Radial Ring Rolling Research Articles

Determination of microstructure changes by eddy-current methods for cold and warm forming applications

Tangential profile ring rolling (Profiled Radial Ring Rolling, PRRR) enables the fast and compared to machining inexpensive production of bearing rings or similar ring-shaped parts with near net-shape geometry and advantageous material properties due to a high degree of work hardening at a high cadence. Conventionally, a specific heat treatment regime is required to achieve the desired microstructural and mechanical properties such as grain size, hardness or strength. Novel control strategies allow thermomechanical treatment during the forming operation itself. To monitor the evolution of properties during forming, a sensor system based on eddy current methods is presented and its ability to discriminate between various influences is demonstrated. It is shown that different process conditions result in different end-product microstructures, and that these differences both relate to application relevant properties and can be identified using non-destructive eddy current sensing, even in the presence of superposed disturbances such as local variations in electromagnetic properties.

The influence of constraint rolls on temperature evolution and distribution in radial ring rolling

Abstract Producing nearer to net-shape hot rolled rings whilst meeting demanding product property requirements is a major industrial challenge, especially in high value materials such as nickel-based superalloys. Recent process innovations propose additional tooling to improve control over the geometric accuracy, but it is not known what influence this will have on the temperature distribution and product properties. To study this, a set of 24 thermally-coupled numerical simulations was conducted for a key material test case, Inconel 718, with a furnace temperature of 1030 °C. The thermal parameters used in the model were validated against an a newly-conducted full industrial trial, and both average surface temperature prediction and rolling tool temperature were found to be accurate to within ±10 °C. The set of simulations focused on the production of two target ring geometries; for each target ring, four different rolling scenarios were developed, covering a realistic range of machine operating parameters. All eight of these scenarios were simulated with three different tooling set-ups, using two, four and six constraint rolls. For a typical rolling scenario with two constraint rolls, the average surface temperature was found to drop by 79 °C after transfer to the machine, and then by a further 54 °C during rolling. Trebling the number of constraint rolls doubled the temperature drop to 113 °C. By comparison, a factor 2.7 increase in rolling time led to a factor 3.0 increase in temperature loss to 166 °C. Simulations for the second, slenderer, target geometry predicted comparable surface temperature drops, but increased temperature loss in the core of the ring. In Inconel 718 regions of the ring that drop below 900 °C experience strongly retarded dynamic recrystallization, rendering them prone to damage. Trebling the constraint rolls was found to increase the area vulnerable to damage by 0–20%, across the 8 scenarios. These predictions suggest that the influence of constraint rolls could to some extent be mitigated by reasonable reductions in rolling or transfer time. However, if used to produce slenderer, nearer to net-shape rings with larger overall reductions and longer process times then temperature and product property control will be difficult.

An experiment study on a novel constructive hot ring rolling process

The traditional rolling process for large ring part is to forge a large ring blank from a large cast ingot firstly and then ring rolling it to a large ring. However, large ingots are more likely to produce casting defects such as voids and composition segregation. The casting defects will bring hereditation to the final ring product, especially for super-large ring whose dimeter is more than ten meters. In this paper, a novel constructive hot ring rolling method to manufacture the high performance large ring is proposed. In this process, ring blank units are forged by high-quality small ingots firstly. Then the ring blank units are assembled together to a large ring blank and surface welded along the unit interface. Finally, the large assembled ring blank is heated and ring rolled to a large seamless ring. To verify the feasibility of the constructive hot ring rolling process, an experiment of constructive hot ring rolling process was carried out in the laboratory condition. Two separated rings are machined firstly. Then cleaning the surface of the two rings and assembling them together. Follow on, the upper and lower interfaces of the assembled ring are welded in the surface areas. Finally, the ring blank is heated to high temperature and deformed by radial ring rolling. The microstructure status and mechanical properties of the forming ring are tested. It is found that the interface is healed after high temperature rolling. The tensile strength of the constructive rolling ring is close to the ring rolled from a seamless ring blank. The research work can provide a new idea for the manufacturing technology of high performance large ring.

Recent development of ring rolling theory and technique

Rings are basic mechanical components. Ring rolling is a well-known advanced plastic forming technique to manufacture high-performance seamless rings. Since the 21st century, the fast development of global manufacturing has raised an urgent request to high-performance rings, thus, comprehensive and in-depth studies on ring rolling technique were carried out. Based on long-term investigations and attentions on ring rolling, important developments of ring rolling theory and technique in recent 15 years were simply summarised, including the traditional radial ring rolling and radial-axial ring rolling, as well as the novel combined ring rolling. It is expected to give a valuable reference to the research and application of ring rolling.

