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In this study, the abrasive impact wear behaviour of a bimetal composite made of medium manganese steels (MMSs) and low carbon steels (LCSs), i.e., the Mn8/SS400 bimetal composite, was investigated using a newly designed wear-testing rig. The need for a new rig arose from the difficulty in replicating real-world wear conditions. Our rig allows for precise control and measurement of wear, simulating harsh environments more accurately than other wear-testing rigs. The bimetal composite Mn8/SS400 demonstrated superior wear resistance, showing an improvement of up to 2.8 times compared to benchmark steels, attributed to its enhanced work hardening sensitivity. Scanning electron microscopy (SEM), X-ray diffractometer (XRD), and electron backscatter diffraction (EBSD) analyses were employed to elucidate the wear mechanisms. After 300 h of abrasive impact wear, the subsurface microhardness of Mn8 reached 601.31 HV, significantly higher than that of the matrix hardness of 292.24 HV, indicating a substantial work hardening effect. The wear mechanism of the Mn8/SS400 bimetal composite was found to be a synergistic effect of grain refinement strengthening, dislocation strengthening, and twin strengthening. Initially, twin strengthening was the dominant mechanism up to 200 h of wear testing. However, after 300 h, contributions from all three mechanisms became increasingly significant, enhancing the overall wear resistance of the composite. [ABSTRACT FROM AUTHOR]

In order to study the evolution laws of the temperature field, flow field, and macroscopic morphology of the molten pool during laser cladding process, this paper focuses on the changes in the morphology and flow field distribution of the molten pool temperature field caused by corresponding parameter changes during laser cladding process. First, a multi-physics field coupling model for laser cladding was established by combining light powder interaction, phase transition, heat transfer, and fluid dynamics, and the temperature and flow fields of the molten pool were analyzed. Then, the influence of process parameters such as laser power, scanning speed, and powder feeding rate on the temperature and flow field of the molten pool was studied. Finally, the influence of Marangoni convection induced by surface tension temperature coefficient on the macroscopic morphology, internal temperature field, and flow field distribution of the molten pool was investigated. [ABSTRACT FROM AUTHOR]

Laser cladding has significant advantages in the forming process of Invar alloy. Nevertheless, the coefficient of thermal expansion, microstructure and mechanical properties still need to be further investigated. In this paper, the Invar alloy powder was used to prepare cladding samples, and the performance and microstructure of the cladding layer were investigated. The mechanical and thermal expansion performances of the cladding layer were analysed using a universal material testing machine and a thermal expansion instrument, and the microscopic structure and micro zone composition of the tensile fracture of the cladding layer were investigated using an SEM scanning electron microscope and an EDS energy spectrum analyser. The results show that the mechanical properties of the Invar alloy transverse cladding layer are better than those of longitudinal cladding layer; the thermal expansion performance of the cladding layer is good, and it keeps the same with the base material in the range of 25–200 °C; the fracture analysis reveals more dimples in the transverse cladding layer fracture with better plastic tenacity, and intergranular fracture and quasi-cleavage fracture in the longitudinal cladding layer fracture with slightly poor plastic tenacity. [ABSTRACT FROM AUTHOR]

This study investigates the effects of different lubrication conditions on drawing force and microcup formation during micro deep drawing (MDD). Results show that graphene lubricant, in combination with TiO2 nanolubricants, has the potential to reduce friction during MDD. The peak drawing force was reduced by 15.39% when both lubricants were used together, while the use of TiO2 nanolubricant and 10.0 mg/ml graphene lubricant reduced it by 6.03% and 14.52%, respectively. The study also reveals that lubricants reduce wrinkling during the formation of microcups by minimising energy consumption during the primary formation. However, the combination of TiO2 nanolubricant and graphene lubricant can cause inhomogeneous formation on the upper part of the blank, leading to more apparent wrinkling. Overall, the study highlights the potential of TiO2 nanolubricant and graphene lubricant in reducing friction and improving microcup formation during MDD. [ABSTRACT FROM AUTHOR]

