Stainless steel material annealing equipment and process

Abstract

The present application belongs to the technical field of metal heat treatment, and discloses a stainless steel material annealing equipment and process, which comprises an annealing furnace, a pretreatment gas chamber is arranged at the feeding port of the annealing furnace, the pretreatment gas chamber is communicated with the annealing furnace and a sealing isolation door is arranged at the communication position; the pretreatment gas chamber is provided with a heating system, an air extraction system and an air charging system; before the workpiece enters the annealing furnace, the pressure of the pretreatment cavity is accurately controlled to be slightly higher than the micro-positive pressure state of the main furnace by the air charging system. When the sealing isolation door is opened to transfer the workpiece, the positive pressure protection gas flow unidirectionally flows from the pretreatment cavity to the main furnace, a dynamic air curtain barrier is formed, and external air backflow is completely blocked; problems such as the increase of the dew point in the furnace, the abnormal hydrogen consumption and the local oxidation caused by the oxygen or moisture brought by the workpiece are avoided, the stable period of the atmosphere in the main furnace is significantly prolonged, and the present application is especially suitable for the continuous multi-batch small-batch production scene and guarantees the long-term consistency of the annealing metallurgical quality.

Description

Technical Field

[0001] This invention belongs to the field of metal heat treatment technology, specifically relating to an annealing device and process for stainless steel materials. Background Technology

[0002] Most stainless steel annealing equipment currently on the market is designed for continuous production of coils and strips, with technology highly concentrated in high-speed continuous annealing production lines. This type of equipment is suitable for thin plates or wires with regular shapes, uniform surface conditions, and large batch sizes. Atmosphere control, heating uniformity, and cooling rhythm can all be highly optimized through stable and continuous process parameters. In contrast, stainless steel workpieces (such as valve housings, pump bodies, medical device structural components, fasteners, flange joints, etc.) often have complex geometries, large surface area to volume ratios, and internal blind holes, internal threads, intersecting channels, or tiny gaps. They also typically exhibit characteristics of small batches, multiple varieties, and non-standard customization. These workpieces not only face difficulties in achieving uniform heating and synchronous cooling in the thermal field, but are also prone to absorbing environmental moisture, residual cleaning agents, air entrainment, and even trace amounts of oil film during pre-processing steps such as machining, ultrasonic cleaning, water-based degreasing, air drying, or manual transfer. Once these "invisible contaminants" enter the high-temperature annealing furnace, they are rapidly released, severely interfering with the stability of the high-purity reducing atmosphere and posing a significant threat to annealing quality.

[0003] First, coiled materials are typically flat, open, continuous strip structures with fully exposed surfaces, making them easy to dry quickly with high-speed hot air or infrared radiation. Furthermore, the types of contaminants are relatively simple (mainly rolling oil). Complex workpieces, however, have numerous closed or semi-closed cavities (such as valve chambers, threaded holes, and assembly gaps), where moisture and cleaning fluids easily accumulate and are difficult to completely evaporate even under prolonged drying at atmospheric pressure. Once in the high-temperature annealing zone, these "hidden moisture" suddenly vaporize and expand, not only locally diluting the protective atmosphere and raising the dew point, but also potentially creating vapor pressure shocks within the micropores, affecting surface integrity. In addition, workpieces are exposed to air for a much longer time during handling than coiled materials in continuous production lines, resulting in significantly higher adsorption of oxygen and water molecules, further exacerbating the risk of atmosphere fluctuations during the initial furnace entry.

[0004] Secondly, coil annealing is carried out in a closed, dynamically balanced furnace, ensuring continuous flow and stable composition of the protective gas. Furthermore, the new strip enters at a constant speed, minimizing system disturbance and facilitating compensation. In contrast, workpiece annealing often employs batch or semi-continuous charging, with each furnace opening interrupting the steady-state of the atmosphere. Without pre-drying and degassing, multiple workpieces loaded at once may carry several grams or even tens of grams of adsorbed water and air, effectively "injecting" a miniature oxidation source into the high-purity reducing atmosphere. This not only leads to significant differences in surface gloss at different locations within the same furnace (with areas near the feed inlet being more prone to oxidation), but may also cause localized hydrogen consumption imbalances, affecting decarburization or inducing hydrogen embrittlement. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide an annealing equipment and process for stainless steel materials to solve the problems existing in the background art.

[0006] To solve the above-mentioned technical problems, the first technical solution of the present invention is a stainless steel annealing device, including an annealing furnace. The inlet of the annealing furnace is provided with a pretreatment gas chamber, which is connected to the annealing furnace and a sealed isolation door is provided at the connection point. The pretreatment gas chamber has a heating system, a vacuum system, and a gas filling system. When the sealed isolation door is closed, the workpiece in the pretreatment gas chamber is dried by the heating system. The vacuum system is used to evacuate the pretreatment gas chamber to a negative pressure state. After the vacuuming is completed, the gas filling system fills the pretreatment gas chamber with protective gas, so that the pressure of the pretreatment gas chamber is restored to a slightly positive pressure state higher than the pressure inside the annealing furnace. Then the sealed isolation door is opened to send the workpiece into the annealing furnace, while ensuring that external air cannot flow back and that the protective atmosphere of the main furnace is not diluted or contaminated.

