The "watermelon skin" iron oxide skin on Q345B steel plates is produced in the roughing and finishing regions and in the laminar cooling process. It may be a mixture of two times of iron oxide and three times of oxide scale. The two oxide scale is mainly produced in the rolling process of rough rolling area, which requires temperature control in the rolling process. The RT2 temperature can not be too high, otherwise it will produce too much iron oxide skin on Q345B steel plates.
By adjusting the allocation of high pressure water and phosphorus removal water in rough rolling area, the production of two times oxide scale can be suppressed by adjusting the outlet temperature of rough rolling. The outlet temperature of rough rolling is controlled at 990 ~ l010 C. Three iron oxide is produced in the finishing area of the intermediate Q345B steel billet in the temperature of 1000 DEG to 1070 DEG C, after finishing high pressure water descaling descaling, intermediate Q345B low alloy steel billet temperature drop at 40~60 DEG C, which means a lot of steel entering finishing mill in the temperature of 1000 degrees Celsius, while the final rolling temperature generally at 820~890 DEG C. Therefore in Q345B steel plates rolling process, the three time iron oxide skin is very easy to form in F1 ~ F4, which is 900~1000 degrees. Therefore, the cooling water between stands becomes very important, it will inhibit the three iron oxide production.
On the other hand, the entrance temperature of F1 frame is about 980~1020 degrees, in the actual rolling process of hot rolled Q345B steel plates, the Q345B steel temperature in F1 ~ F4 frame is above 900 degrees. The Q345B structure steel is very easy to produce magnetite and iron oxide in the region. When the temperature is below 900 DEG C, the oxide layer of the Q345B high strength steel surface is FeO, and a small amount of Fe3O4, but not Fe2O3; when the temperature is higher than 900 degrees with the increase of temperature, decrease of FeO, Fe3O4 in the Q345B steel surface oxide layer increased, while generating Fe2O3, the thickness of the oxide layer become thicker.
Just like you, 70% customers choose long-term cooperation with BBN steel not only for our good product and service quality, good reputation in the international market, but also for our experienced one-stop raw material supply and further steel processing!
