Analysis of guide modes in vertical hot ring rolling and their effects on the ring’s dimensional precision using FE method

In the vertical hot ring rolling (VHRR) process, roundness, outer radius, and width spread are three important indexes to the formed ring’s dimensional precision. In this paper, features of the guide modes of the VHRR process, such as single fixed guide mode (SFGM) and single follow-up guide mode (SFUGM), are analyzed to investigate their effects on the ring’s dimensional precision. The geometrical models of all the guide modes are then established and reliable three-dimensional coupled thermal-mechanical elastic-plastic FE models of the VHRR process are developed in ABAQUS/Explicit. Some key technologies, such as the guide roller’s motion control, are reasonably dealt with. The research results show that: (1) The roundness of the rings rolled by SFUGM is obviously superior to that of the ring rolled by SFGM. (2) With the same feed amount, the outer radius of the ring rolled by SFGM is always larger than that of the rings rolled by SFUGM. (3) During the rolling process of the ring rolled by SFGM, severe eccentricity will exist at the ring’s center, which is not obvious in the rolling process of the ring rolled by SFUGM. (4) The average value of width spread of the ring rolled by SFGM is slightly larger than that of the rings rolled by SFUGM. The research results can yield an understanding of some phenomena in the VHRR process. The modeling methods presented in this paper have general significance in the study of the VHRR process of the ring with complex profile.     

Mathematic modeling and FE simulation of radial-axial ring rolling large L-section ring by shape axial roll

An accurate prediction of the ring diameter growth rate of a large L-section ring during radial-axial ring rolling (RARR) by a shape axial roll is quite essential because it determines the stability of the process and thus influences the quality of the rolled ring. In this paper, a mathematic model predicting the ring diameter of the large L-section ring during the new RARR process is first established. Then, 3D thermo-mechanical coupled rigid-plastic finite element (FE) models of the new RARR process are developed based on the implicit code DEFORM-3D to verify the mathematic model. By setting and adjusting the movements of the work rolls, large L-section rings are rolled. The effective strain distribution of the rolled ring is analyzed. Comparisons between the FE simulated and the mathematic predicted parameters including external diameter, growth rate of external diameter, and rotational speed of the rolling ring are made. The simulated and the predicted parameters are in good agreement, indicating that the mathematic model accurately predicted the size of the rolling ring and thus can be used to provide a guideline in real manufacturing of large L-section rings.     

大变形量下高碳钢环件冷轧变形过程模拟与试验研究

研究了大变形量下高碳钢环件冷轧变形行为,利用有限元模拟方法分析了环件冷轧过程中的形变规律,采用光学显微镜、SEM等材料表征手段研究了大变形量下环件冷轧过程中的组织演化特点。结果表明：在较小的变形量下,环件内外侧应变较中间应变大,且变形首先发生在环件外侧;整个环件变形过程中,环件中间层的晶粒变形程度最小,外层次之,内层的变形最为剧烈;铁素体基体沿轧制方向呈现明显的方向性,碳化物颗粒分布更为均匀,且数量变少;随着变形量的增大,环件内层的应变明显大于外层的应变,且最小应变的位置偏移至靠外层比较近的区域,其组织中碳化物颗粒脱落加重;当变形量达到625%时,环件达到塑性极限,在内侧表面产生裂纹发生破坏。     

Cavity formation in rolling profiled rings

When rolling profiled (T-shaped) rings at large reductions of ring wall thickness, it is found that for certain values of feed-rate, groove and shape factor, a specific form of cavity formation arises which is similar to the onset of piping as known in extrusion.     

