The emulsion mainly consists of Base Oil, emulsifiers, additives, and water. In addition to emulsifiers, the performance and content of other components also have a significant impact on the lubrication performance, usage effect, and service life of the emulsion. The main functions of emulsions include cooling, lubrication, rust prevention, etc., and their chemical properties have a certain impact on their functions. Its cooling function is mainly used to cool the rolled piece and roll, reduce deformation of the rolled piece, improve flatness accuracy, extend roll life, and thereby improve rolling speed and reduction, and improve productivity. Various lubricant additives, such as fatty acid oil, amide esters, polymers, etc., are added to existing emulsions, which can play a role in rolling lubrication, effectively reduce the friction force between the roller and the workpiece, improve the accuracy and surface finish of the product, and extend the service life of the roller.
1. The Effect of Emulsion Temperature on Rolling Force The use temperature of emulsion is also one of the main factors affecting rolling lubrication, and the temperature affects the size and spread of dispersed emulsion oil droplets. A low temperature may cause the emulsion to become rancid and grow bacteria, and low temperature is not conducive to the use of additives such as extreme pressure agents in rolling oil, which affects lubrication; If the temperature is too high, the particle size of the emulsion is easy to grow, which affects the stability of the emulsion and increases fuel consumption. Under identical other conditions, different emulsion temperatures have a certain impact on rolling strip steel. 2. The Effect of Emulsion Concentration on Rolling Force The concentration of emulsion is an important parameter during the use of emulsion, and there are different appropriate values of emulsion concentration when rolling different types and specifications of strip steel. The high concentration of emulsion results in an increase in the amount of free water and the amount of oil film introduced, which leads to over lubrication and can cause slipping between the strip steel and the rolling mill, leading to scratches, rolling mill resonance, and poor plate shape; The low concentration of the emulsion results in a decrease in the amount of water released, a decrease in the amount of oil film introduced, an increase in energy consumption, resulting in insufficient lubrication and blackening of the rolled plate surface, which is prone to thermal scratches, rolling mill resonance, and other phenomena. Adjusting the emulsion concentration is one of the important means to achieve greater reduction rate and reduce rolling force. Under the same other conditions, different emulsion concentrations have a certain impact on rolling strip steel. 3. The Effect of Emulsion Saponification Value on Rolling Force Saponification value is an important index to evaluate the lubrication performance of rolling oil, which reflects the content of fatty acids in animal and vegetable oils in rolling oil. Usually, potassium hydroxide is used for saponification with concentrated rolling oil. The milligram of potassium hydroxide consumed by 1 g of concentrated rolling oil is the saponification value of rolling oil. It is generally believed that the higher the saponification value of rolling oil, the better its lubrication effect. The impurities in the emulsion do not have lubricating ability, so if the content of impurities in the emulsion is high, the saponification value of the emulsion will decrease. When the saponification value of the emulsion decreases, the lubricating ability of the emulsion per unit volume also decreases. 4. Impact of pH The changes in alkalinity or acidity of emulsions during use are related to the oxidation reactions that occur in the emulsions. The change in pH of the emulsion is also related to the change in free fatty acid content. The change in pH can easily enhance the hydrolysis of rolling oil, resulting in saponification and potentially changing the efficiency of the emulsion. When pH<5, the emulsion is unstable and may cause deterioration and rancidity. When pH>8, the particle size of the emulsion decreases, causing lubrication difficulties during cold rolling and affecting rolling speed. 5. Influence of conductivity Conductivity is the size of all inorganic salt components present in the emulsion. By measuring the conductivity, we can determine the size, quantity, and trend of various ions in the emulsion. When the pH value of the emulsion suddenly decreases and the conductivity increases during use, it is possible that inorganic salts enter the emulsion (such as excessive acid concentration in the pickling tank and residual acid on the strip steel being carried into the rolling mill), which makes the strip steel prone to rust and erosion. When the pH suddenly increases, the conductivity also suddenly increases, possibly when alkali containing substances enter the emulsion. A high conductivity indicates a high iron and ash content in the solution. 6. Effects of chlorides The chloride in the emulsion has the greatest impact on the rolling process and strip quality. Because strip steel rolled with emulsion containing high chloride ions may exhibit rust spots after annealing. Chlorides have a significant impact on electrical conductivity. When the chlorine content increases, the conductivity sharply increases. When producing rust spots on strip steel and galvanized sheet, we need to consider the following issues: 1) The chloride ion content in the pickling and rinsing tank is too high. 2) The water chloride ion content of the prepared emulsion exceeds the standard. 3) The chlorine content of the emulsion exceeds 50mg/L. 4) The strip steel is left in the air for too long and the air is humid, so to ensure the qualification rate of the cold plate, it is necessary to control the chlorine content in the emulsion. 7. The impact of iron content The dissolved iron in the emulsion reacts with the free fatty acids in the emulsion, resulting in iron soap that is insoluble in water but soluble in organic matter and accumulates in the oil tank, affecting the stability and lubrication effect of the rolling emulsion. By separating the rolling oil with high iron soap content, it can be seen that the appearance of the rolling oil has changed, becoming black and cloudy. The high iron content is generated when the oil concentration is too low, and due to insufficient lubrication, iron powder is generated by the friction of the rolling strip steel. In production, we need to minimize the content of iron powder as much as possible, ensure a certain concentration, and ensure that the emulsion has good lubrication performance, reduce the friction between the strip steel and the roller, and reduce the generation of iron powder residue. Appropriate filtration and adsorption are used in the emulsion circulation system to remove solid oil sludge and iron powder residue. 8. The impact of free fatty acids During the rolling process, the reduction of free fatty acids results in a decrease in rolling lubrication performance. Free fatty acids are generally used to improve the lubrication effect of emulsions, but they cannot suddenly rise. If they suddenly rise, it indicates that the emulsion undergoes chemical changes, bacterial growth, and oxidation is prone to rancidity. 9. Impact of ash content The ash content in the emulsion mainly causes the emulsion to become dirty, affecting the cleanliness of the surface of the strip steel. If the emulsion is too dirty, it indicates that the emulsion contains too much ash. In this case, the iron content will definitely be high. The active oil content in emulsions with high iron content will decrease, resulting in a decrease in lubrication performance. The emulsion is too dirty, and the surface of the rolled strip steel is prone to spots, which reduces the grade and qualification rate of the product.
