Direct observation of rolling interface of metal sheet by CCD Camera embedded into a roll and a study of lubrication mechanism

研制了一种直接观察轧制界面的轧制装置。在两辊轧机的直径为157 mm的上辊中，同轴地嵌入具有微距透镜的CCD照相机。还在径向方向上嵌入预先研磨以匹配辊的曲率的透明玻璃块。两个正交轴通过位于滚动轴上的反射镜光学连接。信号是通过安装在轧辊边缘的滑环采集的。数字录像机能够以每秒30幅图像的速度稳定采集图像超过一分钟。具有不同粘度的石蜡基油用作润滑剂。在0.167m/s的轧制速度下，以5%、10%或15%的压下率轧制2 mm厚、40 mm宽的纯铝板。结果表明：（1）在轧辊咬入处，存在与油膜厚度有关的反差。暗部的形状（被认为是板的微观谷）富含平行于轧制方向的分量。(2)在轧辊咬入出口处，润滑剂的枝晶结构变得更加清晰，且与轧制轴线平行。这可能是由于加压的高粘度润滑剂排放到自由空间造成的。(3)停留在玻璃工具上的润滑剂随着时间的推移而显示松弛。因此，润滑剂粘度的动态行为应考虑到与塑性流体动力润滑。(4)镜面成品板也显示出与辊轧机成品板类似的润滑剂行为。另一个通过模压制备的具有人工微观空腔的试样表明，高粘性树枝状结构发生在轴承区域。

A new rolling equipment for direct observation of rolling interface is developed. Into the upper roll of 157 mm in diameter of a two-high mill, a CCD camera with a macro lens is co-axially embedded. A transparent glass block preliminarily ground so as to match the curvature of the roll is also embedded in a radial direction. The two orthogonal axs are optically connected by a mirror locating on the roll axis. Signals are acquired through a slip-ring equipped at the edge of the roll. A digital video recorder enabled stabilized acquisition of images for over a minute at a rate of 30 images per second. Paraffinic base oils with varied viscosity were used as lubricants. A pure aluminium sheet of 2 mm thick and 40 mm width is rolled at a reduction of 5,10 or 15% at a rolling speed of 0.167m/s. The results are summarized as follows :(1) At the roll bite, a contrast connected with the thickness of the oil film is visible. The shape of the dark part (which is supposed to be the microscopic valleys of the sheet) is rich in the component parallel to the rolling direction.(2) At the exit of roll bite dendritic structure of the lubricant becomes more clear and parallel to the rolling axis. This is probably caused by the emission of a pressurized high-viscosity lubricant to the free space.(3) The lubricant staying on the glass tool shows relaxation as time passes. Thus, the dynamic behavior of lubricant viscosity should be taken into consideration in relation to the plasto-hydrodynamic lubrication.(4) Mirror finished sheets also showed similar lubricant behavior as the roll mill finished sheets. Another specimen with artifical microscopic cavities prepared by coining showed that the high viscous dendritic structure occurred through bearing areas.