Defatting sintering furnace and gas control method thereof

Abstract

The application discloses a defatting sintering furnace and a gas control method thereof, and relates to the field of heat treatment equipment.The technical scheme points of the defatting sintering furnace are as follows: a double-mode inert gas supply system and an independent air supplement system.The inert gas supply system comprises a first pressure supplement pipeline in communication with a furnace bottom, which is used for rapidly replacing air from bottom to top; and a second pressure supplement pipeline in communication with a suction inlet of a centrifugal fan of a hot air circulation system, which is used for forcibly pre-mixing the supplement gas and the circulating hot air.The independent air supplement system is used for accurately supplementing trace oxygen-containing gas.Through the above-mentioned cooperative design, the defatting sintering furnace not only realizes efficient gas replacement and shortens a process cycle, but also maintains extremely high temperature field uniformity by eliminating thermal shock in the air supplement process, improves product yield, and can construct controllable composite process gas to execute advanced sintering processes such as interface modification, and fundamentally improves product performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of heat treatment equipment, in particular to a debinding sintering furnace and a gas control method thereof. BACKGROUND

[0002] With the rapid development of new energy industry, the demand for high-performance substrates is increasing. In particular, in the field of solid-state batteries, energy storage elements and other related fields, a composite substrate foil is generally used. This substrate foil is usually composed of a metal aluminum foil and a functional coating material. In its preparation process, a functional coating containing an organic binder is usually coated on the surface of the metal substrate, and then through a heat treatment process, it becomes a final product with stable structure and excellent performance.

[0003] The heat treatment process usually includes two core stages:

[0004] First, the low-temperature debinding stage, at a lower temperature, the organic binder in the substrate foil is completely removed to avoid carbonization during subsequent high-temperature processing and affect product performance;

[0005] Second, the high-temperature sintering stage, which needs to be close to the melting point of aluminum to make the coating material and the aluminum foil substrate achieve firm physical combination, while not damaging the aluminum foil itself. Promote the functional coating material and the metal substrate to achieve firm physical combination and densification, thereby giving the substrate foil the required electrical or physical and chemical properties.

[0006] In the prior art, for such precise heat treatment that needs to strictly control the gas at high temperature, a vacuum furnace is usually used. Although the vacuum furnace can provide a very high-purity processing environment, its equipment cost is high, the production efficiency is low, and it is usually intermittent production, which is difficult to meet the needs of large-scale and continuous production, resulting in high production cost.

[0007] And in terms of achieving and maintaining high-temperature inert gas, the conventional method is to fill a large amount of argon into the furnace body before heating to replace air, however, during the high-temperature sintering process, the inert gas at room temperature directly enters the high-temperature furnace, which can cause a sharp fluctuation in local temperature, thereby destroying the uniformity and stability of the furnace temperature field. SUMMARY

[0008] The purpose of the present application is to provide a debinding sintering furnace, which has the dual advantages of maintaining high temperature field uniformity during dynamic gas replenishment and accurately controlling the concentration of trace active gas components in high-purity inert gas, thereby significantly improving product yield, performance consistency and process adaptability.

[0009] The above technical purpose of the present application is achieved by the following technical scheme:

[0010] A debinding sintering furnace, comprising:

[0011] a furnace body, which is internally provided with a furnace chamber for accommodating workpieces;

[0012] a heat source arranged in the furnace body;

[0013] a hot air circulation system, which comprises a centrifugal fan and a circulation air duct in communication with the furnace chamber, and at least a part of the heat source is located in the circulation air duct;

[0014] Further comprising an inert gas supply system, which comprises an inert gas source, a first pressure compensation pipeline and a second pressure compensation pipeline;

[0015] The first pressure compensation pipeline is in communication with the inert gas source at one end and in communication with the bottom of the furnace body at the other end, and is used for rapidly filling the furnace chamber with inert gas to replace air before sintering;

[0016] The second pressure compensation pipeline is in communication with the inert gas source at one end and in communication with the suction port of the centrifugal fan at the other end, and is used for introducing inert gas into the hot air circulation system during sintering, and after preheating by mixing with high-temperature gas in the circulation air duct, sending it back to the furnace chamber;

[0017] Further comprising an air supplementing system, which comprises an oxygen-containing gas source and a bypass pipeline in communication with the furnace chamber, and is used for supplementing air or oxygen into the furnace chamber.

