Rolling Of Low Carbon Steel Research Articles

Anisotropy of acoustic properties in thin-sheet rolled low-carbon manganese steel

Thin-sheet rolled low-carbon manganese steel 09G2S with a thickness of 0,8 mm which has strong property anisotropy due to texture and residual stresses, was experimentally studied using SH-wave with horizontal polarization and zero-order symmetric Lamb wave mode. The velocities of elastic wave propagation along the sheet were analyzed as their direction and polarization varied relative to the rolling direction in the range of angles from 0 to 180 degrees. The excitation and reception of normal waves in the sheet were carried out by piezoelectric transducers with dry point contact, providing tangential force application. The results of the research on the anisotropy of acoustic properties, X-ray structural analysis of residual stresses and inverse pole figures, and metallographic studies were obtained.

Microscopic Study of Surface Hardening by Grit Blasting on Hot Rolled Low Carbon Steel (SPHC)

Microscopic Study of Surface Hardening by Grit Blasting on Hot Rolled Low Carbon Steel (SPHC)

Effect of initial solidification characteristics on longitudinal crack formation in thin slab caster

ABSTRACT Longitudinal surface crack has been one of the serious problems of thin slab casting (TSC). The present study was undertaken to comprehend the characteristics of longitudinal facial crack (LFC) and minimise the same in hot rolled low carbon steel sheets produced through thin slab casting and rolling (TSCR). Macro-structural characteristics of solidified shell has been investigated and correlated with plant observations. The centre and edges of funnel region showed maximum propensity of LFCs. TSC solidification is initiated with fine columnar dendrites which gradually coarsened towards the slab centre. This has been attributed to the characteristics of liquid steel flow instability in the upper mould region. Meniscus flow instability may lead to non-uniform heat transfer besides mould flux entrapment in the solidifying shell. Examination revealed that the mould hot faces ware covered with brass containing voids and cracks. Brass formation was found to be the most prominent around the meniscus of the wide hot face, which gradually faded out towards the mould exit. Tramp elements (zinc and lead) in liquid steel were found to be responsible for harmful brass formation during casting. The present findings were implemented in plant operation to minimise its concentration.

Effect of Carbon Content on Microstructure, Properties and Texture of Ultra-Thin Hot Rolled Strip Produced by Endless Roll Technology.

In order to make a comprehensive comparison between ultra-thin hot rolled low carbon steel (LC) and extra low carbon steel (ELC) produced by endless roll technology and explain the differences, a detailed investigation into the microstructural characterization, characteristics of cementite and precipitates, mechanical properties, internal friction peaks, texture characterization by an X-ray powder diffractometer and electron backscatter diffraction, and formability including earing behavior, hole expanding ratio and V-shaped bending properties was carried out with different carbon content for 1.0 mm thickness ultra-thin hot rolled strip produced in endless strip production line. The experimental results indicate that the microstructure of both is composed of multi-layer areas with different grain sizes and thicknesses, the strength and elongation of LC are higher than that of ELC, but the content of solid solution carbon atoms and r of ELC are higher than that of LC, at the same time, the formability of ultra-thin strip ELC is better than that of LC mainly related to the content of {hkl} <110> and {111} <112> of ELC was higher than those of LC. The mechanical and formability properties of ultra-thin hot rolled strip by endless roll technology can meet the requirements of replacement cold rolled strip by hot rolled strip.

