Edge stresses in wide strip hot rolling

In the rolling of wide strip, longitudinal tensile stresses develop along the edges which enhance edge cracking. Theoretical assessment of these stresses and the factors affecting their magnitude and spread are not emphasized in existing solutions, since most of the solutions are based on the assumption of plane strain along the entire width. In the present work a flowline field solution is developed to analyze the flow and stresses in steady state wide strip hot rolling based on the concept of a plane-strain middle zone and two lateral flow edge zones from which edge stresses and edge zones width have been determined. The results obtained show that the maximum value of the longitudinal edge stresses is 1/√3 the flow stress and occurs at the neutral point where the width of edge zone is maximum. The influence of the coefficient of friction at roll-strip interface, roll diameter and thickness reduction ratio on the magnitude and spread of edge stresses is not appreciable.     

Analysis of flow and stresses in a tube stretch-reducing hot rolling schedule

Analytical expressions for the roll-pass geometry, velocity, strain, strain rate and stress components are obtained for steady-state tube stretch-reducing hot rolling. From these expressions the reduction in tube diameter and wall thickness, inter-stand tensions, roll load and rolling torque have been determined in relation to the roll gap opening and the inter-stand velocity increase ratio. The results have shown that increasing the interstand velocity increase ratio will increase the inter-stand tension while the roll load remains almost unchanged. The rolling torque increases with the increase of the back inter-stand velocity increase ratio and decreases with the increase of the ratio at the front. There is a limiting value for the inter-stand velocity increase ratio at which the rolling process will tend to become unstable. The analysis has been validated by comparing the theoretical results with on-line power measurements on an industrial tube stretch-reducing hot rolling mill.     

Effect of roll gap change of oval pass on interfacial slip of workpiece and roll pressure in round-oval-round pass rolling sequence

This paper presents a study of the effect of varying the roll gap of oval pass in round-oval-round pass sequence on the interfacial slip of workpiece, entrance and exit velocities, stresses and roll load that the workpiece experiences during rolling, by applying analytical method, finite element simulation and verification through hot bar rolling tests. The results have shown that the roll gap variation of oval pass affects the interfacial slip of workpiece along the groove contact and the specific roll pressure. The optimum conditions in terms of minimum interfacial slip and minimum specific roll pressure, which might influence the maximum groove life, is obtained when the subsequent round pass is completely filled.     

Experimental study for roll gap adjustment due to roll wear in single-stand rolling and multi-stand rolling test

To investigate a correlation between the amount of wear and roll gap (pass height) adjustment, we performed a single-stand reversible pilot groove rolling test as well as rolling test in an actual rod mill. In case of the pilot rolling test, we designed wear contour (profile) and machined it on the original roll groove (i.e., roll groove with no wear) to make the roll groove worn down. For the actual rod mill test, we developed a measuring device which can detect the actual wear profile. To determine the amount of roll gap adjustment, we propose a model for equivalent roll gap decrement which reduces the increased exit cross sectional area due to wear. We applied the proposed model to multi-stand rolling (roughing train of POSCO No. 2 Rod Mill) as well as single-stand reversible rolling. The wear profile of rolls worn down at each stand in mill yard was measured at different roll tonnage. The pilot hot rolling test shows that variation of exit cross sectional area is almost linearly proportional to roll gap change while the roll gap decreases from reference roll gap (6.5mm) to 3.5mm. In an actual rod mill which has consecutive rolling system, relationship between tonnage (total amount of tons that the produced rod weighs) and roll gap change at a stand is dependent on the rolling type (oval-to-round or round-to-oval) together with the cross sectional shape of incoming workpiece.     

基于塑性流动本构关系的多步反向模拟法

传统板料成形反向模拟法的本构关系是建立在塑性形变理论的基础上,无法考虑变形历史的影响.提出一种新型有效的多步反向模拟法,采用弹塑性材料模型提高计算精度:引入DKT12薄壳单元考虑类似模具圆角处的弯曲一反弯曲效应等应变历史的影响.提出一种基于塑性流动理论的本构方程,可以快速准确地处理弹/塑性变形及加载/卸载状况,提高了应...     

基于LS-DYNA的板料成形数值仿真及其在轴承冲压保持架中的应用

在论述板材冲压数值模拟数学方法的基础上,运用Dynaform模拟仿真分析轧机轴承冲压保持架的弯曲、拉深、整形等冲压工艺过程,并图示给出了板料实际变形过程中发生的如起皱、拉裂、板厚变化等现象,优化了毛坯尺寸、压边力、润滑方案、模具结构等工艺设计,提出了改进模具和工艺参数的措施.     

铸辗成形大口径25Mn钢环件微织构及力学性能

根据铸辗复合成形工艺对大口径25Mn钢环件进行离心铸造和热辗扩工业试验以及对其调质处理,运用金相显微镜、扫描电镜和电子背散射衍射技术分析组织与织构,并采用拉伸与冲击试验等手段检测其力学性能。结果表明,辗扩件外形尺寸精确,组织相对均匀,个别区域伴有不规则晶粒;微观织构组态主要为沿着111//ND取向线分布的黄铜R织构{111}112和取向密度为6.0的高斯织构{110}001,力学性能较好,但塑性稍微偏低;揭示拉伸和冲击断裂机理为解理与韧窝共存形式。调质后回火析出弥散分布的细小碳化物颗粒,晶粒更加细小均匀,大角度晶界所占比例为3/4;揭示织构演化表现为高斯织构沿着?-取向线逐渐向旋转立方织构{110}110聚集转变,塑性性能得到明显提高,呈现典型的韧窝断裂。研究揭示通过离心铸造25Mn钢环坯直接热辗扩成形大口径环件是切实可行的,达到了环件成形/成性的双重目的。     

基于有限元分析及非线性规划的金属成形过程优化设计

综述显式有限元分析和非线性规划算法的理论基础，进而将它们在金属成形分析和设计中的应用加以回顾。     

梅钢新建热轧机组装备特点分析

介绍梅钢新建热轧生产线机组的工艺特点及优化配置情况,对国内热连轧机组装备及工艺提升有一定的借鉴作用。     

推镗滚压工艺中滚柱急剧失效的分析

对液压缸体推镗滚压工艺中出现的滚柱急剧失效现象进行分析,对滚压过程中滚柱的运动轨道和所受载荷情况进行研究,找出滚柱急剧失效的原因,提出解决问题的方法,为液压缸体推镗滚压加工工艺提供了实际经验.     

