整辊内嵌式板形检测辊瞬态温度场与应力场分析

 在冷轧可逆轧制的不同道次,与板形检测辊接触的带钢温度差异显著,使得检测辊的温度场和应力场不稳定。运用有限元软件ANSYS建立了板形检测辊的热力耦合模型,分析了轧制过程中板形检测辊的瞬态温度场和应力场。结果表明,轧制开始后接触带钢的热量由辊体外表面向内表面逐渐传递,传感器正上方的辊体外表面温度上升最快,并在1940s达到温度最大值135℃;骨架顶部与辊体内孔面的接触热阻使传感器的温度上升较慢,骨架顶部在 2280s达到温度最大值134℃;板形检测辊的最大应力发生在与骨架顶部接触的辊体内孔面上,其在940s达到最大值301MPa,满足材料强度的许用应力要求。通过模拟分析结果与现场实测数据对比,证明了有限元分析模型的正确性。     

热连轧轧辊瞬态温度场研究

考虑水冷、空冷、轧辊与轧件接触热传导等动边界条件，采用有限差分法，建立了热连轧轧辊瞬态温度场变步长分析计算模型。该模型能实现轧辊温度场的动态分析和精确计算，预测轧制时以及终轧后空冷的轧辊瞬态温度场。试验和仿真结果表明，所建立的分析计算模型考虑因素全面、合理，计算精度较高，计算值与实测值吻合良好，真实地反映了轧辊的温度变化情况。     

Two-Dimensional Transient Temperature Field of Finish Rolling Section in Hot Tandem Rolling

Comprehensively considering the factors such as descaling cooling, air cooling, watercooling, frictional heat and deformation heat in gap of every stand, heat conduction betweenwork roll and strip etc, a model of two-dimensional transient temperature field of finish rollingsection in hot tandem rolling was built with finite difference method to calculate the temperaturefields of strip and work roll. So two-dimensional accurate analysis and calculation of strip tem-perature were realized, and the theoretical basis for predicting and controlling strip temperaturewas provided. The simulated results show that the model is practical and reliable.     

Thermomechanical Behavior of Work Rolls During Warm Strip Rolling

A mathematical model was developed to assess thermomechanical behavior of work rolls during warm rolling processes. A combined finite element analysis-slab method was first developed to determine thermal and mechanical responses of the strip being rolled under steady-state conditions, and then, the calculated roll pressure and temperature field were utilized as the governing boundary conditions for the thermomechanical problem of the work roll. Finally, the thermomechanical stresses within the work rolls were predicted by a thermoelastic finite element approach. The results of the model indicate that, in warm strip rolling, thermal and mechanical stresses developed in the work rolls are comparable, and thus, both thermal and mechanical aspects of the problem should be considered in such a problem. Besides, the model was shown to be capable of determining the effects of various rolling parameters on the thermomechanical behavior of the work rolls during warm rolling process.     

基于多目标遗传算法的工作辊温度场计算与分析

等效换热系数是热连轧机工作辊温度场仿真模型的核心输入参数,多采用遗传算法优化得到,某1800 mm 热连轧机存在品种、规格交替轧制,等效换热系数的准确计算比较困难.选取多组典型工艺条件下的工作辊下机后表面温度作为优化目标,采用多目标遗传算法进行优化,并通过改变遗传算子有效避免了算法早熟及局部收敛等问题,获取了具有较强适应性的等效换热系数.仿真和实测数据的对比结果证明了优化模型的可靠性.利用仿真模型分析了主要工艺参数对工作辊热凸度的影响,并提出同宽交替时,工作辊热凸度随轧制进程呈指数变化,而在品种、规格交替编排轧制工艺下相邻带钢轧制时工作辊热凸度存在6-21.8μm 的波动,且随轧制进程趋于稳定.      

平整轧制过程中工作辊粗糙度衰减模型

 针对以往平整工序工作辊表面粗糙度衰减模型仅仅考虑轧辊材质与轧制公里数影响,而忽略所平整带钢的特性以及轧制压力等工艺参数作用,造成辊面实际粗糙度预报误差较大以致影响成品带钢表面粗糙度的控制精度问题,充分结合平整轧制过程的设备与工艺特点,通过大量的理论研究与现场试验,在从微观层面分析了平整轧制过程中工作辊表面粗糙度衰减机理的基础上,不但考虑到工作辊表面硬度、表面原始粗糙度的影响,而且考虑到平整轧制过程中的单位轧制压力及单位摩擦应力的作用,建立了一套适合于平整轧制的工作辊表面粗糙度衰减模型,编制出了相应的工作辊表面粗糙度预报软件,并将其应用到某1 420平整机组的生产实践,取得了良好的使用效果,提高了成品带钢表面粗糙度的控制精度,为机组创造了较大的效益,具有进一步推广应用的价值。     

