Automatic re-pressing and emptying method based on RH furnace refining safety

Abstract

This invention discloses an automatic pressure-breaking method for RH furnace refining safety, belonging to the field of vacuum refining technology. The method triggers an automatic pressure-breaking program after RH furnace refining. First, the vacuum pump group automatically exits, entering a closed monitoring state. No pressure-breaking gas is actively introduced; the pressure in the vacuum chamber rises gradually, primarily relying on the gravity backflow of molten steel and the natural expansion of residual gas within the system, lasting for at least 30 seconds. The vacuum chamber pressure is monitored in real time. Only when the pressure rises above a first preset threshold (greater than 90 kPa absolute pressure) is the inlet valve opened to introduce external gas to achieve final pressure balance. After pressure balance, a pressure-breaking completion safety signal is output, forming a safety interlock with the immersion tube lifting mechanism. This invention transforms manual operation into automatic control, fundamentally eliminating the risks of molten steel splashing and suction, significantly improving safety under abnormal operating conditions, simplifying the operation process, and reducing reliance on personnel experience.

Description

Technical Field

[0001] This invention relates to the field of vacuum refining technology, specifically to an automatic repressurization and vacuum breaking method based on the safety of RH furnace refining. Background Technology

[0002] RH vacuum refining is a key process for producing high-quality steel. At the end of refining, the vacuum chamber, which is under high vacuum (e.g., 67 Pa), must be safely restored to atmospheric pressure (101 kPa); this process is called repressurization. Traditional methods typically involve directly injecting nitrogen gas to rapidly complete repressurization within 3-5 seconds. This drastic pressure change requires precise control of the immersion tube's height in the molten steel; otherwise, it can cause violent boiling and splashing of the molten steel in the ladle, and even "steel suction" through the immersion tube, seriously threatening equipment and personnel safety.

[0003] Existing technologies have recognized the risks of rapid vacuum breaking and have attempted to improve them. For example, some solutions physically limit the intake speed by adding a mechanical throttling device to the intake pipe to achieve a smoother repressurization. In addition, industry safety regulations also require that when using nitrogen to break the vacuum, the system should be equipped with an atmospheric pressure balancing valve and signal interlock to ensure that the vacuum tank cover cannot be opened or the impregnation tube cannot be removed before the pressure difference between the inside and outside of the vacuum chamber is eliminated.

[0004] However, these existing technical solutions still have significant shortcomings: (1) Reliance on manual operation and judgment: The adjustment of the throttling device often depends on the operator's experience. For novices, under the tight production rhythm, it is difficult to accurately control the timing and speed of the throttling, which makes the operation difficult and prone to accidents.

[0005] (2) Weak ability to cope with abnormal working conditions: In emergency situations such as water leakage from the top lance, there is an extreme risk of explosion when water comes into contact with high-temperature molten steel. Traditional rapid caving methods will instantly aggravate system disturbances, and safety interlocks can only provide post-event protection and cannot fundamentally reduce the risk from the caving process itself.

[0006] (3) Poor flexibility: Fixed throttling devices are difficult to adapt to the optimal cavitation requirements under different heats, different steel grades or equipment conditions (such as different degrees of erosion of immersion tubes).

[0007] Therefore, there is an urgent need for an intelligent and automated method for repressurization and air breaking to fundamentally improve the safety, reliability, and ease of operation of RH refining operations. Summary of the Invention

[0008] (a) Technical problems to be solved

[0009] The technical problem this invention aims to solve is to provide an automated repressurization and cavitation breaking method for RH furnace refining safety. This method transforms the manual operation process into a closed-loop automatic control program, achieving a smooth and controllable cavitation breaking process. It aims to completely eliminate the risks of molten steel splashing and suction, significantly reduce the explosion hazards in abnormal situations such as top lance leakage, and simplify the operation process, reducing reliance on operator experience.

[0010] (II) Technical Solution

[0011] To solve the above-mentioned technical problems, the technical solution provided by the present invention is: an automatic repressurization and cavitation breaking method based on RH furnace refining safety, comprising the following steps: Step 1: After the RH furnace refining is completed, trigger the automatic air-breaking program; Step 2: The automatic control system performs the operation of shutting down the vacuum pump group and enters the closed monitoring state. During this stage, the vacuum chamber is not actively filled with air-breaking gas. It mainly relies on the gravity backflow of molten steel and the natural process of expansion of residual gas in the system to make the pressure in the vacuum chamber rise slowly. Step 3: Monitor the pressure value inside the vacuum chamber in real time. When the pressure value rises and exceeds the first preset threshold, open the air inlet valve to introduce external gas into the vacuum chamber to complete the final pressure balance. Step 4: Once the pressure inside the vacuum chamber is balanced with the atmospheric pressure, output a safety signal indicating that the vacuum breaking process is complete.

