Characteristics of unsteady lubrication film in metal-forming process with dynamic roll gap

Based on the theory of unsteady hydrodynamic lubrication and relevant mathematic and physical methods, a basic model was developed to analyze the unsteady lubrication film thickness, pressure stress and friction stress in the work zone in strip rolling. The distribution of pressure stress and friction stress in the work zone was obtained. A numerical simulation was made on a 1850 cold rolling mill. The influence of back tension stress and reduction on the distribution of pressure stress and friction stress between the roll gaps was qualitatively analyzed by numerical simulation. The calculated results indicate that the higher the back tension, the lower the pressure stress and the friction stress in the work zone, and the largest friction stresses are obtained at the inlet and outlet edges. The pressure and friction gradients are rather small at high back tension. The pressure-sensitive lubricant viscosity increases exponentially with the increase of pressure. The unsteady lubrication phenomenon in the roll bite is successfully demonstrated.

Identification and optimization for hydraulic roll gap control in strip rolling mill

In order to improve the control performance of strip rolling mill, theoretical model of the hydraulic gap control(HGC) system was established. HGC system offline identification scheme was designed for a tandem cold strip mill, the system model parameters were identified by ARX model, and the identified model was verified. Taking the offline identified parameters as the initial values, online identification using recursive least square was carried out with model parameters changing. For the purpose of improving system robustness and decreasing the sensitivity due to model errors, the HGC system based on generalized predictive control(GPC) was designed, and simulation experiments for traditional controller and GPC controller were conducted. The results show that both controllers acquire good control effect with model matching. When the model mismatches, for the traditional controller, the overshot will increase to 76.7% and the rising time will increase to 165.7 ms, which cannot be accepted by HGC system; for the GPC controller, the overshot is less than 8.5%, and the rising time is less than 26 ms in any case.

Roll Gap Crown Adjustment Characteristics of 1700 mm Cold Rolling Mills

The 4-hi cold mill is one of the key wide strip tandem cold rolling mills and has many advantages and characteristics. The mill type is the most important, fundamental and long-term effective factor for the strip shape control. Many advanced mill types such as CVC-4, HCW and PC-4, etc are created based on the conventional four-roll mill. The factors of mill type which affect the deformation of roll system, such as strip width, rolling force, bending force, work roll diameter, backup diameter and so on, arc studied how to affect roll gap crown. It provides a good foundation lbr improving the shape performance of mill.

Roll gap prediction in acceleration and deceleration process of cold rolling based on a data-driven method

Severe fluctuation of the effective roll gap in the acceleration and deceleration section of the cold rolling process is a significant factor causing thickness deviation.However,the conventional roll gap compensation method and control strategy do not meet the stringent strip quality requirements.The roll gap model in the acceleration and deceleration process is studied to increase the thickness control precision.In order to improve model accuracy,a roll gap prediction method based on data-driven is proposed.Given the complexities of the cold rolling process,the extreme gradient boosting(XGBoost)method is used to predict the roll gap model as the rolling speed changes.Meanwhile,support vector regression and neural network-based methods are taken to evaluate and compare the prediction performances.Based on the field data,the simulation experiments are carried out.It demonstrated that the prediction performance of the proposed method outperformed the other two methods.The values of root mean square error,determination coefficient value,mean absolute percentage error and mean absolute error obtained from the XGBoost model were equal to 0.000346,0.952,7.02,and 0.00028,respectively.In addition,the proposed method analyzed the contribution rates of the rolling affecting parameters on the roll gap.The data showed that in the controllable rolling parameters,the rolling speed is the most impacting factor that disturbs the roll gap model in the acceleration and deceleration process,which can provide a useful direction for actual roll gap adjustment.

Analysis of Roll Gap Pressure in Sendzimir Mill by FEM

The acting force on the roll system of Sendzimir mill was analyzed using 3D FEM.The roll gap pressure distribution and the acting force between rolls S and O,rolls O and I,rolls O and J,rolls I and A,rolls I and B,as well as rolls J and B were analyzed.The results showed that the roll gap pressure mainly affected the roll surface layer,50 mm for backup roll;the roll gap pressure distribution is of double peaks among the work roll,the 1st intermediate roll（IMR）,and the 2nd IMR;the maximum value of the roll gap pressure between the backup roll and the second IMR appears on the edge of the barrel of rolls;the component force presents the in-para-curve distribution.These are important for reducing the wear of rolls and the break of the backup roll and guiding for production.

