In the process of rolling steel (mainly cold rolling), in order to reduce the friction between the roll and the rolled material, reduce the rolling force and power consumption, make the rolled material easy to extend, control the rolling temperature, and improve the quality of rolled products, it is necessary to Adding lubricating coolant between the contact surface of the roll and the rolling material, this process is called rolling process lubrication.
Cold rolling is usually performed by hot rough rolling and finishing rolling to obtain a steel coil with a thickness of 2 to 4 mm, which has been pickled and annealed. It is rolled by a multi-roll mill (reversible or continuous rolling) to a thickness of 0.8 mm to 0.01. mm sheet. Due to the large deformation resistance of cold metal, the rolling force of modern cold rolling mills has reached thousands of tons, and the rolling speed is close to 2500 m / min. Obviously, during such a high-speed deformation process of metal, on the one hand, a large amount of thermal energy is inevitably generated due to the friction between the molecules inside the metal; on the other hand, the reduction (extension) of the rolling material inevitably causes the roll to face the rolling material motion.
The basic requirements for cold rolling lubricants are:
1. Appropriate oiliness, that is, boundary oil film can still be formed under great rolling pressure to reduce friction resistance and resistance to metal deformation; reduce roller wear and extend roller service life; increase rolling reduction and reduce rolling path Times, saving energy consumption. However, it is necessary to consider that there must be a certain friction between the roller and the steel from time to time, so that the steel can bite into the roller. The friction coefficient is too low and it will slip. So the lubrication performance must be appropriate
2. Good cooling ability, that is, it can absorb the heat generated in the rolling process to the maximum, and achieve constant temperature rolling to maintain the roll with a stable roll shape and keep the strip thickness uniform;
3. Has a good flushing and cleaning effect on the surface of the strip. In order to remove impurities and dirt mixed into the outside world, improve the surface quality of steel;
4. Good physical and chemical stability. During the rolling process, it does not react with the metal and does not affect the physical properties of the metal;
5. Good annealing performance. In modern cold-rolled strip production, in order to simplify the process, improve labor productivity, and reduce costs, when intermediate annealing is required, a direct annealing process is used without degreasing and cleaning. This requires that the lubricant is not annealed and corroded due to its residual on the surface of the steel (ie, spots on the surface of the steel);
6. Good filtering performance. In order to improve the surface quality of steel, some rolling mills use high-precision filtering devices (such as diatomaceous earth) to minimize the impurities in the oil. At this time, it is necessary to avoid the additives in the oil from being adsorbed or filtered out to maintain the quality of the oil;
7. Good oxidation stability and long service life;
8. Good rust resistance. For short-term storage between processes, it can play a good role in rust prevention;
9. Should not contain substances harmful to human health and irritating odors;
10. Wide range of oil sources, easy to obtain and low cost.
Hot rolling process lubrication
Increasing the output of hot-rolled strip mills, reducing consumption, and increasing productivity are extremely important things in the rolling process. Practices in various countries have proven that the use of hot rolling oil can significantly reduce roll wear, reduce power consumption, improve the surface quality of steel plates, and increase productivity.
The following benefits can be obtained with hot rolling (as proven in practice):
1. Improved the surface condition of the roll.
2. Reduce the unit consumption of the roll.
3. Reduced power consumption.
4. Improved the surface quality of the strip.
5. Reduce rolling pressure, easy to realize rolling of thin gauge strip.
6. Promote the research of hot rolling theory.