Taking aluminum foil as the object of annealing analysis, the commonly used rolling oil is B-1 type rolling oil. After testing, the rolling oil contains S1 and S2 rolling additives, of which the S1 additive is added to the B-1 base oil at a mass fraction of 5%. S1 and S2 rolling additives require subsequent thermal analysis in the form of simple rolling oil additives. After testing, the basic properties of rolling oil are: dynamic viscosity at 40 degree , flash point at 85 degree , and distillation range at 205~245 degree . Use the above basic rolling oil and rolling additives to continuously change the temperature change value of the oil and observe the natural change reaction of the oil under heat loss. In addition, the superheat differential analysis method was used to analyze the oxidation, decomposition and polymerization reactions that occur when the oil is heated. Understand the reasons for the formation of cold marks during the annealing process of aluminum foil.
The experimental results show that the corresponding thermal difference analysis curve has two obvious endothermic peaks with an initial temperature of 55 degree , indicating that the rolling oil has a certain volatility. The first stage terminates at a weight loss temperature of approximately 225.5 degrees Celsius, at which point the weight loss percentage can reach a maximum of approximately 58%. After the end of the first stage, the curve begins to change smoothly and gradually enters the second weight loss stage. At this time, oxidation reactions and thermal analysis reactions will occur, which will appear as rolling oil spots during the annealing process. Since the structure of S1 additive is not easily oxidized directly, there is no obvious endothermic peak. The effect of S2 additive is more obvious in the second stage of weight loss, when the additive produces obvious oil spots.
Analysis shows that the pollution quality problems caused by the aluminum foil annealing process originate from the two-stage weight loss reaction of rolling oil and additives. Since the base oil evaporates quickly, has low residue, and has less surface contamination, the minimum contamination level is basic.
When S1 additive is added alone, due to the lower overall content, the amount of contamination on the annealed surface is also lower, and it belongs to the second level. When S1 and S2 additives are mixed, due to the slow evaporation of the overall annealing process, severe oxidation reactions will occur, forming a variety of oil spots. S2 is more serious than S1, so in practical applications, only one additive can be used at most. Otherwise, a lot of aluminum foil quality problems will occur.
In the actual aluminum foil annealing process, in order to prevent the rolling oil from affecting the quality of the aluminum foil, the annealing and deoiling processes should be completed as much as possible in the first stage of weight loss. Generally, the annealing and deoiling temperature of aluminum foil is between 220 degrees Celsius and 240 degrees Celsius. This temperature mainly depends on the final distillation point.