Gas furnace and control method for reducing heating oxidation of forgings

Abstract

The application discloses a gas furnace for reducing forging heating oxidation and a control method. The gas furnace comprises a furnace body, a burner unit, a natural gas supply unit, a combustion-supporting air supply unit, a detection system and a control system. The furnace body is provided with multiple temperature control zones. The burner unit comprises multiple burners. The natural gas supply unit is connected with the burner unit to provide natural gas for the burner unit. The combustion-supporting air supply unit is connected with the burner unit to provide combustion-supporting air for the burner unit. The detection system comprises a temperature detection unit and an oxygen content detection unit. The temperature detection unit is used for monitoring the temperature of each temperature control zone. The oxygen content detection unit is used for monitoring the oxygen content in flue gas discharged from the flue gas pipeline of the furnace body. The control system is electrically connected with the natural gas supply unit, the combustion-supporting air supply unit and the detection system. The control system is used for automatically regulating the natural gas flow and the combustion-supporting air flow according to the temperature data and the oxygen content data. The application has the advantage of improving the forging oxidation inhibition effect.

Description

Technical Field

[0001] This application relates to the field of metal forging technology, and in particular to a gas furnace and control method for reducing the oxidation of forgings during heating. Background Technology

[0002] Before forging, forgings need to be heated in a furnace. During this process, the metal surface reacts with oxygen in the furnace atmosphere to form an oxide scale. This not only directly leads to metal burn-off and increases production costs, but more importantly, the detached oxide scale exacerbates die wear, damages the surface quality of the forgings, and can even cause product scrap. Therefore, suppressing the oxidation reaction during the heating process has long been one of the key objectives pursued in forging heating technology.

[0003] Specifically, the heating process generally consists of two stages: heating and holding. During the heating stage, to rapidly increase the furnace temperature, the control system typically introduces excessive combustion air to ensure complete fuel combustion. This results in a high oxygen partial pressure within the furnace, creating conditions conducive to severe oxidation of the forging surface. In the holding stage, the forging has reached the target temperature, and the primary challenge shifts from "rapid heating" to "uniform holding and reducing oxidation." However, existing control strategies often fail to adjust the air-fuel ratio in a timely and effective manner, leaving the residual oxygen content in the furnace still high and oxidation reactions continuing. This stage is not effectively utilized for oxidation suppression. Summary of the Invention

[0004] The main objective of this application is to provide a gas-fired furnace and control method for reducing oxidation of forgings during heating, aiming to solve the technical problem that existing heating furnaces have poor effect on inhibiting oxidation of forgings.

[0005] To achieve the above objectives, this application provides a gas-fired furnace for reducing oxidation during forging heating, comprising a furnace body, a burner unit, a natural gas supply unit, a combustion air supply unit, a detection system, and a control system. The furnace body has multiple temperature control zones. The burner unit includes multiple burners, with multiple burners arranged on both sides of the furnace body. The natural gas supply unit is connected to the burner unit to supply natural gas. The combustion air supply unit is connected to the burner unit to supply combustion air. The detection system includes a temperature detection unit and an oxygen content detection unit. The temperature detection unit monitors the temperature of each temperature control zone, and the oxygen content detection unit monitors the oxygen content in the flue gas discharged from the furnace body's flue gas duct. The control system is electrically connected to the natural gas supply unit, the combustion air supply unit, and the detection system, and automatically adjusts the natural gas flow rate and the combustion air flow rate based on the temperature and oxygen content data.

[0006] Optionally, the natural gas supply unit includes a main gas pipeline, on which a first shut-off valve, a proportional regulating valve, and a pressure fine-tuning proportional valve are connected in sequence, and the pressure fine-tuning proportional valve is connected to the burner unit.

[0007] Optionally, the combustion air supply unit includes a combustion air fan driven by a frequency converter, the combustion air fan is connected to a main combustion air duct, and a second shut-off valve is installed on the main combustion air duct.

[0008] To achieve the above objectives, this application also provides a control method for controlling the aforementioned gas-fired furnace for reducing oxidation during forging heating, including heating stage control and holding stage control, wherein the holding stage control includes oxygen content adjustment, which specifically includes the following steps:

[0009] Obtain the actual oxygen content Q1 collected by the oxygen content detection unit;

[0010] Obtain the deviation value e0 between the actual oxygen content Q1 and the preset target oxygen content threshold Q2, e0=Q1-Q2;

[0011] Input the deviation value e0 into the preset PID control model to obtain the natural gas flow regulation amount;

[0012] According to the natural gas flow rate adjustment amount and adjustment rules, the natural gas flow rate of the natural gas supply unit is dynamically adjusted so that the actual oxygen content Q1 approaches the target oxygen content threshold Q2; wherein, the adjustment rules are: if e0>0, the natural gas flow rate is slightly increased, and if e0<0, the natural gas flow rate is slightly decreased.

