Metal heat treatment nitriding process

Abstract

The invention relates to the technical field of metal hot working, and discloses a metal heat treatment nitriding process, and a management method of the metal heat treatment nitriding process comprises the following steps of S1, metal preparation, S2, nitriding treatment, S3, annealing, quenching and tempering treatment, S4, metal surface post-treatment and S5, metal detection and analysis. The machining precision and the surface quality can be effectively improved for curved burrs of metal materials, narrow pulse width and high pulse frequency are used in the machining process, due to the gap effect and the step change of pulse current, an electrolyte in a machining gap oscillates, pressure waves are generated, and the machining precision and the surface quality are improved. The stirring effect of the pressure waves improves the flowing condition of the electrolyte in the machining gap, accelerates updating of the electrolyte in the machining gap and eliminates nonuniformity of conductivity distribution of the electrolyte in the machining gap, so that the machining precision and the surface roughness are improved, and the subsequent nitriding fineness of metal is improved.

Description

Technical Field

[0001] The invention relates to the technical field of metal heat processing, in particular to a metal heat treatment nitriding process. Background Art

[0002] Nitriding treatment refers to a chemical heat treatment process that allows nitrogen atoms to penetrate into the surface of a workpiece in a certain medium at a certain temperature. Products treated with nitriding have excellent wear resistance, fatigue resistance, corrosion resistance and high temperature resistance. However, there are usually some problems with the existing metal heat treatment process. The metal is not pretreated and preheated before heating and nitriding, and errors are prone to occur during the heat treatment and nitriding of the metal. Therefore, "when the metal is heat treated and nitrided, the heating method of the metal, the control method of the metal nitriding, and the treatment method of the metal after nitriding will affect the effect of the metal heat treatment work", which is specifically manifested in the following aspects:

[0003] (1) The metal heating speed is slow; (2) The metal insulation time is short; (3) The metal cooling speed is fast; (4) The nitriding concentration is low; (5) The nitriding temperature is low; (6) The nitriding treatment is not stable enough; (7) The cleaning effect after metal nitriding is poor; (8) The impurity removal effect after metal nitriding is poor; (9) The control effect of metal nitriding is general; (10) It is inconvenient to detect and analyze the treated metal. Summary of the invention

[0004] The object of the present invention is to provide a metal heat treatment nitriding process to solve the problems proposed in the above background technology that the treatment method after metal nitriding will affect the effect of metal heat treatment work: (1) the metal heating speed is slow; (2) the metal insulation time is short; (3) the metal cooling speed is fast; (4) the nitriding concentration is low; (5) the nitriding temperature is low; (6) the nitriding treatment is not stable enough; (7) the cleaning effect after metal nitriding is poor; (8) the impurity removal effect after metal nitriding is poor; (9) the control effect of metal nitriding is general; (10) it is inconvenient to detect and analyze the treated metal.

[0005] To achieve the above object, the present invention provides the following technical solution: a metal heat treatment nitriding process, the management method of which comprises the following steps:

[0006] S1. Prepare the metal

[0007] The metal material needs to be cut into shapes of different sizes, and then the metal needs to be cleaned and prepared;

[0008] ① Grinding

[0009] The material needs to be ground to remove oxides and rust on the surface of the material. The grinding machines for nitride metals are divided into manual grinders and automatic grinders. According to the actual processing needs, different sizes of grinding machines are rotated according to the metal materials of different sizes. Before grinding the metal, the metal must be cleaned to remove dirt and grease impurities. During grinding, the pressure of the grinding head should be gradually increased, and the grinding depth and speed should be maintained at 60%-80%. During the grinding process, the cleaning liquid should be replaced and the grinding head should be cleaned when the cleaning liquid is ≤30 to prepare for the next step of processing;

[0010] ②Remove burrs

[0011] After grinding, some burrs and sharp corners will be left on the surface of the material, which need to be deburred. When deburring metal, electrochemical deburring with narrow pulse width and high pulse frequency is used;

[0012] ③ Deoiling

[0013] There will be a layer of grease on the surface of the material, which needs to be thoroughly removed before nitriding. The principle of metal degreasing is to use solvents, chemical reagents or physical friction to remove oil and impurities on the metal surface. The degreasing agent uses organic solvents and weak alkaline agents. There are many types, which are determined according to the metal material, oil type and degreasing requirements;

[0014] ④ Rough cleaning

[0015] Rough cleaning is the first step in surface cleaning of materials. The ground, deburred and deoiled metal is placed in a water tank for preliminary cleaning.

