. One-to-one experimental-numerical comparison augmented with the numerical variation of the ferrite constitutive model, pearlite interlamellar spacing, and lamellar orientation reveals how the ferrite-cementite strain partitioning and the onset of strain localization depend on the morphology and distribution of ferrite grains and pearlite colonies. Importantly, this comparison showcases the limitations of state-of-the-art simulations in their capability to predict specific mechanisms and correct degrees of strain heterogeneity.

Numerical Simulation of Wire Rod Cooling in Eutectoid Steel under Forced-Convection

A coupled thermal-microstructural simulation model was developed to estimate the thermal history in a eutectoid steel wire rod under continuous cooling and forced-convection. The model coupled the phenomena of heat transfer, phase transformation and estimation of the cooling boundary condition. The thermal histories were analyzed at different cooling rates to emulate the forced-convection conditions by air-jet as in the controlled cooling conveyor. The thermal histories were acquired and used to calculate the forced-convection heat transfer coefficients through the solution of the Inverse Heat Conduction Problem, while the phase transformation was approximated with the Johnson–Mehl–Avrami–Kolmogorov (JMAK) kinetic model. From the heat transfer coefficients and the kinetic parameters, a user-defined function (UDF) was coded and employed in the ANSYS Fluent® software. The model results were compared and validated with the experimental histories, obtaining a good agreement between both responses, while the microstructural evolution of the pearlite was validated using Scanning Electron Microscopy (SEM) and Vickers microhardness. It was found that specimen diameter and air velocity are the main variables to modify the undercooling and therefore the pearlite interlamellar spacing.

Evolution of the Microstructure and Properties for 2000 MPA Bridge Cable Steel

In this paper, the microstructure, texture and mechanical properties of pearlite steel wires produced using different processes were investigated by mechanical testing and electron microscopy techniques including combining SEM, TEM and XRD to reveal the evolution of the microstructure and properties of 2000 MPa bridge cable steel. The experiments were carried out under industrial conditions. The microstructural observations indicate that the orientation of the lamellar pearlite in the steel rod is random and that patenting produces a fully pearlitic microstructure with a fine pearlitic interlamellar spacing. The pearlitic lamellae of the wires tilt and stretch toward the drawing direction during cold drawing. Although the cementite of the cold drawn wires retains a laminar shape, partial fragmentation of the cementite lamella occurs. A large number of SBs appear in the galvanized steel wire, and fragmentation of the cementite lamella is more obvious. After cold drawing, the orientation of the 〈110〉 texture intensifies and becomes dominant. However, the intensity of the 〈110〉 texture decreases slightly after galvanizing. The results from the mechanical experiments show that the hardness and tensile strength of the steel wires increase rapidly after cold drawing before reaching a peak. However, the hardness and tensile strength of the galvanized steel wire decrease slightly.

Direct Observation of Austenite and Pearlite Formation in Thermally Simulated Coarse Grain Heat-Affected Zone of Pearlite Railway Steel

In the present study, coarse grain heat affected zone (CGHAZ) of the pearlite railway steel was thermally simulated at different cooling rates ranging from 1 to 4 °C/s to in–situ observe the austenite and pearlite formation by high temperature laser scanning confocal microscopy (HT–LSCM). During heating, austenite nucleation was started at 811 °C at fast heating rate of 9.1 °C/s. Pearlite was completely decomposed into austenite in 21 s at 1005 °C. At peak temperature of 1300 °C, austenite was composed of two microstructural compositions, i.e., high-carbon austenite and low-carbon austenite. Homogenization of austenite and formation of grain boundaries were continued even during cooling when the temperature was above the pearlite transformation. During cooling, Low-carbon austenite has increased the pearlite transformation by providing additional nucleation sites. By increasing the cooling rate from 1 to 4 °C/s, the pearlite transformation temperature was reducing, pearlite growth rate was increasing, and pearlite interlamellar spacing was becoming narrow, respectively. Mathematical interpretation of pearlite growth rate was developed that gives true changing behavior of pearlite growth rate with the varying cooling rate. Present study provides direct observation and unique quantitative information of austenite and pearlite formation in CGHAZ in pearlite railway steel.