Vertical Continuous Casting

Vertical continuous casting refers to continuous cast steel in which the whole process of casting and slab solidification is carried out in a vertical state. Vertical continuous casting has the characteristics of even cooling and good solidification structure symmetry.

Development History

Vertical continuous casting is the earliest continuous casting technology used in industrial production. In 1933, S. Junghans of Germany invented mold vibration technology, which solved the problem of pulling leakage caused by the adhesion between the initial setting shell and the mold. Continuous casting entered industrial application. From the 1950s to the early 1960s, countries around the world built vertical continuous casters one after another. However, due to the high construction cost, high production efficiency, and imperfect continuous casting technology, the development speed was slow.

The world's first industrial experimental vertical continuous caster was built at the low Maor plant in Britain in 1946 to cast small section billets. The first vertical billet caster for industrial production was built at Barro steel works in the United Kingdom in 1952. The first slab caster (semi-continuous vertical caster with a slab section of 180mm × 800mm) was built in the Red October steel plant of the former Soviet Union.

China's first industrial test vertical continuous caster was built at Shanghai Iron and Steel Research Institute in 1956. The first industrial production vertical continuous caster was built in Chongqing No.3 iron and steel works in 1958, with a casting section of 170mm × 250mm。 In 1964, the arc-type continuous caster came out, and the construction of vertical continuous casters was mostly replaced by arc-type casters. However, a few vertical casters were still under construction, and even new vertical casters were built in the 1980s. The Third Steelmaking Plant of Taiyuan Iron and Steel Company of China built a semi-continuous vertical caster for casting stainless steel and alloy steel in 1985. Most of the vertical casters are still functioning, but some have been dismantled or rebuilt. The former Soviet Union had the largest number of vertical continuous casters, followed by France.

Process Principle

The whole process of casting and slab solidification is a continuous cast steel | ironmaking type that is carried out in a vertical state. A series of equipment and operations such as tundish, crystallizer, secondary cooling zone, tension leveler, cutting equipment and receiving fixed length billet for continuous casting | rolling are arranged on a vertical centerline (see Fig. 1). After the molten steel is injected into the crystallizer from the tundish, the initially solidified billet is accelerated by the secondary cooling zone, pulled out by the billet puller at the set pulling speed, cut, and then the fixed length billet enters the tipping bucket. After the tipping bucket receives the billet, the billet is placed in a horizontal state and transported out by the conveying roller table (the pit type caster has a hoist to lift the billet to the floor surface and then output it by the ground roller table), or the tipping bucket is tilted and inverted to the inclined crawler conveyor, The slab is sent to the ground by crawler conveyor and output by the ground roller table, and then pushed to the centralized cooling bed by the steel pulling (or pushing) machine.

Process Characteristics

(1) The molten steel is injected into the vertical mold from the tundish, and the large-sized inclusions and some small inclusions in the molten steel may float to the surface. When casting with mold powder, the inclusions can be absorbed by the mold powder, and the remaining inclusions in the slab are evenly distributed, so that the inclusion in the slab will not accumulate in the inner arc area during arc continuous casting.

(2) The cooling of the billet is uniform and the solidification structure is symmetrical.

(3) The billet is not affected by external forces such as bending and straightening in the solidification process and in the caster, and there will be no crack defects caused by mechanical stress in the billet. Moreover, due to the large hydrostatic pressure of steel, it is easy to solidify and feed, so vertical continuous casting is suitable for casting alloy steel and steel with high crack sensitivity.

However, the total height of the vertical continuous casting equipment is large. Because the slab solidifies in the vertical state, the total height of the equipment also increases with the increase of the section of the casting slab and the increase of the drawing speed. The longer the fixed length of the slab, the higher the height of the caster. Generally, the height of the vertical caster is twice that of the arc caster. For casting the slab of the same type of section, the arc caster is only 1 / 3 of the height of the vertical caster.

For example, the height of a large slab or square billet caster (the distance from the casting platform to the upper surface of the output roller table) is more than 30m, and the height of a vertical caster with a small cross-section generally needs to be about 20m, so the height of the plant is very high or some equipment of the caster needs to be built in the pit (the pit depth of the vertical caster in the first steel making workshop of Tangshan steel works, China is 18m).

Therefore, the capital construction work of vertical continuous casting is large, and the construction cost of the plant or pit is high. In addition, it is troublesome to transport the billet. Once the casting process breaks down, the caster can only stop working. Since the advent of arc continuous caster in the 1960s, the construction of vertical continuous caster has been basically replaced by arc caster.