A method for supplying protective gas for continuous casting of cast steel and its circuit system

Abstract

This invention discloses a method and circuit system for supplying protective gas for continuous casting of steel. The gas supply method is used to blow protective gas onto the stopper rod, the top nozzle, and the mechanical seals during three stages: the pre-casting baking stage, the casting stage, and the post-casting stage. Specifically, during the pre-casting baking stage, nitrogen is used to cool the stopper rod, the top nozzle, and the mechanical seals; during the casting stage, argon is used to cool the stopper rod, the top nozzle, and the mechanical seals; and after casting, nitrogen is used to cool the stopper rod, the top nozzle, and the mechanical seals. The circuit system is designed to implement the above gas supply scheme. This invention's method and circuit system for supplying protective gas for continuous casting of steel achieves a balance between process and cost, implementing cost control at each process control stage, within the limits of process feasibility.

Description

Technical Field

[0001] This invention belongs to the field of continuous casting steel technology, specifically relating to a method for supplying protective gas for continuous casting steel and its circuit system. Background Technology

[0002] The entire process of continuous casting steel production involves molten steel cooling and solidifying in a crystallizer to form a billet shell. With the continuous vibration of the crystallizer and the drive of the main casting straightening device, the molten steel within the solidified billet shell, containing a liquid core, continuously crystallizes and solidifies. After bending and straightening in the secondary cooling zone and solidifying again, it is pulled out of the casting machine. In continuous casting without oxidation, argon is an essential gas. Its main functions in continuous casting are to stir the molten steel to equalize its temperature, protect it from secondary oxidation, prevent nodule formation in the pouring channels and stopper heads, and promote the flotation of inclusions in the molten steel in the crystallizer and secondary cooling zone. Therefore, argon blowing through the stopper bars of tundishes and argon blowing through submerged entry nozzles are widely used in many steel plants' continuous casting machines.

[0003] In existing continuous casting equipment in many steel mills, the argon gas pipelines on the tundish cars are all single argon gas supply systems. In the continuous casting process, before being put into production, the tundish, along with its associated stoppers and submerged entry nozzles, must be preheated to approximately 1200 degrees Celsius to prevent the molten steel from freezing due to excessively low initial pouring temperature, which could lead to abnormal final pouring accidents. During the preheating process, gas must be blown into the stoppers and submerged entry nozzles for cooling to prevent the vent plugs inside from clogging due to high-temperature oxidation, which would affect the stability of continuous casting production. However, most existing steel mills only have a single argon gas control pipeline, meaning that during the tundish preheating process, only expensive argon gas can be used for cooling, resulting in energy waste and increased cost per ton of steel. The argon gas consumption for each tundish stopper is approximately 10L / min, and for the top nozzle, it's 10L / min, with an average preheating time of about 2 hours per tundish. Summary of the Invention

[0004] The purpose of this invention is to provide a gas-cooled cooling solution that balances process and cost.

[0005] To achieve the above technical objectives, this invention provides a method for supplying protective gas for continuous casting of cast steel and its circuit system, the specific technical solution of which is as follows:

[0006] A method for supplying protective gas for continuous casting of steel is disclosed, which is used to blow protective gas to the stopper rod, the top nozzle, and the mechanism seals in three stages: the baking process before casting, the casting process, and the post-casting stage.

[0007] When the baking process is in progress before casting, nitrogen gas is used to cool the stopper rod, water inlet and mechanism seals.

[0008] When the pouring process is underway, the stopper rod, the water inlet and the mechanism seal are cooled with argon gas.

[0009] After the pouring is completed, nitrogen is used to cool the stopper rod, water inlet, and mechanism seals.

[0010] Furthermore,

[0011] When in the casting process, the stopper rod and the water inlet are cooled by argon gas or a nitrogen-argon mixture.

[0012] Furthermore,

[0013] The gas supply method specifically includes the following steps:

[0014] S1: When the PLC detects that the intermediate batch car has reached the preheating position, it sends a baking start signal to the regenerative baking unit. At the same time, the baking start signal is used as a trigger signal to trigger the nitrogen pipeline to the stopper rod, the water inlet and the mechanism seal to form a passage.