面向辊形磨削的热带钢连轧机工作辊热变形研究

热带钢连轧机工作辊下机后尚未完全冷却即进行磨削,残存的不均匀热变形导致磨削的工作辊辊形在空冷一段时间上机时很难达到工艺设定值.针对热辊形不易测量的特点,制定合理的物理测量方式,准确地测量了工作辊下机后的温度分布和热辊形.考虑复杂的工作辊换热边界条件,采用有限差分法对工作辊空冷时的温度场和热变形进行了数值模拟,计算结果与测试结果吻合良好.对工作辊下机后不同时刻的热变形进行仿真,通过将目标上机辊形和磨削时热辊形叠加来设定磨削辊形,为实现合理的辊形磨削提供了依据和计算方法.     

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.     

A thermal elastic-plastic finite-element analysis to roll-life prediction on the twin roll strip continuous casting process

The rolling force and roll deformation behavior in the twin-roll-type strip continuous casting process have been computed to estimate the thermal characteristics of a caster roll. To calculate the rolling force, the relationship between the flow stress and strain for a roll material and a casting alloy are assumed as a function of the strain rate and temperature, because the mechanical properties of casting materials depend on temperature. The three-dimensional (3-D) thermal elastic-plastic analysis of a cooling roll has also been carried out, to obtain roll stress and plastic strain distributions, with the commercial finite-element analysis package of ANSYS. Temperature field data for a caster roll, provided by the authors, were used to estimate the roll deformation. Therfore, numerical models considering the thermal and rolling forces have been developed to estimate the roll life. Roll life considering the thermal cycle is calculated using thermal elastic-plastic analysis results. The roll life is proposed in terms of roll revolution in the caster roll models with and without the fine crack failure on the roll surface. To obtain plastic strain distributions of the caster roll, thermomechanical properties of a roll sleeve with a copper alloy are obtained by a uniaxial tensile test for variation of temperature. The proposed analysis techniques have improved in caster roll design.     

基于遗传算法的工作辊温度场参数优化模型

针对热连轧机工作辊热辊形计算中温度场模型的热交换等参数难以确定的问题 ,建立了基于遗传算法的参数优化模型 ,可以解决复杂条件下的热参数的求解问题。利用优化参数计算的轧辊温度场与实际测量结果一致。     

热轧带钢传热模拟及变形区换热系数的确定

采用数值模拟方法研究了带钢热轧区轧件传热和温度场分布规律.结合现场生产中测温数据,建立了轧制变形区内轧件与轧辊接触传热界面换热系数(HTC)统计模型.分析了辊缝变形区中轧件断面上温度演变和分布特点.研究结果表明,热轧带钢热轧区传热数值模拟计算结果与实际吻合良好;变形区内轧件与轧辊接触传热界面换热系数不仅与平均单位压力相关,而且与轧制速度相关;轧件在轧制变形区存在很大的温度梯度.     

FEM Calculation of Work Roll Temperature and Thermal Crown

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 thermalstructural 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.     

Thermal Scratch on Surface of SUS430 Stainless Steel Strip in Cold Rolling Process

The thermal scratch significantly influences the surface quality of the stainless steel in cold strip rolling.The thermal scratch has a close relation to the rolling parameters,the rolls surface and the emulsions used in rolling.In order to explain the thermal scratch on the strip surface,the cold rolling process of SUS430stainless steel strip was investigated in the laboratory.The thermal scratch defect occurs frequently in the second rolling pass(maximum reduction in height is 32.3%),especially on the lower surface of strips.When concentration and temperature of the emulsion are the same,the thermal scratch on the surface of the strip is aggravated with increasing the roll surface roughness.With the same roll surface roughness and emulsion concentration,the thermal scratch is obviously more severe at an emulsion temperature of 63℃than 55℃.With the same roll surface roughness and emulsion temperature,the thermal scratch is distinctly weaker at the emulsion concentration of 6%than that of 3%.     

