Role In Lubrication Research Articles

Analysis and Prospects of Lubrication and Friction Characteristics in Cold Strip Rolling: A Review

Lubrication and friction are the core processes in cold strip rolling, which are the key links to realizing the stable production of high‐quality strips, reflecting country advanced level in rolling technology. This review investigates the crucial properties of lubrication and friction in cold strip rolling by analyzing the mechanism, characterization methods, and influencing factors. The lubricant forms an oil film on the surface of rolls and strips based on the lubrication dynamics and tribology theory, changing the asperity contact state in the loaded roll gap, leading to changes in friction characteristics. Oil film thickness and coefficient of friction (COF) are crucial parameters for characterizing and judging the characteristics of lubrication and friction, theoretical calculations have become the core analytical method, and the study of the measurement method is still a great challenge. Parameters like rolling speed and oil viscosity affect the lubricant distribution and asperity contact in the loaded roll gap, changing the lubrication and friction state. The influence of parameters is strongly linked to the experimental or rolling environment. Prospective research trends on lubrication and friction in cold strip rolling are presented based on the status of research on lubrication and friction characterization.

Research on the service life of bearings in the gearbox of rolling mill transmission system under non-steady lubrication state

A rolling bearing plays a key role in the gearbox of the cold rolling mill transmission system. As a result, the degradation and failure of bearings can lead to unplanned shutdowns of the entire rolling mill system. Since on-site cold rolling mills work usually in non-steady lubrication rolling conditions originating form variations of multiple parameters, the uncertainty affecting bearing performance in a cold rolling mill transmission system increases, making it more difficult to assess health status and predict the remaining service life of bearings, Therefore, by establishing a coupling model describing the relationship for the rolling mill and normal /faulty gearboxes under non steady rolling conditions, quantitatively studies the influence of various rolling parameters of a rolling mill on the fatigue service life of bearings in the gearbox of the rolling mill transmission system, and verify the effectiveness of linear cumulative damage theory for bearing fatigue service life through experiments and on-site bearing vibration data. The results indicate that as the thickness of the strip steel inlet, lubricant viscosity, and rolling speed increase, or the thickness of the strip steel outlet and rolling roll radius decrease, the service life of bearings gradually decreases. As the fluctuation amplitude of various rolling parameters in the cold rolling mill increases, the service life of bearings in the gearbox of the rolling mill transmission system gradually shortens. Moreover, when the rolling parameter value or fluctuation amplitude increases to a specific values, the remaining service life of bearings will sharply decrease. Under the same rolling conditions, the service life of bearings in gearboxes with faults decreases more significantly than that in normal gearboxes.

Acquisition of molecular rolling lubrication by self-curling of graphite nanosheet at cryogenic temperature

Friction as a fundamental physical phenomenon dominates nature and human civilization, among which the achievement of molecular rolling lubrication is desired to bring another breakthrough, like the macroscale design of wheel. Herein, an edge self-curling nanodeformation phenomenon of graphite nanosheets (GNSs) at cryogenic temperature is found, which is then used to promote the formation of graphite nanorollers in friction process towards molecular rolling lubrication. The observation of parallel nanorollers at the friction interface give the experimental evidence for the occurrence of molecular rolling lubrication, and the graphite exhibits abnormal lubrication performance in vacuum with ultra-low friction and wear at macroscale. The molecular rolling lubrication mechanism is elucidated from the electronic interaction perspective. Experiments and theoretical simulations indicate that the driving force of the self-curling is the uneven atomic shrinkage induced stress, and then the shear force promotes the intact nanoroller formation, while the constraint of atomic vibration decreases the dissipation of driving stress and favors the nanoroller formation therein. It will open up a new pathway for controlling friction at microscale and nanostructural manipulation.

Micropitting performance and friction behaviour of DLC coated bearing steel surfaces : On the influence of Glycerol-based lubricants

A better understanding about the rolling contact fatigue and micropitting performance of machine component surfaces lubricated with environmentally friendly lubricants is critical to designing and further formulating new lubricants intended to be used in rolling–sliding contacts such as those found in gear and bearing applications. In this work, the frictional behaviour and rolling contact fatigue (RCF) performance of DLC, Cr/a-WC:H/a-C:H and a-C:Cr coatings under glycerol-based lubrication in rolling sliding contact conditions have been investigated. Traction maps, Stribeck curves, and fatigue plots have been generated by using a micropitting test rig (MPR). The initiation and progression of micropitting was monitored by means of white light optical interferometry and scanning electron microscopy (SEM). Results indicated that glycerol-based lubricants exhibited a significant friction reduction as the hydrodynamic effect is enhanced at higher rolling-speeds. Under boundary lubrication the friction coefficient was significantly higher compared to the values obtained with a commercial mineral-based transmission oil. Compared to uncoated steel surfaces, DLC coatings effectively reduced the volume loss and micropitting progression. Irrespective of the coating thickness, DLC showed an excellent tribological behaviour when the base lubricant favours the onset of mild-wear, over micropitting. When the lubricant formulation favoured the onset of micropitting, the coatings tended to prematurely fail due to debonding from the substrate, and local micro-spallation. The experiments demonstrated that friction reduction does not necessarily correspond with a reduction of micropitting.