[0015] S2: When the PLC receives the baking end signal, it triggers the pipeline leading to the stopper rod, water inlet and mechanism seal to enter the nitrogen-argon switching mode; at the same time, it reads the correspondence between the current steel grade and nitrogen in the process computer; when it reads that the current steel grade has strict requirements for nitrogen, it proceeds to step S3, otherwise it proceeds to step S4.

[0016] S3: When the PLC detects that the intermediate ladle car has moved to the pouring position, it triggers the formation of an argon gas pipeline leading to the stopper rod, the water inlet and the mechanism seal; until the pouring is completed, proceed to step S5;

[0017] S4: When the PLC detects that the intermediate ladle car has moved to the pouring position, it triggers the nitrogen and argon gas pipelines leading to the stopper rod and the water inlet to form a passage, and blows the stopper rod and the water inlet with a mixed gas to cool them; it triggers the argon gas pipeline leading to the mechanism seal to form a passage; until the pouring is completed, proceed to step S5.

[0018] S5: The PLC controls the nitrogen passage to the stopper rod, water inlet, and mechanism sealing pipeline.

[0019] Furthermore,

[0020] Gas mixers are installed at the front end of the stopper rod and the front end of the water inlet. In step S4, the stopper rod and the water inlet are cooled by blowing mixed gas. This is achieved by setting argon gas pipelines and nitrogen gas pipelines that both lead to their respective gas mixers.

[0021] Furthermore,

[0022] In step S4, the mixing concentration ratio of the nitrogen-argon mixture leading to the stopper rod and the water inlet is determined according to the current steel grade.

[0023] Furthermore,

[0024] The argon gas supplied to the stopper rod is low-pressure argon gas, while the argon gas supplied to the water inlet and the mechanism seal is high-pressure argon gas.

[0025] A gas supply line system for protective gas used in continuous casting of cast steel.

[0026] Three parallel nitrogen pipelines are installed between the nitrogen supply source and the stopper rod, the water inlet, and the mechanism seal, respectively.

[0027] The first parallel nitrogen pipeline is located between the gas supply source and the stopper rod inlet.

[0028] The second parallel nitrogen pipeline is located between the gas supply source and the water inlet.

[0029] The third parallel nitrogen pipeline is located between the gas supply source and the sealed gas inlet of the mechanism;

[0030] at the same time,

[0031] Three argon gas pipelines are respectively installed between the argon gas supply source and the stopper rod, the water inlet, and the mechanism seal;

[0032] A low-pressure argon gas pipeline is installed between the argon gas supply source and the stopper rod inlet.

[0033] A first high-pressure argon pipeline is installed between the argon gas supply source and the water inlet.

[0034] A second high-pressure argon gas pipeline is installed between the argon gas supply source and the sealed inlet of the mechanism.

[0035] Furthermore,

[0036] A first gas mixer is installed at the front end of the stopper rod inlet. Nitrogen and argon gas lines leading to the stopper rod inlet are introduced through the first gas mixer.

[0037] A second gas mixer is installed at the front end of the water inlet air inlet. Nitrogen and argon gas pipelines leading to the water inlet air inlet are introduced through the second gas mixer.

[0038] Furthermore,

[0039] The first high-pressure argon gas pipeline and the second high-pressure argon gas pipeline are connected in parallel.

[0040] The low-pressure argon gas pipeline and the parallel pipeline consisting of the first high-pressure argon gas pipeline and the second high-pressure argon gas pipeline are set up independently.

[0041] or

[0042] The first high-pressure argon gas pipeline and the second high-pressure argon gas pipeline are connected in parallel, and then connected in parallel with the low-pressure argon gas pipeline.