[0007] Preferably, the gas source of the inflation system includes a circulating gas source and a fresh gas source, wherein the circulating gas source uses the protective gas inside the annealing furnace.

[0008] Furthermore, the heating system includes an electric heating mode and a gas-assisted heating mode; the electric heating mode directly or radiates the workpiece by means of electric heating elements set on the wall or internal support of the pretreatment gas chamber; the gas-assisted heating mode uses a circulating gas source to introduce high-temperature protective gas from the annealing furnace into the pretreatment gas chamber as a heat carrier to convectively heat the workpiece.

[0009] As a preferred embodiment, the pretreatment chamber comprises a heating chamber with a heating system and a vacuum chamber with a pumping system and a filling system. The heating chamber and the vacuum chamber are arranged adjacent to each other and connected by an internal isolation door. The workpiece first enters the heating chamber for preliminary drying, and then is transferred to the vacuum chamber. The pumping system is activated in a sealed state to evacuate the chamber to a negative pressure for further drying of the workpiece. After evacuation, a protective gas is injected into the vacuum chamber through the filling system to restore the pressure of the vacuum chamber to a slightly positive pressure higher than that in the annealing furnace. Then, the sealed isolation door between the vacuum chamber and the annealing furnace is opened, and the workpiece is sent into the annealing furnace, ensuring that the entire transfer process is completed under a controlled atmosphere, effectively preventing air intrusion and maintaining the stability of the main furnace atmosphere.

[0010] As a preferred embodiment, in the second configuration of the pretreatment chamber, the heating system, the extraction system, and the filling system of the pretreatment chamber are located in the same chamber. After the workpiece enters the pretreatment chamber, the extraction system is first activated under the sealed state of the chamber to draw the interior into a negative pressure environment, thereby reducing the moisture evaporation temperature and promoting the release of adsorbed gases. Subsequently, the heating system is activated under the condition of maintaining negative pressure to dry the workpiece. After drying is completed, the extraction system is turned off, and protective gas is introduced into the chamber through the filling system to restore the pressure of the chamber to a slightly positive pressure state higher than that in the annealing furnace.

[0011] Furthermore, after restoring the pressure in the chamber to a slightly positive pressure higher than that in the annealing furnace, a second evacuation operation is performed to further remove residual impurity gases released due to the disturbance during the first evacuation. Subsequently, a second evacuation is performed to inject protective gas into the pretreatment chamber, providing a more stable transition environment for the workpiece to enter the main furnace.

[0012] As a preferred embodiment, in the third scheme of the pretreatment gas chamber, the heating system, the evacuation system, and the filling system of the pretreatment gas chamber are located in the same chamber. After the workpiece enters the pretreatment gas chamber, the evacuation system is first activated to evacuate the interior to a vacuum state while the chamber is sealed. The evacuation system is then turned off, and the gas-assisted heating mode is activated. High-temperature protective gas from the circulating gas source is introduced through the filling system to convectively heat and dry the workpiece. After drying, a second evacuation is performed to remove residual gas released by disturbance. Subsequently, the filling system is switched to a new gas source for a second filling, injecting high-purity protective gas to bring the chamber to a slightly positive pressure state higher than that of the annealing furnace, and then the workpiece is sent into the annealing furnace.

[0013] To solve the above-mentioned technical problems, the second technical solution of the present invention is an annealing process for stainless steel materials, which applies the stainless steel annealing equipment described in the first technical solution regarding the pretreatment gas chamber. The annealing process includes the following steps: Step 1: Send the workpiece to be processed into the heating chamber of the pretreatment gas chamber. After closing the internal isolation door between the heating chamber and the vacuum chamber, start the heating system to pre-dry the workpiece. Step 2: Then open the internal isolation door, transfer the workpiece to the vacuum chamber and close the internal isolation door to form a sealed cavity in the vacuum chamber; start the pumping system to pump the vacuum chamber to a negative pressure state to reduce the desorption temperature of moisture and adsorbed gases and achieve deep drying; after the vacuuming is completed, inject protective gas into the vacuum chamber through the gas filling system to restore the pressure inside the chamber to a slightly positive pressure state that is higher than the pressure inside the annealing furnace. Step 3: Open the sealed isolation door between the vacuum chamber and the annealing furnace, and send the workpiece into the annealing furnace for subsequent heat treatment.

[0014] To solve the above-mentioned technical problems, the third technical solution of the present invention is a stainless steel annealing process, which applies the stainless steel annealing equipment described in the second solution of the pretreatment gas chamber in the first technical solution. The annealing process includes the following steps: Step 1: Place the workpiece in the pretreatment chamber and seal the chamber; Step 2: Activate the vacuum system to create a negative pressure environment inside the cavity; Step 3: Start the heating system while maintaining negative pressure to dry the workpiece; Step 4: After drying is complete, turn off the exhaust system and fill the chamber with protective gas through the gas filling system to restore the pressure inside the chamber to a slightly positive pressure state higher than that of the annealing furnace. Step 5: Perform a second evacuation to remove residual impurities released due to inflation disturbance; then refill with protective gas to complete the second pressurization. Step Six: Open the sealed isolation door between the pretreatment chamber and the annealing furnace, and send the workpiece into the annealing furnace for subsequent heat treatment.