High‐Temperature Wettable Water‐Based Lubricants toward Hot Rolling Lubrication

AbstractWater‐based lubricants have attractive properties compared to flammable oily lubricants but in high‐temperature environments remain a tricky challenge due to the Leidenfrost effect‐induced poor wettability once contacting sufficiently hot surfaces. Herein, a surfactant‐modified Laponite nanoclay (LNC), as a prototype water‐based lubricant with considerable lubricity, exhibits spontaneous high‐temperature wettability by which the Leidenfrost point (LFP) can be improved above ≈350 °C on crude stainless steels, increasing by ≈140°C compared to pure water. The inter‐particle attractions between LNC nanoplates increase the liquid viscosity, causing viscous force of bulk water near the substrate, allowing in situ deposition of LNC layers on the hot surface to trigger three‐phase contact line (TCL) pinning. As a basis, wettable lubricants are further optimized on their lubricity by intercalating zwitterionic surfactants between LNC nanoplates, thereby reducing friction coefficient to ≈0.1. The LNC lubricants have been demonstrated in a four‐ball tribometer to simulate hot rolling lubrication, providing insights for high‐temperature metal processing, and potential applications in mechanical engineering and the aerospace field.

Tribological Properties and Lubrication Mechanisms of Water-Based Nanolubricants Containing TiO2 Nanoparticles during Micro Rolling of Titanium Foils.

The tribological behavior of traditional oil-in-water (O/W) lubricants (1.0 wt.%) and nano-TiO2 additive lubricants (1.0-9.0 wt.%) during micro rolling of titanium foils were analyzed. In this study, the surface morphologies of titanium foils under various lubrication conditions were assessed, and the corresponding lubrication mechanisms were revealed. The tribological behavior of nano-TiO2 additive lubricants during micro rolling of titanium foils was also explored through a series of characterization methods. The utilization of nano-TiO2 additive lubricants in micro rolling reduces the surface roughness of titanium foils. Moreover, it effectively inhibits the generation of indentations and cracks during rolling processes, enhancing the surface quality of rolled specimens. Additionally, owing to the synergism of rolling, tribo-film, mending and polishing effects of the nanoparticles, both the rolling force and surface roughness were minimized by using lubricants containing 3.0 wt.% TiO2 nanoparticles. Overall, an optimal concentration (3.0 wt.%) of TiO2 nanoparticles in water-based nanolubricants was obtained with enhanced tribological properties and lubrication performance during micro rolling of titanium foils.

Synergistic lubrication of phosphate glass and TiSiO4 nanoparticles for hot rolling of silicon steel

Lubrication was commonly needed for the moving mechanical counterparts to separate and lubricate the interface by a tribofilm, ensuring the long service life and easy slippage. Traditional, oil-in-water was applied as a hot rolling lubricant. Herein, the effect of the mixture of inorganic glass (sodium polyphosphate) and TiSiO4 nanoparticles (NPs) in the lubrication of silicon steel was studied. The results suggested that the optimal concentration of TiSiO4 NPs was 1 wt% in the 20 wt% sodium polyphosphate solution, which reduces the rolling force of 10.4% compared with the water lubricated condition. The lubrication mechanism was the synergistic effects of melt and nanoparticles lubrication. The combination of inorganic glass and nanoparticles can be extended to the lubrication in hot metal forming process for other steel and metals.

Zwitterionic polyelectrolyte brush modified chitosan nanoparticles as functional biolubricant with good friction-reduction effect

Osteoarthritis (OA) caused by the articular cartilage degeneration is closely related to the lubrication dysfunction of joint. At present, injecting biolubricants into the joint cavity is regarded as an effective strategy for the treatment of arthritis. Herein, a biocompatible chitosan (CS)-based nanoparticles (NPs) biolubricant (CS-PMPC@DS NPs) with dual function of lubrication and anti-inflammatory was fabricated. Zwitterionic polyelectrolyte brush poly(2-methacryloyloxyethyl phosphorylcholine, PMPC) was grafted onto the NPs via atom transfer radical polymerization (ATRP) strategy, while the anti-inflammatory drug (diclofenac sodium, DS) was encapsulated within them. Under the synergistic effect rolling lubrication and hydration lubrication mechanisms, the obtained biolubricant exhibited superior lubrication performance in either artificial joint materials or cartilage contacts, which presents great potential for OA treatment.

