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Severe weld porosity has led the industry to believe that die-cast magnesium alloys cannot be fusion welded. To address this challenge, a new process of ultrasonic vibration coupled with hot rolling was employed to eliminate porosity, and the mechanism associated with weld porosity in die-cast magnesium alloys was analyzed in detail. Unlike conventional welding processes, ultrasonic vibration coupled with hot rolling is effective and efficient. In this study, a roller with ultrasonic vibrations is synchronized with the molten pool to apply pressure to the weld, which is in a semi-solid state on the upper surface. The results showed that hot rolling and ultrasonic vibration coupled with hot rolling could eliminate 78.12 % and 85.5 % of the porosity, respectively. Compared to hot rolling, the ultrasonic vibration coupled with the hot rolling process resulted in smaller and fewer porosities and finer β-Mg 17 Al 12. This is attributed to the cavitation effect of ultrasonic vibration that promotes bubble overflow and breaks the β-Mg 17 Al 12 dendrites in the melt pool, as well as the thermal effect that improves the plasticity of the weld. Furthermore, after closing the porosity under pressure, recrystallized grains will be produced around it. Tensile test results indicated that hot rolling was able to increase the ultimate tensile strength by 84.21 % and elongation by 44.03, whereas ultrasonic vibration coupled with hot rolling was able to increase the ultimate tensile strength by 244.46 % and elongation by 71.70 %. Combining the micron-scale industrial computed tomography results with theoretical calculations, it is found that the porosity of die-cast magnesium alloys is mainly caused by nitrogen, and they originate from gas entrapment during the die-casting process; further, the formation mechanism of die-cast magnesium alloys' fusion-welding porosity is revealed in detail. A physical model of the formation process of welded porosity morphology was established, and the analysis suggested that the pattern of the inner wall of the porosity was related to the Kelvin–Helmholtz instability. This research is expected to improve the weld quality of alloys manufactured by the die-casting process. [Display omitted] • Proposed ultrasonic-vibration-coupled with hot-rolling reduces pore content by 85.51 %. • Ultrasonic-vibration-coupled with hot-rolling increases ultimate tensile strength by 244.46 % and elongation by 71.70 %. • The controversy of "the type of gas that causes porosity" has been resolved. • A complete mechanism for die-cast magnesium alloy weld porosity was proposed. • We explored common class of pore morphologies in metals to suggest physical models. [ABSTRACT FROM AUTHOR]

Aluminum alloy heterogeneous plate has great potential applications in automotive, military, aerospace, and other fields due to its excellent mechanical properties and ability to resist ballistic missile penetration. In the present work, a 5356/7A48 aluminum alloy heterogeneous plate with high strength-ductility and excellent interfacial metallurgical bonding strength was prepared using wire-arc additive manufacturing and hot rolling (WAAM+HR) process. The yield strength and ultimate tensile strength were 280.2 MPa and 392.3 MPa, respectively, both of which were between 5356 and 7A48 alloys, but the elongation was excellent, up to 22%. Its excellent comprehensive mechanical properties far exceed those of Al/Al heterogeneous plates reported in previous studies. In addition, compared with traditional clad plates, its fracture displacement is improved by 48.8%, showing remarkably high interlayer bonding strength. The soft layer 5356 and the hard layer 7A48 beared the main plastic strain and normal stress respectively, resulting in back-stress strengthening at the interlayer interface, which was the fundamental reason for the synergistic effect of strength and plasticity. Furthermore, even at the maximum bending angle of 180°, the heterogeneous plate did not show any sign of fracture, thanks to the fact that the outer soft-clad layer accommodated most of the bending deformation. The heterogeneous lamella structure, high constraint of hard layer to soft layer, and high geometrically necessary dislocations (GNDs) density of interfaces effectively stimulated the back stress strengthening and dislocation hardening, so that the 5356/7A48 aluminum alloy heterogeneous plate exhibited excellent comprehensive mechanical properties. The proposed WAAM+HR process provides an approach for the preparation of multi-functional heterogeneous plates with high strength-ductility and superior bonding strength. [Display omitted] • High strength-ductility aluminum alloy heterogeneous plates were fabricated via wire arc additive manufacturing and hot rolling. • The aluminum alloy heterogeneous plates exhibit heterogeneous lamella structure and excellent mechanical properties. • The inconsistent plastic deformation at the interface caused synergistic enhancement of the strength and ductility. • The soft clad layer accommodates most of the bending strain, enhancing the fracture resistance of the heterogeneous plate. [ABSTRACT FROM AUTHOR]

The present investigation finds the effect of electropulsing treatment on the mechanisms of refining and reprecipitation of ordered L2 0 structure (B2) and its impact on tensile properties of low-density duplex steel of Fe-18Mn-10.5Al-1 C-6Ni composition. The selected composition without manganese is melted at 1600°C by induction heating in a vacuum but Mn is added into the melt at 1560°C, in the argon atmosphere to reduce the loss. The melt is cast into a plate form in a copper mold. The cast steel is homogenized, hot rolled, and annealed (PD1-A sample) to get elongated bands, spheroids, and platelets of B2 phase with an austenitic matrix which results in a yield strength of 1015 MPa, and tensile strength of 1285 MPa with a plastic elongation of 16.3%. Electropulsing partially dissolves the B2 phase at a temperature much lower than the equilibrium solvus by reducing barrier energy because of electron wind. As a result, the sizes of bands and spheroids are reduced, and platelets are disintegrated. Electron wind force deforms coarse precipitates, and fragments as well as spheroidized it. Electropulsing of annealed steel (PD1-AE) mobilizes dislocations, and recovers it in B2, but induces localized recrystallization of austenite. At a later time of the signal, the temperature rapidly falls and the matrix becomes supersaturated but electropulsing accelerates low-temperature precipitation of the B2 phase. Therefore, electropulsing can be adopted as a fast manufacturing process to dissolve, deform, fragment, spheroidize and reprecipitate high temperature phase at much lower temperature by dominant athermal effect of electron wind energy over thermal effect. Electropulsing also induces recovery and recrystallization at a relatively low temperature and reduces defect density. Reduction in the overall size of B2 and its distribution towards better uniformity provided an increased yield strength of 1077 MPa, tensile strength of 1355 MPa, and a plastic elongation of 21.6%. The selected duplex low-density steel follows two-stage work hardening of Ludwigson model with an additional stage of dynamic recovery. Fractography analysis confirms that both samples show mixed modes of ductile and brittle fracture, with an increase in size and area percentage of dimples. [Display omitted] • Major changes in microstructure are resulted from the electron wind energy. • Electropulsing (EP) dissolves ordered L2 0 (B2) phase at lower than solvus temperature. • EP deforms, fragments and refines existing B2 and accelerates precipitation of it. • EP partially recrystallizes austenite and recovers as well as spheroidizes B2. • Improvement in tensile properties by the refinement, and redistribution of phases. [ABSTRACT FROM AUTHOR]