[0015] To solve the above-mentioned technical problems, the fourth technical solution of the present invention is an annealing process for stainless steel materials, which applies the stainless steel annealing equipment described in the third solution of the pretreatment gas chamber in the first technical solution. The annealing process includes the following steps: Step 1: Place the workpiece in the pretreatment chamber and seal the chamber; Step 2: Activate the vacuum system to evacuate the cavity to a vacuum state; Step 3: Turn off the exhaust system and switch to gas-assisted heating mode. Introduce circulating gas from the annealing furnace through the gas filling system to introduce high-temperature protective gas into the chamber for convective heating and drying of the workpiece. Step 4: After drying, perform a second air extraction operation to remove any trace impurities newly released due to heating and gas disturbance. Step 5: Switch the inflation system to a new gas source and perform secondary inflation, injecting high-purity protective gas to make the pressure inside the cavity reach a slightly positive pressure state higher than that of the annealing furnace; Step Six: Open the sealed isolation door between the pretreatment chamber and the annealing furnace, and send the workpiece into the annealing furnace for subsequent heat treatment.

[0016] The main technical effects of this invention are reflected in the following aspects: In this invention, before the workpiece enters the annealing furnace, the pressure in the pretreatment chamber is precisely controlled to a slightly positive pressure state, slightly higher than that of the main furnace, through the gas filling system. When the sealed isolation door is opened to transfer the workpiece, the positive pressure protective airflow flows unidirectionally from the pretreatment chamber to the main furnace, forming a dynamic air curtain barrier that completely blocks the backflow of external air. This avoids problems such as increased dew point in the furnace, abnormal hydrogen consumption, and localized oxidation caused by oxygen or moisture brought in by the workpiece, significantly extending the atmosphere stabilization period of the main furnace. It is especially suitable for continuous multi-batch small-volume production scenarios, ensuring the long-term consistency of annealing metallurgical quality.

[0017] This invention features two functional zones within the pretreatment chamber: a heating chamber and a vacuum chamber, physically separated and sequentially linked by an internal isolation door. The workpiece is first pre-dried at low temperature under normal or slightly positive pressure in the heating chamber, effectively removing surface free water and volatile cleaning agents, avoiding direct condensation and reflux of moisture under high vacuum. It is then transferred to the vacuum chamber, where it is evacuated to negative pressure in a sealed state. Utilizing the synergistic effect of the workpiece's residual heat and the low-pressure environment, the residual heat provides the activation energy required for the desorption of adsorbed water, while the negative pressure significantly lowers the boiling point of water and organic matter, thereby efficiently releasing residual contaminants from enclosed structures such as threaded bottom holes and blind cavities. This two-stage drying strategy avoids the increased energy consumption and risk of localized overheating associated with secondary heating, while significantly improving the deep purification capability for geometrically complex workpieces, solving the problem of traditional single-chamber normal-pressure drying's inability to reach inner dead zones.

[0018] This invention innovatively adds a secondary vacuum purification process to the single-cavity pretreatment gas chamber: after the initial filling with protective gas, gas disturbance may induce the release of residual impurities in the micropores of the workpiece; at this time, a second vacuum is performed to efficiently remove newly generated contaminants; subsequently, a high-purity fresh gas source is switched to perform a secondary filling to rebuild a clean transition atmosphere. This "double vacuum and double filling" operation forms a closed-loop purification logic, significantly reducing the dew point and impurity partial pressure in the atmosphere before entering the furnace, solving defects such as micro-area oxidation, hydrogen embrittlement, or uneven brightness caused by trace amounts of water vapor or organic vapor entering the furnace, and ensuring a high degree of consistency in the annealing quality of multiple types of workpieces in the same furnace.

[0019] This invention introduces high-temperature protective gas from the annealing furnace as a heat carrier into the pretreatment gas chamber, and activates a "gas-assisted heating" mode by switching the gas filling path. After initial high-vacuum degassing, the pumping system is shut off, and a nitrogen-hydrogen mixture drawn from the main furnace is introduced into the pretreatment chamber, forming a high-speed forced convection thermal field. The high-temperature gas can penetrate deeply into dense threads, stacked gaps, or deep hole cavities, achieving all-round, penetrating heat exchange, overcoming the problem of delayed heating at the bottom of deep holes or in shielded areas caused by traditional electric heating relying on radiative heat transfer. This not only significantly improves heating uniformity and desorption kinetics, but also makes full use of the main furnace's waste heat resources, reducing additional energy consumption, and avoiding contaminant residue caused by insufficient local temperature. Attached Figure Description

[0020] Figure 1 A process flow diagram for an annealing process of stainless steel material using a split pretreatment gas chamber structure; Figure 2 A process flow diagram for an annealing process of stainless steel material using a single-cavity integrated pretreatment gas chamber; Figure 3 This is a process flow diagram for a single-cavity integrated pretreatment gas chamber combined with gas-assisted heating. Detailed Implementation

[0021] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, so as to make the technical solution of the present invention easier to understand and master. In the embodiments, it should be understood that the terms "middle," "upper," "lower," "top," "right side," "left end," "above," "back," "center," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, unless otherwise specified in this specific embodiment, the connection or fixing method between components can be achieved by bolt fixing, pin fixing, or pin connection commonly used in the prior art, etc., and therefore will not be described in detail in this embodiment.