[0012] As an improvement, the first preset threshold is an absolute pressure greater than 90 kPa.

[0013] As an improvement, the natural process phase relying on the gravity recirculation of molten steel and the expansion of residual gas within the system lasts for no less than 30 seconds.

[0014] As an improvement, the operation of the vacuum pump unit exiting operation refers to the process in which the control unit automatically controls the vacuum pump unit to stop working and close the relevant valves according to preset logic.

[0015] As an improvement, the introduced external gas is air or low-pressure nitrogen.

[0016] As an improvement, the safety signal for the completion of the cavitation breakthrough is interlocked with the impregnation tube lifting mechanism of the RH furnace. The impregnation tube lifting mechanism is only allowed to operate after receiving the signal.

[0017] As an improvement, throughout the entire process from step 2 to step 4, the control system monitors safety signals in parallel. If an abnormal operating condition signal is received, the preset safety plan is immediately activated.

[0018] An automatic repressurization and cavitation breaking control system based on an automatic repressurization and cavitation breaking method for RH furnace refining safety is characterized by comprising: Pressure sensor used to monitor the pressure inside the vacuum chamber in real time; The actuator is used to control the start and stop of the vacuum pump unit and the opening and closing of the intake valve; A control unit, wherein the control unit stores a control program configured to perform the steps of any one of claims 1 to 7.

[0019] (III) Beneficial Effects

[0020] The advantages of this invention compared to the prior art are: (1) High inherent safety: It fundamentally eliminates the phenomenon of molten steel splashing and steel suction caused by rapid pressure difference changes. Through the slow repressurization combining natural process and automatic control, the system state transitions smoothly, which greatly reduces the probability of accidents caused by physical impact.

[0021] (2) Strong risk resistance: Especially under extreme abnormal conditions such as top gun leakage, the slow repressurization process can avoid causing violent disturbances to the system, and buy critical response time for the safety interlock system (such as emergency lifting of oxygen gun and cutting off water source), effectively suppressing the formation of explosion conditions.

[0022] (3) Easy to operate and improved reliability: The complex, experience-dependent manual operation is transformed into a "one-click" automatic program, which greatly reduces the skill threshold and labor intensity of operators and reduces the possibility of human error. This allows even novices to complete the air-breaking operation safely and in a standardized manner.

[0023] (4) Energy saving and equipment friendly: The system prioritizes the use of its internal physical processes (molten steel reflux, residual gas expansion) for initial repressurization, reducing or delaying the consumption of external gases (especially nitrogen), thus achieving energy-saving benefits. At the same time, the stable pressure change reduces the mechanical impact on the refractory materials, pipes and valves of the vacuum chamber, which helps to extend the service life of the equipment.

[0024] (5) Practical verification of effectiveness: This method has been running stably on the No. 1 RH furnace of Lianggong Steel for more than three years. During this period, no splashing, steel suction or safety accidents caused by the breaking process have occurred, which proves its excellent practicality and reliability. Detailed Implementation

[0025] The invention will now be described in further detail with reference to specific embodiments, but this should not be construed as limiting the scope of the subject matter of the invention to the following embodiments.

[0026] The present invention will be further described in detail below with reference to specific embodiments. This embodiment takes a modern RH furnace equipped with a programmable logic controller or a distributed control system as an example.

[0027] The system used to implement this method in the embodiments includes: Detection unit: High-precision vacuum pressure transmitter with a range of 0-101 kPa, installed on the top of the vacuum chamber or on the pumping pipe, used for real-time monitoring of pressure value P; Actuation unit: vacuum pump unit and its inlet valve, air or nitrogen inlet regulating valve, pneumatic or electric actuator; Control unit: PLC or DCS, which internally stores the automatic control program described in this invention.

[0028] The specific execution flow of the automatic control program is as follows: 1. Startup phase: The program starts after receiving the start command for breaking through the void.

[0029] 2. Natural Pressure Recovery Monitoring Stage: The control unit quickly stops all vacuum pumps and closes relevant valves, sealing the vacuum chamber. During this stage, no gas is actively introduced into the vacuum chamber. The pressure rises gradually due to the natural return of molten steel to the ladle via the downcomer under gravity, the expansion of trace gases not completely removed during refining, gases released from refractory materials, and circulating gases from the molten steel as the pressure recovers. The control unit reads the pressure transmitter value P in real time and monitors its rise.