Effect of Nb on the Austenite Microstructural Homogeneity of Hot Rolled Rebars

While the role of Nb in flat rolling of low carbon steels has been investigated in many works, the information about the use of Nb in rebar rolling of higher carbon grades is more limited. Rebar rolling presents differences relative to flat rolling that can affect the role of Nb, such as the application of higher number of rolling passes, higher strain rates, lower interpass times, and, consequently, enhanced adiabatic heating. Increasing the number of passes can contribute to austenite grain refinement. However, the high finishing temperatures in rebar rolling can lead also to significant austenite grain growth and microstructural heterogeneity development before phase transformation. This phenomenon will directly influence the final grain size and can also lead to the appearance of second hard phases in the final product. One of the options to avoid austenite grain growth is to add microalloying elements that retard grain growth kinetics, either in solid solution or as precipitates. This can open new roles for the application of Nb in rebar rolling. To analyze this, in this work laboratory torsion tests were performed with two 0.2%C steels microalloyed with two different Nb contents (0.029% and 0.015%). Soaking temperatures from 1100°C to 1250°C were applied to obtain different amounts of Nb in solid solution before grain growth study. The study shows that not only finish rolling temperature and cooling time, but also reheating temperature and the amount of Nb remaining in the form of undissolved precipitates are important factors controlling austenite grain growth.

Effect of strain and deformation mode on cube texture formation in warm bi-axial rolled low-carbon steel

Cube texture extensively influences the physical and mechanical properties of materials, but the {100}<001> cube texture scarcely occurs in body-centered cubic metals as deformed state. The cube texture formation in low carbon steel bars processed via 24-pass warm bi-axial rolling (WBR) was confirmed. The cube texture was observed in the area from the center to the quarter in the 13 mm rolled square bar, and it disappeared near the surface. In the present study, the cube texture formation was studied from the viewpoint of strain and deformation mode through finite element analysis (FEA). An equivalent strain, εeq, accumulated, and strain components inside a bar during 24-pass rolling were quantified by using FEA. The εeq was efficiently accumulated in the center and it was more than twice as large as the nominal strain calculated from shape change. The area from the center to the quarter was alternately compressed from two directions under the simple compressive mode. On the other hand, the surface area was compressed under the plane strain mode and shear deformation. Consequently, the bi-axial simple compressive mode brings out cube texture. These quantitative strain and deformation mode analyses would be useful for creating materials with cube orientation.

Experience of Rolling Patterns with an Inverse Temperature Wedge on the NShSGP 2000 Continuous Wide-Strip Hot-Rolling Mill

This article discusses possible approaches to increase the capacity of a finishing train using strip rolling with an inverse temperature wedge. One calendar year of operation of a continuous wide-strip hot-rolling mill (NShSGP) is considered. Analysis of plant data demonstrated that the rolling time is by 7–10% lower in the case of rolling with an inverse temperature wedge, which allows increasing overall mill capacity. The obtained results can be applied during rolling of low carbon steels for cold pressing, and their fraction in mill production prevails; thus, it is possible to significantly increase mill capacity without making additional capital investments.

Effect of Barkhausen Detection Distance in Cold and Temper Rolled Low Carbon Steels: A Novel Approach

In this paper, a novel arrangement for magnetic Barkhausen noise detection is introduced. Measurements have been performed using two low carbon steel plates of 1 mm thickness. The measurements were conducted along the rolling and the transverse directions. The new arrangement includes a displacement of the detection coil in predetermined steps in while the magnetizing yoke is kept stationary introducing a cyclic magnetization in the rolling direction and transverse to it. In general, the intensity of the Barkhausen signals decreased as a function of coil displacement in both plates. In the temper rolled plate, Barkhausen noise profile shape changed from a single peak to a double peak one when coil has been displaced by 5 mm away in both magnetizing directions. Peaks are more apparent while magnetizing in the transverse direction. The appearance of two peaks profile in the temper rolled plate may be attributed to two stages of magnetization taking place at different times as a function of the applied field. Magnetization in the transverse direction results in a partition of the internal magnetizations into two main components perpendicular to each other. The internal components of magnetization involve the magnetic easy axes in the rolling direction and the forced magnetization in the transverse direction due to the applied field. Another assumption to interpret the findings may be due to the internal demagnetization field in the soft material below surface. The findings support this assumption in such a way that the demagnetizing field is strong enough in the transverse direction than in the rolling direction. This assumption is supported by the experiment on cold rolled plate. In the cold rolled plate, the resultant MBN profiles are composed of one peak throughout the test due to high dislocation density and hence a very weak demagnetizing field.

