Effect Of Rolling Speed Research Articles

Effect of Rolling Speed on Microstructure of Al-33wt. % Cu Alloy Strip Prepared by Twin Roll Strip Casting

Microstructural evolutions of Al-33wt. % Cu alloy strip, prepared by twin roll strip casting (TRC) at different roll speed (100-500 rpm) were studied in the present investigation. The as cast sample were subjected to Scanning Electron Microscope (SEM) to study the effect of rolling speed on microstructure along the thickness of the strip. The microstructure shows that Al-33 wt. % Cu strip is a layered structure which consists of partly lamellar and wavy structure. The lamellar microstructure consists of alternating layers of well bonded α-Al phase and θ-Al2Cu phase.

Effect of Rolling Speed on Instantaneous Temperature Distribution and Thermal Expansion of Work Roll in Hot Strip Rolling

In the unsteady state, work roll temperature distribution and thermal expansion have an enormous effect on the process of hot rolling. The rolling speed in the finish rolling as an important rolling parameter plays a crucial role of obtaining the optimum temperature distribution and thermal expansion. Using the finite element method, it solves the regularity of temperature distribution and thermal expansion with thermal-structural coupling analysis, which provide theoretic proof of optimizing gauge and profile control.

Ti STRIP PROPERTIES FABRICATED BY POWDER ROLLING METHOD

In the present study, the characteristics of the Ti powders fabricated by Hydride–Dehydride (HDH) were analyzed in terms of particle shape, size and size distribution. Ti powders were subjected to roll compaction and their microstructure and green densities were evaluated in terms of particle size, powder morphology, roll gap and rolling speed. Effects of blending elements having different powder sizes on densification properties were analyzed. The strip thickness was proportional to the roll gap up to 0.9 mm and the density of titanium strip was decreased with the increase in roll gap. As the roll speed increased, the strip density and thickness were decreased by using -200 mesh Ti powder. However, the effect of rolling speed for -400 mesh Ti powder was not greater than that of -200 mesh powder. The highest density by 93% was achieved by using -400 mesh Ti powder at 0.1 mm roll gap, however edge cracks and alligator cracks were occurred.

Effect of rolling speed on the occurrence of strain aging during and after warm rolling of a low-carbon steel

In this study, effect of rolling speed on strain aging phenomena in warm rolling of a carbon steel has been investigated. For this purpose, by using a mathematical model and predicting temperature and strain rate fields, the possibility of occurrence of dynamic strain aging during the warm rolling was first evaluated. In the next stage, warm-rolled samples were aged up to 11 months at room temperature for studying the kinetics of static strain aging, while mechanical tests as well as microstructural evolutions have been performed to determine the effect of strain aging on material behavior. The results indicate that dynamic strain aging may not occur for the employed rolling program; however, static strain aging takes place after warm rolling leading to changes in the mechanical behavior of the warm-deformed samples. In addition, by increasing rolling speed, the aging time required to achieve the maximum hardness increases.

Effect of Rolling Speed on Deformability and Microstructure in Rolling of AZ31B Magnesium Alloy

Magnesium alloys are expected to be used widely as structural materials because of their lowest density (1.8g/cm3) among all practical alloys and superior specific strength. However, magnesium alloys exhibit poor ductility due to its hcp structure and inactiveness of non-basal slip systems below 523K. Accordingly, magnesium alloy sheets had to be rolled at elevated temperature to avoid edge cracking and fracture during rolling. The present authors succeeded in single pass large draught rolling of AZ31 magnesium alloy sheets below 473K without heating rolls by rolling at the speed higher than 1000m/min. The rolled and quenched sheets had fine recrystallized microstructure and exhibited excellent mechanical properties. It was found that the high speed rolling is a promising method not only for increasing productivity but also for controlling microstructures and improving mechanical properties. If the above mentioned advantages of high speed rolling can be drawn from the rolling at the speed lower than 1000m/min, it is possible to mass-produce magnesium alloy sheets having superior mechanical properties at lower cost. In this study, we tried to determine the lower limiting rolling speed at which we can obtain advantages of high speed rolling. We revealed that the thickness could be reduced about 60% by single pass operation even at 250m/min without heating rolls. The rolled and quenched sheets had equiaxed fine recrystallized microstructure. For example, the mean grain size of 2.1m was obtained in the AZ31B sheet rolled at 250m/min at room temperature to the reduction of 60%.

