What Is Continuous Casting?

Continuous casting is the abbreviation of Continuous Steel Casting. In the production of various types of steel products in steel plants, there are two methods of solidification using molten steel: traditional die casting and continuous steel casting. The continuous casting technology that appeared in European and American countries in the 1950s is an advanced technology that directly casts molten steel. Compared with the traditional method, continuous casting technology has significant advantages such as greatly improving metal yield, slab quality, and energy saving.

The ladle containing the refined molten steel is transported to the rotary table. After the rotary table is rotated to the pouring position, the molten steel is injected into the tundish, and the tundish then distributes the molten steel to each crystallizer through the nozzle. The crystallizer is one of the core equipment of the continuous casting machine, which forms the casting and rapidly solidifies and crystallizes. The drawing straightening machine and the crystal vibration device work together to pull out the castings in the mold, and after cooling and electromagnetic stirring, they are cut into a certain length of slab.

The continuous casting automation control mainly includes the control technology of continuous casting machine drawing roll speed control, mold vibration frequency control, fixed-length cutting control, etc. ^[1]

Since the 1950s, the continuous casting process has been used in steel plants in Europe and the United States. This process of directly casting liquid molten steel through a continuous casting machine into a shaped steel product is compared to the traditional casting and then The rolling process greatly shortens production time and improves work efficiency. In the 1980s, continuous casting technology was gradually improved as the leading technology, and it was widely used in major steel producing countries around the world. By the early 1990s, more than 90% of the world's major steel producing countries had achieved

The horizontal continuous casting project of cast iron is a national Seventh Five-Year Plan project,

Continuous casting machine

The continuous casting machine is mainly composed of an intermediate tank, a crystallizer, a vibration mechanism, an ingot rod, a secondary cooling channel, a stretch straightening machine and a cutting machine.

Although a high degree of automation helps to produce shrink-free castings, problems can occur during the casting process if the liquid metal is not cleaned of impurities in advance. Oxidation is the main source of liquid metal impurities, and gases, slag or insoluble alloys may also be involved in liquid metal. To prevent oxidation, the metal is isolated from the atmosphere as much as possible. In the tundish, any inclusions including air bubbles, other slags or oxides, or insoluble alloys may also be trapped in the slag layer.

A major continuous casting problem is the fracture of the continuous casting slab. If the solidified metal shell is too thin, it may cause the lower metal to pull the condensing metal above after the steel billet is pulled out for a certain length, causing the molten steel to leak, and then damage other machines and cause accidents. Under normal circumstances, the fracture is due to the excessively high pull-out speed, which does not allow the solidified shell to have enough time to produce the required thickness; it may also be that the temperature of the pulled-out metal is still too high, which means that the final solidification time is much lower than the corrected value. Straight rollers and local chains break during rectification due to applied pressure. A breakthrough may also occur, such as causing a tear. If the incoming metal is too hot, it can be prevented by slowing down the pull-out speed.

Another problem that may arise is carbides, which can also be generated when steel reacts with dissolved oxygen. Because the metal is liquid, this carbonization reaction is very fast, and a large amount of high-temperature gas is generated. If the carbonization reaction occurs in the tundish or crystallizer, the oxygen element will also react to form silicon oxide or aluminum oxide. Silicon oxide or aluminum oxide may block the connecting tube between the tundish and the crystallizer, which will lead to damage to production ^[3]