[0016] ⑤ Fine cleaning

[0017] Fine cleaning is the second step of surface cleaning of materials. First, put the metal into a cleaning tank containing nitric acid for 2-5 minutes. Then put the metal into a mixture of hydrofluoric acid, nitric acid and water for 10-20 seconds. Then put the metal into a rinse tank and rinse it repeatedly with clean water for 3-5 minutes. Finally, put the metal into a pretreatment tank containing an active agent for 5-15 minutes.

[0018] S2. Nitriding treatment

[0019] The metal material after pre-treatment enters the nitriding treatment stage. The main principle is to allow nitrogen atoms to penetrate into the metal lattice through heating and nitrogen injection in a specific atmosphere to change the physical properties of the metal surface.

[0020] ① Exhaust air from nitriding furnace

[0021] The metal parts to be treated are placed in the nitriding furnace, and the furnace cover is sealed before heating. However, the air in the furnace must be removed before heating to 150°C. The gases used are ammonia and nitrogen. The hard nitriding working temperature is between 480°C and 550°C, and the common temperature is between 490°C and 530°C. The calculation formula is: FH3=F+3 / 2H2, where F is active nitrogen, which plays a nitriding role, and FH3, N2, and H2 are the atmosphere composition in the furnace;

[0022] ②Decomposition rate of ammonia

[0023] Nitriding is carried out by contacting nitriding and other alloying elements with primary nitrogen. The generation of primary nitrogen is that when ammonia contacts the heated steel, the steel itself becomes a catalyst and promotes the decomposition of ammonia. Nitriding adopts a decomposition rate of 15-30% and is maintained for at least 4-10 hours according to the required thickness of nitriding. The treatment temperature is maintained at 520°C. The calculation formula of nitrogen potential is KN=(1-4 / 3p(H2)) / p(H2)^1.5. Soft nitriding: KN=(a-2 / 3(1+a)p(H2)) / p(H2)^1.5, where a is the proportion of ammonia in the total gas, p(H2) is the hydrogen partial pressure, and KN is the nitrogen potential value.

[0024] ③Cooling

[0025] After nitriding is completed, turn off the heating power supply to reduce the furnace temperature by about 50℃, then double the flow rate of ammonia and start to open the heat exchanger. Pay attention to observe whether there are bubbles overflowing from the glass bottle connected to the exhaust pipe to confirm that the gas pressure in the furnace is normal. After waiting for the ammonia introduced into the furnace to stabilize, you can reduce the flow rate of ammonia until the gas pressure in the furnace is normal. When the furnace temperature drops below 150℃, use the method of exhausting the gas in the furnace described above, introduce air or nitrogen, and then open the furnace cover;

[0026] S3, annealing, quenching, tempering

[0027] After nitriding treatment, the hardness and toughness of metal materials are improved, but there are still some stress and pores, which need further treatment. Annealing, quenching and tempering are necessary supplementary processes after nitriding treatment.

[0028] ① Annealing

[0029] Heat the metal material to 20-40 degrees, keep it warm for 30 minutes, and then slowly cool it with the furnace (or bury it in sand or lime to cool it) to below 500 degrees and cool it in the air. The calculation formula for nitriding annealing is In(P1 / P2)=AHR*(1 / T2-1 / T1) where P1 and P2 are the phase change pressures of the material at two different temperatures, H is the enthalpy change of the phase change, T1 and T2 are the phase change temperatures of the material at two different temperatures, and R is the ideal gas constant;

[0030] ② Sudden fire

[0031] The metal material is heated to 800℃-950℃, and then cooled rapidly by cooling to produce stress and pixels on the surface of the material. When the metal is quenched, brine, water and oil are used as cooling media;

[0032] ③Tempering

[0033] The quenched metal material is heated to 50°C-100°C and maintained for 30 minutes, and then cooled by natural air cooling;

[0034] S4, Surface post-treatment metal

[0035] After the nitriding process, the metal material needs to be processed. The surface post-treatment methods include polishing, electroplating, and passivation.

