反向凝固法凝固层厚度的变化规律研究

讨论了反向凝固钢带凝固层厚度的变化规律，分析了一些因素对凝固厚度的影响，结果表明，母带厚度，钢液过热度及浸入时间对凝固层厚度均有不同影响。     

结晶器内凝固壳厚度的数值计算

本文根据结晶器内方坯凝固传热的理论，结合实际情况下不同的初始条件和边界条件，运用有限差分方法计算了结晶器内凝固壳的厚度，并编制了一套计算凝固壳厚度的计算机程序。     

板坯连铸结晶器中三维凝固壳厚度分布的数值模拟及实验验证

建立了连铸结晶器中三维凝固壳厚度分布的计算模型和计算方法，提出了非耦合计算时流动计算域与凝固传热计算域的衔接问题，以及铸坯表面换热系数确定的方法。针对２５０ｍｍ×１３００ｍｍ板坯连铸实际工况，用所建立的模型放处理方法数值模拟了其结晶器中的三维温度场和三维凝固壳厚度分布。同时用实测的凝固壳厚度分布数据验证了本计算听模型、边界条件和计算方法。本采用的方法可满足工程精度、并较简便实用。     

反向凝固08Al／15F复合钢带凝固传热过程的有限元分析

采用大型有限元分析软件ANSYS，对08Al／15F复合钢带的反向凝固传热过程进行了有限元分析。数值计算的复合层厚度随时间的变化与实际的实验测量值基本一致。计算域内温度分布和变化规律显示，在浸渍过程的初始阶段与母带表面接触的复层钢液温度急剧下降至固相线以下，发生液固相变，在界面处形成固一固接触。此外，数值分析还揭示了‘∩’形的复合层厚度一浸渍时间曲线上出现较长“平台”的实质。     

珠钢CSP薄板坯凝固层厚度研究

结合珠钢生产实际情况，采用射钉法来测定二冷区不同位置的凝固坯壳厚度，试验结果表明，4．8m／min拉速下铸坯液芯长度为4820mm，4．5m／min拉速下铸坯液芯为4490mm，两种拉速下连铸坯坯壳厚度的实际测量结果与凝固传热模型计算结果一致。整个凝固过程坯壳厚度生长符合平方根定律。     

小方坯连铸机结晶器的研究

本文建立了铸坯凝固传热数学模型，模拟计算了铸坯温度场、坯壳厚度、热流场、坯壳热收缩应力场、坯壳与铜壁间气隙厚度；计算出的坯壳厚度与实测的坯壳厚度基本吻合，计算结果可为连铸机生产和连铸机设计提供参考。     

济钢板坯铸机凝固壳厚度计算模型的探讨

在射钉试验和生产实践数据的基础上,通过对凝固平方根定律进行演变计算,运用函数回归和函数归一化处理,建立起了板坯铸机二冷区凝固壳厚度快速计算模型。经实践验证,该快速计算模型计算的结果准确可靠。     

射钉法在铸坯凝固终点预报模型中的应用

为了精确掌握连铸机的综合冷却特性,验证铸机模型计算的准确性,进而为优化二次冷却制度提供依据,采用射钉法分别对新钢3号特厚板连铸机中碳钢和高碳钢进行了射钉试验,测量出典型工况条件下矫直区前后位置处铸坯凝固坯壳厚度,并以测得的凝壳厚度为边界模拟预报出凝固终点的位置。从模型计算预报的结果来看,中碳钢在典型工况条件下凝固终点的位置距离弯月面的距离为33.7m,而高碳钢在典型工况条件下凝固终点的位置距离弯月面的距离为27.6m。射钉试验与凝固模拟相结合预报的凝固末端为末端大压下位置设定提供了理论依据。     

结晶器钢液凝固现象的研究

本文研究了连铸机在正常工作状态下,钢水含碳量、拉坯速度、结晶器冷却水流速等因素对铸坯凝固的影响,并对凝固壳厚度进行了实测,掌握了厚度计算值与实测值的偏差规律,为制订连铸工艺提供了依据。     

