Interfacial microstructure evolution for coordinated deformation of Mg/Al composite plates by asymmetrical rolling with differential temperature rolls

In this work,Mg/Al composite plates with different thickness ratios were prepared by the asymmetrical rolling process with differential temperature rolls and isothermal symmetrical rolling.Microstructural evolution and mechanical properties of matrix and composite materials with different thicknesses were analyzed.Influence of thickness ratios on the coordinated deformability of heterogeneous metals and interface toughness under the action of temperature gradient and shear force was investigated.Results show that the relative deformation rates of matrix and composite materials converge gradually under the influence of work hardening of Mg/Al layer.The Mg layer is mainly DRXed grains and texture intensity gradually weakens with increasing thickness ratio.The Al layer is mostly dominated by subgrains and deformed grains,which have a strong correlation with thickness ratio.Strength and plasticity of composites first increase and then decrease with increasing thickness ratio.Fracture of composite plate occurs in intermetallic compounds(IMCs).Thickness of IMCs has a strong positive correlation with thickness ratio.When the thickness ratio of AZ31B/Al6061 for 5,the relative thickness of IMCs is the largest and the relative bonding strength is the smallest.When the thickness ratio of AZ31B/Al6061 for 3,there is no element aggregation in IMCs,and the comprehensive mechanical properties of composite plate are comparatively better.

Influence of symmetric and asymmetric rolling on texture evolution of work-hardened AA 5xxx aluminium alloy

The textures and microstructures of hot-and cold-rolled sheets of an AA 5454 aluminium alloy were studied,with special attention paid to comparing the texture development for the symmetric and asymmetric cold rolling.Scanning electron microscopy with electron-backscatter diffraction was used to monitor the development of the microstructure in the differently deformed and additionally annealed samples.Details of the formations and transformations of individual texture components occurring during the rolling processes were observed and discussed.The average grain sizes,textures and mechanical properties were correlated and explained for the symmetric and asymmetric cold-rolled samples.The asymmetric rolling is beneficial in terms of deep drawability because it reduces the planar anisotropy of the annealed material due to the decrease of the Cube,Goss,rotated-Cube and η-fibre texture components and at the same time strengthens X1-and X2-fibre texture components which are shear texture components and improve deep drawability.During the asymmetric cold rolling,the temperature increases due to friction,triggering recrystallisation processes and leading to larger grains.It is also confirmed that asymmetric cold rolling uses less rolling force and consequently less energy to produce a final material with better formability,particularly earing.

Short-Term Rolling Prediction of Tropical Cyclone Intensity Based on Multi-Task Learning with Fusion of Deviation-Angle Variance and Satellite Imagery

Tropical cyclones(TCs)are one of the most serious types of natural disasters,and accurate TC activity predictions are key to disaster prevention and mitigation.Recently,TC track predictions have made significant progress,but the ability to predict their intensity is obviously lagging behind.At present,research on TC intensity prediction takes atmospheric reanalysis data as the research object and mines the relationship between TC-related environmental factors and intensity through deep learning.However,reanalysis data are non-real-time in nature,which does not meet the requirements for operational forecasting applications.Therefore,a TC intensity prediction model named TC-Rolling is proposed,which can simultaneously extract the degree of symmetry for strong TC convective cloud and convection intensity,and fuse the deviation-angle variance with satellite images to construct the correlation between TC convection structure and intensity.For TCs'complex dynamic processes,a convolutional neural network(CNN)is used to learn their temporal and spatial features.For real-time intensity estimation,multi-task learning acts as an implicit time-series enhancement.The model is designed with a rolling strategy that aims to moderate the long-term dependent decay problem and improve accuracy for short-term intensity predictions.Since multiple tasks are correlated,the loss function of 12 h and 24 h are corrected.After testing on a sample of TCs in the Northwest Pacific,with a 4.48 kt root-mean-square error(RMSE)of 6 h intensity prediction,5.78 kt for 12 h,and 13.94 kt for 24 h,TC records from official agencies are used to assess the validity of TC-Rolling.