An efficient thermal analysis for the prediction of minimum film thickness in inlet zone at high speed lubricated cold strip rolling

The main objective of this work is to develop a formula for the prediction of thermal minimum film thickness at the roll/strip contact in terms of operating parameters particularly at the elevated roll speeds. The film thickness at the exit of inlet zone and at the entry of contact zone is common. Therefore, in order to compute minimum film thickness accurately at the contact, an efficient thermohydrodynamic analysis of fully flooded inlet zone has been carried out. The effects of rolling speed, reduction ratio, material parameter and slip on minimum film thicknesses (isothermal and thermal) and maximum film temperature rise (in the inlet zone only) are rigorously investigated. The performance parameters in the lubricated domain have been evaluated for rolling speeds (up to 20.0 m/s), reduction ratios (0.05–0.20), and slip values varying up to 20%. Significant reduction in minimum film thickness (thermal) has been observed with the increase in the rolling speed and slip. Based on this study, empirical relations are developed for the prediction of minimum film thicknesses (isothermal and thermal) at the contact. A relation for evaluation of maximum film temperature rise in the inlet zone has been also developed. Authors believe that the empirical relations presented herein may be useful for designers and practicing engineers.

Key factors for warm rolled bond of 6111-aluminium strip

Abstract Based on rolling tests and simulation, the bond behavior and its mechanism of 6111-aluminum alloy commonly used in auto industry were studied. As main factors, the effects of different heating stratagem, rolling speed and reduction on bond were tested. The effect of rolling speed on bond was produced by the synthetical result of contact time and temperature of rolling zone. Higher speed creates higher temperature of rolling zone but decreases contact time of interfaces, and bond strength decreases accordingly. The bond strength increases along with the increase of entry temperature before a turning point, after the turning point bond strength changes gently. Cold rolling is hard to get a satisfying bond result although the rolling parameters are adjusted, while warm bond reaches a higher strength that is comparable to the parent material. The analysis of surfaces separated by shear test shows that for warm bonding the rolling texture disappears on the bond area but the scratch track remain on the bond area for cold bond. There is no gap at the position of interface for well-bond sample. The results of this study are helpful to create well-bond materials for auto industry.

Analysis of adhesion under wet conditions for three-dimensional contact considering surface roughness

This paper describes a numerical model to estimate the adhesion coefficient between rail and wheel under wet conditions, by applying the partial elasto-hydrodynamic lubrication (EHL) theory at three-dimensional (3D) contact considering surface roughness. The effect of the characteristics of surface roughness on the adhesion coefficient is particularly focused on in this study. Based upon numerical solutions obtained by the 3D numerical model, the effects of rolling speed, water temperature, surface roughness amplitude (i.e., standard deviation of roughness height) and parameter of roughness orientation on asperity contact pressure, which has important influence on the adhesion coefficient, are investigated under wet conditions. Furthermore, to verify the adequacy of the 3D numerical model adapted to estimate the adhesion coefficient between rail and wheel, the numerical solutions are compared with the experimental values that were obtained by a twin-disc rolling contact machine.

Effect of roll speed on the magnetic properties of nanocomposite PrFeB magnets prepared by melt-spinning

Rapid solidified Pr x Fe 94− x B 6 alloys, with x ranging from 6 to 10 at%, were prepared by melt-spinning at several roll speeds to obtain nanocomposite PrFeB magnets with enhanced properties. Magnetic properties and grain-size measurements were performed on as-cast ribbons and were correlated to roll speed. It was found that the greatest J r enhancement occurred at roll speeds that led to grain sizes below ∼30 nm. Deviations from this optimum value, caused either by partial amorphisation or grain coarsening, greatly affected the values of J r, jH c and ( BH) max.

