Controllable atmosphere carburizing apparatus and method for through vacuum heating

Abstract

The invention relates to a controlled atmosphere carburizing apparatus and method through vacuum heating. The equipment comprises a vacuum heating chamber, a vacuum oil quenching chamber, a gate valve, a conveying device, a vacuum pump, an oxygen probe, an inflation system, a controllable atmosphere carburizing system and an air exhaust system. According to the equipment and the method, existing double-chamber vacuum heat treatment equipment is improved, the controllable atmosphere carburizing process is combined with vacuum heating and vacuum quenching, the advantages of vacuum heat treatment and controllable atmosphere carburizing are absorbed, the problems that in the controllable atmosphere carburizing process, oxidation exists in a carburizing layer, and the explosion risk exists are solved, and the service life of the carburizing layer is prolonged. And the problems of substandard carbide grade at the sharp corner, poor uniformity of a carburized layer, serious carbon black and the like in a vacuum carburizing process are also solved.

Description

Technical Field

[0001] The present application relates to the field of heat treatment technology, and in particular to a controlled atmosphere carburizing device and method with vacuum heating. Background Art

[0002] Vacuum carburizing is a new technology developed in the heat treatment industry in recent years. It offers numerous advantages over conventional carburizing, including rapid carburizing, environmental friendliness, energy savings, ease of operation, and the absence of gas explosion risk. However, even within the context of my country's "dual carbon" policy, this energy-saving and environmentally friendly vacuum carburizing technology remains largely unused. The main reasons for this are: 1. The carburizing atmosphere, an uncontrollable hydrocarbon cracking gas, is unable to decarburize the carbon content of the carburized layers on the various surfaces of the steel. Consequently, the carbon content at sharp corners of the workpiece, resulting from three-dimensional carburization, is too high to be decarburized by the gas, resulting in excessive carbide levels. Furthermore, if the hydrocarbon gas and cracked carbon atoms are not sprayed or spilled onto the workpiece (steel) surface, no carburized layer will form on the workpiece, rendering the workpiece scrapped. This can even result in the entire furnace of carburized workpieces (dozens or even hundreds) being scrapped. ② The uniformity of the carburized layer is affected by the number, geometry, total surface area, and stacking density of the workpieces being carburized within the furnace. If any of these conditions change, uniformity of the carburized layer becomes difficult to guarantee, and individual workpieces may even experience missed carburization. Therefore, extensive testing is required to ensure that the hydrocarbon gas nozzles within the furnace reach every workpiece surface to achieve the required uniformity. ③ This can lead to the generation of large amounts of carbon black within the furnace, which in severe cases can affect the normal operation of the equipment, increase maintenance costs, and reduce its service life.

[0003] Compared to vacuum carburizing, controlled atmosphere carburizing has a longer history and is more widely used. After decades of development, the technology has matured, delivering excellent carburizing results and high equipment reliability. This carburizing atmosphere, a controllable water-gas dynamic equilibrium reaction gas, effectively addresses defects encountered in vacuum carburizing processes, such as substandard carbide levels at sharp corners, poor carburized layer uniformity, and significant carbon black. However, its drawbacks are also significant compared to vacuum carburizing: ① Internal oxidation of the carburized layer surface. ② Large amounts of hydrocarbons must be introduced into the furnace at all times during the process curve to maintain a positive pressure inside the furnace to prevent air inhalation from causing carburizing gas explosions. This not only wastes significant energy but also pollutes the environment. Summary of the Invention

[0004] In view of the problems existing in the above-mentioned existing vacuum carburizing and controlled atmosphere carburizing technologies, the purpose of the present invention is to provide a controlled atmosphere carburizing equipment that is heated through vacuum, which is combined with the existing double-chamber vacuum heat treatment equipment and has the ability to perform vacuum heating, vacuum quenching and controlled atmosphere carburizing treatment by adding an exhaust system, a controlled atmosphere carburizing system, and an oxygen probe sealing device. The controlled atmosphere carburizing equipment that is heated through vacuum of the present invention has the airtightness of a vacuum, is low-pressure during carburizing, and is heated in a vacuum environment in the remaining sections, eliminating the risk of gas explosion in the controlled atmosphere carburizing process. The controlled atmosphere carburizing equipment that is heated through vacuum of the present invention combines the advantages of vacuum heat treatment and controlled atmosphere carburizing processes, not only solving the problems of oxidation and explosion risk in the carburized layer during the controlled atmosphere carburizing process, but also solving the problems of substandard carbide levels at sharp corners, poor uniformity of the carburized layer, and severe carbon black in the vacuum carburizing process. The controlled atmosphere carburizing equipment that is heated through vacuum of the present invention maintains the advantages of energy saving, environmental protection, ease of operation, and workpiece surface activation brought about by the vacuum heating characteristics, so that it can achieve a fast carburizing speed.