In the process of rotating machinery fault diagnosis (RMFD), the lack of feature conditions leads to the problem of low accuracy of traditional rule-based reasoning methods FD. This paper proposed a knowledge graph (KG)-driven device FD method and applied it to RMFD. First, we proposed a multi-level KG construction method to get multi-source data based on each level and analyzed the levels that affected the system state. A single-level KG was constructed through data features, and a multilevel KG with a stereostructure was built using a multi-source data fusion model as data support for FD. Second, we proposed an approach based on multilevel KG and Bayes theory to detect the system state and located the source of faults by combining the KG reasoning based on relational paths, then used the relationships between the structures of rotating mechanical equipment for fault cause reasoning and used the KG as a knowledge base for a reason using machine learning. Finally, the proposed method was validated using a steelworks motor as an example and compared with other ways, such as rule-based FD. The results show that under the condition of missing input features, the accuracy of the proposed method reaches 91.1%, which is significantly higher than other methods and effectively solves the problem of low diagnostic accuracy. [ABSTRACT FROM AUTHOR]

During past decades, water-based and oil-in-water (O/W) based nanolubricants with nanoparticles (NPs) as additives have been developed to replace conventional oil-based lubricants for solving contamination problems during rolling processes. The formulations of nanolubricants for rolling need to be continuously improved to provide better lubrication performance. This article reviews the formulation, physicochemical properties, and lubrication mechanisms during rolling with water-based and O/W based nanolubricants, and the effects of nanolubricants on rolling force, surface roughness and oxide skin formation during rolling are discussed. This review aims to facilitate the fundamental understanding of nanolubrication and the development of rolling lubrication technology. [ABSTRACT FROM AUTHOR]

The control of strip profiles has been one of the challenges faced by plate and strip enterprises. Wide rolling mill lines are usually plagued with W-shaped profile defects, which severely hamper the improvement of strip product quality and production stability in enterprises. Due to the lack of efficient control methods for the distribution characteristics of W-shaped profiles, the conventional continuous variable crown (CVC) or CVC plus rolling curve cannot meet the current quality standards required for strip rolling. Therefore, a novel roll contour curve was created by utilising the curve subsection superposition method to achieve precise control of the W-shaped profile. The roll correction areas were constructed along the width direction of strips based on the contour curve of a CVC roll. Additionally, the roll curve was modified by using the segmented cosine functions, to lower the reduction at the quarter of the strip width and increase the reduction at the strip edge. The application findings demonstrate that the proposed novel roll contour, which also has a capacity for the quartic crown adjustment, can effectively address the W-shaped profile issue of strips in the production of wide rolling mills, without compromising the quadratic crown adjustment characteristics of the original roll contour. [ABSTRACT FROM AUTHOR]

The continuous energy input can lead to heat accumulation in the multi-pass lap laser cladding, which results in a progressive increase in the dilution rate and deteriorates the quality of laser cladding. Precisely controlling the stability of the dilution in the multi-pass laser cladding is still challenging. In this study, we proposed a deep-learning driven method for precisely controlling the dilution rate in the multi-pass laser cladding. Initially, the relationship between the dilution rate and power energy is retracted via the experiment-based finite element simulation. Subsequently, the convolution neural network deep learning is applied to optimize and improve the accuracy of the dilution rates in the cladding layer. The experiment verifies that the high stability of dilution rate in each pass, i.e., average errors of less than 10.88%, is achieved via in-situ adjusting of the power energy using the prediction obtained from the proposed method. We also attempted to provide insights into the dilution mechanism in Invar alloy multi-pass laser cladding as well as the potential applications of this method for other materials and other additive manufacturing. [ABSTRACT FROM AUTHOR]

