Ladle has the function of receiving molten steel and refining outside the furnace. The service life of ladle directly affects the ladle turnover rate and refractory consumption, thus affecting the smelting cost of steel mills. Taking 75t ladle as an example, this paper analyzes the factors affecting the service life of ladle, and takes corresponding measures from smelting conditions, ladle baking quality, ladle maintenance technology and other aspects to improve the service life of ladle.
1 The factors affecting ladle life factors of service life
(1) Smelting conditions
The longer the ladle is filled with steel, the higher the refining temperature, the greater the slag quantity, the lower the basicity of slag and the stronger the oxidizing property of slag, the faster the erosion of ladle lining material.
(2)Baking quality of ladle
Before the ladle is put into use, it is necessary to bake the ladle, and the refractory material of the ladle is fully sintered, so as to prevent the refractory material from falling off after the new ladle is filled with molten steel. During ladle turnover, it should be avoided that the ladle turnover speed is slow, the temperature drop is large, and the refractory temperature is overheated and supercooled, which affects the ladle life.
The lining material of ladle is in direct contact with molten steel, and its material is suitable for smelting conditions, which can greatly reduce the erosion of refractory materials by molten steel and steel slag. In addition, improving the performance index of refractories can reduce the erosion and penetration of molten steel and steel slag to refractories and prolong the service life of refractories. The use of lining oxidation coating can greatly avoid oxidation of ladle during baking, thus prolonging the service life of ladle.
(4)Masonry method and quality
A:The defects such as triangular joints and staggered joints must be reduced in ladle masonry, so as to reduce the serious erosion of local refractories caused by molten steel or steel slag and affect the overall service life of ladle.
B: Ensure that the joint filler at the back joint of ladle bricks is tamped, so as to avoid accidents such as brick drawing and steel penetration caused by the movement of joint filler in the process of backpacking.
C: The bag mouth must be compacted with steel plates to avoid brick expansion and jacking in the process of using and pouring.
D:The appearance size of ladle bricks is the guarantee of ladle masonry quality, and must be inspected in strict accordance with quality standards.
2.Measures to prolong service life of ladle
2.1 improving smelting conditions
1) Heat loss of molten steel is reduced by insulating ladle, thereby reducing refining temperature and time and prolonging service life of refractory.
2) Reduce the amount of slag discharged from converter, so as to reduce the dissolved amount of ladle magnesia-carbon bricks in slag, and thus improve the life of refractory.
3) Properly increase the amount of lime, improve the basicity and viscosity of slag, reduce the penetration and melting loss of slag to refractory, and thus improve the life of refractory.
2.2 improve ladle baking quality
1) The baking time before the ladle goes online is increased from 36h to 48h, and the temperature is increased strictly according to the baking curve, and the holding time is guaranteed to meet the technological requirements, and the temperature when the ladle goes online reaches 900℃.
2) Reduce the turnover ladle from 5 to 4, improve ladle turnover efficiency, reduce ladle processing time, reduce the time interval of pouring molten steel after ladle pouring, and prevent stable fluctuation of ladle temperature.
2.3 strengthen lining material
1) The converter slag is characterized by strong oxygenicity, low alkalinity and strong erosion ability of its permeability, so its anti-erosion ability should be strengthened by improving the compactness of ladle bricks.
2) The alternation of cold and hot is an important factor for the damage of ladle lining. Improving the thermal shock resistance of ladle magnesia-carbon brick is beneficial to prolonging the service life of ladle.
3) MgO-C brick is easy to be oxidized in the process of baking ladle because of its high carbon content, and the longer the baking time, the more serious the oxidation degree. Coating an anti-oxidation coating on the working surface of magnesia-carbon brick can greatly avoid the oxidation of ladle in the baking process, thus prolonging the service life of ladle.
2.4 improve the laying method of ladle
1) The ladle bottom is changed into pouring mode, which makes the ladle bottom have good integrity and no brick joints, and on the other hand, the ladle bottom can be poured and maintained during the ladle service and when it goes offline, so as to avoid unpacking the ladle bottom, thus enabling the ladle bottom to be used indefinitely and reducing the consumption of refractory materials.
2) The area vulnerable to molten steel erosion in the ladle body is a weak link, which needs to be strengthened. It can be considered from two aspects: strengthening the material to improve the density and anti-erosion performance of the brick; Increasing the thickness of brick can improve the life without changing the erosion rate. Or comprehensively considering the above two points, the service life of refractory in weak area and common position can be synchronized, thus improving the whole service life of ladle.