Slide Gate Plate has a low temperature before use. When it is poured, it suddenly comes into contact with molten steel. The temperature rises instantaneously. The molten steel flows through the casting hole of the slide plate. Under the temperature of the rapid cooling of the slide plate, the edge of the cast hole is easily melted. Cracks, at the same time, radial cracks appear around the casting hole, so that the crack is likely to cause air inhalation, causing pollution to the molten steel, and at the same time, there will be steel leakage. At the same time, due to the external force exerted by the mechanism, the nozzle, etc., once the stress concentration occurs, the sliding plate may be cracked. This paper considers the causes of cracks in the ladle slide gate system and the expansion, and summarizes the methods and measures to suppress crack propagation.
Analysis of the causes of cracks
1. Cracks due to stress concentration
Such cracks are mainly fractures, cracks are large, and the damage to the skateboard is large, which seriously affects the performance of the sliding plate. The main reasons are as follows:
1) The cleaning of the mechanism sliding box is not clean: the mechanism sliding box needs to be cleaned before the replacement of the sliding plate, and the debris and residual debris such as residual steel and the side are removed. Once the cleaning is not complete, the bottom of the sliding box will be uneven, the sliding plate will be installed, and after the spring is pressed, stress concentration will be generated in the convex portion to fracture the sliding plate.
2) The installation of the water inlet is too high: the installation of the water inlet has strict requirements. Once the installation is too high, the navel of the skateboard will keep up with the skateboard, and even the skateboard will be cracked.
3) Mechanism deformation, the sliding box is not flat: Due to the long service life of the mechanism, it is affected by heat radiation and external force, which causes the mechanism to be easily deformed. The sliding plate is prone to stress concentration after contact with the bottom surface of the uneven mechanism.
2. Thermal shock cracks due to thermal stress.
Such cracks are mainly formed during the pouring process, and the 1600 ° C is directly in contact with the molten steel, and the sliding plate is subjected to a sudden change in temperature to generate thermal stress. Crack initiation, although inevitable, can be taken to inhibit crack propagation, or to change the direction of the crack and reduce the risk. There are many influencing factors.
1) When molten steel flows through the casting hole, the temperature suddenly rises, and radioactive thermal shock cracks are generated around the casting hole.
2) The cast hole is first subjected to thermal shock and expansion. The change in position is slightly smaller. When the thermal conductivity is small and the temperature gradient is large, a large thermal stress is generated at a certain distance from the casting hole of the sliding plate to cause cracks.
3) Skateboard is a non-homogeneous material, especially a composite skateboard. It is easy to cause cracks due to different expansion coefficients.
4) Mechanical constraints, the slide is heated and expanded. If there is no gap or gap between the two ends of the sliding box and the slide, it will be restricted by the side wall of the sliding box when the board expands, and the sliding plate is a brittle material, and the compressive stress is excessively cracked.