The crystallizer for the billet caster is an important part of the caster, and it is a bottomless ingot mold with forced water cooling. It is called the "heart" of continuous casting equipment. The continuous casting mold is one of the most important pieces of equipment of the billet caster, and its operation condition directly affects the productivity of the continuous casting machine and the quality of the slab.
The crystallizer for the billet caster is basically composed of a frame, water tank and copper plate (back plate and copper plate), adjustment system (adjustment device, reducer, etc.), lubrication system (oil pipeline), cooling system, spraying, and other equipment.
1. Function of Crystallizer:
(1) Gradually solidify the molten steel into the billet shell of the required specification and shape;
(2) Through the oscillation of the crystallizer, the billet shell can be separated from the mold wall without being pulled off and breakout;
(3) By adjusting the parameters of the mold, the billet is free from defects such as square off, bulge, and crack;
(4) To ensure the uniform and stable formation of the shell of the billet caster.
2. Type of Crystallizer:
(1) The types of crystallizers can be divided into straight and arc shapes according to their inner wall shapes.
1) Straight mold. The inner wall of the straight crystallizer is vertical along the moving direction of the shell, so the thermal conductivity is good and the shell is cooled evenly. This type of mold is also conducive to improving the quality of the shell and the casting speed. The structure is simple, and it is easy to manufacture, install and debug; The inclusions are uniformly distributed; However, the slab is easy to produce bending cracks, which increases the height and investment of the billet caster. Straight mold is used for vertical, vertical bending, and straight arc billet caster.
2) Arc crystallizer. The inner wall of the arc mold is circular along the moving direction of the billet shell, so the billet is not easy to produce bending cracks, but the thermal conductivity is worse than that of straight mold; The inclusions are unevenly distributed and tend to the inner arc side of the shell. Arc mold is used for full arc and oval billet caster.
(2) Evaporative crystallizer and cooling crystallizer can be divided according to the method of obtaining a supersaturated state of solution; According to the flow mode, it can be divided into mother liquor circulating crystallizer and crystal slurry (i.e. the mixture of mother liquor and a crystal) circulating crystallizer; According to the operation mode, it can be divided into continuous crystallizer and intermittent crystallizer.
In the continuous steel casting process, the fluid flow characteristics in the crystallizer are not only related to the heat transfer of the mold and the floating of inclusions, but also closely related to the surface and internal quality of the slab. An unreasonable flow field will cause excessive surface flow velocity, intensified meniscus turbulence, slag entrapment, or excessive impact on the solidified shell, making inclusions or bubbles easy to be captured by the solidified shell, etc., which will cause a series of accidents affecting the smooth running of continuous casting and the quality of the slab.
3. Development History of Billet Caster
In the middle of the 1980s, the German SMS Company published the test results of successfully casting thin slabs with funnel mold. This breakthrough has caused great vibration in the world steel industry Thin slab continuous casting and direct rolling technology have achieved rapid development, which has a great tendency to gradually replace the traditional tropical production process. Metallurgical workers in various countries, especially those famous continuous casting equipment manufacturing companies, are urgently required to develop thin slab continuous casting technology. Strive to achieve a new breakthrough in order to develop its own thin slab continuous casting has been rolling and twisting agriculture. It is in this fierce market competition situation that a variety of thin slab continuous casting crystallizers appear.
Since the industrialization of continuous casting in the 1950s, remarkable development has been made. On the basis of the introduction, digestion, and transplantation, China's continuous casting technology has also made great progress, and many continuous casters have realized localization.
4. Position and Influence in the Industrial Chain
The crystallizer is in the middle of the industrial chain and belongs to the consumables in the continuous casting production of steel plants. In recent years, with the development and promotion of continuous casting technology and equipment, China's continuous casting billet output has been increasing. According to the division of continuous casting slab section, the output of square billet and slab is the largest in China, accounting for about 90% of the total output of continuous casting slab (including mold casting ingot).
At present, China's continuous casters are mainly slab and square billet casters, and various continuous casters, including large-sized round billet continuous casters and extra thick slab continuous casters, have basically achieved independent research, development, design, and manufacturing. In addition, China has also developed a number of continuous casting technical equipment with independent intellectual property rights, such as ladle slag detection, electromagnetic stirring, dynamic soft reduction, automatic mold level control, etc., which has greatly improved the control level of China's continuous casting process and the quality of continuous casting billets while reducing investment costs.
With the continuous emergence of new continuous casting technologies, relevant units should improve and promote the application of efficient slab continuous casting technology, hot charging and hot delivery technology of continuous casting slabs, accelerate the research and development of new near net shape continuous casting technology, enhance the international competitiveness of China's steel engineering technology, and promote the transformation from steel product export to iron steel technology and equipment export.
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