环件辗扩过程的导向辊控制工艺及设备的研究

导向辊的控制在环件辗扩中有着重要意义.对现有的导向辊控制方式及其存在的问题进行了分析,通过对导向辊运动轨迹的分析,提出了一种新的导向辊控制工艺,并给出了该控制工艺的设备实现方法.最后通过有限元分析软件ABAQUS对具体的环件辗扩实验进行了模拟分析,结果表明,采用该导向辊控制工艺进行环件辗扩可以得到较高质量的环件产品.     

“1+4”铝热连轧轧制力自学习

在铝热连轧精轧生产过程中,轧制力的预报精度直接影响板厚和板凸度控制精度。针对河南某1+4铝热连轧机现场轧制力预报精度较低的问题,根据现场采集的大量轧制数据,建立了轧制力模型自学习算法,并用细菌觅食优化算法对自学习中的增益系数进行了优化,提高了轧制力预报精度。     

割枪在热加工中的高效节能应用

本文介绍了割枪用于热处理及其它热加工领域的高效节能应用方法,只要将欲加热的工件置于防散热的简易保温桶内,割枪的加热效率就可数十倍的提高,从而扩展了割枪在热加工领域的应用范围。     

事故液压剪方案设计及结构要点分析

针对铝板热轧机组中事故液压剪的设计方案进行分析探讨,给出主要设计参数的计算和选取依据,提出同步机构的设计要点。     

实验室薄板坯连铸连轧Fe-3%Si热轧钢板的织构

在实验室条件下采用薄板坯连铸连轧工艺制备了Fe-3%Si热轧钢板,采用EBSD和X射线衍射仪分析了不同热轧总变形量和压下制度下钢板的织构组织,分析了α、ε和γ取向线上织构密度的变化规律。结果表明:热轧总变形量由82.9%增大到97.1%时,A成分钢板表层和心部的组织和织构梯度出现,{001}〈110〉取向加强,并向{110}〈001〉和{112}〈111〉等方向发展;B成分钢板在不同压下制度下的织构分布基本相同,但是B1试样的高斯织构取向密度和体积分数较高,C1热轧压下制度有利于高斯织构组织的形成。     

H68黄铜热轧润滑油的研制及应用

根据亲水亲油平衡（Hydrophile-Lapophile Balance，HLB）理论，通过选择合适的乳化剂、抗磨剂、极压剂、防锈剂等添加剂，研制成适用于硬态黄铜（H68，H70和H72）的热轧乳化液，成功地应用于2Cr13不锈钢焊态热轧辊初轧多种硬态黄铜板材，取代了目前铜加工生产中，对于硬态黄铜普遍使用润滑脂间歇式地润滑热轧辊的工艺。生产结果表明：由于采用直接连续地喷射乳化液到轧辊表面，容易控制板形和板材的尺寸；提高了轧辊的抵抗磨损和防止粘辊的能力，克服了铜带表面的“黑丝”、“发黄”和粗糙化现象，稳定地改善了铜带表面的质量，降低了工人劳动强度，从而极大地提高了生产效率并延长了轧辊的使用寿命。     

国内电工钢的生产现状与发展趋势

综述了国内近几年电工钢的生产状况,介绍了武钢、宝钢、太钢、鞍钢的品种牌号,分析了与日本国的差距,进行了发展预测.     

热轧板卷取电机的自动控制与应用

热车板是以板坯为原料,经加热后由粗轧机组及精轧机组制成带钢,从精轧最后一架轧机出来的热钢带通过层流冷却至设定温度,由卷取机卷成钢带卷。通过论述卷取电机的速度与张力控制原理,结合PLC控制,实现对热轧卷取的高精度控制。     

合金轴承座挤压过程中金属流动规律的研究

采用数值模拟的方法，得出了HAL60—1—1合金止推轴承座挤压成形过程中与凸模顶面接触的金属不产生径向流动。并通过画有网格的铅料进行挤压试验，试验结果验证了此结论，证明凸模顶端的凸起结构没有在接触面上拉出沟槽。最终用HAL60—1—1合金进行试验，加工出了止推轴承座成品。     

金属质个性化手术模板的全数字化快速设计及制造

为满足手术模板对快速成型、精确定位和个性化的要求,基于逆向工程结合正向建模设计和选区激光熔化快速成型技术提出了一种全数字化设计、制造金属质个性化手术模板的方法。分析了手术模板的医学需求,从成型方式以及扫描策略两方面提出缩减成型时间、减轻成型件重量以及减少热变形的方案。分别研究了致密态成型和非致密态成型两种工艺,其中非致密态成型采用高扫描速度实现,成型过程采用邻层互错、正交及分区扫描策略。利用上述方法,成功设计了一套手术模板,并分别利用致密态以及非致密态两种方式对模板成型。结果表明,模板尺寸精度达±0.5 mm;另外,与致密态成型方式相比,非致密态方式的成型时间减少了43.3%,模板重量减轻了18%。该方法成型的手术模板已成功应用于临床。