Numerical Simulation of Temperature Field and Thermal Stress Field of Work Roll During Hot Strip Rolling

Based on the thermal conduction equations, the three-dimensional （3D） temperature field of a work roll was investigated using finite element method （FEM）. The variations in the surface temperature of the work roll during hot strip rolling were described, and the thermal stress field of the work roll was also analyzed. The results showed that the highest roll surface temperature is 593 ℃, and the difference between the minimum and maximum values of thermal stress of the work roll surface is 145.7 MPa. Furthermore, the results of this analysis indicate that temperature and thermal stress are useful parameters for the investigation of roll thermal fatigue and also for improving the quality of strip during rolling.

Numerical simulation of the temperature fields of stainless steel with different roller parameters during twin-roll strip casting

The temperature field of stainless steel during twin-roll strip casting was simulated by experiment and a finite element （FE） model. By comparing the measured result with the simulated values, it is found that they fit close to each other, which indicates this FE model is effective. Based on this model, the effects of roll gap （t） and roll radius （R） on solidification were simulated. The simulated results give the relationship between t or R and the position of the freezing point. The larger the t is and the smaller the R is, the closer the position of the freezing point is to the exit.

Analysis of Temperature Field and Thermal Crown of Roll During Hot Rolling by Simplified FEM

Thermal crown of roll is an important factor, which affects strip profile. It is necessary to analyze the temperature field and thermal crown of roll for hot strip mill. A new simplified finite element method （FEM） was used to analyze the temperature field and thermal crown of roll, and corresponding models were built according to the practical boundary conditions. Transient roll temperature field and thermal crown were simulated by ANSYS FEM software with considering transient thermal contact and complex boundary condition. Temperature and thermal crown variations on roll surface nodes were obtained. The thermal crown results of roll obtained by FEM simulation were in good agreement with the measured data, indicating that simplified FEM models and results were correct.

Temperature field analysis and its application in hot continuous rolling of Inconel 718 superalloy

A coupled thermo-mechanical model containing metal flow and temperature field for calculating temperature variation has been developed on fourteen-pass hot continuous rolling of round rod for Inconel 718 alloy using 3D elastic-plastic finite element method （FEM）. The temperature of characteristic analysis points in the intermediate cross-section of the workpiece has been simulated at initial temperature ranging from 960 to 1000 ℃ and initial velocity in range of 0.15-0.55 m·s^-1. Based on finite element analysis and microstructural observation in cylindrical hot compression experiments, the appropriate hot continuous rolling technologies have been designed for rod products with different diameters. For a real rolling practice, the simulated surface temperature was examined and is in good agreement with the measured one.

Numerical simulation of roll temperature field and analysis of influence factor during the single-stand reversing cold rolling process

Accurate calculation results of roll temperature are the key factors in rolling cooling and lubricating technology during the single-stand reversing cold rolling process. By combining the high-strength steel rolling experiments ,the numerical simulation of roll temperature, and the influence factors in reversing cold rolling were studied. The research results correspond with those of rolling experiments and show that the research method could provide effective instruction for roll cooling and emulsion flow rate control during the on-site rolling process.

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.

Characteristics of Fluid Flow and Temperature Field of Twin-roll Steel Strip Casting with a Novel-type Delivery System

A novel-type delivery system consisting of a special feeding device and delivery device was developed and applied to a φ600 mm× 1 000 mm twin-roll casting system for producing the steel strip of 2 mm in thickness, and the characteristics of fluid flow and temperature field in the casting pool were investigated by mathematical simulation. The results showed that the melt from the novel-type delivery system was distributed to the casting pool along the width direction smoothly and uniformly. At the casting speed of 80 m/min, the difference of minimum residence time （groin） and actual average residence time （tave） among different ports of the delivery device was less than 0.18 s and 0.26 s respectively, and the average amplitude of level fluctuation was 0.3 mm to 0.6 mm on the free surface of casting pool. In addition, the difference of temperature on the free surface of the pool was below 20 K and the difference across the width direction of roll in different pool depths was less than 13 K, which indicates that the uniformity of temperature distribution was obtained in the casting pool to maintain the casting process and the defect-free steel strip can also be obtained.

Thermal Crown Model and Shifting Effect Analysis of Work Roll in Hot Strip Mills

Considering the effect of work roll shifting on roll temperature field,a finite difference method of PR format for roll temperature field was presented,which can meet the requirements of accuracy and speed of online calculation.The step-by-step accumulation method was used to simulate the roll temperature field and thermal crown,and the evolution of roll thermal crown in a rolling campaign was studied.And then,the effects of strip width,rolling rhythm and work roll shifting on roll thermal crown were analyzed.It is found that work roll shifting can disperse the thermal expansion of the roll body especially the edge to make roll thermal contour uniform.The effect of work roll shifting on roll thermal crown is mainly concentrated in regions around twice of roll shifting stroke,and the change range of roll thermal crown is±30μm or so in the same roll body location.