[0036] ①Polishing

[0037] Polishing the surface of metal materials by mechanical grinding or electrochemical polishing;

[0038] ②Electroplating

[0039] First, degreasing, pickling and cleaning are used, and then a layer of catalyst is coated on the surface of the metal material. Then, the metal material is immersed in an electrolyte, and the required metal layer is plated through electrolysis, and then it goes through cleaning and drying steps;

[0040] ③ Passivation

[0041] The polished and electroplated metal material is immersed in a solution of 0.25%-1% nitrite, 0.25%-1% nitrate, and 1%-4% chloride for 30 minutes to form a chromate passivation film on the metal surface;

[0042] S5. Metal Detection Analysis

[0043] The generated nitride film is characterized and analyzed using X-ray diffractometers and scanning electron microscopes, and then artificial intelligence technology is applied to the metal nitridation process, such as building a neural network model to predict and optimize the process, or using machine learning algorithms to predict and solve problems that arise.

[0044] 2. A metal heat treatment nitriding process according to claim 1, characterized in that: when the nitriding furnace exhausts air, the furnace cover is sealed after the treated parts are installed, and anhydrous ammonia is started to flow at a flow rate of 80%.

[0045] 3. A metal heat treatment nitriding process according to claim 1, characterized in that: when the nitriding furnace discharges air, the temperature of the nitriding furnace is automatically controlled and set to 150°C and heating begins, and the furnace temperature is ≤150°C.

[0046] 4. A metal heat treatment nitriding process according to claim 1, characterized in that: when the air is exhausted from the nitriding furnace, the air in the furnace is exhausted to less than 10%, and when the exhausted gas contains more than 90% nitrogen, the furnace temperature is then increased to the nitriding temperature.

[0047] 5. A metal heat treatment nitriding process according to claim 1, characterized in that the ratio of the passivated metal material is 0.25% nitrite, 0.25% nitrate, and 0.2% chloride.

[0048] 6. A metal heat treatment nitriding process according to claim 1, characterized in that when the metal is quenched, the concentration of the salt water is 10%.

[0049] 7. A metal heat treatment nitriding process according to claim 1, characterized in that the metal material is immersed in an electrolyte, and the concentration of the electroplating electrolyte is 200-250g / L.

[0050] 8. A metal heat treatment nitriding process according to claim 1, characterized in that the metal material is immersed in an electrolyte, and the concentration of the electrolyte for rapid electroplating is 250-300g / L.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] The present invention uses a pulse power supply instead of a DC power supply for electrochemical deburring, and can effectively improve the processing accuracy and surface quality of metal materials for deburring. A narrow pulse width and a high pulse frequency are used during processing. Due to the gap effect and the step change of the pulse current, the electrolyte in the processing gap oscillates and generates a pressure wave. The stirring effect of the pressure wave improves the flow condition of the electrolyte in the processing gap, accelerates the renewal of the electrolyte in the processing gap, and eliminates the uneven distribution of the electrolyte conductivity in the processing gap, thereby improving the processing accuracy and surface roughness, thereby improving the fineness of the subsequent nitriding of the metal.

