Influence of roll radius on contact condition and material deformation in skin-pass rolling of steel strip

Skin-pass rolling (or temper rolling) is the final forming step in the production of cold rolled steel sheets. Although a large roll radius compared to the contact length is one of the characteristics of skin-pass rolling conditions, numerous studies have been conducted thus far using laboratory mills with small radius rolls. In this paper, the influence of roll radius on the contact condition and material deformation in skin-pass rolling is examined and clarified by numerical analysis by an elastic–plastic FEM analysis as well as experimental rolling tests, which were performed to verify the result of the analysis. Some characteristics of skin-pass rolling related to pressure distribution, contact condition and material deformation are not properly simulated using small radius rolls. Considering characteristic skin-pass rolling conditions, two cases using simplified models, i.e., vertical compression and rolling with a circular, rigid roll, were analyzed.     

箱盖卷耳工艺及模具设计

箱盖边缘卷边类似于普通铰链卷耳,不仅在冲压工艺和模具结构上较为复杂,而且要求模具工作可靠,避免在卷耳过程中出现问题,造成零件报废。文章介绍了汽车工具箱盖成形卷耳工艺及模具设计。     

热轧润滑油中的添加剂及热轧润滑在我国的发展——热轧润滑技术讲座(四)

介绍了热轧润滑油中各种添加剂的成分和功能，以及对其性能的要求，同时分析了热轧润滑在中国的发展前景。     

Influence of radial and axial runouts on surface roughness in face milling with round insert cutting tools

In face milling processes, the surface quality of the machined part depends on many factors, including feed, cutting tool geometry and tool errors. In this work, a numerical model for predicting the surface profile and surface roughness as a function of these factors is presented, incorporating a random values generation algorithm that makes it possible to determine the variation in surface roughness from the values that can be adopted by tool errors. This work is focused on round insert cutting tools and the influence of tool errors such as radial and axial runouts. The results that correspond to a number of teeth equal to 4, insert diameter of 12 mm, depth of cut of 0.5 mm, cutting speed of 120 m/min and feed of 0.4–1.4 mm/rev are analysed. Milling experiments are made to verify the validity of the model and the discrepancies between the experimental and theoretical surface profiles are assumed to be a consequence of different factors such as the variation in undeformed chip thickness along the surface profile.     

热挤压加工中的摩擦与润滑问题初步探讨

讨论了热挤压加工过程中摩擦的特点,热挤压模具失效形式;在此基础上对热挤压模具的润滑方法进行了探讨。     

Predictive modeling of surface roughness and tool wear in hard turning using regression and neural networks

In machining of parts, surface quality is one of the most specified customer requirements. Major indication of surface quality on machined parts is surface roughness. Finish hard turning using Cubic Boron Nitride (CBN) tools allows manufacturers to simplify their processes and still achieve the desired surface roughness. There are various machining parameters have an effect on the surface roughness, but those effects have not been adequately quantified. In order for manufacturers to maximize their gains from utilizing finish hard turning, accurate predictive models for surface roughness and tool wear must be constructed. This paper utilizes neural network modeling to predict surface roughness and tool flank wear over the machining time for variety of cutting conditions in finish hard turning. Regression models are also developed in order to capture process specific parameters. A set of sparse experimental data for finish turning of hardened AISI 52100 steel obtained from literature and the experimental data obtained from performed experiments in finish turning of hardened AISI H-13 steel have been utilized. The data sets from measured surface roughness and tool flank wear were employed to train the neural network models. Trained neural network models were used in predicting surface roughness and tool flank wear for other cutting conditions. A comparison of neural network models with regression models is also carried out. Predictive neural network models are found to be capable of better predictions for surface roughness and tool flank wear within the range that they had been trained.Predictive neural network modeling is also extended to predict tool wear and surface roughness patterns seen in finish hard turning processes. Decrease in the feed rate resulted in better surface roughness but slightly faster tool wear development, and increasing cutting speed resulted in significant increase in tool wear development but resulted in better surface roughness. Increase in the workpiece hardness resulted in better surface roughness but higher tool wear. Overall, CBN inserts with honed edge geometry performed better both in terms of surface roughness and tool wear development.     