Defects would occur in the weld joint of the wheel rims during the post-flash butt welding (FBW) process suffering from poor plasticity, which will deteriorate the quality and lifecycle of finish products. Therefore, the FBW process of the 440CL high-strength-low-alloy (HSLA) steel was physically simulated and the influence of flash parameters on FBW joints was systematically evaluated in this study. The results showed that the width of heat affected zone increased with accumulated flash allowance (δf) while declined with accelerated flash speed (vf). The recrystallization level would be intensified with increased δf. Meanwhile, the acceleration in vf populated the WZ with a more homogeneous microstructure, higher recrystallization degree and lower dislocation density. The hardness in WZ slightly reduced (202 → 195 HV) as increased δf but obviously dropped (192 → 177 HV) as increased vf. All tensile samples were fractured at the BM location and the tensile properties of FBW joints exhibit a good match with those of BM, with a slight increase in strength (UTS: 468 ~ 493 MPa; YS: 370 ~ 403 MPa) but a mild decrease in plasticity (EL: 39 ~ 44%; RA: 74 ~ 79%). Furthermore, both the joint strength and ductility showed a downward tendency with the increment of δf. However, the strength slightly decreased while the ductility increased with the advancement of vf. These findings would be valuably referential to the real FBW of HSLA steels with optimized microstructure and mechanical performance. [ABSTRACT FROM AUTHOR]

Using pure water in comparison to water-based lubricant containing 4% TiO2 nanoparticles (NPs), the hot rolling tests of 304 stainless steel were carried out at a rolling temperature of 1050 °C under varying rolling reductions and speeds. The effects of lubrication on rolling force, torque, power and contact friction were systematically investigated. The coefficient of friction (COF) during steady-state hot steel rolling was inversely calculated using a developed flow stress model. The COF models including the effects of rolling reduction and speed were proposed via multiple linear regression. The results indicated that the use of the nanolubricant enabled a reduction of rolling force up to 6.1% and decreases in rolling torque and power up to 21.6%, compared to that of water condition. The results obtained from the linear regression agreed well with those from the inverse calculation, suggesting the developed COF models had high accuracy. The lubrication mechanisms were derived from a boundary lubrication regime, owing to ball bearing and mending effects of TiO2 NPs, and formation of thin lubricant film under high rolling pressure. [ABSTRACT FROM AUTHOR]

Intermediate roll shifting (IRS) is widely used for improving the strip shape in the six-high tandem cold mill, but most related studies are limited to a single stand. To fill the knowledge gap, a three-dimensional (3D) multi-stand elastic–plastic finite element (FE) model was developed for a continuously variable crown (CVC)-6 tandem cold mill using data transfer, which was then validated by industrial experimental results. Based on this FE model, the effects of the IRS on the strip crown, strip flatness, loaded roll gap profile and contact normal stress between rolls at each stand were quantitatively analysed. The results show that from Stand 1 (S1) to Stand 5 (S5), the regulation ability of the IRS on the strip crown shows a decreasing trend, which depends on the strip plastic rigidity; in contrast, the regulation ability on the quadratic flatness experiences an obvious increase from S1 to Stand 4 (S4), then a drop at S5, while the IRS exerts little effect on the quartic flatness and quartic crown of the loaded roll gap. Moreover, the most uniform distribution of contact normal stress emerges at different IRSs from S1 to S5. These findings can contribute to a better understanding of the role of the IRS in controlling the strip shape during tandem cold rolling (TCR). [ABSTRACT FROM AUTHOR]

This paper compares the microstructure and mechanical evolution in a high-strength quenched and micro-alloyed steel during the austenitising bending process. Simulation results indicated a new finding that the stress neutral layer (SNL) tends to move to the tension zone during straining. The hardness gradient detected from the centre to compression/tension zones was resulted from comprehensive factors: First of all, the location of SNL revealed a prominent impact on strength. Second, the dislocation accumulation would be responsible for the hardness gradient on the surfaces. In addition, the overall strength decrease during straining was mainly ascribed to integrated effects of dynamic recovery (DRV) and dynamic recrystallisation (DRX). Apart from that, overall smaller martensite packet size and coarser prior austenite grains resulted in the increased hardness value at a lower bending degree. Also, the high consistency between experimental and simulation results is instructive for the practical forming process of railway spring fasteners. [ABSTRACT FROM AUTHOR]

