Slide Gate Plate

The slide gate plate like the stopper rod functions to control the metal flow from the tundish to the mold. The slide gate mechanism consists of an upper nozzle placed inside the well block, top plate, sliding middle plate, and bottom plate essentially with a collector nozzle for placement of the submerged entry nozzle. The bore diameter varies from 40 to 50 mm depending on the throughput required. The system is sealed with the help of argon (provision for argon sealing is provided on the bottom and top plates which also serves for the cooling of the plates). The housing is provided with a spring to keep the plates under compression. Many tundish slide-gate systems require air cooling for the springs that supply sealing force to the plates. A glass fiber rope is added which acts as a mechanical seal between the main frame and the top plate.

The plates in contact with steel reaches the steel temperature. The temperature is very high from the refractory point of view and very high-temperature material is preferred. The thermal cycling for the working lining is considerably high. The lower plate experiences greater shock being in the open air and when the gate is opened and steel flows through it. The thermal shock is accentuated by the presence of cold argon, primarily used for cooling and sealing induces thermal stress when it comes in contact with the hot refractory. The abrasion is dependent on the throughput of steel and the size of the bore. The size of the bore is important as far as the abrasion is concerned. When the bore diameter is large then the overlap of the will be small leading to more turbulence and force generation on the lower plate. But when the overlap is more when the bore size is small it becomes harder to control metal flow or compensate for any chocking in the nozzle. The recommended overlap is 50 % for the desired output. Additionally, the movement of plates causes further wear which is not the case for the tundish upper nozzle. The applied stress is high for the plates. They need to be kept under the action of compressive stress due to the need to prevent metal leaking from the plate gap and prevent propagation of cracks. The presence of argon cooling and sealing puts additional stress on the plate.

Wear by dissolution depends on the chemical compatibility of the slags with bricks. The Ca vapour attack is a major issue when casting special grades of steel containing Ca which is in added to modify flow inclusions. When Ca is present is present in the steel and there is overlap of steel plates the calcium gets converted to Ca vapour and reacts in an aggressive manner due to the presence of alumina in the plates. This causes severe wear especially when the concentration of Ca crosses 40 ppm. The wear is in the shape of horse shoe due to the shape it attains after service. MgO or MgC can be alternate solution but it suffers from thermal shock/spalling due to the expansion rate and the stress. Penetration is caused by low viscosity metal/ slag or highly wetting metal/slag penetrating into porous refractories. Oxygen lancing is generally not done and the chance of low viscosity slag formation is rare.

The applied stress is high for the plates. They need to be kept under the action of compressive stress due to the need to prevent metal leaking from the plate gap and prevent propagation of cracks. The presence of argon cooling and sealing puts additional stress on the plate. Spalling of the penetrated zones- The application of applies stress along with abrasion from metal flow, thermal stress due to cold argon flow, corrosion by Ca vapor reduces the life of the plates abruptly. The slide gate plate is made up of alumina- carbon mix of 20-25% C (94% graphite) and 70-75 % alumina (tabular fused alumina with mullite additions). Sometimes 0-5% Zirconia is added. Antioxidants like Al, Si is added to protect the carbon. The material used can be alumina or alumina spinel or pure magnesia or alumina carbon mix with zirconia. High purity material are normally preferred because the material has to sustain really high temperatures. The top nozzle is the key wear area and contains zirconia or spinel or magnesia if high calcium grades are cast. The body generally consists of single material depending on the grade mix.

The demand for high-performance shaped refractories has increased in recent years, primarily to changing steel-making trends. Refractories are frequently utilized in continuous steel casting. Because of their superior corrosion resistance and thermal shock resistance, these refractories are ideal for the production of slide plates. Refractories also have strong flexural and compressive strength, moderate thermal expansion, high thermal conductivity, low modulus of elasticity, and resistance to molten metal and slag.

In the steelmaking process, one of the most significant refractories for continuous steel casting is the slide gate plate, which is used for precise flow control and safety. Slide gate plates, as indicated in the diagram below, regulate the flow of steel from the steel ladle to the tundish. Because they come into touch with hot liquid steel, the refractories used for slide plates should have higher hot strength qualities. Slide gate plate refractories are utilized in ladles and tundishes where they are subjected to thermal stress and physical abrasion from molten metal and slag. As a result, the slide gate plate must be resistant to thermal shock as well as corrosion. The structure of slide gate plate refractories determines the capacity and cost of steel production. The slide gate plate can be manufactured of alumina/graphite or magnesia/graphite, depending on the steel production requirements. In recent years, alumina/carbon refractories have become increasingly popular in order to avoid fuming caused by pitch, which was previously utilized in the plate, and to improve durability and service environment. The downside of alumina/graphite is that it is eroded quickly by ‘Ca’ treated steel and strong oxygen contacts. Basic materials have better corrosion resistance than neutral metals, and their corrosion resistance varies depending on the steel grade.

However, due to their high thermal expansion coefficient, neutral metals have reduced thermal spalling resistance. When high-temperature fluids, such as molten metal, flow through the nozzle of a slide gate plate, a large temperature difference occurs between the inside and outer parts of the slide gate plate that are away from the nozzle hole, causing thermal shock to some of the materials that make up these parts. As a result, the gate plate device is made of refractory material with strong thermal shock resistance but low fineness.

The slide gate nozzle for receiving a melt of special steel, notably molten steel deoxidized with ‘Ca’ alloy, is made of a zirconia-based material, which lacks stability in spalling resistance and so does not guarantee sufficient durability. In steel casting operations, refractories are commonly utilized. The so-called functional components, such as submerged entry nozzles, mono-block stoppers, and ladle shrouds, are the most basic members of this refractory product group, which are utilized in continuous steel casting.

Prevent the occurrence of ‘slag going through’ phenomenon during casting. Pay attention to save the stroke when the continuous casting is controlled and the closing operation is completed. Prevent improper operation of nozzle cleaning which could cause the expansion of the casting hole to be too large. After cleaning the nozzle and removing the scrap of the colletor nozzle, carefully check the erosion of the three joints and the sliding surface of the sliding nozzle from the casting hole while moving the slide gate plate. Stop using when the joint erosion is obvious or the sliding surface is obviously rough.

While pushing and pulling the slide gate plate in the whole process, check the matching condition of the sliding surface of the upper and lower slide gate plates from outside the mechanism to determine whether the mechanism and the spring work normally. If there is a gap between the sliding surfaces or the sliding speed of the lower slide gate plate is too fast or too slow, etc., stop using.

Factory established in 1984, International business department established in 2010. Factory with 10000 m2 area, 120 employees including 20 professional engineers. CH REFRACTORIES is professional manufacturer of fire bricks, Mortar, Pre-cast, Pre shape, Insulation products, Castable, Functional Products for Iron & Steel, Cement, Glass, Power & Petrochemical Industries. Moreover, CH REFRACTORIES also manufacturing and exporting refractory cement A600 A700 A900 CA70, Bauxite and other refractories raw material to all of the world.