Roll force,torque, lever arm coefficient,and strain distribution in edge rolling

Due to the growing importance of width control in strip and plate mills, edge rolling is currently an im-portant process in hot rolling mills. Research in edge rolling has been carried out, and in the present ar-ticle, models for roll force, torque, and lever arm coefficient are derived using the upper bound method. A simple, kinematically admissible deformation zone and velocity field, independent of friction in the roll gap, is proposed, and the energy dissipation rate is derived. The formula for energy dissipation rate has, in practice, no limitation because all edge rolling geometries are safely in the area where the formula is valid. Roll force and torque are derived by means of two independent integrals. Thus, the lever arm coef-ficient is evaluated from the expressions for roll force and torque using conventional rolling theory. Roll-ing trials report good agreement with theory. Measured roll forces are similar to calculated forces. Furthermore, the shape of the dogbone that arises during edge rolling is in fairly good agreement with the calculated dogbone shape. Deviations are due to the deviation from ideally plastic material in the ex-periments. Also, the strain distribution over the dogbone is similar to the proposed deformation zone. Thus, a new formula has been developed to a stage that it can be implemented in width control systems for edge rolling stands in hot strip and plate mills.     

宽带钢热连轧生产线自动控制系统综合设计及应用

宽带钢热连轧生产线是一套综合了机电液压系统的复杂大系统,自动控制系统是最大限度发挥轧线效能和生产高质量产品的重要保证。文章系统阐述了热连轧的特点及其对自动化系统的要求、自动控制系统设计思想、系统结构和配置。设计采用多级系统、各级间高速光纤以太网、高性能控制器间高速全局数据内存网、高性能控制器与现场设备间Profibus_DP网通信、L2级服务器热机备份策略、L1级光纤以太网冗余设计等创新的设计理念,以及拥有自主知识产权的L2级中间件系统、L2级关键数学模型和L1级核心控制模型。本文的设计思想及其基础上的控制系统已经在国内多条热连轧生产线上得到了成功应用。     

热连轧超快冷系统水压控制策略的开发与应用

以热连轧超快冷冷却水压力控制系统为研究对象,通过对超快冷压力调节阀组开口度与流量的分析,建立了超快冷压力调节阀组的调节效率方程。结合压力调节效率方程,开发了用于热连轧超快冷系统的低能耗、高效率的最优压力控制策略。现场应用结果表明：采用该最优压力控制策略,超快冷冷却水压力控制稳定,为低能耗、高效率生产提供了保障。     

热带精轧过程中温度变化规律的研究

为研究热连轧带钢终轧温度变化规律,给出了带钢轧制过程温度计算模型,分析了轧制速度、工作辊材质、带钢材质和工作辊温度对变形温升、接触温降和摩擦温升的影响,从而得到带钢轧制过程中温度变化的影响规律,为建立高精度热连轧带钢温度控制模型提供了理论依据.     

Numerical simulation and experimental verification of microstructure evolution in a three-dimensional hot upsetting process

The hot compression tests of 42CrMo steel were performed in the temperature range of 850–1150 °C at strain rates of 0.01–10 s^?1 and deformation degrees of 10–60% on Gleeble-1500 thermo-simulation machine. The optical microstructures in the center region of the section plane were examined. Based on the results from thermo-simulation experiments and metallographic analysis, the dynamic recrystallization mathematical models of 42CrMo steel were derived. The effects of processing parameters, including the strain rate and deformation temperature, on the microstructure evolution of 42CrMo steel hot upsetting process were discussed by integrating the thermo-mechanical coupled finite element method with the derived microstructure evolution models. The fraction of dynamic recrystallization and dynamic recrystallization grain sizes during the hot upsetting process of 42CrMo steel were predicted. The results show that the effects of strain rates and deformation temperatures on the microstructure evolution of 42CrMo steel hot upsetting process are significant, and a good agreement between the predicted and experimental results was obtained, which confirmed that the derived dynamic recrystallization mathematical models can be successfully incorporated into the finite element model to predict the microstructure evolution of hot upsetting process for 42CrMo steel.     

Mechanism and kinetics of coagulation of γ′-phase in nickel alloys at temperatures of hot plastic deformationin nickel alloys at temperatures of hot plastic deformation

It is known that hot plastic deformation of hard-to-deform complexly alloyed heat-resistant nickel alloys is easier to conduct at temperatures of the double-phase region than at those of the single-phase region. In heating such alloys before deformation and in the process of deformation cooling of them the amount of strengthening γ^′-phase and its sizes and distribution change, which exerts a substantial effect on their susceptibility to hot plastic deformation in the double-phase range. For this reason, knowledge of the laws of variation of the amount, dispersity, and distribution of the strengthening γ^′-phase in heating to the deformation temperature is very important, because it makes it possible to control these processes. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 3, pp. 11–13, March, 1997. Deceased.     