粉末注射成形充模过程凝固层形成规律研究

根据连续性、动量和能量守恒方程,以及固／液界面上能量平衡原理,建立了考虑凝固层后的一维流动模型,计算了模腔内壁上喂料凝固层厚度与工艺参数的关系,研究结果表明：模具入口附近凝固层厚度开始急剧增加,然后增加速率逐渐减缓;适当提高模具温度,可以减少凝固层厚度,有利于充模过程。     

压力AGC正反馈特性分析

通过理论分析,证明在常用压力AGC系统中,如果轧机刚度计算值比实际值小到一定程度则会产生正反馈,并且只要计算值和实际值存在偏差,则实际厚差不能被完全消除;而且在一些条件下,负反馈的厚度控制过程会因辊缝调节方向错误而造成实际厚度的正反馈现象.找出了产生正反馈的区域.     

热轧带钢层流冷却温度控制模型的应用分析

 工业大学金属材料与加工重点实验室, 安徽 马鞍山 243002) 摘要：在带钢热轧后的冷却过程中，热轧带钢卷取温度的数学模型是至关重要的。介绍了某热轧带钢厂的卷取温度控制数学模型，针对传统的热轧带钢层流冷却卷曲温度控制中数学模型的固有缺陷，分别采用了差分方程和有限元数值模拟的方法，建立带钢厚度方向上的温度场。对测得的数据进行了分析，结果表明：在考虑带钢与介质的热交换的同时再考虑带钢内部的热传导大大提高模型的预报精度，为定量地描述计算值与实测值之间的偏差提供了依据。     

基于弹跳方程的GM-AGC的局限性

通过理论分析,证明在基于弹跳方程的GM-AGC系统中,如果轧机刚度计算值和实际刚度存在偏差,则实际厚差不仅不能被完全消除,而且在某些条件下,看似负反馈的厚度控制过程甚至会因辊缝调节方向错误而造成实际厚度的正反馈现象,从而导致基于弹跳方程的GM-AGC控制效果的恶化。     

热轧带钢局部硬度对冷轧带钢板形的影响

考虑轧件材质横向差异对冷轧带钢板形的影响,采用末架轧机出口带材横向厚度分布和板形作为验证模型精度的指标,定量研究了热轧来料局部硬度对冷轧带钢板厚和前张应力分布的影响程度及规律,通过与现场实测数据的对比,证明该模型提高了轧后板形的计算精度。研究结果显示,局部硬度对冷轧带材的张应力分布影响显著,附加张应力与硬度峰高度成正比,给出了冷连轧过程中轧后带材附加厚度和附加张应力与热轧来料局部硬度的关系。     

钢带喂入比对铸坯组织的影响

通过试验设计,研究了不同钢带喂入比对铸坯组织的影响。结果表明:钢带在恒温钢液中的熔化过程分为两个阶段,开始时钢带残余厚度随喂入时间的增加而快速增加,最多增加100%;钢带厚度达到最大值后开始缓慢减小,直到钢带在钢液中全部熔化,此时钢带残余厚度变为零。钢带喂入比影响铸坯等轴晶率和等轴晶晶粒大小,钢带喂入比从0增加到3%,铸坯等轴晶率从49.3%增加到75.3%,提高52.7%,平均等轴晶晶粒尺寸减小55.4%。过大的喂入比导致铸坯芯部疏松,合适的钢带喂入比为1%。     

A Physical Based Method to Predict Spread and Shape during Flat Rolling for Real‐Time Application