[0053] The present invention characterizes and analyzes the generated nitride film through an X-ray diffractometer and a scanning electron microscope to ensure that the expected effect is achieved, and then uses artificial intelligence technology to facilitate a better understanding and detection of the metal heat treatment nitriding process, thereby improving the intelligence of the metal heat treatment nitriding, and can use the network model to facilitate subsequent improvements to the process. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 The metal heat treatment nitriding process flow chart of the present invention;

[0055] Figure 2 This is a schematic diagram of the placement ratio information of the passivation material of the metal material of the present invention. DETAILED DESCRIPTION

[0056] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0057] Embodiment 1:

[0058] Please refer to the figure, a metal heat treatment nitriding process, and its management method includes the following steps:

[0059] S1. Prepare the metal

[0060] The metal material needs to be cut into shapes of different sizes, and then the metal is cleaned and prepared, which greatly improves the quality of the metal and the nitriding effect

[0061] ① Grinding

[0062] The material needs to be ground to remove oxides and rust on the surface of the material. The grinding machines for nitride metals are divided into manual grinders and automatic grinders. Manual grinders are simple to operate and suitable for small batch processing, while automatic grinders complete large batch processing and improve production efficiency. According to the actual processing needs, different sizes of grinding machines are rotated according to different sizes of metal materials. Before grinding the metal, the metal must be cleaned to remove dirt and grease impurities. During grinding, the pressure of the grinding head should be gradually increased to maintain a grinding depth and speed of 60%-80%. During the grinding process, the cleaning liquid should be replaced and the grinding head should be cleaned when the cleaning liquid is ≤30 to maintain the cleanliness of the grinding liquid and prepare for the next step of processing;

[0063] ②Remove burrs

[0064] After grinding, some burrs and sharp corners will be left on the surface of the material, and these parts need to be deburred. When deburring metal, manual deburring is suitable for products with few burrs, simple product structure, and low technical requirements for operators. Electrochemical deburring with narrow pulse width and high pulse frequency. Theoretical research and processing practice of pulse power supply show that using pulse power supply instead of DC power supply for deburring can effectively improve processing accuracy and surface quality. Usually, narrow pulse width and high pulse frequency are used in processing. Due to the gap effect and the step change of pulse current, the electrolyte in the processing gap oscillates, generating pressure waves, which press The stirring action of the force wave improves the flow condition of the electrolyte in the machining gap, accelerates the renewal of the electrolyte in the machining gap, and eliminates the uneven distribution of the electrolyte conductivity in the machining gap, thereby improving the machining accuracy and surface roughness. Electrochemical deburring uses an electrode with a shape similar to the edge to be deburred. As the name suggests, it uses electricity and chemicals to remove burrs. Electric current and electrolyte are required for electrochemical deburring. Sodium chloride (salt) or sodium nitrate is used as the electrolyte to remove burrs without pressure. This method is fast and provides high precision in difficult areas to avoid excessive pores or cracks in subsequent nitriding treatments.

[0065] ③ Deoiling

[0066] There will be a layer of grease on the surface of the material, which needs to be thoroughly removed before nitriding treatment to ensure the stability and uniformity of the surface quality after nitriding. The principle of metal degreasing and degreasing is to use solvents, chemical reagents or physical friction to remove oil and impurities on the metal surface. There are many types of degreasing and degreasing agents using organic solvents and weak alkaline agents, which are determined according to the metal material, oil type and degreasing requirements;

[0067] ④ Rough cleaning

[0068] Rough cleaning is the first step in cleaning the surface of the material. The metal after grinding, deburring and degreasing is placed in a water tank for preliminary cleaning. The purpose is to remove impurities and dirt on the surface and prepare for the next step of fine cleaning.

[0069] ⑤ Fine cleaning

[0070] Fine cleaning is the second step of surface cleaning of materials. First, put the metal into a cleaning tank containing nitric acid for 2-5 minutes. Then put the metal into a mixture of hydrofluoric acid, nitric acid and water for 10-20 seconds. Then put the metal into a rinse tank and rinse it repeatedly with clean water for 3-5 minutes. Finally, put the metal into a pretreatment tank containing an active agent for 5-15 minutes. The purpose is to remove the dirt that was not removed in the rough cleaning and ensure that the surface of the material is completely dry.

