Billet Rotation Research Articles

Digital Model of Automatic Plate Turning for Plate Mills Based on Machine Vision and Reinforcement Learning Algorithm

Plate turning is an essential step in the plate rolling process. The traditional control mode relies on the manual observation of billets and mainly manual operation. Manual plate turning becomes an external disturbance of the automatic control system of plate mills, which reduces the reproducibility and accuracy of the rolling process. The automatic plate turning function is urgently needed to improve the control level of the rolling line. In this paper, based on the improved image processing algorithm, the position and angle information of the billet conversion process are detected in real time, and the real-time processing of detection data in a complex production environment is realized. Based on the change in the billet rotation angle in the actual plate turning process, a mathematical model is constructed to simulate the plate turning process. On this basis, the digital model and optimization algorithm for automatic plate turning based on reinforcement learning are established, and the automatic optimization of plate turning speed and accuracy is completed. The field application of data-driven plate turning systems replaces manual plate turning control. The plate turning angle detection error of the system is ≤2°. The average plate turning time of each billet is greatly shortened compared with manual plate turning mode, and the fastest time can be shortened by more than 1 s, which greatly improves the production efficiency and is of great significance for improving the automatic control level and digital upgrade of plate mills.

Degree and depth of hardening under pendulum surface plastic deformation of carbon steel

The article discusses influence of the main technological parameters of pendulum surface plastic deformation (SPD) on the mechanical properties of surface layer of cylindrical parts made of carbon steel. Using the hardness tester HBRV-187.5 and the microhardness tester HMV-G21, we determined hardness of the surface layer, microhardness and depth of the work-hardened layer of hardened parts. In addition, the results of calculating the hardening degree are presented, which is important information for evaluating the effectiveness of SPD method in terms of improving the metal mechanical properties. Experimental studies showed that after pendulum SPD (at different processing modes), hardness of the surface layer increases by 9 – 12 % compared to hardness of the original surface, and the microhardness increases by 1.5 – 1.7 times, which leads to a significant hardening of the cylindrical billet surface layer. Depth of the hardened layer varies in the range of 0.9 – 1.1 mm, while the hardening degree is 45 – 65 %. Using the software package Statistica 10.1, which allows solving optimization problems based on statistical analysis and building an optimization model, we determined the optimal modes of hardening by pendulum SPD. These modes simultaneously provide both the maximum depth of the hardened layer and the highest hardening degree of the surface layer. They are formed under the following processing modes: radial interference t = 0.15 – 0.2 mm; longitudinal feed s = 0.07 – 0.11 mm/rev; billet rotation frequency nb = 160 – 200 min−1; frequency of the working tool pendulum movement nt = 110 – 130 strokes/min; angular amplitude of the working tool α = 35 – 40°. According to the results of experimental data and numerical calculations, it was established that the average grain size in pendulum SPD decreases by 30 – 40 % compared to the initial size, and the dislocation density increases by 2.5 times.

High-Temperature Equal-Channel Angular Pressing of a T6-Al-Cu-Li-Mg-Ag-Zr-Sc Alloy

Equal-channel angular pressing (ECAP) is known to induce significant grain refinement and formation of tangled dislocations within the grains. These are induced to evolve to form low-angle boundaries (i.e., cell boundaries) and eventually high-angle boundaries (i.e., grain boundaries). On the other hand, the precipitation sequence of age hardening aluminum alloys can be significantly affected by pre-straining and severe plastic deformation. Thus, ECAP is expected to influence the T6 response of aluminum alloys. In this study, a complex Al-Cu-Mg-Li-Ag-Zr-Sc alloy was subjected to ECAP following different straining paths. The alloy was ECAP at 460 K via route A, C, and by forward-backward route A (FB-route A) up to four passes. That is, ECAP was carried out imposing billet rotation between passes (route A), billet rotation by +90° between passes (route C), and billet rotation by +90° and inversion upside down between passes (FB-route A). The alloy was also aged at 460 K for different durations after ECAP. TEM microstructure inspections showed a marked influence of the different shearing deformations induced by ECAP on the alloy aging response. The precipitation kinetics of the different hardening secondary phases were affected by shearing deformation and tangled dislocations. In particular, the T1-Al2CuLi phase was the one that mostly showed a precipitation sequence speed up induced by the tangled dislocations formed during ECAP. The T1 phase was found to grow with aging time according to the Lifshitz-Slyozov-Wagner low-power regime.

