Ladle has the function of accepting molten steel and stopping refining outside furnace. The service life of ladle directly affects ladle turnover and refractory consumption, thus affecting the smelting cost of steel mill. Taking 75t ladle as an example, the factors affecting ladle service life were analyzed, and corresponding measures were taken from the aspects of smelting conditions, ladle baking quality and ladle maintenance technology to improve the service life of ladle.
Factors affecting ladle life elements of service life
1) Smelting conditions. The longer ladle holding time, the higher refining temperature, the larger slag discharge, the lower slag basicity and the stronger slag oxidation, the faster corrosion of ladle lining material.
2) Ladle baking quality. Before the ladle is put into use online, it is necessary to stop the baking of the ladle, and the ladle refractory material is fully sintered to prevent the refractory material from falling out after the new ladle is filled with molten steel due to too fast temperature rise. In the process of ladle turnover, slow ladle turnover speed, large temperature drop and excessive heat and cooling of resistant material temperature should be avoided, which will affect the life of ladle.
3) Lining of ladle. The lining material of ladle is in direct contact with molten steel, and its material conforms to smelting condition, which can greatly add molten steel and steel slag to the corrosion of refractory materials. In addition, to improve the function of refractory materials, molten steel and steel slag can be added to the erosion and penetration of refractory materials, improve the life of refractory materials. The application of lining oxidizing coating can greatly avoid the oxidation of ladle during the baking process, and thus prolong the service life of ladle.
4) Masonry method and quality.
① Ladle masonry must add triangle joints, staggered table and other defects, in order to add molten steel or steel slag on the local serious corrosion of resistant materials, affecting the whole life of the ladle. (2) Ensure the ladle brick back seam filling material ramming, avoid in the process of reversing, joint filling material movement caused by brick pumping, steel infiltration and other accidents.
(3) The packing mouth must be compacted with steel plate to avoid the brick expansion and top-up in the process of using and inverting, and the situation of falling bricks.
④ The surface size of ladle brick is the guarantee of ladle masonry quality, and the inspection must be strictly in accordance with the quality standard.
Measures to improve the service life of ladle
2.1 Improve smelting conditions
1) After heat preservation of ladle, heat loss of molten steel is added, so as to reduce refining temperature and time and extend the service life of resistant material.
2) The amount of slag under converter is added to increase the amount of dissolved ladle magnesia carbon brick in slag, so as to improve the life of resistant material.
3) Add lime dosage appropriately, improve the basicity and viscosity of slag, reduce the penetration and melting loss of slag to refractory materials, so as to improve the life of refractory materials.
2.2 Improve ladle baking quality
1) The baking time before the ladle goes online is increased from 36h to 48h. The heating is stopped strictly in accordance with the baking curve, and the insulation time reaches the technological requirements. The temperature reaches 900℃ when the ladle goes online.
2) Increase the number of working ladle from 5 to 4 to improve the working efficiency of ladle, reduce the disposal time of ladle, add the time interval of reinjecting molten steel after ladle pouring, and prevent the shaking and firmness of ladle temperature from sudden cooling and heating.
2.3 Strengthen the lining material
1) The characteristics of converter slag is strong oxygen genicity, low alkalinity, its osmotic corrosion ability is strong, through improving the density of ladle brick to strengthen its corrosion resistance.
2) Hot and cold alternation is an important factor of ladle lining easy to damage. Improving the thermal shock resistance of ladle magnesia carbon brick is beneficial to prolong the service life of ladle.
3) Magnesium carbon brick is easy to be oxidized in the process of baking ladle due to its high carbon content, and the longer the baking time, the more serious the oxidation degree. Coating the working surface of magnesia carbon brick with an anti-oxidation coating can avoid the oxidation of ladle during baking process to a great extent, so as to prolong the service life of ladle.
2.4 Improve ladle laying method
1) Ladle bottom is changed to casting mode, on the one hand, the whole of ladle bottom is good, no brick cracks appear, on the other hand, ladle bottom can be stopped pouring maintenance in the process of ladle use and production line, avoid dismantling the ladle bottom, so as to make the bottom of infinite use, reduce the consumption of resistant materials.
2) The area where the body position is vulnerable to scouring by molten steel belongs to the weak link, and the demand for suspension strengthening can be considered from two aspects: material strengthening to improve the density and anti-scouring function of the brick; Add the thickness of brick, improve the life without changing the corrosion rate.
Perhaps considering the above two points, so that the life of the weak area and ordinary position of the resistant material synchronization, so as to improve the service life of the whole ladle.