Edge crack formed during the hot rolling process significantly affected the quality of high-grade non-oriented electrical steel (NOES), posing substantial challenges to production. This study investigated the formation mechanism of serrated edge cracks in hot rolled strip, characterized by unusually coarse strip-like grains with typical thicknesses ranging from 0.5 to 0.8 mm and lengths ranging from 10 to 15 mm. These coarse strip-like grains evolved from abnormal columnar grains at the edges of reheating slab. During the continuous casting process, the bulge phenomenon occurred easily in high-grade NOES slabs, due to its lower yield strength at high temperatures. This bulge induced high internal stress at the slab edge, leading to abnormal growth of the columnar grains during the slab reheating process at high temperature. The orientation of coarse grains gradually changed to a rotated cube texture ({100}<011>) throughout the hot rolling process. These grains with rotated cube texture exhibited fewer slip systems and lower deformation storage energy, which is not conducive to the plastic deformation in thickness direction. Consequently, coarse grains at the slab edge deformed along TD direction and overflowed towards the lower surface of hot rolled strip, resulting in the original edge boundary enveloped by the overflowed metal to generate crack source. Finally, the serrated edge crack was formed from crack source under tensile stress during finish hot rolling. [Display omitted] • The interaction between serrated edge crack and the abnormal coarse strip-like grain microstructure was considered. • The abnormal coarse strip-like grain evolution process has been investigated. • The formation mechanism of serrated edge crack has been established. [ABSTRACT FROM AUTHOR]

Abstract Surface defects on metal strips can be generated during hot rolling from surface cavities and indents. The size and aspect ratio of the initial surface cavities present before rolling are critical parameters that determine the final configuration of the defect. The propagation of these defect through the full rolling process is detrimental to the surface quality of the end product, in particular for electrical steel where these type of defects may directly affect the magnetic properties of the final product. A finite element model was developed in the present research to simulate the evolution of surface defects in a high-silicon electrical steel subjected to a single pass hot-rolling operation. The surface defects were modelled as predefined cavities with various aspect ratios and a multi-scale approach was used to capture the large local deformation gradients at the vicinity of the initial cavities. A user-defined subroutine was developed to describe the material constitutive behaviour at different strain rates and temperatures based on the Sellars-Tegart model in ABAQUS/standard finite element package. The modelling results were validated by laboratory scale hot rolling experiments with respect to the measured rolling forces and the plastic deformation of the initial cavities. This study shows that buckling of the lateral sides and bulging of the floor of the initial cavities are the main mechanisms involved in the formation of sub-surface defects. The developed model can be used to predict the evolution of surface cavities and to optimise the rolling parameters in order to minimise the detrimental effect of these defects in the final stages of the hot rolling process. [ABSTRACT FROM AUTHOR]

Abstract The effect of stress release on the shape and deformation of strip between stands are rarely considered or quantified in the traditional strip shape model. In order to make up this deficiency, a high precision shape model is established by the mechanism of the strip shape forming and the deformation of roll system in this paper. Special concentration is placed on the effect of roll wear, roll thermal expansion, metal transverse flow and stress release on the shape. In addition, a tolerance factor which is used to describe the attenuation and tolerance abilities of each stand for longitudinal strain difference is proposed as a foundation for a presetting strategy. Compared to the traditional presetting strategies using the empirical coefficient or Shohet theory, the presetting strategy on the basis of the tolerance factor can better play the control ability of each stand. A systematical description of the presetting strategy and the modeling process of the high precision shape model is given in the present study. The calculated results agree well with experiments, and the actual production data show that the shape model has satisfactory accuracy. [ABSTRACT FROM AUTHOR]

In this paper, oil-in-water (O/W) based nanolubricants containing TiO 2 nanoparticles were developed to reduce the rolling force and improve the surface quality of rolled 304 stainless steel product. Practical hot rolling tests with and without application of lubricant were conducted to systematically investigate the effects of the developed O/W based nanolubricants on the rolling force, surface roughness, oxide scale thickness and tribological behaviour. The obtained results indicate that the nanoparticles can enter the deform zone with oil droplets to take a lubrication effect. The optimal lubrication effect can be achieved when the O/W (1% oil mass fraction) based nanolubricant with a TiO 2 mass fraction of 1.5% was applied. The microstructure of oxide scales formed on the hot rolled sample was not significantly affected by TiO 2 nanoparticles in the O/W based lubricant, but the oxide scale growth could be induced by TiO 2 nanoparticles. A discontinuous thin SiO 2 layer at the substrate-scale interface was observed. It can effectively reduce the formation of iron-rich oxides. The novel nanolubricant has a great potential to be applied in the hot steel rolling, to realise the cost-effective and environmental-friendly manufacturing process. [ABSTRACT FROM AUTHOR]

This work aimed to alter the texture components and enhance the stretch formability of rolled AZ31 sheets by developing the rolling technology. In this study, a continuous bending channel was introduced into an equal channel angular rolling apparatus and a new rolling technology was successfully developed. Microstructure evolutions during hot-rolling, equal channel angular rolling and subsequent continuous bending were investigated. Results showed that hot-rolling generated a strong basal texture component. Single pass equal channel angular rolling cannot eliminate the basal texture component, while can greatly weaken basal texture intensity. After continuous bending, basal texture component was almost eliminated. Meanwhile, a strong c-axis//RD texture component and a weak double-peak texture component with symmetrical splitting of the {0002} basal texture were formed. After recrystallization annealing, symmetrical double-peak texture whose {0002} pole peak located at about 40° from normal direction towards the rolling direction was enhanced with the disappearance of c-axis//RD texture. The AZ31 sheets with double-peak texture exhibited excellent stretch formability at room temperature (with an Erichsen value of 7.4 mm). Finally, the relevant mechanisms were discussed. [ABSTRACT FROM AUTHOR]

Casting metal products are characterized by undesired void defects due to the shrinkage occurring during the solidification of molten material. In order to deliver safe and sound components satisfying the customer requirements, these defects need to be reduced or if possible eliminated. Hot metal forming processes can be used for this purpose therefore, the calibration of their parameters is a fundamental task. In this paper a study of the void closure during hot rolling of 316L stainless steel slabs coming from continuous casting has been conducted. The effects of the hot rolling main parameters (i.e. percentage of reduction, cooling time, and side of reduction) on void closure index have been investigated by means of FE analysis. Data coming from experimental tests performed by Cogne Acciai Speciali S.p.a. were utilised to validate the model and the research results. A correlation between void closure indexes and the residual voids along the hot rolled slabs axis was found for AISI 316L stainless steel. Moreover, new geometric indexes depending on the rolling parameters were defined. Also in this case a correlation between these new indexes and the void closure was found. [ABSTRACT FROM AUTHOR]

