Comparison of lubricants in cold thin-sheet rolling

The formation of a lubricant boundary layer at the metallic surface of the strip and rollers in rolling mills is theoretically described. Methods of heterogeneous friction are classified, and the effectiveness of lubricants is compared in the cold rolling of steel strip, in laboratory conditions.     

Investigation into tribology of cold strip rolling

The key factors which determine the friction as well as the surface quality of the rolled strip are the amount of oil which is entrapped in the roll bite and the roughness of strip and roll. In the present paper, the influence of the hydrodynamic and the roughness effect on the entrained film thickness and on the friction conditions in the roll gap have been examined theoretically and experimentally. For the experimental validation of the theoretical findings, rolling tests with thin aluminium sheets are carried out. The main parameters for the hydrodynamic effect, l.e, the rolling speed, base viscosity and yield stress, and the ones for the surface effect, l.e, the surface roughness and its orientation, have been systematically varied throughout the experiments.     

带钢冷轧润滑形膜的特征

提出了一种建立于流体动力学及塑性变形原理基础上的带钢冷轧润滑模型,可用于预测分析轧制变表区内油膜厚度,前滑、轧制压力及摩擦力分布等。该模型首先求解入口速度,然后得到油膜厚度,另外,本作还进行了高运动粘度矿物油带钢轧制、实测了不同压下率下变形区入口处油膜厚度,结果表明：实测值与计算机值吻合很好。该模型为进一步研究带钢冷轧及其润滑过程、优化生产工艺提供了依据。     

Effect of Thermomechanical Processing on Microstructure,Texture Evolution,and Mechanical Properties of Al-Mg-Si-Cu Alloys with Different Zn Contents

The effect of thermomechanical processing on microstructure, texture evolution, and mechanical properties of Al-Mg-Si-Cu alloys with different Zn contents was studied by mechanical properties, microstructure, and texture characterization in the present study. The results show that thermomechanical processing has a significant influence on the evolution of microstructure and texture and on the final mechanical properties, independently of Zn contents. Compared with the T4P-treated (first preaged at 353 K (80 °C) for 12 hours and then naturally aged for 14 days) sheets with high final cold rolling reduction, the T4P-treated sheets with low final cold rolling reduction possess almost identical strength and elongation and higher average r values. Compared with the intermediate annealed sheets with high final cold rolling reduction, the intermediate annealed sheets with low final cold rolling reduction contain a higher number of particles with a smaller size. After solution treatment, in contrast to the sheets with high final cold rolling reduction, the sheets with low final cold rolling reduction possess finer grain structure and tend to form a weaker recrystallization texture. The recrystallization texture may be affected by particle distribution, grain size, and final cold rolling texture. Finally, the visco-plastic self-consistent (VPSC) model was used to predict r values.

     

Theory research on use efficiency of emulsion in cold rolling

Lubrication in cold rolling process is used not only to control friction,but also to control surface quality and thermal chamber.Successful cold rolling of strip at high speeds requires an optimum presence of lubricant film thickness at the contact.In order to have a better control on rolling process the awareness for the prediction and maintenance of desired minimum film thickness.On the basis of learning and summarizing the theories early founded by experts around the world,this paper constructed the m...     

Experimental Analysis on the Frictional Behaviour of Drawbeads in Sheet Metal Forming

In sheet metal forming, drawbeads are commonly used to control uneven material flow, which may cause defects such as wrinkles, fractures, surface distortion and springback. Although friction may not directly change the limiting strain of steel sheets, the tribological conditions in the contact zone between the sheet surface and the tool surface play an important role in determining the limits of the forming process. Friction in the drawbead contact zones affects the flow of the material in the tool and is used deliberately to control the stamping process. Therefore in this study, the frictional behaviour of drawbeads is experimentally investigated by the drawbead friction test. To characterize the effect of processing variables on the friction coefficients, tests are performed for various sheets, lubricants and bead materials suffering different surface treatments. The results obtained from the drawbead friction test show that the friction and drawing characteristics of deforming sheets were strongly influenced by the strength of sheet, viscosity of lubricant and hardness of bead surface.     

Experimental and Numerical Study on Determination of Forces During Cold Rolling of Shafts

The influence of stress and friction conditions on material flow during longitudinal cold rolling of a shaft was investigated. The longitudinal cold rolling method makes it possible to form and finish-up machine parts in the rolling process, which is associated with strengthening of the material due to cold work. The experiments were carried out in order to determine the pressure force at the stage of squeezing on shafts formed by longitudinal cold rolling and made of constructional unalloyed steels S235JR and C45. The experimental results were compared with numerical simulation results obtained by using the MSC. Marc 2010 based on finite element method (FEM). The influence of deformation degree on structural changes and the increase of material strength are shown.     

