Towards a steady forming condition for radial-axial ring rolling

Radial-axial ring rolling (RARR) is a typical incremental forming process with high flexibility. It is difficult but essential to establish a successful RARR process and remain its stability by properly designing process variables. This paper is an attempt to develop a steady forming condition under which the RARR process can be established successfully and then proceeds stably with qualified ring rolled parts. For remaining process stability by alleviating dynamic contacts and collisions between the ring and the rolls, constant growth velocity condition (CGVC) of the ring is proposed as a design objective of the process variables. Then a mathematical model of the steady forming condition for RARR is developed based on the CGVC. The model describes both the mathematic correlations and the reasonable ranges of key process variables of RARR, and the application and role of the model are illustrated by a case study in detail. For verifying the steady forming condition for RARR, FE simulations and analyses are carried out through developing reliable 3D-FE models for the entire RARR processes under ABAQUS/Explicit platform. The simulation results show that the designed processes based on the mathematical model of the steady forming condition are successfully operated and have good stability. A value of the growth velocity of the ring, which is close to the median of its reasonable range determined by the steady forming condition, is recommended for the design of the process by taking into account the geometry of the rolled ring, material plastic deformation behavior of the ring and process stability.     

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。     

Ring blank design and its effect on combined radial and axial ring rolling

In conventional ring rolling, it is difficult to achieve a large increase in the ring height. This paper proposes a new combined radial and axial ring rolling process, which can achieve a large increase in both the ring diameter and height. During the proposed process, the geometry of the ring blank is of great importance because it determines the distribution of the radial ring rolling process and the subsequent axial ring rolling process. Therefore, this paper is aimed to reveal the effect of the geometry of the ring blank on the combined radial and axial ring rolling process. Using the finite element (FE) method, the deformation characteristics of the ring are first investigated. Then, the effect of the geometry of the ring blank, axial height H ₀, outer diameter D ₀, and thickness t ₀, on the geometry development and inhomogeneous deformation of the final rolled ring, is revealed. The results of this research provide an important basis for the design and optimization of the ring blank in the new combined radial and axial ring rolling process.     

Numerical simulation and experimental study on geometry variations and process control method of vertical hot ring rolling

The accurate geometry and effective control during the ring rolling process are the prerequisites for the ring products’ precise forming. In this paper, the interaction modes and rules between ring and rolls in vertical hot ring rolling (VHRR) process are analyzed, and the change laws of the ring’s geometry are studied. Based on the ABAQUS/Explicit software and its subroutine VUAMP, the finite element (FE) model of the VHRR process with measurement and control is established. Then, the ring rolling process of a groove-section profile ring is simulated. During the simulation, the ring’s outer diameter, roundness error, and the stability of the rolling process are detected in time, and the close-loop control of feed plan of the drive roll and measuring roll are also employed. The results obtained show the following: (1) Four feed stages are divided by means of a step-down feed movement, that is, bite stage, main rolling stage, precise forming stage, and sizing stage. (2) At bite and main rolling stages of the VHRR process, the ring’s center swings in a spiral line, and the rolling process is unstable, the ring’s roundness becomes worse, while the process is entering the precise forming stage, by means of the guide roll, the rolling process becomes steady and the ring’s roundness tends to be better. (3) The measuring roll contacts with the ring at the main rolling stage, afterwards, it is pushed back at the precise forming stage by ring’s growth. When the measuring roll meets the desired displacement value, a stop feeding command will be fed back, and the ring rolling process enters the sizing stage. At the sizing stage, the ring’s outer diameter still increases a little. (4) A series of VHRR experiments are conducted, and FE results are in good agreement with experimental results. The absolute errors of the ring’s outer diameter and the roundness are within 1 mm. The research results of this paper have practical significance to guide the VHRR production.     

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.     

Spread and flow patterns in ring rolling

Tellurium lead and aluminium alloy rings were rolled on an experimental radial ring rolling mill to reductions as great as 70% to determine the spread when taking into account the various ring rolling factors.Both plain and profiled rings were rolled. In the case of the profile ring rolling, a T-shaped section was formed from an initially rectangular cross-section, the undriven mandrel being grooved and the main roll plain.The mode of deformation for plain and profiled rings was also examined and is reported.     