A new model was proposed based on the dislocation density of the computer simulation of the microstructure evolution in magnesium alloys. It is possible to describe the continuous dynamic recrystallization (CDRX) interaction including work-hardening, dynamic recrystallization (DRX) and dynamic recovery (DRV) changing with rolling time. The transient hot rolling simulation was performed by implementing this model under various rolling temperatures and strain conditions using the finite diffraction method (FDM). Normal rolling experiments were conducted at different reductions and starting rolling temperatures. Microstructural parameters, such as grain size, subgrain size, misorientation angle, high-angle grain boundary (HAGB), and low-angle grain boundary (LAGB), were measured using electron back-scattering diffraction (EBSD). The dislocation density of LAGB and the hypothetical dislocation density of HAGB were estimated through theoretical derivation using the experimental data. As a result, changes in the hypothetical dislocation density of HAGB and the dislocation density of LAGB of the model prediction fit well with the experimental data. The microstructure evolution mechanisms of the AZ31 magnesium alloy in the roll bite were examined at 300, 400 and 500 °C rolling. As a result, it is clear that the work-hardening is a dominated mechanism of 300 °C rolling in the rolling strain ranging from 0 to 0.6. However, the DRV plays a vital role in the microstructure evolution at 400 and 500 °C rolling. [ABSTRACT FROM AUTHOR]

Surface defects on metal strip products can have their root cause created in the hot rolling process by cavities and indents entrapped scale. The initial size and aspect ratio of surface features are critical parameters that determine whether they will be eliminated by the rolling process. The present research investigates the effects of the initial cavity geometry and the evolution mechanisms in a single hot rolling pass for a high-silicon electrical steel substrate. Laboratory hot-rolling experiments were carried out on blocks with open cavities of different geometries machined into the surface. The final geometry of the longitudinal and transversal profiles of the deformed cavities was analysed from metallurgical cross-sections. For a given initial cavity width, the width of the resulting oxide-filled defect is inversely related to the initial depth of the machined cavity. It has also been observed that the depth of defects increases linearly with the original depth to width aspect ratio of the initial cavities. Cavities with a depth of less than 1 mm essentially disappeared after the rolling. The final length is only dependent on its initial length in the rolling direction. The percentage reduction of cross-sectional area of the defects is found to increase with the initial depth and width of the cavities. [ABSTRACT FROM AUTHOR]

The advantages of stainless steel/carbon steel clad plates include corrosion resistance, low cost, good ductility, etc., which are usually used as chief load-bearing components. But the low bonding strength and bearing capacity of clad plates severely limit their wide application. 316 L/Q235B/ 316 L clad plates are prepared by the longitudinal corrugated rolling (LCR) method. The deformation characteristic, mechanical property and microstructure evolution of the LCR plates are investigated by combining finite element method (FEM) and experiments. The effects of LCR and traditional flat rolling (FR) processes on the performance of clad plates are compared and analyzed. The results show that the LCR plates' shear strength is increased up to 14%, 16% and 19% at the peak, waist and trough, and the tensile and bending strengths of LCR plates are increased by 7.1% and 16.2% compared with FR plates, respectively. The grains are equiaxed at the peak and lamellar at the trough in the 316 L layer in the LCR process. The grains are equiaxed at the peak and trough of LCR plates in the Q235B layer in the LCR process. The deformation mechanisms of the LCR and FR processes are illustrated according to FEM results. The grain state and metal flow of LCR plates can be changed by the fluctuant effective strain and temperature distributions caused by the special roll shape. In the LCR process, the opposite shear stresses in the rolling direction (RD) and the transverse direction (TD) can form cross shear zones, which improves the clad plates' bonding strength. [ABSTRACT FROM AUTHOR]

Tensile armor is usually made of flat pearlitic steel wires and produced in a manufacturing sequence as follows: hot-rolling → patenting treatment (PT) → cold forming → wire coiling → stress relief → re-winding wire process. To evaluate the effect of the key parameters in this set of processes on the microstructure, microtexture, and crack susceptibility in commercial pearlitic steel, four process routes were lab-simulated with different setups of 45% hot-rolling, PT, and 65% cold-rolling. Subsequently, the cold-rolled specimens produced through the four distinct routes underwent two stress relief treatments (at 400 and 700 °C for 60 s), succeeded by simulation of the re-winding wire process via four alternated three-point bending procedures. Scanning electron microscope images, microhardness, and electron backscattered diffraction techniques were extensively performed in this work. Due to pearlitic block size control, the PT influenced the {111}< 112 > component formation during the cold-rolling process. During the bending experiments, cracks were detected just in the route with the highest cold-rolled {111}< 112 > microtexture orientation followed by stress relief at 700 °C. This crack susceptibility was related to the small recrystallized grains nucleated in the shear bands of the {111}< 112 > pearlitic blocks during the stress relief treatment. • Patenting treatment can change pearlitic block size, colony size, interlamellar spacing, microtexture, and microhardness. • Pearlitic block size affects the intensity of the {111}< 112 > microtexture component formed during the cold-rolling process. • Stress relief at 700 °C for 60 s can produce small recrystallized grains inside 65% cold-rolled {111}< 112 > pearlitic blocks. • Small recrystallized grains inside {111}< 112 > pearlitic blocks are prone to crack nucleation during bending deformation. [ABSTRACT FROM AUTHOR]

The strip flatness is a crucial index determining product quality in the strip tandem cold rolling (SCR). Data-driven methods (DDM) for flatness prediction are able to capture the uncertainties and nonlinearities in SCR compared with traditional analytical method and numerical simulation methods. However, they only depend on the industrial data during SCR, which restricts the adaptability and precision, especially for the strip head-end part, when the incoming state of hot rolled strip fluctuates violently. To break the restrictions, a novel paradigm of flatness prediction and optimization for SCR is proposed in this study based on a cloud-edge collaboration platform. The platform is designed to reasonably allocate computing tasks to achieve real-time optimization of flatness, and to provide an intact dataset by collecting the industrial data with heterogeneous interfaces and data types from SCR and strip tandem hot rolling (SHR) production line; an artificial neural network algorithm optimized by an artificial bee colony algorithm (ABC-ANN) is proposed to predict the flatness; and feedforward feedback coordinated regulation (FFCR) method is established to optimize the flatness control. The results of a cause study on a 1420 mm SCR production line indicate that the new proposed mode is feasible and outperforms the traditional modes only involving the data in SCR, and it can accurately predict and optimize the flatness including the strip head-end part. [Display omitted] • Proposing an advanced machine learning model allows for predicting the whole length flatness of the strip. • Establishing a new flatness control mode overcomes the state fluctuation of incoming hot rolled strip. • Designing an industrial IoT platform eliminates "information islands" and implements the data-driven model in real-time. • The new paradigm for prediction and optimization flatness is successfully applied to a 1420 mm strip tandem cold rolling production line. [ABSTRACT FROM AUTHOR]

