High-speed Rolling Research Articles

Effect of Roll Material on Strip Solidification between the Rolls of a Vertical-Type High-Speed Twin-Roll Caster

Tool steel for hot working is usually used for the rolls of conventional twin-roll casters for aluminum alloys. In a vertical high-speed twin-roll caster, copper rolls are used to rapidly solidify the aluminum alloys and to increase the casting speed, since the thermal conductivity of copper is higher than that of tool steel. However, the degree of superiority of copper rolls over steel rolls is not clear. In the present study, the effect of the roll material on strip solidification between the rolls of a vertical high-speed twin-roll caster was investigated by inserting a thermocouple in the strip during casting. The Al-4.8%Mg alloy was used, since it does not stick to the steel rolls in the absence of a parting material. Both copper rolls and mild steel rolls were used. The cooling rate, the supercooling of the liquidus temperature, and the temperature of the strip cast using the copper rolls were superior to those of that cast using the mild steel rolls. The copper rolls were better than the steel rolls in terms of achieving high-speed roll casting, rapid solidification of the strip, and high productivity.

Braking forces of a traction linear induction motor with an adjustable resistance of a short-circuite winding of the secondary element

Background: The study of the properties of linear traction drives for new types of rolling stock seems to be an urgent task. Linear motors are multifunctional and are capable of providing both traction and braking of promising high-speed rolling stock.
 Aim: Investigation of the braking characteristics of an adjustable traction linear induction motor with variable resistance by a short-circuited winding of the secondary element.
 Methods: Analytical methods have been used to obtain relations for calculating the braking forces of an adjustable linear induction motor with a short-circuited winding of the secondary element.
 Results: The obtained ratios made it possible to calculate the braking forces of linear induction motors.
 Conclusion: The results of calculating the braking forces of adjustable linear induction motors make it possible to reasonably choose the braking modes of a new type of rolling stock.

A high-accuracy SINS attitude update algorithm based on Legendre polynomial

The large-acceleration motion of HFV (hypersonic flight vehicle), the high-speed rolling of spinning missile, and the large-maneuver flight of fighter aircraft has put forward higher performance demand for SINS (strapdown inertial navigation system). The high-accuracy positing will be realized under the high-dynamic maneuver environment after decreasing measurement error of IMU (inertial measurement unit), meanwhile the algorithm of SINS must be improved. The conventional algorithm calculates the flight attitude with determining the compensation term of coning error, after ignoring the high-order term of the Bortz equation. To improve the algorithm accuracy of SINS under high-dynamic maneuver environment, a high-accuracy algorithm, which uses Legendre polynomial to complete angular velocity function approximation and takes the numerical method of quaternion differential equation as core, is proposed herein. The high-order coning error is compensated in the numerical solving period in the proposed novel algorithm, because no approximation exists in deducing process. The attitude calculating simulations are finished in coning motion condition and high-dynamic maneuver condition respectively. Compared with the quadruple-cross-product compensation algorithm which has the highest accuracy at present, the attitude error of proposed algorithm is less than its 1/3 in coning motion condition. And algorithm accuracy is raised an order of magnitude under the high-dynamic maneuver environment. The high-accuracy algorithm based on Legendre polynomial has reference significance for accurate positing of future HFV, atomic gyroscope INS research and high-accuracy algorithm design of SINS.

Effect of Al addition and annealing on the microstructure evolution of Mg-3Sn Mg alloy subjected to high-speed rolling

