High-quality cold-rolled steel strip has extensive and important applications in industries such as automobiles, shipbuilding, bridges, construction, aerospace, instrumentation, electronics, food packaging and household appliances. Taking the automobile industry as an example, steel, as the main raw material for automobile production, generally accounts for more than 72-88% of the materials used in automobile production, and in the variety composition of automobile steel, steel plates account for more than 50%, and it generally takes 600-800 kg of thin steel plates to manufacture a car. The production process of automobile plates is complex, the technology is difficult, and the product quality requirements are high. In particular, high-end automobile panels are called “crafts” among steel products. Therefore, high-quality cold-rolled steel strip has become an inevitable trend for future development.
The finishing production line is the key link for the strip from the steel plant to the user. It plays a pivotal role in the production of the steel industry and is the ultimate guarantee of the quality of the finished strip.
Before the project was launched, the finishing production equipment and key technologies of high-quality cold-rolled strip were mainly in the hands of several major foreign steel groups such as Germany’s SMS, Japan’s Mitsubishi, and Austria’s ANDRITZ.
The existing finishing process technology is difficult to meet the quality requirements of high-quality cold-rolled strip products. The yield rate and unit output are very low. There is no systematic process control theory, and the site is still dominated by experience control, resulting in the edge quality, plate shape and surface quality of high-quality cold-rolled strip. There is still a big gap between the international level. The inadequacy of finishing equipment and technology has seriously limited the unit’s production capacity and product quality, let alone high-quality and stable production. How to overcome the equipment and process problems of the finishing production line has become the key to solving the technical bottleneck of high-quality cold-rolled strip production.
Ideas and technical solutions to solve problems
In response to the current status of finishing equipment and technology, Yanshan University, in collaboration with China Heavy Machinery Research Institute Co., Ltd., Baoshan Iron & Steel Co., Ltd., and Tangshan Iron and Steel Group Co., Ltd., aims to achieve efficient and stable finishing production of high-quality cold-rolled plates and strips. Based on the domestic independent design and development of a complete set of high-quality cold-rolled strip finishing equipment and key production technologies, the research started from three aspects: strip edge quality control, strip shape and surface quality control, and straightening and upstream and downstream coordinated control. After more than ten years of continuous research, it has broken through the key equipment and technical bottlenecks in the finishing production of high-quality cold-rolled strip, formed independent intellectual property rights, and finally achieved efficient and stable industrialized production of high-quality cold-rolled strip.
Main innovative achievements
Development of high-quality, stable, and precise shearing process control technology. We have formulated quantitative evaluation criteria for the edge quality of plates and strips, established a database of disc shearing process parameters and a self-learning system, designed a high-precision adjustment mechanism for the overlap of disc shears, developed a comprehensive optimization setting technology for overlap, lateral clearance, and front and rear tension during shearing, and developed an automatic tracking and grinding technology for edge defects after shearing, overcoming common problems such as buckling, burrs, and unbalanced cutting ratios on the edges of plates and strips, and ensuring stable shearing and edge quality.
Development of high-precision prediction and comprehensive control technology for plate shape and surface quality in the leveling process. The influence of abnormal production such as horizontal displacement of the roll and wear of the roll on the plate shape is revealed, and the plate shape prediction and control technology based on the horizontal deflection of the working roll in the leveling process is proposed. A model for the attenuation of the surface roughness of the working roll in the leveling process is established, and the corresponding roll matching method and rolling pressure setting method are proposed, realizing the comprehensive control of the plate shape, surface quality and mechanical properties of the finishing process of high-quality cold-rolled strip.
Closed-loop control of elongation in the straightening process and upstream and downstream coordinated production process technology. A method for presetting the working parameters of the straightening machine was proposed, and a mathematical model and closed-loop control system for elongation in the straightening process were developed to ensure the shape and mechanical properties of the finished strip. The production of splitting, straightening, rewinding, and inspection was concentrated on one unit, and a finishing upstream and downstream coordinated production process based on the straightening unit was proposed, realizing efficient, coordinated, and continuous production of high-quality cold-rolled strip.
Application and Effect
The innovative results of this project have been promoted and applied in major steel mills. In the past ten years, the market share of finishing production lines has exceeded 60%, and good application effects have been achieved.