A physical based method is developed that gives real‐time solutions for the transverse variations, across the strip width, for the strip stresses and strains during rolling. From this the strip spread and downstream shape defect are predicted for a given variation in the thickness reduction across the width. The method implicitly couples the downstream residual stresses of the strip under tension, due to non‐uniform strip elongations or shape, to the stress field within the roll gap. The case of a parabolic variation in thickness reduction across the strip width is investigated with the sensitivity of shape defect with the non‐uniform reduction predicted, for various strip thicknesses and widths. These results are shown to be consistent with previously published experimental results. The model is therefore useful in predicting the limits of thickness profile change during rolling before shape defects are formed. Furthermore, being an analytical method the prediction of spread and shape defects can be made in real‐time with a minimum of computational cost. The spread model is then coupled to a roll stack deflection model so that the non‐uniform thickness reduction is also calculated for a set of rolling conditions. The full model solution is calculated within several seconds on a PC, making it possible for real‐time application.     

拉伸弯曲矫直过程中带钢对弯曲辊包角的理论计算

在带钢的拉伸弯曲矫直变形过程中,包角的精确计算对拉伸矫直机延伸率的精确控制至关重要.在不考虑带钢抗弯力矩的影响时,带钢在各个辊上的理论包角比较容易计算,研究了对称模型包角、非对称模型包角、带钢厚度对包角的影响.在确定的设备和带钢厚度时,带钢对弯曲辊的包角取决于其压下量.     

Stress–Strain State of Coiled Steel

In a new mathematical model of the stress–strain state of steel strip in the course of cooling, the nonplanarity, surface roughness, and transverse thickness variation (convexity of the cross section) are taken into account. The stress–strain state of a coil of thin steel sheet has a significant influence on factors such as the temperature distribution in the coil; the scale formation on cooling in the course of hot rolling; the adhesion of adjacent turns in the annealing of cold-rolled strip; and the shape of the coil itself. The mathematical model is based on representation of the coil as individual nested hollow cylinders of finite length. The cylinders are divided into sections over the width. The sum of solutions of the Lame equation for individual sections is shown to converge to the solution for the cylinder as a whole. The model permits calculation of the coil’s stress–strain state, taking account of gap formation between adjacent turns as a result of the transverse variation in strip thickness. The modeling results show how the radial and tangential stress formed in strip winding is distributed within the coil. The model permits calculation of the stress–strain state of the coil in the winding of even strip; in the winding of convex even strip with no tension; in the loose winding of convex even strip with tension less than that in tight winding; in tight winding of even convex strip with the correct tension; and in the winding of convex uneven strip without tension. The decrease in distance between contacting rough surfaces is calculated on the basis of a probabilistic approach. An algorithm is presented for calculation of the coil’s stress–strain state. The result obtained for the stress distribution in the coil is typical for the winding of steel strip. The model is verified for the winding of hot-rolled strip, in terms of the size of the region with tight contact of adjacent turns. The tightness of contact is assessed on the basis of the temper color on the edges of the hot-rolled strip. The discrepancy between the calculated and measured size of the region with tight contact is 3%.     

CVC热连轧精轧机组板形计算软件的开发

针对ＣＶＣ热连轧精轧机组板形计算问题,采用影响函数开发了计算热连轧机轧后板断面厚度分布软件。根据ＣＶＣ轧辊辊形的特点,采用实际轧辊凸度分布模,并利用轧机的反对称性质,计算轧垂直中心线一侧的板断面厚度分布、轧制力分布、辊间压力分布等,提高了板形计算和辊间压力计算的精度,模拟计算结果与现场数据相符。     

Three-layer copper-iron-copper strips of metal powder

Summary The experimental study of the effect of the dimensions of the feed mechanism and the properties of powder upon the relative thickness of copper and iron layers in pore-free strip was carried out. An equation is suggested for the calculation of the relative thickness of copper layers in pore-free strips prior to rolling; this equation takes into account the setting of the feed apparatus and the properties (volume weight) of powders. The calculated data is in good agreement with experimental results. The agreement of the three-layer metal-powder strip with the standard specifications is not worse than that of the strip made of laminated ingots.