[0043] Furthermore,

[0044] A nitrogen-argon switching solenoid valve is installed at the front end of the mechanism sealing air inlet. The nitrogen and argon pipelines leading to the mechanism sealing air inlet are connected to the mechanism sealing air inlet via the nitrogen-argon switching solenoid valve.

[0045] Furthermore,

[0046] On the first parallel nitrogen pipeline, the second parallel nitrogen pipeline, the low-pressure argon pipeline, the first high-pressure argon pipeline, and the pipeline between the mechanism sealing inlet and the mechanism sealing nitrogen-argon switching solenoid valve, each has its own main flow control setting and bypass branch flow control setting.

[0047] This invention discloses a method and circuit system for supplying protective gas for continuous casting of steel. It changes the previous method of using argon gas to cool the tundish without any change. By adopting different cooling control for the stopper rod, the top nozzle, and the mechanical seal at different process stages, it balances cost and process considerations at each process control stage, which has a significant effect on reducing costs and consumption. At the same time, it also combines nitrogen and argon gas cooling with specific steel grades, and establishes a setting for corresponding cooling control during the casting stage according to the steel grade. Attached Figure Description

[0048] Figure 1 This is a schematic diagram illustrating the steps of a method for supplying protective gas for continuous casting of steel according to the present invention.

[0049] Figure 2 This is a schematic diagram of the circuit structure of a protective gas supply system for continuous casting of cast steel according to the present invention.

[0050] In the picture,

[0051] M1 - Manual shut-off valve for nitrogen inlet;

[0052] M2 - Low-pressure argon manual shut-off valve;

[0053] M3 - High-pressure argon manual shut-off valve;

[0054] Y1 - Stopper rod nitrogen solenoid valve;

[0055] Y2 - Nitrogen solenoid valve for water inlet;

[0056] Y3 - Mechanism-sealed nitrogen / argon gas switching solenoid valve;

[0057] Y4 - Stopper rod nitrogen bypass solenoid valve;

[0058] Y5-Plug Argon Pantone Solenoid Valve;

[0059] Y6 - Nitrogen bypass solenoid valve for water inlet;

[0060] Y7 - Argon bypass solenoid valve for water inlet;

[0061] Y8 - Mechanism-sealed gas bypass solenoid valve;

[0062] PI01 to PI10 - Remote pressure sensors;

[0063] PT01 to PT10 - Pressure gauges;

[0064] CV1 to CV6 - Check valves;

[0065] FI01 to FI10 - Remote flow meters;

[0066] AV1 to AV5 - Automatic Flow Regulators;

[0067] V1 to V5 - Manual flow control valves;

[0068] PV1 to PV4 - Pressure regulating valves;

[0069] Mixer - Gas mixer. Detailed Implementation

[0070] The following is a detailed description of a method for supplying protective gas for continuous casting of steel and its circuit system, based on the accompanying drawings and specific embodiments of the present invention.

[0071] To facilitate understanding of this technical solution, its working principle and process are described below:

[0072] A method for supplying protective gas for continuous casting steel is disclosed, used to blow protective gas onto the stopper rod, top nozzle, and mechanical seals in three stages: the pre-casting baking stage, the casting stage, and the post-casting stage. Specifically, during the pre-casting baking stage, nitrogen is used to cool the stopper rod, top nozzle, and mechanical seals; during the casting stage, argon is used; and after casting, nitrogen is used again. This control setup effectively achieves both cost and energy reduction. Furthermore, to further reduce costs and energy consumption, the cooling protective gas supply is combined with the steel grade and innovatively configured. When the current steel grade has strict nitrogen requirements, argon is used for cooling alone; when the current steel grade does not have strict nitrogen requirements, a nitrogen-argon mixture is used. When using a nitrogen-argon mixture, the specific mixing concentration ratio is determined based on the actual steel grade. This setup fully integrates the innovative concept of cost reduction and efficiency improvement into every stage of the process. For specific control logic, please refer to [link / reference needed]. Figure 1Specifically:

[0073] S1: When the PLC detects that the intermediate batch car has reached the preheating position, it sends a baking start signal to the regenerative baking unit. At the same time, the baking start signal is used as a trigger signal to trigger the nitrogen pipeline to the stopper rod, the water inlet and the mechanism seal to form a passage.