[0018] Further provided are: a liquefied gas special ball valve, a filter, a pressure sensor assembly, a pressure reducing valve, a pressure switch assembly, an electric butterfly valve and a ZII type vortex flowmeter arranged in sequence on the first pressure compensation pipeline along the inert gas flow direction.

[0019] Further provided are: a ball valve, a pressure gauge, a pneumatic high-temperature hot air butterfly valve and a split vortex flowmeter arranged in sequence on the bypass pipeline along the gas flow direction.

[0020] Further provided are: the bypass pipeline of the air supplementing system is connected to the first pressure compensation pipeline of the inert gas supply system, and the connection point is located between the electric butterfly valve and the pressure switch assembly.

[0021] Further provided are: the second pressure compensation pipeline is arranged at the top of the furnace body; and a blow-off fan assembly, a blow-off pipe butterfly valve matched therewith, a negative pressure fan assembly and a negative pressure pipe butterfly valve matched therewith are arranged on the second pressure compensation pipeline.

[0022] Another object of the present application is to provide a gas control method for the above-mentioned debinding sintering furnace, comprising the following steps:

[0023] S1: performing a furnace chamber gas replacement step;

[0024] S11: through the first pressure compensation pipeline in the inert gas supply system, quickly fill the inert gas from the bottom of the furnace body into the hearth, replace the air in the hearth, and make the oxygen content rapidly decrease to below the process requirement value;

[0025] S2: in the high-temperature sintering stage, the step of dynamically maintaining the positive pressure in the furnace is performed;

[0026] S21: through the second pressure compensation pipeline in the inert gas supply system, the supplementary inert gas is sent into the suction port of the centrifugal fan of the hot air circulation system;

[0027] S22: the supplementary inert gas is mixed and preheated with the circulating high-temperature gas in the circulating air duct;

[0028] S23: the mixed and preheated gas is sent back to the hearth by the centrifugal fan;

[0029] S3: in the high-temperature sintering stage, the step of supplementing oxygen-containing gas is performed;

[0030] S31: through the bypass pipeline in the air supplement system, a preset flow of air or oxygen is supplemented into the hearth.

[0031] Further setting: in the S31 step, the supplemented preset flow is controlled at 1 to 5 standard cubic meters per hour.

[0032] Further setting: the oxygen-containing gas supplementing step S3 further includes:

[0033] S32: a high-temperature oxygen sensor is arranged in the hearth to monitor the oxygen content in the hearth in real time;

[0034] S33: the real-time monitoring value of the high-temperature oxygen sensor is compared with the preset oxygen content target value, and according to the comparison difference, the flow of air or oxygen supplemented through the bypass pipeline is dynamically adjusted, so that the actual oxygen content in the hearth is maintained in the target value range.

[0035] Further setting: the hearth gas replacement step S1 includes a coordinated replacement substep:

[0036] S11a: through the first pressure compensation pipeline, fill the normal-temperature inert gas with high density from the bottom of the furnace body to perform the main replacement from bottom to top, and use the gravity effect to discharge the air in the hearth;

[0037] S11b: at the same time or immediately after the main replacement is performed, the auxiliary circulation replacement from top to bottom is performed by using the second pressure compensation pipeline and the hot air circulation system, to discharge the low-density mixed gas remaining in the upper part of the hearth due to gas mixing, so as to eliminate the replacement dead angle.

[0038] Further setting: between S2 and S3, the gas pretreatment step S2a is further included:

[0039] After the furnace is heated to the intermediate temperature section, the negative pressure fan assembly on the second pressure compensation pipeline is started to intermittently pump out the furnace, and the preheated inert gas is supplemented and circulated through the second pressure compensation pipeline and the hot air circulation system to alternately between controllable negative pressure and slight positive pressure, so that the impurity gas adsorbed on the surface of the workpiece and the inside of the furnace body is desorbed and discharged.

[0040] In summary, the present application has the following beneficial effects:

[0041] First, in the present application, by setting the first pressure compensation pipeline communicating with the bottom of the furnace body, high-flow and high-density inert gas is allowed to replace and blow the furnace from bottom to top, and the stable replacement laminar flow is used to efficiently discharge the air with smaller density in the furnace upward, so that the low-oxygen environment required by the process is achieved in a shorter time, the process preparation period is significantly shortened, and the overall production efficiency of the equipment is improved.