Influence of Rare Earth Elements on Microstructure and Mechanical Properties of Cast High-Speed Steel Rolls

The influence of rare earth （RE） elements on the solidification process and eutectic transformation and mechanical properties of the high-V type cast, high-speed steel roll was studied. Test materials with different RE additions were prepared on a horizontal centrifugal casting machine. The solidification process, eutectic structure transformation, carbide morphology, and the elements present, were all investigated by means of differential scanning calorimetry （DSC） and scanning electron microscopy energy dispersive spectrometry （SEM-EDS）. The energy produced by crack initiation and crack extension was analyzed using a digital impact test machine. It was found that rare earth elements increased the tensile strength of the steel by inducing crystallization of earlier eutectic γ-Fe during the solidification process, which in turn increased the solidification temperature and thinned the dendritic grains. Rare earth elements with large atomic radius changed the lattice parameters of the MC carbide by forming rare earth carbides. This had the effect of dispersing longpole M C carbides to provide carbide grains, thereby, reducing the formation of the gross carbide and making more V available, to increase the secondary hardening process and improve the hardness level. The presence of rare earth elements in the steel raised the impact toughness by changing the mechanism of MC carbide formation, thereby increasing the crack initiation energy.

Coupled Dynamic Modeling of Rolls Model and Metal Model for Four High Mill Based on Strip Crown Control

The crown is a key quality index of strip and plate, the rolling mill system is a complex nonlinear system, the strip qualities are directly affected by the dynamic characteristics of the rolling mil. At present, the studies about the dynamic modeling of the rolling mill system mainly focus on the dynamic simulation for the strip thickness control system, the dynamic characteristics of the strip along the width direction and that of the rolls along axial direction are not considered. In order to study the dynamic changes of strip crown in the roiling process, the dynamic simulation model based on strip crown control is established. The work roll and backup roll are considered as elastic continuous bodies and the work roll and backup roll are joined by a Winkler elastic layer. The rolls are considered as double freely supported beams. The change rate of roll gap is taken into consideration in the metal deformation, based on the principle of dynamic conservation of material flow, the two dimensional dynamic model of metal is established. The model of metal deformation provides exciting force for the rolls dynamic model, and the roils dynamic model and metal deformation model couple together. Then, based on the two models, the dynamic model of rolling mill system based on strip crown control is established. The Newmark-13 method is used to solve the problem, and the dynamic changes of these parameters are obtained as follows： （1） The bending of work roll and backup roll changes with time; （2） The strip crown changes with time; （3） The distribution of rolling force changes with time. Take some cold tandem rolling mill as subject investigated, simulation results and the comparisons with experimental results show that the dynamic model built is rational and correct. The proposed research provides effective theory for optimization of device and technological parameters and development of new technology, plays an important role to improve the strip control precision and strip shape quality.

Comprehensive contour prediction model of work rolls in hot wide strip mill

The predictive calculation of comprehensive contour of work rolls in the on-line strip shape control model during hot rolling consists of two important parts of wear contour calculation and thermal contour calculation, which have a direct influence on the ac- curacy of shape control. A statistical wear model and a finite difference thermal contour model of work rolls were described. The comprehensive contour is the equivalence treatment of the sum of grinding, wear, and thermal contours. This comprehensive contour calculation model has been applied successfully in the real on-line strip shape control model. Its high precision has been proved through the large amounts of actual roll profile measurements and theoretical analyses. The hit rates （percent of shape index satisfying re- quirement） of crown and head flatness of the strips rolled, by using the shape control model, which includes the comprehensive contour calculation model, have about 16% and 10% increase respectively, compared to those of strips rolled by using manual operation.