[0074] S2: When the PLC receives the baking end signal, it triggers the pipeline leading to the stopper rod, water inlet and mechanism seal to enter the nitrogen-argon switching mode; at the same time, it reads the correspondence between the current steel grade and nitrogen in the process computer; when it reads that the current steel grade has strict requirements for nitrogen, it proceeds to step S3, otherwise it proceeds to step S4.

[0075] S3: When the PLC detects that the intermediate ladle car has moved to the pouring position, it triggers the formation of an argon gas pipeline leading to the stopper rod, the water inlet and the mechanism seal; until the pouring is completed, proceed to step S5;

[0076] S4: When the PLC detects that the intermediate ladle car has moved to the pouring position, it triggers the nitrogen and argon gas pipelines leading to the stopper rod and the water inlet to form a passage, and blows the stopper rod and the water inlet with a mixed gas to cool them; it triggers the argon gas pipeline leading to the mechanism seal to form a passage; until the pouring is completed, proceed to step S5.

[0077] S5: The PLC controls the nitrogen passage to the stopper rod, water inlet, and mechanism sealing pipeline.

[0078] During mixed gas cooling, in order to ensure a gradual pressure of the cooling gas, gas mixers (i.e., gas mixers) are installed at the front end of the stopper rod inlet and the front end of the upper water inlet, respectively. Figure 2 Mixer in (the game).

[0079] The corresponding line structure system, such as Figure 2 As shown, the entire control system is based on a PLC, and data interaction is established between the PLC and the process control unit to determine and issue the decision on whether to cool the casting section with argon gas alone or with a nitrogen-argon mixture. The established system is supplied with nitrogen (N2), low-pressure argon (Ar.L.), and high-pressure argon (Ar.H.). Figure 2As shown, three parallel nitrogen pipelines are respectively installed between the nitrogen supply source and the stopper rod, the water inlet, and the mechanism seal. The first parallel nitrogen pipeline is located between the supply source and the stopper rod inlet, the second parallel nitrogen pipeline is located between the supply source and the water inlet, and the third parallel nitrogen pipeline is located between the supply source and the mechanism seal inlet. At the same time, three argon pipelines are respectively installed between the argon supply source and the stopper rod, the water inlet, and the mechanism seal. A low-pressure argon pipeline is installed between the argon supply source and the stopper rod inlet, a first high-pressure argon pipeline is installed between the argon supply source and the water inlet, and a second high-pressure argon pipeline is installed between the argon supply source and the mechanism seal inlet. A mechanism seal nitrogen-argon switching solenoid valve is installed at the front end of the mechanism seal inlet. The nitrogen pipeline and argon pipeline leading to the mechanism seal inlet are connected to the mechanism seal inlet via the mechanism seal nitrogen-argon switching solenoid valve. On the first parallel nitrogen pipeline, the second parallel nitrogen pipeline, the low-pressure argon pipeline, the first high-pressure argon pipeline, and the pipeline between the mechanism's sealed inlet and the mechanism's sealed nitrogen-argon switching solenoid valve, each has its own main flow control setting and bypass branch flow control setting. With this configuration, during operation, the gas supply from the stopper rod and the water inlet is respectively collected by nitrogen and argon branches and then supplied to the gas mixer. Each nitrogen branch consists of a solenoid shut-off valve, a pressure regulating valve, a mass flow regulating valve, and a bypass branch. The bypass branch is equipped with a solenoid shut-off valve, a flow meter, and a manual flow regulating valve. The bypass branch is only used in case of a mass flow controller failure; when using it, the corresponding bypass solenoid valve must be opened before gas can flow. One-way valves are used in the system to prevent gas backflow.

