Investigation of Lateral Confinement, Roller Aspect Ratio and Wear Condition on HPGR Performance Using DEM-MBD-PRM Simulations

It has been known that the performance of high-pressure grinding rolls (HPGR) varies as a function of the method used to laterally confine the rolls, their diameter/length (aspect) ratio as well as their condition, if new or worn. However, quantifying these effects through direct experimentation in machines with reasonably large dimensions is not straightforward, given the challenge, among others, of guaranteeing that the feed material remains unchanged. The present work couples the discrete element method (DEM) to multibody dynamics (MBD) and a novel particle replacement model (PRM) to simulate the performance of a pilot-scale HPGR grinding pellet feed. It shows that rotating side plates, in particular when fitted with studs, will result in more uniform forces along the bed, which also translates in a more constant product size along the rolls as well as higher throughput. It also shows that the edge effect is not affected by roll length, leading to substantially larger proportional edge regions for high-aspect ratio rolls. On the other hand, the product from the center region of such rolls was found to be finer when pressed at identical specific forces. Finally, rolls were found to have higher throughput, but generate a coarser product when worn following the commonly observed trapezoidal profile. The approach often used in industry to compensate for roller wear is to increase the specific force and roll speed. It has been demonstrated to be effective in maintaining product fineness and throughput, as long as the minimum safety gap is not reached.

Study on Minimum Rollable Thickness in Asymmetrical Rolling

A new model for the asymmetrical rolling is proposed to calculate the minimum rollable thickness simply and fast by the slab method. The calculation formulas of the rolling pressure, the rolling force, the critical roll speed ratio and the critical front tension under different deformation zone configurations are proposed, and the deformation zone configuration - rolling parameters relationship diagram is given and analyzed. The results show that the minimum rollable thickness can be reached when the rolling parameters keep the deformation zone configuration as cross-shear zone + backward-slip zone (C+B) or all cross-shear zone (AC). The calculation formulas of the minimum rollable thickness and the required rolling parameters for different deformation zone configurations are proposed respectively. The calculated value is in good agreement with the experimental results.

Casting of Al-Mg Strip Using Single Roll Caster Equipped with a Scraper

A scraper was attached to an unequal-diameter twin-roll caster without requiring large modifications. This caster was used as a 1000 mm diameter single roll caster equipped with a scraper, and its strip casting ability was tested. The effects of the scraper angle and load, the roll speed, and the pouring temperature of the molten metal on the scribed surface, thickness distribution and average strip thickness were investigated. The scribed surface characteristics were sound and the thickness distribution was flat when the scraper angle was 60° and the scraper load was in the range of 1 to 4 kg. When the scraper load was more than 1 kg, the thickness distribution was uneven. The average strip thickness decreased as the roll speed increased. The pouring temperature of the molten metal influenced the evenness of the solidified layer thickness. The solidified layer became even as the molten metal temperature was decreased. A strip cast with the determined optimal conditions was then cold rolled down to 1 mm to improve its surface quality.

Investigation of the effect of several parameters on the applicability of magnetic separation method

Purpose. This research investigates the separation process performed by a magnetic separator. The magnetic separation process is used to isolate ferrous materials from those which are not. Hence, a prototype of a dry magnetic separator is designed. It should be said that this study defines the effect of different parameters (roll speed, magnetic force, and mass of silica sand particle) on separation efficiency. Methodology. The influence of several parameters of the magnetic separator such as magnetic force, centrifugal force, and properties of particle (mass, shape, etc.) were studied theoretically and simulated by SolidWorks software. The optimum conditions of the magnetic separator were obtained, and several trials were performed to find the point that results in a lower effect of roller speed and a higher effect of the magnetic force on the particle in order to achieve higher separating efficiency. Findings. The results show that the centrifugal force are the most important variable influencing separating efficiency. Moreover, it was found that blade angle magnitude of (174) degree with magnetic force between (1.71E-05 to 6.3E-05 N) and roll speed from (84 to 105 rpm) are the optimum separating conditions to reach higher rate of the separating process. Originality. This is the first time that the effect of the gap distance between the magnet and the feeding particles on the magnetic force has been studied. Furthermore, the effect of centrifugal force on magnetic separator force is investigated theoretically and numerically in order to be compared for different parameters. Practical value. The new prototype design of the magnetic separating unit is promising and efficient since the parameters can be varied based on the type and characteristics of materials. It is also revealed that separating time of the materials is reduced. Hence, this type of construction of a magnetic separator is recommended for industrial applications.