[0005] In order to achieve the above-mentioned objectives, the present application provides a controlled atmosphere carburizing equipment with vacuum heating throughout, comprising: a vacuum heating chamber, a vacuum oil quenching chamber, a gate valve, a conveying device, a vacuum pump, an oxygen probe, an air charging system, a controlled atmosphere carburizing system and an exhaust system; the vacuum heating chamber is configured to heat a workpiece in a vacuum environment; the vacuum oil quenching chamber is configured to quench the workpiece with oil in a vacuum environment; the gate valve is configured to control the connection and sealing of the vacuum heating chamber and the vacuum oil quenching chamber; the conveying device is configured to transfer the workpiece between the vacuum heating chamber and the vacuum oil quenching chamber through the gate valve; the vacuum pump is configured to provide a vacuum environment for the vacuum heating chamber and the vacuum oil quenching chamber respectively; the air charging system is configured to drip methanol liquid into the vacuum heating chamber according to the air pressure of the vacuum heating chamber; the oxygen probe is configured to detect the oxygen potential of the vacuum heating chamber; the controlled atmosphere carburizing system is configured to charge the vacuum heating chamber with enriched gas acetone liquid according to the oxygen potential detected by the oxygen probe; and the exhaust system is configured to exhaust the vacuum heating chamber according to the air pressure of the vacuum heating chamber.

[0006] In a possible embodiment of the controlled atmosphere carburizing equipment with vacuum heating throughout, the inflation system and the exhaust system are configured to repeat the following operations in the carburizing section: when the pressure of the vacuum heating chamber is higher than a first predetermined pressure, the inflation system stops inflating the vacuum heating chamber and the exhaust system starts exhausting; when the pressure of the vacuum heating chamber is lower than a second predetermined pressure, the exhaust system stops exhausting the vacuum heating chamber and the inflation system starts inflating.

[0007] In a possible embodiment of a controlled atmosphere carburizing device with vacuum heating throughout, the oxygen probe is sealed in a sealing device, and the sealing device includes a first solenoid valve, a second solenoid valve and a third solenoid valve, wherein the first solenoid valve is connected to a reference gas air pump pipeline, the second solenoid valve is connected to the atmosphere, and the third solenoid valve is connected to the exhaust system.

[0008] In a possible implementation of the controlled atmosphere carburizing equipment with vacuum heating, the first predetermined pressure is 50-70 KPa, and the second predetermined pressure is 20-40 KPa.

[0009] In one possible embodiment of a controlled atmosphere carburizing device with vacuum heating, the controlled atmosphere carburizing system includes a carbon controller and a dripping device. The carbon controller controls the dripping device to drip enriched gas acetone liquid into the vacuum heating chamber according to the oxygen potential measured by the oxygen probe, thereby causing the oxygen potential of the vacuum heating chamber to fluctuate within 1200-1300 mV.

[0010] In order to achieve the above-mentioned purpose, the present application also provides a method for controlled atmosphere carburizing throughout vacuum, which uses a vacuum heating chamber to heat the workpiece to the carburizing temperature and keep it warm to austenitize it in the vacuum environment provided by a vacuum pump; uses an oxygen probe, an inflation system, a controlled atmosphere carburizing system and an exhaust system connected to the vacuum heating chamber to perform controlled atmosphere carburizing on the workpiece in the vacuum heating chamber, wherein, when the pressure of the vacuum heating chamber is higher than a first predetermined pressure, the inflation system stops inflating the vacuum heating chamber and the exhaust system starts exhausting, and when the pressure of the vacuum heating chamber is lower than a second predetermined pressure, the exhaust system stops exhausting the vacuum heating chamber and the inflation system starts inflating; uses a conveying mechanism to send the workpiece into the vacuum oil quenching chamber via a gate valve, and quenches the workpiece in the vacuum environment provided by the vacuum pump.

