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Several measures to effectively improve the service life of continuous casting tundish

Table of Contents

The continuous casting tundish is one of the key equipments in the continuous casting process. It has the functions of stabilizing and dividing the flow. It plays a very important role in smoothing the continuous casting operation and ensuring the quality of molten steel. The stable pouring of the tundish is conducive to extending the residence time of the molten steel in the tundish and uniformizing the temperature and composition of the molten steel. However, the working layer near the impact zone of the tundish is eroded by molten steel too quickly, which limits the service life of the tundish. By adding a flow stabilizer in the impact area of the molten steel in the tundish, the erosion of the working layer of the tundish near the impact area by the molten steel can be slowed down, thereby further increasing the age of the tundish. After installing the flow stabilizer, the motion trajectory of the molten steel in the tundish changes, reducing additional circulation, basically eliminating short-circuit flow, reducing slag entrainment, and promoting the floating of inclusions. However, there are still problems such as severe erosion and high temperature at the corners on both sides of the tundish, the seat bricks, and the nozzle, which reduces the service life of the tundish, causes an increase in billet rejection during heat exchange, high consumption of steel materials, and increases in refractory material costs. Therefore, it is necessary to improve and optimize the metallurgical process of the continuous casting tundish to extend the service life of the tundish, ensure the cleanliness of the molten steel, improve the quality of the cast slab, and meet user requirements.

Process flow and existing problems

Process flow: 50t double-blown converter → refining → continuous casting ladle rotary table → tundish → flow stabilizer → water inlet → crystallizer.

1) The working layer of the continuous casting machine tundish has been expanded and transformed many times, and the working lining is relatively thin, with the thickness of the working lining of the tundish being about 80mm. Moreover, the tundish cladding has not been updated after many years of use, and the cladding is severely deformed, resulting in uneven wall thickness. Recently, the corrosion thickness of the slag line in the working layer of the tundish has been more than 40mm after being used for more than 48 hours, and the erosion of the tundish slag line and impact area is serious. After the erosion of the tundish slag line, the temperature measured at this part is more than 50°C higher than that of other parts.

2) At present, in the production of stopper rod tundish of continuous casting machine, the plug head is subject to uneven and strong erosion by the molten steel in the tundish. After 12 hours of use, the stopper rod head erodes unevenly and quickly, causing the stopper rod tundish to be unable to control flow stably, which is a key factor limiting the service life of the stopper rod tundish.

3) At the end of the service life of the sizing tundish, the upper nozzle of the tundish erodes too quickly and the zirconium core falls off. Problems such as nozzle blockage and continuous casting interruption often occur, which seriously affects the efficient production of continuous casting. The above factors lead to frequent unplanned replacement of tundishes, which seriously affects the improvement of the service life of the tundish and brings greater risks to the safety and stable production of the continuous casting machine.

improvement measures

  • Tundished slag line magnesia carbon brick composite repair technology

The refractory material of the tundish is divided into two parts: the permanent layer and the working layer. The permanent layer is mainly used for thermal insulation of the tundish and has poor corrosion resistance. The working layer is mainly used to resist the erosion of high-temperature molten steel and steel slag, and the insulation effect is relatively poor. Improving the corrosion resistance of the tundish slag line is mainly improved by optimizing the working layer.

Develop a tundished slag line magnesia carbon brick masonry technology. According to the erosion width of the tundish slag line and the thickness of the tundish working layer, a 300mm×300mm×30mm special magnesia carbon brick for the tundish slag line is designed. The material of the tundish working layer is magnesia dry material. According to the different erosion conditions in the tundish, the material of the magnesia dry material in the slag line of the tundish is improved, and the corrosion resistance of the magnesia dry material in the slag line is improved. Magnesia dry materials are divided into two types: slag line magnesia dry materials and bottom package magnesia dry materials. Magnesium dry materials for the bottom of the tundish are used below the tundish slag line and at the bottom of the tundish, and special magnesium dry materials are used for the tundish slag line. During the preparation of the tundish, after the permanent layer of the tundish is knotted, the working layer of the tundish is knotted. First, fill the bottom of the middle slag line with magnesium dry material. Then place a circle of special magnesia carbon bricks for the slag line along the inner wall of the permanent layer of the tundish, and finally fill the slag line magnesia dry material. After 1.5 to 2.0 hours of baking over medium and low heat, it is formed.

  • Combined construction of magnesium plates in the impact area of the tundish

Increase the thickness of the working layer in the impact zone of the tundish. Due to the limited space of the tundish impact zone, the thickness of the permanent layer in the tundish impact zone was reduced from 200 to 220 mm to 150 to 170 mm. The thickness of the working layer in the impact zone of the tundish increases accordingly from 80 to 100mm to 130 to 150mm. Increasing the thickness of the working layer in the tundish impact zone can significantly improve the erosion resistance of the tundish impact zone.

Develop a combined masonry process of magnesium plates in the impact zone of the tundish, and design special magnesium plates for the impact zone of the tundish according to the shape and size of the tundish. The magnesia board is knotted with tundished materials and is divided into three types: outer arc plate, side arc plate and side plate. The thickness of the magnesia outer arc plate and side arc plate is 100mm, and the thickness of the magnesia side plate is 50mm. The outer arc plate, side arc plate and side plate of the magnesium plate in the tundish impact area are combined to protect the working layer in the tundish impact area. After the knotting of the tundish working layer is completed, a flow stabilizer is installed in the impact area of the tundish. The magnesium outer arc plate is installed above the flow stabilizer, and the two magnesia side arc plates are installed on the left and right sides of the flow stabilizer. Two magnesium side plates are installed on either side of the corner of the strike zone. After installation, use a coating material for bonding and bake over medium and low heat for 1.5 to 2.0 hours before taking shape.

