CN-121988606-A - Method for alternately using double hot rolling units for continuous casting of thin strip

CN121988606ACN 121988606 ACN121988606 ACN 121988606ACN-121988606-A

Abstract

The invention belongs to the technical field of strip casting and rolling, and relates to a double hot rolling unit system for strip continuous casting and an alternate use method thereof. The thin strip casting and rolling process comprises the steps of smelting high-temperature molten steel through a converter BOF, a VD furnace and an LF furnace, then rapidly cooling and forming through a pair of crystallization rollers rotating in opposite directions to form a casting strip, transferring the casting strip to a hot rolling unit for single rolling time through a pinch roller, rolling to form a thin gauge rolling strip, and finally transferring the thin gauge rolling strip to a coiling machine through a laminar cooling zone to be coiled into coils. The double hot rolling unit system is positioned between the pinch roll and the laminar cooling, and mainly achieves the purpose of rolling the thin strip into the target thickness. The invention mainly solves the problem of lower continuous casting furnace number of the current thin strip casting and rolling process, so that the continuous casting furnace number of the continuous casting furnace number is obviously improved, and the production line cost reduction trend is met.

Inventors

YAN XINHUA
LIU XINYUAN
FENG KONGFANG
LI NING
LI HUALONG
WU XIANLIANG
LIU YUJUN
ZHOU DONGSHENG

Assignees

张家港中美超薄带科技有限公司
江苏省沙钢钢铁研究院有限公司
江苏沙钢集团有限公司
江苏沙钢钢铁有限公司

Dates

Publication Date: 20260508
Application Date: 20260122

Claims (6)

1. A method for the alternate use of a twin hot rolling train for strip casting, said twin hot rolling train comprising a rolling mill #1 and a rolling mill # 2, the rolling mill on the side marked as the rolling mill #1 being close to the casting machine, said method essentially comprising the steps of: (1) Before casting, the No. 1 rolling mill is in a working state, the No.2 rolling mill is in a standby state, and a thin strip sequentially passes through the No. 1 rolling mill, the No.2 rolling mill and an online surface detector after casting; (2) Detecting the quality conditions of the upper surface and the lower surface of the thin strip in real time through the online surface detector, and switching the No. 2 rolling mill when the total area of the surface defects is more than or equal to 10% of the area of the thin strip; (3) The rolling mill No. 2 is switched from the standby state to the working state, and the roll gap control of the rolling mill No. 2 is consistent with that of the rolling mill No. 1; (4) And the No.1 rolling mill is switched from the working state to the standby state, and the surface quality of the thin strip is continuously detected in real time through the online surface detector after the double hot rolling mill groups are alternated until the total surface defect area is more than or equal to 10% of the area of the thin strip.
2. The method according to claim 1, characterized in that: The No. 1 rolling mill is located between the pinch roll and the laminar cooling zone and is 5-6 m away from the pinch roll, the No. 2 rolling mill is located between the pinch roll and the laminar cooling zone and is 3-4 m away from the No. 1 rolling mill and is 1-2 m away from the laminar cooling zone, and the online surface detector is located between the laminar cooling zone and the coiling machine and is 2-3 m away from the coiling machine.
3. The method according to claim 1, characterized in that: the working state refers to that the roll gap distance is 0.7-1.5 mm, the standby state refers to that the roll gap distance is more than or equal to 50mm, and the standby state rolls do not participate in rolling work.
4. The method according to claim 1, characterized in that: in the method, the roll gap of the No. 2 rolling mill is kept consistent with that of the No. 1 rolling mill for 4-8 min.
5. The method according to claim 1, characterized in that: detecting the surface quality defect of the thin belt by the online surface detector, wherein the total area of the surface defect and the area of the thin belt in the surface quality defect of the thin belt are more than or equal to 10 percent.
6. The method according to claim 5, wherein: the surface quality defects of the thin strip comprise pits, roll marks and scratches.

Description

Method for alternately using double hot rolling units for continuous casting of thin strip Technical Field The invention belongs to the technical field of strip casting and rolling, and particularly relates to a double hot rolling unit system for strip continuous casting and an alternate use method thereof. Background The thin strip continuous casting technology belongs to near-net-shape front edge forming technology and is one new technology with the highest potential in the field of continuous steel casting. The high-temperature molten steel is used as a raw material, and the high-temperature molten steel is rapidly cooled, solidified and formed by two crystallization rollers rotating in opposite directions, so that a strip with the thickness of 0.7-1.6 mm can be directly produced. The molten steel is cooled and solidified and then is transferred to a single-pass hot rolling unit through a pinch roll, and the thickness is directly controlled to be the target thickness after rolling, so that the thin strip can reach the target thickness only through single-pass rolling, the length of a production line is greatly shortened, and compared with the traditional continuous casting and rolling or the thin slab continuous casting and rolling, the length of the production line is shortened by 80-90%. However, because the molten steel is long in casting time and high in temperature (the temperature is still 1000-1300 ℃ before the thin strip enters the rolling mill), the roller is exposed to a high-temperature environment for a long time to run, and the roller can be subjected to thermal fatigue damage. The roller thermal fatigue damage is easy to generate surface cracks and gradually propagates inwards, so that the cracks can be stamped on the surface of the thin belt, and the surface of the thin belt is provided with defects such as scratches, pits and the like. The thin strip production line is characterized by producing thin products, the target thickness of the products is mainly in the range of 0.7-1.6 mm, and the rolling reduction is 30-70%. The higher rolling force of the rolls is required for high rolling reduction, i.e. the thinner the strip thickness is, the larger the rolling force of the rolling mill is. High rolling forces also amplify crack defects generated by thermal fatigue of the rolls, exacerbating crack propagation. If lubrication-free (oil) rolling is required during rolling, damage to the rolls is larger, the rolls flex and deform, and the roll gap becomes convex or edge convex, so that the thickness of the thin strip is uneven. In the process characteristics of the thin strip, only a single-frame rolling mill is used, and the rolling cannot be carried out under normal requirements when abnormal thin strips appear on the rollers, or the surface quality of the rolled thin strip is problematic, and finally the casting is stopped, so that the number of casting continuous casting furnaces is low. In the prior art, the surface quality defects of roll marks, pits and the like of the thin strip are caused by conditions of thermal fatigue, high rolling reduction force and the like, and the surface quality of the produced thin strip is judged to be inferior, so casting is stopped, and the continuous casting furnace number is difficult to promote. In addition, the continuous casting of the thin strip requires a large number of matched refractory materials for each production and use, and a batch of refractory materials needs to be replaced after casting is stopped. The improvement of the continuous casting furnace number has a direct relation to the use control of consumable materials such as refractory materials. The online surface detector is an important method for observing the surface quality of the rolled strip in real time during casting in a strip workshop, and mainly captures and identifies the surface defects of the strip through a high-precision sensor and algorithm based on optical imaging and intelligent image analysis. Compared with the smooth thin belt surface, the surface of defects such as pits, scratches and the like has uneven flatness, different scattering (reflection) of light, and different light source signals obtained by the high-precision sensor. The LED light source is used for bright field illumination, is suitable for detecting convex or concave defects such as pits and roll marks, and is suitable for detecting defects such as scratches and cracks (scattered light of the edges of the defects is enhanced, and dark area contrast is obvious) through dark field illumination of the low-angle annular light source. And (3) adopting a high-speed linear array camera to collect pictures, continuously reading data of each row by the camera when an object to be collected moves in front of the camera, and splicing the data together to form a complete two-dimensional image. The method is suitable for detecting objects in a high-speed assembly line or continuous uniform motion, and comprises