[0022] The stainless steel annealing equipment and process provided by this invention are mainly applied to the high-cleanliness annealing treatment of small batches, multiple varieties, and complex stainless steel workpieces (such as valve bodies, pump bodies, flange joints, fasteners, and medical device components). However, it is not limited to this and can also be used in other similar or identical metal heat treatment production processes, such as the integrated degreasing and annealing treatment of high-temperature alloys, precision carbon steel parts, or copper alloy parts that are sensitive to surface oxidation under a protective atmosphere.

[0023] Furthermore, as is common knowledge in this industry, the sealing isolation doors mentioned earlier typically employ a pneumatically or electrically driven gate valve structure. Their sealing methods can be metal hard seals or high-temperature resistant elastic seals (such as graphite composite gaskets) to ensure effective isolation between chambers under high temperature and alternating positive / negative pressure conditions. The vacuum system often consists of a rotary vane vacuum pump, a Roots pump, or a combination of both. Resistance wires, silicon carbide rods, or infrared radiation tubes in the heating system are standard configurations for industrial electric heating elements. Nitrogen-hydrogen mixed protective gas is widely used as a reducing atmosphere in the bright annealing of stainless steel. These are common knowledge; therefore, their principles and structures will not be elaborated upon further.

[0024] Example 1 This embodiment discloses an annealing device for stainless steel materials, aiming to overcome the technical bottleneck of existing continuous annealing production lines being unable to adapt to small batches, multiple varieties, and high-contamination-risk workpieces. As described in the background art, traditional coil annealing relies on a stable and continuous thermal field and atmosphere environment. However, typical stainless steel workpieces such as valve bodies, due to their closed structures such as internal threads, are extremely prone to absorbing moisture, residual cleaning agents, or entraining air during the preceding cleaning, drying, and transfer processes. If directly fed into a high-temperature reducing annealing furnace, these "hidden contaminants" will be released violently within seconds, causing a sudden rise in local dew point, hydrogen partial pressure imbalance, and even micro-area oxidation or hydrogen embrittlement. To address this, this embodiment adds a pretreatment gas chamber at the annealing furnace inlet to achieve deep purification of the workpieces before they enter the furnace and seamless atmosphere connection.

[0025] In specific implementation, the annealing equipment includes an annealing furnace, the inlet of which is equipped with a pretreatment gas chamber. The pretreatment gas chamber is connected to the annealing furnace, and a sealed isolation door (usually a pneumatic or electric gate valve with a metal seal or high-temperature resistant elastic seal structure) is provided at the connection point. The pretreatment gas chamber has a heating system, a vacuum system, and a filling system. During operation, the operator loads the workpieces to be processed (such as a batch of flange joints or fasteners) into the pretreatment gas chamber and closes the outer door. At this time, the sealed isolation door remains closed, completely isolating the pretreatment gas chamber from the main furnace. Subsequently, the system first starts the vacuum system (usually composed of a rotary vane vacuum pump or a Roots vacuum pump) to quickly pump the pressure inside the chamber to a negative pressure state. This step significantly lowers the boiling point of water (refer to the boiling point table of water under different atmospheric pressure environments for details), allowing liquid water trapped in micropores, threaded bottom holes, or assembly gaps to vaporize and be extracted at low temperatures, effectively avoiding the false drying phenomenon of "dry surface, wet interior" during atmospheric pressure drying; this is a key improvement to address the problem of "hidden moisture being difficult to evaporate" in the background technology.

[0026] After the vacuum system draws the pressure inside the chamber to a negative pressure state, the heating system is activated to accelerate the desorption process of moisture.

[0027] Preferably, the heating system supports two heating modes: one is an electric heating mode, which uses resistance wires, silicon carbide rods, or infrared radiation tubes arranged on the cavity wall or a dedicated support to radiate or near-field heat to the workpiece. The other is a gas-assisted heating mode, which uses a gas filling system to draw high-temperature protective gas from the annealing furnace as a circulating gas source and introduces it into the pretreatment gas chamber to form a convective thermal field. It should be noted that the electric heating mode mainly relies on radiation or local contact heat transfer. When processing stainless steel workpieces with deep holes, internal cavities, dense threads, or stacked structures, heat is difficult to penetrate evenly into the internal structure, easily creating a "hot outside, cold inside" temperature gradient, resulting in incomplete desorption of moisture or contaminants. In contrast, the gas-assisted heating mode introduces the existing high-temperature protective gas (such as a nitrogen-hydrogen mixture) in the annealing furnace as a heat carrier into the pretreatment gas chamber, using forced convection to achieve all-round, penetrating heat exchange, significantly improving heating uniformity and efficiency, and is especially suitable for non-standard workpieces with complex geometries.

