The hot-rolled sheet of stainless steel strip is mainly hot continuous rolling, and the conventional continuous rolling mill has several layout types such as 1/2, 3/4 and full continuous. On the premise of meeting the output requirements, the single roughing stand is currently used more in China, that is, a powerful four-high roughing mill is used for 3-7 passes of reversible rolling to meet the billet requirements of finishing rolling. This arrangement can greatly shorten the length of the rough rolling zone, which is beneficial to reduce the temperature drop of the slab.
Due to the high requirements on the surface quality of stainless steel strips, the primary iron oxide scale on the surface of the slab is generally removed by high-pressure water rough descaling during the hot rolling process, which can minimize the thickness of the iron oxide scale coating.
Generally, a vertical rolling mill is arranged in front of the roughing mill in hot tandem rolling, and it 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 as-cast structure to the rolled structure to prevent edge cracking during horizontal rolling. These features are very important to avoid hot rolled edge cracking of stainless steel sheets.
Due to the narrow processing temperature range and high temperature deformation resistance of stainless steel strip, in order to reduce the temperature drop of stainless steel plate rolling during the rolling process, the method of high temperature rapid rolling and rush rolling is adopted in the rough rolling stage. The slab is rolled to the intermediate thickness in as few rolling passes as possible. Therefore, the selection of power and energy parameters of the rolling mill is larger than that of the carbon steel rolling mill of the same specification.
There is also a hot coil box process in the process, and its function is as follows. The finishing mill can not use the speed-up rolling, which can reduce the power of the main motor and the speed of the rolling mill, and can shorten the length of the rolling line and reduce the investment. Under the same conditions, the slab discharge temperature can be reduced, the heating furnace fuel can be saved, and the slab oxide scale can be reduced. When the hot coil box is coiled, a large number of secondary iron oxide scales are peeled off, which is conducive to the removal of iron oxide scales 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 widely used in domestic stainless steel hot rolling production.
There is also a finishing rolling unit. Before the finishing rolling of strip steel, high-pressure water or steam can be used to remove and purge the iron oxide scale on the surface of the intermediate billet according to carbon steel and stainless steel.
In the domestic production of stainless steel strips, a vertical roll mill is generally equipped in front of the finishing rolling unit, which plays the role of guiding and edge rolling of the rolling stock, and preventing edge cracks in the rolling stock during the finishing rolling through the edge rolling. There are generally 6 to 7 finishing rolling mills, and the selection of power parameters is similar to that of rough rolling mills in principle.
The last one is the cooling water of the rolling line and the cooling system of the strip steel, and the cooling water of the rolling line is strictly controlled in the rolling of stainless steel. The cooling method of the intermediate roller table uses the two methods of roll 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 cooling system can precisely control the coiling temperature of the stainless steel strip.
