Role In Lubrication Research Articles

Hydrodynamic analysis of partial film lubrication in the cold rolling process

Lubrication in cold rolling plays an important part for process feasibility and process quality. The hydrodynamic process of lubrication is very complicated and affected by many material and process parameters. This paper examined partial lubrication in the cold rolling process. The average flow Reynolds equation for rolling lubrication was 2set, which considered the pressure–viscosity and average flow effects. Lubricating factors such as sidling, surface waviness, lubricant viscosity, surface roughness, and reduction ratio were investigated. The results of the lubrication equation show that sliding, lubricant viscosity, and surfaces roughness affect the values of rolling friction. Surface waviness and reduction ratio also influence both rolling pressure and rolling friction.

Study on the Hydrodynamic Lubrication Behavior in Cold Rolling Process

Partial lubrication in cold rolling process has been investigated. The average flow Reynolds equation for rolling lubrication is set. This equation considers the pressure-viscosity effect and the average flow effect. Lubricating factors such as inlet velocity, surface waviness, lubricant viscosity are studied in analyses. The results for lubrication equation show that inlet velocity and lubricant viscosity have some influence on the value of rolling friction. And the results also show that surface waviness has great influence on both rolling pressure and rolling friction.

Microstructural effects in wear of hardened sintered steels produced by diffusion bonded and prealloyed powders

The influence of the microstructure on the wear behaviour of some hardened sintered steels produced with diffusion bonded powders and subjected to through hardening, carburising and sinterhardening was investigated. In dry sliding, wear was oxidative in nature and the localised surface deformation caused delamination, which further reduce the wear resistance. In these conditions, the harder the microstructure, the better the resistance to plastic strain. In lubricated rolling–sliding, wear occurs by rolling contact fatigue. Cracks nucleation was caused by the stress localisation at the pores edges. In this case, a brittle virgin martensite has a negative effect. Tempering reduces martensite brittleness, and makes its resistance to nucleation and propagation of the rolling contact fatigue comparable to that of Fe–Ni austenite.

Simulation of contact friction in the hot rolling of steel sheet

Hot rolling creates complex deformation conditions at contact between the quenched strip and the working rollers and radically changes the boundary friction, which complicates simulation of this process. On the basis of many years’ experience with experimental lubricants in the hot rolling of steel strip in laboratory and industrial conditions, data regarding the influence of lubricant on the rolling parameters and the surface quality of the strip, and observations of the working surface of rollers in different periods, we derive conclusions regarding the formation of a lubricant contact layer at the rollers in accordance with the molecular-physics theory of contact friction and corrections to the theory. The process may be divided into three periods. First, in the brief period of mill operation without a load, a boundary layer of active lubricant is formed at the roller surface, in accordance with the molecularphysics theory of boundary friction [1]. In the absence of an external load, the thickness of the lubricant layer formed is half of the boundary phase determined by the force field of the solid roller surface, the temperature, and the properties of the atomic structure of the lubricant molecules. In the initial period, these factors determine the physical state of the material forming the boundary phase. When active lubricant is supplied to the rollers, a half layer of boundary phase is formed at the roller surface. In four-roller cells, if the lubricant is supplied to the working or supporting rollers, the boundary phase is transferred from one roller to another through the frictional contact between them. The thickness of the lubricant layer formed on subsequent rollers is also half the boundary phase without an external load. This transfer of the active-lubricant layers between the working and supporting rollers, confirmed in investigating the lubricants in industrial mills, permits the creation of rational methods and the design of oiling systems for thin-sheet hot rolling with lubricant, in production conditions. The second stage, which is the most prolonged, is associated with partial or complete combustion of the thin organic-lubricant layer in the deformation source. The combustion products, which have antifrictional properties, reduce the frictional contact forces. There has been virtually no study of the complex frictional mechanism in the deformation source during hot rolling. It is obvious, however, that occlusion occurs at the contact of the strip with the working rollers: specifically, the frictional forces are reduced, while the thickness, structure, and color of the scale are changed. Research shows that the working surface of the rollers is covered by a thin soot coating, which is retained throughout rolling and stabilizes the contact friction at a lower level; this determines the efficiency of the technological lubricant.

Molecular rolling friction: the cogwheel model

With the help of a two-dimensional (2D) model we study rolling lubrication by circular(‘2D fullerenes’) molecules for a wide range of parameters. The conditions under whichmicroscopic rolling friction may be effective are identified and related to the relativeingraining between substrate and molecule, the latter behaving as a nanosized cogwheel.