[0011] In a possible embodiment of the controlled atmosphere carburizing method with vacuum heating, during the controlled atmosphere carburizing, the oxygen potential of the vacuum heating chamber is fluctuated within a range of 1200-1300 mV by means of the controlled atmosphere carburizing system.

[0012] In a possible implementation of the controlled atmosphere carburizing method with vacuum heating, the first predetermined pressure is 50-70 KPa, and the second predetermined pressure is 20-40 KPa.

[0013] The controlled atmosphere carburizing equipment and method disclosed in the present invention, which run through a vacuum heating process, combine the advantages of vacuum heat treatment and controlled atmosphere carburizing processes. They not only address the problems of oxidation within the carburized layer, explosion risks, energy waste, and environmental pollution that exist in the controlled atmosphere carburizing process, but also address issues such as unqualified carbide levels at sharp corners, poor carburized layer uniformity, and severe carbon black that exist in vacuum carburizing processes. Because the workpiece being treated is heated and quenched in a vacuum environment, oxidation and decarburization do not occur, which is energy-saving and environmentally friendly. At the same time, surface degreasing and degassing also accelerates the carburizing process, resulting in a clean and bright surface for the workpiece after carburizing.

[0014] In the controlled atmosphere carburizing equipment and controlled atmosphere carburizing method of the present invention that runs through the vacuum heating process, the workpiece to be carburized completes the heating-average temperature-cooling-average temperature quenching steps in the process curve under a vacuum environment, which account for 3 / 4 of the entire process curve. In this environment, the workpiece surface is not oxidized, decarburized, or carburized, which not only saves energy but also reduces environmental pollution. In the remaining 1 / 4 of the time, the workpiece undergoes a controlled atmosphere carburizing process, which effectively avoids the explosion of carburizing gas and the accumulation of carbon black in the furnace; and through the inflation / exhaust cycle operation, the gas in the furnace is physically agitated, greatly improving the uniformity of carburizing. The mechanical properties of the workpiece treated by this equipment are greatly improved. Due to the use of a controlled atmosphere carburizing process, almost no carbon black is generated in the furnace, which improves the utilization rate of the equipment and reduces maintenance costs. The equipment has a sophisticated structure, is easy to operate, and has a high degree of adaptability. It is applicable to carburizing and vacuum heat treatment of various types of steel, has high versatility (one machine for multiple uses), and has significant economic and environmental benefits.

[0015] The above content of the present application will be more concise and understandable in the following description of multiple embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The following are the drawings of the present application. These drawings are only for presenting the present application in a more intuitive form. They are exemplary and are not intended to limit the scope of the present application.

[0017] Figure 1 This is a structural block diagram of a controlled atmosphere carburizing device with vacuum heating according to one embodiment of the present application.

[0018] Figure 2 This is a schematic structural diagram of a controlled atmosphere carburizing device with vacuum heating according to one embodiment of the present application.

[0019] Figure 3 Schematic diagram of the structure of a carburizing atmosphere control sealing device according to one embodiment of the present application.

[0020] Figure 4 Picture of the carburized layer of the carburized workpiece.

[0021] Reference numerals

[0022] 1-Vacuum oil quenching chamber furnace door, 2-Quenching lifting mechanism, 3-Quenching oil tank, 4-Vacuum oil quenching chamber nitrogen supply connection, 5-Transfer mechanism, 6, 8-Main pumps, 7-Gate valve, 9-Workpiece to be processed, 10-Oxygen probe sealing device and auxiliary pump, 11-Drip device, 12-Vacuum heating chamber furnace door; 21-K1 valve, 22-K2 valve, 23-K3 valve, 24-Baffle valve 3, 25-Baffle valve 5, 26-Sealing device cover, 27-Support mounting pipe, 28-Oxygen probe, 29-Vacuum heating chamber upper wall. DETAILED DESCRIPTION

[0023] In order to make this application easier to understand, the present application is further described below with reference to specific examples. The experimental methods described in this application are conventional methods unless otherwise specified; the materials described are commercially available unless otherwise specified. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by technicians in the technical field of this application. In the event of any inconsistency, the meaning described in this specification or the meaning derived from the contents recorded in this specification shall prevail. In addition, the terms used herein are only for the purpose of describing the embodiments of this application and are not intended to limit this application.