Regulating the Coordinates of the Electromechanical System of the Rolling Mill Based on the Elastic Torque Observer

The paper considers the electromechanical system of the reversing stand of the plate rolling mill 5000 of PJSC “Magnitogorsk Metallurgical Plant” (PJSC “MMK”). The performed experimental studies of transient processes in the mode of gripping metal by rolls allowed establishing unacceptable dynamic loads of an oscillatory nature and a loss of controllability of the electric drive. This confirms the need for the development of control methods that limit the motor and spindle torques. It is noted that the known control systems for the speed modes of an electric drive, which decrease the elastic moment due to the preliminary closing of the angular gaps, are, in essence, open-loop speed control systems. This does not provide for the controlled regulation of coordinates in dynamic modes. The paper proposes the development of a closed system for automatic control of coordinates of a two-mass electromechanical system with an observer of the moment of the elastic shaft and the speed of the second mass. An observer of the unmeasurable parameters of a two-mass rolling mill system has been developed. It provides an indirect determination (recovery) of the roll speed and the spindle torque in on-line mode. It is based on a system of equations in the state space. By comparing the reconstructed and experimentally obtained transient processes, the satisfactory accuracy of the results has been confirmed. Based on the proposed observer, the authors developed an automatic control system (ACS) of the roll speed with subordinate contours of the elastic shaft moment, speed and engine torque. The setting of closed-loop regulators has been substantiated. Transient processes of moments and velocities are considered at impact application of a load with increased speed of the second mass speed control loop. The analysis of the LAFC and LPFC confirmed the stability of the developed system in the frequency range. The analysis of experimental data substantiated a conclusion about the influence of the angular gap on the accuracy of the elastic moment recovery in the mode of metal capture by rolls. Prospects for the introduction of developments at mill 5000 and other rolling mills operating with shock load are noted.

Twin Roll Casting of Copper Alloy C19210 Using Commercial Scale Machine

Copper alloy C19210 have excellent corrosion resistance, heat resistance, and conductivity, and is used for precision electronic parts such as lead frame materials. Conventionally, copper alloy strips are manufactured by repeating heat treatment and cold rolling, and have a problem that it is multi-process and production cost is expensive. On the other hand, twin roll casting can improve the above problems because strips are made directly from molten metals. In this study, twin roll strip casting of copper alloy C19210 using commercial scale machine was operated. The aims of this study is to investigate the possibility of strip casting for copper alloy. The effect of the side dam and release agent was researched. The effect of rolls speed on the strip surface condition was researched. The improved side dam prevented molten metal leakage. The release agent prevented sticking of the manufactured strip to the roll surface. The strip produced at roll speed of 7 m/min and 10 m/min had a lot of metallic luster. Moreover, the strip produced at roll speed of 7 m/min had more metallic luster than the strip produced at roll speed of 10 m/min. The lower the roll speed is, the greater the rolling load is. At a roll speed of 7 m / min, the rolling load became the maximum rolling load of the equipment. For producing strips with copper alloy C19210, higher rolling loads are preferred.

Uji Kinerja Roll Pengepres Dengan Beberapa Variasi Kecepatan Putaran Pada Alat Pencacah Tipe Reel Tandan Kosong Kelapa Sawit (Elaeis guineensis Jacq)

