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?Cviscosity 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.     

Dry lubrication for rolling element spacecraft parts

Dry lubrication of spacecraft hardware is reviewed and some of the logic and test philosophy used in selecting and qualifying the dry lubricants presented. Examples of current applications are given, together with comments on and data from selected references     

油气润滑应用于滚动轴承的发展现状

介绍油气润滑系统的特点、组成及在当今国内外,特别是国内轴承行业的研究与应用现状。     

Synthetic lubricants in cold strip rolling

The embedded-pin technique is used to monitor the variation of the interfacial forces during cold rolling of aluminium slabs. The results confirm earlier conclusions, indicating that the frictional coefficient is a strong function of the process and material parameters. Coefficient of friction values deduced from forward slip measurements are close to the present data, confirming that in spite of several drawbacks of the experimental technique, it can yield very useful results. Lubricants are shown to reduce the loads on the rolling mills in a significant manner.     

A review of thermoelastohydrodynamic lubrication in rolling and sliding contacts

This paper reviews the state of thermoelastohydrodynamic lubrication in line contacts. A comparison of the theoretical studies and correlation of the theory and experimental results are presented.     

冷挤压流体动力润滑模型的建立

分析了冷挤压润滑过程，在考虑冷挤压工况下润滑剂呈非牛顿特性的影响，分别建立了冷挤压非稳定状态和稳定状态的流体动力润滑模型，运用该模型可以计算冷挤压过程的润滑油膜厚度、油膜压力以及摩擦力的分布。     

Pure rolling elastohydrodynamic lubrication of short stroke reciprocating motion

The behavior of point contact elastohydrodynamic lubrication (EHL) films under pure rolling short stroke reciprocating motion is investigated using both optical interferometry technique and theoretical analysis. The EHL films are recorded with a high-speed color camera and simulated with multigrid techniques. General variation of oil film under point contact reciprocating motion is explained by a comparison between a fully flooded simulation and an experiment with a frequency of 7.78 Hz. Influence of starvation is considered by another simulation under a higher working frequency of 14.4 Hz and the simulated results are compared with experimental results. Both simulations show good agreements quantitatively with experiments. In addition, general tribo-characteristics of EHL under fully flooded and starved conditions are discussed.     

Multi-scale roughness transfer in cold metal rolling

We report on a comparative Atomic Force Microscope (AFM) multi-scale roughness analysis of cold rolled Al alloy and steel roll, in order to characterize the roughness transfer from the steel roll to the workpiece in cold strip rolling processes. More than three orders of length-scale magnitudes were investigated from 100 microns to 50 nanometers on both types of surfaces. The analysis reveals that both types of surfaces are anisotropic self-affine surfaces. Transverse and longitudinal height profiles exhibit a different roughness exponent (Hurst exponent) ζ=0.93±0.03 and ζ=0.5±0.05 Different length-scale cut-offs are obtained in each direction l^sup=50μm, l^sup>100μm. Height and slope distributions are also computed to complement this study. The above mentionned self-affine characteresitics are found to be very similar for the roll and the strip surfaces, which suggest that roughness transfer takes place from the macroscopic (100 μm) to the very small scale (50 nm).     

冷连轧机中的活套控制

论述全连续冷轧机中的活套控制原理及保证活套量准确的控制方法。     

Transient elastohydrodynamic lubrication film thickness in sliding and rolling line contacts

The contact behavior between cam and follower is greatly influenced by the kinematics and dynamics of the whole valve train system. This is the reason that both shape and thickness of the fluid film in the contact gap are mainly determined by applied loads and relative contact speeds as well as the curvatures of contacting elements. Most of the studies about lubricant film behavior between cam and follower have been performed without a consideration of transient effects in the contact gap. For the computational difficulties of transient effects, most contact conditions such as relative contacting speeds have been regarded as quasi-steady state during the whole operating cycle. In this work, in order to obtain stable convergence, a multigrid multi-level method is used for the computation of load capacity in the lubricant film. Nonlinear valve spring dynamics are also considered in the same way as Hanachi’s. From the computational results, transient EHL film thicknesses under the conditions of different contact geometries are computed for a pushrod type valve train system during an engine cycle. Several results show the squeeze film effect, which is generally not found with conventional EHL computations of the cam and follower contact. The results are also compared with those by the Dowson-Hamrock (D-H) formula, which does not consider the dynamic film effect. Without the dynamic film effect as in D-H’s formula, the minimum film thickness is highly dependent on the entraining lubricant velocity, whereas the minimum film thickness including the squeeze film effect is dependent on the applied load.     

钢管冷斜轧成型研究

提出了采用冷斜轧方法生产冷轧钢管的新工艺 ,对其理论成型的特点进行了研究 ,对实践该新工艺进行了探讨。冷斜轧技术的应用将会给企业带来好的经济效益     

The causes of edge cracking in cold rolling

Surface cracking in predominantly compressive bulk forming processes such as upsetting and rolling are well-known examples of the numerous possible defects that may occur in metalworking operations. Both barrel cracking in upsetting and edge cracking in rolling have been attributed to secondary tensile stresses induced at the work-piece surfaces by inhomogeneous deformation.After introducing the general concepts of ductility and workability and the mechanisms of ductile fracture, this review examines the parameters which influence the onset of edge cracking in rolling. These parameters are the state of stress and strain in relation to the apparent material ductility, which factors are influenced by roll camber, applied tensions, frictional conditions, spread, edge shape and the ductility of the metal.     