[0042] The one end of the second pressure compensation pipeline communicates with the suction inlet of the centrifugal fan, so that the supplemented normal-temperature inert gas is forced to be pre-mixed and heat-exchanged with the high-temperature circulating gas pumped out from the furnace inside the fan before entering the furnace, so that it is instantaneously preheated to a temperature close to that of the circulating gas. The thermal shock and local temperature field fluctuation caused by conventional cold gas direct injection are eliminated, and the extremely high temperature field uniformity in the furnace can still be maintained under the working condition of dynamic air compensation, providing a stable thermodynamic environment for the high-consistency sintering of temperature-sensitive materials, and significantly improving the yield and performance uniformity of the products.

[0043] By setting an independent air supplementing system including an oxygen-containing gas source and a bypass pipeline, the present application can realize accurate and controllable supplement of trace active gas components on the basis of high-purity inert gas, so as to finely regulate the sintering process of the material. It can meet the unconventional composite gas sintering process, for example, by introducing trace oxygen at a specific stage to promote the generation of specific oxide bonding phases at the material interface, thereby improving the physical or electrochemical performance of the final product, such as bonding strength and interface impedance.

[0044] Second, in the present application, by connecting the bypass pipeline of the air supplementing system to a specific position of the first pressure compensation pipeline, the functions of high-flow replacement and micro-flow supplement are realized in one furnace inlet, simplifying the furnace structure and reducing the potential leakage points. At the same time, this connection mode uses the pipeline volume of the first pressure compensation pipeline to buffer and stabilize the pulsating gas flow of trace supplement, further improving the stability and uniformity of the trace oxygen-containing gas supplement process.

[0045] Third, the method of the present application, by supplementing 1 to 5 standard cubic meters of trace oxygen-containing gas per hour to the high-purity inert gas, constructs a non-equilibrium thermodynamic environment with precisely controllable oxygen partial pressure. The precise oxygen partial pressure provides sufficient thermodynamic driving force to initiate in-situ solid-phase reaction of target product generation at the interface of functional coating and metal substrate, while not enough to cause bulk phase oxidation of the substrate. This in-situ reaction can generate a nanoscale, structurally dense, and both physically adhesive and electrochemically functional interface bonding phase. The interface phase not only serves as an atomic-level structural adhesive, greatly enhancing the bonding strength of the coating and the substrate, preventing delamination failure of the product during subsequent use, but more importantly, it optimizes the ion transport channel at the interface, significantly reducing the interface impedance, thereby fundamentally improving the core electrochemical performance and cycle stability of the final product.

[0046] Fourth, the method of the present application, the oxygen-containing gas supplementing step of S3, through real-time monitoring and closed-loop feedback control, its essence is to deepen the physical quantity of process control from the macroscopic gas flow to the core thermodynamic parameter that determines the direction and rate of chemical reaction, i.e. oxygen partial pressure. By constantly maintaining the oxygen partial pressure at the target value, the rate of in-situ solid-phase reaction at the interface is ensured to be constant, eliminating the kinetic uncertainty caused by fluctuations in reactant concentration, thereby ensuring the high uniformity of the generated interface phase in thickness and microstructure.

[0047] Fifth, the method of the present application, by synergistically combining two displacement methods based on different gas kinetic principles, it solves the inherent technical defects of single displacement method. The initial bottom-up main displacement utilizes the stable piston flow formed by the gas density difference to efficiently exclude most of the air in the furnace. The subsequent or simultaneous top-down auxiliary circulating displacement then utilizes forced convection to actively capture and remove the low-density mixed gas dead angle that is difficult to reach by gravity displacement and remains at the top of the furnace due to gas mixing.

[0048] Sixth, the method of the present application, also has the S2a step, which utilizes the basic principles of physical adsorption and gas partial pressure, by periodically creating a negative pressure environment through pumping, provides a strong desorption driving force for trace impurity molecules adsorbed on the surface of the workpiece and the furnace body, making them escape from the surface to the gas phase; and the subsequent micro-positive pressure supplement and circulation steps then utilize forced convection to efficiently capture and remove these desorbed impurity molecules outside the furnace. This active and alternating desorption and purge process can purify the furnace environment and the workpiece surface more efficiently and deeply compared to the traditional constant pressure purge. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 is a structural schematic diagram of a debinding sintering furnace;

[0050] Figure 2is a structural schematic diagram of an inert gas supply system and an air supplement system;

[0051] Figure 3 is an outside schematic diagram of the top of the furnace body;

[0052] Figure 4 is an inside schematic diagram of the top of the furnace body;

[0053] Figure 5 is a sectional schematic diagram of the furnace body.

