Hot rolling process steps of 430 stainless steel
(1) Roll grinder process optimization. By changing the grinding wheel model, the grinder control program was improved, the grinding amount of the grinder passes was reduced, and the surface finish of the roll was greatly improved.
(2) Temperature optimization at each stage of hot rolling. Due to the wrinkle characteristics of 430 stainless steel, the suitable processing temperature is 900-1100℃, and the heating temperature should be controlled at 1150℃. In order not to affect the performance of the cold rolled plate, the rough rolling outlet temperature should be increased as much as possible without increasing the heating temperature. After on-site debugging tests, the roller conveyor speed was improved, the rough rolling speed control was improved, the rough rolling outlet temperature was increased by more than 20°C, and the finishing rolling opening temperature was increased. At the same time, it is determined according to the test conditions that the final rolling temperature is controlled at 800-880°C.
(3) The descaling system is optimized to reduce roll surface wear and rolling adhesion. From the conventional point of view of hot rolling, increasing the descaling intensity and the number of descaling passes is beneficial to removing the iron oxide scale produced during the heating and rolling processes on the strip surface, and can minimize the thickness of the iron oxide scale covering layer. It has always been used The best process is to increase the descaling intensity as much as possible during the production of ferritic stainless steel. However, during the on-site tracking process, it was found that because the entrance speed of the finishing rolling is very slow, less than 1 ms, it takes more than 1 minute to complete the entire slab rolling. Therefore, the temperature drop at the tail end of the rough rolling slab is particularly large during the finishing rolling process. The temperature drop caused by scale water is even greater. On-site observation found that when the tail 10m of the strip entered the finishing mill, there were black marks on the edge surface. This phenomenon caused serious damage to the roll surface during the rolling process. Through comparative tests of finishing rolling without descaling, it was determined that the process of 430 production without finishing rolling and descaling reduces the temperature drop on the surface of the strip. At the same time, during the finishing rolling process, a thin oxide layer adheres to the surface of the strip to separate the strip from the strip. The rolls are in direct contact, and the oxide layer plays a lubricating role to a certain extent, thus protecting the rolls and reducing roll surface damage and rolling adhesion, thus improving the surface quality of the strip to a great extent.
(4) Optimize the usage of process cooling water to ensure uniform distribution of the thickness of the oxide layer on the surface of the strip. Improve the water cutting effect of the rolling mill water cutting plate by strengthening the water management of the rolling line rollers, closing the iron scale to inhibit water, and reducing the amount of roll cooling water. Minimize the contact between water and the surface of the strip to maintain a certain thickness of the oxide layer on the surface of the strip and uniform coverage of the surface of the strip, thereby reducing the surface roughness of the strip and improving the roll bonding problem.
(5) Optimization of rough rolling feed thickness. Reducing the feed thickness of rough rolling can effectively reduce the load on each stand of finishing rolling, and the improvement of the surface quality of the strip is also very obvious. However, due to design reasons, the requirements for the weight of the continuous cast billet, and the length limitations of the rear roller table of the roughing mill, the roughing feed thickness has only a small range of variation. In daily production, the billet weight is relatively large, so the rough rolling feed thickness of different finished product specifications is classified and controlled, so that the intermediate billet feed thickness is reduced from the previous 40m to 30-35mm.
(6) Improve the load distribution of finishing rolling and improve the control system. In view of the situation that the front-end stand of finishing rolling is easy to stick and has a large amount of wear, combined with the fact that the deformation resistance of ferrite stainless steel is small, and the deformation rate of the rear-end stand still has a certain increase margin, the 430 stainless steel L control model is optimized and adjusted to limit it. The maximum deformation rate of the front-section frame was increased to increase the load of the rear-section frame. After multiple adjustment tests, the load distribution plan was finally determined.