[0028] After drying, the extraction system is shut off, and protective gas is injected into the chamber via the inflation system. The inflation system has dual gas sources: one is a circulating gas source connected to the annealing furnace, used to introduce existing high-temperature protective gas (such as a nitrogen-hydrogen mixture); the other is connected to a high-purity fresh gas source. Additionally, the circulating gas flows through an impurity filtration module, which typically includes a high-temperature sintered metal filter element or a porous ceramic filter, effectively intercepting trace amounts of oxide dust, carbonized particles, or metal vapor condensate that may be carried within the furnace. Although the annealing furnace has a reducing atmosphere, particulate contaminants may still be generated during long-term operation due to workpiece decarburization and furnace material aging. If these are introduced directly into the pretreatment gas chamber without treatment, they may contaminate the surface of the workpiece to be treated. Therefore, the filtration module ensures the cleanliness of the circulating gas, allowing for energy saving and reuse without sacrificing pretreatment quality.

[0029] It is worth noting that the gas-assisted heating mode and the design of the circulating gas source avoid the system pressure imbalance problem that may be caused by the indiscriminate supply of fresh protective gas into the annealing furnace during operation of the pretreatment gas chamber. If only relying on the continuous charging of the new gas source to maintain positive pressure or provide heat, it will not only waste high-purity gas, but may also cause the internal pressure of the annealing furnace to rise continuously, forcing the system to frequently open the exhaust valve to release pressure, thereby disrupting the stability of the furnace atmosphere and increasing hydrogen consumption. In this embodiment, by prioritizing the use of the main furnace circulating gas source for heating and preliminary pressurization, the internal circulation and energy recovery of the protective gas are achieved: this effectively controls the pressure fluctuation of the main furnace, reduces the external exhaust demand, and maintains the dynamic balance of the annealing atmosphere.

[0030] In an optional embodiment, see Figure 1The pretreatment chamber adopts a split structure, including an adjacent heating chamber and a vacuum chamber, which are connected by an internal isolation door. The heating chamber is equipped with a heating system for preliminary drying under normal or slightly positive pressure; the vacuum chamber integrates a pumping system and a filling system, and is dedicated to deep drying and atmosphere transition.

[0031] Specifically, the workpiece first enters the heating chamber for preliminary drying under electric heating, removing surface free water and volatile components. It is then moved into the vacuum chamber, where the internal isolation door is closed, creating an independent, sealed cavity. The system activates the pumping device to rapidly reduce the pressure inside the cavity to a negative pressure state. Notably, the residual heat from the preliminary drying process synergizes with the negative pressure environment. On one hand, the residual heat provides the energy needed for the desorption of adsorbed water and residual solvents; on the other hand, the negative pressure significantly lowers the boiling point of water and organic matter, allowing them to vaporize at lower temperatures. This combination significantly accelerates the release rate of residual contaminants in micropores, threaded bottom holes, and closed channels, while avoiding increased energy consumption or the risk of localized overheating caused by secondary heating.

[0032] After vacuum drying is completed, protective gas (preferably fresh gas source) is injected into the vacuum chamber through the gas filling system to restore the pressure inside the chamber to a slightly positive pressure state, which is slightly higher than that of the annealing furnace. Then, the sealed isolation door between the vacuum chamber and the annealing furnace is opened, and the workpiece is sent into the main furnace under positive pressure protection. This ensures that the entire transfer process is completed in a controlled atmosphere, effectively preventing the intrusion of external air and maintaining the stability of the main furnace atmosphere.

[0033] In an optional embodiment, see Figure 2 The pretreatment gas chamber adopts a single-chamber integrated structure, but a secondary purification mechanism is introduced to further improve the cleanliness of the atmosphere before entering the furnace.

[0034] Specifically, after the workpiece enters the gas chamber and is sealed, the system first activates the vacuum system to create a negative pressure environment inside the chamber, thereby reducing the moisture evaporation temperature and promoting the release of adsorbed gases. Then, while maintaining the negative pressure, the heating system (electric heating) is activated to dry the workpiece. After drying, the vacuum system is shut off, and protective gas (preferably recirculated gas) is introduced into the chamber through the gas filling system to restore the pressure inside the chamber to a slightly positive pressure state higher than that of the annealing furnace.

[0035] The key improvement lies in the secondary evacuation operation performed after the initial pressurization to remove any residual impurities newly released due to gas disturbance; subsequently, a second pressurization is performed to inject high-purity protective gas (which can be switched to a new gas source) to rebuild an ultra-high cleanliness transition atmosphere. This secondary evacuation and pressurization operation is particularly suitable for medical devices, semiconductor components, or high-end fluid control elements that require extremely high surface gloss and cleanliness. It effectively prevents quality fluctuations within the same furnace batch caused by trace contaminants entering the furnace, ensuring surface consistency and metallurgical performance standards are met after annealing.

[0036] In an optional embodiment, see Figure 3 It also adopts a single-chamber integrated pretreatment gas chamber, but its core feature lies in the synergistic application of gas-assisted heating mode and internal pressure balance strategy.