[0013] Optionally, the expression for the PID control model is:

[0014]

[0015] In the formula, Δ Q gas For natural gas flow regulation, K p , K i and K d These are all PID parameters.

[0016] Optionally, the natural gas flow rate of the dynamically adjusted natural gas supply unit is adjusted in multiple stages, with the magnitude of each adjustment satisfying the following formula:

[0017] |Δ Q gas |≤0.02*Q';

[0018] In the formula, Q' represents the current natural gas flow rate.

[0019] Optionally, the heat preservation stage control also includes furnace temperature uniformity adjustment, which specifically includes the following steps:

[0020] The temperature detection unit acquires the temperatures T1 and T2 corresponding to two preset temperature measurement points in each temperature control zone;

[0021] Determine whether the temperature deviation value ΔT is greater than the preset temperature deviation threshold ΔT'. If so, adjust the pulse time distribution of the left and right burners in the corresponding temperature control zone; where ΔT = |T1 - T2|.

[0022] Obtain the average temperature value for each temperature control zone, and filter out the maximum value T among multiple average temperature values. max and minimum value T min To obtain the maximum temperature difference value ΔT max ; where ΔT max =T max -T min ;

[0023] Determine the maximum temperature difference ΔT max Is it greater than the preset temperature difference threshold ΔT'? max If so, oxygen content adjustment is paused, and temperature uniformity is restored by adjusting the pulse distribution of each burner or the total natural gas flow rate until the temperature uniformity meets the standard before resuming oxygen content adjustment.

[0024] Optionally, the insulation stage control also includes basic heat load adjustment, which specifically includes the following steps:

[0025] Obtain the measured temperature T3 collected by the temperature detection unit;

[0026] Obtain the deviation value e between the measured temperature T3 and the preset target insulation temperature T4. t ;

[0027] For the deviation value e t Perform PID calculations to obtain analog signals;

[0028] Based on the analog signal, the output frequency of the natural gas supply unit and the combustion air supply unit is controlled to dynamically adjust the total natural gas input and the total combustion air flow to maintain the basic heat load.

[0029] Optionally, the temperature rise stage control includes the following steps:

[0030] Obtain the heating command and the target insulation temperature T4;

[0031] According to the preset heating power curve, the natural gas flow rate and combustion air flow rate are controlled at a level that can maintain an oxygen-rich state.

[0032] The temperature T3 inside the furnace is collected in real time by the temperature detection unit. When the preset conditions are met, it is determined that the furnace has entered the heat preservation stage.

[0033] Optionally, the preset conditions include: the measured temperature T3 is monitored to reach 99% of the target insulation temperature T4, and this state is maintained stably for a preset time t1.

[0034] Optionally, it also includes safety interlock controls, which include:

[0035] Parameters are monitored during the heating and heat preservation phases to immediately shut off the natural gas supply unit and the combustion air supply unit when a safety shutdown condition is triggered.

[0036] Optionally, the safe stop conditions include:

[0037] The temperature detection unit collects the actual temperature inside the furnace in real time, T3 > 1220℃;

[0038] The gas pressure in the natural gas supply unit is lower than the preset lower limit or higher than the preset upper limit.

[0039] The combustion air supply unit stopped operating due to a malfunction;

[0040] The combustion air pressure of the combustion air supply unit is lower than the preset lower limit of air pressure.

[0041] Optionally, it also includes shutdown control, which includes the following steps:

[0042] Obtain the heat preservation duration during the heat preservation stage. If the heat preservation duration reaches a preset time threshold, obtain the heating end signal.

[0043] Based on the heating end signal, the control system executes a shutdown command; the shutdown command first shuts down the natural gas supply unit, and then shuts down the combustion air supply unit after a preset time t2.

[0044] The beneficial effects that this application can achieve are as follows:

[0045] The detection system described in this application includes a temperature detection unit and an oxygen content detection unit. The temperature detection unit can monitor the temperature of each temperature control zone inside the furnace, while the oxygen content detection unit can monitor the oxygen content in the flue gas discharged from the flue gas duct of the furnace. Thus, based on the changes in temperature and oxygen content data, the system can coordinately control the natural gas supply unit and the combustion air supply unit to automatically regulate the flow rate of natural gas and the flow rate of combustion air. This allows the oxygen content inside the furnace to be precisely controlled at a low level (0~1%) during the heat preservation stage, creating a weak oxidizing atmosphere, effectively inhibiting oxidation reactions, and improving the quality of forgings. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0047] Figure 1 This is a schematic diagram of the structure of a gas furnace for reducing oxidation during heating of forgings, as described in an embodiment of this application.

[0048] Figure 2 This is a flowchart illustrating a control method in an embodiment of this application.

[0049] Figure label:

[0050] 1-Furnace body, 2-Burner unit, 3-Natural gas supply unit, 4-Combustion air supply unit, 5-Detection system, 6-Safety interlock unit.

[0051] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0052] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0053] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationship and movement of each component in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0054] In this application, unless otherwise expressly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral part; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0055] Furthermore, if the embodiments of this application involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed in this application.

