November 10, 2022
In order to obtain fine and uniform ferrite grains, the process requirements are as follows:
(1) The final rolling temperature should be above A3, coiling temperature should be below A, so as to obtain uniform and equiaxed fine grain structure and high dispersion carbide phase. If the coiling temperature is high, uniform will be generated
The coarse grain structure and carbides will accumulate to a considerable extent, which is bad for the properties of steel plate.
(2) During final rolling and low-temperature coiling under A3, coarse ferrite crystals appear on the surface layer due to the deformation of ferrite, thus forming uneven grain structure. If high temperature coiling is carried out under such conditions, it can be removed
The coarse grain structure is very uneven and the surface grain is very coarse.
(3) If the final rolling temperature is lower, there will be extended ferrite grains, which will remain in the steel after low temperature coiling or form coarse crystal structure due to self-tempering recrystallization during high temperature coiling.
In addition, the raw materials used for galvanized sheet are mainly rolling slab and continuous casting slab. The thickness of slab used in hot rolling mill is generally 150~300mm, most are 200~250mm, and the thickest is 350mm. nearly
The width of the slab is larger than that of the finished product. The width of the strip is controlled by the vertical roll. The length of the strip is mainly determined by the width of the heating furnace and the weight of the slab required.