Analysis of the thermal profile of work rolls in the hot strip rolling process

A 2-dimension axisymmetric model was developed by the finite-differencemethod, which can be used to predict the transient temperature field and thermal profile of workrolls in the hot strip rolling process. To demonstrate the accuracy and reliability of the solutiondeveloped, the calculation results were compared with the production data of a 1700 mm hot striprolling mill and good agreement was found between them. The effect of strip width and roll shiftingon the thermal expansion of the work rolls was studied. It is found that the strip width has markedeffect on the efficient thermal crown. Initially, when the rolling strip changes from narrow towide, a bigger efficient thermal crown can be quickly achieved; afterwards, when the rolling stripchanges from wide to narrow, not only the influence of uneven wear can be reduced but also theexcessive efficient thermal crown can be avoided. It is also found that the work roll shifting has adeterminate but not obvious effect on the reduction of the efficient thermal crown, and will makethe strip shape unstable without being used properly.

Gauge-meter model building based on the effect of elastic deformation of rolls in a plate mill

The calculation error of the gauge-meter model will affect the gap setting precision and the self-learn precision of rolling force. The precision of the gauge-meter model is strongly influenced by plate width, working roll radius, backup roll radius, working roll crown, backup roll crown, and rolling force. The influence rules are hard to get by measuring. Taking a conventional 4-h plate mill as the research subject, these influences were transferred into the calculation of roll deflection and flattening deformation. To calculate these deformations, the theory of the influence function method was adopted. By modifying the traditional gauge-meter model, a novel model of the effect of roll elastic deformation on the gap setting was built by data fitting. By this model, it was convenient to analyze the variation caused by the rolling condition. Combining the elastic deformation model of rolls with the kiss-rolls method, a gauge-meter model was put forward for plate thickness prediction. The prediction precision of thickness was greatly improved by the new gauge- meter model.

Thermal spray coating on conductor rolls in electroplating line

In electroplating lines,many conductor rolls are installed in electroplating bath.Typical electroplatings are tin plating(ETL) and zinc plating(EGL),and from required product qualities,a vertical cell for the former and a horizontal cell for the latter is often used.Generally,chrome plating or WC cermet thermal spray coating is applied to stainless steel conductor roll in ETL for prolonging service life by improvement of wear resistance and corrosion resistance.On the other hand,Hastelloy type alloy substrate is used for conductor rolls in EGL due to severe corrosion environment of electro plating solution.Thermal spray coating is effective for reducing wear,but there are many cases where the coating cannot complete expected service life when corrosion becomes an issue.In this study,thermal spray coating for ETL conductor roll and development of the coating for EGL conductor roll to meet expected service life are described.

Numerical simulation and model of control-efficiency of thermal crown of work rolls in cold rolling

Aiming at accuracy control of the thermal crown of work rolls in cold rolling,new parameters such as regulation domain and control-efficiency factors were proposed and a numerical analysis model of the thermal crown of work rolls was established using finite difference method to study roll's thermal deformation.Based on simulation results,the influences of control-efficiency factors on thermal crown are presented and the thermal crown of work rolls is analyzed after taking sub-cooling of sprinkling beam into consideration.It has been found that the control-efficiency factor of any position on the roll's surface is linear function of the temperature and the control ability of water temperature is stronger than other control parameters.In addition,the verification of the model has been carried out based on the producing technology data in some factories and the numerical simulation results coincide well with the experimental data.Therefore,this work has important value for on-line control of roll's crown in cold rolling.

Experimental Study on Surface Deterioration of Hot Rolling Mill Rolls under Near Service Conditions

With specially designed hot rolling test equipment,the surface deterioration process of hot rolling mill rolls can be simulated and representative samples were obtained.Thus a series of micro-analyses can be done onto the sample's worn surface,including wear loss,worn surface morphology,wear mode,oxidation and other influences from environment conditions.A leading study has been done with a high chromium cast iron to show the rolling test conditions and the methodologies of follow-up investigations for all the above-mentioned micro-analyses.Primary results have shown that high chromium iron roll may undergo complex degrading mechanism,and most of them can be investigated with the help of this research method-