The present study aimed to investigate the microstructure, temperature and thermal stress evolution in a high speed steel (HSS) work roll under service conditions during the early stage of hot rolling. Microstructural observations revealed the formation of micro-voids at the work roll surface due to spalling of carbides at grain boundaries, which can act as initiation sites of cracks during further cyclic heating and cooling. A transient thermo-mechanical model predicted a maximum surface temperature of 580 °C during the first rolling revolution and a stable maximum temperature of about 630 °C with further rolling revolutions, and the results will be used as reference temperatures in future study on high temperature oxidation and wear mechanisms of HSS work roll materials under practical service conditions. No tensile thermal stress at the surface was observed during the early stage of the hot rolling process, which is significantly influenced by the work roll body temperature. The residual stress at work roll surface was compressive with magnitude of about 200 MPa as measured by X-ray diffraction technique. [ABSTRACT FROM AUTHOR]

The effect of work roll roughness on the surface/near-surface evolution of aluminum alloys during hot rolling was examined with the use of a rolling tribo-simulator. Work rolls made of steel alloy AISI 52100 with two different surface roughness (R a ) values, 0.1 μm and 1.1 μm, were used to hot roll Al-Mg alloy samples under similar laboratory conditions for one and ten passes. Surface features on both rolled samples included cracks, grooves, and rolling ridges, but shingles were only observed on the samples rolled with the rougher work roll. Near-surface damage was observed to increase with work roll roughness. Cross-sectional examinations revealed that transverse micro-cracks on the sample rolled with the smoother work roll extended to depths of 2.8 μm, while cracks were 3.2 μm in depth for the rougher work roll. In addition, the oxide-rich near-surface layers formed on the samples were thicker and more discontinuous for the rougher work roll. The oxide distribution in the transverse direction could be correlated to the size of the rolling ridges, which were larger for the samples rolled with the rougher work roll. A critical work roll surface roughness was proposed to influence the initiation of shingles on the aluminum alloy surfaces. The extent of the near-surface damage and the surface features formed on the rolled aluminum alloys were shown to be dependent on, but not limited to, the work roll surface topography. [ABSTRACT FROM AUTHOR]

Determining the exact relationships between rolling parameters and mechanical properties is important to predict and even control the mechanical properties of hot rolled Ti micro-alloyed steel products. In this paper, two data dimension reduction strategies, respectively guided by physical metallurgical (PM) principles and data-driven (DD) strategy were proposed to preprocess the high dimensional steel composition and rolling parameters, and a comprehensive set of machine learning (ML) models was developed to predict yield strength (YS) and elongation (EL) combined with the reconstructed inputs. The artificial neural network (ANN) with the inputs including dislocation density, fractions, and sizes of ferrite and TiC precipitate transferred by PM principle outperformed that with the inputs extracted low variance feature elimination (LVFE) and autoencoder (AE) algorithms. Based on the proposed model, the effects of alloying elements, rolling temperatures, and microstructures on mechanical properties were comprehensively analyzed. Also, the variations of microstructures and mechanical properties over the strip length were discussed, which were consistent with the measured results. [Display omitted] • PM-guided dimension reduction was proposed to transfer rolling parameters to microstructures. • The dimension reduction guided by PM performed better than that guided by DD methods with LVFE and AE. • The predicted effects of process and microstructures on YS and EL were consistent with experiments. • The predicted variations of YS and EL over strip length were consistent with measured results. [ABSTRACT FROM AUTHOR]

Ti/steel clad plates have good corrosion resistance and lower titanium cost. However, the low interfacial bond strength severely restricts their wide application. In this study, a new process is proposed for preparing Ti/steel clad plates with high bond strength by employing double-layered slab assembly and hot rolling. The effect of temperature on bond strength is systematically studied. The results show that the shear strength initially increases and then decreases with increasing temperature from 700 °C to 950 °C. The maximum strength value of 311 MPa is obtained at 850 °C with a reduction rate of 30 % in a single pass. The mechanism analysis shows that the bond strength is affected by temperature in terms of metal deformation, elemental diffusion and intermetallic compound (IMC) formation. In addition, the shear strength depends on different degrees of dislocation strengthening and recrystallization in the titanium matrix when the fracture is located at titanium matrix near the interface. Finally, a phenomenological prediction mechanism-based model is developed to describe the relationship between the temperature and the bond strength. This research can provide guidance for the hot rolling preparation of Ti/steel clad plates with high bond strength. [Display omitted] • Ti/steel plates were fabricated by double-layered slab assembly and hot rolling. • A superior bond strength of 311 MPa was obtained at 850 °C. • Microstructure evolution was characterized. • Bonding mechanism at different temperatures was analyzed. • A phenomenological prediction mechanism-based model was proposed. [ABSTRACT FROM AUTHOR]

Microstructural evolution during hot rolling, which is complex and unperceptive but has direct effects on rolling forces, determines the final microstructure and mechanical properties of steel products. In this paper, a comprehensive set of machine learning (ML) models was developed through rolling forces to reveal the evolutions of recrystallization and grain size of austenite, in which the grain size was estimated by considering the grain shape effect after each rolling pass. By using the backpropagation neural network (BPNN) and genetic algorithm (GA) combined with industrial data, the quantitative connections of parameters in the models for static recrystallization (SRX), meta-dynamic recrystallization (MDRX), and mean flow stress (MFS) were established with steel chemical compositions and deformation conditions. Through the machine learning (ML) approach, softening kinetics and rolling forces can be more accurately predicted than traditional models. Also, the recrystallization behavior and evolution of austenite grain size during hot rolling were analyzed by using the proposed ML models, which are consistent with experimental results. • A novel grain size estimation approach considering grain shape effects was proposed. • SRX kinetics for industrial hot rolling could be accurately calculated by BPNNs. • Parameters in MDRX kinetics and L-J model were fine-tuned with rolling forces. • Microstructural evolution revealed by ML was consistent with physical principles. [ABSTRACT FROM AUTHOR]