[0037] Specifically, after the workpiece is loaded and sealed, the system first activates the vacuum system to evacuate the cavity to a high vacuum level, maximizing the removal of ambient air and surface-adsorbed gases. The vacuum system is then shut down, and a gas-assisted heating mode is activated: high-temperature protective gas is drawn from the annealing furnace via the gas filling system as a circulating heat carrier and introduced into the pretreatment gas chamber, forming a forced convection heat field. This high-temperature protective gas can penetrate the complex internal cavity of the workpiece, achieving omnidirectional, penetrating convection heat transfer. This overcomes the limitations of electric heating in covering deep holes, dense threads, or stacked areas, significantly improving heating uniformity and desorption efficiency.

[0038] After drying, the system performs a second air extraction to remove any trace organic residues newly released due to the impact of high-temperature gas; then the gas filling system is switched to a high-purity new gas source for a second gas filling to inject protective gas.

[0039] In this embodiment, the workpiece is first placed in a single-chamber integrated pretreatment gas chamber and evacuated to a high vacuum state. Then, high-temperature circulating protective gas from the annealing furnace is introduced for gas-assisted heating, utilizing a forced convection thermal field to thoroughly dry deep holes and complex structures within the workpiece. After heating, a second vacuum is performed to completely remove contaminants released into the gas phase space due to thermal desorption. Finally, a high-purity fresh gas source is switched to fill the chamber, restoring the pressure inside to a slightly positive pressure state higher than that of the annealing furnace. Under this positive pressure protection, the isolation door is opened to send the workpiece into the annealing furnace. Traditional processing methods typically only involve a single vacuum followed by direct filling with high-purity fresh gas for heating, or simple drying using circulating gas before entering the furnace, lacking a mechanism for secondary purification and coordinated gas source timing.

[0040] Compared to traditional methods, this embodiment achieves significantly better overall results than single-method approaches through the synergistic effect of circulating gas thermal drive, secondary vacuum purification, and fresh gas final-state protection. The high-temperature permeability of the circulating gas effectively solves the dead zone problem in areas such as blind holes and threads caused by traditional radiant heating, allowing for the full desorption of deeply adsorbed water and residual solvents. The secondary vacuum precisely removes these activated and released impurities, avoiding the problems of re-adsorption or incomplete dilution of contaminants during traditional single-filling. Finally, the injected fresh gas forms a stable reduction barrier on the surface of the purified hot workpiece, eliminating the risk of localized condensation caused by direct contact between the cold fresh gas and the hot workpiece, and avoiding the high energy and gas consumption associated with using fresh gas throughout the process. Ultimately, this process achieves higher blind hole cleanliness and annealing brightness pass rates than the pure fresh gas solution while maintaining a low energy consumption level close to that of a pure circulating gas solution, while significantly reducing the consumption of high-purity fresh gas, truly achieving a balance between ultimate cleanliness, high efficiency and energy saving, and operational stability.

[0041] Example 2 This embodiment discloses an annealing process for stainless steel materials. This process is based on the stainless steel annealing equipment described in Embodiment 1 and is suitable for equipment structures employing split pretreatment chambers. Its core lies in a two-stage drying strategy of "atmospheric pressure pre-drying + vacuum deep drying." See also... Figure 1 The specific operating procedure is as follows: First, the workpiece to be processed is fed into the heating chamber at the front end of the pretreatment gas chamber, and the internal isolation door between the heating chamber and the rear vacuum chamber is closed to form an independent drying chamber. The electric heating system (such as an infrared radiation tube or silicon carbide rod) is then activated to perform preliminary drying of the workpiece under normal or slightly positive pressure, effectively removing surface free water and volatile cleaning residues. This stage avoids carbonization of contaminants due to high temperatures and provides residual heat for subsequent vacuum drying.

[0042] Subsequently, the internal isolation door is opened, and the workpiece is moved into the vacuum chamber via a conveying mechanism (such as a pusher or roller conveyor). The internal isolation door is then immediately closed, making the vacuum chamber a completely sealed cavity. The system then activates the evacuation device to rapidly reduce the pressure inside the chamber to a negative pressure state. At this time, the residual heat of the workpiece and the low-pressure environment create a synergistic effect: the residual heat provides desorption activation energy, and the negative pressure significantly lowers the boiling point of water and organic matter, thereby efficiently releasing adsorbed water and residual solvents trapped in threaded bottom holes, blind cavities, or assembly gaps. This design cleverly avoids the increased energy consumption and the risk of localized overheating caused by secondary heating of the workpiece. After deep drying is completed, high-purity protective gas (preferably fresh gas source to ensure cleanliness) is injected into the vacuum chamber through the gas filling system, making the pressure inside the chamber slightly higher than that inside the annealing furnace.

[0043] Finally, open the sealed isolation door between the vacuum chamber and the annealing furnace (usually a metal hard-seal pneumatic gate valve), and under positive pressure protection, smoothly send the workpiece into the main furnace, completely isolating external air from intrusion and effectively maintaining the stability of the reducing atmosphere inside the furnace.