A High-Resolution Modeling Study of the 19 June 2002 Convective Initiation Case during IHOP 2002:Localized Forcing by Horizontal Convective Rolls

The initiation processes of one of the initial convective cells near and on the east side of a dryline on 19 June 2002 during the IHOP 2002 field experiment in the central United States is analyzed in detail based on a high-resolution numerical simulation. Prominent horizontal convective rolls and associated near-surface moisture convergence bands [called roll convergence bands(RCBs) here] develop within the convective boundary layer(CBL) due to surface heating, in the hours leading to convective initiation(CI). The RCBs east of the dryline are advected toward the primary dryline convergence boundary(PDCB) by the southerly moist flow as the CBL deepens with time. Backward trajectories of air parcels forming the initial precipitating updraft of the convective cell are found to primarily originate at about 1–1.5 km above ground, within the upper portion of the shallower CBL earlier on. The representative air parcel is found to follow and stay on top of a surface RCB as the RCB moves toward the PDCB, but the RCB forcing alone is not enough to initiate convection. As this RCB gets close to the PDCB, it moves into a zone of mesoscale convergence and a deeper CBL that exhibits an upward moisture bulge associated with the PDCB. The combined upward forcing of the RCB and the mesoscale PDCB convergence quickly lifts the representative air parcel above its level of free convection to initiate convection. A conceptual model summarizing the CI processes is proposed.

High-speed steel rolls used for cold rolling

During cold rolled production of steel, each change of rolls causes a halt in production and affects the roll＇ s grinding maintenance and consumption. Consequently,rolls are very critical to the costs of steel production. Besides the rolling accidents, surface quality problems, including inhomogeneous wear and a decrease of the surface roughness of the rolls are other main reasons for outage and a change of the rolls. Therefore, safe rolls, with superior wear resistance and roughness retentivity will be a future trend in the cold rolling steel industry. In this study, the property characteristics and in-service performance of high-speed steel （HSS） cold rolling work rolls at Baosteel are discussed. The results of this study indicate that in-service performance of HSS cold work rolls has an improvement over conventional rolls. Implementation of HSS work rolls will prolong the rolling campaign and improve the rolling stability, thus, the cost of cold rolling production can be better controlled.

Development and Application of Die-Casting High Speed Steel Rolls

Due to its high hardness,good red hardness and excellent wear resistance at high temperature,high speed steel(HSS)is fit for the roll manufacture.In order to overcome the segregation of centrifugal casting of HSS roll,die-cast processes were developed and its effects on the properties of the HSS roll were investigated.It was found that pressure,pressing time and speed are three important factors affecting shrinkage cavity.For pouring temperature of 1 400-1 450 ℃,pressure of 150-160 MPa,pressing time of 120-150 sand pressing speed of 14-16mm/s,a compact HSS roll was obtained,which has no segregation and small working allowance.In the high speed wire rod rolling mill,service life of the HSS roll is 5to 8times longer than that of high nickel chromium infinite chilled cast iron roll.

Analysis of rolls deflection of Sendzimir mill by 3D FEM

The deflection of rolls of Sendzimir mill with double AS-U-Roll was simulated by finite element method(FEM). The influences of rolling pressure, strip width and rolls-assignment on rolls deflection were analyzed. The results show that the work roll deflection increases with the increase of rolling pressure and the reduction of work roll radius, but the rigid displacement of work roll slightly changes; the work roll end might appear negative displacement for the narrow strip width and high rolling pressure that might cause the contact of work rolls. The research results are significant for guiding production and theoretical analysis of the rolls system of Sendzimir mill.

Test and analysis of mechanism and influential elements of axial drifting of weldment on turning rolls

The mechanism of axial drifting of weldment on welding turning rolls was investigated. The simulation test for influential element has been carried out as well. The results show that axial drifting is caused by unparallel between the axis of roller and weldment resulting in axial force. When the helical angle λ between rolls and weldment is from 1°to 6°, the tanλ is linearly related to axial drifting speed v. Increase of number of deflected rollers causes non linear increase of v. The angle of λ makes more effect on speed v than what the angle of deflection does. The turning speed of weldment is proportion to axial drifting speed v. The dead weight of weldment has little effect on speed v.

