Hot Ring Research Articles

Establishment of Hot Processing Maps and Hot Ring Rolling Process of 42CrMo Steel

Establishment of Hot Processing Maps and Hot Ring Rolling Process of 42CrMo Steel

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.

Acidity‐Promoted Cellular Uptake and Drug Release Mediated by Amine‐Functionalized Block Polycarbonates Prepared via One‐Shot Ring‐Opening Copolymerization

This paper reports a drug nanovehicle self-assembled from an amine-functionalized block copolymer poly(6,14-dimethyl-1,3,9,11-tetraoxa-6,14-diaza-cyclohexadecane-2,10-dione)-block-poly(1,3-dioxepan-2-one) (PADMC-b-PTeMC), which is prepared by controlable ring-opening block copolymerization attractively in a "one-shot feeding" pathway. The copolymers display high cell-biocompatibility with no apparent cytotoxicities detected in 293T and HeLa cells. Due to their amphiphilic nature, PADMC-b-PTeMC copolymers can self-assemble into nanosized micelles capable of loading anticancer drugs such as camptothecin (CPT) and doxorubicin (DOX). In particular, the outer PADMC shell endows the PADMC-b-PTeMC nanomicelles with pH-dependent control over the micellar morphology, cell uptake efficiency, and the drug release pattern. Confocal inspection reveals the remarkably enhanced cellular internalization of drug loaded micelles by cancerous HeLa cells at relatively lower pH 5.8 simulating the mildly acid microenvironment in tumors. Along with the acidity-triggered volume expansion of micelles, an accelerated CPT release in vitro occurs. The obtained results adumbrate the possibility of completely biodegradable PADMC-b-PTeMC as pH-sensitive drug carriers for tumor chemotherapy.

Reduction of friction of steel covered with oxide scale in hot forging

The hot ring compression test of chrome steel covered with an oxide scale film is carried out to examine the effects of the oxide scale film on the hot forging characteristics through experiment and finite element analysis. The nominal coefficient of shear friction of the scale is estimated from the plastic deformation behavior of the chrome steel covered with oxide scale film. The estimated coefficient of shear friction of the oxide scale is found to be lower than that of the chrome steel. The plastic deformations and temperature changes of the chrome steel workpiece and the oxide scale layer are calculated using finite element analysis method to investigate the mechanism underlying the reduction in the friction during the hot forging of chrome steel covered with an oxide scale film. Low friction and thermal conductivity values of the oxide scale lead to low forging load in the hot forging of chrome steel covered with an oxide scale film.

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.

Application of a Material Model to Predict Rolling Forces and Microstructure during a Hot Ring Rolling Process

Ring rolling is an incremental bulk forming process. Hence, the process consists of a large number of alternating deformations and dwell steps. For accurate calculations of material flow and thus ring geometry and rolling forces in hot ring rolling processes, it seems necessary to consider material softening due to static and post dynamic recrystallization which could occur between two deformation steps. In addition, due to the large number of cycles, the modeling results, especially the prediction of grain size, can easily be affected by uncertainties in the input data. However, for small rings and ring material with slow recrystallization kinetics, the interpass times can be short compared to the softening kinetics and the effect of softening can be so small, that microstructure evolution and the description of the materials flow behavior can be de-coupled. In this paper, a semi-empirical JMAK-based model for a stainless steel (1.4301/ X5CrNi18-9/ AISI304) is presented and evaluated by the use of experiments and other investigations published in [1],[2]. Finite Element (FE) simulations of a ring rolling process with a high number of ring revolutions and thus multiple, incremental forming steps were conducted based on ring rolling experiments. The FE simulation results were validated with the experimentally derived rolling force and evolution of ring diameter. The microstructure evolution was calculated in a post processing step considering the investigated evolution of strain and temperature. In this calculation the interrelations between the fraction of dynamically recrystallized microstructure, the evolution of post-dynamically recrystallized microstructure and the final grain size have been considered. Both, the calculated final microstructure and the evolution of rolling force and ring geometry calculated stand in good agreement with the experimental investigations.

