Continuous casting billets (CCB) have become an important intermediary form of steel for later rolling and forming. The expansion of the continuous casting plan and the improvement of quality will further promote the development of the steel industry. However, due to the characteristics of continuous casting, it is still a technical problem in continuous casting production. Low-ratio structure refers to the decrease in the ratio of wall thickness to sectional area, making the wall structure thinner and slender. This kind of structure of steel billets not only reduces production costs, but also improves the quality of rolling products and provides advantages for the later stamping and forging processes.
There are three main ways to vary the low-ratio structure of continuous casting billets:
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1) Modifying the diameter of the tundish and the exiting nozzle can effectively control the wall thickness of the billet. Under the same conditions, the thicker the walls, the lower the ratio of wall thickness to sectional area.
2) The shape of the tundish has a great influence on the wall thickness of the billet. When the inside diameter of the tundish is larger than that of the billet, a conical tundish should be used. Compared with the round tundish, the conical tundish can reduce the wall thickness of the billet and improve the ratio of wall thickness to sectional area.
3) The composition of steel can also change the low-ratio structure of steel billets. By adjusting the composition of steel, the wall thickness of the steel can be increased or decreased accordingly.
In addition to the above methods, the low-ratio structure of continuous casting billets can also be adjusted by controlling the speed of the launder. It is necessary to ensure the coherence of speed between the mold and the launder, and the speed of the launder should be lower than that of the mold in order to better control the wall thickness of the billet.
In summary, by selecting the special chemical type quality, improving the design parameters of tundish, controlling the speed of launder and nozzle, and selecting the appropriate pouring ratio, the ratio of wall thickness to sectional area of the continuous casting billets can be adjusted. This not only helps to improve the ability of continuous casting plan to produce low-ratio structure steel billets, but also improves the quality of rolled products and provides advantages for the later processing process.