镦粗试验中鼓度与摩擦的相关性研究

建立了圆柱体镦粗的刚塑性有限元模型,模拟了高径比为1．5和1．0、当摩擦因子从0.1到1.0之间变化时圆柱体镦粗过程,给出镦粗试验中试件鼓度与接触面上摩擦因子间的定量关系,该关系可用来剔除流动应力试验中的摩擦和测量接触面上的摩擦因子。     

Industrial experiments and findings on temper rolling chatter

Based on a series of tests, the chatter of temper rolling has been studied. It is shown that the temper rolling chatter is self-excited vibration and its cause is the rolling interface where partial fluid lubrication and viscous-slip co-exist.     

热轧润滑方法和润滑油的发展：热轧润滑技术讲座（三）

介绍了热轧润滑的供油方法,热轧对润滑油性能的要求,以及润滑油成分和主要物理性能。     

Material adhesion and stresses on friction stir welding tool pins

During friction stir welding, polygonal tool pins experience severe stresses and, under certain conditions, loss of functionality due to adhesion of plasticised material on their surfaces. The extent of adhesion is analysed for various pin geometry and welding conditions based on the theory of machining. The effective stresses on the polygonal pins are evaluated following the principles of mechanics. The results show that the polygonal pins with fewer sides can avoid permanent adhesion of plasticised material at higher weld pitch, which is defined as a ratio of welding speed and tool rotational speed. The computed pin geometries for minimum adhesion are compared with the pin profiles recommended by various investigators based on independent experiments. The computed stresses show that pins with larger number of sides will experience lower stresses for any given set of welding variables.     

热轧工艺润滑技术的开发与应用

阐述了热轧工艺润滑的机理及作用,并结合工艺润滑技术在宝钢２０５０ｍｍ热轧厂的开发与应用,探讨了工艺润滑对带钢表面质量及环境的影响．     

热轧润滑机理及其出现和应用的前景—热轧润滑技术讲座（一）

介绍了板带热轧润滑的机理及作用,分析了随着轧辊材质的进步,轧制速度的提高、市场需求的不断增加,热轧润滑技术的出现和应用前景。     

Influence of tool thread on mechanical properties of dissimilar Al alloy friction stir spot welds

Abstract

The influence of threaded and wear simulated (half thread) tools on the mechanical properties of dissimilar Al alloy friction stir spot welds is investigated. With lower tool rotational speed settings, the failure loads of Al 5754/Al 6111 lap joints made using a threaded tool were clearly higher than that of a half thread tool. However, the failure load of the joints made using a half thread tool increased when the tool rotational speed increased, and finally, as the rotational speed was further increased, the failure load became almost the same as the failure load of joints made using a threaded tool. In Al 5052/Al 6061 butt joints made using the threaded and half thread tools, the area of the stir zone on the bonded cross-section corresponded with the actual bonded region on the fracture surface. Therefore, the thread on the rotating pin has limited influence on the mechanical properties of the friction stir spot lap joints.     

An example of selection of the cutting conditions in broaching of heat-resistant alloys based on cutting forces, surface roughness and tool wear