[0044] Example 3 This embodiment discloses an annealing process for stainless steel materials. This process is based on the stainless steel annealing equipment described in Embodiment 1, and also uses a single-cavity integrated structure, but focuses on the synergistic optimization of gas-assisted heating and system pressure balance. See also... Figure 2 The specific operating procedure is as follows: First, the workpiece is loaded into a single pretreatment chamber and sealed completely. The vacuum system is then activated to create a negative pressure environment inside the chamber. Subsequently, the electric heating system is activated to dry the workpiece while maintaining the negative pressure, using the low pressure to accelerate the vaporization of moisture. After drying, the vacuum system is shut off, and protective gas is introduced for the first time (preferably using circulating gas from the main furnace to save energy), restoring a slight positive pressure inside the chamber.

[0045] The key innovation lies in the fact that during the initial gas filling process, the high-speed airflow disturbs the workpiece surface and microporous structure, potentially inducing the re-release of residual trace contaminants (such as adsorbed water molecules and organic vapors). At this point, a secondary gas extraction is performed, efficiently removing these newly generated impurities. Subsequently, the gas filling path is switched to a high-purity fresh gas source for a secondary gas filling, reconstructing an ultra-high cleanliness transition atmosphere. This "double extraction and double filling" operation significantly improves the purity of the atmosphere before furnace entry, eliminating uneven surface brightness or metallurgical performance fluctuations within the same furnace batch caused by trace contaminants, ensuring consistent annealing quality for high-end products.

[0046] Example 4 This embodiment discloses an annealing process for stainless steel materials. Based on the stainless steel annealing equipment described in Embodiment 1, this process is designed for single-chamber integrated pretreatment gas chambers and introduces a "secondary purification" mechanism, specifically for scenarios requiring high cleanliness (such as implantable medical devices and semiconductor fluid components). See also Figure 3 The specific operating procedure is as follows: After the workpiece is loaded and sealed, the vacuum system evacuates the cavity to a high vacuum level to remove ambient air and surface-adsorbed gases to the maximum extent. The vacuum system is then shut off, and the system switches to gas-assisted heating mode. Existing high-temperature nitrogen-hydrogen mixed protective gas is drawn from the annealing furnace via the gas filling system and introduced into the pretreatment gas chamber as a circulating heat carrier. The high-temperature gas forms a forced convection heat field within the cavity, penetrating dense threads, stacking gaps, or deep holes to achieve omnidirectional, penetrating heat exchange. This overcomes the problem of dead zones in electric heating radiation and significantly improves heating uniformity and desorption efficiency.

[0047] After drying, a second air extraction is performed to remove the trace amounts of organic residue newly released due to the impact of high-temperature gas; then the gas filling system is switched to a high-purity new gas source for a second gas filling, injecting clean protective gas to a slightly positive pressure state.

[0048] Of course, the above are just typical examples of the present invention. In addition, the present invention may have many other specific embodiments. All technical solutions formed by equivalent substitution or equivalent transformation fall within the scope of protection claimed by the present invention.

Claims

1. An annealing process for stainless steel materials, implemented using stainless steel annealing equipment, characterized in that, The annealing equipment includes an annealing furnace, the inlet of which is equipped with a pretreatment gas chamber. The pretreatment gas chamber is connected to the annealing furnace and a sealed isolation door is provided at the connection point. The pretreatment gas chamber has a heating system, a vacuum system, and a gas filling system. When the sealed isolation door is closed, the workpiece in the pretreatment gas chamber is dried by the heating system. The vacuum system evacuates the pretreatment gas chamber to a negative pressure state. After evacuation, the gas filling system fills the pretreatment gas chamber with protective gas, restoring the pressure of the pretreatment gas chamber to a slightly positive pressure state higher than the pressure inside the annealing furnace. Then, the sealed isolation door is opened, and the workpiece is sent into the annealing furnace, while ensuring that external air cannot flow back and that the protective atmosphere of the main furnace is not diluted or contaminated. The gas supply of the inflation system includes a circulating gas source and a fresh gas source. The circulating gas source uses the protective gas inside the annealing furnace. The heating system includes an electric heating mode and a gas-assisted heating mode. The gas-assisted heating mode uses the circulating gas source to introduce the high-temperature protective gas from the annealing furnace into the pretreatment gas chamber, which acts as a heat carrier to convectively heat the workpiece. The electric heating mode uses electric heating elements installed on the wall or internal support of the pretreatment gas chamber to directly or radiate heat the workpiece. The pretreatment gas chamber includes a heating chamber with a heating system and a vacuum chamber with a pumping system and a filling system. The heating chamber and the vacuum chamber are arranged adjacent to each other and are connected by an internal isolation door. The annealing process includes the following steps: Step 1: Send the workpiece to be processed into the heating chamber of the pretreatment gas chamber. After closing the internal isolation door between the heating chamber and the vacuum chamber, start the heating system to pre-dry the workpiece. Step 2: Then open the internal isolation door, transfer the workpiece to the vacuum chamber, and close the internal isolation door to form a sealed cavity in the vacuum chamber; Start the vacuum system to evacuate the vacuum chamber to a negative pressure state, so as to reduce the desorption temperature of moisture and adsorbed gas and achieve deep drying. After the vacuuming is completed, protective gas is injected into the vacuum chamber through the gas filling system to restore the pressure inside the chamber to a slightly positive pressure state that is higher than the pressure inside the annealing furnace. Step 3: Open the sealed isolation door between the vacuum chamber and the annealing furnace, and send the workpiece into the annealing furnace for subsequent heat treatment.