[0071] S2. Nitriding treatment

[0072] The metal material that has undergone pretreatment enters the nitriding treatment stage. The main principle is to allow nitrogen atoms to penetrate into the metal lattice through heating and nitrogen injection in a specific atmosphere to change the physical properties of the metal surface. During the nitriding process, the temperature and time need to be controlled to ensure the hardness and uniformity of the material surface. At the same time, the pores and surface defects generated during the treatment process need to be monitored and adjusted to ensure the stability and reliability of the nitriding quality.

[0073] ① Exhaust air from nitriding furnace

[0074] The metal parts to be treated are placed in the nitriding furnace, and the furnace cover is sealed before heating. However, the air in the furnace must be exhausted before heating to 150°C. The main function of exhausting the air in the furnace is to prevent the explosive gas generated when ammonia decomposes and contacts with air, and to prevent the surface oxidation of the treated objects and brackets. The gases used are ammonia and nitrogen. The hard nitriding working temperature is between 480°C and 550°C, and the common temperature is between 490°C and 530°C. The calculation formula is: FH3=F+3 / 2H2, where F is active nitrogen, which plays a nitriding role, and FH3, N2, and H2 are the atmosphere composition in the furnace;

[0075] ②Decomposition rate of ammonia

[0076] Nitriding is carried out by contacting nitriding and other alloying elements with primary nitrogen. The generation of primary nitrogen is that when ammonia contacts the heated steel, the steel itself becomes a catalyst and promotes the decomposition of ammonia. Nitriding adopts a decomposition rate of 15-30% and is maintained for at least 4-10 hours according to the required thickness of nitriding. The treatment temperature is maintained at 520°C. The calculation formula of nitrogen potential is KN=(1-4 / 3p(H2)) / p(H2)^1.5. Soft nitriding: KN=(a-2 / 3(1+a)p(H2)) / p(H2)^1.5, where a is the proportion of ammonia in the total gas, p(H2) is the hydrogen partial pressure, and KN is the nitrogen potential value.

[0077] ③Cooling

[0078] After nitriding is completed, turn off the heating power supply to reduce the furnace temperature by about 50℃, then double the flow rate of ammonia and start to open the heat exchanger. Pay attention to observe whether there are bubbles overflowing from the glass bottle connected to the exhaust pipe to confirm that the gas pressure in the furnace is normal. After waiting for the ammonia introduced into the furnace to stabilize, you can reduce the flow rate of ammonia until the gas pressure in the furnace is normal. When the furnace temperature drops below 150℃, use the method of exhausting the gas in the furnace described above, introduce air or nitrogen, and then open the furnace cover;

[0079] S3, annealing, quenching, tempering

[0080] After nitriding treatment, the hardness and toughness of metal materials are improved, but there are still some stress and pores, which need further treatment. Annealing, quenching and tempering are necessary supplementary processes after nitriding treatment. Through the process of heating and cooling, the material can achieve the ideal hardness and durability.

[0081] ① Annealing

[0082] Heat the metal material to 20-40 degrees, keep it warm for 30 minutes, and then slowly cool it with the furnace (or bury it in sand or lime to cool it) to below 500 degrees and cool it in the air. The calculation formula for nitriding annealing is In(P1 / P2)=AHR*(1 / T2-1 / T1) where P1 and P2 are the phase change pressures of the material at two different temperatures, H is the enthalpy change of the phase change, T1 and T2 are the phase change temperatures of the material at two different temperatures, and R is the ideal gas constant;

[0083] ② Sudden fire

[0084] The metal material is heated to 800℃-950℃, and then cooled rapidly to produce stress and pixels on the surface of the material to achieve the purpose of quenching and hardening. When the metal is quenched, salt water, water and oil are used as cooling media. The metal material through quenching is easy to obtain high hardness and smooth surface, and it is not easy to produce soft spots that cannot be hardened, but it is easy to cause serious deformation of the workpiece, or even cracking;

[0085] ③Tempering

[0086] The material after quenching is too hard and brittle and needs to be tempered. The purpose of this process is to return the material to a certain hardness and toughness so that it has better physical properties. The quenched metal material is heated to 50℃-100℃ and kept for 30 minutes, and then cooled by natural air cooling;

[0087] S4, Surface post-treatment metal

[0088] After the nitriding process, the metal material needs to be treated in order to enhance the surface hardness of the nitrided layer, improve the surface finish, reduce the surface friction coefficient and increase the surface lubricity. The surface post-treatment methods include polishing, electroplating and passivation.