Analytical Description of a Dead Spot in a PEM Fuel Cell Anode

Polymer electrolyte membrane fuel cells (PEMFCs) are close to commercialization, with automotive companies expected to begin mass production of PEMFC–powered cars in the next few years. Nonetheless, the lifetime of fuel cells still needs to be substantially improved to make this technology less expensive and more reliable. Over the past decade, large efforts have been directed toward understanding the microscopic mechanisms of PEMFC degradation. 1 Some of these mechanisms include parasitic electrochemical reactions, which run many orders of magnitude faster in the domains where the reaction overpotential is larger. This raises the problem of local non–uniformities in fuel cells, which can produce large local overpotentials. In this work, we continue the study of a problem of potentials and current distributions in the domain near a dead spot in the anode catalyst layer of a PEMFC. The spot of no or low electrochemical activity may arise due to local poisoning of the catalyst surface, or due to delamination of the anode catalyst from the membrane. Last but not least, this problem arises in the transmission X–ray absorption spectroscopy of the PEMFC cathode. 2,3 Transmission XAS requires removal of Pt atoms from a small circular anode “window” to make it transparent to X–rays probing the state of Pt atoms in the cathode catalyst layer (CCL). In a previous analysis, the problem has been formulated and solved numerically. 4 The numerical solution reveals the formation of a current double layer (CDL) at the spot boundary. The main feature of this layer is a high HOR current density generated in a narrow ring just outside the spot (“hot ring”). Here, we report an analytical solution of the problem. This solution allows us to derive a simple relation for the characteristic width of the hot ring. The solution confirms the conjecture of 4 that the CDL is an autonomous structure, which is independent of the spot radius.

Hard x-ray tomographic studies of the destruction of an energetic electron ring

A tomography system was designed and built at the Large Plasma Device to measure the spatial distribution of hard x-ray (100 KeV-3 MeV) emissivity. The x-rays were generated when a hot electron ring was significantly disrupted by a shear Alfvén wave. The plasma is pulsed at 1 Hz (1 shot/s). A lead shielded scintillator detector with an acceptance angle defined by a lead pinhole is mounted on a rotary gimbal and used to detect the x-rays. The system measures one chord per plasma shot using only one detector. A data plane usually consists of several hundred chords. A novel Dot by Dot Reconstruction (DDR) method is introduced to calculate the emissivity profile from the line integrated data. In the experiments, there are often physical obstructions, which make measurements at certain angles impossible. The DDR method works well even in this situation. The method was tested with simulated data, and was found to be more effective than previously published methods for the specific geometry of this experiment. The reconstructed x-ray emissivity from experimental data by this method is shown.

AN INTERFEROMETRIC STUDY OF THE FOMALHAUT INNER DEBRIS DISK. II. KECK NULLER MID-INFRARED OBSERVATIONS

We report on high contrast mid-infrared observations of Fomalhaut obtained with the Keck Interferometer Nuller (KIN) showing a small resolved excess over the level expected from the stellar photosphere. The measured null excess has a mean value of 0.35% +/- 0.10% between 8 and 11 microns and increases from 8 to 13 microns. Given the small field of view of the instrument, the source of this marginal excess must be contained within 2AU of Fomalhaut. This result is reminiscent of previous VLTI K-band observations, which implied the presence of a ~ 0.88% excess, and argued that thermal emission from hot dusty grains located within 6 AU from Fomalhaut was the most plausible explanation. Using a parametric 2D radiative transfer code and a Bayesian analysis, we examine different dust disk structures to reproduce both the near and mid-infrared data simultaneously. While not a definitive explanation of the hot excess of Fomalhaut, our model suggests that the most likely inner few AU disk geometry consists of a two-component structure, with two different and spatially distinct grain populations. The 2 to 11 microns data are consistent with an inner hot ring of very small (~ 10 to 300 nm) carbon-rich grains concentrating around 0.1AU. The second dust population consists of larger grains (size of a few microns to a few tens of microns) located further out in a colder region where regular astronomical silicates could survive, with an inner edge around 1AU. From a dynamical point of view, the presence of the inner concentration of sub-micron sized grains is surprising, as such grains should be expelled from the inner planetary system by radiation pressure within only a few years. This could either point to some inordinate replenishment rates (e.g. many grazing comets coming from an outer reservoir) or to the existence of some braking mechanism preventing the grains from moving out.

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.

Metadynamic recrystallization of the as-cast 42CrMo steel after normalizing and tempering during hot compression

The existing researches of hot ring rolling process are mainly based on forged billet. Compared with the existing process, the new ring casting-rolling compound forming process has significant advantages in saving materials and energy, reducing emission and reducing the production cost. The microstructure evolution of the casting materials during hot deformation is the basis of the research of the new process. However, the researches on the casting materials are rare. The metadynamic recrystallization of the as-cast 42CrMo steel after normalizing and tempering during the hot compression is investigated. The tests are performed on the Gleeble-1500 thermal-mechanical simulator. The influence rule of the deformation parameters on the metadynamic recrystallization is obtained by analyzing the experimental data. The kinetic model of the metadynamic recrystallization is deduced. The analysis results show that the metadynamic recrystallization fraction increases with the increase of the deformation temperature and the strain rate. The metallographic experiments are used to investigate the influence rule of the deformation parameters on the grain size of the metadynamic recrystallization. The experimental results show that the grain of the metadynamic recrystallization could be refined with the increase of the strain rate and the decrease of the deformation temperature during hot compression. The occurrence of the metadynamic recrystallization during the hot deformation is more difficult in as-cast 42CrMo steel than in forged 42CrMo steel. The research can provide the foundation for the further research of the hot deformation behaviors of the as-cast structure and theoretical support for the new ring casting-rolling compound process.