[0054] In the figure, 100, furnace body; 101, furnace chamber; 200, heat source;

[0055] 300, inert gas supply system;

[0056] 310, first pressure supplement pipeline; 311, liquefied gas special ball valve; 312, filter; 313, pressure sensor assembly; 314, pressure reducing valve; 315, pressure switch assembly; 316, electric butterfly valve; 317, ZII type vortex flowmeter;

[0057] 320, bypass pipeline; 321, ball valve; 322, pressure gauge; 323, pneumatic high-temperature hot air butterfly valve; 324, split vortex flowmeter;

[0058] 330, second pressure supplement pipeline; 331, purging fan assembly; 332, purging pipe butterfly valve; 333, negative pressure fan assembly; 334, negative pressure pipe butterfly valve;

[0059] 400, centrifugal fan; 401, circulating air duct; 500, high-temperature oxygen sensor. DETAILED DESCRIPTION

[0060] The application will be described in further detail below with reference to the drawings.

[0061] In the description of the application, it should be understood that the orientations or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the application.

[0062] The application provides a degreasing sintering furnace, which comprises a furnace body, a heat source, an inert gas supply system and an air supplement system. Figure 1As shown, the furnace body 100 is provided. The interior of the furnace body 100 defines a furnace chamber 101 for accommodating and heat-treating workpieces. In order to heat the workpieces in the furnace chamber 101, a heat source 200 is arranged in the furnace body 100.

[0063] The furnace body 100 is further provided with a hot air circulation system. The hot air circulation system comprises a centrifugal fan 400 and a circulation air duct 401 in communication with the furnace chamber 101. The centrifugal fan 400 serves as a power source to drive the circulation of the gas in the furnace chamber 101 between the furnace chamber 101 and the circulation air duct 401 to form a forced convection circulation. At least a part of the heat source 200 is arranged inside the circulation air duct 401, so that the circulating gas can efficiently carry heat energy.

[0064] The debinding and sintering furnace further comprises an inert gas supply system 300 and an air supplement system.

[0065] The inert gas supply system 300 comprises an inert gas source and a pressure supplement pipeline in communication with the inert gas source. The pressure supplement pipeline specifically comprises a first pressure supplement pipeline 310 and a second pressure supplement pipeline 330, which are respectively connected to the inert gas source for performing different gas supplement functions at different stages of the process.

[0066] One end of the first pressure supplement pipeline 310 is connected to the inert gas source, and the other end is in communication with the bottom region of the furnace body 100. This structural arrangement enables the first pressure supplement pipeline 310 to rapidly fill the inert gas into the furnace chamber 101 from bottom to top before the start of the sintering process, so as to efficiently displace the air in the furnace chamber 101.

[0067] One end of the second pressure supplement pipeline 330 is also connected to the inert gas source, and the other end is connected to the suction inlet of the centrifugal fan 400 of the hot air circulation system. This structure enables the supplemented inert gas to be first sucked into the hot air circulation system during the sintering process, to be fully mixed with the high-temperature gas in the circulation air duct 401 and to be preheated, and then to be uniformly sent back to the furnace chamber 101 by the centrifugal fan 400.

[0068] The air supplement system comprises an oxygen-containing gas source and an independent bypass pipeline 320. The bypass pipeline 320 is in communication with the internal space of the furnace chamber 101, and is used to supplement a preset flow of air or oxygen into the furnace chamber 101 according to the process requirements.

[0069] In some specific embodiments, the heat source 200 can be an electric heating element such as a resistance wire, a silicon-carbon rod, a silicon-molybdenum rod, or an infrared heating lamp. The centrifugal fan 400 can be an axial flow fan or other high-temperature-resistant fan capable of driving the circulation of high-temperature gas. The inert gas source can be a high-pressure steel cylinder group, a liquid argon storage tank, or a site nitrogen production device, which provides inert gas, preferably argon or high-purity nitrogen. The oxygen-containing gas source can be a clean compressed air machine, a high-pressure oxygen cylinder, or a pre-mixed gas source of air and inert gas.