内外局部约束下内齿圈滚轧成形

提出一种内外局部约束高效滚轧成形内齿圈新工艺,完成相关工艺构架并分析了其成形过程内外滚轧模具及工件的运动特征。搭建了采用2对滚轧模具的内齿圈滚轧试验平台,实现了内齿圈滚轧;建立多对滚轧模具内外局部约束下内齿圈滚轧过程有限元模型,完成了采用2对滚轧模具和3对滚轧模具的内齿圈滚轧过程有限元分析。试验与有限元结果表明,齿形形状完整、轮廓清晰,达到了设计齿高要求,内齿圈滚轧成形工艺可行;和试验获得齿高相比,有限元模型对齿形预测误差小于5%;通过适当的模具和坯料几何参数调整,可控制成形齿高、改善端面成形质量。研究结果对内复杂型面零件的高效省力成形工艺具有理论意义和参考价值。     

Technology and experiments of 42CrMo bearing ring forming based on casting ring blank

Bearing ring is the crucial component of bearing. With regard to such problems as material waste, low efficiency and high energy consumption in current process of producing large bearing ring, a new process named ＂casting-rolling compound forming technology＂ is researched by taking the typical 42CrMo slew bearing as object. Through theoretical analysis, the design criteria of the main casting-rolling forming parameters are put forward at first. Then the constitutive relationship model of as-cast 42CrMo steel and its mathematical model of dynamic recrystallization are obtained according to the results of the hot compression experiment. By a coupled thermal-mechanical finite element model for radial-axial rolling of bearing ring, the fraction of dynamic recrystallization is calculated and recrystallized grains size are predicated. Meanwhile, the effects of the initial rolling temperature and feed rate of idle roll on material microstructure evolution are analyzed. Finally, the industrial rolling experiment is designed and performed, based on the simulation results. In addition, mechanical and metallographic tests are conducted on rolled bearing ring to get the mechanical parameters and metallographic structure. The experimental data and results show that the mechanical properties of bearing ring produced by casting-rolling compound forming technology are up to industrial standard, and a qualified bearing ring can be successfully formed by employing this new technology. Through the study, a process of forming large bearing ring directly by using casting ring blank is obtained, which could provide an effective theoretical guidance for manufacturing large ring parts. It also has an edge in saving material, lowering energy and improving efficiency.     

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.     

环件径轴向轧制毛坯尺寸设计方法

毛坯尺寸设计是环件径轴向轧制过程优化设计的前提和基础,合理的毛坯尺寸设计,对于成功建立环件径轴向轧制过程、通过包括毛坯在内的过程优化设计以获得精确的环件尺寸和良好性能,具有十分重要的意义.为此,提出一种基于轧比和径轴向变形量分配比的矩形截面环件径轴向轧制毛坯尺寸设计方法,给出毛坯尺寸的计算公式与确定流程,阐明该毛坯尺寸设计方法的特点及应用范围.该方法基于体积不变原理,针对同一环件的轧制,可以设计不同轧比和变形量分配比的多个环坯,为研究不同环坯下的环件径轴向轧制变形行为、工艺规律以及包括毛坯在内的工艺过程优化设计、成形成性一体化调控提供了重要的方法和基础.     

Modeling of on-line measurement for rolling the rings with blank size errors in vertical hot ring rolling process

The size errors of the ring blanks have a considerable effect on the vertical hot ring rolling process and the ring products’ dimensional precision. In this paper, the geometric relationship between the ring’s outer diameter and the measuring roll’s displacement is studied, and then, the influence of the blank size errors on this geometric relationship is analyzed. Subsequently, a modeling method of the measurement model for vertical hot ring rolling process is proposed, that is, the ring’s outer diameter can be measured indirectly through the relations of the ring’s outer diameter with respect to the measuring roll’s displacement and the ring blank’s outer diameter. Using this modeling method, the on-line measurement model of a certain type of vertical hot ring rolling mill was established, and the verification experiments were also conducted. The experiments showed that this on-line measurement model could calculate the ring’s outer diameter precisely, and the absolute errors of the formed rings were less than ±1.5 mm. The research results of this paper have general significance for the on-line measurement and process control of vertical hot ring rolling process.     