Rack-and-pinion effects in molecular rolling friction

Rolling lubrication with spherical molecules working as ‘nanobearings’ has failed experimentally so far, without a full understanding of the physics involved and of the reasons why. Past model simulations and common sense have shown that molecules can only roll when they are not too closely packed to jam. The same type of model simulations now shows in addition that molecular rolling friction can develop deep minima once the molecule's peripheral ‘pitch’ can match the substrate periodicity, much as ordinary cogwheels do in a rack-and-pinion system. When the pinion-rack matching is bad, the driven molecular rolling becomes discontinuous and noisy, whence energy is dissipated and friction is large. This suggests experiments to be conducted by varying the rack-and-pinion matching. That could be pursued not only by changing molecules and substrates, but also by applying different sliding directions within the same system, or by applying pressure, to change the effective matching.

The Shear-Thinning Elastohydrodynamic Film Thickness of a Two-Component Mixture

Lubricant base oils are often blends of different molecular weight cuts to arrive at a specified ambient pressure viscosity and, to improve the temperature-viscosity behavior or to simply increase the viscosity, viscosity-modifying polymer additives are often added to the base oil. This paper investigates the effect of mixture rheology on elastohydrodynamic lubrication (EHL) film thickness using EHL contact measurements and a full numerical analysis for three synthetic lubricants including two single-component lubricants PAO650 and PAO100 and a mixture of these. The pressure and shear dependences of the viscosity of these lubricants were measured with high-pressure viscometers; viscosities were not adjusted to fit experiment. The point contact film thicknesses for these lubricants in pure rolling were measured using a thin-film colorimetric interferometry apparatus. Numerical simulations based on the measured rheology show very good agreement with the measurements of film thickness while the Newtonian prediction is up to twice the measurement. These results validate the use of realistic shear-thinning and pressure-viscosity models, which originate from viscosity measurements. It is conceivable that simulation may provide a means to “engineer” lubricants with the optimum balance of film thickness and friction through intelligent mixing of components.

EFFECT OF STARVATION ON THERMOELASTOHYDRODYNAMIC LUBRICATION OF ROLLING / SLIDING CONTACT

A complete numerical solution of thermal compressible elastohydrodynamic lubrication of rolling /sliding contact was achieved to determine the effect of inlet boundary condition on the film shape,film pressure, and film temperature in an elastohydrodynamic line contact problem.The direct iterative technique is used to solve the simultaneous system of Reynolds, ,elasticity , andenergy equations for different locations of inlet oil fed . The effect of various load, speed , and slipconditions have been investigated . the results indicate that the effects of starvation are an increaseof oil film temperature and decrease in oil film thickness so that the temperature effect aresignificant and can not be neglected.

Origins of the friction and wear properties of antiwear additives

Experimental techniques have been developed to measure the friction, antiwear film-forming and wear properties of lubricants in rolling–sliding contact. Friction measurements show that zinc dialkyldithiophosphates (ZDDPs) and also some other phosphorus-based additives increase friction in mixed lubrication. Film thickness measurements show that this increase in friction correlates with the thickness of antiwear film. They also reveal some of the drivers of antiwear film formation and removal. A novel wear tester is described which enables the mild wear resulting from ZDDP-containing oils to be monitored. Copyright © 2006 John Wiley & Sons, Ltd.

Quaker Chemical Corp.

AbstractPetroleum and Coal Products (MIC: 11.8 SIC: 2992 NAIC:324191)Quaker Chemical develops, produces, and markets a wide range of formulated chemical specialty products for various heavy industrial and manufacturing applications and, in addition, offers and markets chemical management services. Co. operates in three segments: metalworking process chemicals, coatings, and other chemical products. Co.'s principal product lines include rolling lubricants, corrosion preventives, hydraulic fluids, machining and grinding compounds, forming compounds, chemical milling maskants, metal finishing compounds, technology for the removal of hydrogen sulfides, construction products and programs to provide chemical management services.

The effect of surface deformation on lubrication and oxide-scale fracture in cold metal rolling

Finite-element analysis is used to examine the surface deformation of a thin strip at the inlet to the bite in cold metal rolling. There is a “pre-entry” region ahead of the bite where there is significant elastic deformation of the strip and a very short transition region at the elastic-plastic boundary (which is not accurately modeled in this analysis). A suitable normalization allows the shape of the inlet profile and the surface extension of the strip ahead of the bite in the pre-entry region to be represented by a single master curve. The effect of strip deformation ahead of the bite on inlet lubrication and surface oxide fracture in aluminum rolling is investigated.

