The emulsion for aluminum hot rolling is prepared from hot rolling oil and water. The concentration of the emulsion is usually in the range of 2~10%, of which the water phase accounts for about 90~98% of the emulsion. Therefore, the water in the emulsion for aluminum hot rolling plays a very important role in the production of aluminum hot rolling and the quality of plates and strips.
1. Classification of water and related water Water can be classified into: name
| Hardness/(mmol · dm-3)
|
Extremely hard water
| >4.5
|
Hard water
| 3.0~4.5
|
Medium hard water
| 1.5~3.0
|
Soft water
| 0.5~1.5
|
Extremely soft water
| <0.5
|
Generally, hardness and conductivity can be used to measure the purity of water. The hardness of water is the total concentration of calcium and magnesium ions in water, while the conductivity is the size of ionic conductivity in water. Natural water: In addition to Ca2+and Mg2+ions, it also contains other ions, which have different effects on water quality. Soft water (sodium ion exchange water): the water is softened by sodium ions to remove Ca2+and Mg2+. The water has the following characteristics: the hardness of the obtained water decreases, but the pH value remains unchanged; The total amount of anions and cations in the water is basically unchanged, the content of Na+will increase significantly, and the conductivity is basically unchanged; As the regenerant is NaCl, the content of chloride ion (Cl -) in sodium ion softened water is higher than that in raw water. Deionized water: since all ions dissolved in water are removed, the hardness and conductivity of water are greatly reduced, which is conducive to production and use. 2. Selection and influencing factors of emulsion mixing water for aluminum hot rolling 1) Use natural water to prepare liquid Calcium and magnesium ions in natural water are the most harmful to emulsion. Calcium and magnesium ions can form insoluble substances with emulsifiers and some effective ingredients in lotion, which has a great impact on the stability of lotion and the function of effective ingredients. They not only affect the stable use of emulsion, but also may affect the normal rolling production. 2) The softened water is used to prepare the solution Because calcium and magnesium ions are harmful, people use sodium ion exchange resin to replace divalent calcium and magnesium ions with univalent sodium, which reduces the harm of calcium and magnesium ions to a certain extent. After replacing calcium and magnesium with sodium, the hardness of water decreased a lot, but the content of metal ions in lotion did not decrease, so the conductivity did not change significantly. 3) Solution preparation with deionized water Deionized water is the best choice for preparing emulsion for aluminum hot rolling. The use of deionized water for solution preparation can fundamentally eliminate the possible impact of water quality on lotion, and the possible harm of ions in water will no longer exist. The direct harm of Ca2+, Mg2+and the harm caused by the accumulation of Na+, Cl - plasma will be reduced to the minimum. Then, in the daily use of emulsion, the metal ions rolled into the lotion can be eliminated or reduced through daily maintenance, so that the emulsion can better and long-term service for the stable rolling and good surface quality. 3. Water index and relevant requirements for emulsion preparation of aluminum hot rolling 1) General testing items and index requirements of water for liquid preparation: project
| test result
|
Hardness (ppm)
| 0
|
Conductivity (uS/cm)
| <10~20
|
pH
| 6-7
|
Chloride ion content (ppm)
| 0 |
In addition to the requirements for the indicators of water for liquid preparation, the temperature and method of water for liquid preparation are also required when preparing emulsion for aluminum hot rolling. 2) Temperature of liquid preparation water The temperature of liquid mixing water should be better than 40 ℃, and the surface tension of water is large (73). It is difficult to emulsify oil into water because it does not wet oil on its interface. The surface tension of hot water is relatively small, which can reduce the viscosity of oil. Thermal movement is conducive to molecular movement and dispersion. In addition, the rational use of emulsifiers, as well as the necessary mechanical shear forces such as circulation, can make oil droplets well dispersed into the water phase, A better oil in water emulsion is formed and is used well in aluminum hot rolling production. 3) Solution preparation method As far as aluminum hot rolling is concerned, the emulsion used is mostly in a metastable state, and there are strict requirements for particle size distribution or emulsion stability. Therefore, there are also certain requirements for the oil filling method and system circulation during liquid preparation. To prepare aluminum hot rolling emulsion, rolling oil shall be added to water for preparation. If the rolling oil has good emulsification, the emulsion can be directly added to water and stirred to quickly form emulsion. However, when most rolling oils are prepared, it is necessary to add liquid in front of the circulating pump. With the help of the mechanical shear force of the circulating pump, the oil in water emulsion with reasonable oil droplet distribution and suitable for hot rolling production can be formed. 4. Conclusion The water phase in the emulsion for aluminum hot rolling accounts for a large proportion, and the selected mixing water plays a vital role in the stability of the emulsion and the production and quality of the strip. Deionized water is the best choice for preparing emulsion for aluminum hot rolling. The detection and control of liquid mixing water index and the selection of liquid mixing water temperature and liquid mixing method are also very useful for obtaining good production and aluminum plate quality.