[0089] ①Polishing

[0090] Polishing the surface of metal materials by mechanical grinding or electrochemical polishing to improve the surface flatness, smoothness and surface hardness of the materials;

[0091] ②Electroplating

[0092] First, degreasing, pickling and cleaning are used to remove impurities and oxides on the surface of the metal material and improve the adhesion of the electroplating. Then a layer of catalyst is coated on the surface of the metal material to improve the conductivity of the coating. Then the metal material is immersed in an electrolyte and plated with the required metal layer through electrolysis. Then, cleaning and drying steps are performed to remove the electroplating solution residue and moisture to ensure the stability of the metal material coating.

[0093] ③ Passivation

[0094] The polished and electroplated metal material is immersed in a solution of 0.25%-1% nitrite, 0.25%-1% nitrate, and 1%-4% chloride for 30 minutes to form a chromate passivation film on the metal surface;

[0095] S5. Metal Detection Analysis

[0096] We use X-ray diffractometers and scanning electron microscopes to characterize and analyze the generated nitride films to ensure that the expected results are achieved. We then apply artificial intelligence technology to the metal nitridation process, such as building a neural network model to predict and optimize the process, or using machine learning algorithms to predict and solve problems that arise. This way, we can better understand the process and monitor and improve the process in real time during production.

[0097] In this embodiment: when the nitriding furnace is exhausting air, the furnace cover is sealed after the treated parts are installed, and anhydrous ammonia gas is started to flow, and its flow rate is 80%:

[0098] In this embodiment: when the nitriding furnace exhausts air, the temperature of the nitriding furnace is automatically controlled and set to 150°C and heating begins, and the furnace temperature is ≤150°C:

[0099] In this embodiment: when the air is exhausted from the nitriding furnace, the air in the furnace is exhausted to less than 10%, and when the exhausted gas contains more than 90% nitrogen, the furnace temperature is raised to the nitriding temperature;

[0100] In this embodiment: the ratio of the passivated metal material is 0.25% nitrite, 0.25% nitrate, and 0.2% chloride;

[0101] In this embodiment: when the metal is quenched, the concentration of the salt water is 10%;

[0102] In this embodiment: the metal material is immersed in an electrolyte, and the concentration of the electroplating electrolyte is 200-250g / L;

[0103] In this embodiment: the metal material is immersed in the electrolyte, and the concentration of the electrolyte for rapid electroplating is 250-300g / L

[0104] Embodiment 2:

[0105] As shown in the figure, different from the first embodiment, the management method of a metal heat treatment nitriding process in this embodiment includes the following steps:

[0106] S1. Evacuate the furnace tank

[0107] The workpiece or mold is pre-evacuated to a low vacuum of <100MPa.

[0108] S2. Uniformly heat to 520-570℃ in a circulating nitrogen atmosphere

[0109] Fill with pure nitrogen (after removing the gas that affects nitriding) and heat evenly to 520-570℃ in a circulating nitrogen atmosphere.

[0110] S3. Fill with oxygen under nitrogen atmosphere.

[0111] Fill with oxygen to pre-form a uniform active oxide film on the metal surface;

[0112] In the first stage of nitriding, vacuum pulse charging and exhausting nitriding is carried out with an ammonia-nitrogen ratio of 1:1;

[0113] In the second stage of nitriding, vacuum pulse charging and exhausting nitriding is carried out with an ammonia-nitrogen ratio of 1:3;

[0114] After the nitriding process is completed, the vacuum is reduced to <100MPa, and forced cooling is carried out in a nitrogen atmosphere with a cooling rate of ≥10℃ / min

[0115] S4. Cool to below 100°C and take out of the furnace.