[0056] Example 1

[0057] Reference Figure 1 This embodiment provides a gas-fired furnace for reducing oxidation during forging heating, including a furnace body 1, a burner unit 2, a natural gas supply unit 3, a combustion air supply unit 4, a detection system 5, and a control system. The furnace body 1 has multiple temperature control zones. The burner unit 2 includes multiple burners, with multiple burners arranged on both sides of the furnace body 1. The natural gas supply unit 3 is connected to the burner unit 2 to supply natural gas. The combustion air supply unit 4 is connected to the burner unit 2 to supply combustion air. The detection system 5 includes a temperature detection unit and an oxygen content detection unit. The temperature detection unit monitors the temperature of each temperature control zone, and the oxygen content detection unit monitors the oxygen content in the flue gas discharged from the flue gas duct of the furnace body 1. The control system is electrically connected to the natural gas supply unit 3, the combustion air supply unit 4, and the detection system 5. The control system automatically adjusts the natural gas flow rate and the combustion air flow rate based on the temperature and oxygen content data.

[0058] In this embodiment, the detection system 5 includes a temperature detection unit and an oxygen content detection unit. The temperature detection unit can monitor the temperature of each temperature control zone in the furnace body 1, and the oxygen content detection unit can monitor the oxygen content in the flue gas discharged from the flue gas duct of the furnace body 1. Thus, based on the changes between temperature data and oxygen content data, the natural gas supply unit 3 and the combustion air supply unit 4 can be controlled in a coordinated manner to automatically adjust the natural gas flow rate and the combustion air flow rate. This allows the oxygen content in the furnace body 1 to be precisely controlled at a low level (0~1%) during the heat preservation stage, creating a weak oxidizing atmosphere, effectively inhibiting oxidation reaction, and improving the quality of forgings.

[0059] It should be noted that the furnace body 1 has a sealed heating chamber, and the refractory layer inside the furnace body 1 is integrally cast with refractory castable, providing good thermal insulation. High-speed burners can be used, arranged on both sides of the furnace chamber inside the furnace body 1, 500mm above the forgings, to prevent the flame from directly impacting the forging surface. The burners are connected to the combustion air inlet, flue gas outlet, and natural gas inlet, respectively. The gas inlet end of each burner is welded to a branch pipe of the gas distribution pipe, and the combustion air inlet end is connected to the flange of a branch pipe of the combustion air distribution pipe. The temperature detection unit can use S-type thermocouples. For example, the furnace chamber can be divided into four temperature control zones, with two S-type thermocouples installed in each zone, for a total of eight. The S-type thermocouples are installed away from the direct flame impact zone and are used to monitor the temperature of each temperature control zone in real time. The signal output end of the S-type thermocouples is connected to the temperature controller via a compensating wire. The oxygen content detection unit can employ a laser online flue gas analyzer, installed on the flue gas duct at the furnace outlet. This location representatively reflects the furnace atmosphere while avoiding strong airflow disturbances. It is used for real-time monitoring of the oxygen content (O2 concentration) in the flue gas. The sampling tube of the laser online flue gas analyzer is inserted into the center of the flue, and its signal output is connected to the control system via a shielded cable. The control system is based on a Siemens S7-1500 series PLC and is electrically connected to all electrical components in the natural gas supply unit 3, the combustion air supply unit 4, and the detection system 5.

[0060] As an optional implementation, the natural gas supply unit 3 includes a main gas pipeline, on which a first shut-off valve, a proportional regulating valve, and a pressure fine-tuning proportional valve are connected in sequence, and the pressure fine-tuning proportional valve is connected to the burner unit 2.

[0061] In this embodiment, the first shut-off valve can be a VAS type pneumatic shut-off valve, and the proportional regulating valve can be a GIK type mechanical proportional regulating valve. The sampling port of the GIK type mechanical proportional regulating valve can be connected to the main combustion air pipeline through a Φ10 copper pipe to achieve the pre-setting of the air-fuel ratio of gas and combustion air. The pressure fine-tuning proportional valve is installed downstream of the GIK type mechanical proportional regulating valve and is used to receive electrical signals from the control system to finely adjust the gas flow. The output of the pressure fine-tuning proportional valve can be delivered to the gas inlet of each burner through the gas pipeline. Through the coordinated operation of the first shut-off valve, the proportional regulating valve, and the pressure fine-tuning proportional valve, the precise control of the fuel ratio can be achieved.

[0062] It should be noted that a gas filter can also be installed between the first shut-off valve and the proportional regulating valve to intercept impurities and output clean gas.

[0063] As an optional implementation, the combustion air supply unit 4 includes a combustion air fan driven by a frequency converter, the combustion air fan is connected to a main combustion air duct, and a second shut-off valve is installed on the main combustion air duct.

[0064] In this embodiment, the frequency converter in the combustion fan can receive a 4-20mA analog signal from the control system, thereby precisely adjusting the air pressure and flow rate of the combustion fan by changing the speed of the combustion fan.