Void defects such as porosity, shrinkage, and the formation of gas cavities cannot be completely avoided during the casting process. One current method that improves the quality of these products is the use of a forging or rolling process. Further research on the evolution behavior of voids during processing is necessary. To this effect, the present study investigates the evolution behavior of a few different sizes of voids during the hot rolling process. Evolution behavior is analyzed by finite-element simulation and laboratory experimentation. Analysis focused on the stress field surrounding a void during the rolling process. Results showed that voids changed shape from spherical to ellipsoid, and as the rolling pass increased became smaller and more irregular. The upper and lower surfaces of the voids bonded together after the last rolling pass. Voids of varying size change shape in a similar manner, however, by analyzing their hydrostatic integration it was observed that smaller voids bond more readily than larger ones. The results demonstrate favorable agreement between experimental and simulated results. [ABSTRACT FROM AUTHOR]

For hot-rolled flat products major losses of steel are due to surface defects, which are caused by the quality of an incoming continuous cast slab. Each typical surface defect of a continuous cast slab if not detected and eliminated transforms into a surface defect of a rolled plate. One of the most critical problems of hot rolled plates is connected with the longitudinal surface cracks located at the distance up to 80 mm from the edges. This study covers the research and simulation of transformation of surface cracks into the edge defects of the hot-rolled plate by finite element method. It is shown that the mechanism of crack movement during plate rolling comes from inclination of front and tail faces of slab due to temperature gradient between top and bottom surfaces. To reduce the possibility of corner crack formation it is proposed to increase the temperature of the edge zone of the slab due to the rounding of edges or by induction heating. The results of the study will be useful for material saving during plate rolling. [ABSTRACT FROM AUTHOR]

In this study, a commercially available twin roll cast AZ31 Mg sheet was hot rolled at 400 °C to investigate the influence of rolling parameters (speed and percent thickness reduction) on microstructure, texture and mechanical properties. As compared to the twin roll cast condition, the microstructure of the successfully rolled materials was much finer and relatively less bimodal but contained profuse twinning and varying fractions of dynamically recrystallized grains. The extent of dynamic recrystallization (DRX) during rolling was found to be significantly influenced by percent thickness reduction. In the parameters investigated here, the rolling speed had a weak effect on DRX. The results showed that hot rolling strengthened the weak basal texture of the twin roll cast material and in addition to necklace grain formations at grain boundaries, DRX inside the twins was also identified as a key recrystallization mechanism. Mechanical testing revealed that at room temperature hot rolling improved the yield strength with retention of limited tensile ductility (<15%). However at 200 °C, the rolled material exhibited more a balanced mechanical properties with large tensile elongations. Microstructural analysis of the failed tensile tested specimens showed that the deformation behavior was dependent on grain size and crystallographic texture. [ABSTRACT FROM AUTHOR]

In multi-pass rolling processes such as plate rolling, accurate predictions of roll force and torque over all roll passes are desired, so that the pre-calculated roll pass schedule can be put into practice without exceeding the limits of the roll stand. In this context, the grain size has two roles; the final grain size determines the product properties, and the evolution of grain size influences the force predictions. Since the grain size predicted after each roll pass enters the recrystallization kinetics and grain size evolution equations of the subsequent pass, a feed-back loop for the grain size calculation is created, which may become unstable so that the computed roll force and grain size become very sensitive to small variations in the input parameters. Although models for the evolution of grain size in multi-stage hot rolling have been applied in the industry for decades, their mathematical stability has not been given much attention, which poses difficulties for force and grain size predictions in cases subject to partial recrystallization. In this paper, the stability of a common semi-empirical model for static recrystallization and grain growth is investigated. The conditions under which instabilities occur are analyzed both for an industrial plate rolling pass schedule and for idealized load cycles. It is shown that complete recrystallization between roll passes leads to a stable grain size evolution, and that some states of partial recrystallization are unstable and hence problematic for force and grain size predictions. Instabilities in force and grain size predictions of an industrial pass schedules are analyzed by computing sensitivities using automatic differentiation of the model, showing that large amplification factors may occur if the states of partial recrystallization are treated by average strains and grain sizes. The instabilities are an inherent property of the closed-form equations for microstructure evolution for some states of partial recrystallization. However, the side effects of the instabilities can be reduced if the microstructure is not represented by average values of grain size and accumulated strain but by substructures generated by partial recrystallization. This way, the accuracy of roll force predictions can be considerably improved. [ABSTRACT FROM AUTHOR]

[Display omitted] Interrupted in situ tests at high temperature characterized with X-ray microtomography were employed to study porosity evolution under loading conditions representative of aluminum hot rolling. Coupling digital volume correlation and simulations, it is possible to access, for each pore, its morphological evolution, and the mechanical fields it experienced. The closure kinetics of hundreds of pores were studied, which is described as the pore volume as a function of the hydrostatic integration. Closure kinetics are a function of the shape of the pore. Focus is put on pores with a complex shape which are more detrimental to mechanical properties. Their closure kinetics are exponential due to the pore fragmentation during closure. The closure of complex pores is fostered by an initial orientation perpendicular to the loading direction and a low initial fragmentation. Based on the closure kinetics of 243 complex pores, a new pore closure model is proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] Pores are often present in large aluminum ingots after casting. To ensure the mechanical reliability of the final thick plates, these pores must be closed during the forming process, hot rolling in the present case. This study aims at understanding the effects of rolling parameters on the volume evolution of pores. To do so, X-ray microtomography is used to track real casting pores during deformation. Nevertheless, thick plates are too large to enable a fine characterization of the evolution of pores during the process. The size and shape of the samples as well as the mechanical boundary conditions must be optimized to meet imaging constraints. This paper focuses on the reproduction of complex loading paths. Multi-scale FE simulations are used to reproduce the loading conditions of thick plate rolling with uniaxial tests on samples of a few millimeters. Uniaxial tests are then characterized with tomography on a synchrotron X-ray beamline. In each sample, tens of pores are individually tracked, giving access to their volume evolution. The local loading path experienced by each pore is determined with FE simulation. It is shown that the volume evolution of a real pore correlates with the hydrostatic integration which is the integral of stress triaxiality along cumulated strain. This confirms that the closure of complex casting pores is enhanced by a high relative reduction and high values of L / H ratio during rolling similarly to what was observed numerically on simpler shapes. [ABSTRACT FROM AUTHOR]