[0024] In order to accurately describe the technical content in this application and to accurately understand the present invention, the following explanations or definitions are given for the words and terms used in this specification before describing the specific implementation methods.

[0025] As used in this specification, the phrases "one embodiment" or "an embodiment" mean that a particular feature, step, or characteristic described in connection with that embodiment is included in at least one embodiment of the present invention. Thus, the phrases "in one embodiment" or "in an embodiment" appearing throughout this specification do not necessarily refer to the same embodiment, but may do so. Furthermore, in one or more embodiments, the particular features, steps, or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure.

[0026] The purpose of the present invention is to disclose a controlled atmosphere carburizing device that runs through a vacuum heating process, in order to solve the above-mentioned and / or existing problems in the existing vacuum and controlled atmosphere carburizing technology. The present invention improves the existing double-chamber vacuum heat treatment equipment, combines the controlled atmosphere carburizing process with vacuum heating and vacuum quenching, absorbs the advantages of vacuum heat treatment and controlled atmosphere carburizing, and not only solves the problems of oxidation and explosion risk in the carburized layer during the controlled atmosphere carburizing process, but also solves the problems of substandard carbide levels at sharp corners, poor uniformity of the carburized layer, and serious carbon black in the vacuum carburizing process. The advantages of energy saving, environmental protection, simple operation, and workpiece surface activation brought by the vacuum heating characteristics are maintained, so that the carburizing speed is fast.

[0027] The term "through vacuum heating" as used in the specification and claims refers to a process that organically combines vacuum heat treatment and controlled atmosphere heat treatment. In the through vacuum heating of the present invention, the entire process begins and ends in a vacuum environment, with the intermediate controlled atmosphere heat treatment operating at a controlled pressure.

[0028] like Figure 1 and 2 As shown, in one embodiment of the present application, a controlled atmosphere carburizing apparatus with vacuum heating includes a vacuum heating chamber, a vacuum oil quenching chamber, a gate valve between the vacuum heating chamber and the vacuum oil quenching chamber, an air charging system, a controlled atmosphere carburizing system, and an exhaust system, each connected to the vacuum heating chamber. A main vacuum pump is connected to the vacuum heating chamber and the vacuum oil quenching chamber, respectively. One side of the vacuum oil quenching chamber (furnace door) serves as the loading / unloading port, while the other side is connected to the vacuum heating chamber via a gate valve. A quenching oil tank and a quenching lifting mechanism are located within the vacuum oil quenching chamber. The vacuum oil quenching chamber and the vacuum heating chamber are separated by a gate valve into two separate chambers. The main pump evacuates the gas in each chamber via pipes and electric valves to the required vacuum level in each chamber. The vacuum level in the vacuum heating chamber is 0.13 Pa. During the carburizing process, the vacuum level in the vacuum oil quenching chamber is ≤13 Pa, and the damper valves 1 and 2 connecting the main pump to the two chambers are closed, leaving the gas in both chambers static. After that, the vacuum oil quenching chamber uses high-purity nitrogen to increase the chamber pressure from ≦13Pa to 80KPa to tighten the gate valve, preparing for the carburizing process.

[0029] The aeration system consists of a pressurized tank, a flowmeter, a solenoid valve, a dripping device, and a pressure gauge. The pressurized tank is filled with methanol liquid, which is pressurized to 40 kPa with high-purity nitrogen. Under pressure, the methanol liquid drips through the dripping device via the flowmeter and solenoid valve into the vacuum heating chamber, where it is cracked to form a carburizing carrier gas (1 / 3 CO + 2 / 3 H2). The exhaust system consists of an auxiliary pump, baffle valves 4 and 5, and a pipeline connected to the vacuum heating chamber. During the controlled atmosphere carburizing process, the auxiliary pump is always running, baffle valve 4 is closed, and carrier gas (1 / 3 CO + 2 / 3 H2) is introduced into the furnace via the aeration system, rapidly increasing the furnace pressure from 0.13 Pa. When the electric contact pressure gauge reaches 60 kPa, baffle valve 4 is commanded to open, and the auxiliary pump is exhausted. When the electric contact pressure gauge reaches 30 kPa, baffle valve 4 is commanded to close, and exhaust stops. The solenoid valve of the gas charging system opens, and the carrier gas is charged into the furnace. When the pressure in the furnace rises back to 60KPa, the solenoid valve of the gas charging system closes, the baffle valve 4 opens, and the auxiliary pump pumps gas to 30KPa. This cycle repeats until the carburizing process is completed.