[0065] It should be noted that the combustion air blower outlet is connected to a combustion air filter. The output of the combustion air filter is delivered to the combustion air pipeline, and then connected to a T-connector. One end of the T-connector is connected to the downstream of the main combustion air pipeline, and the other end is connected to the outlet of the cooling air blower, which is then connected to the combustion air distribution pipe. Finally, it is connected to the combustion air inlet of each burner. The frequency converter is connected to the combustion air blower motor via a cable.

[0066] As an optional implementation, a safety interlock unit 6 is also included. The safety interlock unit 6 includes a gas pressure switch, a combustion air pressure switch, a furnace over-temperature switch, an emergency stop button, and an audible and visual alarm. The gas pressure switch's pressure tap is connected to the main gas pipeline and is located downstream of the first shut-off valve. The combustion air pressure switch's pressure tap is connected to the main combustion air pipeline and connected to the outlet pipeline of the combustion air fan. The furnace over-temperature switch's temperature-sensitive end is installed in the temperature-sensitive area of ​​the furnace inner wall. The emergency stop button and the audible and visual alarm are both installed on the operation panel. The gas pressure switch, combustion air pressure switch, furnace over-temperature switch, and emergency stop button are all connected to the PLC's digital input module via shielded control cables. The audible and visual alarm is connected to the PLC's digital output module via the same shielded control cable. When any interlock condition is triggered, the PLC immediately outputs a signal to cut off the flow shut-off valves (including the first and second shut-off valves) and the emergency shut-off solenoid valve to block the gas passage, stop the combustion air fan and the cooling fan to stop the supply of combustion air and cold air, and activate the audible and visual alarm to issue a warning.

[0067] Existing technologies have made some attempts to improve the combustion atmosphere, but none of them have fundamentally solved the above problems:

[0068] For example, patent CN201120402670 proposes to regulate combustion by analyzing multiple components in flue gas (such as O2, CO / CO2, H2). However, this method relies on a complex and expensive flue gas analysis system, resulting in high implementation costs. Furthermore, its control logic is global and fails to provide fine-grained, staged control tailored to the characteristics of different stages of forging heating.

[0069] For example, patent CN201510010406 ​​attempts to monitor residual oxygen at the burner to adjust airflow, but its adjustment mechanism is a slow-responding, gradual adjustment that is difficult to respond quickly to dynamically changing furnace conditions. More importantly, this solution only focuses on local oxygen content and does not coordinate it with the overall temperature uniformity control of the furnace, which may lead to sacrificing heating quality in order to reduce oxidation.

[0070] Another approach, such as CN202510413760, aims at environmental protection and emission reduction by using nitrogen-free combustion air to reduce nitrogen oxide generation. While this approach may indirectly affect the atmosphere, it is not designed for controlling oxide scale on forgings, and its system configuration is extremely complex and costly to modify, making it unsuitable for ordinary industrial gas furnaces.

[0071] Looking at existing technologies, the field has long faced an unresolved technical dilemma in achieving efficient and high-quality forging heating: how to suppress oxide scale formation without compromising heating efficiency and furnace temperature uniformity. This dilemma manifests itself in the following key technical bottlenecks:

[0072] Lack of control dimension: Existing systems generally lack the ability to perceive and control the key parameter of actual oxygen content inside the furnace in real time, resulting in insufficient basis for control decisions.

[0073] The control strategy is crude: it fails to design a differentiated atmosphere control strategy that matches the different core requirements of the two stages of "heating" and "heat holding" in the heating process.

[0074] Single control objective: Existing atmosphere optimization attempts are often independent of or even conflict with temperature control loops, making it impossible to achieve synergistic optimization of oxygen content and furnace temperature uniformity.

[0075] High technical implementation threshold: It relies on complex solutions involving multi-sensor fusion or special media (such as nitrogen-free air), making the system complex and costly, and difficult to achieve widespread application in conventional gas furnaces with a large number of applications.

[0076] Based on this, the following embodiments provide an innovative control method that breaks through the traditional single-temperature-dimensional control paradigm. Under the premise of strictly ensuring heating efficiency and furnace temperature uniformity, it achieves precise staged control of oxygen content in the furnace through a simple, reliable and easy-to-implement means, thereby significantly inhibiting forging oxidation.

[0077] Example 2

[0078] Reference Figures 1-2 This embodiment provides a control method for controlling a gas furnace in the above embodiment that reduces oxidation during forging heating. The method includes heating stage control and holding stage control. The holding stage control includes oxygen content adjustment, which specifically includes the following steps:

[0079] Obtain the actual oxygen content Q1 collected by the oxygen content detection unit;

[0080] Obtain the deviation value e0 between the actual oxygen content Q1 and the preset target oxygen content threshold Q2, e0=Q1-Q2;

[0081] Input the deviation value e0 into the preset PID control model to obtain the natural gas flow regulation amount;

[0082] According to the natural gas flow rate adjustment amount and adjustment rules, the natural gas flow rate of the natural gas supply unit is dynamically adjusted so that the actual oxygen content Q1 approaches the target oxygen content threshold Q2; wherein, the adjustment rules are: if e0>0, the natural gas flow rate is slightly increased, and if e0<0, the natural gas flow rate is slightly decreased.