МОДЕЛИРОВАНИЕ КИНЕМАТИЧЕСКИХ ХАРАКТЕРИСТИК ПРОЦЕССА ДВУСТОРОННЕЙ ТОРЦЕШЛИФОВАЛЬНОЙ ОБРАБОТКИ

The paper is dedicated to the bilateral end-finishing improvement at the expense of efficient kinematic characteristics realization in parts machined ensuring limiting errors minimization in end surfaces. 
 A systematization of parts rotation experimental characteristics is carried out. It is shown that they may be referred to six basic kinds. There are offered equivalent characteristics of rotation used while grinding modeling and their mathematical description is given. The dependences obtained determine a kinematic parameter of a shaping form in the equation of the surface worked. 
 There is considered an influence of billet rotation characteristics upon shaping and accuracy of frictionless bearing cylindrical roller machining under virtual technological conditions equivalent to industrial. As a result of computer experiments carried out it is defined that dynamics and balance of shape errors and a relative position of end surfaces of the roller to a considerable extent are defined with the kind of realized rotation characteristics. 
 The error sensitivity of a shape and end beating to kinematic characteristics realized and technological parameters must be taken into account during bilateral end-finishing control.

Influence of Grain Refinement by ECAP on Mechanical and Erosion Corrosion Properties of AISI 4130 Steel: Experimental and Prediction Approach

Sever plastic deformation (SPD) is widely employed to make ultrafine-grained structure (UFGS) materials that satisfy desired properties such as high strength, good tribological properties, and lightweight. Equal channel angular pressing (ECAP) is one of the most important SPD techniques. The current work studies the effect of ECAP passes on mechanical properties, microstructure, and the erosion–corrosion (E–C) resistance of AISI 4130 steel. ECAP at high temperature according to Bc route (billet rotation 90 deg counterclockwise after every pass) was applied and UFGS AISI 4130 specimens with an average grain size of 500 nm were obtained after four ECAP passes. Consequently, the effects of ECAP on the tensile, hardness, and impact properties were investigated. The E–C resistance of unECAPed and ECAPed specimens was evaluated by using seawater slurry with specified sand concentrations. Various microscopes were employed to investigate the microstructure and surface changes due to ECAP and E–C. The results showed that the AISI 4130 steel processed by ECAP has enhanced mechanical and E–C properties. The main mechanisms of E–C are plastic deformation, craters, and small pits. A predication model based on an artificial neural network (ANN) was developed to predict the E–C behavior of both unECAPed and ECAPed materials. The model is able to estimate the weight loss without the need to perform extra experiments. A good agreement between the predicted values and the experimental results was achieved.

Influence of Ultrasonic Finishing on the Surface Roughness of Ship Components

The influence of plastic deformation by ultrasonic smoothing on the surface roughness of 17Kh18N9 and 20Kh1M1F1TR steel billet in finishing is studied. In the experiments, a D-optimal Hartley–Kono design for four factors is employed. The four factors are the speed of billet rotation, the supply, the clamping force, and the ultrasonic power.

Equal-channel angular extrusion of Al 5083 alloy with copper shielding

The microstructural homogeneity, hardness and tensile strength of aluminium alloy 5083, with and without copper shielding (CS), processed by equal-channel angular extrusion (ECAE) are investigated in this work. The two opposite longitudinal faces of the rectangular billets are shielded with copper sheets of various thicknesses (1·0, 1·5, 2·0 and 2·5 mm) and ECAE’d at room temperature in route A (no rotation of billet) up to four times. The required extrusion load is drastically reduced due to the smaller coefficient of friction between the CS and channels of the steel die. The shielded copper reduces the effect of the dead metal zone and microcracks and improves strain uniformity in the extruded alloy. The hardness and tensile strength of the extruded alloy with CS are increased extensively due to newly formed submicron-sized grains in the homogeneous structure. Also, the ductility of ECAE’d alloy with CS is higher compared to that of the alloy extruded without shielding. It is noticed that the increase in the thickness of CS does not have a noteworthy effect on the structural and mechanical behaviour of the extruded alloy.

