Research on Longevity and Energy Saving of Water Jacket of Billet Continuous Casting and Straightening Machine

Abstract: This article introduces the problems existing in the water jacket of the red steel billet continuous casting tension and leveling machine. The service life of the cooling water jacket is directly related to the use of the tension and leveling machine, and also has a great impact on the quality of the casting billet and the operation rate of the casting machine. The reasons for the low life of the water jacket were analyzed, improvement measures were proposed, and a new type of water jacket that met actual production requirements was developed and achieved results.

Keywords: Tension and straightening machine; Water jacket; Longevity and energy saving

With the successful commissioning of the third phase project of Honghe Iron and Steel Co., Ltd. (hereinafter referred to as Red Steel) in 2009, the steelmaking plant has formed a production scale of 2 million tons/year, with a monthly output of more than 6,000 tons. The production pace is fast, and the energy-saving and intact equipment is the basic guarantee for smooth production. Among the billet continuous casting equipment, the tension leveler is the key equipment. In order to protect the tension leveler and its electrical and hydraulic equipment and extend the life of the tension leveler, a water tank is installed to prevent thermal radiation of the billet. During production and use, the water jacket has a short service life, often burns out, cracks, and leaks, and water is directly sprayed onto the slab, affecting the quality of the slab. At the same time, electrical and hydraulic equipment are not protected. Because the tension and leveling machine body and tension and leveling rollers are not well protected by cooling, they will deform, causing the tension and leveling machine body to be scrapped, affecting the operation rate of the casting machine and increasing maintenance costs.

1 Analysis of reasons for existence

After long-term follow-up inspection and review of drawings and data, it was found that the original water jacket of the tension and leveling machine had the following problems (see Figures 1 and 2):

(1) The water jacket of the continuous casting and tension leveling machine is divided into a front water jacket and a rear water jacket. Each has a water inlet and outlet for cooling through the cooling water of the equipment. Then the cooling water enters the water jacket and is divided into two channels for cooling at both ends of the water jacket. Since the water jacket pipeline is relatively long and thin, under high temperature conditions, the amount of cooling water is insufficient, and stagnant water is easily formed inside the water jacket, which can burn the water jacket;

Research on Longevity and Energy Saving of Water Jacket of Billet Continuous Casting and Straightening Machine

Figure 1 Burnt water jacket

(2) Since the water jacket pipeline is relatively long and thin, the quality requirements for the cooling water of the equipment are relatively high. It is easy to cause pipeline blockage and cannot be processed. The cooling water cannot be circulated for cooling, so the water jacket will be burned due to the high temperature;

(3) When the water jacket is burned out and needs to be replaced, it is not easy to replace it online. Because the tension and leveling rollers were stuck at the front and rear water jacket saddles, the entire tension and leveling machine had to be taken offline for maintenance and replacement, which took a long time. It takes about 4 hours at a time, and the entire machine must be dismantled and repaired after the tension and straightening is off the line, which is costly;

(4) When the water jacket ruptures, causing the entire circulating closed-circuit water system to be unstable, new water needs to be added to the pool to maintain the operation of the closed-circuit water system, which consumes large amounts of water resources and results in a waste of water resources;

(5) The consumption of spare parts is high, which increases the spare parts inventory funds and easily causes a backlog of funds. Therefore, in accordance with the purpose of cost reduction and energy conservation of Honggang Company of “strong benchmarking and deep tapping of potential”, Honggang Steelmaking Plant carried out the project of “Research on the Longevity and Energy Saving of Water Jackets of Billet Continuous Casting and Straightening Machines”. Improve the service life of the water jacket and the replacement cycle of the tension and straightening machine, reduce the consumption of spare parts and increase the start-up rate of the continuous casting machine.

Research on Longevity and Energy Saving of Water Jacket of Billet Continuous Casting and Straightening Machine

Figure 2 Water jacket structure before modification

2 Contents of the study

After reviewing a large amount of relevant information, a large number of theoretical experimental studies have been conducted on the water jacket of the tension leveling machine at home and abroad, as well as at Kunming Iron and Steel Technology Center. However, relevant research work mainly focused on the water jacket material, the diameter of the inlet and outlet pipes, and the water flow rate to improve the life of the water jacket of the tension leveler. The average life span was only increased by 8 months, and some results were achieved. The research on this topic mainly has the following research objectives based on the actual production site conditions of the Red Steel Steel Plant and from the perspective of modification and ease of installation.

(1) Solve the defects of continuous casting and straightening water jackets, increase the replacement life cycle, reduce maintenance time, reduce the labor intensity of maintenance personnel, and reduce water consumption.

1) The replacement cycle of the water jacket has been increased from 3 months to 12 months;

2) The time to replace the water jacket is reduced from the previous 4 hours to about 30 minutes;

3) It saves the consumption of water resources and saves 0.5 m³/t steel of circulating closed-circuit water every year.

(2) Conduct a series of tests to analyze and grasp the effect of the water jacket after it is put into use.

(3) Perform statistical tracking on the water jacket after use to examine whether the purpose of energy saving and efficiency creation has been achieved.

3 Improvement measures

(1) Change the structure of the water jacket device of the tension leveling machine and divide the original front water jacket and rear water jacket into three sections (see Figure 3 for details.)