[0070] In the inert gas supply system 300, along the direction of gas flow from the inert gas source to the bottom of the furnace body 100, a manual shut-off valve, such as a ball valve 311 for liquefied gas, is first arranged on the first pressure compensation pipeline 310, which is used to isolate the gas source in the maintenance or non-working state. A filter 312 is arranged downstream of the manual shut-off valve, which is used to remove impurities that may exist in the gas. The filtered gas successively flows through a pressure sensor assembly 313, a pressure reducing valve 314 and a pressure switch assembly 315. Among them, the pressure sensor assembly 313 is used to monitor the original pressure in the pipeline, the pressure reducing valve 314 is used to adjust the gas pressure to a stable process pressure, and the pressure switch assembly 315 is used to monitor whether the pressure after pressure reduction is within a safe range. Downstream of the pressure switch assembly 315, an electric butterfly valve 316 is arranged as the main control valve of the pipeline. Downstream of the electric butterfly valve 316, near the inlet of the furnace body 100, a vortex flow meter, such as a ZII type vortex flow meter 317, is also arranged for metering the flow of inert gas.

[0071] Similarly, the bypass pipeline 320 in the air supplement system is also specifically configured. Along the direction of gas flow from the oxygen-containing gas source to the connection point, a manual ball valve 321 is first arranged on the bypass pipeline 320. A pressure gauge 322 is arranged downstream of the manual ball valve 321, which is used to directly display the pressure of the pipeline. A pneumatic high-temperature hot air butterfly valve 323 is arranged downstream of the pressure gauge 322 as the main control valve of the pipeline. Downstream of the butterfly valve, a split-type vortex flow meter 324 is arranged for accurately metering the flow of supplemented oxygen-containing gas. In other embodiments, the control valve on the pipeline, such as the electric butterfly valve 316 or the pneumatic butterfly valve, can be replaced by an electric ball valve 321, a solenoid valve or a precision regulating valve according to the control requirements. The flow meter can also be selected as a mass flow meter or other types of flow measuring instruments according to the measurement medium and accuracy.

[0072] In the present embodiment, the inert gas source and the oxygen-containing gas source are external structures, and therefore are not shown in the figure.

[0073] In the present embodiment, the outlet end of the bypass pipeline 320 of the air supplement system is connected to the first pressure compensation pipeline 310 of the inert gas supply system 300. The connection point is located downstream of the pressure switch assembly 315 and upstream of the electric butterfly valve 316 on the first pressure compensation pipeline 310.

[0074] In a specific embodiment, the second pressure compensation pipeline 330 is arranged at the top of the furnace body 100. The second pressure compensation pipeline 330 is not a single functional pipeline in structure, but constitutes a plurality of gas management modules with multiple gas processing capabilities,

[0075] Specifically, the gas management module comprises a purging fan assembly 331, and a purging pipe butterfly valve 332 is connected to the pipeline of the purging fan assembly 331 to control the opening and closing of the pipeline. The outlet end of the purging fan assembly 331 is connected to the suction inlet of the centrifugal fan 400 in the hot air circulation system to actively send the supplemented inert gas into the circulation system; and the inlet end is connected to the inert gas source.

[0076] In addition, the gas management module further comprises a separate negative pressure fan assembly 333. The pipeline of the negative pressure fan assembly 333 is also connected with a negative pressure pipe butterfly valve 334. The air suction port of the negative pressure fan assembly 333 is connected to the internal space of the furnace 101 to perform air extraction or create a negative pressure environment, and the exhaust port is connected to an external waste gas treatment system. Through the selective operation of the two fan assemblies, the functions of gas replenishment, internal circulation and external extraction of the furnace 101 are integrated.

[0077] In other embodiments, the above-mentioned fan assemblies and valves can have various options. For example, the purging fan assembly 331 or the negative pressure fan assembly 333 can select high-pressure fans, Roots blowers or turbo molecular pumps according to the required air volume and pressure. The butterfly valve can also be a ball valve, a gate valve or an electric regulating valve according to the control accuracy requirement.

[0078] The present application also provides a gas control method for the above-mentioned defatting sintering furnace, comprising the following steps:

[0079] S1: performing a furnace 101 gas replacement step;

[0080] S11: rapidly filling inert gas into the furnace 101 from the bottom of the furnace body 100 through the first pressure compensation pipeline 310 in the inert gas supply system 300 to replace the air in the furnace 101 and rapidly reduce the oxygen content to below the process requirement value;

[0081] S2: performing a dynamic positive pressure maintaining step in the high-temperature sintering stage;

[0082] S21: sending the supplemented inert gas into the suction inlet of the centrifugal fan 400 of the hot air circulation system through the second pressure compensation pipeline 330 in the inert gas supply system 300;

[0083] S22: mixing and preheating the supplemented inert gas with the circulating high-temperature gas in the circulating air duct 401;

[0084] S23: sending the mixed and preheated gas back to the furnace 101 by the centrifugal fan 400;

[0085] S3: performing an oxygen-containing gas replenishment step in the high-temperature sintering stage;

[0086] S31: supplying a preset flow of air or oxygen into the furnace 101 through the bypass pipeline 320 in the air supplement system.