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.     

A new mathematical model for predicting the diameter expansion of flat ring in radial–axial ring rolling

An accurate prediction for the diameter expansion is quite essential for the ring rolling with large diameter since it determines the compatibility between the work rolls and the deformed ring in kinematics, so that the rolling stability and the final forming quality of the ring are influenced. A new mathematical model for predicting the diameter expansion of the flat ring in the radial–axial rolling process has been proposed, in which the variation of cross section, the particularity of initial rolling phase, and the effect of slip are all taken into consideration. Based on the proposed mathematical model, a 3D-FEM model for the radial–axial ring rolling process has been developed, and the corresponding experimentation has also been carried out. The diameter expansion in the simulation shows a good agreement with that in the experimentation. The forming quality comparison concerning the circularity, coaxiality, and tilting of the rolled ring has been executed between the former and new proposed method. The result indicates that the new mathematical method is very helpful to control the forming stability and hence improve the ring rolling quality significantly.     

Analysis of plastic penetration in process of groove ball-section ring rolling

Plastic penetration is a necessary condition of ring rolling forming. In this paper, based on the principle of groove ball-section ring rolling and characteristics of plastic penetration, a three dimensional (3D) finite element (FE) analysis model for the plastic penetration of ball groove-section ring is established under the ABAQUS software environment. A decisive factor for plastic penetration behavior, namely the penetration speed of plastic zone, has firstly been ascertained. The distribution pattern of the plastic zone in the process of plastic penetration is revealed by 3D simulation. By researching the diffusion rules of the plastic zone under the conditions of different ring radial thickness and feed speed, the influences of ring radial thickness and feed speed on plastic penetration are obtained. Lastly, the necessary condition for the plastic penetration of groove ball-section ring rolling is summarized, and is validated by experiment and simulation. The achievements of this study expressly reveal the plastic penetration rules of groove ball-section ring rolling, and it’s useful for technology design and production.     

冷辗扩工艺中环件锻透变形的数值分析与试验

冷辗扩机床是目前世界上生产轴承套圈的先进设备.在辗压环件过程中存在着接触非线性和材料非线性双重复杂的变化过程.采用ANSYS有限元分析软件对复杂的辗扩过程进行数值仿真.根据锻透条件,计算出不同工况条件下的最小辗压力,为模具的设计及进给机构参数设计提供了依据.同时进行试验验证分析.     

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.

     

高颈法兰封闭轧制的数值模拟研究

基于DEFORM有限元软件建立了高颈法兰封闭轧制过程的仿真模型,对整个周期的动态轧制过程进行数值模拟分析,分别分析了驱动辊转速、芯辊进给速度对轧制过程以及轧制力的影响规律,并获得了工艺参数的优化指标。研究结果表明,计算机数值模拟对优化工艺参数、提高轧制效率具有重要的意义。     

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。     

大型铝环轧机的研制

为改良大型铝合金环件的生产工艺,研制了环轧机.介绍该轧机的设备组成、生产工艺流程及自动化控制系统.此大型铝环轧机的成功研制为改良大型铝合金环件的生产工艺奠定了基础.     

不锈钢复合板冷轧过程有限元模拟

研究了双金属复合板中不锈钢复合板的冷轧生产工艺,并用大型有限元软件ANSYS模拟了不锈钢复合板的冷轧过程。建立了包括上下辊、轧件在内的二维模型,采取适当的加载和约束条件,对不锈钢复合板的冷轧做了模拟,最后得出了不同压下条件下,轧制变形区域内应力应变分布情况。并分析出不锈钢复合板首道次的压下条件,这与冷轧带钢厂不锈钢复合板实际的生产工艺条件是一致的。