[0080] Referring to Table 1, the flow rates shown in Table 1 represent only a specific real-world scenario. Different flow rates can be set for different real-world scenarios, but the control logic follows the rules in Table 1. The "+" sign indicates trigger activation, and the "-" sign indicates trigger deactivation. The listed modes are selected based on different operating conditions. The system control is divided into the following control modes, which are switched by the PLC collecting limit signals from the tundish car based on its position. When reaching the preheating position, it automatically switches to baking mode upon receiving the start signal from the regenerative baking unit. When it receives the end signal from baking, it switches to nitrogen-argon switching mode. When the tundish car reaches the pouring position, it automatically switches to normal pouring mode. When it leaves the pouring position, it switches to final pouring mode. A one-button emergency mode is used for rapid flow setting during rapid deceleration in pouring to prevent excessive gas flow from causing the molten steel surface to churn and splash in the crystallizer.

[0081]

[0082] Table 1

[0083] Simultaneously, the system can fully utilize the PLC's automatic flow timing setting to develop a one-click leak detection function. Specifically, by adding a plug to the end of the pipeline, the program controls the flow rate setting of 30 l / min for each line. The system records the results of each leak detection operation. If the actual flow rate is found to be greater than 0 l / min, the system will issue an alarm while recording the leak detection record. The operator is required to handle the leak and then perform another leak detection to complete the leak detection operation.

[0084] This invention discloses a method and circuit system for supplying protective gas for continuous casting steel. During casting and baking, the required gas can be automatically switched according to different production processes based on process and cost control requirements. Specifically, during tundish baking, nitrogen can automatically replace argon to cool the stopper rod and nozzle, preventing blockage of channels and vent plugs, and avoiding heat damage to pipes and seals that could cause leaks. When the tundish baking is completed and the operator leaves the baking position, the baking mode is automatically shut off, switching to a nitrogen-argon switching mode, i.e., nitrogen is shut off while argon is automatically turned on according to process control parameters. After final casting, the system switches back to nitrogen cooling mode to protect the sealing rings of the quick-connect fittings at the stopper rod and immersion argon inlet pipe interfaces, extending the service life of the sealing rings and thus improving the service life of the quick-connect fittings. Simultaneously, a PLC-based one-button leak detection function is implemented, significantly reducing the labor intensity of operators in checking for leaks in the gas supply pipeline.

[0085] In summary, this system addresses the energy conservation and environmental protection needs of on-site production while also considering the auxiliary gas requirements for continuous casting under various working conditions. Through programmed control of the control device, combined with parameter adjustment functions and preset flow rates for different modes, it achieves gas usage under diverse operating conditions. Using this device reduces the consumption of large amounts of rare inert gases during the baking process of each tundish, while also reducing the workload of frontline operators.

Claims

1. A method for supplying protective gas for continuous casting of steel, used to blow protective gas to the stopper rod, the top nozzle, and the mechanical seals in three stages: the pre-pouring baking stage, the pouring stage, and the post-pouring stage, characterized in that: When the baking process is in progress before casting, nitrogen gas is used to cool the stopper rod, water inlet and mechanism seals. When in the casting process, the stopper rod and the water inlet are cooled with argon or a nitrogen-argon mixture, and the mechanism seal is cooled with argon. After the pouring is completed, the stopper rod, water inlet and mechanism seals are cooled with nitrogen. The gas supply method specifically includes the following steps: S1: When the PLC detects that the intermediate batch car has reached the preheating position, it sends a baking start signal to the regenerative baking unit. At the same time, the baking start signal is used as a trigger signal to trigger the nitrogen pipeline to the stopper rod, the water inlet and the mechanism seal to form a passage. S2: When the PLC receives the baking end signal, it triggers the pipeline leading to the stopper rod, water inlet and mechanism seal to enter the nitrogen-argon switching mode; at the same time, it reads the correspondence between the current steel grade and nitrogen in the process computer; when it reads that the current steel grade has strict requirements for nitrogen, it proceeds to step S3, otherwise it proceeds to step S4. S3: When the PLC detects that the intermediate ladle car has moved to the pouring position, it triggers the formation of an argon gas pipeline leading to the stopper rod, the water inlet and the mechanism seal; until the pouring is completed, proceed to step S5; S4: When the PLC detects that the intermediate ladle car has moved to the pouring position, it triggers the nitrogen and argon gas pipelines leading to the stopper rod and the water inlet to form a passage, and blows the stopper rod and the water inlet with a mixed gas to cool them; it triggers the argon gas pipeline leading to the mechanism seal to form a passage; until the pouring is completed, proceed to step S5. S5: The PLC controls the nitrogen passage to the stopper rod, water inlet, and mechanism sealing pipeline.