[0087] In the S31 step, the preset flow of air or oxygen supplied is controlled at 1 to 5 standard cubic meters per hour.

[0088] Further, the oxygen-containing gas supplement step S3 further includes:

[0089] S32: setting a high-temperature oxygen sensor 500 in the furnace 101 to monitor the oxygen content in the furnace 101 in real time;

[0090] S33: comparing the real-time monitoring value of the high-temperature oxygen sensor 500 with a preset oxygen content target value, and dynamically adjusting the flow of air or oxygen supplemented through the bypass pipeline 320 according to the comparison difference, so that the actual oxygen content in the furnace 101 is maintained within the target value range.

[0091] Further, the furnace 101 gas replacement step S1 includes the following coordinated replacement sub-steps:

[0092] S11a: filling a high-density normal-temperature inert gas from the bottom of the furnace body 100 through the first pressure supplement pipeline 310 to perform a bottom-up main replacement, and using gravity effect to discharge the air in the furnace 101;

[0093] S11b: simultaneously or immediately after the main replacement, using the second pressure supplement pipeline 330 and the hot air circulation system to perform a top-down auxiliary circulation replacement to discharge the low-density mixed gas remaining in the upper part of the furnace 101 due to gas mixing, so as to eliminate the replacement dead angle.

[0094] Further, between the S2 and S3, a gas pretreatment step S2a is further included:

[0095] After the furnace 101 is heated to the intermediate temperature section, the negative pressure fan assembly 333 on the second pressure supplement pipeline 330 is started to intermittently pump the furnace 101, and at the same time, the preheated inert gas is supplemented and circulated through the second pressure supplement pipeline 330 and the hot air circulation system, so as to alternate between controllable negative pressure and slight positive pressure, desorb and discharge the impurity gas adsorbed on the surface of the workpiece and the inside of the furnace body 100.

[0096] The above method is exemplified in a specific application scenario:

[0097] S1: coordinated high-efficiency gas replacement step;

[0098] S11: furnace 101 pre-pumping and main replacement;

[0099] S111: The coated aluminum foil of the roll is the workpiece, which enters the feeding section of the furnace body 100 through the continuous conveying system, and the furnace door is sealed at this time. At this time, the furnace is at room temperature (25°C) and normal pressure air gas (oxygen content is about 20.9%). First, start the negative pressure fan assembly 333 on the second pressure compensation pipeline 330 to pre-evacuate the furnace 101 for 5 minutes, so that the pressure in the furnace reaches-5kPa. This step can quickly remove about 5% of the air, saving time and cost for subsequent inert gas replacement.

[0100] S112: Close the negative pressure pipeline valve and open the electric butterfly valve 316 of the first pressure compensation pipeline 310. The room temperature argon gas with a purity of 99.999% is filled from the bottom of the furnace body 100 at a large flow rate of 200 standard cubic meters / hour. Because the density of cold argon gas is much greater than that of hot air in the furnace, the argon gas expels the light air from the furnace 100 from bottom to top.

[0101] S12: Auxiliary circulation replacement and end point control;

[0102] S121: After 2 minutes of main body replacement, start the low-speed operation of the centrifugal fan 400 of the hot air circulation system, and at the same time, supplement the argon gas through the second pressure compensation pipeline 330 at a flow rate of 20 standard cubic meters / hour. The centrifugal fan 400 forms a negative pressure area in the upper part of the furnace 101, actively sucking the low-density gas remaining at the top and mixed with argon gas into the circulating air duct 401 and discharging it, breaking the gas cap dead angle formed at the top due to the density difference in the traditional replacement method.

[0103] S122: The oxygen content sensor in the furnace monitors the oxygen content in real time. The system determines that when the oxygen content is continuously stable below 10ppm for 1 minute, the S1 step is completed. The system automatically closes the first pressure compensation pipeline 310, and switches the gas supplementing flow rate of the second pressure compensation pipeline 330 to a slow pressure compensation mode for maintaining a micro-positive pressure of +100Pa in the furnace.

[0104] S2a: Dynamic pressure swing gas pretreatment step;

[0105] S2a1: Warm up to the intermediate temperature section;

[0106] S2a11: The heating system is started to raise the furnace temperature from room temperature to 450°C at a rate of 10°C / min. In this process, the organic binder in the coating begins to decompose and gasify in large quantities, and at the same time, the trace amount of water adsorbed by the workpiece and the furnace wall also evaporates, forming a gas containing a large amount of impurities.