The strip shape inheritance model is widely applied to improve the strip shape quality in tandem cold rolling (TCR). However, the inheritance mechanism is still currently unclear. To bridge this gap, this paper presents a new numerical method for calculating the strip crown inheritance factor. In addition, the effects of the entry strip crown on exit strip crown and flatness were quantitatively analysed at each stand in the TCR using a novel three-dimensional (3D) multi-stand elastic–plastic finite element (FE) model. The results show that the strip crown inheritance factor increases slowly from S1 (stand 1) to S3 (stand 3), while rising sharply from S3 to S5 (stand 5), reaching a peak value of 0.495 μm/μm at S5. This trend coincides with that of strip plastic rigidity, which verifies that the strip crown inheritance factor is dependent on the strip plastic rigidity. Furthermore, the variation of strip crown and flatness under different entry strip crowns from S1 to S5 is jointly influenced by the pass reduction and strip plastic rigidity. Moreover, the strip crown inheritance factor increases with the deformation resistance of the strip at both S1 and S5. These findings not only offer a fresh perspective to understand the mechanism of strip crown inheritance, but also provide an important basis for optimising the strip shape control in the TCR process. [ABSTRACT FROM AUTHOR]

Spark plasma sintering (SPS) is a powerful technique for consolidating metal powders at a remarkably shorter time with excellent quality. We used this technique for sintering nanocrystalline WC10Co powders and simultaneously bonding with high-strength steel. A series of experiments were conducted in order to find out the optimised set of SPS controlling parameters. The effects of temperatures (1000 to 1150 °C, with a 50 °C interval) in sintering nanocrystalline WC10Co powders and their bonding phenomena with AISI4340 steel were examined at a constant pressure of 80 MPa and a holding time of 5 min. The full density of the carbide powders was achieved at a lower temperature compared with that of conventional techniques. A number of techniques were employed to evaluate the microstructural characteristics of WC and steel bilayered composite and their mechanical properties. For determining the bonding strength of the joint, a novel micro-tensile testing system was adopted. Since such investigation is the first of its kind, to the best knowledge of the authors, where SPS is used to join the tungsten carbide with the steel, this research is expected to provide a valuable future reference for fabricating dissimilar bilayered composite materials. [ABSTRACT FROM AUTHOR]

A systematic study was carried out to evaluate the effects of cold rolling and annealing processes on the ridging severity of ferritic stainless steel (FSS). Both microstructural refinement and texture optimisation were achieved with an optimised processing schedule to improve the ridging resistance of FSS. Coarse grain bands comprising of primarily {112} <110> oriented grains were found to form inside cold-rolled and annealed FSS sheets. The effects of annealing schedules and the resultant microstructure and texture on the ridging behaviour of FSS are discussed. The results indicate that the reduction in the fraction of {001} <110> orientation by optimisation of the rolling processes contributes to reduce the ridging height of the FSS during the subsequent forming process. Through extending soaking time and under 880 °C during final annealing step, a maximum of 30% reduction in ridging height can be achieved with a refined microstructure and texture of FSS, improving the surface quality of FSS during subsequent forming processes. [ABSTRACT FROM AUTHOR]

Effects of various lubrication conditions on macroscale deep drawing have been investigated extensively while in microscale due to the open and closed lubrication pocket theory and friction coefficient escalation, proper lubricant concern becomes severe. Microforming is used to produce lighter and more energy-effective products accordingly; in this study, magnesium-lithium (Mg-Li) alloy is chosen to form a superior micro-cup due to its ultralight weight with outstanding ductility. Mg-Li is a new material in microscale; consequently, to study the mechanical properties, a heat treatment process is performed. The dry and oil lubrication conditions are chosen as benchmarks to investigate effects of TiO2 oil-based nano-additive lubricant. Finite element (FE) modelling has been conducted and the simulated results are agreed well with the experimental results where the drawing force is significantly affected by the nano-particle. The formed cup quality regarding the surface roughness has been evaluated extensively by consideration of various parameters and the quality improvement is substantial. [ABSTRACT FROM AUTHOR]