[0116] In summary: compared with Example 2, in this Example 1, a pulse power supply is used instead of a DC power supply for electrochemical deburring, which can effectively improve the processing accuracy and surface quality for deburring metal materials, thereby improving the processing accuracy and surface roughness, thereby improving the fineness of subsequent nitriding of the metal, and characterizing and analyzing the generated nitride film by means of an X-ray diffractometer and a scanning electron microscope to ensure that the expected effect is achieved, and then artificial intelligence technology is used to facilitate a better understanding and detection of the metal heat treatment nitriding process, thereby improving the intelligence of the metal heat treatment nitriding, and the network model can be used to facilitate subsequent improvements to the process.

[0117] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0118] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A metal heat treatment nitriding process, characterized in that: The management method includes the following steps: S1. Prepare the metal The metal material needs to be cut into shapes of different sizes, and then the metal needs to be cleaned and prepared; ① Grinding The material needs to be ground to remove oxides and rust on the surface of the material. The grinding machines for nitride metals are divided into manual grinders and automatic grinders. According to the actual processing needs, different sizes of grinding machines are rotated according to the metal materials of different sizes. Before grinding the metal, the metal must be cleaned to remove dirt and grease impurities. During grinding, the pressure of the grinding head should be gradually increased, and the grinding depth and speed should be maintained at 60%-80%. During the grinding process, the cleaning liquid should be replaced and the grinding head should be cleaned when the cleaning liquid is ≤30 to prepare for the next step of processing; ②Remove burrs After grinding, some burrs and sharp corners will be left on the surface of the material, which need to be deburred. When deburring metal, electrochemical deburring with narrow pulse width and high pulse frequency is used; ③ Deoiling There will be a layer of grease on the surface of the material, which needs to be thoroughly removed before nitriding. The principle of metal degreasing is to use solvents, chemical reagents or physical friction to remove oil and impurities on the metal surface. The degreasing agent uses organic solvents and weak alkaline agents. There are many types, which are determined according to the metal material, oil type and degreasing requirements; ④ Rough cleaning Rough cleaning is the first step in surface cleaning of materials. The ground, deburred and deoiled metal is placed in a water tank for preliminary cleaning. ⑤ Fine cleaning Fine cleaning is the second step of surface cleaning of materials. First, put the metal into a cleaning tank containing nitric acid for 2-5 minutes. Then put the metal into a mixture of hydrofluoric acid, nitric acid and water for 10-20 seconds. Then put the metal into a rinse tank and rinse it repeatedly with clean water for 3-5 minutes. Finally, put the metal into a pretreatment tank containing an active agent for 5-15 minutes. S2. Nitriding treatment The metal material after pre-treatment enters the nitriding treatment stage. The main principle is to allow nitrogen atoms to penetrate into the metal lattice through heating and nitrogen injection in a specific atmosphere to change the physical properties of the metal surface. ① Exhaust air from nitriding furnace The metal parts to be treated are placed in the nitriding furnace, and the furnace cover is sealed before heating. However, the air in the furnace must be removed before heating to 150°C. The gases used are ammonia and nitrogen. The hard nitriding working temperature is between 480°C and 550°C, and the common temperature is between 490°C and 530°C. The calculation formula is: FH3=F+3 / 2H2, where F is active nitrogen, which plays a nitriding role, and FH3, N2, and H2 are the atmosphere composition in the furnace; ②Decomposition rate of ammonia Nitriding is carried out by contacting nitriding and other alloying elements with primary nitrogen. The generation of primary nitrogen is that when ammonia contacts the heated steel, the steel itself becomes a catalyst and promotes the decomposition of ammonia. Nitriding adopts a decomposition rate of 15-30% and is maintained for at least 4-10 hours according to the required thickness of nitriding. The treatment temperature is maintained at 520°C. The calculation formula of nitrogen potential is KN=(1-4 / 3p(H2)) / p(H2)^1.