[0107] S2a2: Intermittent negative pressure desorption and purging;

[0108] 2a21: The furnace temperature is kept at 450°C for 30 minutes. During this period, 10 "pressure swing" cycles are performed. Each cycle is 4 minutes, specifically:

[0109] Negative pressure desorption stage: start the negative pressure fan assembly 333 on the second pressure compensation pipeline 330, and exhaust the furnace 101 for 60 seconds to reduce the pressure in the furnace to-1.0 kPa. The negative pressure environment can greatly promote the impurity molecules adsorbed on the surface of the workpiece and the pores of the furnace wall to separate out and enter the gas in the furnace 101.

[0110] Positive pressure purging stage: close the negative pressure pipeline, and supplement the preheated pure argon through the second pressure compensation pipeline 330 and the hot air circulation system, so that the pressure in the furnace is restored to +150 Pa within 180 seconds and is maintained at +150 Pa. The fresh and circulating argon flow can efficiently carry away the impurity molecules desorbed in the previous stage, and is discharged through the exhaust port. Through the dynamic process of one extraction and one compensation, deep purification of trace impurities is realized.

[0111] S2: high-temperature sintering and non-disturbance gas maintaining step;

[0112] S21: heating to sintering temperature;

[0113] S211: after the pretreatment step is completed, the heating system is operated at full power, and the furnace temperature is raised from 450 DEG C to the final sintering temperature of 620 DEG C at a rate of 5 DEG C / min.

[0114] S22: constant-temperature sintering and gas precise maintaining;

[0115] S221: the furnace temperature is precisely constant at 620 DEG C for 2 hours. During this period, the pressure sensor in the furnace and the control system of the second pressure compensation pipeline 330 are linked, and the pressure in the furnace is always stabilized at +100 Pa (±5 Pa). Any pressure drop caused by a small leakage will be immediately responded by the second pressure compensation pipeline 330 and supplemented with argon preheated by the hot air circulation system, so as to ensure that the temperature field uniformity of the core sintering area in the furnace is controlled within ±1 DEG C.

[0116] S3: closed-loop feedback type trace oxygen complexing step;

[0117] S31: interface modification process starts;

[0118] S311: in the last 1 hour of constant temperature at 620 DEG C, the high-temperature oxygen sensor 500 starts to work, and the system target oxygen content is set to 50 ppm.

[0119] S32: closed-loop feedback dynamic oxygen supplementing;

[0120] S321: the control valve of the air supplementing system is opened, and the bypass pipeline 320 starts to supplement compressed air into the furnace.

[0121] Initial stage: the reading of the high-temperature oxygen sensor 500 is lower than 50 ppm, and the air is supplemented at a flow rate of 3.5 standard cubic meters / hour.

[0122] Approaching target: when the oxygen level rises to 45 ppm, reduce the output, and the flow rate is reduced to 1.0 Nm3 / h accordingly.

[0123] Stable maintenance: in the subsequent process, the material reaction will consume oxygen. When the high-temperature oxygen sensor 500 reading is lower than 48 ppm, immediately increase the trace amount of the air supply flow rate; when it is higher than 52 ppm, immediately reduce it, so as to dynamically maintain the actual oxygen content in the target window of 50 ppm (± 2 ppm) at all times.

[0124] The above embodiments are only explanations of the present application, and are not limitations of the present application. Those skilled in the art can make modifications to the embodiments according to needs without creative contributions after reading the specification, but as long as they are within the scope of the claims of the present application, they are protected by the Patent Law.