Each section has a water inlet and outlet, so that the cooling water does not need to be diverted after entering the water jacket, which increases the cooling water flow rate of each section and improves the cooling effect. This solves the problem of the water jacket being burned without water, thereby reducing the consumption of spare parts.

(2) Change the connection method, separate the previous front and rear water jackets from under the tension and straightening roller (at the saddle), and connect the middle straight section into one body to form a three-body structure, as shown in Figure 3. In this way, the weight of each section is smaller, and online installation between sections can be achieved. When replacing later, the connecting plate needs to be cut into sections and the water jackets can be lifted out from both ends of the tension and leveling machine. This can greatly save maintenance time. It only takes about 30 minutes to replace the water jacket, which is 3.5 hours shorter than before.

(3) The water jacket of the tension leveling machine is made of flat oval tubes with dimensions of 85 mm × 25 mm × 5 mm and material Q235-A, which are overlapped and welded (see Figure 4 for details). It includes front water jacket 1, middle water jacket 2 and rear water jacket 3; during assembly, one end of front water jacket 1 and middle water jacket 2 are welded and connected by δ10 mm×100 mm×150 mm steel plate. The other end of the rear water jacket 3 is connected to the middle water jacket 2, and is welded and connected by a δ10mm×100mm×150mm steel plate, which is more convenient to assemble. Connect the water inlet 4 of the front water jacket, the water inlet 5 of the middle water jacket, and the water inlet 6 of the rear water jacket to the straightening cooling water pipe respectively. In this way, the cooling water flow of the three-stage water jacket is guaranteed, thereby improving the cooling effect of the water jacket and increasing the service life of the water jacket.

Research on Longevity and Energy Saving of Water Jacket of Billet Continuous Casting and Straightening Machine

Figure 3 Water jacket of new tension and leveling machine

Research on Longevity and Energy Saving of Water Jacket of Billet Continuous Casting and Straightening Machine

Figure 4 Cross-sectional view of the water jacket of the new tension and leveling machine

(4) As shown in Figure 5, the installation method of the new water jacket has not changed. It is fixed on the base of the tension and leveling machine with bolts using the installation plate in Figure 5. According to the water flow diagram in Figure 5, the number of water inlets and outlets of the water jacket of the tension leveling machine has doubled, and the flow direction of the cooling water in each water jacket has been improved. It avoids the phenomenon of water jacket bursting and burning caused by diversion (high water flow at the saddle is smaller) and uneven cooling, and improves the cooling effect.

Research on Longevity and Energy Saving of Water Jacket of Billet Continuous Casting and Straightening Machine

Figure 5 New water jacket put into use

4 Usage effects

Through the implementation of this topic, after the transformation of the water jacket of the tension leveling machine, the service life of the tension leveling machine was extended, the consumption of spare parts was reduced, and the surface quality of the cast slab was improved. It also correspondingly reduces the large amount of equipment or costs invested in improving water quality due to poor closed-circuit water quality. The use effect is good, the service life of the water jacket has been significantly improved, the expected technical indicators have been successfully completed, and the purpose of energy saving and consumption reduction has been achieved. This water jacket device is used for the first time in a domestic metallurgical continuous casting machine. Comprehensive comparison with the current domestic and foreign similar research and similar technologies, it belongs to the domestic advanced level and has broad prospects for use in the metallurgical industry in the future. The specific situation is shown in Table 1.

Table 1 Comparison of indicators before and after the transformation

TimeService life/month Replacement time/h New water consumption/(m³/t steel)  Whether it can be replaced online Benefits/(10,000 yuan/year)
Transformation of the former342.5no 
After transformation120.52able623.46

5 Conclusion

(1) After research and modification, the cooling effect of the water jacket device of the tension and leveling machine has been effectively improved, the service life of the water jacket has been extended, and the consumption of spare parts has been reduced. After the transformation, the service life of the tension and leveling water jacket increased from 3 months before the transformation to 12 months, ensuring the normal operation of the tension and leveling machine. Honggang Steelmaking Plant can save 39 sets of water jackets of tension and leveling machines every year, totaling 309,000 yuan.

(2) After research and transformation, the problem of inconvenient online replacement of the water jacket of the straightening machine has been solved, and the maintenance cost of the straightening machine has been reduced, (replacement of roller bearings, sealing rings, reducers, straightening rollers, metal hoses, etc. ), which can save 1.17 million yuan in maintenance costs every year.

(3) After research and transformation, the maintenance time has been greatly saved, from the previous 4 hours to about 30 minutes, saving 201.5 hours of maintenance time every year, effectively promoting the smooth progress of production, improving the operation rate of the casting machine, and reducing the intensity of maintenance , which brings convenience to the maintenance of equipment.

(4) After research and modification, the cooling effect of the water jacket has been effectively improved. This solves the problem of the cooling water jacket being burned out, the water jacket pipeline rupturing, the continuous casting machine being forced to shut down for processing, and water resources being wasted due to poor cooling of the water jacket. This also solves the problem of large water consumption due to the instability of the entire circulating closed-circuit water system due to the rupture of the water jacket, and the need to replenish new water to the pool to maintain the operation of the closed-circuit water system. It saves the consumption of water resources and saves 0.5 m³/t steel of circulating closed-circuit water every year.

(5) The quality problems of the slab caused by water tank leakage are reduced, and the surface quality of the slab is significantly improved.

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