Austenite transformation simulation for a controlled rolling processing technology development

Abstract Using an originally-developed computer model and appropriate software the impact of deformation on austenite phase transformation in low carbon alloyed steel was carried out. The computer simulation takes into account an impact of the deformation degree and takes into account non-constant cooling rate. That makes it useful for the development of thermal and deformation technological processes development. Based on the simulation results a technology of controlled rolling of low carbon steel alloyed by carbide forming elements (Nb, V, Ti) was developed. The proposed technique allows production of rolled steel sheets with high strength and plastic properties, as well as high impact strength in normal and low temperatures.

Optimization of Multiple Performance Characteristics of Cold rolling Processes Using Taguchi’s Quality Loss Function

The single stand cold rolling mills are generally called as reversing mills, whereby the metal strip is successively wound and unwound in the form of coil as it is repeatedly passed back and forth through the one mill stand. Rolling Pass schedule consists of setting of control parameters at each pass depending on various factor like input and output thickness, width of the coil, material to be rolled, mill capability etc. Majority Quality related problem faced by cold rolled producers using single stand cold rolling are strip thickness variation and strip flatness, also they are concerned about power consumption and production rate. This happens because there is no standard pass schedule available which can predict these Performance parameters. The operator uses thumb rule to make pass schedule. There is no Theoretical model available for such complex cold rolling process. Experimental Model using Taguchi based Single Optimization Method can improve the quality and process performance of the Mill. The main objective of this paper is to show the capability of the Taguchi Quality loss function based multi response optimization methods in increasing productivity of cold rolling process while controlling the Quality and cost of Production. The proposed methodology is used to optimize Multi process performance namely thickness variation, strip flatness, production rate and Power consumption by obtaining optimal solution for control factors exit tension, entry tension, Mill speed and Roll bending pressure for cold rolling of low carbon steel in single stand reversible cold rolling mill. A L_27 orthogonal array was selected and total 27 experiments were conducted after selecting control factors and its levels. Interaction plot shows no interaction among the control parameters. The ANOVA carried out which shows the mill speed is most significant control factor. The optimal values obtained using the multi characteristics optimization Model using Taguchi loss function has been validated by confirmation experiment.

Improvement of strength and toughness for hot rolled low-carbon bainitic steel via grain refinement and crystallographic texture

Low-carbon bainitic steel with effective grain size of ~2.0µm and strong <110>//RD (rolling direction) transformation texture was obtained by adopting ultra fast cooling following non-recrystallization rolling. The steel exhibited higher tensile strength of ~840MPa and lower ductile-to-brittle transition temperature of ~−106°C in comparison with the steel that had no distinct texture with effective grain size of ~4.5µm. High intensity of {110} planes normal to the rolling direction were formed as a result of the strong {114}~{223}<110> transformation texture and effectively inhibited the main crack propagation by ductile fracture mechanism. The existing {100} planes parallel to the rolling plane led to the impact fracture delamination at −20~−100°C, which improved the low temperature toughness.

Numerical and experimental investigations into strain distribution and metal flow of low carbon steel in cold ring rolling

Strain distribution of cold ring rolling has been proven to be inhomogeneous in published literatures. However, divergence emerges from those numerical and experimental results concerning strain levels throughout ring thickness. One reason for this is that most of the results were obtained under different experimental conditions such as die geometry and processing parameters. Thus, to achieve a reliable explanation for the strain distribution of the ring is of great importance. For this task, numerical simulation and experimental procedures of cold ring rolling of low carbon steel are performed in the current work on the condition that the parameter configuration of the two is identical. In doing so, a comparison of simulation with experiment is provided to help explain the strain distribution of the ring. The numerical simulation shows good agreement with the experimental results. A higher level of plastic deformation exists in the outer surface of the ring, which is revealed in both the simulation and the experiment. Furthermore, microstructure observation is introduced to determine the metal flow in cold ring rolling from a new angle of microscale. Aligning at smaller angles with rolling direction, lamellar colonies in the outer surface of the ring exhibit relatively finer morphologies than those in the inner surface, indicating circumferential material flow of a higher level in that region.