2. The method for supplying protective gas for continuous casting of steel according to claim 1, characterized in that: Gas mixers are installed at the front end of the stopper rod and the front end of the water inlet. In step S4, the stopper rod and the water inlet are cooled by blowing mixed gas. This is achieved by setting argon gas pipelines and nitrogen gas pipelines that both lead to their respective gas mixers.

3. The method for supplying protective gas for continuous casting of steel according to claim 1, characterized in that: In step S4, the mixing concentration ratio of the nitrogen-argon mixture leading to the stopper rod and the water inlet is determined according to the current steel grade.

4. The method for supplying protective gas for continuous casting of steel according to claim 1, characterized in that: The argon gas supplied to the stopper rod is low-pressure argon gas, while the argon gas supplied to the water inlet and the mechanism seal is high-pressure argon gas.

5. A gas supply system for protective gas used in continuous casting of cast steel, characterized in that: Three parallel nitrogen pipelines are installed between the nitrogen supply source and the stopper rod, the water inlet, and the mechanism seal, respectively. The first parallel nitrogen pipeline is located between the gas supply source and the stopper rod inlet. The second parallel nitrogen pipeline is located between the gas supply source and the water inlet. The third parallel nitrogen pipeline is located between the gas supply source and the sealed gas inlet of the mechanism; at the same time, Three argon gas pipelines are respectively installed between the argon gas supply source and the stopper rod, the water inlet, and the mechanism seal; A low-pressure argon gas pipeline is installed between the argon gas supply source and the stopper rod inlet. A first high-pressure argon pipeline is installed between the argon gas supply source and the water inlet. A second high-pressure argon gas pipeline is installed between the argon gas supply source and the sealed inlet of the mechanism.

6. The gas supply line system for protective gas used in continuous casting of steel according to claim 5, characterized in that: A first gas mixer is installed at the front end of the stopper rod inlet. Nitrogen and argon gas lines leading to the stopper rod inlet are introduced through the first gas mixer. A second gas mixer is installed at the front end of the water inlet air inlet. Nitrogen and argon gas pipelines leading to the water inlet air inlet are introduced through the second gas mixer.

7. The gas supply line system for protective gas used in continuous casting of steel according to claim 5, characterized in that: The first high-pressure argon gas pipeline and the second high-pressure argon gas pipeline are connected in parallel. The low-pressure argon gas pipeline and the parallel pipeline consisting of the first high-pressure argon gas pipeline and the second high-pressure argon gas pipeline are set up independently. or The first high-pressure argon gas pipeline and the second high-pressure argon gas pipeline are connected in parallel, and then connected in parallel with the low-pressure argon gas pipeline.

8. The gas supply line system for protective gas used in continuous casting of steel according to claim 5, characterized in that: A nitrogen-argon switching solenoid valve is installed at the front end of the mechanism sealing air inlet. The nitrogen and argon pipelines leading to the mechanism sealing air inlet are connected to the mechanism sealing air inlet via the nitrogen-argon switching solenoid valve.

9. The gas supply line system for protective gas used in continuous casting of steel according to claim 8, characterized in that: On the first parallel nitrogen pipeline, the second parallel nitrogen pipeline, the low-pressure argon pipeline, the first high-pressure argon pipeline, and the pipeline between the mechanism sealing inlet and the mechanism sealing nitrogen-argon switching solenoid valve, each has its own main flow control setting and bypass branch flow control setting.

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