[0030] The controlled atmosphere carburizing system consists of a pressurized tank, flowmeter, solenoid valve, dripping device, and carbon controller. The carbon controller compares the oxygen partial pressure detected by the oxygen probe (discussed later) with the pre-set oxygen partial pressure carbon potential curve. It then commands the solenoid valve to open / close, dripping enriched acetone liquid into / from the vacuum heating chamber via the pressurized tank, flowmeter, and dripping device, achieving real-time control of the carbon potential.

[0031] The oxygen probe is connected to the vacuum heating chamber, with its end inserted 80mm into the furnace, and is used to detect the oxygen partial pressure in the carburizing atmosphere in real time and transmit its signal to the aforementioned carbon control instrument. To ensure the airtightness of the entire equipment, the oxygen probe is sealed in a sealing device. Figure 3 As shown, the sealing device primarily consists of sealing device sidewalls, a sealing device cover plate 6, and a support mounting tube. The sealing device seals the portion of the oxygen probe protruding from the upper wall of the vacuum heating chamber. Three solenoid valves, designated K1, K2, and K3, are installed on the sealing device sidewalls. K1 is connected to the oxygen probe reference gas air pump pipeline; K2 is open to the atmosphere; and K3 is connected to the damper valve 3 connected to the main pump and the damper valve 5 connected to the auxiliary pump. The sealing device is not connected to the vacuum heating chamber. During the controlled atmosphere carburizing phase of vacuum heating, solenoid valves K1 and K2 are open, while K3 is closed. K1's function is to pump air reference gas into the bottom of the sealing device through the oxygen probe's internal pipeline and then discharge the gas through the return pipeline and K2. During other periods, solenoid valves K1 and K2 are closed. During these periods, K3 is open, and through damper valve 3, the pressure in the reference gas pipeline and sealing device is the same as the pressure in the heating chamber. This allows the vacuum heating process to be carried out at a vacuum level of 0.13 Pa.

[0032] The running trajectory of the workpiece to be carburized in the equipment of the present invention is as follows: the workpiece is sent to the conveying mechanism of the vacuum oil quenching chamber, the furnace door is closed - the vacuum oil quenching chamber / vacuum heating chamber is evacuated - the gate valve is opened, the workpiece is conveyed to the vacuum heating chamber through the conveying mechanism - the conveying mechanism returns to the vacuum oil quenching chamber, the gate valve is closed - the workpiece is subjected to vacuum heating, controlled atmosphere carburizing, and cooled to the quenching temperature - the gate valve is opened, the conveying mechanism enters the vacuum heating chamber and retrieves the workpiece to the vacuum oil quenching chamber - the gate valve is closed, the quenching mechanism holds up the workpiece - the quenching mechanism and the workpiece are put into oil quenching together - after quenching is completed, the workpiece is lifted onto the conveying mechanism of the vacuum oil quenching chamber, the vacuum oil quenching chamber furnace door is opened, the workpiece is taken out, and the entire operation is completed.

[0033] In addition to the aforementioned key components and workpiece trajectory, the equipment also includes other related sensors (such as pressure gauges), monitoring systems, and an operator interface. These monitor various parameters of the heating, carburizing, and quenching processes in real time and provide corresponding control and adjustment functions to achieve precise control and monitoring of the heating, carburizing, and quenching processes, ensuring workpiece quality and consistency. The specific configuration and components can be designed and installed according to actual needs to ensure stable operation and safety performance.

[0034] In this embodiment, a workpiece to be carburized and a test sample are placed in the vacuum heating chamber.

[0035] The workpiece is a worm, and its dimensions are: The material is 20CrMo steel, and the chemical composition (mass percentage) is: 0.2% C, 0.25% Si, 1.0% Cr, 0.4% Mn, 0.2% Mo, and the rest Fe.