Energy conservation in stainless steel cold rolling applications

In order to predict the performance of rolling oils in actual production mills, from tests in laboratory mills, the influence of various factors, such as shape factors work roll diameter (D), strip thickness (h₁), operating conditions (reduction rate (r), peripheral velocity of roll (U₀), strip velocity (U₁)) and kinematic viscosity of the rolling oil (υ₀) was investigated. A parameter RLI (Rolling Lubrication Index = u₀(U₀+U₁)(1−r)(D/2h₁.r)^½) was found to be useful in predicting lubricating conditions in actual production mill applications. The coefficients of friction of mineral oils, some synthetic hydrocarbons including polybutene, and several kinds of additives were obtained from laboratory mills under the same condition of RLI value as that for finish rolling in actual production mills. With hydrocarbons, paraffins showed the lowest coefficient offriction, while aromatics exhibited a higher coefficient of friction, with naphthenes showing the highest. A high-quality rolling oil was formulated using a combination of ester and paraffinic mineral oil. It is observed that this new oil can save 14% of energy consumed by a laboratory mill compared with conventional rolling oils. In production mills, nearly the same energy conservation level can be achieved.     

An analysis of the mechanisms of grease lubrication in rolling element bearings

There are over eighteen billion bearings in use in the world, and most are grease lubricated. Grease is chosen for a variety of reasons: it gives low friction, is easily confined, and has a long lubricating life at low cost. In many applications, the grease is expected to lubricate effectively over a wide range of conditions and for extended periods. For such applications, lubricant failure leads to instantaneous and rapidly increasing damage of the components and eventually breakdown. Thus, an improved understanding of the fundamental aspects of grease lubrication has far-ranging technical and economic implications. Despite the overwhelming importance of this subject, very little is known about the mechanisms of grease lubrication and the relationship between composition, lubrication performance, and life. This paper attempts to summarise current understanding of grease lubrication mechanisms in rolling element bearings and to consolidate the different aspects of this complex topic.     

偏心机构在冷轧机中的应用

针对小型冷轧机手动压下装置压下速度慢,换辊时间长的缺点,设计了一种低成本,操作方便、换辊迅速的双偏心压下装置,并对自锁条件、驱动力大小与轧制力的关系、辊缝与旋转角的关系进行了分析和计算.     

A study of rolling bearing fatigue life with mineral oil lubrication

Tests on mineral oil lubricated deep groove ball bearings show that there is an optimum lubricant viscosity to ensure maximum rolling contact fatigue life. The results are explained by lubricant film thickness measurements and the application of E.H.L. theory. The optimum lubricant viscosity increases with increase of load and decreases with reduction of speed.     

Mixed film lubrication of strip rolling using O/W emulsions

A numerical study on the oil concentration effect of O/W emulsion in cold rolling operating in the mixed film lubrication regime has been carried out. The developed scheme is able to calculate oil concentration at any point within the inlet zone (IZ) and work zone (WZ), rolling pressure, film thickness, and contact ratio for various rolling speeds. Hence the intertwined effects of oil concentration of the supplied emulsion and rolling speed on strip rolling are discussed. The study encompasses mixed film regime with speeds S range from 10⁻⁵ to 10⁻³ and supplied emulsion's oil concentration levels λ_ds range from 5% to 90%. The result shows that a moderate rise in oil concentration occurs in the IZ followed by a rapid one at the beginning of the workzone. In most cases, the oil in the emulsion would have been transformed from disperse phase to continuous phase throughout the WZ. Notwithstanding further concentration, which depends on the oil concentration of the supplied emulsion, could still occur in the WZ. The effect of the concentration process is predominantly seen in the development of the lubricant pressure whilst its effect on the total pressure is less pronounced. The analysis of the results suggests that it is possible to lower the emulsion oil concentration without detrimental effects on the rolling process; and from the analysis of the outlet film thickness, it is shown that the variation of emulsions’ oil concentration could control the exit lubricant film thickness and consequently the strip surface quality.     

冷轧机组带钢纠偏研究

在钢铁生产过程中,由于某些原因,带钢在通过冷轧机组时出现跑偏现象,影响到正常生产。针对冷轧机组中的跑偏现象,进行了深入研究,提出了纠偏的措施,分析了各种设计方法的可行性和有效性,并提出了提高可靠性的设计方案。     

现代冷轧钢板生产中的平整设备

阐述平整机组的工作原理、类型及平整机的发展,并以我公司与德国MDS联合设计制造的12200mm单机架四辊平整机为例,较详细地介绍了平整机工艺及设备组成,以供今后平整机设计参考。