Abstract: The no-recrystallization temperature (T nr) is an important parameter in the design of two-stage rolling schedule to obtain finer grain size. T nr was obtained both by continuous cooling compression testing and tension-compression testing. However, due to the limitations of experimental installation, both compressing testing and tension-compression testing have a scaling down of practical pass strain and strain rate in rolling mill. The mathematical model that calculates mean flow stress (MFS) can eliminate these limitations and the pass strain and strain applied in mathematical model are approximately equal to the mean value of that in wire-rod rolling mill. Therefore, mathematical calculation is a new method to determine T nr and the predicted T nr is similar to experimental results. Due to the high strain rate and short interpass time at the finishing strain of wire rods mills, mathematical modeling is also an effective method to simulate microstructure-evolution in wire rods rolling. An expert system was established to study the microstructure evolution in two-stage rolling through the obtained dynamic recrystallization (DRX) model combined with metadynamic recrystallization (MRX) and static recrystallization (SRX) model in literature. In the present work, it is simplified that the complete metadynamic recrystallization (MRX) is achieved when strain for deformation exceeds critical strain ɛ c . It was found that strain accumulation played an important role in finishing rolling. The recrystallization behavior during finishing rolling stage was repeated by static and dynamic model. The predicted austenite grain size and mean flow stress at each pass are expected to provide guidance for appropriate rolling schedule design. [Copyright &y& Elsevier]

Abstract: SUS304 stainless steel and plain carbon steel were first bonded by hot rolling in an argon atmosphere and were subsequently hot-rolled by multiple passes in air. Shearing and peeling tests were performed according to appropriate standards to evaluate the bonding results. The interfacial microstructures, composition diffusion and peeling fractographies of the clad plate samples were used to examine the bond quality. The effects of bond parameters on the bond properties of clad plate were studied. The experimental results indicate that the shear strength reaches 266MPa, and the peel strength is up to 322N/mm at 1323K in the first pass, representing a reduction of 24.3%. Both the shear strength and the peel strength increase with increases in bonding temperature and total reduction ratio. The maximum shear strength reaches 361MPa, and the peel strength is up to 510N/mm at 1323K after six passes with a total reduction ratio of 74.8%. Both the dimension and number of interfacial pores decrease rapidly with increasing rolling passes. Multipass hot rolling generates a number of local embedments at the interface and improves the interfacial bonding strength. [Copyright &y& Elsevier]

Highlights: [•] The grain size effect on precipitation kinetics of nitrides has been investigated. [•] In hot rolled state the grain size effect is significant. [•] In cold rolled state the effect of grain boundaries on precipitation is negligible. [•] In hot rolled strips the precipitated nitride fraction is grain size dependent. [Copyright &y& Elsevier]

Abstract: As an attempt to recycle iron scraps, a new method is proposed to produce stainless steel clad plate by hot rolling. Iron scraps (Q195) were cold pressed into stainless steel pipe (304), and were subsequently hot rolled to produce composite clad plates at 1250°C. Experiments showed that the iron scraps could be compressed into solid steel and joined well with the outer stainless steel surface using the proposed method. The shear strength of the bimetallic interface formed is about 273MPa after seven pass rolling. The clad plates produced show good bending ductility. Element diffusion occurred at the interface during the hot rolling processes. The peak hardness appears in the vicinity of the interface due to the severe plastic deformation under high temperature and pressure during the rolling processes. [Copyright &y& Elsevier]

Abstract: TiB2/AZ31 magnesium matrix composites were prepared under the separate effects of an electromagnetic field, ultrasound and of both in combination. The electromagnetic field appeared to expand the zone of ultrasonic action, resulting in fine grained and more uniform microstructure with a more homogeneous distribution of the reinforcing TiB2 particle clusters in the magnesium alloy matrix. Subsequent hot-rolling further improved the microstructural homogeneity. The resulting TiB2/AZ31 composite sheets exhibited excellent overall mechanical properties, with an ultimate tensile strength of 350MPa and a tensile ductility approaching 8%. [Copyright &y& Elsevier]

To minimize the adjustments to the initial roll speed setting in tube manufacturing, both the tube profile and the tube stress distribution during the rolling are needed to be predicted before the actual rolling. While predicting the tube profile is to make the rolling reach to the metal flow balance state efficiently, predicting the tube stress distribution is to decrease the potential formation of the rolled defects caused by the non-ideal stress distribution in tube at each pass. This requires the rolling model to combine the prediction of tube profile with the prediction of stress distribution of tube in its formulation. A new analytical model which can meet the above requirements is presented in this paper. The mechanics of rolling tube in three-roll continuous retained mandrel rolling has been analyzed in the model. Validity of the model has been examined by hot rolling experiments at the plant. According to the experimental results, the predicted tube profiles are in good agreement with the measured, with the prediction errors of cross-sectional areas being in the range of 0.8∼2.5 %. The theoretical initial roll speed setting calculated based on the proposed model can be applied directly to tube manufacturing, with further adjustments at the mill being less than 4 %. The predicted roll forces calculated based on the proposed model have a maximum deviation from the measured less than 15 %. In general, the hot rolling experimental results at the plant have proved the validity of the proposed model. [ABSTRACT FROM AUTHOR]

[Display omitted] • AZ31 alloy with full of equiaxed grains was obtained by GTAW-based additive manufacturing. • Relationship between the microstructure and properties of AMed AZ31 alloy were studied. • Comparison between the corrosion resistance of hot-rolled and AMed AZ31 alloy was conducted. Additive manufacturing (AM) technology has drawn tremendous attention in producing lightweight and complex metallic components. In this work, a thin wall of AZ31 Mg alloy with fine equiaxed grains was fabricated via gas tungsten arc-based wire arc additive manufacturing (WAAM-GTA) technology. The grain structure, dislocation, and texture of the hot-rolled and WAAM-GTA AZ31 samples were analyzed by EBSD, while the matrix and dispersed phases were characterized by EDS and X-ray diffraction. The 3D porosity of samples was examined quantitatively by an X-ray computed tomography (XCT). The results show that dominated equiaxed α-Mg grain structure was obtained together with negligible precipitated phase. The mechanical properties of WAAM-GTA AZ31 were superior to their cast counterparts and close to those of wrought AZ31, and their correlation to microstructure and defects were explored. Moreover, the WAAM-GTA AZ31 showed excellent electromechanical corrosion performance in 3.5 % NaCl solution as compared to the hot-rolled AZ31 plate. The WAAM-GTA technology therefore offers new routes to fabricate AZ31 Mg components with equiaxed grain structure, as well as favorable mechanical properties and electromechanical corrosion performance. [ABSTRACT FROM AUTHOR]

