There is an increasing demand for higher service life of the slide gate system for higher production efficiency and more economical operation. Therefore, a new generation slide gate system is to be developed to extend the service life of the slide gate plate to achieve better production capability. The conventional slide gate system features a three-plate system, a well block, top nozzle, and a collector nozzle. The primary function of the ladle slide gate system is to control the flow of the liquid steel from the ladle to the tundish. It has been observed that the life of slide gate plates is the bottleneck which accounts for inferior performance of the overall slide gate refractory system. The performance of the slide gate plate is dependent on many factors such as refractory material, operating conditions, steel grade and slide gate mechanism.
A new generation slide gate plate system had been developed which consists of a two-plate linear, hydraulically driven gate. The gate valves are designed for small, medium and large capacity ladles. The new ladle slide gate being simple and robust offers higher stroke length, plate crack control, higher face pressure, and lower nitrogen pick-up.
It comprises of the one-piece well block and a one-piece upper nozzle, unlike the conventional. The fixed and sliding refractory plates are identical in terms of shape and size. The steel-encased collector nozzle is detachable. The innovative shape is based on 3D stress modeling and finite element analysis studies. Internal stress distribution has been optimized by the octagonal shape, hot banding and plate clamping. The forces act on the plate from four corners which eliminate crack formation in the stroke area. It has been observed that all cracks are oblique and do not lie on the stroke. The automatic face pressure loading of the gate, cuts down the manual effort as well. This type of ladle slide gate system provides much more safety compared to other gates due to its higher stroke length. Thus increased stroke length provides better operational safety and improved plate life. The quality of steel is (nitrogen pick-up is reduced) further improved by the unique pressure distribution in the collector nozzle and the tightness of the mechanism.
The refractory material used in the slide gate plate must be compatible with the chemistry of cast steel grade. The calcium concentration in the steel is important when selection of the slide plate material is made. The material of the slide plate is also dependent on the sliding stroke length of the plate. For smaller plates, magnesia-based materials are preferred whereas, and for bigger plates, alumina-based materials are used. The slide plate is subjected to high throttling as well. Therefore, a suitable plate material with a suitable bonding system has to carefully chosen keeping in mind the various factors involved in the process.
IFGL Refractories LTD has developed FF sliding gate system which offers faster circulation of ladles, lower number of ladles required, higher spring life and higher plate life. Trials done with FF90 and FF60 have shown promising results. The plate surface was found to be clean and the bore of the plate was also perfectly circular. IFGL manufactures the following types of bonding systems for superior plate performance in any type of casters:
– metal bond – most advanced bonding system with suitable heat treatment,
– lightly burnt metal bond – most advanced bonding system with specifically designed firing,
– carbon bond – most conventional bonding system with proper firing,
– ceramic bond – most stable bonding system with solid-state sintering at high temperature.