Effect of micro-defects on the surface brightness of cold-rolled stainless-steel strip

Cold-rolled stainless-steel strip can be produced efficiently by high-speed rolling in a cluster-type rolling mill with small-diameter work rolls, or in a tandem cold-rolling mill with large-diameter work rolls. The surface brightness of the strip is deteriorated by high-speed rolling, and the surface brightness of a strip rolled by large-diameter work rolls becomes worse than that of a strip rolled by small-diameter work rolls. In this study, the effect of micro-defects on surface brightness is examined with laboratory-scale and actual rolling mills, and the mechanisms for the occurrence of micro-pits in cold rolling are discussed. The surface brightness was affected strongly by micro-defects on the surface, the brightness being improved for decreasing surface-area ratio of the micro-defects. Micro-defects can be reduced to four types: micro-pits originating from the surface roughness of the mother sheet; oil-pits formed during cold rolling; grooves formed by inter-granular corrosion during pickling; and scratches due to the surface roughness of the rolls. The micro-pits remaining on the surface of cold-rolled sheet were affected by the diameter of the work rolls, the surface roughness of the mother sheet, and the rolling reduction. The effects of rolling speed and of the viscosity of the rolling oil were minor under the experimental conditions investigated.

The radial damping of agricultural tractor tyres

The damping coefficients of rolling agricultural tractor tyres in the radial (or vertical) direction have been measured. Six different tyres ranging in age from 1 to 16 years have been measured. Factors which most affect the apparent radial damping of the tyre are the inflation pressure, the tyre age, and the surface over which it rolls. The effects of rolling speed, load, torque, amplitude, frequency, ply rating and lug length are also discussed.

Technology advances for continuous compression milling pretreatment of lignocellulosics for enzymatic hydrolysis

The feasibility of a continuous compression milling pretreatment process for the enzymatic hydrolysis of lignocellulosics has been demonstrated. Pretreatment efficiency was improved significantly by adjustment of feedstock moisture content prior to milling and/or increasing the roll pressure on the feedstock. Optimum moisture contents for newspaper (24%). corn stover (17%), popular (12-20%) were determined. Sugar Yields of 48% were obtained from air-dried newspaper after six passes through even-pressure rolls and the specific energy input was 0.21kW h/lb. The Effect of roll speed on enzymatic hydrolysis improvement was constant over a roll speed range of from 30-110 ft/min (65 rpm). Enzymatic hydrolysis results from commercial-scale pretreatment of moist newspaper processed at 6 tons/h/ correlated well with laboratory mill data while energy consumption was 26% less.

Effect of rolling speed on the fracture of plates clad with steel 08Kh13

Effect of rolling speed on the fracture of plates clad with steel 08Kh13

Aluminium Foil Production

The increasing use of aluminium foil in packaging and other areas is outlined. The principal section on aluminium foil production contains a general description of how foil is made, then, under them ore specific headings that follow, deals with roll force and torque requirements in foil rolling, the effect of rolling speed, roll dimensions, the minimum thickness that can be rolled, friction in the roll-gap, and trends in foil rolling. The separating and annealing of converter foil are then discussed. In the section on the properties of aluminium foil, the strength and ductility offoil, surface appearance, porosity, flatness and thickness tolerances, and the suitability for conversion treatments are considered. The foil conversion processes and the properties of plain and· converted foils are then reviewed from the standpoint of packaging applications. The review concludes with remarks on the energy requirements for packaging materials.

Continuous Production of Iron Strip from Metal Powder

A continuous method of producing iron strip from powder has been developed. Iron powder directly conversed to green strip by roll compacting, and which was continuously sintered, hot rolled and cooled in hydrogen atmosphere and coiled up. The effects of various continuous powder rolling factors, such as the sintering temperature, roll speed, and hot rolling lood on the properties of hot rolled strip were investigated with Husquvarna Star electrolytic iron powder and Höganäs sponge iron powder.In general, with increasing the sintering temperature and hot rolling lood the physical and mechanical properties of iron strip by powder rolling were improved, whereas the effect of roll speed was different, depending upon the sinterability of iron powder. These properties obtained were considerably well for the powder metallurgical product, although the sintering time was short. According to the repeated hot rolling or annealing and cold rolling, the pro. perties of the iron strip were equal to those of the conventional iron strip, especially the one made from Husquvarna Star iron powder showed superior magnetic properties.