Cermet and steel material bonding is a challenging task, due to their large difference of physical properties, e.g. coefficient of thermal expansion. In this study, a hot compaction diffusion bonding method was employed to fabricate a small-dimensional bimetallic composite of WC-10Co and high strength AISI 4340 steel, where the cermet was used in powder form and the steel as solid. The bimetal composite was characterised by microstructural analysis and mechanical properties evaluation. The interface microstructure reveals a successful metallurgical bonding between the cermet and steel materials. The influence of sintering temperature (1050–1250 °C) was examined at intervals of 50 °C. This study shows that the properties of sintered powder and the bonding quality with the steel improve with an increase in sintering temperature. A bonding beneficiary reaction layer was observed to grow at the joining interface by mutual diffusion of the alloying elements, which increases with the increasing temperature. The maximum width of the reaction layer observed was 4.13 μm and consists mainly of intermetallic ternary carbides. The bonding shear strength of the interface is found to be slightly higher than claimed in previous studies. The developed bimetal composite could be used in applications where a combination of high strength and hardness is required. [ABSTRACT FROM AUTHOR]

Bimetal composites have wide applications due to their excellent overall performance and relatively low cost. In this study, the formability of stainless/carbon steel bimetal medium-thick composite in the stamping process without blank holder was investigated by finite element (FE) simulations and experiments. Uniaxial tensile tests on substrate metal (carbon steel) and clad metal (stainless steel) were first conducted, respectively, in order to obtain the material properties of each metal layer required in the FE simulation. Processing variables, including the layer stacking sequence, relative thickness ratios of two layers and friction conditions, were considered, and their effects on the magnitude of press load and distributions of thickness strain for predicting the high-risk region of necking during stamping were discussed. Experimental tests were carried out to verify the simulation results. It is indicated that simulation results can be used as an evaluation indicator to ensure the bimetal medium-thick composite can be safely formed. [ABSTRACT FROM AUTHOR]

This paper proposes a self-piercing riveting (SPR) method which uses a flange pipe rivet. This joining technology can solve the problems of oblique rivet and incorrect rivet position which are usually found in the SPR with a pipe rivet. The lap shear strength of the joint with a flange pipe rivet is higher than that of a joint with a conventional rivet. In this research, a flange pipe rivet was placed between two sheets with a force applied to the top sheet by a punch riveting machine. The flange pipe rivet moved downward along with the top sheet to induce appropriate bending and form a mechanical interlock in both sheets. Finite element (FE) analysis of the SPR with a flange pipe rivet was done by DEFORM software. The simulated joint cross-section shapes were observed, and the influence of the flange pipe rivet parameters on joint quality was analyzed. Simultaneously, some riveting experiments on joining aluminum sheets were conducted taking into consideration different rivet heights and chamfer angles. The results show that the joining surface is smooth and the simulated joint cross-section shapes are in good agreement with the experimental results. The joining property with a chamfer angle of 45° and a rivet height of 5 mm is found to be the best in joining the Al6063 aluminum alloy sheets with a thickness of 2.4 mm by using the SPR with a flange pipe rivet. [ABSTRACT FROM AUTHOR]

Influences of hydraulic pressure on forming features in micro hydro deep drawing are different from those in normal drawing due to the small size of specimens. In this study, micro hydro deep drawing of SUS304 sheets was carried out in order to study the impacts of the hydraulic pressure on the quality of the drawn cup. Experimental results indicate that there is a critical hydraulic pressure range from 3 to 6 % of the blank's initial yield stress, where wrinkling and earing development trends change twice. The wrinkling and the earing of the drawn cup also reach their local extremes in the critical pressure range. The cup earing value moves in the opposite direction from the wrinkling value. Hydraulic pressure affects the wrinkling and the earing of the drawn cup through changes in the micro-frictional condition, the shape of the blank and its strain-stress state. Micro-finite element (FE) simulation which takes these factors as well as the material size effects into consideration showed similar results to the experimental ones, thus validating the experimental results and the suitability of the micro-simulation model for micro-forming FE simulation. The experimental and simulation results indicate that the critical hydraulic pressure based on the blank's initial yield stress can restrict the wrinkling and the earing of the drawn cup. Ultra-high pressure has the potential to avoid the cup wrinkling and earing. [ABSTRACT FROM AUTHOR]