Abstrak. Penelitian ini bertujuan untuk melakukan pengujian pada alat pencacah tandan kosong kelapa sawit (Elaeis guineensis Jacq) tipe reel dengan menggunakan 3 variasi kecepatan putaran roll pengepress yaitu 40, 60, dan 80 rpm. Alat pencacah ini menggunakan system transmisi sabuk pulley, dengan menggunakan motor penggerak mesin diesel dengan daya 6,5 HP, dengan bahan tandan kosong sawit (TKS) sebanyak 3 kali pengujian untuk setiap satu pengujian kecepatan dengan berat awal setiap pengujian ±3,010 kg, dengan menggunakan roll pengepress sebelum melakukan proses pencacahan yang berfungsi untuk mencengkram dan sebagai pengumpan serta menekan tandan kosong kelapa sawit. Serta hasil pengujian yaitu hasil cacahan kehilangan hasil cacahan, dan keseragaman hasil cacahan. Dengan adanya pengujian kecepatan roll pengepress terhadap mesin pencacah ini akan berpengaruh terhadap hasil cacahan dan ukuran hasil cacahan. Hasil cacahan yang dihasilkan dengan adanya penambahan roll pengepress dan menggunakan beberapa variasi kecepatan putaran roll pengepress kemudian dilakukan pengujian keseragaman hasil dengan menggunakan ayakan yang dibagi menjadi 3 ukuran yaitu untuk hasil cacahan tandan kosong 3 cm yaitu hasil cacahan halus, 3-5 cm yaitu hasil cacahan sedang dan 5 cm yaitu hasil cacahan kasar. Ukuran hasil cacahan dipengaruhi oleh berbagai macam hal, yaitu kecepatan putaran mesin, system pengumpanan, ukuran bahan, dan mata pisau pencacah. Kemudian berbagai macam bentuk dan alur mata pisau pencacah juga dapat mempengaruhi tingkat kehalusan hasil cacahan. Pada kecepatan 40 rpm didapatkan rata-rata hasil cacahan 2.059 kg dengan rata-rata cacahan kasar 59.58%. Pada kecepatan 60 rpm didapatkan rata-rata cacahan sedang 17.46%. Pada kecepatan 80 rpm didapatkan rata-rata hasil cacahan halus 32.46%.Performance Test of Roll press At Variations Of Round Speed In The Coconut Oil Palm Blast Counter Appliance (Elaeis Guineensis Jacq)Abstract. This study aims to test the reel type oil palm empty fruit bunches (Elaeis guineensis Jacq) using 3 variations of pressing roll rotation speed, which are 40, 60, and 80 rpm. This chopper uses a belt pulley transmission system, using a diesel engine driven motor with a power of 6.5 HP, with oil palm empty fruit bunches (TKS) as much as 3 tests for each speed test with the initial weight of each test ± 3.010 kg, using roll press before carrying out the enumeration process which the purpose to grab and feed as well as to suppress oil palm empty bunches. As well as the test results which are the chopped results loss the chopped results, and the uniformity of the chopped results. By testing the pressing roll speed on the counter machine it will affect the chopped results and the size of the chopped results. The chopperd results were produced by the addition of a pressing roll and using several variations of the pressing roll rotation speed then the uniformity of the results was tested using a sieve which was divided into 3 sizes which is for the results of 3 cm empty bunches is soft chopped results, 3-5 cm is chopped results medium and 5 cm which is the result of rough chopped. The size of the chopped results is influenced by various things, which are the speed of the engine rotation, feeding system, the size of the material, and the counter blade. Then the various shapes and blades of the enumerator's blades can also affect the level of fineness of the chopped results. At a speed of 40 rpm the average chopped results of 2,059 kg was obtained with an average roughly chopped of 59.58%. At a speed of 60 rpm it was found that the average chopped results was 17.46%. At a speed of 80 rpm, 32.46% of the fine chopped results were obtained.

Numerical Simulation of the Effect of Process Parameters on Cooling Rate and Secondary Dendrite Arm Spacing in High-Speed Twin Roll Strip Casting of Al–15 wt % Cu Alloy

Twin roll casting is a process used to produce thin strips of metals by continuously pouring melt on to rotating rolls. In order to make the process more productive and economical, high roll speed is recommended. The numerical simulation of high-speed twin roll casting is performed by analyzing fluid flow, heat transfer, and solidification behavior of Al–Cu hypo-eutectic alloy. The flow field, temperature, liquid fraction distribution, and cooling rate are analyzed by solving governing transport equations of continuity, momentum, energy, and turbulence. The low-Re Turbulence model is used to capture turbulence effects in the process and enthalpy-porosity technique used to account for the rise in viscosity due to phase change. The effect of melt pool height and roll velocity on average cooling rate along the strip surface is investigated. It is found that the increase in melt pool height and roll speed increases the average cooling rate along strip surface due to rise in heat transfer up to certain roll velocity but beyond that process fails due to breakout. The average cooling rate of process affects the microstructure and properties of strips. It is found that higher cooling rates result in a decrement of secondary dendrite arm spacing (SDAS) of 1 mm thin strip along strip surface results in the fine and homogeneous microstructure.