[0083] In this embodiment, the actual oxygen content Q1 in the flue gas can be collected in real time by the laser online flue gas analyzer of the oxygen content detection unit and transmitted to the control system. The control system calculates the oxygen content deviation value e0 = Q1 - Q2, for example, Q2 = 1% vol. Based on the deviation value e0, the control system uses a PID algorithm to calculate the natural gas flow adjustment amount, thereby adjusting the opening of the pressure fine-tuning proportional valve to dynamically change the natural gas flow, so that the actual oxygen content Q1 approaches the target oxygen content threshold Q2, ultimately achieving precise adjustment of the oxygen content. Therefore, this embodiment creates a weakly oxidizing atmosphere by precisely controlling the oxygen content in the furnace at a low level (0~1%) during the heat preservation stage, effectively suppressing the oxidation reaction. Actual measurements show that the average thickness of the oxide scale on the forgings can be reduced from 3.5 mm to 1 mm, and the material burn-off rate can be reduced by about 71.4%, which is a significant effect.

[0084] The expression for the above PID control model is as follows:

[0085]

[0086] In the formula, Δ Q gas For natural gas flow regulation, K p , K i and K d These are all PID parameters.

[0087] As an optional implementation, the natural gas flow rate of the dynamically adjusted natural gas supply unit is adjusted in multiple stages, with the magnitude of each adjustment satisfying the following formula:

[0088] |Δ Q gas |≤0.02*Q';

[0089] In the formula, Q' represents the current natural gas flow rate.

[0090] In this embodiment, a small, gradual adjustment method is adopted, with the amplitude of each adjustment controlled according to the above formula. At the same time, the adjustment period can be set to 10-30 seconds, thereby improving system stability.

[0091] As an optional implementation, the heat preservation stage control also includes furnace temperature uniformity adjustment, which specifically includes the following steps:

[0092] The temperature detection unit acquires the temperatures T1 and T2 corresponding to two preset temperature measurement points in each temperature control zone;

[0093] Determine whether the temperature deviation value ΔT is greater than the preset temperature deviation threshold ΔT'. If so, adjust the pulse time distribution of the left and right burners in the corresponding temperature control zone; where ΔT = |T1 - T2|.

[0094] Obtain the average temperature value for each temperature control zone, and filter out the maximum value T among multiple average temperature values. max and minimum value T min To obtain the maximum temperature difference value ΔT max ; where ΔT max =T max -T min ;

[0095] Determine the maximum temperature difference ΔT max Is it greater than the preset temperature difference threshold ΔT'? max If so, oxygen content adjustment is paused, and temperature uniformity is restored by adjusting the pulse distribution of each burner or the total natural gas flow rate until the temperature uniformity meets the standard before resuming oxygen content adjustment.

[0096] In this embodiment, the PLC can convert the control signal into a pulse signal (the frequency of the pulse signal is 0.5~1Hz to ensure smooth switching of the burner combustion state), and cyclically control the combustion state (high flame / low flame / off flame) of each high-speed burner. By adjusting the pulse duty cycle, the power output of each burner is precisely controlled. Then, the temperature detection unit detects the temperatures T1 and T2 corresponding to two preset temperature measuring points (i.e., two S-type thermocouples) in each temperature control zone. If the system determines that ΔT=|T1-T2|>ΔT' (temperature deviation threshold), it can automatically adjust the pulse time distribution of the left and right burners in that zone. For example, if the temperature of the left burner is higher, the combustion time of the left burner is reduced. At the same time, the system can monitor the maximum temperature difference ΔT in multiple temperature control zones within the furnace body 1. max ΔT max It is the maximum value T among the average temperature values ​​of each temperature control zone. max and minimum value T min The difference is calculated to characterize the temperature difference range of each temperature control zone. If the maximum temperature difference value ΔT max Greater than the preset temperature difference threshold ΔT' maxIf the temperature is not uniform, the oxygen content regulation function is immediately suspended, and temperature uniformity is restored by adjusting the pulse distribution of each burner or the total natural gas flow. Oxygen content regulation is then resumed once the temperature uniformity meets the standard. Throughout this process, the PLC's intelligent pulse program continuously operates, cyclically controlling the start-up and shutdown sequence of the burners in each temperature control zone, and fine-tuning the power of each burner in real time based on temperature feedback from each temperature control zone to ensure that the furnace temperature uniformity meets ΔT. max ≤ΔT' max If the temperature difference in a certain area is too large (ΔT) due to oxygen content adjustment, max >ΔT' max The system prioritizes adjusting the burner pulse to restore uniformity. When heating ends, the system shuts off all valves and fans, completing the task.