Finite element modelling of mixed film lubrication in cold strip rolling

A finite element model for mixed film lubrication in cold strip rolling has been developed. In this paper, a full 3D rigid–plastic finite element method (FEM) was used to simulate the cold strip rolling, taking into account the friction variation in the roll bite which involves a mixed film lubrication regime. A roll with embedded pins was employed to measure the variation of the coefficient of friction. The simulation results such as rolling force and torque have been validated by experimental results, which indicate that the developed model can give a reliable prediction. This paper contributes to Professor Wang’s 70th birthday celebration. The first author has been significantly inspired by Professor Z.R. Wang’s distinguished work in metal forming since he was an undergraduate at the Northeastern University, PR China, which has benefited him significantly in the development of his academic career.

Quaker Chemical Corp.

AbstractPetroleum and Coal Products (MIC: 11.8 SIC: 2992 NAIC:324191)Quaker Chemical develops, produces, and markets a wide range of formulated chemical specialty products for various heavy industrial and manufacturing applications and, in addition, offers and markets chemical management services. Co. operates in three segments: metalworking process chemicals, coatings, and other chemical products. Co.'s principal product lines include rolling lubricants, corrosion preventives, hydraulic fluids, machining and grinding compounds, forming compounds, chemical milling maskants, metal finishing compounds, technology for the removal of hydrogen sulfides, construction products and programs to provide chemical management services.

The rolling of very high strength steels on the Sollac Lorraine HSM

In order to roll thin and wide material of very high strength grades on our low powered mill, a global optimization of the process has been done. Taking account of the finisher power limit and furnace maximum drop out temperature, improvements have been made on the thickness of the transfer bar regarding the load of the prefinishing stand, on the finisher speed schedule and preset, on the use of the cooling system and on work roll lubrication.

Thermal effect on the film thickness in high-speed lubricated cold rolling of a strip—an inlet zone analysis

A thermal analysis of hydrodynamic lubrication of high-speed cold rolling of strips in the inlet zone has been made to estimate the film thickness in the contact region. The piezoviscous effect, which would be significant in the case of heavy-duty rolling when a large reduction in the thickness of the strip takes place during the rolling process, has been incorporated using Roelands' viscosity model. The generalized Reynolds equation in the inlet zone has been solved using the finite difference method to determine the pressure distribution. Temperature variations across the film have been expressed using Legendre's polynomial at Lobatto points while solving the energy equation. Temperature variations along the film were determined using the finite difference method by solving the energy equation. The results for the film thickness-temperature profile in the inlet zone have been estimated for high-speed rolling of the strip (up to 50m/s) with and without sliding for heavy reduction in thickness of the strip. Significant reduction in the film thickness due to the thermal effect has been found.

A 3D finite element analysis of the hot rolling of strip with lubrication

In both rolling theory and practice, two important factors must be considered: friction and deformation resistance strength. A major handicap to producing accurate and reliable models for hot strip rolling is the lack of well-defined friction boundary conditions. In order to improve the accuracy of the computer on-line control model, in this paper, the authors developed a 3D rigid–visco-plastic finite element method (FEM) model to simulate the hot rolling of strip, considering dry and lubricated conditions. The simulation was based on the experimental conditions conducted on a Hille 100 experimental mill. Rolling pressure was measured by a sensor roll that includes a radial pin and an oblique pin. A comparison of the simulation results and experimental values, such as roll separating force and torque, taking into account the friction variation in the roll bite shows a good agreement. The application of lubrication in hot strip rolling can reduce the roll separating force, and the rolling speed also has a significant influence on the roll separating force.

Nano-Meter Film Rheology and Asperity Lubrication

It is today possible to manufacture so smooth surfaces that they can elastically conform totally to each other over the whole Hertzian contact area. For pure rolling lubrication such surfaces only need an oil film of molecular dimensions to get total separation. When the rolling motion is combined with sliding, the pressure fluctuations inside the Hertzian contact redistribute the oil and make metal-to-metal contact possible. The redistribution velocity is a function of the slip rate S and the number of asperities N from the inlet to the outlet of the Hertzian contact area. The asperity top oil film thickness decreases with a factor of the order 2NS going from the inlet to the outlet of the Hertzian contact.

