Factors Affecting LRF Service Life

1.1 Steel smelting：Proper Tapping Temperature

Too high tapping temperature will seriously erode the inner wall working layer. Too low tapping temperature will prolong the refining time. The stagnation time of the molten steel is too long, which also causes severe erosion and mechanical damage. The iron oxide content should be appropriate. If the iron oxide content is too high, there will be a strong chemical reaction with the lining of the molten steel tank refractory material, causing corrosion damage. Maintain proper slag alkalinity, the smaller the slag alkalinity, the more severe the erosion of the working lining of the steel molten steel tank. Correctly control the position of the steel ladle when tapping, to avoid the steel flow hitting the cladding wall, causing serious erosion of the slag bread wall.

1.2 Design of LRF Masonry

-Choose the thickness and material of the sidewall according to the erosion of different areas;

-Choose the location of the bottom porous plug and the nozzle reasonably to avoid excessive erosion of the molten steel on the sidewall.

1.3 Quality of LRF Masonry

Repair the damaged parts after the ladle goes off line, and clean the residual steel residues lined in the LRF. Fill or repair the gaps and pits caused by molten steel scouring and mechanical damage. The baking method and baking time of the ladle lining should be reasonable used.

2.1 Improvement of LRF Fixed Repair Mode

Corundum non-carbon bricks are used for the 300t ladle lining of refractory lining and the cladding working layer of Shougang Jingtang Company, and the low-magnesia carbon bricks are used for the slag line working layer, and the designed service life is 120 times.

The fixed repair mode of the ladle mainly considers the matching of the air-permeable brick, the nozzle brick and the slag line brick and the wall brick. The specific fixed repair mode is shown in Table 1. The stable fixed repair mode can effectively reduce ladle safety hazards and abnormal off-line, speed up the ladle turnover and use, ensure the cleanliness of the molten steel and the stability of the molten steel composition, and can also reduce the ladle turnover the impact of slow and abnormal offline production on steel production.

2.2 Improvement of LRF Masonry Process

The masonry process has a great influence on the online safe use of the ladle and the improvement of the service life. The 300t ladle work lining was originally designed with vertical brick-type masonry. The ladle is prone to cracks, accelerated erosion and flaking during use and other issues.

There are large potential safety hazards in the use of the LRF, the number of abnormal off-line is more, and the amount of small repairs is large, resulting in large consumption of refractory materials, slow ladle turnover rate, and steelmaking output has not been improved. After redesigning, the ladle work lining was changed to flat brick-type masonry. The frequency of cracks during the online use of the LRF decreased, the safety performance of the ladle was significantly improved, and the number of abnormal ladle off-line and the amount of refractory materials were greatly reduced. When constructing a ladle, the ladle maintenance personnel require careful operation and accurate judgment.

2.3 Improvement of LRF Baking System

(1) Standardize the blowing operation of bottom blowing bricks

A special bottom-blowing brick blowing gas test device is adopted to determine the bottom-blowing brick blowing status by the argon press flow of the ladle bottom-blowing brick, to avoid the excessive erosion of the bottom-blowing brick to cause the ladle to go offline abnormally and reduce the service life of the LRF .

(2) Standard processing of LRF operation

To avoid the abnormal ladle off-line caused by the damage to the ladle brick due to the excessive LRF edge after processing, the LRF edge must be processed in time.

Specific requirements: when the width of the inner ladle of the ladle is ≥200mm, and the external slag of the ladle is higher than the height of the ≥100mm, it must be organized in time; after the operation of the ladle, observe whether the brick along the ladle is loose or falling off In case of any problems, notify the contractor in time for key inspection.

2.3 Strengthen the Operation Control of the LRF Use Process

Temperature is an important indicator for smelting steel. LRF baking is an important method to reduce the temperature drop of molten steel tapping and transportation. The reasonable ladle baking temperature can reduce the heat dissipation of the ladle and reduce the impact on the molten steel tapping temperature. But too much baking not only wastes gas, but also has a great impact on the life of refractory materials.

(1) Preheating Roasting System for LRF to be Cast

After the ladle masonry drying and baking are completed and deactivated, preheating and baking operations are carried out before being put into use, and the ladle scheduling records the baking on the record table Start and end time. The improved ladle baking system to be cast is shown in Table 2.

(2) Baking System of LRF out of Commission

Baking of LRF out of commission before use put into use again: Due to the excessive turnover of the ladle, the ladle is off the line, and the preheating and baking operation is carried out before being put back into use (the LRF parking time is calculated from the casting machine shutdown time). The improved baking system of LRF out of commission system is shown in Table 3.

The off-line LRF parking time is more than 2h, it is strictly prohibited to use, must be off-line baking; the parking time is 2 to 4h before the online baking time is controlled at more than 2h; the off-line ladle parking time is 4 to 8h before the online baking time is controlled at more than 4h ; The off-line ladle parking time 8 ~ 24h before the on-line baking time is controlled at more than 5h; the off-line ladle parking time exceeds 24h before the on-line baking time is controlled at more than 7h. The ladle schedule clearly records the start and end time of baking on the record table.

Improved Ladle Service Life

After adjusting the fixed repair mode, improving the ladle masonry process and baking system, the online safety performance of the ladle has been significantly improved, the number of abnormal off-line is significantly reduced, and the number of latent safety hazards and abnormal off-line impact on production is significantly reduced. The ladle age is further improved. The service life of ladle refractories has increased from an average of 120.45 furnaces in 2016 to an average of 121 furnaces in 2017.

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