Investigation of deformation degree and initial forming temperature dependences of microstructure in hot ring rolling of TA15 titanium alloy by multi-scale simulations

Hot ring rolling is a preferred technology for manufacturing high-quality titanium alloy rings. During the process, the material undergoes complex microstructure evolution which determines the mechanical properties of the rolled ring. In this study, an internal state variable microstructure model for the hot working of TA15 titanium alloy is implemented into the 3D-FE model of hot ring rolling process under ABAQUS environment to realize multi-scale simulation of the process. Then the effects of deformation degree and initial forming temperature on the microstructure of TA15 titanium alloy in hot ring rolling are investigated numerically. The results show that: (1) with increasing deformation degree, the volume fraction and grain size of primary α phase in the ring both decrease, and the primary α phase distribution becomes more nonuniform while the primary α grain size distribution becomes more uniform; (2) with increasing initial forming temperature, the volume fraction and grain size of primary α phase both decrease, and the uniformity of primary α phase distribution gets better first and then worse while the uniformity of primary α grain size distribution gets better; and (3) in order to obtain uniform distributions of both primary α phase and grain size, an optimum process condition for hot ring rolling of TA15 titanium alloy is suggested to be the deformation degree of 0.25–0.35 and the initial forming temperature of 930–940°C. The results can serve as a guide to the microstructure control, blank size design and processing parameter optimization for hot ring rolling of titanium alloy.

Microstructure evolution modeling of titanium alloy large ring in hot ring rolling

Exploration of microstructure evolution is of significance for manufacturing the large ring with high performance and high reliability in hot ring rolling. In the study, the microstructure evolution model and the rate-/temperature-/microstructure-dependent constitutive model of titanium alloy are implemented in ABAQUS/Explicit through the user material subroutine VUMAT. The developed subroutine is validated by single-element models and isothermal upsetting experiments of Ti–6Al–4V cylinder. The subroutine is imbedded into a coupled thermomechanical three-dimensional finite element (3D-FE) model for hot rolling of Ti–6Al–4V large ring. The evolution characteristics of β phase volume fraction and grain size of Ti–6Al–4V during the process are revealed, and the final microstructures of the large ring under different processing conditions are explored. The results obtained show that (1) microstructure evolution follows the trend with the process progressing: the fine grain zone transfers from the surface layer (SL) to the middle layer (ML) of the ring; the poor β zone extends from the outside of the SL to the end-plane of the ML, and the rich β zone always locates at the SL. (2) decreasing the rotational velocity of the driver roll n1, or increasing the feed rate of the idle roll v or the initial temperature of the ring T0 contributes to more uniform distributions of β phase and its grain size, but results in the increase of the β phase volume fraction and grain size.

Instability and propagation of EMIC waves in the magnetosphere by a kappa distribution

Electromagnetic ion cyclotron (EMIC) waves are excited near the magnetic equator by anisotropic ring current ions with energies near a few tens of keV. We investigate the instability and the path‐integrated gain of EMIC waves during wave propagation. Calculations are performed by a global core density model, a field‐aligned density model and particularly the hot ring current ions modeled by a kappa distribution. Simulating results show that the instability of EMIC waves is influenced primarily by the parameters of hot ring current ions, the wave normal angle and the composition of background plasma. A larger path‐integrated gain occurs when the initial wave vector points toward lower L shells. During the storm main phase, the most common EMIC wave is the He+ band wave which occurs in the outer magnetosphere beyond the plasmapause with frequency just below the cyclotron frequency of He+. During the recovery phase, EMIC wave occurs in H+ band and He+ band with almost the same intensity in cases of interest. The O+ band EMIC waves are very weak and quite rare. This result presents a further insight into propagation and instability of EMIC waves under different geomagnetic activities.