热连轧带钢生产线计算机控制系统的研发与应用

针对全连续热轧带钢生产线，在开发核心的轧制数学模型的基础上，在过程控制级实现了高精度的模型设定和模型自学习功能，在基础自动化级实现了自动宽度控制和自动厚度控制，最终搭建了功能完备的两级计算机控制系统，实现了热轧产品的高精度控制。现场实际应用效果表明，自动化控制系统的稳定运行率达到了99%以上，针对不同的产品规格，厚度控制精度在±25 μm范围内，宽度控制精度在0~3 mm范围内达到99%以上，实现了产品的高精度控制。     

钛铝复合板热加工图及热轧实验

采用Gleeble-3500热模拟试验机进行高温等温压缩实验,研究了爆炸焊接钛铝复合板在变形温度为300~500 ℃、应变速率为0.1~10 s^-1条件下的热变形行为,利用动态材料模型构建了钛铝复合板热加工图,并基于热加工图进行了钛铝复合板热轧工艺验证实验。结果表明：钛铝复合板属于正应变速率敏感材料;在热加工图中变形温度为420~460 ℃、应变速率为1.6~6.3 s^-1时,功率耗散效率达到0.64~0.72,该区域对应的工艺参数适合进行钛铝复合板热轧;热轧后实验板材界面结合良好,具有良好的力学性能和钣金成形性能。钛铝复合板在热轧过程中的变形机制为：变形抗力低、流动快的铝层在自身发生塑性变形的同时牵引着钛层一起发生塑性变形,其中铝层是热变形,钛层为冷变形。     

Hot and cold rolling of high nitrogen Cr-Ni and Cr-Mn austenitic stainless steels

Behavior of austenitic Cr-Ni-(0.14-0.50)N and Cr-Mn-(0.78-1.00)N steels in hot and cold rolling was investigated by rolling experiments and mechanical testing. Structure of the steels in the as-cast condition and fracture surfaces after the rolling experiments were investigated using optical and scanning electron microscopy (SEM). Resistance to deformation was calculated using rolling forces in hot rolling. Increase in strength in the rolling experiments was related to the nitrogen content of the steels. Resistance to deformation during hot rolling increased with decreasing rolling temperature and with increasing nitrogen content. In some steels, hot rolling led to edge cracking, which was more a function of impurity than nitrogen content. Microscopy revealed that the edge cracking occurred along grain boundaries and second phase particles. For the cold-rolled steels, the highest achievable reductions were limited due to a “crocodiling” phenomenon, that is, opening of the strip end. Fracture type at the opened strip end was a brittle-like fracture.     

Constitutive modeling of hot deformation behavior of X20Cr13 martensitic stainless steel with strain effect

Hot deformation behavior of X20Cr13 martensitic stainless steel was investigated by conducting hot compression tests on Gleeble–1500D thermo-mechanical simulator at the temperature ranging from 1173 to 1423 K and the strain rate ranging from 0.001 to 10 s^?1. The material constants of α and n, activation energy Q and A were calculated as a function of strain by a fifth-order polynomial fit. Constitutive models incorporating deformation temperature, strain rate and strain were developed to model the hot deformation behavior of X20Cr13 martensitic stainless steel based on the Arrhenius equation. The predictable efficiency of the developed constitutive models of X20Cr13 martensitic stainless steel was analyzed by correlation coefficient and average absolute relative error which are 0.996 and 3.22%, respectively.     

基于动态再结晶动力学方程的镍基高温合金热变形流变应力预测

采用等温热压缩实验,研究了一种典型镍基高温合金在1010-1160oC及0.001-1s-1条件下的高温流变行为。结果表明在合金的高温变形过程中发生了动态回复(DRV)以及动态再结晶(DRX)现象。通过深入分析不同变形条件下合金的高温流变行为,分别建立了合金在加工硬化-动态回复阶段以及动态再结晶阶段的流变应力本构方程。其中,在动态再结晶阶段,流变应力本构方程的建立是基于一种新型的动态再结晶动力学方程,该方程中引入了最大软化速率应变。此外,采用线性拟合的方法,建立了本构方程中材料常数与Zener-Hollomon参数间的函数关系。同时,通过对比分析流变应力的实测值和预测值,并计算两者之间的相关系数(R)和平均相对误差绝对值(AARE),验证了所建立本构方程的准确性,它可以精确预测所研究合金的高温流变应力。     

A new method for determining dynamic grain structure evolution during hot aluminum extrusion

In this paper, a new method for analyzing the microstructure evolution of aluminum during deformation at elevated temperatures by extrusion is presented, which is entirely separated from secondary restoration effects viz. static recrystallization and grain growth. In order to observe the development of grains and their orientation under severe plastic deformation, a small-scale forward extrusion setup was designed which allows quenching the extrusion butt together with the die and the container immediately after extrusion to preserve the grain structure evolved during the deformation. The forming path and the forming history of a selected material point were calculated by numerical simulation. The evolution of the microstructure along the forming path was analyzed using electron backscatter diffraction. A database for the development of physically based phenomenological models for predicting and simulating the evolution of microstructure during the hot deformation of EN AW-6082 alloy is provided.     