Analysis of surface cracking in water-cooled rolls and heat transfer between furnace chamber and rolls in a direct flame furnace

In the direct fired furnace of a continuous annealing line, seal rolls are susceptible to deformation that leads to surface defects of steel strips. According to failure analysis, the reasons include improper structural design and heat imbalance. An improved design has been proposed to reduce stress concentration and thermal radiation. A heat transfer model has been employed to determine the proper water flow rate for roll cooling. Industrial application proves that seal rolls with the new design has less deformation and longer service life.

Effects of heat treatment on structures and properties of high speed steel rolls

The effects of quenching temperature, cooling pattern, temper temperature andtemper times on the structure and properti-es of high speed steel (HSS) rolls have beeninvestigated. The results show that, when the quenching temperature is lower than 1050℃ thehardness of HSS increases with the quenching temperature increasing in oil cooling, but when thequenching temperature exceeds 1100℃ the hardness decreases. In the conditions of salt bath coolingand air cooling, the effect of quenching temperature on the hardness is similar to the above law,but the quenching temperature obtaining the highest hardness is higher than that in oil cooling.When the temper temperature below 350℃ the hardness of HSS has a little change, when above 475℃the hardness will increase with the temper temperature increasing, and the highest hardness isobtained at 525℃. When the temper temperature continues to increase, the hardness decreases. Twicetemper has little effect on the hardness, but three times temper decreases the hardness. HSS in aircooling has lower hardenability, oil cooling can easily produce crackle, and HSS quenching in saltbath has high harde-nability and excellent wear resistance.

Development of centrifugal casting high speed steel rolls

The present study aims at developing the high speed steel (HSS) as rollmaterials to replace the traditional roll materials such as the alloy cast iron and powdermetallurgical (PM) hard alloy. The HSS roll billet was formed by centrifugal casting, and the billetwas rough machined alter soften annealing heat treatment, then it was quenched and tempered to getsuitable hardness and toughness. After that the HSS roll was finish machined to the final dimensionof phi 285 mm in the outer diameter, phi 160 mm in the inner diameter and 120 mm in width and itssurface hardness was tested. Finally the HSS roll was used in high speed wire rod mill. The testresults show that a high and homogeneous hardness can obtain on the work surface of HSS rolls, thesurface hardness is 63-65HRC and its variation is smaller than 2HRC. The impact toughness of thiskind of HSS is about 16 J/cm^2. The results of on-line service investigation in high speed wire rodmill indicate that the HSS rolls have excellent wear resistance, the steel rolling quantity per mmof HSS rolls is 3120 t, the service life-span of HSS rolls is 4 times longer than that of highchromium cast iron rolls and it is close to that of the PM hard alloy rolls. The manufacturingburden of HSS rolls is obviously lower than that of the PM hard alloy rolls, it is only 25 percentof that of the PM hard alloy rolls.

Research on development of surface-roughness variation and control technology of the automotive plates and rolls

Surface roughness considerably influences the stamping and coating performance of the automotive plates;however,the surface roughness of the automotive plates is transferred from the roll during the rolling process.Therefore,the variation and control technology regarding the roughness of the automotive plates and rolls has drawn increasing attention from researchers in China and around the globe.In this study,the research methods,analytical techniques,prediction models,transfer rules,and control technologies regarding the surface roughness of the automotive plates and rolls were reviewed.Among these,an online measurement system for automotive-plate and roll surface roughness has been applied to the production lines of Germany,China,Belgium,Holland,Austria,and other countries and has achieved remarkable results.Online measurement and timely feedback regarding the automotive-plate and roll surface roughness are needed to ensure favorable conditions for the establishment of automotive-plate roughness-control measurement.