5. Soft nitriding: KN=(a-2 / 3(1+a)p(H2)) / p(H2)^1.5, where a is the proportion of ammonia in the total gas, p(H2) is the hydrogen partial pressure, and KN is the nitrogen potential value. ③Cooling After nitriding is completed, turn off the heating power supply to reduce the furnace temperature by about 50℃, then double the flow rate of ammonia and start to open the heat exchanger. Pay attention to observe whether there are bubbles overflowing from the glass bottle connected to the exhaust pipe to confirm that the gas pressure in the furnace is normal. After waiting for the ammonia introduced into the furnace to stabilize, you can reduce the flow rate of ammonia until the gas pressure in the furnace is normal. When the furnace temperature drops below 150℃, use the method of exhausting the gas in the furnace described above, introduce air or nitrogen, and then open the furnace cover; S3, annealing, quenching, tempering After nitriding treatment, the hardness and toughness of metal materials are improved, but there are still some stresses and pores, which require further treatment. Annealing, quenching and tempering are necessary supplementary processes after nitriding treatment; ① Annealing Heat the metal material to 20-40 degrees, keep it warm for 30 minutes, and then slowly cool it with the furnace (or bury it in sand or lime to cool it) to below 500 degrees and cool it in the air. The calculation formula for nitriding annealing is In(P1 / P2)=AHR*(1 / T2-1 / T1) where P1 and P2 are the phase change pressures of the material at two different temperatures, H is the enthalpy change of the phase change, T1 and T2 are the phase change temperatures of the material at two different temperatures, and R is the ideal gas constant; ② Sudden fire The metal material is heated to 800℃-950℃, and then cooled rapidly by cooling to produce stress and pixels on the surface of the material. When the metal is quenched, brine, water and oil are used as cooling media; ③Tempering The quenched metal material is heated to 50°C-100°C and maintained for 30 minutes, and then cooled by natural air cooling; S4, Surface post-treatment metal After the nitriding process, the metal material needs to be processed. The surface post-treatment methods include polishing, electroplating, and passivation. ①Polishing Polishing the surface of metal materials by mechanical grinding or electrochemical polishing; ②Electroplating First, degreasing, pickling and cleaning are used, and then a layer of catalyst is coated on the surface of the metal material. Then, the metal material is immersed in an electrolyte, and the required metal layer is plated through electrolysis, and then it goes through cleaning and drying steps; ③ Passivation The polished and electroplated metal material is immersed in a solution of 0.25%-1% nitrite, 0.25%-1% nitrate, and 1%-4% chloride for 30 minutes to form a chromate passivation film on the metal surface; S5. Metal detection analysis The generated nitride film is characterized and analyzed using X-ray diffractometers and scanning electron microscopes, and then artificial intelligence technology is applied to the metal nitridation process, such as building a neural network model to predict and optimize the process, or using machine learning algorithms to predict and solve possible problems.

2. A metal heat treatment nitriding process according to claim 1, characterized in that: When the nitriding furnace is exhausting air, the furnace cover is sealed after the treated parts are installed, and anhydrous ammonia gas is started to flow in at a flow rate of 80%.

3. A metal heat treatment nitriding process according to claim 1, characterized in that: When the nitriding furnace exhausts air, the temperature of the nitriding furnace is automatically controlled and set to 150° C. and heating begins, and the furnace temperature is ≤150° C.

4. A metal heat treatment nitriding process according to claim 1, characterized in that: When exhausting air from the nitriding furnace, the air in the furnace is exhausted to less than 10%. When the exhausted gas contains more than 90% nitrogen, the furnace temperature is raised to the nitriding temperature.

5. A metal heat treatment nitriding process according to claim 1, characterized in that: The passivated metal material ratio is 0.25% of nitrite, 0.25% of nitrate and 0.2% of chloride.

6. A metal heat treatment nitriding process according to claim 1, characterized in that: When the metal is quenched, the concentration of the brine is 10%.

7. A metal heat treatment nitriding process according to claim 1, characterized in that: The metal material is immersed in an electrolyte, and the concentration of the electroplating electrolyte is 200-250g / L.

8. A metal heat treatment nitriding process according to claim 1, characterized in that: The metal material is immersed in an electrolyte, and the concentration of the electrolyte for rapid electroplating is 250-300 g / L.

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