The microstructure evolution of Mg-3Sn, Mg-3Sn-3Al-Zn (ATZ331), and Mg-3Sn-6Al-Zn (ATZ631) alloys during high-speed rolling (HSR) and annealing was studied. High-speed rolling was carried out on the three alloys at a rolling speed of 1100 m/min, a rolling temperature of 400 °C, and a reduction of 40% during a single pass. The results showed that the microstructure of the samples after HSR contained many twins and was dominated by {10−12} extension twins (ETs) and supplemented by {10−11} contraction twins (CTs) and {10−11}-{10−12} double twins (DTs). After adding Al, the content of these different types of twins was reduced. The twinning fraction decreased significantly with 3 wt% Al addition, while the twinning fraction decreased slightly with 6 wt% Al addition. The high-speed rolled alloys were annealed at 370 °C for 1 min, 2 min, 3 min, 5 min, and 8 min. When the annealing time was 1 min, the recrystallization fraction of the ATZ631 alloy was low, indicating that increasing the Al content to 6 wt% inhibited recrystallization. When the annealing time increased to 3 min, the recrystallized grains in the ATZ631 alloy grew, indicating that the grain growth progressed faster in this alloy. When the annealing time was 8 min, the grain size of the three alloys grew. The electron backscattered diffraction (EBSD) results of the alloy annealed for 8 min showed that the twin fraction in the annealed state was lower than that after high-speed rolling. In addition with the increase in Al content, the twin fraction decreased. During high-speed rolling, the maximum intensity also increased with an increase in Al content, were 22.72, 25.09, and 26.35, and the texture of the annealed alloy was weakened. The Al addition also increased the maximum intensity.

An extra long stringless pendulum

A 2.7 m long stringless pendulum was set up to measure the coefficient of rolling friction of various balls, at higher rolling speeds than usually observed with a short stringless pendulum. The arrangement is easy to set up and makes an impressive classroom demonstration as well as an interesting laboratory experiment.

Сложная пространственная геометрия криволинейных участков трассы высокоскоростных железнодорожных магистралей

Purpose: The paper poses some promising trends of modern projection science development for high-speed railway plan and profile. The main objective of the trends is to critically rethink the provisions of the existing regulatory design base of the projection. The question on inadmissibility of the arrangement of complex spatial geometry sections — the sections of coincidence of a vertical curve in a profile and a passage curve in a plan — is one of such provisions. Methods: In the frames of the conducted research, a theoretical approach to the determination of force impacts at the section of complex spatial geometry is proposed. Results: It is established that force impact value is caused by vertical curve direction (convex or concave), as well as by calculated value of outstanding acceleration in being considered curve, Studies of the influence of sections with complex spatial geometry on the dynamics of high-speed rolling stock motion show that at certain combination of circular and vertical curve radii for motion various speeds, it is possible to minimize negative dynamic effects caused by the presence of complex spatial geometry section. Practical importance: As a result of the work, it was found that at speeds of 350 km/h or more, the superimposition of a vertical curve in the profile and a passage curve in the plan is acceptable without applying additional requirements to the curve parameters. The radius of the circular curve should be increased by 30-60% at speeds of less than 350 km/h.

Оптимизация эксплуатационных расходов за счет улучшения условий взаимодействия подвижного состава и пути по параметру эквивалентной конусности

Purpose: Calculation of an economic effect by introducing the parameter of equivalent taper of wheel pairs on account of reduction of operating costs on high-speed train motion and track facility maintenance. Methods: The study used the methods of computer simulation of interaction between a rolling stock and a railway track, methods of mathematical statistics, methodology to make traction calculations in automated system. Results: Measures have been proposed to reduce the forces of a drag for a high-speed rolling stock motion. We’ve calculated an economic effect from introduction of wheel pair equivalent taper parameter on Russian Federation high-speed railroads. Practical importance: Recommendations have been proposed on consideration of wheel pair equivalent taper parameter for to reduce the forces of drag to the motion and on pursuing rail mobile treatment on the sections of high-speed train traffic sections.