热连轧工作辊热平衡的优化研究与应用

轧辊热膨胀对承载辊缝形状和带钢板形具有显著的影响,而准确预报轧制过程中轧辊热膨胀是板形控制中的难点之一。针对某热连轧生产线单辊期内热膨胀量与轧辊温度不收敛的问题,利用自主开发的与产线生产完全一致的板形模型分析测试系统对热凸度二级模型进行了仿真分析与研究,提出了一种有效提高工作辊热平衡收敛性的优化方法,并进行了生产应用。该优化方法的应用解决了该热轧产线单辊期内热平衡不收敛的问题,消除了轧辊温度计算值和实测值之间的偏差,不仅提高了模型的预报精度,也大幅提高了该产线轧制带钢的凸度控制精度。     

Measurement of Thermal Load on Working Rolls during Hot Rolling

Work rolls in hot rolling mills are thermally and mechanically loaded; both of these loading aspects are difficult to measure. Laboratory tests can be used for the specification of the thermal load in the cooling area; however a thermal load in a roll gap is still difficult to measure. The paper describes an experimental technique developed for monitoring the work roll surface temperature by sensors embedded in the work roll. Continuous hot rolling pilot line trials were performed for different process conditions. One parameter, for example, roll cooling, rolling velocity, reduction, or skin cooling, can easily be changed during the trials, and the effect on the thermal cycle of the work roll can be directly measured. These thermal measurements give very detailed information about the temperature field. An inverse heat‐conduction model has been developed to compute the surface boundary condition from the measured temperatures. The heat flux and heat transfer coefficient distribution along the roll circumference can be obtained afterwards. The results for different rolling velocities and reductions (up to 50%) are shown.     

Effects of interface resistance on heat transfer in steel cold rolling

The thermal contact resistance created in the bite region during rolling depends on surface roughness, contact pressure, and the coolant, lubricant or oxide scale between the roll and strip. Therefore, to estimate temperatures of the roll and the strip accurately, the interface resistance in the contact region should be considered when modelling. The purpose of this study is to more effectively analyze the thermal behaviour of the steel rolling process by considering the interface resistance of the roll and strip in the contact region. Since the interface is very thin in comparison with its length, it is modelled as one-dimensional heat transfer with friction heat generated along the interface. For the estimation of the thermal contact resistance, different surface situations of cold rolling are considered. The finite element method is adopted to evaluate the deformation and friction power dissipated in the rolls and strip during rolling process. Roll and strip thermal properties, such as thermal conductivity and specific heat, are considered to be temperature dependent during the calculation.     

宝钢150t超高功率直流电弧炉用耐火材料

介绍、讨论了宝钢１５０ｔ超高功率直流电弧炉耐火材料的设计特点,以及投产一年多来的使用情况,并根据操作经验认为：（１）造成泡沫渣埋弧操作非常关键;（２）镁铝尖不石底电极套筒砖性能优越;（３）冷态下底电极套砖接长修补是可行的;（４）采用高钙、低硅,适量的铁的烧结镁砂制成的炕底捣打料性能良好;（５）采用热态修补出钢口技术能大大延长出钢口砖寿命;（６）小炉顶的材质建议采用镁碳砖环状砌筑。     

热轧薄带平整机支撑辊辊型优化的研究与应用

某热轧薄带平整机轧辊长度为1 800 mm,带钢宽度为1 320 mm,两者相差太大,造成工作辊与支撑辊间有害接触区长度过大,在轧辊自身挠度作用下,辊间应力峰值集中于带钢边部位置.随轧制公里数延长,工作辊边部磨损加剧,不利于后期板形控制,同时会缩短轧辊使用寿命.针对热轧薄带平整机工作辊磨损不均匀问题,设计优化支撑辊辊型...     

轧辊温度场及轴向热凸度有限元计算

采用大型有限元分析软件 ANSYS对四辊轧机工作辊的温度场进行了模拟 ,在模拟过程中 ,考虑了轧辊和轧件间的瞬态热接触和对流边界 ,动态分析了热轧时工作辊的升温过程 ,预测了工作辊的瞬态温度分布 ,并将所得的温度分布用于热凸度的近似计算中 ,其计算结果与文献结果相吻合     

New Method for Evaluating Thermal Wear of Rolls in Rolling Process

A new method was developed by a thermal wear machine to evaluate the thermal wear of roils in steel rolling process. The steel strip and rolls were simulated by upper and lower heating disks. The upper heating disk could he kept at a temperature of over 900 ℃ by induction heating. The pressure between the disks as high as 323.2 MPa could be achieved and the slipping rate could be 12. 7 %. The thermal wear of high speed steel （HSS） roll material, the wear rate of the HSS roll, and the SEM morphology of a worn HSS roll surface were investigated. This method was useful and could be employed to simulate friction and wear between strip and roll during the strip rolling process.