Recent development of ring rolling theory and technique

Rings are basic mechanical components. Ring rolling is a well-known advanced plastic forming technique to manufacture high-performance seamless rings. Since the 21st century, the fast development of global manufacturing has raised an urgent request to high-performance rings, thus, comprehensive and in-depth studies on ring rolling technique were carried out. Based on long-term investigations and attentions on ring rolling, important developments of ring rolling theory and technique in recent 15 years were simply summarised, including the traditional radial ring rolling and radial-axial ring rolling, as well as the novel combined ring rolling. It is expected to give a valuable reference to the research and application of ring rolling.

Grain refinement limit during hot radial ring rolling of as-cast GCr15 steel

Using hot radial ring rolling to process as-cast blank is a new ring manufacturing technology of high efficiency, high material utilization and low energy consumption. It was customarily considered that larger deformation amount is needed in the new process to obtain smaller average grain size. However, in our work, no further refinement of the average grain size has been found at a certain sufficient deformation amount. Hot radial ring rolling of as-cast GCr15 steel at elevated forging temperature has a grain limit, further deformation produced by this technology does not help overcome this limit. The key explanation to this phenomenon lies in the balance of dynamic recrystallization-induced grain reduction and thermal-induced grain growth occurred during this process. The minimum strain to reach grain limit has been defined and quantified based on the empirical dynamic recrystallization models. The effects of strain and Z parameter on grain limit have been carried out. The optimizing selections of rolling parameters based on grain limit have been discussed. These results obtained provide guidance for grain size controlling and performance improving in the new technology of manufacturing rings.

Precision ring rolling technique and application in high-performance bearing manufacturing

High-performance bearing has significant application in many important industry fields, like automobile, precision machine tool, wind power, etc. Precision ring rolling is an advanced rotary forming technique to manufacture high-performance seamless bearing ring thus can improve the working life of bearing. In this paper, three kinds of precision ring rolling techniques adapt to different dimensional ranges of bearings are introduced, which are cold ring rolling for small-scale bearing, hot radial ring rolling for medium-scale bearing and hot radial-axial ring rolling for large-scale bearing. The forming principles, technological features and forming equipments for three kinds of precision ring rolling techniques are summarized, the technological development and industrial application in China are introduced, and the main technological development trend is described.

The Effect of the Initial Temperature of Ring Blank on Conical Ring Rolling Process

A FE model of radial conical ring rolling process with a closed die structure on the top and bottom part of driven roll (RCRRCDS) process was set up based on ABAQUS/Explicit software. The effect of the initial temperature of conical ring blank on equivalent plastic strain (PEEQ) and temperature distribution of rolled ring, average rolling force and average rolling moment was investigated. The results indicated that with the increase of the initial temperature of ring blank, the PEEQ distribution of rolled ring becomes uniform at first and then less uniform; the temperature distribution gradually becomes homogeneous; and both average rolling force and average rolling moment decrease. When the initial temperature of ring blank is 925°C, the PEEQ distribution of rolled ring is most uniform; the temperature distribution of rolled ring is relatively uniform; the average rolling force and average rolling moment are relatively smaller.

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 H0, outer diameter D0, and thickness t0, 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.

Effect of driver roll rotational speed on hot ring rolling of AZ31 magnesium alloy

Abstract Based on the ABAQUS/Explicit code, A 3D elastic–plastic and coupled thermo-mechanical FE model of radial ring rolling of AZ31 Magnesium alloy has been proposed to analyze the influence of rotational speed of driver roll to study the inhomogeneity distribution of strain and temperature, fishtail coefficient, rolling force parameters. The results show that: (1) when the rotational speed of driver roll n increases, the strain distribution of the rolled ring becomes less homogeneous, and the temperature distribution more homogeneous yet, and leading to an optimal n value; (2) the fishtail coefficient firstly decreases, then increases with the increase of n ; (3) the rolling force, contact area and rolling moment gradually descend with the increase of n .

