Description: The slide plate is a key component that determines the function of the sliding nozzle, and plays a role in controlling and regulating the flow of molten steel. Due to the repeated contact of the slide plate with high-temperature molten steel (especially the part of the casting hole), the corrosion is serious and the service conditions are harsh. The slides are required to have good properties such as high strength, corrosion resistance, and peeling resistance, and ensure that no molten steel leaks between the slides during the pouring process.
Keyword: slide gate plate nozzle
Refractories for sliding nozzles: well block，upper&lower slide gate plate，upper&lower nozzle，filling sand.
The sliding nozzle device is composed of upper and lower plates made of refractory materials and a mechanical drive structure, and is installed outside the bottom of the ladle. The upper slide is fixed and the lower slide is movable. According to the way of skateboarding, it can be divided into three categories:
1) Linear reciprocating type;
2) Linear propulsion type;
3) rotary type.
By driving the pull rod, the slide plate reciprocates in a straight line. When the casting holes on the upper and lower plate bricks are staggered, the drainage sand is filled in the upper nozzle hole, and the ladle can be filled with steel; when the casting holes overlap, the drainage sand flows out automatically, and the Pouring, and the pouring speed can be controlled by the overlapping degree of the casting holes.
Slide gate plate
The slide plate is a key component that determines the function of the sliding nozzle, and plays a role in controlling and regulating the flow of molten steel. Due to the repeated contact of the slide plate with high-temperature molten steel (especially the part of the casting hole), the corrosion is serious and the service conditions are harsh. The skateboard is required to have good properties such as high strength, corrosion resistance, and peeling resistance. During the pouring process, it is ensured that no molten steel leaks between the skateboards. The skateboard must have the following properties:
(1) Smoothness of sliding surface ≤0.05mm;
(2) High mechanical strength;
(3) Strong corrosion resistance of molten steel and slag;
(4) Excellent oxidation resistance;
(5) Good thermal shock stability.
The sealing protection of the ladle sliding nozzle is mainly at the connection between the upper nozzle and the upper sliding plate, and the lower plate and the lower nozzle. During the pouring process, generally after pouring one or two furnaces of molten steel, the lower plate and the nozzle must be replaced and reassembled. Fiber or clay gaskets are used for sealing protection to ensure the high cleanliness of molten steel and the uniformity of the internal quality of the slab.
firing of slide gate plate
In the firing of aluminum-carbon slides, not only the organic binder is carbonized and coked during firing, forming a carbon bond in the brick, but also the additives, such as metal silicon, can combine with carbon to form SiC when reduced and fired at <1300 °C , and a ceramic bond is formed in the brick body. Therefore, there is a dual bonding system of ceramic bonding and carbon bonding in the fired aluminum-carbon slide plate. It significantly improves the strength of the skateboard, and even after the carbon is burned out in use, it can maintain sufficient residual strength due to its ceramic bonding system. After the skateboard is fired, it is generally immersed in oil. Vertical or horizontal vacuum-pressurized oil immersion devices are generally used in oil immersion. After the slide plate is preheated, put it into the oil immersion tank, and evacuate it to a vacuum degree above 650mmHg column, introduce heated tar or asphalt, and pressurize the oil to a pressure of 8~16kgf/cm2 or higher to make the tar or asphalt is sucked into the open air pores of the skateboard. The casting hole in the slide plate can be made during molding, or it can be formed into a non-porous integral board first, and then drilled to obtain. Most people think that drilling is good for improving the quality of the skateboard. In addition, wrapping the hoop around the skateboard with a thin iron sheet is considered an important measure to ensure the safe use of the skateboard. It can prevent the skateboard from breaking during use, and because the metal hoop is wrapped very tightly, it has limitations. The effect of crack propagation, especially crack opening, in a material.
Non-firing slide gate plate
It is a non-firing aluminum-carbon slide plate with relatively simple process, low cost and good use effect. The ingredients of this kind of skateboard are similar to those of fired skateboards. Raw materials such as plate corundum, mullite, corundum, flake graphite, silicon carbide and silicon powder are used, and phenolic resin is added as a binder. After kneading, molding, heat treatment and mechanical processing That is the finished product. Compared with the fired aluminum-carbon slide plate, the non-burned slide plate does not need firing, oil immersion and carbonization heat treatment in the manufacture, which simplifies the production process, but the strength is low and the porosity is slightly higher. Practice has proved that the non-burning slide plate has a good effect on the ladle of medium-sized converters and electric furnaces, and some even exceed the burning oil-immersed slide plate.
How to install and use the slide gate plate
- The cement between the skateboard and the nozzle should have a moderate amount and hardness, so that the joints are uniform and the strength is appropriate.
- Increase the self-opening rate of the nozzle, avoid burning oxygen and drainage, and reduce the oxidation and hole expansion of the slide.
- Prevent the phenomenon of “slag dropping” at the nozzle when the molten steel is poured, and reduce the erosion of the slag on the slide surface.
- Continuous casting should save stroke when pouring steel flow control and closing operation after pouring.
- Oxygen blowing removes residual steel, and the residue prevents improper operation from causing excessive reaming of the slide plate.
Skateboard damage factors
1) Cracking and chipping around the casting hole due to thermal shock. Micro-cracks and damage must be produced when the high-temperature molten steel is in contact with the cold refractory material initially. Therefore, it is extremely important to improve the thermal shock stability of the slide material.
2) Erosion and erosion of molten steel and slag. The erosion and erosion resistance of a skateboard will significantly affect its lifespan. Corrosion mainly refers to the reaction between Mn, MnO, FeO, CaO and other components in molten steel and the slide material. SiO2 in the material is easy to react, and reducing the content of SiO2 is beneficial to resist corrosion. The carbon in the product can prevent the intrusion and reaction of corrosive oxides, and the oxidation prevention of carbon is the main thing at this time.
3) The wear of the slide plate material during sliding, especially when the slide plate has a certain damage, the solidified steel will cause the wear of the slide plate when sliding. Therefore, the strength of the skateboard should be improved. In addition, it is necessary to maintain a smooth surface with low porosity to reduce the penetration and penetration of molten steel, and use tar and asphalt impregnation to improve surface lubricity and keep the surface smooth.