Kinetics study of cold rolling lubricant degradation through advanced instrumental techniques

AbstractResearch was focused on understanding the degradation kinetics of cold rolling oil used in the rolling mill at Tata Steel. Aged rolling oil leads to various surface defects. Ageing phenomenon is influenced through thermo‐mechanical behaviour, oxidation, hydrolysis and presence of iron fines. Ageing of cold rolling oil in presence of iron fines was systematically performed at various temperature followed by thermo‐mechanical wear tests. With variation in intensity of ageing, change in physico‐chemical parameters and fatty acid distribution (FAD) within triglycerides could be observed. The impact of the controlled ageing on performance parameters like lubrication, evaporation kinetics and oxidative stability were also studied. Thermo‐oxidative ageing depletes antioxidant concentration within the rolling oil resulting in rapid oxidation of unsaturated fats. This leads to rapid build‐up of high molecular weight ingredients resulting in formation of fatty acid soaps or scum. The resultant scum negatively impacts the boundary lubrication and evaporation kinetics of rolling oil.

In Situ Contact Analysis of Polyetheretherketone under Elastohydrodynamic Lubrication.

The influence of the complex material behavior of thermoplastic polymers in lubricated contacts is poorly understood. It affects the optimal design of power-transmitting thermoplastic machine elements and the exploitation of its potential, e.g., lightweight design, low-noise operation, and cost-effective manufacturing when injection-molded. This study applies the in situ thin-film sensor technology on a twin-disk tribometer in order to study the elastohydrodynamic lubrication of rolling–sliding contacts with the thermoplastic polymer polyetheretherketone. The results provide insights into the effects and relevance of its thermoplastic material properties. Pressure measurements reveal a typical hydrodynamic profile in combination with a large deformation of the contact zone. The influence of speed and slip ratio is thereby negligible. The temperature rise is low compared to elastohydrodynamically lubricated contacts with steel and is mainly influenced by the slip ratio as well as the load, whereas speed plays a subordinated role. In general, the heat generation is governed by shearing and backflow in the contact inlet zone at low slip ratios and shearing in the contact zone at high slip ratios. No effects attributed to viscoelasticity or loading frequency were observed at the operating conditions considered.

Study of a fuse‐polymerised inorganic glassy compound as a hot rolling lubricant

AbstractThis study had investigated the main degradation mechanism of a roll in hot rolling process, to reduce the wear and oxidation, a type of low‐melting glass fabricated by the fuse‐polymerisation method was tested as a hot metal forming lubricant by a ball‐on‐disc tribometer at high temperature. The results revealed that the roll degrades mainly due to the cracks initiated at the interface of carbides/matrix on the roll surface, then propagate along the interface, and being sheared off when the cracks confluence in the subsurface. The high‐speed steel (HSS) starts to be oxidised at 500°C, and grows heavily with increasing temperature. The recommended lubricant presented a desired lubrication behaviour for hot rolling process that generating a higher friction coefficient at low temperature and a lower one at high temperature. The friction coefficient, wear rate, and oxidation of HSS roll was reduced materially, which meets the requirements of hot rolling lubricant well.

Understanding the efficiency of roll lubrication when rolling AD33 aluminium alloy bands in industrial twin mill 175Ч300

