Since
stainless steel strips have high requirements on surface quality, the primary oxide scale on the surface of the slab is generally removed through high-pressure water rough descaling during the hot rolling process, which can minimize the thickness of the oxide scale covering layer.
Generally, a vertical roller mill is installed in front of the roughing mill of hot tandem rolling and is arranged close to the roughing mill. It is used to control the width and shape of the strip and at the same time change the edge of the stainless steel slab from the cast structure to the rolled structure to prevent edge cracks during horizontal rolling. These functions are very important to avoid hot rolling edge cracks of stainless steel plates.
Due to the narrow processing temperature range of stainless steel strips and the high resistance to high-temperature deformation, in order to reduce the temperature drop of stainless steel plate rolling parts during the rolling process, high-temperature fast rolling and rush rolling are used in the rough rolling stage. The slab is rolled to the intermediate thickness in as few rolling passes as possible. Therefore, the force and energy parameters of the rolling mill are larger than those of carbon steel rolling mills of the same specifications.
There is also a hot coil box process in the process, and its functions are as follows. The finishing rolling unit does not need to use increased speed rolling, which can reduce the main motor power and rolling mill speed, shorten the rolling line length, and reduce investment. Under the same circumstances, the slab exit temperature can be lowered, heating furnace fuel can be saved, and slab oxide scale can be reduced. During hot coil coiling, a large amount of secondary iron oxide scale peels off, which is beneficial to the removal of iron oxide scale and reduces the temperature difference between the head and tail of the intermediate billet and the upper and lower surfaces. Therefore, hot coil box technology is commonly used in domestic stainless steel hot rolling production.
There is also a finishing rolling unit. Before finishing strip rolling, high-pressure water or steam can be used to remove and purge the oxide scale on the surface of the intermediate billet according to carbon steel and stainless steel.
In domestic stainless steel plate and strip production, a vertical roller mill is generally equipped in front of the finishing rolling unit to guide and edge roll the rolled pieces. Edge rolling prevents edge cracks in the mid-rolled pieces after finishing rolling. The finishing rolling mill unit generally has 6 to 7 stands, and the selection of force and energy parameters is similar to the rough rolling mill unit in principle.
The last one is the rolling line cooling water and strip cooling system. The rolling line cooling water is strictly controlled during stainless steel plate rolling. The cooling methods of the middle roller table use two methods: roller body cooling and roll neck cooling, which can be controlled separately. During the rolling process, it is strictly forbidden for the roll cooling water to leak onto the surface of the strip because the laminar flow cooling system can accurately control the coiling temperature of the stainless steel strip.