Control and application of cooling path after rolling for hot strip based on ultra fast cooling

Hot rolled strip requires diverse and flexible control of cooling path in order to take full advantages of strengthening mechanisms such as fine grain strengthening, precipitation strengthening, and transformation strengthening, adapting to the development of advanced steel materials and the requirement of reduction-manufacturing. Ultra fast cooling can achieve a great range of cooling rate, which provides the means that the hardened austenite obtained in high temperature region can keep at different dynamic transformation temperatures. Meanwhile, through the rational allocation of the UFC （ultra fast cooling） and LFC （laminar flow cooling）, more flexible cooling path control and cooling strategy of hot rolled strip are obtained. Temperature distribution and control strategies under different cooling paths based on UFC are investigated. The process control temperature can be limited within 18 ℃, and the mechanical properties of the steels get a great leap forward due to the cooling paths and strategies, which can decrease costs and create great economic benefits for the iron and steel enterprises.

Mechanism of necking defect of 6082 aluminium alloy rolled by cross-wedge rolling method based on material thermal properties

Necking defects have long troubled the application of cross-wedge rolling technology in aluminium alloy shaft parts.To accurately predict necking defects,new judgement conditions are established based on the thermal performance of 6082 aluminium alloy.The limit-sectional shrinkage without necking defects is achieved by combining theoretical calculation and finite-element model analysis,which couples heat transfer and deformation.In this paper,a 6082 aluminium alloy extruded rod with a 40 mm diameter rolled at a preheated temperature of 500℃and a rolling angular velocity of 1 rad/s is taken as an example.The simulation and experimental results show that necking defects do not occur on the rolled pieces if the sectional shrinkage is below the limit-sectional shrinkage but will occur when the sectional shrinkage is above it.The results prove that the prediction model of necking defects in cross-wedge rolling of 6082 aluminum alloy is feasible,and this research provides a theoretical basis for the qualified aluminum alloy shafts produced by the cross-wedge rolling.

Wear and Thermal Stress Analysis of Side Dam for Twin Roll Strip Casting

The simulation of the work roll temperature field was carried out by means of ANSYS software, and the thermal crown of the roll along its axis was obtained. The thermal-structural coupled element and contact element were introduced. In the simulation of work roll temperature field, the convert boundary condition and the transient thermal contact between the roll and strip were studied. Besides, the dynamic variation of the work roll temperature and the transient temperature distribution of the work roll during hot rolling were investigated. The calculated results were in good agreement with the measured data.

Heat Transfer Characteristic of Molten Pool for Twin-Roll Strip Casting

Body-fitted coordinate transformation equation was deduced and used to generate the body-fitted grids of molten pool for twin-roll strip casting.The orthogonality of the grids on the boundary was modified by adjusting source item.The energy equation and the boundary conditions were transformed from physical space to computational space.The velocity field model proposed by Hirohiko Takuda was used to calculate the temperature field of molten steel,and the influence of technical factors was also discussed.

FINITE ELEMENT ANALYSIS OF AXIAL FEED BAR ROLLING

A flexible technique of hot working of bars by axial feed rolling was introduced. The process deformation, strain field, stress field, and temperature fie M of the parts are analyzed by finite element method （ FEM）-simulation software DEFORM-3D. The material flow rule and tool load have been investigated.

Formation Mechanism in Alloy Steel Rolling Process Using Thermo-mechanical Coupling Method

Based on the theory of elastic-plastic finite element method, the high-speed hot continuous rolling process of a billet is simulated and analyzed in vertical and horizontal passes. The billet is dragged into the passes by contact friction force between the billet and rollers. The rollers and billet are represented by respectively rigid and deformable bodies, and three-dimensional models are developed for the billet and rollers. The distribution of deformation field, effective strain, rolling force and temperature field are accurately calculated for the whole rolling process （including unstable and stable stages）. In addition, the rolling pressure on the width symmetry center is compared with that in the in-situ experimental measurements. It is revealed that various heat exchange phenomena among the billet, rollers and surroundings can result in unbalanced temperature distribution on the cross section. Rolling force and strain can change significantly when the billet is moved towards or away from the roller gap, and keep almost invariable in the stable stage. It is expected that the simulation results would be useful for practical manufacture and provide the theoretical foundation for improvement of process planning and optimization of process parameters.