基于板带厚度误差PI反馈的轧机辊缝调节方法

针对轧机刚度系数未知波动影响板带厚度控制精度的问题,提出了基于板带厚度误差PI反馈的轧机辊缝调节方法。首先,建立轧机弹跳方程、液压辊缝调节动态方程,以及从辊缝设定值到板带出口厚度的动态方程;其次通过测厚仪和测压计,获取轧机出口处的板带厚度,以及轧机施加的轧制压力;然后设计基于板带厚度误差量PI反馈的辊缝大小的设定值,同时引入比例反馈增益系数与积分反馈增益系数的单参数化设计;最后将辊缝大小的设定值输入轧机液压辊缝调节系统进行辊缝调节,最终形成一套完整的轧机辊缝调节方法。该方法提高了轧制参数的预设定精度,大大减小了轧机刚度系数波动对板带厚度控制精度的影响,从而提高了板带厚度精度。

1180 MPa级超高强钢冷连轧过程的厚度综合控制技术

针对超高强钢在冷轧过程中厚度波动大以及带头带尾厚度超差的问题,首先根据金属秒流量模型建立了厚度超差预测模型与辊缝调节量预估模型;随后开发了轧制过程中的厚度控制系统,并进行了辊缝调节量优化;最后建立了带钢头尾轧制过程中的轧制速度与张力优化模型。以国内某冷连轧机组的第1机架为技术应用对象,选择两种典型的超高强钢进行生产测试,测试结果表明:超高强钢AR4146E1与DU6220A1的厚度超差长度分别从70.3 m、36.89 m下降到了16.85 m、16.33 m。

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.

基于GAP单元的滚动轴承应力分析

利用有限元分析软件MSC.Marc/Mentat对某一滚动轴承进行有限元分析,采用GAP单元代替滚动体模拟轴承内外圈间的接触,在某组载荷工况下,计算该简化模型的应力结果;在同组工况下,对比实体轴承模型与GAP单元简化模型的有限元分析结果,对比各自的最大应力值;同时用理论计算方法计算轴承在相同工况下的最大应力值,来验证有限元结果的正确性。结果表明:GAP单元可以有效的模拟滚动轴承内外圈之间的接触,从而为滚动轴承建模及与轴承连接的组合件之间的建模提供了一种简便且有效的方法。

TB水电站大坝廊道层施工技术研究与应用

TB水电站大坝为碾压混凝土重力坝,坝高158 m,大坝在高程1586、1640、1695 m布置了低中高3层廊道。大坝廊道层廊道模板安装后,大仓面被分隔为多个独立仓面,加上底层廊道与固结灌浆的干扰,廊道层碾压混凝土施工是大坝施工难度最大、直线工期最长的一个升层。TB水电站通过在固结灌浆、廊道备仓、“穿”廊道等工艺工序技术创新,有效加快了廊道层施工速度,仅20d完成大坝中部廊道层碾压混凝土施工。

辊轴式残膜打包装置的设计与试验

【目的】针对国内现有残膜打包装置成捆机理不明确、作业时出现残膜逃逸、膜包杂质含量过高等问题,设计一种集残膜清杂及残膜打包为一体的辊轴式残膜打包装置。【方法】该装置主要由清杂输送机构、打包机构、传动系统等组成。通过理论分析建立清杂输送辊与残膜的力学关系,确定清杂输送辊的结构参数;根据清杂输送机构结构特征与作业原理,分析并确定清杂输送辊的布置间隙。采用机理分析方法分析残膜捆芯形成过程中残膜的受力与运动情况,并确定打包辊的运动参数。以成捆率和膜包含杂率为指标,机具前进速度、清杂输送机构倾斜角度、打包辊转速为试验因素进行正交试验,并对较优的参数组合进行田间验证试验。【结果】影响成捆率的主次因素依次为打包辊转速、清杂输送机构倾斜角度和机具前进速度;影响膜包含杂率的主次因素依次为清杂输送机构倾斜角度、机具前进速度和打包辊转速。以成捆率为主要指标,确定的较优作业参数组合为:清杂输送机构倾斜角度为10°、机具前进速度为1.5 m/s、打包辊转速为200 r/min。田间验证试验的膜包成捆率为98.1%、膜包含杂率为15.2%。【结论】该残膜打包装置满足田间作业要求,作业效果好,可为辊轴式残膜打包装置的设计与研究提供参考。

Accu Roll轧管机上导盘与左轧辊之间间隙的计算

根据空间解析几何的基本理论,推导了AccuRoll轧管机的上导盘与左轧辊之间间隙的计算公式,并结合某厂实际情况进行了计算分析,为解决该轧管机在生产实际中存在的产品内螺旋道,轧制速度不高,轧制薄壁管时导盘寿命低等问题,以及实现导盘和轧辊等工艺参数的优化设计和最佳调整提供了理论依据。