[0036] 2 test specimens, dimensions: / ×5mm. Material: 20CrMo steel and T12 steel, the chemical composition (mass percentage) of T12 steel is: 1.2% C, the rest Fe.

[0037] This embodiment includes the following steps:

[0038] S1: Heat the workpiece to the carburizing temperature in a vacuum environment and keep it at this temperature for a certain period of time to austenitize it.

[0039] Specifically, refer to Figure 1 , start the main vacuum pump and its damper valves 1, 2, and 3, and simultaneously evacuate the vacuum heating chamber and the vacuum oil quenching chamber until the vacuum degree in both chambers reaches 0.13 Pa. In the vacuum heating chamber, heat the workpiece to 930°C in a vacuum environment with a vacuum degree of 0.13 Pa and hold it for 30 minutes to fully austenitize it in preparation for the carburizing process.

[0040] S1.1 Open the main vacuum pump and its three front flapper valves 1, 2, and 3, and pump the vacuum to 0.13 Pa in the two chambers and the oxygen probe sealing device. Close the three flapper valves 1, 2, and 3 of the vacuum pump to make the gas in the vacuum heating chamber and vacuum oil quenching chamber still.

[0041] S1.2 Open the charging solenoid valve of the vacuum heating chamber, fill it with high-purity nitrogen to increase the pressure in the chamber from ≦13Pa to 80KPa, tighten the gate valve, and prepare for carburizing.

[0042] S1.3, start the oxygen probe. Figure 3 , open solenoid valves K1 and K2, close solenoid valve K3, start the air reference gas pump, and fill air into the built-in reference tube of the oxygen probe to ensure that the oxygen probe detects the oxygen partial pressure in the furnace accurately. At this time, the oxygen probe sealing device is connected to the atmosphere.

[0043] S2: Operate the filling / exhaust system to perform the controlled atmosphere carburizing process.

[0044] Specifically, refer to Figure 1 , start the auxiliary pump and close damper valve 4. Start the aeration system and the solenoid valve. Using a dripping device, methanol liquid from the sealed tank is dripped into the vacuum heating chamber via a flowmeter to decompose and form a carburizing carrier gas. When the pressure gauge of the aeration system detects that the chamber pressure reaches 60 kPa, damper valve 4 of the exhaust system opens and begins extraction. When the pressure gauge detects that the chamber pressure reaches 30 kPa, damper valve 4 of the exhaust system closes and stops extraction. The aeration system continues to operate, dripping methanol liquid into the vacuum heating chamber to decompose and generate gas, raising the chamber pressure back to 60 kPa. This cycle repeats, maintaining the chamber pressure between 30 kPa and 60 kPa. Theoretically, at 930°C and an atmospheric carbon potential of 1.0%C, the corresponding oxygen potential is 1244 ± 2 mV. This value is input into the carbon control instrument. During the carburizing process, an oxygen probe continuously monitors the oxygen potential in the vacuum heating chamber atmosphere and transmits it to the carbon control instrument of the controlled atmosphere carburizing system at microsecond speeds. The carbon controller receives input from the oxygen probe. When the oxygen potential in the atmosphere falls below 1244 mV, it commands the solenoid valve of the controlled atmosphere carburizing system to open and the dripping device to drip enriched acetone into the furnace, raising the oxygen potential. When the oxygen potential in the atmosphere rises above 1244 mV, the carbon controller commands the solenoid valve to close and the dripping device to stop dripping acetone. This keeps the oxygen potential in the vacuum heating chamber within the range of 1244 ± 2 mV. This dynamic equilibrium is maintained until the carburizing process is complete. The carburizing time is 60 minutes.

[0045] S3: Carburizing is completed, and the auxiliary pump and the baffle valve 4 are closed. The main vacuum pump is used to evacuate the vacuum heating chamber again, and the workpiece is transferred to the vacuum oil quenching chamber for vacuum quenching process.