2. An annealing process for stainless steel materials, implemented using stainless steel annealing equipment, characterized in that, The annealing equipment includes an annealing furnace, the inlet of which is equipped with a pretreatment gas chamber. The pretreatment gas chamber is connected to the annealing furnace and a sealed isolation door is provided at the connection point. The pretreatment gas chamber has a heating system, a vacuum system, and a gas filling system. When the sealed isolation door is closed, the workpiece in the pretreatment gas chamber is dried by the heating system. The vacuum system evacuates the pretreatment gas chamber to a negative pressure state. After evacuation, the gas filling system fills the pretreatment gas chamber with protective gas, restoring the pressure of the pretreatment gas chamber to a slightly positive pressure state higher than the pressure inside the annealing furnace. Then, the sealed isolation door is opened, and the workpiece is sent into the annealing furnace, while ensuring that external air cannot flow back and that the protective atmosphere of the main furnace is not diluted or contaminated. The gas supply of the inflation system includes a circulating gas source and a fresh gas source. The circulating gas source uses the protective gas inside the annealing furnace. The heating system includes an electric heating mode and a gas-assisted heating mode. The gas-assisted heating mode uses the circulating gas source to introduce the high-temperature protective gas from the annealing furnace into the pretreatment gas chamber, which acts as a heat carrier to convectively heat the workpiece. The electric heating mode uses electric heating elements installed on the wall or internal support of the pretreatment gas chamber to directly or radiate heat the workpiece. The heating system, extraction system and inflation system of the pretreatment gas chamber are located in the same chamber; The annealing process includes the following steps: Step 1: Place the workpiece in the pretreatment chamber and seal the chamber; Step 2: Activate the vacuum system to create a negative pressure environment inside the cavity; Step 3: Start the heating system while maintaining negative pressure to dry the workpiece; Step 4: After drying is complete, turn off the exhaust system and fill the chamber with protective gas through the gas filling system to restore the pressure inside the chamber to a slightly positive pressure state higher than that of the annealing furnace. Step 5: Perform a second evacuation to remove residual impurities released due to inflation disturbance; then refill with protective gas to complete the second pressurization. Step Six: Open the sealed isolation door between the pretreatment chamber and the annealing furnace, and send the workpiece into the annealing furnace for subsequent heat treatment.

3. An annealing process for stainless steel materials, implemented using stainless steel annealing equipment, characterized in that, The annealing equipment includes an annealing furnace, the inlet of which is equipped with a pretreatment gas chamber. The pretreatment gas chamber is connected to the annealing furnace and a sealed isolation door is provided at the connection point. The pretreatment gas chamber has a heating system, a vacuum system, and a gas filling system. When the sealed isolation door is closed, the workpiece in the pretreatment gas chamber is dried by the heating system. The vacuum system evacuates the pretreatment gas chamber to a negative pressure state. After evacuation, the gas filling system fills the pretreatment gas chamber with protective gas, restoring the pressure of the pretreatment gas chamber to a slightly positive pressure state higher than the pressure inside the annealing furnace. Then, the sealed isolation door is opened, and the workpiece is sent into the annealing furnace, while ensuring that external air cannot flow back and that the protective atmosphere of the main furnace is not diluted or contaminated. The gas supply of the inflation system includes a circulating gas source and a fresh gas source. The circulating gas source uses the protective gas inside the annealing furnace. The heating system includes an electric heating mode and a gas-assisted heating mode. The gas-assisted heating mode uses the circulating gas source to introduce the high-temperature protective gas from the annealing furnace into the pretreatment gas chamber, which acts as a heat carrier to convectively heat the workpiece. The electric heating mode uses electric heating elements installed on the wall or internal support of the pretreatment gas chamber to directly or radiate heat the workpiece. The heating system, extraction system and inflation system of the pretreatment gas chamber are located in the same chamber; The annealing process includes the following steps: Step 1: Place the workpiece in the pretreatment chamber and seal the chamber; Step 2: Activate the vacuum system to evacuate the cavity to a vacuum state; Step 3: Turn off the exhaust system and switch to gas-assisted heating mode. Introduce circulating gas from the annealing furnace through the gas filling system to introduce high-temperature protective gas into the chamber for convective heating and drying of the workpiece. Step 4: After drying, perform a second air extraction operation to remove any trace impurities newly released due to heating and gas disturbance. Step 5: Switch the inflation system to a new gas source and perform secondary inflation, injecting high-purity protective gas to make the pressure inside the cavity reach a slightly positive pressure state higher than that of the annealing furnace; Step Six: Open the sealed isolation door between the pretreatment chamber and the annealing furnace, and send the workpiece into the annealing furnace for subsequent heat treatment.

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