Claims

1. A defatting sintering furnace, comprising: a furnace body (100) with a furnace chamber (101) for accommodating workpieces inside; a heat source (200) arranged in the furnace body (100); a hot air circulation system comprising a centrifugal fan (400) and a circulating air duct (401) communicating with the furnace chamber (101), and at least a part of the heat source (200) is located in the circulating air duct (401); characterized in that it further comprises an inert gas supply system (300) comprising an inert gas source, a first pressure compensation pipeline (310) and a second pressure compensation pipeline (330); wherein one end of the first pressure compensation pipeline (310) communicates with the inert gas source, and the other end communicates with the bottom of the furnace body (100), and is used for rapidly filling the furnace chamber (101) with inert gas to replace air before sintering; one end of the second pressure compensation pipeline (330) communicates with the inert gas source, and the other end communicates with the suction port of the centrifugal fan (400), and is used for introducing inert gas into the hot air circulation system during the sintering process, and then preheating the inert gas by mixing with high-temperature gas in the circulating air duct (401) and returning it to the furnace chamber (101); further comprising an air supplement system comprising an oxygen-containing gas source and a bypass pipeline (320) communicating with the furnace chamber (101) for supplementing air or oxygen into the furnace chamber (101); a liquefied gas special ball valve (311), a filter (312), a pressure sensor assembly (313), a pressure reducing valve (314), a pressure switch assembly (315), an electric butterfly valve (316) and a ZII type vortex flowmeter (317) are sequentially arranged on the first pressure compensation pipeline (310) along the inert gas flow direction; a ball valve (321), a pressure gauge (322), a pneumatic high-temperature hot air butterfly valve (323) and a split vortex flowmeter (324) are sequentially arranged on the bypass pipeline (320) along the gas flow direction; the bypass pipeline (320) of the air supplement system is connected to the first pressure compensation pipeline (310) of the inert gas supply system (300), and the connection point is located between the electric butterfly valve (316) and the pressure switch assembly (315); the second pressure compensation pipeline (330) is arranged at the top of the furnace body (100); the second pressure compensation pipeline (330) is provided with a purging fan assembly (331) matched with a purging pipe butterfly valve (332), and a negative pressure fan assembly (333) matched with a negative pressure pipe butterfly valve (334).

2. A gas control method using the defatting sintering furnace according to claim 1, characterized by, comprising the following steps: S1: performing a furnace chamber (101) gas replacement step; S11: rapidly filling the furnace chamber (101) with inert gas from the bottom of the furnace body (100) through the first pressure compensation pipeline (310) in the inert gas supply system (300) to replace the air in the furnace chamber (101) and rapidly reduce the oxygen content to below the process requirement value; S2: performing a step of dynamically maintaining positive pressure in the furnace during high-temperature sintering stage; S21: through the second pressure compensation pipeline (330) in the inert gas supply system (300), the supplementary inert gas is sent into the suction port of the centrifugal fan (400) of the hot air circulation system; S22: the supplementary inert gas is mixed and preheated with the circulating high-temperature gas in the circulating air duct (401); S23: the mixed and preheated gas is sent back to the hearth (101) by the centrifugal fan (400); S3: in the high-temperature sintering stage, the oxygen-containing gas supplement step is performed; S31: through the bypass pipeline (320) in the air supplement system, a preset flow of air or oxygen is supplemented into the hearth (101).

3. The gas control method according to claim 2, characterized by: In the S31 step, the supplemented preset flow is controlled at 1 to 5 standard cubic meters per hour.

4. The gas control method according to claim 2, characterized by: The oxygen-containing gas supplement step of S3 further includes: S32: a high-temperature oxygen sensor (500) is arranged in the hearth (101) to monitor the oxygen content in the hearth (101) in real time; S33: the real-time monitoring value of the high-temperature oxygen sensor (500) is compared with the preset oxygen content target value, and according to the comparison difference, the flow of air or oxygen supplemented through the bypass pipeline (320) is dynamically adjusted, so that the actual oxygen content in the hearth (101) is maintained at the target value range.

5. The gas control method of claim 2, wherein: The gas replacement step of S1 of the hearth (101) includes the following coordinated replacement sub-steps: S11a: through the first pressure compensation pipeline (310), the normal-temperature inert gas with high density is filled from the bottom of the furnace body (100) to perform the bottom-up main replacement, and the air in the hearth (101) is discharged by using the gravity effect; S11b: at the same time or immediately after the main replacement is performed, the second pressure compensation pipeline (330) and the hot air circulation system are used to perform the top-down auxiliary circulation replacement, and the low-density mixed gas remaining in the upper part of the hearth (101) due to gas mixing is discharged to eliminate the replacement dead angle.

6. The gas control method according to claim 4, characterized by: Between S2 and S3, the gas pretreatment step S2a is further included: After the hearth (101) is heated to the intermediate temperature section, the negative pressure fan assembly (333) on the second pressure compensation pipeline (330) is started to intermittently pump the hearth (101), and the preheated inert gas is supplemented and circulated through the second pressure compensation pipeline (330) and the hot air circulation system, so as to alternate between controllable negative pressure and slight positive pressure, desorb and discharge the impurity gas adsorbed on the surface of the workpiece and the inside of the furnace body (100).

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