This paper describes the results of a study that looked at the effect of contact conditions (including the use of industrial oil I40 (5%) for roll lubrication) on the deformation performance and power draw of a twin cold mill 175×300 operated by the machine building site in Dong Nai, Vietnam, when rolling 0.55 mm thick bands made of aluminium alloy AD33. The initial band size is 0.7×100×2,000 mm. The authors considered reological properties of the aluminium alloy, as well as the roll lubrication environment, to come up with a rational rolling process designed for 0.55×100 mm bands made from 0.7×100×2,000 mm rolled steel. Due to the use of industrial oil I40 (5%) in the mill 175×300, the number of passes could be reduced from three to two. The use of industrial oil I40 (5%) in the twin mill 175×300 ensured the specified precision and helped reduce the loads. Compared with dry rolling, due to the use of industrial oil I40 (5%), the rolling force could be lowered by 6 kN (8.3%) in the first pass and the power draw – by 0.025 kW (3.34%). At the same time, the second pass saved 2.96 kN (5.24%) of rolling force and 0,017 kW (3.95%) of power while ensuring the preset band thickness at the mill exit. Compared with dry rolling, when using I40 oil, the rolling force distribution efficiency along the band length rises by 22.7% in the first pass and by 14.64% in the second pass. When using I40 oil (5%), the strain distribution u nevenness along the band length drops by 39.15% — from 2.35 to 1.43% in the first pass and by 70.08% — from 3.81 to 1.14% in the second pass. When using I40 oil (5%), the thickness distribution along the length of aluminium band at the mill exit is more even than when the rolls are dry or use water. It also results in a minimized longitudinal thickness variation δh – i.e. 0.01 mm. These findings helped develop a rational rolling process for AD33 aluminium alloy bands that relies on the use of industrial oil I40 (5%) to lubricate the rolls of an industrial twin mill, while cutting the loads and saving power.

Effect of asymmetric material entrance on lubrication in cold rolling

An Integrated Digital Image Correlation (IDIC) method has been applied to the cold rolling process, the images clearly visualise the geometry of the roll bite and the inlet zone. A key, novel finding is that despite using coils and applying entry tension, the strip can enter asymmetrically in the rolling mill. Moreover, it is shown that asymmetric strip feeding results in an uneven lubricant film thickness between top and bottom strip surface. A method is detailed to feed the strip truly symmetrically in the mill, a procedure that is necessary for a meaningful experimental validation of lubricant film thickness models. For symmetric rolling processes the measured film thickness corresponds significantly better with the theory than for asymmetric processes.

Tribological and Lubrication Performances of Nano-WO3 and CaWO4 Contained in Water-Based Fluid for Steel Strip during Hot Forming

CaWO4 and WO3 nanoparticles were prepared by the sol-gel method and Pechini method. The morphology and structure of nano-CaWO4 and nano-WO3 were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Tribological, hot forming, and hot rolling lubrication properties of nano-CaWO4, nano-WO3, and mixed nano-CaWO4-WO3 as antiwear additives in water-based fluid were investigated using a four-ball friction and wear testing machine, Gleeble tester, and two-high rolling mill, respectively. Results showed that 0.3 wt% mixed nano-CaWO4-WO3 has excellent tribological properties in water-based fluid. The average wear scar diameter values decreased from 0.62 to 0.37 mm (mixed WO3-CaWO4) and the coefficient of friction value reduced from 0.080 to 0.064. This was due to the formation of a tribofilm (∼30 nm) on the worn surface during the forming process, avoiding direct contact between the metals. During Gleeble hot forming, the lubrication effect of the mixed nano-CaWO4-WO3 was the best. The nano-WO3-CaWO4 particles were relatively dispersed and dis not bond together under high temperature and pressure conditions, which played a role in reducing friction resistance between friction pairs. With the addition of 0.3 wt% mixed WO3-CaWO4 nanofluid, the surface quality was improved and it had the lowest surface roughness in the hot rolling process.

TiO2–SiO2 Nanoparticle-Stabilized Soybean Oil-in-Water Emulsions: Dispersion Stability, Rolling Lubrication Performance, and Surface Self-Cleaning Effects

Abstract Vegetable oil-in-water emulsions are common cold rolling lubricants. However, maintaining the required dispersion for polar oil droplets for consistent lubrication and proper surface self-cleaning after rolling remains a practical challenge. In this study, titanium silicate TiO2–SiO2 nanoparticle (NP)-stabilized soybean oil emulsions are produced and NPs functions as dispersant, lubrication enhancer, and detergent agent to clean up oil residue are explored. Cold rolling of SS316 strips reveals a threshold of NPs wt%, at which stably dispersed oil droplets improve tribology and lower the rolling parameters relative to without or at high wt% of NPs. Cleaner as-rolled strips are also obtained with NPs. Favorable results are attributed to the formation of NP-coating layers on oil droplets which enhances dispersion, optimizes plate-out while keeping adequate wetting, and provides a three-body abrasive rolling as opposed to two-body adhesion without NPs. A model of sliding–rolling lubrication in cold rolling is also discussed.