超大型环件径轴向轧制过程偏移机理及自适应模糊控制方法研究

超大型环件径轴向轧制过程容易产生偏移,影响环件轧制稳定性和成形质量。为研究环件偏移机理及其控制方法,分析了轴向孔型滑移区中前滑区和后滑区的分布变化规律,建立了理想情况下不产生环件偏移时锥辊旋转运动学条件,获得了滑移区的最优速度匹配系数。此外,从历史轧制数据中归纳人工控制经验后提出了基于锥辊转速自适应模糊调节的环心偏移量控制方法,基于ABAQUS软件和VUAMP子程序开发,建立了集成有环心偏移量模糊控制算法的?10 m超大型环件径轴向轧制有限元模型,研究了采用最优速度匹配系数的常规控制和自适应模糊控制下的环心偏移量变化规律。结果表明,自适应模糊控制下的平均环心偏移量相比于常规控制降低了72.4%,仿真结果和试验数据均验证了所提超大型环件轧制过程偏移自适应模糊控制方法的有效性。     

内台阶锥形环件轧制三维有限元模拟和工艺优化设计

以Abaqus三维有限元模拟软件为平台，对内台阶锥形环件的轧制过程进行了数值模拟，通过模拟计算揭示了内台阶锥形环件轧制缺陷的形成机理。根据轧制难度分析和有限元模拟结果，对轧制毛坯尺寸和轧制孔型进行了优化。采用铅环件试样在D51—160轧环机上进行了内台阶锥形环件的轧制试验，轧制了合格的内台阶锥形环件。模拟和试验结果表明，轧制毛坯尺寸和轧制孔型优化方案是合理的，基于变形模拟的轧环工艺优化方法是有效的。     

Grain refinement-plastic deformation-texture of bearing ring blank in cold ring rolling

The cold ring rolling of GCr15 steel was carried out for achieving the grain refinement and texture of bearing ring blanks while causing plastic deformation within the matrix. The degree of grain refinement was significantly increased by enlarging the rolled deformation. The plastic damage of bearing ring blanks was correlated with the degree of grain refinement. The rolled plastic deformation was an influential factor with crucial effects on the texture evolution. These results obtained provide valuable guidance for revealing the relationship of the microstructure of bearing ring blanks with the process of cold ring rolling.

     

基于空间啮合理论的环件轧制孔型设计

分析了环件轧制变形的啮合运动性质,基于空间啮合理论建立了环件轧制孔型的一般设计方法,并进行了实例设计计算。本文解决了复杂形状环件轧制孔型设计理论问题,对于环件轧制技术的应用和发展具有实际意义。     

环件冷辗扩中单辊随动导向运动规律研究

根据立式单导向辊随动导向冷辗环机的实际工况，建立了矩形截面环件和深沟球截面环件冷辗扩的运动学模型，分析两种环件的直径变化规律，研究了一定辗扩工艺条件下导向辊的运动规律。建立根据冷辗扩工艺来确定导向辊运动的一整套设计方法，并用MATLAB编写求解程序以求解所有的设计参数。精确地控制导向辊的运动规律有利于提高环件冷辗扩的精度。研究结果为冷辗环机的设计制造提供了依据。     

沟球断面环件冷辗扩三维有限元模拟与工艺设计

沟球断面环件冷辗扩是滚珠轴承套圈制造新工艺。以有限元软件Abaqus为平台,根据冷辗环机实际工作条件,建立从矩形断面毛坯冷辗扩成形沟球断面环件的三维弹塑性动力显式有限元模型。通过动力显式有限元数值模拟,研究沟球断面环件冷辗扩变形过程,揭示出该环件冷辗扩中直径增长和圆度变化规律。基于数值模拟结果,优化设计矩形断面环件毛坯尺寸和冷辗扩工艺参数。在D56G90冷辗环机上进行沟球断面环件冷辗扩试验,验证了数值模拟结果,并采用矩形断面环件毛坯成功冷辗扩出了沟球断面轴承套圈。     

Modeling and simulation of cold rolling process for double groove ball-section ring

