Implementation process for nitriding by replacing ammonia gas with nitrogen

Abstract

The invention discloses an implementation process for nitriding by replacing ammonia with nitrogen, and belongs to the technical field of mold surface treatment. Comprising the following steps that S3, after the nitriding heat preservation operation of the mold is completed, cooling is started, then gas introduced into the furnace is switched from ammonia gas to nitrogen gas, and after the temperature is reduced to a preset value, nitrogen gas introduction is stopped, and the mold is taken out. After nitriding heat preservation operation of the mold in the nitriding furnace is completed, the nitriding furnace is cooled, when the temperature is reduced to be lower than 400 DEG C, ammonia gas introduced into the furnace is switched into nitrogen gas, it can be ensured that original ammonia gas in the furnace is completely decomposed when the mold is discharged out of the furnace, and the nitrogen gas serves as inert gas, has the colorless and odorless characteristics and has high chemical stability, so that the mold is not prone to falling off. Nitrogen taken out when the mold is discharged from the furnace does not contain ammonia gas, and the purposes of protecting the environment and protecting the body health of personnel are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of mold surface treatment, and in particular relates to an implementation process of nitridation by replacing ammonia with nitrogen. Background Art

[0002] As the automotive industry develops towards lightweight, the demand for bright anodized aluminum profiles from OEMs continues to increase. The rapid rise of new energy vehicles has further promoted the application of special-shaped and complex structural aluminum profiles, and the proportion of these aluminum profiles used in car bodies is increasing. All-aluminum body designs have appeared on the market, and most of these complex aluminum profiles are manufactured through aluminum extrusion processes. Especially in body structural parts, the material composition is complex, which places extremely high demands on the load-bearing capacity and wear resistance of the extrusion die. Therefore, in order to extend the service life of the die, it is usually necessary to nitride the extrusion die.

[0003] Traditional nitriding mainly uses ammonia (NH3) as a nitriding agent. However, ammonia is a highly irritating gas that can cause serious harm to the human body if inhaled. Especially when the nitriding temperature is below 400°C, the decomposition efficiency of ammonia is reduced, resulting in more ammonia being emitted without complete reaction when leaving the furnace. Therefore, reducing the amount of ammonia used and improving its volatilization condition have become urgent issues to be solved. Summary of the invention

[0004] The present invention aims at the above problems existing in the prior art and proposes a process for implementing nitridation by replacing ammonia with nitrogen.

[0005] The present invention can be achieved through the following technical solutions:

[0006] A process for implementing nitrogenization by replacing ammonia with nitrogen comprises the following steps:

[0007] S3. After the mold is nitrided and heat-insulated, the temperature is lowered and the gas introduced into the furnace is switched from ammonia to nitrogen until the temperature drops to a preset value. Then, the introduction of nitrogen is stopped and the mold is removed.

[0008] As a further improvement of the present invention, before step S3, the following steps are also included:

[0009] S1. Install the mold to be treated in a nitriding furnace, start the nitriding furnace and introduce ammonia gas. The ammonia gas decomposes to produce active nitrogen atoms and hydrogen. The nitrogen atoms are absorbed by the surface of the mold to form a nitriding layer.

[0010] As a further improvement of the present invention, between step S1 and step S3, the following steps are also included:

[0011] S2, entering the nitriding insulation stage, controlling the decomposition temperature and inflow flow rate of ammonia to ensure the nitriding effect.

[0012] As a further improvement of the present invention, in step S1, the heating temperature range of the nitriding furnace is 380-550°C.

[0013] As a further improvement of the present invention, in step S2, the pressure difference in the nitriding furnace is controlled between 80 mm and 100 mm.

[0014] As a further improvement of the present invention, in step S2, the decomposition temperature of ammonia is controlled to be above 400°C.

[0015] As a further improvement of the present invention, in step S3, when the temperature in the nitriding furnace drops below 400°C, the ammonia gas is turned off and nitrogen gas is introduced at the same time, and the introduction of nitrogen gas continues until the mold can be taken out of the furnace.

[0016] As a further improvement of the present invention, a nitrogen pipeline is provided at the air inlet of the nitriding furnace, and the nitrogen pipeline is equipped with a pressure reducing valve to adjust the nitrogen pressure.

[0017] As a further improvement of the present invention, in step S1, the interior of the nitriding furnace is vacuumed before the temperature of the furnace is raised.

[0018] As a further improvement of the present invention, before step S1, the mold surface is pretreated to remove surface contaminants to improve the nitriding effect.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. After the mold has completed the nitriding and heat preservation operation in the nitriding furnace, the nitriding furnace is cooled down. When the temperature drops to below 400°C, the ammonia gas introduced into the furnace is switched to nitrogen gas, thereby ensuring that the original ammonia gas in the furnace is completely decomposed when the mold is taken out of the furnace. Nitrogen, as an inert gas, is colorless and odorless, and has a high degree of chemical stability. Therefore, the nitrogen gas taken out of the mold when it is taken out of the furnace does not contain ammonia components, which plays a role in protecting the environment and protecting the health of personnel;

[0021] 2. During the nitriding process of the mold, the active nitrogen atoms generated by the decomposition of ammonia form a nitriding layer on the mold surface, and hydrogen provides a reducing atmosphere for the nitriding process, which helps prevent the oxidation of the metal surface at high temperatures and ensures the quality and uniformity of the nitriding layer;

[0022] 3. During the nitriding process of the mold, the hydrogen produced by the decomposition of ammonia can also assist the nitriding process, allowing the active nitrogen atoms to better penetrate into the lattice of the metal surface and react with metal elements (such as iron) to form hard and wear-resistant nitrides (such as Fe3N, Fe4N, etc.). That is, the presence of hydrogen helps the diffusion of nitrogen atoms, thereby further improving the formation efficiency and quality of the nitriding layer, ensuring that a high-quality nitriding layer can be formed on the mold surface, so that the nitrided mold has higher hardness and wear resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a flow chart of the implementation process of nitrogen replacement of ammonia nitridation of the present invention. DETAILED DESCRIPTION

[0024] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical method of the present invention, but the present invention is not limited to these embodiments.