MODEL OF ROLLING RODS IN THE ROLL PASS OF THE OVAL-ROUND

For modern high-speed rolling mills, stable and efficient operation is possible only with the use of automatic process control systems. Such systems involve the use of certain process models, both for control and technology development. Therefore, research aimed at improving existing models of the process of rolling rods and developing new ones remains relevant.
 The aim is to improve the model of the process of rolling rods of round cross-section using a system of passes "oval-round", suitable for the development of technology (determining the size of pass and power parameters) and as software for automatic process control systems.
 A characteristic difference of the proposed improved model is the application of the condition of volume constancy to determine not only the speed but also the deformation parameters of rolling. Features of the model also include the appointment of the ratio of the axes of oval passes and the use of the rate of mismatch in the interstand spaces to control and minimize tension.The sequence of calculations in the model includes an iterative procedure with three mandatory approximations, which involves adjusting the coefficients of elongation using the condition of constant volume, and adjusting the size of the workpieces using speed mismatch as a factor characterizing the corresponding tension or compressive.
 The model uses known expression and geometric relationships, the combination and sequence of which provides the definition of technological parameters and sizes of roll passes with the required accuracy. The program can be implemented in various forms depending on the needs, from the most common applications to environments of professional computer systems. The model can be used as a basis for the development of systems for automatic control of the rolling process for the conditions of the existing mills.

ANALYSIS OF PARAMETERS AND MODELING OF WEAR ROLLS OF HIGH-SPEED WIRE BLOCKS

Research on the study of features and modeling of wear of rolls remains relevant, due to the need to predict the stability of rolls and determine their costs. The importance of such research increases with the introduction of new roll materials, in particular tungsten carbide alloys.
 The processes of hot rolling are characterized by the simultaneous action of several main mechanisms of wear. Various models for predicting wear are known for these mechanisms, but under current conditions there is a need to develop local models that take into account the peculiarities of technology. Such conditions include high-speed wire blocks.
 The aim of this work is to analyze the parameters of high-speed rolling according to the level of their impact on the wear of the rolls and to develop a model of wear of the rolls of the unit based on the actual wear of several sets of rolls. For the analysis the results of measurements of wear of four sets of rolls which were executed by an optical method and calculated parameters of rolling on usual technology are used. Correlation analysis was performed, using the indicator of wear intensity, as the ratio of maximum wear to the amount of rolled metal in the caliber. A linear dependence was chosen to build the regression model.
 According to the results of the analysis of the wear rate and rolling parameters in the high-speed wire block, it is established that the well-known tribological rolling parameters vary according to the block modules in a rather narrow range, which does not reveal their effect on wear. That is, the effect of these parameters is approximately the same for all modules of the unit, so it is not statistically confirmed.
 The correlation analysis revealed the most significant parameters of rolling by the effect on the wear rate, namely the relative velocity of the cell, the elongation coefficient and the cell shape parameter. For these parameters, a regression model was obtained to determine the wear rate. The model confirms the adequacy and provides an acceptable level of accuracy in determining the wear of the rolls of the block.
 The obtained regression model can be used to determine the durability grooves rolls of the block and predict the expense of rolls, as well as to adjust the technological parameters to reduce wear and expense of rolls.

Tribological Characteristics of Nano-Lubricated High-Speed Rolling Bearings Considering Interaction between Nanoparticles and Rough Surface

The embedding situation between various nanoparticles and rough surfaces affects the lubrication characteristics of rolling bearings. If not properly handled, this can easily lead to wear damage of rolling bearings. Therefore, the friction and wear mechanism of nano-lubricated high-speed rolling bearings under various nanoparticle embedded states is studied in this manuscript. Mixed oils containing different sized SiO2 nanoparticles and dispersants are prepared, and then the tribology test of nano-lubricated high-speed rolling bearings considering the interaction between various nanoparticles and the rough surfaces is conducted. The friction and wear properties such as coefficient of friction, wear volume and real-time temperature rise of high-speed rolling bearings under different embedding conditions are revealed, and the anti-wear mechanism of the nano-lubricated high-speed rolling bearings is obtained. The results show that compared to the complete non-embedded state, the complete embedded state of different nanoparticles effectively improves the anti-wear effect of the bearing. When the nanoparticle mixed oil is added, the bearing still has good anti-wear performance under the conditions of high speed and lack of oil. As for the light loaded rolling bearing adopted with nano-mixed oil, the coefficient of friction is appropriately increased, as well as the skid reduced, while the wear of the rolling bearing is effectively reduced. This research will provide theoretical basis and important reference for nano-lubrication and its application in aviation rolling bearings.

