Difficulties in rolling of thin gauge hot rolled products and countermeasures
- Taking the thin gauge container plate SPA-H (thickness ≤2.0mm) as an example, the rolling characteristics are introduced:
(1) The thickness of the container board with thickness ≤ 2.0mm has an order, but the order of the intermediate transition specification (between 2.9 and 2.0mm) is basically not. Therefore, in order to reduce the unplanned product as much as possible, it is basically SS400 or Cold-rolled base material SPHC as a transition material, the problems brought by it are due to the large difference in steel grades and specifications, the accuracy of secondary setting and the unsuitable leveling value, etc., which affect the rolling process of thin gauge container plates. Wearing belt stability, head shape control, affecting the thinning stability of the container board;
(2) When rolling thin gauge container plates, due to the presence of Cu in the chemical composition, the process temperature drop is large, and the rolling vibration is relatively strong, especially F2—F4. As the temperature drop increases, the tail vibration is very obvious. Obvious shock marks are observed, which is not conducive to the plate type control of the tail of the steel strip. In serious cases, on-site accidents such as tail-flicking are prone to occur, which is not conducive to rolling thinning.
- What are the precautions for rolling hot-rolled products? Specific attention should also be paid to the rolling process:
(1) When rolling thick gauge transition materials, it is necessary to concentrate and finely adjust. When rolling to SPA-H of 2.9mm specification, the horizontal value and the strip head and tail state are relatively stable, which is 1.9mm and 1.6mm. SPA-H provides favorable conditions;
(2) During the rolling process, the shape of the strip should be observed at any time. It is found that the bilateral waves and the medium waves should be intervened in time, and the changes of the value of the bending rolls and the rolling rolls should be paid attention to at the same time, and the relatively stable rolling rhythm should be maintained to promote the board. Shape faster self-learning, paving the way for thinning;
(3) When rolling the first 1.9mm/1.6mm SPA-H, the speed of the belt is limited to about 10.0-100.8m/s to prevent the belt from flying too fast and the head is flying. And the automatic thickness control (AGC) of the head is cancelled, and the rolling state is unstable due to the large deviation of the head thickness setting;
(4) In the process of thinning, the deceleration rate of the tail should be increased to 0.3-0.6 m/s/s to prevent the tail from being thrown too fast. After the rolling is stabilized, the belting speed can be appropriately increased to about 11 m/s and the tail deceleration rate can be appropriately reduced, thereby reducing the rolling time of the strip and increasing the temperature of the tail portion, which is favorable for rolling stability; when the thin gauge is rolled due to the tail temperature Low and in a lost state, the AGC should be canceled before the steel is thrown to prevent the roll gap from being adjusted to cause the tail;
(5) When the rolling state is stable, try to use a set of horizontal values for the head and tail, and try to keep the tail in the middle when throwing the tail. When the condition is not good, the tail can be biased to one side for pre-adjustment of the subsequent rack.