Effect of processing route on grain refinement in pure copper processed by equal channel angular extrusion

An experimental study of the microstructures in pure copper billets processed by 8 passes of equal channel angular extrusion (ECAE) via an extended range of processing routes with a 90° die is carried out. Each processing route is defined according to the inter-pass billet rotation angle (χ), which varies from 0° to 180°. According to the generation of high-angle boundaries and reduction of grain size by electron backscatter diffraction (EBSD) measurements, the grain refinement is found to be most efficient for route with χ=90° and least efficient with χ=180°, among the seven routes studied. This trend is supported by supplementary transmission electron microscopy (TEM) measurements. Comparison of the EBSD and TEM data reveals the importance of considering the non-equiaxity of grain structures in quantitative assessment of microstructural differences in ECAE-processed materials.

The Origin of Fracture in the I-ECAP of AZ31B Magnesium Alloy

Magnesium alloys are very promising materials for weight-saving structural applications due to their low density, comparing to other metals and alloys currently used. However, they usually suffer from a limited formability at room temperature and low strength. In order to overcome those issues, processes of severe plastic deformation (SPD) can be utilized to improve mechanical properties, but processing parameters need to be selected with care to avoid fracture, very often observed for those alloys during forming. In the current work, the AZ31B magnesium alloy was subjected to SPD by incremental equal-channel angular pressing (I-ECAP) at temperatures varying from 398 K to 525 K (125 °C to 250 °C) to determine the window of allowable processing parameters. The effects of initial grain size and billet rotation scheme on the occurrence of fracture during I-ECAP were investigated. The initial grain size ranged from 1.5 to 40 µm and the I-ECAP routes tested were A, BC, and C. Microstructures of the processed billets were characterized before and after I-ECAP. It was found that a fine-grained and homogenous microstructure was required to avoid fracture at low temperatures. Strain localization arising from a stress relaxation within recrystallized regions, namely twins and fine-grained zones, was shown to be responsible for the generation of microcracks. Based on the I-ECAP experiments and available literature data for ECAP, a power law between the initial grain size and processing conditions, described by a Zener–Hollomon parameter, has been proposed. Finally, processing by various routes at 473 K (200 °C) revealed that route A was less prone to fracture than routes BC and C.

The Effect of Initial Grain Size on Formability of AZ31B Magnesium Alloy during I-ECAP

The goal of this work was to investigate formability of AZ31B magnesium alloy during incremental equal channel angular pressing (I-ECAP). Square billets were processed using different routes of I-ECAP at temperatures varying from 125 °C to 250 °C. The billets were obtained from commercially available coarse-grained, hot-extruded rod and fine-grained, hot-rolled plate. A strong influence of the initial microstructure on processing temperature was reported. Fine-grained samples were successfully processed at 200 °C, while coarse-grained ones must have been heated up to 250 °C to avoid fracture. A gradual temperature decrease with subsequent passes allowed successful pressing at 150 °C. Processing using various routes of I-ECAP showed that a billet rotation before the last pass had strong influence on mechanical properties. The results of experiments were plotted on the diagram of allowable processing temperature for AZ31B. It was found that the relation between the minimum temperature in I-ECAP and the initial grain size could be described by a logarithmic equation.

Grain Refinement in Pure Aluminum Severely Deformed by Equal Channel Angular Extrusion via Extended Processing Routes

AA1060 pure aluminum billets were processed by eight passes of equal channel angular extrusion (ECAE) using 90 and 120 deg dies via processing routes characterized by an inter-pass billet rotation angle (χ) varying from 0 to 180 deg. The grain refinement efficiencies achieved in the different processing conditions were investigated by comparing misorientation and grain size in the deformed samples measured by electron back-scatter diffraction. The results reveal an overall decrease of grain refinement efficiency with an increase of χ for both dies. This trend corroborates the general observations in various face-centered cubic metals processed using a 120 deg die and can be satisfactorily explained by correlating the relative grain refinement efficiency to the relative significance of newly activated slip systems at pass-to-pass transitions. For ECAE with the 90 deg die, the route-dependency of grain refinement found in the AA1060 samples contradicts some of the observations in the literature, and the main discrepancies are located for routes with χ = 0 to 90 deg. Comparison of the present results with those of pure copper processed under similar conditions further reveals that these discrepancies could be mainly ascribed to differences in the characteristics of the materials, and that it is irrational to simply claim the route with χ = 0 or 90 deg as the optimal route without necessary experimental validations for a specific material.