[0097] Therefore, during the heat preservation stage, while reducing the oxygen content, the intelligent pulse control ensures excellent furnace temperature uniformity (temperature difference at each point ≤ ±10℃), ensuring the heating quality of the forgings. Based on multi-point real-time feedback of oxygen content and temperature, closed-loop control is implemented, reducing manual intervention and providing good control accuracy and stability.

[0098] As an optional implementation method, the insulation stage control also includes basic heat load adjustment, which specifically includes the following steps:

[0099] Obtain the measured temperature T3 collected by the temperature detection unit;

[0100] Obtain the deviation value e between the measured temperature T3 and the preset target insulation temperature T4. t ;

[0101] For the deviation value e t Perform PID calculations to obtain analog signals;

[0102] Based on the analog signal, the output frequency of the natural gas supply unit and the combustion air supply unit is controlled to dynamically adjust the total natural gas input and the total combustion air flow to maintain the basic heat load.

[0103] In this embodiment, the deviation value e between the measured temperature T3 and the preset target insulation temperature T4 is monitored in real time. t and the deviation value e t By performing PID calculations, an analog signal can be obtained. Based on this analog signal, the output frequency of the natural gas supply unit and the combustion air supply unit can be controlled, that is, the opening of the GIK type mechanical proportional regulating valve and the output frequency of the frequency converter in the combustion air fan can be controlled. This allows for dynamic adjustment of the total natural gas input and the total combustion air flow, thereby maintaining the basic heat load to ensure stable furnace temperature.

[0104] As an optional implementation, the temperature rise stage control includes the following steps:

[0105] Obtain the heating command and the target insulation temperature T4;

[0106] According to the preset heating power curve, the natural gas flow rate and combustion air flow rate are controlled at a level that can maintain an oxygen-rich state.

[0107] The temperature T3 inside the furnace is collected in real time by the temperature detection unit. When the preset conditions are met, it is determined that the furnace has entered the heat preservation stage.

[0108] In this embodiment, during the heating stage, based on the heating command, the target insulation temperature T4, and the heating power curve, the natural gas flow rate and combustion air flow rate are controlled at a high level to ensure sufficient fuel and oxygen supply, thereby achieving rapid heating of the furnace. During this stage, a certain oxygen-rich state is maintained to ensure complete combustion and heating speed. At the same time, the measured temperature T3 is collected in real time by the S-type thermocouple of the temperature detection unit and transmitted to the control system. When the measured temperature T3 reaches 99% of the target insulation temperature T4 (i.e., T3≥99%T4) and this state is stably maintained for a preset time t1 (e.g., 2 minutes), the system can automatically determine to enter the insulation stage and thus enter the control program for the insulation stage.

[0109] As an optional implementation, a safety interlock control is also included, which includes:

[0110] During the heating and heat preservation stages, parameters are monitored to immediately cut off the natural gas supply unit 3 and the combustion air supply unit 4 when a safety shutdown condition is triggered, so as to ensure the safe operation of the gas furnace.

[0111] As an optional implementation, the safety stop conditions include:

[0112] Over-temperature stop: The actual temperature T3 inside furnace body 1, collected in real time by the temperature detection unit, is greater than 1220℃;

[0113] Gas pressure abnormality stop: The gas pressure of natural gas supply unit 3 is lower than the preset lower limit (e.g., 0.02MPa) or higher than the preset upper limit (e.g., 0.1MPa).

[0114] Fan failure shutdown: Combustion air supply unit 4 stopped operating due to a malfunction;

[0115] Combustion air pressure abnormally stopped: The combustion air pressure of combustion air supply unit 4 is lower than the preset lower limit of air pressure (e.g., 0.015MPa).

[0116] Therefore, setting safe shutdown conditions based on monitoring of multiple parameters can effectively ensure the operational safety of the gas furnace.

[0117] As an optional implementation, a shutdown control is also included, which comprises the following steps:

[0118] Obtain the heat preservation duration during the heat preservation stage. If the heat preservation duration reaches a preset time threshold, obtain the heating end signal.

[0119] Based on the heating end signal, the control system executes a shutdown command; the shutdown command first shuts down the natural gas supply unit 3, and then shuts down the combustion air supply unit 4 after a preset time t2 (e.g., 10-30 seconds).

[0120] In this embodiment, after the heat preservation period lasts for a certain time, a heating end signal can be automatically obtained. The control system can then execute a shutdown command based on this signal, first shutting down the natural gas supply unit 3, and then shutting down the combustion air supply unit 4 after an interval of time t2, to ensure safety.

[0121] Comparative Example 1: Conventional heating method using a common gas furnace

[0122] To demonstrate the significant advancements of this invention, this comparative example is provided. A conventional gas furnace with the same furnace size and rated power as the gas furnace of this invention, but employing a traditional control method, is used for the comparative test.