Optimization of microstructure development: application to hot metal extrusion

A new process design method for controlling microstructure development during hot metal deformation processes is presented. This approach is based on modern control theory and involves state- space models for describing the material behavior and the mechanics of the process. The challenge of effectively controlling the values and distribution of important microstructural features can now be systematically formulated and solved in terms of an optimal control problem. This method has been applied to the optimization of grain size and certain process parameters such as die geometry profile and ram velocity during extrusion of plain carbon steel. Various case studies have been investigated, and experimental results show good agreement with those predicted in the design stage.     

中宽带热连轧计算机控制系统

根据热轧中宽带钢生产线的特点,给出了其自动控制系统的计算机配置和通讯方案;提出了出粗轧区轧机及辊道的速度控制和电动APC控制策略;将磁致位移传感器成功地应用到轧制生产中,提高了辊缝测量精度;给出了粗轧全自动控制方案和程序设计;针对活套起套速度设定不当可能引起带钢“颈缩”现象,提出了活套“软接触”解决方案;介绍了精轧机组无活套机架和粗轧机组模糊微张力控制的方法。     

TB6钛合金热变形行为及本构模型研究

研究材料的热变形行为及建立其本构模型是进行材料加工与模拟的基础。通过对TB6钛合金热变形行为分析,表明流变应力受应变速率的影响较显著,而变形温度对流变应力的影响程度与应变速率的大小有关。采用Arrhenius型双曲正弦方程建立了TB6钛合金流变应力本构模型。研究变形条件对TB6钛合金流变应力的影响。结果表明,可通过控制应变速率和变形激活能来控制热加工的应力水平和力能参数,为TB6钛合金塑性加工过程控制和模拟提供前提条件。     

Flow stress prediction of Hastelloy C-276 alloy using modified Zerilli−Armstrong,Johnson−Cook and Arrhenius-type constitutive models

To better understand the hot deformation behaviors of Hastelloy C-276 alloy under elevated temperatures, hot tensile tests were carried out in the temperature range of 1223−1423 K and the strain rate range of 0.01−10 s⁻¹, respectively. Based on the modified Zerilli−Armstrong, modified Johnson-Cook, and strain-compensated Arrhenius-type models, three constitutive equations were established to describe the high-temperature flow stress of this alloy. Meanwhile, the predictability of the obtained models was evaluated by the calculation of correlation coefficients (r) and absolute errors (Δ), where the values of r for the modified Zerilli−Armstrong, Johnson−Cook, and Arrhenius-type constitutive models were computed to be 0.935, 0.968 and 0.984, and the values of Δ were calculated to be 13.4%, 10.5% and 6.7%, respectively. Moreover, the experimental and predicted flow stresses were compared in the strain range of 0.1−0.5, the results further indicated that the obtained modified Arrhenius-type model possessed better predictability on hot flow behavior of Hastelloy C-276.     

GH4169合金涡轮盘热模锻中晶粒尺寸演变的数值模拟与分析

针对GH4169合金涡轮盘热模锻中易出现粗晶、混晶等显微组织缺陷,通过热模拟压缩实验和热变形后热处理实验,研究分析了GH4169合金在热变形和后续热处理中的显微组织演变规律,并建立了晶粒尺寸演变模型。实验结果表明:GH4169合金在热变形中的主要显微组织演变机制为动态再结晶,热变形后热处理中的主要显微组织演变机制为晶粒长大和孪晶生成。将晶粒尺寸演变模型与有限元结合,对某GH4169合金涡轮盘热模锻中的晶粒尺寸演变进行了预测分析,预测结果与实际结果一致。     

Quantitative description of the flow-stress dependence of aluminum alloys at the stage of steady flow upon hot deformation on the Zener–Hollomon parameter

The deformation behavior of a 1981 aluminum alloy has been studied using a complex for simulating thermomechanical processes in the temperature range of 200–400°C at a deformation rate in the range of 0.001–10 s^–1. The models of the relationships between the flow stress, temperature, and deformation rate have been constructed using a power-law dependence, exponential dependence, and hyperbolic-sine function on the Zener–Hollomon parameter (Z). In the calculations according to the power-law and exponential equations, discrepancies between the calculated and experimental values of the Zener–Hollomon parameter have been revealed at low and high values. These discrepancies are caused by the fact that the experimentally obtained dependences of the flow stress on the Z parameter over the entire range of its change with a single magnitude of the effective activation energy of the plastic deformation consist of two linear parts that correspond to the hot and warm deformation and have different magnitudes of the effective activation energy of plastic deformation with a lower value of the activation energy for hot deformation.