Al 6061- and Al 7108-SiCp composites (Al-PMMC) were prepared by stir-casting with SiCp size of 8 and 15μm and volume fraction (Vf) of 0–20%. These composites were then subjected to successive hot rolling at 450°C using a strain rate of 1s−1 while the intermediate period of heating between each two successive rolling steps was 1min to 1h. Tensile test was conducted on the as-rolled composite strips with 3.0, 1.1 and 0.4mm thicknesses using 81, 94 and 98% reductions, subsequently, with a tensile rate of 10MPas−1. Different tensile properties including ultimate tensile strength UTS, Young's modulus and elongation, were determined. The tensile behaviour was analysed in view of matrix alloy type and SiCp size and Vf. The effect of T6 treatment on the microstructure and tensile properties was also presented. Generally, successive hot rolling resulted in decreasing casting defects such as void and SiCp agglomeration present in the as-cast composites and hence enhanced mechanical properties were achieved. Almost 240 and 390% improvement in ultimate tensile strength (UTS) for 6061 and 7108 composite was obtained, respectively. The improvement in strength was remarkable for composites rolled to 0.4mm. Annealing improved the elongation% at break of the 10–15% Vf composite more than 3 times. UTS of rolled composite was enhanced by T6 treatment at 176°C and 120°C for 6061 and 7108 composites. The effect of T6 treatment on the composite tensile behaviour was discussed. [ABSTRACT FROM AUTHOR]

Abstract: In order to characterise the mechanical response of materials in manufacturing processes, such as wire and bar rolling involving very high strain rates, temperatures and level of straining, an experimental device is presented. The device is suitable for testing at strain rates up to approximately 4000s−1, temperatures up to 1200°C (≈1500K) and strains around 0.5. It is based on the classical Split Hopkinson pressure bar and is complemented with an inductive heating source for achieving requested temperatures. By keeping the specimen separated from the Hopkinson bars just until an instant before impact (50ms) considerable cooling and temperature gradients in the specimen are avoided. Three steel grades, two stainless steels and a high-speed steel, were tested. Four different material models whose parameters were fitted to the obtained experimental data were used for mechanical characterisation: two empirically based and two physically based. Overall, one of the physically based models showed the best agreement between experimental results and the predicted flow stresses. [Copyright &y& Elsevier]

Abstract: To meet targeted reductions in CO2 emissions by 2050, demand for metal must be cut, for example through the use of lightweight technologies. However, the efficient production of weight optimized components often requires new, more flexible forming processes. In this paper, a novel hot rolling process is presented for forming I-beams with variable cross-section, which are lighter than prismatic alternatives. First, the new process concept is presented and described. A detailed computational and experimental analysis is then conducted into the capabilities of the process. Results show that the process is capable of producing defect free I-beams with variations in web depth of 30–50%. A full analysis of the process then indicates the likely failure modes, and identifies a safe operating window. Finally, the implications of these results for producing lightweight beams are discussed. [Copyright &y& Elsevier]

Abstract: In order to meet the requirement of schedule-free rolling (SFR) for wide non-oriented electrical steel production with a large number of the same width strip rolling campaigns, ASR (asymmetry self-compensating work rolls) shifting strategies for different rolling schedules are studied. According to the actual rolling process, the work roll wear prediction mathematical model for non-oriented electrical steel sheets and a 3D finite element model for roll stacks are established. The effects of the shifting step and the shifting rhythm on the ASR wear contour and the loaded roll gap profile within the entire rolling campaign are analyzed. The reasonable ASR shifting strategies for different rolling schedules are developed. In comparison with the conventional work roll contour of K-WRS mill, the self-maintenances of roll contours for ASR reach to more than 88%, the rate of the measured strip crown less than 45μm increased from 41.8% to 94.9%, and the rate of the measured strip crown larger than 52μm decreased from 32.6% to 2.0% by industrial test on the production of the same strip-width for wide non-oriented electrical steel sheets in the 1700mm hot strip mill of WISCO. The ASR technology has applied to the production successfully. [Copyright &y& Elsevier]

Abstract: In order to reduce the rolling force and the roll wear, the lubricants have been used in hot rolling of steel. In order to evaluate the tribological behavior at the interface between roll and workpiece in hot steel rolling, it is important to measure the coefficient of friction and examine the effect of the tribological factors on the coefficient of friction. In this paper, the effect of the rolling speed on the coefficient of friction is investigated using the tribo-simulator testing machine for hot rolling developed by the authors. The workpiece used is SPHC. The roll material is SKD11 and the surface roughnesses are 0.05μm, 0.2μm and 0.8μm. The rolling tests are carried out at a temperature of 800°C during a rolling distance of 400mm, changing the rolling speed from 15 to 70m/min. The colza oil is used as a base oil and the emulsion concentrations are 0.1% and 3.0%. The coefficient of friction at an emulsion concentration of 3.0% is independent on the rolling speed. On the other hand, the coefficient of friction at an emulsion concentration of 0.1% decreases with increasing rolling speed in the lower range of rolling speed, but it increases in increasing rolling speed in the higher range of rolling speed. [Copyright &y& Elsevier]

Abstract: During hot deformation of Al–Mg–Si alloys, a non-uniform microstructure is developed due to differences in localized strain. Physical simulations were performed to examine the effects of processing parameters such as deformation temperature, total reduction, rolling schedule and alloying additions on the grain structure evolution. Overall, the kinetics of recrystallization followed the traditional trends predicted by JMAK kinetics. Electron backscatter diffraction (EBSD) was used to quantify the difference in recrystallization kinetics at the sample surface and mid-thickness. The results showed that the surface showed elevated kinetics when compared to the sample mid-thickness. [Copyright &y& Elsevier]

Abstract: In this work, a numerical-based model has been proposed to calculate distributions of temperature, strain and strain rate during hot rolling as well as the subsequent microstructural changes after hot rolling of an aluminum alloy. For doing so, a transient finite difference analysis together with a stream function method have been coupled to calculate temperature distribution and velocity field within the rolling metal. A new approach considering internal state variables method has been employed to predict the kinetics of static recrystallization after hot rolling. The predicted results were then compared with the experimental ones and a good consistency was observed between the two sets of data. [Copyright &y& Elsevier]

Abstract: An experimental study was carried out to investigate the possibilities to use rolls made from Si3N4–TiN ceramic composite in hot rolling of steel. The results show that the wear of the ceramic material was lower than the wear of a reference cast iron. The results suggest that the Si3N4–TiN material is beneficial to use in a hot rolling process, on condition that the temperature of the work piece material is held sufficiently high. [Copyright &y& Elsevier]

Abstract: Generally, the vertical roll process is used to achieve extensive width reduction in hot strip mill. However, it is difficult to avoid the defects such as dog-bone and seam-defect. The sizing press has been developed in response to the defects mentioned above. Especially, this study is carried out to investigate the deformation of slab by two-step sizing press. The deformation behavior in the width sizing process is more favorable than that in conventional vertical rolling edger. The objective of this study is to determine the optimal anvil shape parameters in the sizing press with two-step die from the viewpoint of forming load and edge-seam length. In the sizing press with two-step die, to minimize forming load and dog-bone profile anvil shape parameters are considered as. The optimal combination of the parameters is determined by FE-simulation and artificial neural network (ANN). In general, the edge-seam defect occurs parallel to the rolling direction at both edges in horizontal rolling process after sizing press. The slab deformation in sizing press with convex anvil is analyzed by FE-simulation. The most suitable profile of the anvil is also discussed for the improvement of trimming loss because of the side seam defect by FE-simulation and ANN. [Copyright &y& Elsevier]