Design of a damped vibration absorber to control the resonant vibration of roll

Strip rolling is currently the main steel production process. The vertical vibration of the rolling mill caused by the large reduction ratio and high rolling speed reduces the qualification rate of strip products, and even damages the rolling equipment. In this paper, a new particle damping absorber (PDA) is designed to suppress the vertical vibration of the mill. The adaptive genetic algorithm (AGA) is used to optimize the basic parameters of PDA. Considering the nonlinear stiffness between the roll and the rolling stock, a four-degree-of-freedom vertical vibration model of the roll system with the PDA is established. The amplitude-frequency characteristic equations of the primary resonance and the internal resonance are solved by using the multi-scale method. The static bifurcation of the primary resonance of the system is investigated based on the singularity theory. The effects of parameters on vibration are analyzed. The control effect of the vibration absorber is investigated experimentally, and it is found that the experimental results are basically consistent with the theoretical analysis, which verifies the reliability of the established vibration model. The results show that the PDA can effectively suppress the vertical vibration of the roll. It provides some theoretical guidance for the research on vibration suppression of rolling mills.

Thermal shock of subsurface material with plastic flow during scuffing

The thermal shock of subsurface material with shear instability and severe plastic flow during scuffing was investigated. The scuffing damage of M50 steel was tested using a high-speed rolling—sliding contact test rig, and the transient temperature during scuffing was calculated using the Fourier transform method considering the effects of both frictional heat and plastic work. The results show that a thermal shock with a rapid rise and subsequent rapid decrease in the contact temperature is generated in the subsurface layers. The frictional power intensity generates a high temperature rise, leading to the austenitization of the subsurface material. Consequently, the plastic flow is generated in the subsurface layer under the high shear stress, and the resulting plastic strain energy generates a further temperature increase. Subsequently, a rapid decrease in the contact temperature quenches the material, resulting in clear shear slip bands and retained austenite in the subsurface layers of the M50 steel.

Investigation of Oil–Air Flow and Temperature for High-Speed Ball Bearings by Combining Nonlinear Dynamic and Computational Fluid Dynamics Models

Abstract An improved nonlinear dynamic model of high-speed ball bearings with elastohydrodynamic lubrication is adopted to predict the movements of balls and power loss of ball bearings for defining the boundary conditions of a computational fluid dynamics (CFD) model. Then, this method of combining nonlinear dynamic and CFD models is validated through the experimental verification. Subsequently, oil–air flow and temperature distribution inside the bearing chamber are studied at low and high speeds and light and heavy loads. The effect of nozzle’s position on the formation of oil film and heat dissipation is revealed under combined loads. The research results provide a theoretical basis for engineering application of high-speed rolling bearings.

Metal flowing mechanism of high-speed cold roll beating of spline

Metal flowing mechanism of high-speed cold roll beating of spline

Polygonal wear mechanism of high-speed wheels based on full-size wheel-rail roller test rig

The polygonal wear of train wheels is common. It increases the wheel-rail interaction force drastically and adversely affects the safety and comfort of the train. The mechanism of the initiation and development of polygonal wear warrants further study. This study performed a high-speed rolling test based on the full-size wheel-rail roller test rig to reproduce the entire process of the generation and development of the polygonal wear on the tested wheelset of CL60 steel in the laboratory. The mechanism of the initiation and development of polygonal wear was analyzed using the test results, the bending resonance of wheelset was considered as an important cause of the polygonal wear in this paper. The basic condition for the polygonal wear formation and its high rate of development was verified. The evolution process of polygonal wear was studied in-depth, and the relationship between axle-box acceleration and polygonal wear was revealed. Effective countermeasures against the development of polygonal wear were proposed. Variable speed operation could mitigate the development of polygonal wear in this paper. The results obtained in this study may provide reference for the further study of the effective countermeasures against the development of polygonal wear.