[0046] Specifically, after the carburizing process is completed, the baffle valve 4 is closed and the Figure 3 , close the solenoid valves K1 and K2, open K3 and the baffle valve 5, and evacuate the oxygen probe sealing device until the pressure gauge on the sealing device shows 0.13Pa, then close the auxiliary pump and the baffle valve 5. Thus, after the carburizing process is completed, the inoperative oxygen probe is sealed in the sealing device to ensure the overall vacuum degree. Figure 1 , open the two damper valves 1 and 2 leading from the main vacuum pump to the vacuum heating chamber and vacuum oil quenching chamber, and re-evacuate both chambers to 0.13 Pa. The workpiece in the vacuum heating chamber is cooled to the quenching temperature and held at that temperature for 30 minutes before the gate valve is opened. The conveyor mechanism in the vacuum oil quenching chamber follows the track into the vacuum heating chamber, lifts the carburized workpiece, and returns it to the vacuum oil quenching chamber. The gate valve drops and closes; the quenching mechanism rises, lifting the workpiece, and then drops it and the workpiece into the oil for quenching. Simultaneously, nitrogen is introduced into the vacuum oil quenching chamber to a furnace pressure of 40 kPa. The quenching mechanism removes the quenched workpiece from the oil. The vacuum oil quenching chamber is then inflated to atmospheric pressure, the vacuum oil quenching chamber door is opened, and the workpiece is removed. The process is complete.

[0047] In summary, the controlled atmosphere carburizing equipment, which operates throughout the vacuum heating process, first utilizes vacuum heating to heat the workpiece to the carburizing temperature within the vacuum heating chamber and austenitize it. Then, the main pump's damper valves 1, 2, and 3 are closed, the auxiliary pump and pre-damper valve 4 are opened, and the aeration system is activated, continuously dripping methanol for aeration. Acetone is then dripped into the workpiece for carburization, and the furnace pressure is maintained by intermittent vacuum pumping. This pumping also stirs the furnace atmosphere, improving carburization uniformity. After carburizing for a specified period, the vacuum heating chamber and vacuum oil quenching chamber are evacuated again. Once the pressures are consistent, the gate valve is opened to return the workpiece to the vacuum oil quenching chamber for vacuum quenching. The present invention improves upon existing dual-chamber vacuum heat treatment equipment, combining a controlled atmosphere carburizing process with vacuum heating and vacuum quenching. This combines the advantages of both vacuum heat treatment and controlled atmosphere carburizing, resolving the issues of oxidation within the carburized layer during controlled atmosphere carburizing and the need to inject large amounts of hydrocarbons into the furnace throughout each process stage to maintain a positive pressure, leading to energy waste and environmental pollution. It also addresses issues such as substandard carbide levels at sharp corners, poor carburized layer uniformity, and significant carbon black in the vacuum carburizing process. The present invention maintains the advantages of vacuum heating, including energy conservation, environmental protection, ease of operation, and workpiece surface activation for faster carburizing.

[0048] By using the controlled atmosphere carburizing equipment of the present invention throughout the vacuum heating process, the 20CrMo steel worm of the above embodiment is carburized and quenched. The test results are as follows: Figure 4As shown (20CrMo on the left, T12 on the right), the carburized layer is well-uniformed, with a thickness of 0.37 mm formed after carburization. The surface exhibits a eutectic structure (1.0% carbon content), and there is no internal oxidation on the carburized layer. This meets the workpiece's technical requirements. No carbon black deposits were observed in the furnace.

[0049] Using the controlled atmosphere carburizing equipment of the present invention, which performs a vacuum heating process, 20CrMo and T12 steel samples from the above-described embodiment were carburized and quenched, followed by vacuum annealing. The results showed that after carburizing, the 20CrMo steel formed a 0.37mm carburized layer with a surface structure of eutectoid (1.0% carbon content), while the T12 steel formed a 0.06mm decarburized layer with a surface structure of eutectoid (1.0% carbon content). Their carbon contents were essentially equal, demonstrating the existence of a water-gas chemical equilibrium reaction in the carburizing atmosphere. When the carbon potential in the carburizing atmosphere is 1.0% carbon, low-carbon steel (20CrMo steel containing 0.2% carbon) is carburized, while high-carbon steel (T12 steel containing 1.2% carbon) is decarburized under these conditions. This demonstrates the feasibility of the controlled atmosphere carburizing process of the present invention, applying the principles and processes of controlled atmosphere carburizing.

[0050] The above are only preferred embodiments of the present application and the technical principles employed. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and that various obvious changes, readjustments, and substitutions can be made by those skilled in the art without departing from the scope of protection of the present application. Therefore, although the present application has been described in more detail through the above embodiments, the present application is not limited to the above embodiments and may include many other equivalent embodiments without departing from the scope of protection of the present application.