The rapid development of continuous casting technology is a very noticeable trend in the development of the contemporary steel industry. The reason why continuous casting has developed rapidly is that it has greater technical and economic advantages compared to traditional steel ingot mold casting. The following aspects.
(1) Simplified production process Because continuous casting can eliminate the pre-rolling and slab-opening process, it not only saves the energy consumption of soaking furnace heating, but also shortens the cycle time from molten steel to slab forming. One of the main developments of continuous casting in recent years is the tendency to cast slabs close to the cross-section of the finished product, which will further simplify the rolling process.
(2) Improve the metal yield. The ingot mold casting yield from molten steel to slab is about 84 to 88%, while continuous casting is about 95 to 96%. Therefore, the continuous casting process can save metal 7 to 12 %, This is a considerable number. One of the important reasons why the Japanese steel industry is competitive in the world is the large-scale adoption of continuous casting in the steel industry. Since 1985, the continuous casting ratio in Japan has exceeded 90%. For the expensive special steel and stainless steel, the continuous casting method is used for casting, and its economic value is even greater. After the second steelmaking plant of Wuhan Iron and Steel Company of China replaced die casting with continuous casting, the cost per ton of slabs was reduced by about 170 yuan. Based on the annual output of 8 million tons, the annual revenue was about 1.35 billion yuan. It can be seen that improving the metal yield and simplifying the production process will obtain considerable economic benefits.
(3) Saving energy consumption According to the introduction of relevant materials, the production of 1 ton continuous casting slab can save 627 1046KJ energy compared to die casting and slab opening, which is equivalent to 21.4 35.7kg standard coal, plus the energy consumption saved by increasing the yield rate is more than 100kg Standard coal. According to China's energy consumption level, the comprehensive energy saving per ton of continuous casting slabs is about 130 kg of standard coal.
(4) Improving labor conditions, easy to realize automatic mechanization and high degree of automation of continuous casting. The continuous casting process has realized computer automatic control, which frees operators from heavy physical labor. In recent years, with the development of science and technology and the improvement of automation level, electronic computers are also used for the control of continuous casting production. Except for steel pouring and pouring operations, all are controlled by computers. For example, the slab continuous casting machine of Baosteel in China uses 5 PFU-1500 computers for on-line control. It has cutting length calculation, compression casting control, electromagnetic stirring setting, on-line mold width adjustment, quality management, Cold water control, process data collection, casting slab, tracking, finishing line selection, flame cleaning, slab printing labeling and weighing, and various report printing and other 3l control functions.
(5) Good quality of the slab. Due to the rapid cooling rate of continuous casting, continuous drawing, and controllable and stable casting conditions, the internal structure of the slab is uniform, dense, less segregated, and stable in performance. Sheets rolled with continuous casting slabs have better lateral performance than die casting, and deep drawing performance, and other performance indicators are also better than die casting. In recent years, continuous casting has been able to produce slabs with no surface defects and directly hot-rolled into steel.
Continuous steel casting is a systematic project that involves a series of processes such as steelmaking, rolling, refractories, energy, spare parts, production organization management and so on. Many years of production practice prove that: Only by establishing the idea of "continuous casting as the center, steelmaking as the basis, and equipment as the guarantee", can we better grasp the modern continuous casting technology. The adoption of continuous casting technology has changed the traditional process requirements and operations. Habits and time rhythm. This requires operators and technicians to strengthen their learning and update their knowledge in order to adapt to the development of new continuous casting technology and do a good job of technical training ^[1]

1. Horizontal continuous casting composite method of Al-Pb alloy-steel back bearing material

2, csp thin slab

1. Inspection, maintenance and repair work must be completed when the pouring is stopped.

2. For maintenance and repair work, the electrical system must be switched off, and a prohibited operation sign is hung to prevent others from closing.

3. It is forbidden to adjust, maintain and repair the cold bed area during pouring.

4. When there is any movement on the cooling bed, it is forbidden to enter the area of the cooling bed swing beam.

5. Before entering the cold bed area and after leaving the bed area, you must contact the control room to establish a contact confirmation signal.

6. Inspection, maintenance and repair of the cold bed must be carried out when the equipment is stopped.

7. When adjusting, maintaining and repairing the cold bed, the adjacent equipment must be disconnected and ensure that it is not closed.

8. When lifting the cold bed components, the sling must be checked and confirmed, and the lifting should be accurately commanded ^[3] .