NUMERICAL SIMULATION OF MOLTEN POOL AND CONTROL STRATEGY OF KISS POINT IN A TWIN-ROLL STRIP CASTING PROCESS

Coupled turbulent flow, temperature fields of the twin-roll casting strip process were simulated by three-dimensional finite element method. Based on the heat balance calculation and using inverse methods between the simulations and real experiments, the relational models among casting speed, location, and coefficient of heat transfer between molten metal and rolls in different regions are given. In the simulation, the calculated surface temperatures are in good agreement with the measured values. An on-line model of kiss point is derived by simulations and the geometry of molten pool, corresponding control strategy is also proposed.

Variable Thermal Comfort Index for Indoor Work Space in Office Buildings: A Study in Germany

International standards state the thermal comfort requirements that office spaces must comply with. These are based on a model developed by Prof. Paul Ole Fanger of the Centre for Indoor Environment and Energy, Denmark. Today, forty-year research shows an evolution in these experiences. The work presented here is to develop a tool to evaluate the thermal comfort of working environments of office buildings. A methodology is devised on the basis of on-site measurements and questionnaire responses. For measurements, a mobile unit equipped with sensors is used, whereas the questionnaire obtains user responses on thermal quality of the work space. The thermal conditions of thirty office buildings presenting different acclimatization systems have been surveyed. The correlation between objective and subjective data allows developing a formula that shows the thermal comfort level for a given environment as a function of local aspects. For the surveyed buildings, the resulting comfortable temperature was 23.3℃, and the minimum percentage of user individuals experiencing discomfort with such temperature was 7%.

DS1820与LonWorks现场总线测温系统

本文介绍了单线制数字式温度传感器DS1820的测温原理、测温步骤以及工程应用中的几个实际问题,并结合LonWorks现场总线节点给出一个测量单点温度的例子,然后阐明了测量多点温度的方法。此实例可进一步推广到适合传感器温度量程的其它温度控制系统中去。

方坯直轧工艺下连铸坯温度场均匀性及切坯工艺优化

对方坯直轧工艺下连铸坯温度场和初生晶粒演化进行数值模拟,并根据计算结果对连铸坯切坯顺序进行优化。结果表明:随着连铸拉速的提高,连铸方坯表面温度和心表温差逐渐增大,心部等轴晶区也逐渐扩大;拉速对连铸坯初生晶粒取向的影响较小;连铸坯定尺对铸坯头尾温差的影响较大,在拉速不变的情况下,连铸坯定尺每增加1 m,头尾温差增大约10.5℃。方坯直轧工艺生产采用非定尺切坯策略,可以有效减小连铸拉速波动对出坯生产节奏的影响。

黏温黏压下径向柱塞泵滑靴副温度分布与泄漏量分析

针对高压大排量径向柱塞泵滑靴副摩擦失效和泄漏问题,以XDP1000型径向柱塞泵为例,对滑靴副温度分布与泄漏量进行了流场仿真和数值计算。首先,根据滑靴柱塞组件运动学特性分析,求解了滑靴偏转角变化规律,并通过建立滑靴副不同通道流量计算公式的方式,建立了滑靴副静压支承特性方程;然后,建立了滑靴副泄漏功率损失和摩擦功率损失模型,求解了滑靴副最佳油膜厚度,并分析了最佳油膜厚度的变化规律;最后,在考虑了油液黏温黏压特性的基础上,通过流场数值计算的方式,研究了滑靴副温度分布与泄漏量随径向柱塞泵工况参数的变化规律。研究结果表明:额定工况下,滑靴副最佳油膜厚度值约为14μm,滑靴副最佳油膜厚度值随着转子转角的增大而增大,随着工作压力和温度的增大而减小;滑靴运动方向侧油膜温度较另一侧高13 K,滑靴副温度值基本不受工作压力的影响,而随着转速的增大而升高;滑靴副阻尼孔泄漏量较滑靴边界泄漏量大0.02 kg/s,而且泄漏量随着压力、转速和油液温度的增大而增大。该研究结论可为高压大排量径向柱塞泵滑靴副设计及优化提供参考。

电塑性轧制加电装置设计及实验验证

为满足电塑性轧制中高能脉冲电流的高效传输和靶向作用,提出一种电塑性轧制加电装置,并利用ANASYS有限元分析软件对轧辊与轧件的电流场和温度场进行了仿真分析。通过变参数多工况模拟,研究了不同参数对电极与轧辊、轧辊与轧件接触处电流集中的影响、轧件塑性变形区内电流非均匀分布区的影响规律以及轧辊和轧件的温升情况。基于此,搭建了二辊电塑性轧制实验平台,并以AZ31镁合金板材为对象,验证了新的加电方案可以有效遏制AZ31镁合金轧制过程中边裂现象的发生,从而大幅度提升了镁合金板材的成形效率与质量。