Keyword：Ladle, magnesia carbon brick
Description：The service life of the ladle has been increased from 102 times to 201 times. This article introduces how we have significantly improved the life of the steel ladle through optimization.
Through the implementation of optimization measures, the use of steel ladles in steel mills has been gradually improved. The life of major repairs of steel ladles has increased from 102 times to the current 201 times, and the life of minor repairs of steel ladles has increased from 51 times to the current 100 times. The average erosion rate of cladding bricks decreased from 1.47 mm to 0.67 mm per time; the average erosion rate of slag line bricks decreased from 3.27 mm to 1.75 mm per time. Share the optimization measures below
First, briefly introduce the overall background of the steel mill. The main equipment includes three 1750 m3 blast furnaces, two 200 t vanadium extraction converters, three hot metal pretreatment desulfurization stations, two 200 t steelmaking converters, two 200 t double-station LF refining furnaces, and one 200 t duplex One RH refining furnace, two two-machine two-strand slab continuous casting machines. The schematic diagram of the process flow is shown in Figure 1.
Main problem: The main problem is that the slag line of the ladle is severely eroded, and accidents such as slag line piercing steel occasionally occur, and the average overhaul life of the ladle is only 102 times.
Problems and solutions
Optimization of masonry methods
The permanent lining of the 200 t ladle in the steel plant uses aluminum-calcium castables to replace the original microporous lightweight mullite castables. The working lining of the cladding wall is made of carbon-free ladle bricks. The original carbon-free ladle bricks were changed to impact-resistant aluminum-magnesium-carbon bricks with a thickness of 450 mm. The non-impact area of the bottom-covering working lining was covered with carbon-free ladle bricks, and the slag line was comprehensively built with magnesia-carbon bricks.
Improvement of ladle material
The carbon-free ladle-clad bricks for cladding walls are replaced by plate-like corundum and brown corundum, and the thermal shock resistance is improved.
35%~40% (w) of 98.5 large crystalline magnesia is added to the slag line brick to replace part of the 97 fused magnesia in the main raw material, the corrosion resistance is improved, and its service life is increased from the original 60~70 times to 100 times. ~110 times.
The material and molding process of the nozzle seat brick are improved. The central inner cavity of the nozzle block is made of chrome corundum material, and the outer wall of the seat block is formed by secondary casting of corundum castable. The life of the nozzle seat brick has been increased from 70 times to more than 100 times.
Vortex masonry near the nozzle block
The ladle nozzle block is relatively close to the cladding wall. During the steel pouring process, the molten steel at the nozzle block generates eddy currents, so that the cladding wall near the nozzle block is continuously washed by the molten steel vortex, resulting in faster erosion of the cladding wall near the nozzle block. . Judging from the residual thickness of the ladle off the assembly line, the wall of the nozzle block is the thinnest. For this reason, install 6~8 impact-resistant alumina-magnesia-carbon bricks around the nozzle block, and arrange 3~4 local bumps higher than the upper end of the block, so as to destroy the eddy current generated by the molten steel above the nozzle block.
Ladle baking process optimization
The flame length of the first-generation ladle roaster cannot reach the bottom of the ladle, resulting in low baking temperature at the bottom of the ladle. Upgrade it to a third-generation energy-saving roaster with no reversing valve and no induced draft fan.
Change of refining slagging agent
A CaO-Al2O3-SiO2-based slagging agent is used, and a small amount of NaCO3 is added to replace fluorite. Add it to the LF refining furnace for slagging, and the amount added is controlled at 0.5-1.0 kg per ton of steel.
Through the implementation of the above measures, the use of the ladle has been gradually improved. The life of the overhaul of the ladle has increased from 102 times to the current 201 times, and the life of the minor repair of the ladle has increased from 51 times to the current 100 times. The average erosion rate of cladding bricks decreased from 1.47 mm to 0.67 mm per time; the average erosion rate of slag line bricks decreased from 3.27 mm to 1.75 mm per time.