Prediction of Mechanical Properties of Low Carbon Steel in Hot Rolling Process Using Artificial Neural Network Model

This work deals with the prediction of mechanical properties of hot rolled steel slab in the hot rolling mill to avoid the manual working of preparing tension test samples in the mechanical testing lab. The time consumption for testing is avoided and the cost of product is decreased.A model for predicting mechanical properties of low carbon steel has been developed and Feed Forward Back Propagation (FFBP) as one type of algorithm of the Artificial Neural Network has been applied to the prediction system. Yield strength (YS), Ultimate tensile strength (UTS) and Elongation(EL) are the basic mechanical properties of low carbon steel are predicted as a function of thermo-mechanical process parameters. These properties mainly depend on the input parameters such as Dispatch Temperature (DISTEMP), Transfer-Bar/Rolling Temperature (TBART), Finishing Temperature (FINT), Coiling Temperature (COILT) and Carbon Equivalent (CEQ). The FFBP is a supervised system that requires a lot of input and output data pairs for training process. The data are acquired from Indian Public Sector Steel Company and preprocessed before training.Performance of the model is evaluated by the Normalized Root Mean Square Error (NRMSE) and the Coefficient of Correlation (R). The NRMSE and the R values of both training and validation parts show excellent values. Therefore, the model using the FFBP algorithm is appropriate to predict the mechanical properties of the hot rolled low carbon steel.

Kinetics of static strain aging after temper rolling of low carbon steel

In this study, static strain aging behaviour of cold rolled steel strips was considered with emphasis on the distribution of residual hydrostatic stress developed during temper rolling. In order to assess residual stress distribution produced by the temper rolling, a three-dimensional model was first employed. Then, samples were rolled at a reduction of 4% under single and double pass rolling programmes and the kinetics of static strain aging phenomenon as well as the required activation energies were then evaluated using hardness and tensile tests on the deformed samples. Considering the predicted residual hydrostatic stress distribution, it was found that tensile hydrostatic stresses promote the kinetics of the static strain aging process and alter the activation energy required for the phenomenon. In addition, it was revealed that different positions of the rolled steel show different aging behaviour owing to non-uniform distribution of residual stresses after temper rolling.

Research on Characteristics of Deposition Precipitation Process in Production of Low Carbon Aluminum-Killed Steel in FTSR Technology

Precipitation characteristics of second phase in low-carbon steel produced by FTSR technology have been researched by TEM and EDS in this article. And preliminary research of precipitation conditions of second phase particles in thermodynamics and dynamics have been took. The results indicate that: there’re second phase particles precipitated dispersively in hot rolled low-carbon steels by FTSR technology. These particles mainly contain particles of Al2O3, MnS and AlN, and the precipitate size is about tens to hundreds of nano. Thermodynamical analysis declares that most of the Al2O3 and all of the MnS, AlN particles are precipitated in solid state. That’s why the precipitation process is slowed down by the diffusion velocity of the elements in solid, and thinner particles are precipitated while the material is in solid state than in liquid state. Different from the traditional plate rolling production of Al-killed steel, the precipitation of AlN particles are mainly controlled by the continuous casting process in thin slab casting and rolling process, but almost no precipitation of AlN particles in the rolling process.