Plastic deformation behaviors and mechanical properties of rolled rings of 20CrMnTi alloy in combined radial and axial ring rolling

In this paper, a new combined radial and axial ring rolling process is proposed, in which a large increase in both the ring diameter and height can be achieved. Using the finite element (FE) method, the plastic deformation behaviors and mechanical properties of the rolled rings of 20CrMnTi alloy in combined radial and axial ring rolling are numerically investigated. It is found that under different axial rolling ratio λa and radial rolling ratio λr, there are three kinds of plastic deformation behaviors during the process. The first one is that when λa=1 and λr>1, the ring produces the deformation of thickness reduction and diameter expansion and its height basically remains unchanged. The second one is that when λa>1 and λr>1, the ring produces the deformation of thickness reduction, diameter expansion and height increase. The third one is that when λa>1 and λr=1, the ring produces the deformation of thickness reduction, outer diameter constancy and height increase. Owing to these plastic deformation behaviors, the axial and circumferential strain distribution of the rolled rings with the same final geometry is different. To evaluate the mechanical properties of these rolled rings, the compression and tensile tests have been carried out numerically and it is found that the rolled rings with the same final geometry may have different mechanical properties due to the different axial and circumferential strain distribution and the proposed combined radial and axial ring rolling process can thus be adopted to manufacture the rings with the same final geometry but different mechanical properties.

A new cylindrical ring rolling technology for manufacturing thin-walled cylindrical ring

Abstract Ring rolling is an advanced incremental metal forming technology used to manufacture precise seamless rings. Generally, it is classified as two types. One is pure radial ring rolling in which the ring mainly produces the deformation of thickness reduction and diameter expansion and its height basically remains unchanged. The other is radial–axial ring rolling in which the ring produces the deformation of thickness reduction, diameter expansion and height reduction. Obviously, it is difficult for the above two types of ring rolling processes to achieve a large increase in the ring height. Therefore, this paper proposes a new cylindrical ring rolling process which can achieve a large increase in both the ring diameter and height. For evaluating the proposed process, a 3D elastic–plastic FE model of cylindrical ring rolling is first established and its validity is verified by the experiment carried out on a vertical NC ring rolling machine. Then, some fundamental forming characteristics, such as the geometry evolution and strain distribution of the ring, contact characteristics between the rolls and ring and power parameters, are investigated based on this reliable 3D FE model. Finally, the effect of a critical process parameter, axial rolling ratio (circumferential rolling ratio), on the cylindrical ring rolling process is revealed numerically. Through the above analysis, three highlights of the proposed process can be summarized as follows: (1) The stability and final roundness of the deformed ring can be guaranteed easily by the inner surface of the constraint roll without the guide rolls and complicated control schedule. (2) The proposed process can achieve a large increase in both the ring diameter and height. (3) Under the constant radial deformation, different axial and circumferential deformation distribution can be achieved by changing the axial rolling ratio (circumferential rolling ratio).

Effect of friction on combined radial and axial ring rolling process

Combined radial and axial ring rolling is a complicated incremental metal forming process used to manufacture the thin-walled cylindrical rings. During the process, the friction is a critical factor because it has a significant effect on the deformation characteristics of the process. This paper is aimed to reveal the effect of the friction coefficient on the combined radial and axial ring rolling process. For this purpose, a 3D elastic–plastic FE model of the process is first established and its validity is verified by the experiment. Based on this reliable 3D FE model, the effect of the friction coefficient on the geometry development, inhomogeneous deformation of the ring and the power parameters is then investigated numerically.

The effects of forming parameters on conical ring rolling process.

The plastic penetration condition and biting-in condition of a radial conical ring rolling process with a closed die structure on the top and bottom of driven roll, simplified as RCRRCDS, were established. The reasonable value range of mandrel feed rate in rolling process was deduced. A coupled thermomechanical 3D FE model of RCRRCDS process was established. The changing laws of equivalent plastic strain (PEEQ) and temperature distributions with rolling time were investigated. The effects of ring's outer radius growth rate and rolls sizes on the uniformities of PEEQ and temperature distributions, average rolling force, and average rolling moment were studied. The results indicate that the PEEQ at the inner layer and outer layer of rolled ring are larger than that at the middle layer of ring; the temperatures at the “obtuse angle zone” of ring's cross-section are higher than those at “acute angle zone”; the temperature at the central part of ring is higher than that at the middle part of ring's outer surfaces. As the ring's outer radius growth rate increases at its reasonable value ranges, the uniformities of PEEQ and temperature distributions increase. Finally, the optimal values of the ring's outer radius growth rate and rolls sizes were obtained.