Claims

1. A vacuum-controlled atmosphere carburizing apparatus comprising: Vacuum heating chamber, vacuum oil quenching chamber, gate valve, conveyor, vacuum pump, oxygen probe, charging system, controlled atmosphere carburizing system and exhaust system; The vacuum heating chamber is configured to heat the workpiece in a vacuum environment; The vacuum oil quenching chamber is configured to quench the workpiece with oil under a vacuum environment; The gate valve is configured to control the communication and closing of the vacuum heating chamber and the vacuum oil quenching chamber; The conveying device is configured to convey the workpiece between the vacuum heating chamber and the vacuum oil quenching chamber through the gate valve; The vacuum pump is configured to provide a vacuum environment for the vacuum heating chamber and the vacuum oil quenching chamber respectively; The inflation system is configured to drip methanol liquid into the vacuum heating chamber according to the air pressure of the vacuum heating chamber; The oxygen probe is configured to detect the oxygen potential of the vacuum heating chamber; The controlled atmosphere carburizing system is configured to fill the vacuum heating chamber with an enriched gas acetone liquid according to the oxygen potential detected by the oxygen probe; and The exhaust system is configured to exhaust the vacuum heating chamber according to the air pressure of the vacuum heating chamber.

2. The vacuum controlled atmosphere carburizing equipment according to claim 1, wherein: The inflation system and the exhaust system are configured to repeat the following operations in the carburizing section: when the pressure of the vacuum heating chamber is higher than a first predetermined pressure, the inflation system stops inflating the vacuum heating chamber and the exhaust system starts exhausting; and when the pressure of the vacuum heating chamber is lower than a second predetermined pressure, the exhaust system stops exhausting the vacuum heating chamber and the inflation system starts inflating.

3. The vacuum controlled atmosphere carburizing equipment according to claim 1, wherein: The oxygen probe is sealed in a sealing device, which includes a first solenoid valve, a second solenoid valve and a third solenoid valve, wherein the first solenoid valve is connected to the reference gas air pump pipeline, the second solenoid valve is connected to the atmosphere, and the third solenoid valve is connected to the exhaust system.

4. The vacuum controlled atmosphere carburizing equipment according to claim 1, wherein: The first predetermined pressure is 50-70 KPa, and the second predetermined pressure is 20-40 KPa.

5. The vacuum controlled atmosphere carburizing equipment according to claim 1, wherein: The controlled atmosphere carburizing system includes a carbon controller and a dripping device. The carbon controller controls the dripping device to drip enriched gas acetone liquid into the vacuum heating chamber according to the oxygen potential measured by the oxygen probe, thereby causing the oxygen potential of the vacuum heating chamber to fluctuate within 1200-1300 mV.

6. A through-vacuum controlled atmosphere carburizing method, implemented by means of the through-vacuum controlled atmosphere carburizing apparatus according to any one of claims 1 to 5, comprising: With the help of a vacuum heating chamber, the workpiece is heated to the carburizing temperature under the vacuum environment provided by the vacuum pump and kept warm to austenitize; Carburizing the workpiece in the vacuum heating chamber under controlled atmosphere by means of an oxygen probe, a gas charging system, a controlled atmosphere carburizing system, and an exhaust system connected to the vacuum heating chamber, wherein when the pressure of the vacuum heating chamber is higher than a first predetermined pressure, the gas charging system stops charging the vacuum heating chamber and the exhaust system starts exhausting the air; and when the pressure of the vacuum heating chamber is lower than a second predetermined pressure, the exhaust system stops exhausting the vacuum heating chamber and the gas charging system starts charging the chamber; The workpiece is conveyed into a vacuum oil quenching chamber via a gate valve by means of a conveying mechanism, and is quenched in a vacuum environment provided by the vacuum pump.

7. The method of carburizing in a controlled atmosphere through vacuum according to claim 6, wherein: During the controlled atmosphere carburizing, the oxygen potential of the vacuum heating chamber is fluctuated within a range of 1200-1300 mV by means of the controlled atmosphere carburizing system.

8. The method of carburizing in a controlled atmosphere through vacuum according to claim 6, wherein: The first predetermined pressure is 50-70 KPa, and the second predetermined pressure is 20-40 KPa.

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