Grain refinement and mechanical properties of asymmetrically rolled low carbon steel

The formation of fine ferrite grains by the asymmetric rolling of low carbon steel and their mechanical properties were studied. Super-cooled low carbon austenite was deformed by asymmetric rolling at 750 °C with a roll size ratio of 1.5 and immediately cooled at various cooling rates ranging from 3 °C/s to 15 °C/s. Fine ferrite grains (∼2 μm) were formed after asymmetric rolling, preferentially at the prior austenite grain boundaries. The volume fraction of the fine ferrite grains increased with increasing rolling reduction. A ferrite plus pearlite microstructure was obtained at smaller strains and slower cooling rates. However, after heavy deformation, a fine ferrite grain structure with carbide particles dispersed at the ferrite grain boundaries was obtained and the pearlite structure was not observed even after very slow cooling, which implies that most of the ferrite grains were formed dynamically, i.e. during deformation. The yield strength of the asymmetrically rolled steel plates increased with increasing deformation; however, the yield ratio also increased with increasing rolling reduction. The best combination of strength and yield ratio was obtained by using a low level of deformation and a high cooling rate, in which case a portion of the untransformed austenite transformed to martensite.

Effects of inclusion and loading direction on the fatigue behavior of hot rolled low carbon steel

The anisotropic fatigue behaviors of hot rolled low carbon steel were investigated for specimens with different angles between the loading and rolling direction. It was found that with the increase of loading angles crack initiation site changed from the matrix of surface to internal inclusions (either alumina or MnS) and fatigue strength decreased significantly. The large difference of the projected area of inclusions was responsible for this anisotropic fatigue strength. A good linear relationship between inclusion area and fatigue life in log–log plot was found. The fatigue limits can be predicted by empirical equation and a modified Murakami’s model.

Aging Behaviour in Hot‐Rolled Low Carbon Steels

Lüders strain and aging index were employed to characterize the aging properties of hot rolled low carbon steels during production. The Lüders strain was found to increase with aging time while the aging index decreased. It is interpreted that the aging index represents the susceptibility of steels to aging, while the Lüders strain measures the effects of carbon and nitrogen atmosphere pinning on dislocations. By comparing accelerated aging with room temperature aging behaviours of low carbon steels for up to two years, an algorithm deriving the activation energy of solute carbon and nitrogen migration from aging property measurements was proposed. The equation derived for accelerated aging of hot‐rolled low carbon steels investigated was in reasonable agreement with that reported in the literature.

Effect of O2 in Heating Atmosphere on Hydraulic Descaling in Hot Rolling of Low Carbon Steel

Low carbon steel was oxidized over the temperature range 1050–1250°C in O2–CO2–H2O–N2 gas mixtures. The oxidation times were 15–120 min, and the scales were 130–2000 μm thick. The experimental parameters were chosen to approximate scale formation under conditions similar to those of reheating furnaces in hot strip mills. In the hydraulic descaling tests, two modes of scale removal were observed. In the first mode, observed in classical three-layer scales that developed an inner porous layer with low or medium porosity, the horizontal undercutting occurred at the boundary of the inner porous layer and dense scale. The second mode was observed in classical three-layer scales that developed an inner porous layer with high porosity, and in crystalline scales. In the second mode, the horizontal undercutting occurred at the first plane of large pores relative to the scale/steel interface. A rise in the concentration of free oxygen resulted in an increase in thickness of the residual scale at 1050°C. At 1100°C and 1150°C, the increase in residual scale thickness with increasing free oxygen was significant in the initial 60 min of oxidation; after this period of time the differences in the thickness of the residual scale became smaller. At higher temperatures, the influence of free oxygen in the residual scale thickness was small at 1200°C and negligible at 1250°C. In general, the experiments showed that scale morphology controlled the removability of scale.

Influence of process parameters on scale reduction with H2

A new pickling method that reduces the metal oxide on steel strip using H2 has been studied through an extensive campaign of experimental tests. The process, referred to as 'acid free pickling', is environmentally friendly and does not use acid. It is most suitable for application to hot rolled low carbon steel strip. Experimental studies are in progress to validate the application of hydrogen on different metals.