On the origin of the cold spot

In a concordant Λ cold dark matter model, the large-angle cosmic microwave background (CMB) temperature anisotropy due to linear perturbations in the local universe is not negligible. We explore a possible role of an underdense region (void) that may cause an anomalous cold spot (CS) in the CMB sky. Although the observed anomalous cold region with a surrounding hot ring can be produced by an underdense region surrounded by a massive wall, a decrement in the CMB temperature in the line of sight is suppressed because of the blueshift of CMB photons that pass the wall. Therefore, undercompensated models give better agreement with the observed data in comparison with overcompensated or compensated models. We find that it is likely that ∼90 per cent of the CMB fluctuation is generated due to an overdense region surrounded by an underdense region at the last scattering surface, and the remaining ∼10 per cent is produced due to a single spherical underdense region with a radius r∼ 6 × 102h−1 Mpc and a density contrast δm∼−0.009 (2σ) at redshift z∼ 1 in the line of sight to the CS. The probability of having such two aligned structures is ∼0.7 per cent if the perturbed region at z∼ 1 is moderately undercompensated.

Influences of Geometric Factors on Rolling Force and Moment in Hot Ring Rolling of Large Parts

For hot ring rolling of large parts, rolling force and moment are of significance for designing, choosing and optimizing of rolling die and mill. In the study, the average shape parameter of the deformation zone of ring rolling is presented first, and then a reliable coupled thermo-mechanical three-dimensional (3D) finite element (FE) model for the process is developed. Finally, the influences of geometric factors on rolling force and moment during hot ring rolling of titanium alloy large parts are explored. The main results show that increasing the ratio of driver roll radius to idle roll radius or decreasing the average radius of blank is beneficial to a saving of rolling force and moment, while the axial height of blank has a little influence.

Semi‐optical in‐process‐metrology to determine the roundness deviation of bearing rings during heat treatment

AbstractThis paper presents two different systems for measuring the roundness deviation of bearing rings during heating and gas quenching. During heating in a furnace, laser triangulation is applied to measure absolute values for the ring's mean radius and ovality. Afterwards, the ring is quenched in a gas nozzle field equipped with a semi‐optical measurement system consisting of twelve tactile and twelve optical sensors independent from each other. Before quenching, the tactile sensors measure in‐situ the absolute mean radius of the near 900°C hot ring and its roundness deviation from ovality up to pentagonality. Based on this information, the optical sensors measure in‐process the change of the roundness deviation during the gas quenching, as the tactile sensors cannot be used in high speed gas jets due to turbulence.

3ロール型，2ロール型リングローリングにおける<br>変形特性の実験的研究

Hot ring rolling is a useful process for producing large seamless rings such as bearing races for ships, airplanes and windmills. Ring rolling is classified into two types, i.e., two-roll-type and three-roll-type, by roll layout. A two-roll-type ring rolling mill is generally used for manufacturing processes. On the other hand, a three-roll-type ring rolling mill has fewer applications, and therefore has been less studied. In this study, the deformation characteristics in both types of ring rolling were investigated experimentally. It is found that the deformation characteristics near the center of the width of the ring in three-roll-type ring rolling are similar to those observed under plane strain compression. In this region, fiber flow toward the outer side is observed. It is also found that three-roll-type ring rolling shows less lateral spread and more uniform deformation than the two-roll-type process without axial rolls.

Numerical Simulation Key Technical Research of Hot Bend-Forming of Auto Windshield

Three-dimensional simplified model of auto windshield, mold, hot ring and quench ring was built using UG software in this article. Hot bend-forming numerical simulation process of auto windshield was reserched based on Show-implicit sequence solving algorithm. Finite element dynamic display simulation of press and drop forming and rebound deformation work step were finished. Distortion status, stress and strain distribution in forming process could be real-time displayed. It compared measured value and simulated value in two ways (bending depth and rebound rate) in the three groups product samples randomly selected.The comparison result proved the veracity of numerical simulation result. It had certain actual production guiding significance.

Investigation on Constant and Variable Feed Speeds Effects in Ring Rolling Process Using 3D FEM

Although cold ring rolling (CRR) process is largely used in the manufacturing of profiled rings like bearing races, research on this purpose has been scant. In this study, based on a validated finite element (FE) model, CRR process is simulated regarding the variable and constant feed speeds of the mandrel roll which lead to constant and variable values of the ring's diameter growth rates respectively using a 3D rigid-plastic finite element method (FEM). Major technological problems involved in the process including plastic deformation behavior, strain distribution and its uniformity, Cockcroft and Latham damage field and final outer diameter of ring are fully investigated. The results of simulations would provide a good basis for process control especially feed speed controlled mills and guiding the design and optimization of both cold and hot ring rolling process.