The sliding nozzle is composed of upper and lower sliding plates and 4 refractory bricks for the upper and lower nozzles. The pouring of each ladle of molten steel must pass through the upper and lower sliding plates and the upper and lower nozzles, so they are very strict. Firstly, they must have sufficient strength at high temperatures to withstand the static pressure of molten steel, and secondly, the upper and lower sliding plates are required. The sliding surface should be very smooth, flatness should be high, to ensure tight contact, to ensure that no molten steel leaks during the pouring process, but also to be resistant to erosion, erosion, and good thermal stability, so as to withstand sudden changes in temperature. Erosion and slag erosion.
The sliding nozzle device is composed of upper and lower slide 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 skateboarding method, it can be divided into three categories:
1) Linear reciprocating;
2) Linear propulsion;
3) Rotary type.
By driving the pull rod, the sliding plate slides back and forth in a straight line. When the casting holes on the upper and lower sliding plate blocks are staggered, the upper nozzle hole is filled with drainage sand, and the steel ladle can be loaded; when the casting holes overlap, the drainage sand automatically flows out. Pouring, and the pouring speed can be controlled by the degree of overlap of the casting holes.
The sliding plate is a key component that determines the function of the sliding nozzle, and plays a role of controlling and regulating the flow of molten steel. Due to the repeated contact of the sliding plate with high-temperature molten steel (especially the casting hole), the corrosion damage is serious and the use conditions are harsh. The skateboard is required to have good performances such as high strength, corrosion resistance, and peeling resistance. During the casting process, ensure that no molten steel leaks between the skateboards. The skateboard must have the following properties:
(1) Flatness of sliding surface ≤0.05mm;
(2) High mechanical strength;
(3) Strong corrosion resistance to molten steel and molten slag;
(4) Excellent anti-oxidation performance;
(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 slide, and the lower slide and the lower nozzle. In the pouring process, generally after pouring one or two furnaces of molten steel, the lower slide plate and the nozzle must be replaced and reassembled. The sealing protection adopts fibrous or mortar gaskets to ensure the high cleanliness of the molten steel and the uniformity of the internal quality of the casting slab.
Sliding nozzle hydraulic transmission:
Large and medium-sized ladle generally use hydraulic transmission devices to solve the problem of opening and closing sliding nozzles. Hydraulic transmission is driven by liquid (common oil) as the working medium. Because the liquid has almost incompressible characteristics, when the liquid is filled with a closed container (consisting of oil pumps, pipes, valves, cylinders, etc.), the liquid is pressurized by the oil pump, and it can lose this pressure through pipes, valves, etc. It is transmitted to the oil cylinder very small, causing the oil cylinder to move and realizing hydraulic operation. Reasons for steel leakage between sliding nozzles and preventive measures
(1) The reason for the leakage of the gap between the drain and the lower sliding plate: the sliding plate is not baked after pre-installation; the cement is not evenly coated during installation, resulting in gaps; there are bricks in the cement, making it loose.
Preventive measures: The fire mud must be clean during installation, the joints must be evenly seamed, and can only be used after baking and drying.
(2) The reason for the leakage of the upper and lower slide plates: the sliding surface is not flat; the upper and lower slide plates are cracked at the edge of the injection hole; the adjustment operation is not tight or the front and back are uneven.
Preventive measures: pay attention to choosing flat skateboards. Do not use skateboards without steel hoops to prevent cracking at the edge of the injection hole; the adjustment operation should be tight and even before and after.
(3) The reason for the leakage of the gap between the upper nozzle and the upper sliding plate: the upper sliding plate and the upper sliding plate are not evenly coated with mud; the mass in the fire mud causes the male and female mouths to be insufficiently deep and disconnected; the gap is too large.
Preventive measures: the fire mud should be clean, and the joints should be evenly cracked.