冷连轧高速轧制过程中摩擦因数机理模型的研究

在现场试验与理论分析的基础上,针对现有摩擦模型对冷连轧高速轧制过程中摩擦因数的预报精度不高、通用性不强等问题,首先对润滑油膜厚度计算模型与摩擦因数返算方法进行了推导,然后定量研究了辊缝中润滑油膜厚度与摩擦因数之间的关系,最终建立起一套适合冷连轧高速轧制的摩擦因数机理模型,并将其应用于宝钢冷轧薄板厂1220五机架冷连轧机与宝钢冷轧厂2030五机架冷连轧机的生产实践.应用结果表明:提高了轧制的稳定性与带材的控制精度,减小了相关模型的自学习与自适应系数波动,取得了良好的使用效果.     

纳米TiO2轧制液对硅钢冷轧性能的影响

分别采用传统冷轧轧制液和纳米TiO₂的冷轧轧制液,对无取向硅钢板进行了四辊冷轧实验.重点研究两种冷轧轧制液的轧制润滑性能和对轧后硅钢薄带表面质量和耐蚀性能的影响.通过场发射电子显微镜和能谱仪对使用两种轧制液轧后得到的硅钢薄带表面形貌和成分进行了分析.给出了轧制液中TiO₂纳米粒子在轧制过程中的抗磨减摩机理.在轧制载荷较高时,纳米TiO₂轧制液具有优良的轧制润滑性能并能显著改善轧后硅钢薄带的表面质量.同时在高载荷作用下,TiO₂纳米粒子被压入硅钢薄带基体,形成一个滑动系来支撑载荷,从而使润滑膜的耐磨性提高.      

冷轧变形量对304不锈钢力学性能的影响

 研究304奥氏体不锈钢薄板的硬度随冷轧变形量的变化规律,为奥氏体不锈钢薄板工业生产提供指导。同时,采用金相显微镜、维氏硬度测量、X-射线衍射仪和透射电镜研究了不同变形量冷轧对304不锈钢显微组织和机械性能的影响。在室温对0.5mm厚退火板材进行冷轧,使冷轧变形量从10%增加到52%。结果表明,形变诱发马氏体相变是导致304不锈钢冷轧时产生加工硬化的主要原因,冷轧可以显著提高钢的强度和硬度。当冷轧变形至40%时,304不锈钢的维氏硬度是未变形时的2.2倍,屈服强度、抗拉强度分别增大到未变形时的4.2倍（880MPa）和1.8倍（1312MPa）。     

Influence of the Cold Rolling and Annealing Sequence on the Ridging Behaviour of Ti‐Stabilized 18% Cr Ferritic Stainless Steel

The influence of the cold rolling and annealing sequence on the ridging resistance and the crystallographic texture distribution of AISI 439 type ferritic stainless steel was studied in order to determine optimal processing conditions for surface quality improvement. In the present study, the effect of two sequences of cold rolling and annealing were analysed: a single cold rolling and annealing, and an interrupted cold rolling with an intermediate and a final anneal. In the conventional single step cold rolling, the ridging resistance was found to deteriorate with increasing cold reduction ratio. For a fixed total cold reduction ratio in the two stage cold rolling, ridging was less pronounced when a higher reduction was applied in the second step. Band‐like clusters of grains with similar crystallographic orientations were observed in the mid‐thickness of sheets with severe ridging. The results show that severe ridging is related to the presence of band‐like clusters of 〈111〉//ND oriented grains. The two stage cold rolling was found to result in less band‐like clusters and an improved surface quality.     

多参数耦合下冷轧铝带工作辊分段冷却调节特性

为得到多参数耦合下冷轧铝带工作辊分段冷却调节特性,建立了工作辊和轧件的一体化耦合传热模型.耦合传热建模过程包含工作辊和轧件导热微分方程的建立、轧件变形热和摩擦热的求解、换热边界条件的确立、工作辊热辊形的计算及采用二维交替差分对微分方程进行求解.仿真结果表明,同一轧制参数下工作辊分段冷却正负方向调节能力近似相等,但单向调节幅度受轧制参数影响较大,轧制长度、喷射梁工作压力和摩擦系数的增加对分段冷却调控能力具有促进作用,轧制速度的作用则相反.      

New Technology for Producing Molybdenum Wire Billets

On the basis of systematic studies of intense methods for metal forming, a production scheme has been developed, substantiated by experiment and realized for manufacturing molybdenum wire. The main stages are helical rolling of small rounded bars, vibratory drawing with induction heating of wire billets, and cold wire drawing with hydrodynamic introduction of lubricant and application to the tool of vibration in the transitional stages of the process (start-up, speed-up, slow-down, and stopping the pulling tool drive).     