Double groove ball-section ring (DGBR) is an important part of bearing rings. Cold DGBR rolling is an advanced continuous and local plastic forming technique by reducing cross section and increasing the diameter of ring blanks between rotating roll, and can directly obtain the DGBR with good mechanical properties. In this paper, the cold DGBR rolling processes from some initially rectangular blanks are investigated by using 3D-FE numerical simulation to reveal its deforming rules. Firstly, by analyzing the dimension relationship between rectangular blank and deformed ring, a new blank size design method is proposed based on rolling ratio and the volume conservation law, and thus a series of different original blanks can be precisely designed under different rolling ratios for a same final required DBGR. Secondly, under the ABAQUS/Explicit software environment, a reliable guide roll adaptive control-based 3D-FE model for cold DGBR rolling process is built via elastic–plastic dynamic explicit finite element method. Finally, several rectangular blanks are designed under different roll ratios and the deforming behaviors of cold DGBR rolling process are investigated with thorough numerical simulation. The results show that: (1) the maximum radial thickness of ring H reduces firstly slowly and then rapidly after the ball groove achieves its final shape; (2) the diameters of the ring expand gradually during the whole process and no sudden change occurs just when the final shape of the ball groove is completely formed; (3) the largest deformation occurs around the ball groove all the time under small rolling ratio; while under large rolling ratio, it occurs first around the ball groove and then gradually transfers to the ring outer surface; and (4) the inhomogeneous deformation degree increases with the progress of the process, and for final parts, it increases slowly first with the increasing of roll ratio and then fast when the roll ratio is greater than a certain value. These results will not only reveal the forming mechanisms of cold DGBR rolling process but also provide a basis to blank optimum design and process adaptive control of the relevant profiled ring rolling processes.     

Thermography in incremental forming processes at elevated temperatures

Temperature measurement is essential for several forming processes at elevated temperatures. It serves to determine and control the workpiece temperature. Thermography as a non-contact-based technology offers the possibility to capture thermograms of complete workpieces without any time-offset. However, the application of thermography requires the knowledge of the fundamentals of radiation thermometry, in particular the emissivity. This paper presents the results of the application of thermography in incremental sheet forming (ISF) with Joule heating and radial–axial ring rolling as a bulk forming process. Using thermography for the determination of the temperature of the forming zone allows for a real-time closed loop control in ISF with Joule heating. Additionally, the results of the temperature measurement of the surface temperature of radial–axial rolled rings are presented, which can be used as a starting point to make a forecast of the rings’ dimensions in cold state.     

基于铸辗复合成形的42CrMo钢环坯铸造工艺与试验研究

针对目前环形零件生产工艺流程长,加热次数多,浪费材料和能源等问题,提出和研究环形零件短流程铸辗复合成形新工艺。该工艺采用铸造环坯直接辗扩成形,具有节能、节材和缩短工艺流程等优点。在这种新工艺中,环坯的铸造质量、组织和力学性能对后续的辗扩工艺和环形零件组织、性能具有重要的影响。以轴承环件常用的42CrMo钢为研究对象,通过理论分析和模拟研究,提出高质量环形铸坯铸造工艺;并进行实际工业试验。通过试验研究和性能测试,表明该铸造工艺生产的环形铸坯具有良好的质量、组织和力学性能,可以为轴承环件铸辗复合成形提供高质量的铸坯。     

超大型环件径轴向轧制过程稳定性与圆度自适应控制方法研究

超大型环件径轴向轧制过程失稳、失圆等异常状态常导致轧环终止和产品质量波动。提出了轧环过程稳定性和圆度自适应控制方法,从历史数据中归纳人工控制经验知识,建立了基于锥辊转速模糊调节的轧制稳定性控制方法,制定了基于导向力反馈的轧制圆度控制策略。运用ABAQUS有限元软件和子程序二次开发,设计了轧环过程稳定性和圆度自适应控制子程序,建立了16 m超大型环件轧制过程控制有限元模型,仿真分析了锥辊转速模糊调节、导向力反馈以及基于限幅滤波的锥辊转速模糊调节+导向力反馈综合控制下的轧环过程偏移量和圆度误差变化规律,结果表明该方法与常规规划控制相比,环件偏移量减小了48.3%,圆度误差减小了61.8%。     

