The Formation of Oxide Scale on the Surface of Packaging Steel Strip

Formation of Oxide Scale on the Surface of Packaging Steel Strip
　　 When the steel is rough-rolled and runs along the roller table to the hot tandem rolling mill. The temperature is about 1000℃. At this time, a thin layer of iron oxide scale has been formed on the surface of the rolled piece. This iron oxide scale can be used in the It can be removed by hydraulic removal before the hot strip mill. When the rolled piece is rolled on the hot tandem mill, the time for the plate failure to blast between the rolling mills of each stand is extremely short, and the large reduction prevents the formation of thick scale on the surface of the strip, and the resulting The oxide film is destroyed and washed by water. Therefore, it can be said that although the temperature of the strip steel just coming out of the finished frame has a relatively high temperature of 780-850°C, the scale on the surface of the strip steel is extremely thin. After the strip steel comes out of the finished product frame, it is rolled into a strip steel coil and slowly cooled down in the back of the water spray device. During this period of time, the strip steel watch is tested and turned into an oxide scale.
　　 On the surface of the strip steel coming out of the finished frame, iron atoms first combine with oxygen atoms in the air to form the first layer of oxide. This layer of oxide may be dense Fe3O4, or sufficiently loose FeO. In the former case, the further growth process of the scale can only be carried out by the diffusion of oxygen and iron ions. In the latter case. In the air Oxygen can freely pass through the porous and loose iron oxide scale to thicken and densify the iron oxide scale. In either case, the final result is the formation of oxide scale on the surface of strip steel that we usually see.
　　 Of course, after a layer of iron oxide scale is formed on the surface of the strip steel, the diffusion of oxygen and iron ions is also hindered to a certain extent, and the thicker the iron oxide scale, the larger the barrier code for ion diffusion, resulting in iron oxide scale. The slower the speed. Therefore, the growth rate of the scale is not constant, that is, the thickness of the scale increases very quickly at the beginning, and then the increase rate of the scale of the scale becomes slower and slower with the increase of the scale of the scale. In fact, the formation of scale is particularly strong at high temperature. Generally, the higher the temperature, the faster the formation of scale. When the temperature is lower than 600°C, the rate of scale formation is very slow and almost stopped.