TC16钛合金板材冷轧工艺及组织性能研究

进行了TC16钛合金板材多道次冷轧试制,利用光学显微镜、扫描电镜和X射线衍射等手段研究了变形量对冷轧板材微观组织与力学性能的影响。结果表明:α+β两相TC16钛合金板材冷轧加工是可行的,其极限冷变形量达到79%,冷轧板材表面无裂纹。大幅度冷轧变形后,TC16钛合金组织为分布均匀的纤维状结构,且存在极少量未充分变形的α晶粒,并伴有应变诱导的α″马氏体相产生;抗拉强度和显微硬度均得到较大程度的提高,发生明显的冷形变强化。     

基于辊缝动态摩擦方程的铝板冷轧机垂振机理分析

针对高速铝板轧制过程中频繁出现的冷轧机垂直振动现象,结合轧制工艺润滑原理和机械振动理论,建立基于辊缝动态摩擦方程的轧机垂直振动模型.该模型由辊缝几何形状模型,轧辊-轧件工作界面的动态摩擦模型,变形区内的正向轧制应力、摩擦应力分布模型,以及单机架铝板冷轧机二自由度垂向系统结构模型组成.同时,为研究轧辊-轧件工作界面动态摩擦机制影响下的冷轧机垂振机理及系统稳定性,采用某厂单机架铝轧机设备及工艺参数,搭建Matlab/Simulink平台,分别模拟仿真轧制压力和正向轧制应力曲线,验证该模型的有效性;并讨论分析了变形区混合摩擦状态,轧辊-轧件表面粗糙度、轧件入口厚度与系统稳定性的关系.      

冷轧薄板再结晶温度研究

冷轧薄板的生产过程中,金属晶粒经过冷变形,晶粒将随着变形方向拉长。这种变化将导致力学性能等的变化。再结晶退火是冷轧薄板生产过程中的一个重要过程。因此,研究冷轧薄板再结晶温度以及压下率对再结晶温度的影响,对冷轧薄板生产具有重要的实际意义,能够为冷轧薄板生产时退火工艺制度的制定提供理论依据。     

冷轧板常见表面缺陷特征及成因分析

通过生产实践和检验,分析认为冷轧板常见表面缺陷包括原料缺陷和冷轧缺陷两大类,原料缺陷源于炼钢和热轧。原料缺陷如果控制不当,会遗传到冷轧成品板上,冷轧缺陷宏观易于辨识。提高冷轧板表面质量需要冶炼、连铸、热轧、冷轧各工序协调配合。     

铝铸轧带坯生产花纹板质量缺陷的成因探析

针对铝铸轧带坯生产的花纹板，花纹高度不够、筋条不饱满、花纹偏移等质量问题；结合轧制试验结果，对可能影响压花质量的铸轧坯质量、中间退火制度、冷轧轧制参数、乳液润滑剂等方面进行了分析；通过调整工艺参数和改变生产条件问题得以解决。     

冷轧控制模型中摩擦因数模型的开发与应用

摩擦因数模型是冷轧的核心工艺模型之一,目前对其进行的大量研究多是在试验环境下进行的。基于经典摩擦因数模型的工艺原理,综合考虑了轧辊粗糙度、轧制速度等关键因素的影响,结合生产控制的实际情况及控制模型的整体设计,提出了适用的摩擦因数计算模型,进而简要介绍了摩擦因数模型关键参数的调试方式,并提出了一套间接评价模型精度的方法。通过现场测试和长期实际应用证明了模型的控制效果优异。     

Influence of a solution treatment on the evolution of through‐thickness texture gradients in dry cold rolled and recrystallized low carbon steel

The influence of a solution treatment on the evolution of through‐thickness texture gradients in a low carbon steel was studied. In order to intensify through‐thickness variations of the strain state, the samples were cold rolled dry, i.e. without lubrication. The evolution of the texture and the microstructure during rolling and recrystallization was tracked by X‐ray texture analysis and TEM microstructure investigations. The strain distribution during rolling was simulated for several layers of the rolled sheets by the finite element method. After the rolling deformation, a specimen taken directly from the hot band showed pronounced through‐thickness texture gradients, whereas the solution treated specimen showed a rather uniform rolling texture in all layers analyzed. Analysis of the friction behaviour between the different specimens and the roll material points to a much higher friction between the softer hot band and the rolls. This leads to stronger through‐thickness variations in the strain state and, thus, to the pronounced texture gradients observed. The texture gradients in the recrystallized samples reflected those of the as‐rolled sheets. In the center layer of the hot band specimen and in all layers of the solution treated specimen characteristic though notably weakened typical plane strain recrystallization textures formed; the textures in outer layers of the hot band sample were even almost random. These weak recrystallization textures could be attributed to the highly inhomogeneous as‐deformed microstructure.