Abstract: In this work, a mathematical model has been developed to predict distributions of temperature, strain and strain rate during hot rolling as well as the subsequent microstructural changes after hot deformation. For doing so, a 2-D finite element analysis together with a stream function method have been coupled to calculate temperature distribution and velocity field within the rolling metal while the roll force has been estimated, through using an upper bound solution. Also the additivity rule and Avrami-type equation have been employed to predict the kinetics of static recrystallization after hot rolling. The model has been examined on AA5083. Hot rolling experiments have been conducted under various hot deformation conditions. Comparison between the theoretical results and the experimental data shows the validity of the model. [Copyright &y& Elsevier]

Abstract: Front end bending in plate rolling creates enormous forces impacting on the roller tables, which reduce productivity eventually entailing expensive downtimes. Furthermore, front end bending reduces the quality of the plates considerably. Many investigations on that topic have been published in the past and are summarized in this work. Some basic relations explaining the causes and consequences of front end bending are already known. However, operators are still struggling with the problem. An implicit two-dimensional finite element model has been employed to simulate the front end bending based on fundamental geometric relations. This paper focuses on the well known bending due to the related mismatch of circumferential speed between the work rolls. The shift of the neutral point, i.e. where no curvature occurs, from thin to thick rolling stock is reported for the first time and shows interesting results. The mismatch of bending intensity between thin and thick rolling stock is also reported. The absence of the neutral point for very thick rolling stock is explained. A comparison between previously published results and the current investigations provides a broad overview on the front end bending in plate rolling. [Copyright &y& Elsevier]

Abstract: The AZ31 magnesium alloy sheets were hot-rolled by using a small sized rolling mill. The thickness was successfully reduced to 0.6mm without surface cracks. The effects of rolling reduction on microstructure and hardness of the thin sheets were investigated. The rolled sheets of less than 1mm in thickness had a preferred orientation () and a very fine-grained homogeneous microstructure with an average grain size of about 20μm as a result of dynamic recrystallization. The eutectic precipitates (α-Mg and β-Mg17Al12) changed gradually from a blocky structure to small particles of about 5μm with increasing reduction, through the diffusion of the eutectic precipitates from the grain boundaries to the inner of the refined grains during the hot rolling. The hardness of the as-rolled samples increased initially from 50 to 80HV with increasing reduction, and reached the highest value of 90HV at 97% reduction in thickness. [Copyright &y& Elsevier]

Abstract: The effect of different variables of the rolling operation on the lateral spread in the first pass of the finishing mill has been studied. A simplified 3D finite element model has been used to calculate the stress and strain fields in the rolling gap using the constitutive equations for the materials calculated from torsion tests performed at high temperatures. Although a very simple approach to the friction problem has been used (Coulomb friction), good agreement between the calculations and the experimental values measured for the power in an Arcelor facility (Avilés, Spain) has been observed. The influence of the interstand tension between the rolling mills on the spread and the stress state in the slab has been also studied. [Copyright &y& Elsevier]

Abstract: Al–4.5Cu–3.4Fe composite was cast in a heated cast-iron mould to obtain a structure consisting of needles of brittle Al3Fe intermetallic in a eutectic matrix of Al+Al3Fe. Pieces of this as-cast composite were cut in the form of small bars and deformed to large strain by hot rolling. Tensile tests were carried out on the rolled specimens at room temperature. The associated fracture surfaces were examined under a scanning electron microscope. With an increase in the extent of rolling, the needles of the brittle Al3Fe intermetallic were found to break down into progressively smaller fragments. At the same time the fragmented particles got oriented along the direction of rolling, the extent of orientation increasing with the extent of rolling. A gradual increase in ultimate tensile strength and ductility with an increase in the extent of rolling was observed. The poor mechanical properties of the as-cast composite resulted from the ‘coarse crystalline’ fracture which was caused by the cracking of the brittle second phase particles (Al3Fe). A transition from the coarse crystalline fracture in the as-cast condition to the form of void growth and void linkage occurred as the extent of rolling increased. [Copyright &y& Elsevier]

Abstract: Rolling processing was selected to produce fully dense sheet from porous preform. Deformation behavior of the porous preform prepared by spray deposition during hot densification rolling has been investigated. The strain distribution in the deformation zone of the porous samples is analyzed. A notable deformation behavior is that the thickness reduction of the porous preform decreases from the surface to the center across the section, even though the total thickness reduction is up to 40% in a single pass, which is obviously different from the deformation characteristic of the fully dense metal. A decreased normal stress from surface to center and a lower work hardening effect during rolling of porous metal are supposed to be the main factors. When the longitudinal and transverse flow during rolling were retarded by contact friction, a decreased strain in length and width will result in a decreased thickness strain during rolling of fully dense metal due to a constant volume. However, the porous preforms tend to be compacted firstly near the surface of porous metal due to porosity. [Copyright &y& Elsevier]

Abstract: Reinforcement bars are used chiefly in the building industry in the production of reinforced concrete constructions, and as working elements in bridge building. An important factor, which provides for the common bearing of the bar and concrete, is that its effectiveness is highly dependent on dimensions and positioning of the ribs at the bar''s surface. In this paper, the computer simulation of the rolling of the round reinforcement bar is presented. It has been performed in order to define the specific features of the mode of metal flow in the roll gap and to determine the effect of the shape and dimensions of the roll on the pitch of the ribs of the finished bar. [Copyright &y& Elsevier]

Abstract: A set of unified viscoplastic constitutive equations, which models recrystallized volume fraction, dislocation hardening, grain size evolution and their effects on viscoplastic flow of a steel under hot forming conditions, has been implemented into the commercial FE solver MARC through the user defined subroutine UVSCPL. An FE model and the corresponding numerical procedure have been established to simulate the microstructure evolution in the conditions of rolling a commercial steel plate. A series of FE simulations have been carried out to study the effects of rolling parameters on microstructural evolution of the material. This provides evidence for the selection of hot rolling parameters, so that the materials with designed microstructure can be processed. [Copyright &y& Elsevier]

Abstract: In this paper the high temperature, high strain rate mechanical behaviour of two free-machining steels is reported. The effect of bloom position on material ductility is investigated, and a physically-based parameter is created to link microstructure characteristics at various bloom locations with observed material ductility. [Copyright &y& Elsevier]