[0030] 3. Threshold Judgment and Inflation Stage: The control unit compares the real-time pressure value P with a preset first pressure threshold (e.g., 90 kPa). Only when P > 90 kPa, the program outputs a command to slowly open the air intake regulating valve, injecting air or low-pressure nitrogen into the vacuum chamber at a small flow rate. The setpoint for the inflation flow rate can be adjusted using PID control based on the P value, aiming to make the pressure steadily approach atmospheric pressure. Once the pressure returns to atmospheric pressure, the control unit immediately closes the main vacuum valve, cutting off the direct connection between the vacuum chamber and the vacuum pump unit.

[0031] 4. Completion and Signal Output Stage: Once the pressure value P stabilizes near the local atmospheric pressure (e.g., 100 kPa) and remains stable for a certain period (e.g., 2 seconds), the program determines that cavitation has been completed. The control unit sends a "cavitation complete" digital signal to the RH furnace main control system. This signal serves as one of the necessary conditions for allowing the impregnation tube to be lowered to a safe height (e.g., 400 mm), forming a safety interlock.

[0032] 5. Safety Interlock and Anomaly Handling Phase: Throughout the entire air-breaking process, the control system monitors safety signals in parallel (such as cooling water flow difference alarm, top gun leakage signal, etc.). Once an emergency signal such as "top gun leakage" is received, the system will pop up a confirmation button on the main control system. After confirming the problem, regardless of the step the program has reached, the preset safety plan will be activated immediately, all intake valves will be closed, and the highest level of safety measures will be triggered to prevent the accident from escalating.

[0033] Key parameter descriptions: First pressure threshold (90 kPa): This is the core control point of this invention. This value is set based on extensive practical experience, ensuring that the pressure difference between the inside and outside of the vacuum chamber is insufficient to drive violent flow or splashing of molten steel. Depending on the specific production line and steel grade, it can be fine-tuned within the range of 88-95 kPa.

[0034] The duration of the natural repressurization stage depends on the specific furnace conditions and is typically 30 seconds to 2 minutes. This is much longer than the traditional 3-5 second venting time, which is key to achieving safety.

[0035] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0036] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents. In short, if those skilled in the art are inspired by these claims and design similar structural methods and embodiments without departing from the inventive spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. An automatic re-pressing and emptying method based on RH furnace refining safety, characterized in that, The method comprises the following steps: Step 1: after the end of RH furnace refining, an automatic breaking-vacuum program is triggered; Step 2: the automatic control system performs an operation of turning off the vacuum pump set and entering a closed monitoring state, in which stage, no breaking-vacuum gas is actively filled into the vacuum chamber, and mainly depending on the natural process of molten steel gravity backflow and residual gas expansion in the system to make the pressure in the vacuum chamber rise gently; Step 3: the pressure value in the vacuum chamber is monitored in real time, and when the pressure value is monitored to rise and exceed a first preset threshold value, the gas inlet valve is opened to introduce external gas into the vacuum chamber to complete the final pressure balance; Step 4: after the pressure in the vacuum chamber is balanced with the atmospheric pressure, a safety signal of breaking-vacuum completion is output.

2. The method according to claim 1, wherein, The first preset threshold value is an absolute pressure greater than 90 kPa.

3. The method according to claim 1, wherein, The duration of the stage of depending on the natural process of molten steel gravity backflow and residual gas expansion in the system is not less than 30 seconds.

4. The method according to claim 1, wherein, The operation of turning off the vacuum pump set refers to a process of automatically controlling the vacuum pump set to stop working and close related valves by the control unit according to a preset logic.

5. The method according to claim 1, wherein, The introduced external gas is air or low-pressure nitrogen.

6. The method according to claim 1, wherein, The safety signal of breaking-vacuum completion forms a safety interlock with the immersion tube lifting mechanism of the RH furnace, and only after receiving the signal, the immersion tube lifting mechanism is allowed to act.

7. The method according to claim 1, wherein, During the whole process of steps 2 to 4, the control system monitors the safety signal in parallel, and if an abnormal working condition signal is received, a preset safety plan is started immediately.

8. The automatic repressing and breaking vacuum control system based on the automatic repressing and breaking vacuum method for RH furnace refining safety according to any one of claims 1-7, characterized in that, It comprises: a pressure sensor for monitoring the pressure in the vacuum chamber in real time; an actuator for controlling the start and stop of the vacuum pump set and the opening and closing of the gas inlet valve; a control unit, wherein the control unit stores a control program, and the control program is configured to perform the steps of any one of claims 1 to 7.