1. One of the factor: emulsion concentration (C)The influence of the emulsion concentration on the rolling surface is realized by the thickness of the oil film formed in the deformation zone. The concentration is too low and the oil equivalent precipitated in the deformation zone is low. The thickness of the oil film forming the minimum fluid lubrication must be 3 times the combined surface roughness. High concentration, high oil equivalent precipitation, oil film thickness is too thick, roll surface roughness “conduction” blocked. The surface roughness of aluminum plate also cannot be guaranteed. Through field testing and research. The results showed that the surface roughness of aluminum sheet was the least when the emulsion concentration of 59U in 2800mm cold rolling mill was maintained at 18%-22%.
Factor 2: cold rolling speed (VThe faster the speed of cold rolling helps the roll grasp the lubricating oil to establish the oil film thickness. The faster the speed is, the more emulsions will enter the deformation zone. The thicker the oil film is, the higher the surface roughness will increase. Moreover, for the emulsion with relatively large viscosity (refer to coal bar), the rapid rolling speed will cause uneven distribution in the roll surface and inconsistent oil film thickness in the deformation zone. Different roughness areas will appear on the surface of the aluminum plate, that is, forming a large strip or small strip of “chromatic aberration” phenomenon, the defect can not be eliminated after cleaning.
Factor 3: rolling pressure (F)With 59U emulsion lubrication, the roughness of 5A06 alloy wool supplied by “11 “hot rolling mill at different rolling pressures was measured.
When the rolling force is small. The thick oil film protects the roughness of the original surface of the rolled sheet and weakens the rolling and rolling effect of the roll on the rolled sheet. The oil film in the deformation zone has “isolation effect”. With the increase of rolling pressure, the thickness of oil film in deformation zone decreases, and the surface roughness of rolled plate also decreases. When the rolling pressure increases to a certain value (630t in this scheme), the oil film thickness will not decrease when it reaches the minimum critical condition of fluid lubrication. The surface roughness also tends to stabilize. When the rolling force continues to increase more than the bearing limit of the molecular oil film (1100t in this scheme), the oil film breaks. Dry friction is formed when the roll directly touches the surface of the rolled plate, resulting in the roughness increasing with the increase of rolling pressure.
Conclusion:(1) the original grinding roughness of the roll surface “dries up” with the production process, but it will not decrease infinitely, and will tend to a fixed value, which is determined by the original value and the lubricating medium.
(2) when the surface roughness of the product reaches a certain pressure reduction rate, it has nothing to do with the surface roughness of the original incoming material. But it is affected by roll roughness, rolling pressure, rolling speed and emulsion concentration.(3) there is an optimal production range for roll roughness, rolling pressure, rolling speed and emulsion concentration in different machine lines, in which better surface roughness can be obtained. Its value can be measured by this test method.