卷取机助卷辊自动控制策略优化分析

通过分析卷取机助卷辊工作状态及控制方式,提出助卷辊控制策略。通过卷取机助卷辊安装精度调整、辊缝自动标定功能改进、助卷辊张力控制准确设定、自动跳步控制合理选择、助卷辊压尾控制等策略优化,有效解决了薄板生产过程中带钢头尾部卷取形状较差及压痕过大等问题,提升了薄板生产效率和卷取质量,为薄板后续加工提供可靠的保障。

白象山选矿厂提高产能优化实践

白象山选矿厂为了进一步提高生产效率和产能,针对精矿产品质量、生产作业率等指标进行了生产流程优化,提高设备利用率,采用先进生产设备等研究。通过循环使用淘洗机尾矿溢流水,减轻了尾矿大井负荷,提高了磁选机的选别效果,同时优化湿式筛分预选工艺筛孔尺寸,提高了选厂处理能力;通过优化高压辊辊缝及频率等参数,使用新型侧挡板,延长了高压辊辊面的使用寿命,提高了设备利用率;通过使用凿岩台车、深孔钻机等智能采矿设备,改善了选厂给矿状况。现场生产实践表明,通过上述措施优化,有效提高了白象山选厂的产能。

基于有载辊缝模型的热轧带钢边鼓缺陷研究

针对热连轧精轧带钢边鼓缺陷问题进行分析,结合轧辊弹性变形的相关理论,建立综合影响因素模型,并提出优化轧制计划编排、细化管控温度制度、合理安排轧制规程和优化设计工作辊与支撑辊辊型等治理措施。经过模拟板形曲线的验证,带钢的某机架出口板形值显著降低,带钢的边浪及边鼓现象有所改善,实现了带钢板形质量的提升。

辊缝标零技术在型钢轧机上的应用

型钢生产正在向标准化和自动化的连轧方向发展,但组成连轧机组的短应力线轧机的辊缝标零技术是其中的一个瓶颈——辊缝标零功能是短应力轧机不能采用液压伺服缸进行辊缝压下操作,应用液压伺服缸的牌坊式轧机又存在投入大,实现线下装配工序复杂且不易实现,伺服液压缸液压接头反复拆装不利于其精确使用的问题。因此投入少,标零功能操作灵活、高效是短应力轧机需要解决的问题。

宽厚板轧机使用轧制力测力仪若干问题分析及处理

宽厚板轧机使用轧制力测力仪测量轧制力,可以在生产中调节、控制板材的厚度和板形。对于宽厚板轧机,轧制力压头的测量力值巨大,因此在使用过程中容易出现异常情况。本文介绍了轧制力测力仪压头结构及安装的注意事项,对于轧制力压头使用过程中,轧机刚度系数异常、辊缝间隙波动异常等问题进行了分析处理。

连铸机扇形段控制模式的转换

本钢炼钢厂6#板坯连铸机扇形段控制模式分为收缩辊缝和扇形段轻压下控制技术两种模式。本文分析了板坯铸机在两种控制模式转换过程中,铸机拉矫力过大造成拉不动板坯,严重时发生冻坯事故的原因及解决办法,通过优化扇形段控制过程,解决了两种控制模式转换时发生问题的现象。

一种图像处理的汽车用棒材轧制孔型深度检测方法

目前国内棒材轧制孔型深度的检测,全部依靠人工卡量,不同的人员测量,会导致不同的结果,进而可能会导致辊缝设置存在较大的偏差。为实现上述孔型深度的自动测量目的,文章研究了一种以标准对比磁棒为标本、平行光源光学成像为手段、图像处理技术为基础的棒材机架孔型深度检测方法,以及相关的数学建模及算法。上述方法能够兼顾现场换辊操作及生产准备的便利性和精度,具有精度高、操作方便的特点。现场实验表明,以图像处理为基础的孔型深度检测方法,其实测精度可以达到0.2 mm以内,且比较稳定,对指导实际工业生产具有一定的实际应用价值。

调整轧机轴承座与机架间隙的智能衬板研究

轧机装备的稳健运行是充分发挥设备潜在能力,提高板带材质量的重要保证。轧机结构的动态特性是保证轧机稳健运行的前提,按“微尺度静定”设计理论分析得知,轧辊轴承座与机架窗口立柱之间存在约1 mm微小间隙易使辊系处于静不定状态,进而产生辊间错位及交叉工况。通过有限元方法分析了间隙和偏移距对轧辊两端支反力的影响,并设计了一种用于安装在轧机牌坊和上工作辊轴承座之间的液压智能衬板。经分析发现,轧辊两端支反力不相等的原因根源在于支承辊与工作辊之间的交叉角,而交叉角来源于轧机轴承座与机架之间的“不得已”间隙。通过开发智能衬板可以实现零间隙控制,保证轧机轧辊平行定位稳定且可靠运转,从而释放了轧机的潜能,为轧机非线性动力学分析及稳定性控制提供了一种新思路,对现实生产具有重要指导意义。