Rotatory Condition at Initial Stage of External Spline Rolling

In spline rolling process, the billet is mainly driven by frictional moment at initial forming stage that from starting rolling to billet/workpiece rotated half circle. If the rotation of billet is not normally driven by rolling die, then the motion between billet and rolling die is not coordinated, and then dividing precision of external spline will be reduced. Thus, the rotatory condition of rolled billet was established in this work. The rotatory condition for the rolling process of spline with even number of teeth is different from that with an odd number of teeth. However, the changing trends for both rotatory conditions are the same. The results indicated that (i) the rotatory condition can be improved when the friction between die and billet increases or the outside diameter of rolling die increases, (ii) the rotatory condition for odd number of teeth is better than that for even number of teeth, and (iii) the outside diameter of rolling die should be five times greater than the diameter of billet before rolling according to the rotatory condition. The reasonable decrement can be selected by comprehensive considering of rotatory condition and geometry of rolling die.

Intensive Shear Deformation in Billets During Forging with Specially Formed Anvils

Classification of forging schemes which involve intensive shear deformation in the billet have been proposed. An investigation of the stress-strain state in the billet during forging by anvils with slant has been done. The influence of such parameters as relative billet feed, anvil stroke, and anvil slant angle on billet strain state during the forging process has been determined. Recommendations of forging regimes in the form of such parameters as billet feed, anvil stroke, anvil slant angle, and billet rotation sequence have been made. The feasibility of forging a 41Cr4 steel billet with slanted anvils as a round shaft was confirmed experimentally, and the advantages of this new scheme over traditional flat anvil forging have been identified.

Role of strain path change in grain refinement by severe plastic deformation: A case study of equal channel angular extrusion

Equal-channel angular extrusion (ECAE) provides exciting opportunities to explore the role of strain path change (SPC) in grain refinement by severe plastic deformation (SPD). In this study, crystal plasticity simulations were carried out using a viscoplastic self-consistent model for a face-centered cubic model material processed via an extended range of processing routes and with two die angles (90° and 120°). Each processing route was defined according to the interpass billet rotation angle (χ), which varied from 0° to 180° at intervals of 15°. Based on a statistical analysis of the simulated slip activities, it is proposed that differences in grain refinement among these cases can be best correlated to key differences in the slip activities, i.e. the significance of newly activated slip systems at pass-to-pass transitions corresponding to macroscopic SPCs. Accordingly, grain refinement is anticipated to be most efficient for routes with χ near 75° for the 90° die or 0–45° for the 120° die, and least efficient with χ near 180° for both dies. The relative grain refinement efficiencies thus predicted are in good overall agreement with those indicated by the generation of high-angle boundaries and reduction of grain size in pure copper measured by electron back-scatter diffraction. It is suggested that the effect of SPC and the resulting characteristic slip activities should be incorporated in understanding the effectiveness of grain refinement and unpinning the underlying grain subdivision mechanisms in SPD with different SPCs.

기공닫힘부 폐쇄정도 결정을 위한 평가방법 연구

This paper presents methods for analyzing the extent of cylindrical-shaped void closure. In addition, a quantitative relationship between change in void fraction and height reduction ratio of a compressed specimen is proposed. The height reduction ratio, number of deformation steps and billet rotation were chosen as key process parameters influencing the void closing behavior, namely, the changes in void shape and size during hot open die forging of a large ingot. The extent of void closure was analyzed from microscopic observations and estimated from tensile test results. The tensile strengths of specimens with closed voids and those without were compared for various reduction ratios in height. The results confirmed that void closure occurs at reduction ratios greater than 30 %. The void closing behavior could be expressed as a hyperbolic tangent function of reduction ratio in height, number of paths, and billet rotation. The knowledge presented in this paper could be helpful for optimizing deformation paths in open die forging processes.