Despite the fact that broaching has been used for long a time as a machining process for manufacturing highly accurate, complex profiles, little work has been published on the selection of cutting conditions to maximise tool life while achieving the required surface quality and level of cutting forces. This is even more important when notorious difficult-to-cut materials, such as Ni and Ti alloys, used in the aero-engine/power generation industry where high geometrical accuracy, along with restricted surface quality are required. The paper describes a multi-step methodology to select the cutting conditions for the broaching of Ni and Ti alloys used in the manufacture of aero-engines and power generators. Based on the application of the Taguchi technique, the cutting conditions (cutting speed, rise per tooth, rake angle, coolant type) were selected in order to obtain fine surface quality along with reasonably low levels of main cutting force (Fz) and perpendicular cutting force (Fy). This was followed by a reduced number of tool life tests which were carried out in order to select the final cutting conditions. Scanning electron microscopy (SEM) and chemical composition analysis on the flank and rake faces of the tools were employed to characterise the worn tools. It was found that when broaching forces, surface roughness and tool life are considered as process output measures, and taking into consideration generic process constraints on process productivity, machine tool stability, and tool stiffness, only a “pseudo-optimal” solution for the cutting conditions could be specified.     

Lubricity of volatile lubricants in sheet metal rolling

A series of experiments is carried out by using a rolling type tribometer to investigate the lubricity of the volatile lubricants at high speed forming. The roll material is the die steel alloy SKD11, and the workpiece material is the mild steel SPCE with a rough surface and the aluminum alloy A3004 with a smooth surface. Experimental results show that the friction coefficient decreases with increasing working velocity for both SPCE and A3004, in any lubricant. With an increase of reduction in thickness, the friction coefficient decreases for SPCE, but increases for A3004. Some volatile lubricants have the same lubricity as the generally used mineral oil with low-viscosity by judging from the value of friction coefficient, the surface appearance of rolled workpiece and the roll surface damage.     

轧制参数对钢球螺旋孔型斜轧工艺的影响

采用螺旋孔型斜轧工艺加工轴承钢球,其模具加工、调试安装复杂且耗时。针对该问题,利用有限元软件Deform,对轴承钢球轧制过程进行了仿真模拟,并采用控制变量法的思想,通过改变单一参数研究了棒料尺寸、轧制温度、轧辊倾斜角度对钢球轧制成形的影响规律,从而为钢球的斜轧工艺设计提供一定的参考。研究结果表明:棒料尺寸对钢球外形影响最大,棒料尺寸不足会造成钢球带有环带沟,棒料尺寸过大会导致钢球表面金属堆积;轧制温度对轧制力影响最大,轧制温度的提高有利于降低轧制力,但会导致钢球表面的脱碳及氧化皮现象严重,因此应尽可能采用较低的轧制温度;当轧辊倾角小于轧辊螺旋升角时,在轧制过程中容易出现钢球无法旋转的情况,因此应尽可能使轧辊倾角与轧辊的螺旋升角保持一致。     

Unsteady lubrication modeling of inlet zone in metal rolling processes

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楔横轧模具数控编程系统的研究

针对楔横轧模具数控加工的复杂性和特殊性,从系统集成角度,研究开发了楔横轧模具数控编程系统。文中详细阐述了楔横轧模具数控加工系统的总体结构以及该系统各主要功能模块的结构、原理及实现机制。     

Statistical analysis of surface roughness and cutting forces using response surface methodology in hard turning of AISI 52100 bearing steel with CBN tool

The present work concerns an experimental study of hard turning with CBN tool of AISI 52100 bearing steel, hardened at 64 HRC. The main objectives are firstly focused on delimiting the hard turning domain and investigating tool wear and forces behaviour evolution versus variations of workpiece hardness and cutting speed. Secondly, the relationship between cutting parameters (cutting speed, feed rate and depth of cut) and machining output variables (surface roughness, cutting forces) through the response surface methodology (RSM) are analysed and modeled. The combined effects of the cutting parameters on machining output variables are investigated while employing the analysis of variance (ANOVA). The quadratic model of RSM associated with response optimization technique and composite desirability was used to find optimum values of machining parameters with respect to objectives (surface roughness and cutting force values). Results show how much surface roughness is mainly influenced by feed rate and cutting speed. Also, it is underlined that the thrust force is the highest of cutting force components, and it is highly sensitive to workpiece hardness, negative rake angle and tool wear evolution. Finally, the depth of cut exhibits maximum influence on cutting forces as compared to the feed rate and cutting speed.