[0123] This proportional control method uses a fixed air-fuel ratio for combustion, lacks online oxygen content detection and closed-loop control, and lacks zoned intelligent pulse temperature control to ensure furnace temperature uniformity. Its system configuration does not include... Figure 1 The system includes a pressure fine-tuning proportional valve, a combustion fan with a frequency converter, a laser online flue gas analyzer, and core control logic.

[0124] To ensure the fairness and scientific rigor of the comparison, the experiment was designed as follows:

[0125] Identical workpieces: steel forgings from the same manufacturer and made of the same material, with identical specifications and furnace loading quantities;

[0126] Same target temperature: The target heating temperature is 1200℃;

[0127] Same fuel: Natural gas that uses the same gas source;

[0128] Same total heating time: The total heating time remains the same.

[0129] Heating process of Comparative Example 1: The ordinary gas furnace operates at a fixed air-fuel ratio. In order to reach and maintain the target temperature, the supply of combustion air is relatively sufficient throughout the process, resulting in a high oxygen atmosphere inside the furnace. Operators can only make manual fine adjustments through observation and experience, and cannot effectively intervene in the oxidizing atmosphere inside the furnace. The furnace temperature fluctuates greatly and has poor uniformity.

[0130] The results are as follows:

[0131] Average oxide scale thickness of forgings: 3.5 mm;

[0132] Material burn-off rate: 2.8%;

[0133] Maximum temperature difference in the four zones of the furnace: 30°C;

[0134] Natural gas consumption per unit time: 400m³ 3 / h;

[0135] Example 2 Heating Process: As described in this example, the process involves rapid heating and intelligent heat preservation. During the heat preservation stage, the system automatically and stably controls the oxygen content within the range of (1.0±0.2)%, and dynamically adjusts the power of each burner through intelligent pulse control to ensure uniform temperature.

[0136] The results are as follows:

[0137] Average oxide scale thickness of forgings: 1.0 mm;

[0138] Material burn-off rate: 0.8%;

[0139] Maximum temperature difference in the four zones of the furnace: 9°C;

[0140] Natural gas consumption per unit time: 300m³ 3 / h;

[0141] The comparison and analysis of the control schemes of Comparative Example 1 and Example 2 is shown in Table 1 below:

[0142] Table 1 Comparative Analysis Table

[0143]

[0144] As can be seen from the table above, under the same experimental conditions, the average thickness of the oxide scale of the present invention is 1 mm, which is significantly improved, reducing the thickness by 71.4% compared with the comparative example; the material burn-off rate is reduced from 2.8% to 0.8%, a reduction of 71.4%; the furnace temperature difference is reduced from 40℃ to about 20℃, and the uniformity is significantly improved; while reducing oxidation, it saves about 18% of gas energy consumption. Through the comparison between the present invention and ordinary gas furnace, it can be seen that the present invention is not a simple optimization, but a systematic and innovative technical solution that can simultaneously solve the three major problems of "high oxidation burn-off", "uneven temperature" and "high energy consumption". Its technological progress and the beneficial effects it produces are outstanding, significant and unexpected.

[0145] In summary, the present invention has the following significant advantages:

[0146] Significantly reduced oxidation rate: By precisely controlling the oxygen content in the furnace to a low level (0~1%) during the holding stage, a weakly oxidizing atmosphere is created, effectively inhibiting the oxidation reaction. Actual measurements show that the average thickness of the oxide scale on forgings can be reduced from 3.5mm to 1mm, and the material burn-off rate can be reduced by approximately 71.4%.

[0147] Ensuring heating quality and efficiency: The heating stage is rapid and efficient; during the heat preservation stage, while reducing the oxygen content, intelligent pulse control ensures excellent furnace temperature uniformity (temperature difference at each point ≤ ±10℃), thus ensuring the heating quality of the forgings.

[0148] High degree of automation and intelligence: Closed-loop control based on multi-point real-time feedback of oxygen content and temperature reduces manual intervention and provides good control accuracy and stability.

[0149] High safety: It integrates multiple hard safety interlocking mechanisms, which effectively prevent production safety accidents.

[0150] Significant economic benefits: It comprehensively reduces metal burn-off, improves the surface quality of forgings, and extends the life of dies, resulting in significant economic benefits.