대형 잉곳의 기공압착 효과 향상을 위한 폐쇄조건 연구

In this work, the closing behavior of cylindrical-shaped voids was experimentally investigated according to various parameters such as reduction ratio in height, initial void size and billet rotation during hot open die forging process. The reduction ratio in height, number of path, and billet rotation were chosen as key process parameters which influence the void closing behavior including the change of void shape and size. On the other hand, values of die overlapping and die width ratio were set to be constant. Void closing behavior was estimated by microscopic observation. Based on the observations, it was confirmed that application of billet rotation is more efficient to eliminate the void with less reduction ratio in height. The experimental results obtained from this study could be helpful to establish the optimum path schedule of open die forging process.

Grain Refinement Efficiency in Equal Channel Angular Extrusion of FCC Metals Inferred from Crystal Plasticity Simulations of Slip Activities

Equal channel angular extrusion (ECAE) is a relatively new technique to produce ultrafine-grained materials by severe plastic deformation. Its efficiency of grain refinement varies with the processing route, i.e. the billet rotation () about its longitudinal axis between successive passes. The influence of processing route can not be fully explained by existing theories that consider only the macroscopic deformation features. In this study, the mesoscopic deformation behavior during multi-pass ECAE of face-centered cubic (FCC) metals was simulated using a visco-plasticity self-consistent (VPSC) polycrystal model and assuming simple shear deformation in each pass. It is shown that the slip activities vary significantly at the transitions between successive passes, depending on the die angle and processing route. The efficiencies of grain refinement in the different cases can be well correlated to the contribution of slip systems newly activated in a subsequent pass. The grain refinement is more efficient when such contributions are higher, such as in route B ( = 90) with a 90 die or route A ( = 0) with a 120 die. These crystal plasticity simulations provide insights into the efficiency of grain refinement during severe plastic deformation with strain path changes.

X-Ray Diffraction Studies of Grain Growth in an Ultra-fine Grained 6060 Aluminium Alloy

In-situ synchrotron X-ray diffraction has been applied in order to study grain growth in an ultra-fine grained (D~400 nm) 6060 aluminium alloy at 270°C. The submicron grain structure was produced by Equal Channel Angular Pressing (ECAP) to an effective strain of ~6 without rotation of the billet. As the material was textured after ECAP, the initial stages of grain growth were seldom detected, but in the grain size interval available for studies a grain growth exponent of 3.6±0.3 was obtained. By interpolation of the grain growth curves to D=D0 (determined by EBSD) the effect of growth on the softening of the alloy was estimated. The interpolated average curve indicates that the initial stages of softening are not due to uniform grain growth, but rather reconfiguration and annihilation of dislocations as well as overaging of hardening precipitates.

Molecular Dynamics Study on Grain Refinement Process of α-Iron by Equal Channel Angular Pressing under Quasi 3-Dimensional Condition

Equal Channel Angular Pressing (ECAP) has potentiality for producing ultrafine-grained polycrystalline metals in bulk with very high yield stress and excellent workability, under an optimized processing condition. In this study, molecular dynamics (MD) simulations were performed in order to reveal the dependence of metallographic structure evolution on the processing route, and also to clarify the grain refinement mechanism in α-iron by ECAP with a 90° die. We used Lees-Edwards periodic boundary condition to impose a severe plastic deformation which is ideally equivalent to the simple shear deformation produced at the intersecting plane of two channels. The transition of the internal structure during 4 passes were investigated for the feasible four kinds of processing route under quasi 3-dimensional condition. It is shown that the twinning deformation is dominant for the analyzed material, and the texture evolution is notably affected by the relationship between applied simple shear direction and the characteristic crystal orientation which can easily cause twinning deformation. The simplest processing route with no rotation of billet between passes, which is called Route A in general, is the most efficient route in the presently analyzed cases. This is because the twinning deformation along the simple shear direction intersects with the twin boundaries which are developed by stress component conjugate to the simple shear.

Texture of IF steel after equal channel angular pressing (ECAP)

Based on experimentally measured textures of interstitial free steel, this paper shows how the textures after equal channel angular pressing (ECAP) via routes A and C, up to 4 passes, can easily be understood by means of a rotation field for simple shear. The rotation field was taken from the literature, and results from a full constraint Taylor rate sensitive calculation for simple shear, assumed to act parallel to the die channel’s intersection plane. Isolation of the effect of one billet rotation explains why the microstructures obtained via routes A and C are very different, even though both routes imply strain reversal between passes. The application of this analysis to the textures after ECAP via routes B A and B C is less self-evident, because for these routes the plane of plane strain changes from one pass to another.