Bimetal consisting of high-carbon steel and low-carbon steel was prepared by centrifugal composite casting, and thermo mechanical treatments were carried out by hot compression tests using Gleeble 3500 thermo mechanical simulator. The characteristics of microstructure and hot deformation behaviour of the bimetal were investigated. It is concluded that a sound metallurgical bond was achieved by micro mass transfer across the interface between the constituent steels. Four different microstructural regions (including low-carbon steel region, interface region, fully pearlitic region and pro-eutectoid ferritic/pearlitic region) with different mechanical properties were found, which resulted in heterogeneity of plastic deformation within the bimetal. Regardless of strain rate, the low-carbon steel layer preferentially extruded from the bimetal when deformation temperature was below 900 °C, whereas the extrusion was not observed at 900, 1000 and 1100 °C. This indicated that the high-carbon steel/low-carbon steel bimetal can be processed like monolithic material. [ABSTRACT FROM AUTHOR]

Physical parameters, such as microscopic and roughness, play important roles in microforming process due to an increasing ratio of surface to volume of the deformed material. The study on lubrication characterisation in microforming is getting more attractive to researchers because traditional models are not reliable in this scaled down process. In this study, the micro rolling deformation characterisation has been investigated on SUS 304 stainless steel considering lubricant effect and feature size effect. The foil thickness plays an important role in the tribological features of micro rolling. The evolutions of both oil film thickness and foil surface are analysed accordingly. All the results have been verified experimentally via the new developed 2-Hi desktop micro rolling mills. [ABSTRACT FROM AUTHOR]

Size effects play a significant role in microforming process, and any dimensional change can have a great impact on materials' mechanical properties. In this paper, the size effects on deformation behaviour and fracture of phosphor foil were investigated in the form of grain size effect: the ratio of materials' thickness ( T) to average grain size ( D) by micro tensile tests. The ratio was designed to be closed to but larger than, less than and equal to 1, respectively. The results show that the amount of plastic deformation decreases with the decrease of the ratio of T/ D, which indicates that the grain size plays a significant role and grain deformation modes differ when the ratio changes. It is also found that their fractograph reflects different features in terms of micro-dimples and cleavage planes, further demonstrating that when T/ D >1, its materials have a tendency to fracture ductilely, while materials would like to conduct brittle fracture when T/ D <1. So the ratio of T/ D which is close to 1 can be regarded as the divide of ductile fracture and brittle fracture. For T/ D <1, a new constitutive model is proposed based on the classic composite model. The model's results are compared with the experimental ones and the efficiency of the developed models is verified. [ABSTRACT FROM AUTHOR]

With the new development of microforming technology, the demand on the accuracy of the metallic microcomponents is elevating. Springback phenomenon is inevitable during sheet metal forming process and can cause unpredicted dimensional error. The previous research found that the springback value in microforming is difficult to be assessed as the sizes of tools and specimens downsize hundreds even thousands times. This paper focuses on improving the prediction accuracy of springback during micro V-bending. A finite element (FE) model of the micro V-bending has been established via ABAQUS/Standard commercial software where the specimen's microstructure is represented by Voronoi tessellations. With the consideration of the grain heterogeneity, each Voronoi tessellation has been employed with different grain mechanical properties based on experimental results. Corresponding micro V-bending tests have been carried out, and a good agreement between the experimental and simulation results indicates that the developed FE model can accurately predict springback in micro V-bending. [ABSTRACT FROM AUTHOR]

A 3D elastic-plastic finite element method (FEM) model of cold strip rolling for 6-high continuous variable crown (CVC) control rolling mill was developed. This model considers the boundary conditions such as accurate CVC curves, total rolling forces, total bending forces and roll shifting values. The rolling force distributions were obtained by the internal iteration processes instead of being treated as model boundary conditions. The calculated error has been significantly reduced by the developed model. Based on the rolling schedule data from a 1,850-mm CVC cold rolling mill, the absolute error between the simulated results and the actual values is obtained to be less than 10 μm and relative error is less than 1 %. The simulated results are in good agreement with the measured data. The developed model is significant in investigating the flatness control capability of the 6-high CVC cold rolling mill in terms of work roll bending forces, intermediate roll bending forces and intermediate roll shifting values. [ABSTRACT FROM AUTHOR]