Practice of Capacity Expansion and Bottom Process Optimization for Steel ladle
The actual usage volume of the ladle seriously affects the production rhythm of the converter, and also restricts the production efficiency of the 300t converter. The average furnace output of the 300t converter at home and abroad must be greater than the nominal design capacity, and the average furnace output of the converter must be less than 290t. This is an important bottleneck that has long plagued the efficiency of production. Therefore, we are determined to expand the capacity of the ladle, thoroughly solve the various drawbacks caused by the small size of the ladle, and achieve stable production operation. Let's learn about the practice of ladle capacity expansion and bottom process optimization together!
Capacity expansion and renovation of steel ladle
1.1 Requirements for Capacity Expansion and Renovation of Steel ladle
In order to reduce renovation costs, the company has decided to utilize existing luggage boxes, including old luggage bottoms, luggage bottom supports, and flipping devices. The bottom of the ladle maintains the current dimensions of each part, with significant support around the ear shaft seat and utilization of the ladle seat. The welding and heat affected zone with the cylinder are removed, with 35mm removed on both sides. The length of the ear shaft embedded in the ear shaft seat is relatively shortened, so that the inner ear shaft fixing block and protruding part are consistent with the original inner wall of the ladle, without changing the size of the ladle overturning device for reuse. The bottom of the package is first cut along the weld seam, as shown in Figure 1. The height of the bottom of the ladle is 90mm, and the welding position of the ladle wall and bottom has been changed from the inner side to the outer side. Transition welding has been carried out, and the R20mm corner has been polished smooth. The ladle bottom has been flush with the ladle wall from before the renovation until now, ensuring that the thickness of the permanent layer of the ladle is the same after masonry.
Due to an increase in the diameter of the ladle body by approximately 68mm, it is necessary to replace the steel plate of the ladle body. In order to ensure strength, the thickness of the steel plate has been increased from 40mm to 42mm. The ladle ear shaft and ear shaft seat are important parts for ladle lifting. At present, the service life of 37 existing steel ladles in the company exceeds 8 years. Grinding occurred during the lifting and transportation of the ear shaft. For safety reasons, the ear shaft will be replaced during capacity expansion and renovation. After increasing the capacity of the ladle, in order to maintain the external dimensions unchanged, after review by the design institute, the strip steel and water tank bracket are new products with shorter inner dimensions. However, in order to ensure strength and increase plate thickness, the ladle is equipped with a hinged cover and the upper opening position and horizontal distance of the ladle are reduced by 35mm. The diameter of the ladle cover is the same as the outer diameter of the ladle, and the hinge base is constructed according to the drawing. The technical parameters of each part of the ladle are shown in Table 1.
1.2 Impact on other devices
After the capacity expansion and renovation of the ladle, the increase in cladding size has a certain impact on related equipment. During the capacity expansion and renovation of the steel ladle, the company fully considered important limiting factors such as the 480t day hook, offline steel ladle baking, steel ladle truck, 480t over limit truck, LF furnace, RH furnace, CAS furnace, steel ladle cover system, and casting machine turntable, ensuring that the above main equipment did not change.
1.2.1 Impact of Expansion on the Hook of Longmen Crane
At present, the center distance of the 480t overhead crane gantry hook is 5600mm. After the diameter of the airbag increases, it is necessary to solve the problem of how to maintain the normal and safe lifting of the airbag without replacing the gantry hook. In order to ensure the stability of the gantry crane, after rigorous verification, the reinforcing plates on both sides of the pouring ladle are shortened in the width direction to increase the thickness of the steel plate and ensure a certain interval between the gantry cranes. After increasing the capacity of the ladle, the water content per ladle has increased from 290 tons to 320 tons, with a cladding weight of about 71 tons and a refractory weight of about 80 tons. The total weight is about 470 tons, but the weight of the overhead crane is 480 tons, so the capacity has not exceeded the load of the overhead crane. 1.2.2 The impact of expansion on tire wrap
After the steel ladle becomes larger, the diameter of the ladle body increases by about 68mm. Therefore, the raw tire used as a permanent layer needs to be discarded, and the diameter of the ladle body correspondingly increases to match the newly added ladle. The dimensions and structure of other parts remain unchanged.
1.2.3 Impact of Expansion on Steel Ladle Related Auxiliary Equipment
As the capacity increase height of the ladle has not increased, it will not affect the offline baking, LF furnace, RH furnace, and CAS furnace of the ladle. However, if the ladle becomes thicker, it will affect the ladle cover, ladle seat bracket, and fork arm of the ladle turntable. In order to minimize changes to the current equipment size, equipment experts finally reached a consensus during on-site surveying and testing:
The diameter of the mouth of the newly poured ladle is 4700mm, which is the same as the diameter of the ladle cover. It is required that the cover does not fall off inside the ladle, and it should be made into a permanent layer of refractory bricks and then covered. The diameter of the ladle has changed to 4386mm, and the distance between the two sides after sitting on the ladle fork arm has increased from the original 35mm to about 10mm now. The reduction in distance has a certain impact on the stable packaging turntable of the ladle. The wear-resistant bands of the ladle and ladle fork need to be polished to 15mm, and the manufacturer is required to control the diameter of the ladle with negative tolerance when manufacturing it.
1.3 Requirements for expanding the construction of steel ladle
Before connecting the permanent layer of the package wall, construct asbestos boards on the package wall and connect them with lightweight castables. Control the amount of water added to lightweight materials at around 6% to 8%, stir evenly, set up new ladle molds, and operate according to existing technical requirements. The bottom of the package is tied with heavy-duty straps, and the support bricks for the bottom and water outlet are constructed using existing masonry methods. That is, first install the upper and lower bricks, and then assemble the bottom brick so that the gap between the bricks is less than 2mm. The gaps between the bricks are staggered vertically and horizontally, and the gaps between the bricks are covered with soil. The bottom of the building is accurate and firm.
For the expanded and renovated ladle cladding, the working layer of the ladle wall is lined with 190mm inner lining, and the slag line is made of 210mm magnesia carbon bricks. Before the formal implementation of the production organization for restoring the capacity of steel ladles, it is necessary to ensure that they are used for more than 25 times. The working layer of the medium repair steel ladle wall uses 180mm lining bricks, and the slag line uses 210mm magnesia carbon bricks.
Optimization of Bottom Blowing in Pot 2
2.1 Optimization of Breathable Brick Structure
During use and pouring, high-temperature molten steel and slag may penetrate through gaps to blow the bottom of the original slit type permeable brick, causing the airway to be blocked by the permeable steel and slag. Therefore, a new type of narrow slit composite dispersed breathable brick was produced. The breathable brick is mainly composed of an argon gas pipe, a brick core body, a circular cone (slit block), a dispersing block, and a brick core supporting brick. The argon gas pipe is welded to the iron sheet of the brick core body, and the circular cone (slit block) is installed near the lower part of the interior of the brick core body.
The above introduction is the practice of steel ladle capacity expansion and ladle bottom process optimization. If you need to learn more, please feel free to contact us at any time!