  • Long-life nozzle for continuous casting tundish

In order to solve the problem of excessive corrosion of the nozzle of the tundish and the shedding of the zirconium core, a new type of long-life nozzle was developed and used. Increase the height of the inverted nozzle, increase the thickness of the magnesium carbon protective layer on the upper nozzle zirconium core, and reduce the erosion of the zirconium core by molten steel; increase the overall thickness of the zirconium core at the nozzle to improve the corrosion resistance of the zirconium core.

1) Design of overall dimensions. The height of the nozzle is increased from 95mm to 145mm. A magnesium carbon protective refractory is added to the upper end of the zirconium core at the upper nozzle. The thickness of the magnesium carbon protective refractory is 20mm, which serves to isolate the zirconium core from the upper nozzle and the molten steel and reduce the direct erosion and erosion of the upper end of the zirconium core by molten steel.

2) Optimization of zirconium material in the inner cavity. The height of the main body of the zirconium core at the upper nozzle is increased from 80mm to 125mm, and the overall thickness of the main body of the zirconium core at the upper nozzle is increased by 2mm. The inner hole at the upper end of the zirconium core at the upper nozzle that is in direct contact with the molten steel is designed as an R arc with a radius of 5mm to improve the strength of the zirconium core at the upper nozzle. And buffer the impact of molten steel on the zirconium core.

Stopper rod tundish combined with cofferdam seat brick

The quality of the stopper rods, seat bricks, and nozzle refractory materials used in the continuous casting tundish determines the service life of the stopper rod tundish. The seat brick is used in conjunction with the nozzle of the tundish. Its main function is to fix and protect the nozzle of the tundish, and improve the installation accuracy and service life of the nozzle. The stopper rod cooperates with the nozzle of the tundish to control the flow.

In order to solve the problem of uneven and rapid erosion of the stopper rod head of the stopper rod tundish, a combined cofferdam seat brick with stopper rod tundish was developed. The modular seat brick is divided into two parts. The lower seat brick is used to position the tundish seat brick and the nozzle. The upper seat brick is higher than the matching nozzle bowl of the tundish, and plays a role in protecting the nozzle bowl of the tundish and the stopper rod head. The combination of the nozzle of the stopper rod tundish, the stopper rod, and the combined cofferdam seat brick solves the problem of uneven and rapid erosion of the stopper rod head by molten steel in the tundish, and increases the service life of the stopper rod tundish.

Ladle sliding nozzle - how to solve the problem of steel wear

Implementation Effect

1.The composite masonry process of the tundish working layer greatly improves the erosion resistance of the tundish slag line. After the implementation of the process, it was observed that the tundish was used for 48 hours. The erosion of the working layer at the slag line of the tundish disappeared and the shape of the magnesia carbon bricks was intact. It was observed that the tundish was used for 70 hours. Some magnesia carbon bricks remained at the slag line of the tundish. After the tundish was turned over, , check that the permanent layer is intact.

2.The combined masonry process of magnesium plates in the impact zone of the tundish improves the erosion resistance of the impact zone of the tundish.

After the process was implemented, it was observed that the tundish was used for 48 hours. The shape of the magnesium carbon plate in the impact area of the tundish was obviously eroded, and the working layer was intact. It was observed that the tundish was used for 70 hours. The magnesium carbon plate in the impact area of the tundish disappeared and the erosion thickness of the working layer was 100~150mm. , in 2019, the number of tundishes that were offline due to severe erosion in the impact zone was reduced to zero.

tundish in steel making

3.The application of the stopper rod tundish combined cofferdam seat brick effectively solves the problem of uneven and rapid erosion of the stopper rod head in the stopper rod tundish, and greatly improves the corrosion resistance of the stopper rod head. After the process was implemented, it was observed that the stopper rod tundish was used for 11 hours, and the rod head of the plug rod tundish was slightly eroded; it was observed that the plug rod tundish was used for 18 hours, and the rod head of the plug rod tundish was significantly eroded, but it was obviously lighter than before optimization and can continue to be used.

4.The application of the new long-life nozzle reduces the erosion of the zirconium core by molten steel. After 72 hours of on-site use, the nozzle of the tundish did not burst, and the entry of foreign matter into the nozzle was reduced to once per month.

By applying the magnesia-carbon brick composite repair technology of the tundish slag line, the magnesia plate combined repair technology of the tundish impact area, the long-life nozzle technology of the continuous casting tundish, and the plug-rod tundish combined cofferdam seat brick technology, Laiwu Branch The overall erosion resistance of the tundish in the steelmaking plant is improved, the refractory material in the impact zone is stable, the cleanliness of the molten steel is ensured, the metal yield is increased, and the average life of the sizing tundish is increased from 48h/package to 72h/package.

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As professional one-stop solution provider, LIAONING MINERAL & METALLURGY GROUP CO., LTD(LMM GROUP) Established in 2007, and focus on engineering research & design, production & delivery, technology transfer, installation & commissioning, construction & building, operation & management for iron, steel & metallurgical industries globally. 

Our product  have been supplied to world’s top steel manufacturer Arcelormittal, TATA Steel, EZZ steel etc. We do OEM for Concast and Danieli for a long time.

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As professional one-stop solution provider, LIAONING MINERAL & METALLURGY GROUP CO., LTD(LMM GROUP) Established in 2007, and focus on engineering research & design, production & delivery, technology transfer, installation & commissioning, construction & building, operation & management for iron, steel & metallurgical industries globally. 

Our product  have been supplied to world’s top steel manufacturer Arcelormittal, TATA Steel, EZZ steel etc. We do OEM for Concast and Danieli for a long time.

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