Tribological Study at the in-situ Situation for Aluminum 6061 and Steel EN31 During the Dry and Starved Lubricating Condition

Scientists are working on the development of materials and lubricants to reduce friction as well as wear at metalto- metal interfaces having relative motion. Aluminum is a widely used metal due to its high strength to weight ratio and availability in nature as compared to other metals that are manufactured by the rolling process. The output of the product quality and quantity from the rolling process requires less energy as compared to other manufacturing processes. A tribological study has been carried at the in-situ condition for the interface of Al6061 and steel EN31 on the pin on disc setup. To analyze the effectiveness of lubricant with mating surfaces, the effect of rolling lubricant was analyzed for tribological behavior and compared with the dry condition. The coefficient of friction was reduced up to 80% and the specific wear rate was reduced up to 96% by using rolling lubricant compared to dry conditions at the interface of metals that had relative motion.

Tribological performances of BP/TiO2 nanocomposites as water-based lubrication additives for titanium alloy plate cold rolling

The tribological performance and rolling lubrication properties of the BP/TiO2 nanocomposites as water-based lubrication additives (BP/TiO2-WL) were investigated by the ball-on-disc tribometer and four-high rolling mill. The results indicated that the average coefficient of frictions (COFs) and wear rate of the 0.08 wt % BP/TiO2-WL were reduced by 24.5% and 59.5%, respectively, compared with ultrapure water. The lubrication mechanisms of the BP/TiO2-WL were dominated by the synergistic effect between the BP nanosheets and TiO2 nanoparticles and the formation of tribological reaction films. In addition, due to the addition of the BP/TiO2 composite nanofluids, the rolling force and surface roughness of the titanium alloy plate during the rolling process were decreased by 17.5% and 32.2%, respectively. Therefore, BP/TiO2 nanocomposites as water-based lubrication additive have shown potential application in the field of titanium alloy plate cold rolling.

Analiza uticaja brzine vratila i spoljašnjeg opterećenja na režime podmazivanja radijalnih kugličnih ležajeva

Appropriate lubrication of the rolling bearing is needed to lower the friction between the surfaces in mutual contact and their wear. A lubricant should completely separate the rolling elements from the raceways. The values that affect the efficiency and regimes of lubrication are analyzed in the paper, after which it is introduced a lubrication regime coefficient. This coefficient makes it possible to choose in a simple and fast manner an optimum combination of rolling bearing and lubricant based on the known shaft speed, external load, and rolling bearing operating temperature. For certain bearings with radial contact and certain lubricants, the lubrication regime dependence on the shaft speed and contact load is shown.

Synthesis, characterization and lubrication performance of reduced graphene oxide-Al2O3 nanofluid for strips cold rolling

A novel nanomaterial reduced graphene oxide-Al2O3 nanocomposite (rGO-Al2O3) was synthesized through the hydrothermal method. The nanofluid containing rGO-Al2O3 nanocomposite was prepared as lubricant and exhibited superior dispersion stability. To clarify the lubrication mechanism of rGO-Al2O3 nanofluid, tribological tests and cold rolling lubrication experiments were conducted using the four-ball tribometer and two-high rolling mill. The results indicated that excellent anti-wear and friction-reducing properties as well as desired strip surface topography could be obtained under the lubrication of 0.20 wt% rGO-Al2O3 nanofluid. Induced by the interfacial tribochemical reaction, a bilayer lubrication film composed of adsorption film and reaction layer was formed at the friction interface. Through theoretical calculation and experimental characterizations, the thickness of lubrication film was about 25 nm. The adsorption film, dominated by nano-Al2O3 and graphene oxide fragments, played a vital role in synergistic lubrication. Meanwhile the reaction layer contained iron oxides (primarily Fe2O3 and FeO) with high mechanical properties. This bilayer structure ensured the denseness and continuity of the lubrication film, thus achieving significant lubrication performance.

Investigation to the skid resistance of asphalt pavement based on the movement of aeolian sand

Particulate contaminants that adhere to the surface have a major impact on asphalt pavement skid resistance. In this investigation, the skid resistance analysis system for the contaminated road was used to look at the decay characteristics of the pavement friction and the movement behavior of sand particles. To analyze the effect of aeolian sand on the skid resistance, the handheld laser scanner was used to collect the road surface macrotexture and then rebuilt the 3D model. The surface roughness of the contaminated road can be jointly characterized via the centreline average (Sa), the profile root-mean-square deviation (Sq), the height distribution symmetry (Ssk), and the height distribution kurtosis (Sku). The results show that aeolian sand has shear lubrication and rolling lubrication at the contact interface between the tire and the road. It fills the macrotexture and weakens the road's skid resistance. When there is aeolian sand adhering to the pavement, sliding and rolling friction provides the skid resistance of the asphalt road. Excessive aeolian sand has adverse long-term effects on skid resistance. It is recommended to routinely clean the road surface to maintain its original skid resistance when the amount of sand reaches to 0.625 kg/m2.