Cold rolling usually takes the steel coil with a thickness of 2~4mm after hot rough rolling and finish rolling as the blank, and is rolled into a thin plate with a thickness of 0.8mm ~ 0.0 1mm by a multi-roll mill (reversible or continuous rolling). Because cold metal has great deformation resistance, the rolling force of modern cold rolling mill has reached thousands of tons, and the rolling speed is close to 2500m/min. Obviously, in such a high-speed deformation process, on the one hand, due to the friction between molecules inside the metal, a lot of heat energy is inevitably generated; On the other hand, the thinning (extension) of the rolled material inevitably makes the surface of the roller and the rolled material move relatively.
The basic requirements for lubricants in cold rolling process are:
1. Proper oiliness, that is, boundary oil film can still be formed under large rolling pressure to reduce friction resistance and metal deformation resistance; Reduce the wear of the drum and prolong the service life of the drum; Increase reduction, reduce rolling passes and save energy consumption. But what needs to be considered is that there must be some friction between the roller and the steel from time to time, so that the steel can bite into the roller. If the friction coefficient is too low, it will slip. Therefore, 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 extent and realize constant temperature rolling to keep the roll profile stable and the strip thickness uniform;
3. It has a good cleaning and cleaning effect on the surface of strip steel. In order to remove impurities and dirt mixed outside and improve the surface quality of steel;
4. Good physical and chemical stability. In the rolling process, there is no chemical reaction with the metal, which 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 needed, the production process of direct annealing without degreasing cleaning is adopted. This requires that the lubricant will not be annealed and corroded because it remains on the steel surface (that is, spots will be produced on the steel surface);
6. Good filtration performance. In order to improve the surface quality of steel, some rolling mills use high-precision filtering devices (such as diatomite) to remove impurities in oil to the maximum extent. At this time, it is necessary to avoid the additives in the engine oil being adsorbed or filtered to maintain the quality of the engine oil;
7. Good oxidation stability and long service life;
8. Good antirust performance. For short-term storage between processes, it can play a good role in rust prevention;
9. Do not contain substances harmful to human health and pungent odor;
10. The oil source is extensive, easily available and low in cost.
Hot rolling process lubrication
This is of great significance to increase production, reduce consumption and improve productivity of hot strip mill. Practice in various countries has proved that the use of hot rolling oil can significantly reduce roll wear, reduce power consumption, improve the surface quality of steel plate and increase productivity.
The following benefits can be obtained by using hot rolling (which has been proved by practice):
1. improves the surface condition of the roller.
2. The unit consumption of the roller is reduced.
3. The consumption of electric energy is reduced.
4. The surface quality of strip steel is improved.
5. Reducing the rolling pressure makes it easy to roll thin gauge strip steel.
6. Promote the research of hot rolling theory.
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