Hot rolling is done at the highest possible temperature to reduce the loads and reduce the flow stress to achieve a large reduction. Due to the need to re-control the crystallization and precipitation, depending on the alloy as well as the aggregation, a high temperature limit is applied.
During normal rolling, the coarse structure transforms into a bulk structure and recrystallizes to a finer grain size. The primary sediments are coarsely crushed and evenly distributed. Decreasing the temperature during rolling and increasing the vacuum concentration in the network due to deformation leads to more precipitation of the secondary phases.
Due to the microstructure, hot rolling deformation and annealing steps are observed sequentially. The predominant metallurgical properties are recrystallization and development of crystal (texture) orientations. Both processes are interconnected and affected by continuous rainfall
. Recrystallization is mainly determined by the alloy system and processing conditions. In high purity aluminum, the grain boundary mobility is high and the material already shows rapid recrystallization during processing (dynamic recrystallization).
Conventional industrial alloys, dynamic recrystallization can be observed at very high temperatures, this effect is not only due to nucleation and growth, but mainly due to local swelling of the grain boundary. For these materials, recrystallization usually occurs at standstill or after rolling at high temperatures (after dynamic or static recrystallization).
In commercial pure alloys such as AA1050, which is commonly used for foil or lithographic sheet packaging, low-solubility elements such as Fe and Si interact with the grain boundaries to prevent recrystallization in the presence of finely dispersed sediments.
The presence of manganese and chromium gives the same effect as long as the elements are not attached to large particles. In the Al-Mg-Mn alloy system, which is used in significant quantities for beverage cans or automotive components, recrystallization covers a wide range of industrial conditions and can therefore be greatly influenced by the choice of rolling parameters. . In industrial practice, the recrystallization structure can be obtained in a separate annealing process, but more advanced technologies use the rolling temperature on the coil.
In a typical hot mill, aluminum ingots are dipped in kilns before being brought to the reverse mill or shredder to make a long, narrow strip. The tape is significantly reduced, we bring it to the Finishing Mill, which is a series of rolls downstream of the same line, and is reduced to the final thickness before it is wrapped at the end of the process.
A continuous rolling line creates a continuous thin slab that progresses in a continuous process, all in one, through a coarse mill mill and then an end mill. Slab mill has a separate crushing mill and finishing factory. The plate is repeatedly passed under the same mill to obtain the final thickness.
Shows sample configurations of hot rolled aluminum plants. The configuration of rolling mills varies depending on the amount of production desired. Single-base mills are used to produce small batches of a wide range of products, while standing mills are used for mass production.
In recent years, it has become very significant to start working with single-mill mills to add rolling mills in line with growing demand to minimize initial investment and shift standing plants.
Hot rolling mills for aluminum have coil coating problems because the adhesion of aluminum powder to the surface of the coils affects the surface quality of the rolling strips. Brush rolls and other special mechanisms are installed in aluminum rolling mills as countermeasures against such a problem.