[0151] The above are merely preferred embodiments of this application and do not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A control method for controlling a gas-fired furnace to reduce oxidation during forging heating, characterized in that, The gas furnace includes a furnace body with multiple temperature control zones; a burner unit with multiple burners arranged on both sides of the furnace body; and a natural gas supply unit connected to the burner unit to supply natural gas to the burner unit. The combustion air supply unit is connected to the burner unit to supply combustion air to the burner unit; the detection system includes a temperature detection unit and an oxygen content detection unit. The temperature detection unit is used to monitor the temperature of each temperature control zone, and the oxygen content detection unit is used to monitor the oxygen content in the flue gas discharged from the flue gas duct of the furnace; the control system is electrically connected to the natural gas supply unit, the combustion air supply unit, and the detection system. The control system is used to automatically adjust the natural gas flow rate and the combustion air flow rate based on the temperature data and oxygen content data. The control method includes heating stage control and heat preservation stage control. The heat preservation stage control includes oxygen content adjustment, which specifically includes the following steps: Obtain the actual oxygen content Q1 collected by the oxygen content detection unit; Obtain the deviation value e0 between the actual oxygen content Q1 and the preset target oxygen content threshold Q2, e0=Q1-Q2; Input the deviation value e0 into the preset PID control model to obtain the natural gas flow regulation amount; According to the natural gas flow rate adjustment amount and adjustment rules, the natural gas flow rate of the natural gas supply unit is dynamically adjusted so that the actual oxygen content Q1 approaches the target oxygen content threshold Q2; wherein, the adjustment rule is: if e0>0, the natural gas flow rate is slightly increased, and if e0<0, the natural gas flow rate is slightly decreased. The heat preservation stage control also includes furnace temperature uniformity adjustment, which specifically includes the following steps: The temperature detection unit acquires the temperatures T1 and T2 corresponding to two preset temperature measurement points in each temperature control zone; Determine whether the temperature deviation value ΔT is greater than the preset temperature deviation threshold ΔT'. If so, adjust the pulse time distribution of the left and right burners in the corresponding temperature control zone; where ΔT = |T1 - T2|. Obtain the average temperature value for each temperature control zone, and filter out the maximum value T among multiple average temperature values. max and minimum value T min To obtain the maximum temperature difference value ΔT max ; where ΔT max =T max -T min ; Determine the maximum temperature difference ΔT max Is it greater than the preset temperature difference threshold ΔT'? max If so, oxygen content adjustment is paused, and temperature uniformity is restored by adjusting the pulse distribution of each burner or the total natural gas flow rate until the temperature uniformity meets the standard before resuming oxygen content adjustment.

2. The control method as described in claim 1, characterized in that, The expression for the PID control model is: In the formula, Δ Q gas For natural gas flow regulation, K p , K i and K d These are all PID parameters.

3. The control method as described in claim 1, characterized in that, The natural gas flow rate of the dynamically adjusted natural gas supply unit is adjusted in multiple stages, and the magnitude of each adjustment satisfies the following formula: |D Q gas |≤0.02*Q'; In the formula, Q' represents the current natural gas flow rate.

4. The control method as described in claim 1, characterized in that, The insulation stage control also includes basic heat load adjustment, which specifically includes the following steps: Obtain the measured temperature T3 collected by the temperature detection unit; Obtain the deviation value e between the measured temperature T3 and the preset target insulation temperature T4. t ; For the deviation value e t Perform PID calculations to obtain analog signals; Based on the analog signal, the output frequency of the natural gas supply unit and the combustion air supply unit is controlled to dynamically adjust the total natural gas input and the total combustion air flow to maintain the basic heat load.

5. A control method as described in claim 1 or 4, characterized in that, The temperature rise phase control includes the following steps: Obtain the heating command and the target insulation temperature T4; According to the preset heating power curve, the natural gas flow rate and combustion air flow rate are controlled at a level that can maintain an oxygen-rich state. The temperature T3 inside the furnace is collected in real time by the temperature detection unit. When the preset conditions are met, it is determined that the furnace has entered the heat preservation stage.

6. The control method as described in claim 5, characterized in that, The preset conditions include: the measured temperature T3 is monitored to reach 99% of the target insulation temperature T4, and this state is maintained stably for a preset time t1.

7. The control method as described in claim 1, characterized in that, It also includes safety interlock controls, which include: Parameters are monitored during the heating and heat preservation phases to immediately shut off the natural gas supply unit and the combustion air supply unit when a safety shutdown condition is triggered.

8. The control method as described in claim 7, characterized in that, Safe stopping conditions include: The temperature detection unit collects the actual temperature inside the furnace in real time, T3 > 1220℃; The gas pressure in the natural gas supply unit is lower than the preset lower limit or higher than the preset upper limit. The combustion air supply unit stopped operating due to a malfunction; The combustion air pressure of the combustion air supply unit is lower than the preset lower limit of air pressure.

9. The control method as described in claim 1, characterized in that, It also includes shutdown control, which includes the following steps: Obtain the heat preservation duration during the heat preservation stage. If the heat preservation duration reaches a preset time threshold, obtain the heating end signal. Based on the heating end signal, the control system executes a shutdown command; the shutdown command first shuts down the natural gas supply unit, and then shuts down the combustion air supply unit after a preset time t2.

10. The control method as described in claim 1, characterized in that, The natural gas supply unit includes a main gas pipeline, on which a first shut-off valve, a proportional regulating valve, and a pressure fine-tuning proportional valve are connected in sequence. The pressure fine-tuning proportional valve is connected to the burner unit.

11. The control method as described in claim 1, characterized in that, The combustion air supply unit includes a combustion air fan driven by a frequency converter. The combustion air fan is connected to a main combustion air duct, and a second shut-off valve is installed on the main combustion air duct.

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