Life enhancement of bent pipe by heat treatment

Wire rod mill is continuous high speed rolling mill to produced wire rods of varying diameters from billets. Bent pipe is a thick-walled hollow pipe located in between the pinch roll and laying head of the wire rod mill, which feeds wire rod from mill to the laying head. The pipe is not straight and the bending of the pipe is designed in such a manner so that it can accommodate the height difference between the pinch roll and the laying head in the WRM.Bent pipe absorbs lot of mechanical shock due to its shape and it absorbs thermal shock as finish rolling temperature is around 1000 °C. Thus, significant abrasive wear of bent pipe takes place during operation as a result it punctures almost regularly after around 1200 T of rolling. This kind of failure of bent pipe is predominant in lower section plain wire rods which are rolled at relatively higher speed. The puncture of bent pipe during rolling leads to cobble and production losses.The failed bent pipe was investigated by metallurgical investigations. JMat pro software was used to determine the CCT diagram from where the maximum hardness of material was determined. Heat treatment experiments were performed in laboratory to optimize the heat treatment parameters. After proper heat treatment, life of bent pipe was improved by using the existing material by 150%. This was validated by plant trials.

Data Augmentation and Characterization of Nonlinear Vibration Responses of High-Speed Rolling Bearing

Data Augmentation and Characterization of Nonlinear Vibration Responses of High-Speed Rolling Bearing

In situ observation of the interface between a roll and a sheet in flat rolling process

In metal forming processes, the interface between a workpiece and a tool was occasionally observed directly. However, the rolling interface has almost never been observed because of high-speed roll rotation. To achieve the in situ observation, this paper proposes a novel method where one roll is fixed in the space without rotation, while the other roll revolves around the fixed roll with rotation. With passing the gap between the two rolls, a sheet is rolled. A prototype machine with transparent rolls was fabricated, then the interface in solder rolling was successfully observed from the interior of the fixed roll.

ВЗАИМОДЕЙСТВИЕ ТОКОПРИЕМНИКА ВЫСОКОСКОРОСТНОГО ПОДВИЖНОГО СОСТАВА И КОНТАКТНОЙ ПОДВЕСКИ В РАЗЛИЧНЫХ УСЛОВИЯХ ЭКСПЛУАТАЦИИ

The paper presents a mathematical model that describes interaction of a current collector of high-speed rolling stock and catenary suspension in various conditions of operation such as rolling stock speed, current collector opening height, wear rate of current collection plates, ambient temperature, wind and glaze. The authors have determined limits of permissible operation according to quality of current collection, have established parameters of climatic and technogenic factors at which it is necessary to restrict speed on high-speed lines according to conditions of current collection. Results of the study can be used at development and production of domestic high-speed current collectors and catenary suspensions and at adaptation of import models for operation in Russia.

NEW BEARING STEEL FOR HIGH-SPEED APPLICATIONS

The requirements for speed suitability and fatigue strength of motor spindle bearings are constantly increasing. These challenges can be met by further developing the spindle bearings, e.g. by using higher-performance bearing steels. In the following, the experimental investigation results of a spindle bearing made of a new raceway steel tested on a high-speed rolling bearing test rig are presented. Spindle bearings of the type 7008 (hybrid execution) were tested in an endurance run at a rotational speed of 46 krpm and 3 kN axial load. The operating behaviour was validated based on the bearing outer ring temperature and the vibration behaviour. Microscope analysis of the raceways after the test shows that the new steel has good resistance to micropitting and surface fatigue. The calculated contact pressures, wear parameter and lifetime for the bearings in the tests show that the performance limits of spindle bearings are significantly higher than initially assumed.