Experimental study of deep drawability of hot rolled IF steel

The effects of the hot rolling conditions on the deep drawability of hot rolled interstitial-free (IF) steel were investigated in this paper. Experiments showed that the rolling lubrication affected the deep drawability of the hot rolled IF steel greatly. Without rolling lubrication, the hot rolled IF steel could not obtain deep drawability. Pass reduction also had a significant effect on the deep drawability. Large pass reduction could increase the average plastic strain ratio of the hot rolled IF steel sheets. When rolling in ferrite region, lowering the hot rolling temperature could improve the deep drawability. The textures in the hot rolled IF steel sheets were analyzed by X-ray diffraction. The effects of rolling lubrication and annealing on the microstructure and textures in the hot rolled IF steel were discussed.

EXTENDING THE LONGEVITY OF ROLLING CUTTER BITS

Analysis of failures in oil and gas equipment indicates that the rolling cutter is the weak link in drill bits. One of the causes of rolling-cutter breakdown is contortion of the balls and roller of the thrust bearings of the bit, which leads to a cle ft in the rolling cutter. A design of rolling-cutter bit, which possesses extended longevity, has been developed at the Sarapul Polytechnic Institute (branch of the Izhevsk State Technical University). Lack of circulation of metal-blocking lubrication in the zone of contact between the hemispherical surfaces of the rolling cutter and shank is a deficiency of present devices. Figure 1 shows a rolling cutter bit with shank 1 and journal 5, the surface of which is built in the form of a hemisphere. Rolling cutter 8 is mounted on the shank using articulated rolling bearing 3. Channels 4 for the feed of lubricant through knurls 9 onto the spherical surface of the journal of reservoir 7 are located in the journal. A layer of copper film 6 is situated between the mating surfaces of the hemispheres of the rolling cutter and journal, and labyrinth seal 2 is installed between the shank and rolling cutter. Rotation from the drill rig is transmitted to the shank and rolling cutter via the housin g of the drill bit. As the rolling cutter turns about its own axis, friction develops between the contact surfaces of the hemisphe res of the rolling cutter and shank, as a result of which the layer of copper film applied to the surface of the hemispheres of the rolling cutter (or shank) is heated. A lubricant (2/3 of glycerin and 1/3 of a hydrochloric acid solution) is fed into the cont act zone through channels 4 and knurls 9. A pressure is created in the lubricant fluid in the contact zone by centrifugal forces, and channels 4 are evacuated, promoting the entry of lubricant from the contact zone to reservoir 7. When there is a difference in surface potentials between the copper alloy (+) and iron alloy (‐), copper particles proceed onto the journal (or rolling cutter), the uncompensated surface structure of the iron alloy (the potential of which increas es with increasing temperature in the contact zone), is attained, and the components existing in the iron alloy proceed into the contact zone, thereafter settling in the knurls. A thin (atomic) layer of copper film, which additionally plays the role of lubri cant, is formed between the contact surfaces. A uniform layer of copper film over the entire contact surface ensures high contact stiffness. The mating surfaces of the cutting roller and journal are fabricated with a high accuracy on machines manufactured with the aid of a computer; this makes it possible to apply a thin layer (0.01‐0.02 mm) of copper (or its alloy); during assembly, moreover, a fabrication error is compensated (if a thin layer of copper is applied) due to rotation of the rolling cutter around its own axis and the axis of the journal (a superfluous layer of copper settles in the knurls of the journal, and thereafter proceeds into the recesses of the rolling-cutter cleft of the articulated rolling bearing, compensating for the clearance in the latter). Thus, the fabrication and assembly of the rolling cutter and journal is simplified many times over, the productivity and accuracy of fabrication is improved, and the longevity of the bit is extended. In the design, use of a simplified labyrinth seal between the rolling cutter and shank (SV-synthesis coating) appreciably reduces the ingress of soil to the contact zone; this also extends the longevity of the bit.

Numerical Simulation of Friction Coefficient and Surface Roughness in Cold Rolling of Steel Sheets.

In order to make the numerical analysis model for friction coefficient and surface roughness of a rolled material in cold rolling, the experimental equations for the unknown parameters in the model of cold rolling lubrication are obtained from the analyses of experimental results for characteristics of boundary lubrication and surface roughness in cold rolling of steel sheets which were reported formerly. Also, applying these experimental equations to the model of cold rolling lubrication gives the numerical analysis model for friction coefficient and surface roughness of a rolled material. Then, the values calculated by the numerical analysis model are compared with the ones measured by the cold rolling experiments. Moreover, the effects of surface roughnesses of roll and an initial material on friction coefficients and surface roughnesses of the rolled material in cold rolling are analyzed by the numerical analysis model. As a result, the lubrication mechanism in the cold rolling experiments reported formerly has been discussed and clarified.