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

研制了一种用于直接观察轧制界面的新型轧制设备。在一台二辊轧机直径157 mm的上辊中，同轴嵌入了一台带有微距镜头的CCD相机。与辊曲率相匹配的初步研磨的透明玻璃块也沿径向嵌入。两个正交轴由位于滚动轴上的反射镜光学连接。通过安装在轧辊边缘的滑环采集信号。数字录像机能够以每秒30幅图像的速度稳定采集一分钟以上的图像。采用不同粘度的石蜡基础油作为润滑剂。对厚度为2 mm、宽度为40 mm的纯铝板，在0.167m/S的轧制速度下，压下量为5%、10%或15%，结果表明：(1)在轧辊咬合区，与油膜厚度有明显的反差；暗部的形状(应该是薄板的微观沟谷)富含平行于轧制方向的成分。(2)在轧辊咬合出口处，润滑剂的枝晶结构变得更加清晰，并平行于轧制轴。这可能是由于加压的高粘度润滑剂释放到自由空间所致。(3)停留在玻璃工具上的润滑剂随着时间的推移表现出松弛。因此，在进行塑性流体动力润滑时，应考虑润滑剂粘度的动态行为。(4)镜面精整钢板也表现出与轧钢机精轧钢板相似的润滑行为。另一种具有人造微孔的试件表明，高粘性的树枝状结构通过承重区出现。

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.