As a transitional device between the ladle and the crystallizer during the continuous casting process, the tundish is not only a storage and distributor for molten steel, but also a refining container for molten steel. It is used to stabilize the steel flow and reduce the impact of the steel flow on the billet shell in the crystallizer. Ensuring that the molten steel has a reasonable flow field and a suitably long residence time in the tundish to ensure uniform temperature of the molten steel and the separation and floating of non-metallic impurities, as well as ensuring the cleanliness of the molten steel and continuous pouring of multiple furnaces, which is an important link in improving steel quality and continuous casting efficiency.
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The main tasks of the tundish are:
(1)Divert molten steel. The multi-stream continuous casting machine distributes molten steel to various crystallizers through the tundish.
(2)Steady flow. Reduce the static pressure of molten steel, maintain a stable liquid level in the tundish, and smoothly inject molten steel into the crystallizer.
(3)Store molten steel. When replacing the ladle in continuous pouring of multiple furnaces, the pulling speed is not reduced to create conditions for continuous pouring of multiple furnaces.
(4)Purify molten steel. During a long pouring time, the temperature of the molten steel is basically kept constant, which promotes the further floating of inclusions in the molten steel, prevent contact between the molten steel and the air, and avoid oxygen and nitrogen absorption.
Refractories used in the tundish can be functionally classified into three categories:
The first category is lining material, which mainly consists of insulation layer, permanent layer and working layer.
The second category is flow stabilizing components, including slag weir, slag baffle, impact pad, etc.
The third category is the flow control part, which is divided into stopper rod, sliding nozzle, sizing nozzle and submerged entry nozzle.For billet continuous casting, the core of high-efficiency continuous casting is high casting speed, which requires that the continuous operation rate and pouring speed of the continuous casting machine should be improved as far as possible on the basis of the molten steel quality meeting the requirements, so as to achieve high billet temperature and billet quality. These technical indicators put forward two requirements for the tundish refractories, one is high performance, and the other is long service life.
The composition of refractories for the inner lining of the tundish generally includes the following parts:
(1) Insulation layer(10&#;30mm),this layer is next to the tundish steel shell and is usually uses asbestos panels, insulating bricks or lightweight castables. The best effect is aluminum silicate fiber felt, which has low thermal conductivity and is easy to build.
(2)Permanent layer (100&#;200mm),this layer is in contact with the insulation layer, and generally uses clay bricks. The overall permanent lining is the most common, and the castables are generally high-aluminum or mullite self-flowing castables.
(3)Working layer(20&#;50mm),this layer is in contact with molten steel and is a key part.Insulation boards or coatings are commonly used now. The insulation board is generally made of silicon, magnesium, or magnesium olivine. The coating is made of magnesium, magnesium chromium, and magnesium calcium. The coating shall be mechanically sprayed or manually applied.
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(4)Well block,it is embedded at the bottom of the tundish, used to install the nozzle of tundish , usually made of high aluminum material.
(5)Tundish bottom working layer,the material of the bottom of the tundish is basically the same as that of the working layer. The bottom is easily damaged by the impact of molten steel and requires corrosion resistance and wear resistance. Generally, high alumina bricks or dense high alumina bricks and aluminum chromium bricks are used, as well as specially made large high-strength tar magnesium bricks. The molten steel impact part is reinforced with zircon bricks or precast blocks.
(6)The cover covers the tundish to insulate and prevent molten steel from splashing. The cover is made of clay or high-aluminum castables.
(7)Slag baffle(Weir),the baffle is built in the tundish and can be a single or a double. The material of the baffle(weir) is generally casted with refractory castables, such as high-alumina, aluminum-magnesium or magnesium, etc., which are made into precast blocks through curing, demoulding, baking and other processes.Magnesium baffles are widely used because they have good corrosion resistance, high refractory resistance, and can effectively reduce the oxygen content brought into the molten steel. Their purpose is to retain molten slag. In order to improve the cleanliness of molten steel, a molten steel filter can also be arranged on the baffle.
The End.
A tundish is an essential component of the continuous casting system in steelmaking. Located between the ladle and the casting molds, the tundish feeds molten steel to the molds at a regulated rate. Due to the temperature extremes involved, tundish refractory linings are designed to withstand thermal shock, prevent thermal loss, prevent oxidation, and resist erosion and corrosion &#; all while not contaminating the liquid steel with unwanted impurities. BassTech is a strategic supplier of performance enhancing additives for tundish refractory linings, including sodium metasilicate 9 MOL and our specialty phosphates.
Here are five interesting facts about tundish refractory linings:
On top of being lined permanently with either refractory bricks or monolithics, a tundish also has a disposable lining. The disposable lining acts as a thermal and chemical barrier that protects the permanent liner while maintaining the temperature of the molten metal, and it needs to be replaced after one or more heats of molten steel. This refractory lining, which is sprayed on between heat cycles, contains our unique phosphate binder/deflocculant system that cures with either the residual heat or ambient temperature after cold starts.
Phosphates help with strength development, dispersing other ingredients through a mix, and allowing control of set/working times. Our phosphates are also engineered to enhance flowability, prevent oxidation, prevent out-gassing and improve strength development at elevated temperatures.
Sodium Metasilicate 9 MOL is extremely stable at ambient temperature and begins releasing significant amounts of water at about 80°C, which makes it a useful ingredient as a quick binder in single component systems at relatively low temperatures. It has shown excellent success in single component blends for low temperature strength development. In addition to strength development, the water kicks off the reactions for the other additives in the refractory mix.
Aside from extending the life of the permanent tundish lining, the disposable lining allows easier removal of the tundish skull. After being removed in a process called &#;deskulling,&#; the skull can usually be cycled back into the continuous casting process. Our phosphate additives prevent oxidation from the skull without adding detrimental impurities back into the composition.
Billets, blooms, and slabs are considered semi-finished products. These are the materials used for most forms of steel work and may eventually become rails, pipes, wire, rods, or tubes.
Are you a manufacturer of tundish refractory linings? We are a strategic supplier of performance enhancing additives for tundish refractory linings. To learn more about how BassTech International can assist you, feel free to reach out to one of our tundish refractory experts.