Effect of rolling ratio on groove-section profile ring rolling

Ring rolling is an advanced plastic forming technique which is used to manufacture precise seamless rings. Rolling ratio is regarded as a decisive parameter for the ring rolling process because it decides the blank dimension, reflects the ring deformation degree and influences the forming results. However, its importance for the ring rolling process is always neglected. In this paper, the effect of rolling ratio on the groove-section profile ring rolling is firstly investigated. The relationships between rolling ratio and blank dimension, rolling ratio and ring deformation degree are theoretically studied and a theoretical value range of rolling ratio is proposed. Then, with FE simulation, the influences of rolling ratio on the forming results are revealed. Based on comparison and experimental verification, a reasonable value range of rolling ratio is determined.     

Photoelastic study of the influence of oil film on contact stresses

The paper describes some experiments, the object of which was to determine the stress distribution at a contact surface or below of it. Plastic and glass cylinders were rolled on the inner surface of a hardened steel ring under dry and lubricated conditions. The ring and the cylinder were driven by separate motors to enable rolling and sliding contact.     

Experiments study on the rolling process for heavy disk

Roll forming is a flexible and low-cost technique for manufacturing axisymmetric parts. The disk-rolling process using the revamped radial–axial ring rolling mill has been developed from the radial–axial ring rolling process. This paper introduces the disk-rolling process in detail. Experiments of rolling process for heavy hollow disks were carried out on the revamped Wagner RAW500/400 ring rolling mill. Qualified heavy disks of Q235 steel and 0Cr11Ni2MoVNb steel were successful rolled. The interrelations of billets and disks dimensions were researched on these experiments. It was found that all the qualified disks have a big section spread. Furthermore, the expansion of the inner hole diameter and the outer diameter of the disk during the rolling process were studied. The result indicates that, in order to roll a qualified disk, there must be enough section spread deformation for the billet.     

环件辗扩成形过程微观组织及性能控制研究进展

高性能大型环件精确辗扩控形控性一体化制造是大型运载火箭仓体、风电法兰、核电反应堆及石油化工容器等高端装备向着安全、轻量、高效和长寿命方面发展的迫切需求。综述环件辗扩成形过程微观组织及性能研究现状,分析单、双道次简单热模拟压缩试验和显微组织演变数值模拟技术在环件辗扩过程组织演变研究中的应用,探讨环件组织与性能控制中存在的问题,并指出目前的研究已无法满足上述高性能环件制造要求。提出复杂多道次物理模拟及内变量组织建模用于环件辗扩组织演化分析的必要性,探明环件宏观/微观织构定量表征和晶体塑性有限元法(Crystal plasticity finite element method,CPFEM)揭示组织演变机理的可行性。阐述今后高性能环件辗扩成形组织演变及性能控制的研究方向与重点,未来必须构建辗扩过程环件组织、织构和力学性能之间及其与工艺参数的定量关系。     

基于产品特征的自润滑关节轴承滚压技术研究

通过对轴承滚压安装工艺和质量控制的分析,建立了自润滑关节轴承滚压收口有限元模型,利用ABAQUS分析轴承外圈唇边的形成过程并进行了试验验证,结果表明:当轴承座内孔处厚度比轴承外圈厚度小0.1～0.2 mm,倒角为外圈V形槽深度的0.6～0.7时,轴承滚压收口质量最好.     

大型L形环件径轴向轧制成形仿真分析

环件径轴向轧制工艺是生产大型环锻件的一种先进加工技术,目前关于大型异形环锻件的径轴向轧制成形理论和工艺的研究相对较少,无法为该类型环件实际轧制生产提供指导。因此,本文为主要针对工程机械用大型L环件的稳定轧制问题,采用优化的毛坯设计控制环件精密成形,采用轧辊分级降速控稳定轧制,借助有限元软件ABAQUS进行仿真建模与分析。研究结果对于该类型环件的径轴向轧制工艺设计具有重要意义。