Evolution Behavior of Sunking Defect in Forging Rolling Process of Bearing Ring

As an advanced plastic processing technology, forging rolling technology which is consist of hot forging process and radial hot ring rolling process is widely used in the production of small and medium size bearing rings. During the process, sunking defect is easy formed in outer diameter of ring's upper and lower surface's edge. This will increase machining allowance, reduce material utilization and even may lead the ring scrapped. In view of the problem, a whole forging rolling process model of GCr15 bearing ring is established under Transvalor. Forge software environment. The model not only directly reflects evolution process of bearing ring's sunking defect but also reveals the forming mechanism and the rule of evolvement. The impact of hot forging's upsetting radio, hot rolling's feed speed, hot rolling's friction coefficient and hot rolling's initial temperature on the sunking defect of bearing ring are studied. The results show that the sunking defect is more greatly affected by hot forging's upsetting radio,hot rolling's feed speed and hot rolling's friction coefficient than by hot rolling's initial temperature. These will provide a scientific guidance for control the sunking defect in forging rolling process of bearing ring, through the study of the evolution behavior of sunking defect in forging rolling process of GCr15 bearing ring.

A Mandrel Feeding Strategy in Conical Ring Rolling Process

A mathematical model for radial conical ring rolling with a closed die structure on the top and bottom of driven roll, simplified as RCRRCDS, was established. The plastic penetration and biting-in conditions in RCRRCDS process were determined. A mandrel feeding strategy for RCRRCDS process was proposed. The mandrel feed rate and its reasonable value range were deduced. The coupled thermal-mechanical FE model of RCRRCDS process was established. The reasonable value range of the mandrel feed rate was verified by using numerical simulation method. The results indicate that the reasonable value range of the mandrel feed rate is feasible, the proposed mandrel feeding strategy can realize a steady RCRRCDS process, and the forming quality of conical ring rolled by using the proposed feeding strategy is better than that of conical ring rolled by using a constant mandrel feed rate.

Forward Slip and Backward Slip in Radial Ring Rolling Process

During the process of radial ring rolling, relative slip or relative slip tendency occurs on the interface between the ring and the rolls. Research on the relative slip or relative slip tendency plays an important role on reducing friction to ensure the ring rolling smoothly. In this paper, the reason of relative slip or relative slip tendency is investigated that there is speed difference between tangential component of the ring and linear velocity of the rolls. According to speed difference, slip types of the interface are classified. Forward slip coefficient and backward slip coefficient are defined and derived and relations between them are studied. Comparison between the new method and the previous one is conducted via case study, which proves the rationality and effectiveness.

Effects of Rotational Speed of Driver Roll on Hot Ring Rolling of 6061 Aluminum Alloy by 3D FE Simulation

In this paper, a 3D elastic-plastic and coupled thermo-mechanical FE model of radial ring rolling of 6061 aluminum alloy is developed, and the hot rolling process with different the rotational speed of driver roll n is simulated by using the dynamic explicit code ABAQUS/Explicit. The influence laws of the rotational speed of driver roll on the uniformity of strain and temperature distribution (STD), fishtail coefficient, roll force, contact area and roll moment are revealed respectively. One optimum n is obtained, under which SDT is relatively uniform; meanwhile, another optimum n is obtained, under which the quality of end-plane of the rolled ring is the best. The result can provide a valuable guideline to research and optimum of the hot ring rolling of aluminum alloys.

Plastic Instability Criterion of Radial Ring Rolling

The ring is subjected to the combined action of rolling deformation and guide rolls in radial ring rolling process. If the rolling process parameters are designed unreasonably, the ring may be deformed unexpectedly or squashed to waste product. In this article, equation of ring’s bending moment in rolling process is developed based on the mechanical model. Then the stress of ring at any point is analyzed and the maximum stress is found out. The plastic instability criterion of radial ring rolling is also proposed based on the analyses above.

The Stability Evaluation of Radial Ring Rolling

In the Non-stability radial ring rolling process, the ring may collide with the guide roll, making the ring become a polygon. In extreme cases the rolling process could be terminated and the ring be scrapped. The stability evaluation of radial ring rolling has great theory and practice significance. In this article, based on the kinematics theory, a classified research on the dynamic phenomenon of radial ring rolling was done, and a stability evaluation method during the radial ring rolling was put forward. The evaluation provided a good base for the future ring rolling dynamic research.