[0025] like Figure 1 As shown, the present invention provides a process for implementing nitrogen replacement of ammonia nitridation, comprising the following steps:

[0026] S3. After the mold has completed the nitriding and heat preservation operation in the nitriding furnace, the temperature is lowered, and the gas introduced into the nitriding furnace is switched from ammonia to nitrogen. After the temperature drops to a preset value, the introduction of nitrogen is stopped and the mold is taken out.

[0027] It should be noted that after the mold has completed nitriding and heat preservation, its surface already has a nitriding layer, and before the mold is taken out of the furnace, the nitriding furnace needs to be cooled down first. However, when the ammonia is below 400°C, its decomposition rate will decrease. Therefore, when the mold is taken out of the furnace, the undecomposed ammonia in the furnace will be carried out. Ammonia is a highly irritating gas and inhalation can cause great harm to the human body.

[0028] In this regard, in this embodiment, after the mold completes the nitriding and heat preservation operation in the nitriding furnace, the nitriding furnace is cooled. When the temperature drops to below 400°C, the ammonia introduced into the furnace is switched to nitrogen, which ensures that the original ammonia in the furnace is completely decomposed when the mold is taken out of the furnace. Nitrogen, as an inert gas, is colorless and odorless and has a high chemical stability. Therefore, the nitrogen taken out of the mold when it is taken out of the furnace does not contain ammonia components, thereby protecting the environment and protecting the health of personnel.

[0029] Preferably, before step S3, the method further comprises the following steps:

[0030] S1. Install the mold to be treated in a nitriding furnace, start the nitriding furnace and introduce ammonia gas. The ammonia gas decomposes to produce active nitrogen atoms and hydrogen (2NH3→2[N]+3H2). The nitrogen atoms are absorbed by the mold surface to form a nitriding layer.

[0031] That is, step S1 is the nitridation process of the mold, and the active nitrogen atoms generated by the decomposition of ammonia form a nitridation layer on the mold surface, and hydrogen provides a reducing atmosphere for the nitridation process, which helps to prevent the oxidation of the metal surface at high temperature. The reducing atmosphere means that hydrogen can react with the oxide on the metal surface and reduce it back to the metal state, thereby protecting the metal surface from oxidation damage and ensuring the quality and uniformity of the nitridation layer;

[0032] In addition, hydrogen can also assist the nitriding process, allowing the active nitrogen atoms produced by the decomposition of ammonia to better penetrate into the lattice of the metal surface and react with metal elements (such as iron) to form hard and wear-resistant nitrides (such as Fe3N, Fe4N, etc.);

[0033] That is, the presence of hydrogen helps the diffusion of nitrogen atoms, thereby further improving the formation efficiency and quality of the nitride layer, ensuring that a high-quality nitride layer can be formed on the mold surface, and making the nitrided mold have higher hardness and wear resistance.

[0034] Preferably, between step S1 and step S3, the following steps are also included:

[0035] S2, entering the nitriding and heat preservation stage, controlling the decomposition temperature and the flow rate of ammonia to ensure the nitriding effect;

[0036] Specifically, in step S2, the decomposition temperature of ammonia is controlled to be at least 400°C to ensure the decomposition efficiency of ammonia, and the flow rate of ammonia is to ensure the pressure in the nitriding furnace. In actual operation, a U-shaped pressure gauge can be used to measure the pressure in the furnace, and ammonia is introduced to keep the pressure difference in the furnace at 80mm-100mm.

[0037] Preferably, in step S1, the heating temperature of the nitriding furnace is in the range of 380-550°C, wherein when the nitriding furnace is heated to above 400°C, ammonia begins to decompose and forms a nitrided layer on the surface of the mold.

[0038] Preferably, in step S3, when the temperature in the nitriding furnace drops below 400°C, the ammonia is turned off and nitrogen is introduced at the same time. The introduction of nitrogen continues until the mold is taken out of the furnace, effectively reducing the use of ammonia and preventing excess ammonia from being discharged into the environment when the mold is taken out of the furnace.

[0039] Preferably, a nitrogen pipeline is provided at the air inlet of the nitriding furnace, and the nitrogen pipeline is equipped with a pressure reducing valve to adjust the nitrogen pressure to ensure that the nitrogen flows into the furnace at a suitable pressure, thereby stabilizing the flow rate of the nitrogen and ensuring a stable and reliable gas supply during the nitriding process.

[0040] Preferably, before step S1, the mold surface is pretreated to remove surface contaminants to improve the nitriding effect.

[0041] Preferably, in step S1, before the nitriding furnace is heated up, the nitriding furnace is first vacuumed to effectively remove the air in the nitriding furnace, reduce the oxygen and other impurity gases in the air, create a purer environment for the subsequent nitriding process, and avoid oxidation of the mold surface due to contact with oxygen at high temperature, thereby improving the quality of the nitriding layer.

[0042] The technical means disclosed in the scheme of the present invention are not limited to the technical means disclosed in the above technical means, but also include technical schemes composed of any combination of the above technical features. The above is a specific implementation of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also regarded as the protection scope of the present invention.

[0043] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0044] In addition, in the present invention, descriptions such as "first", "second", "one", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0045] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0046] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

Claims

1. A process for implementing nitrogenization by replacing ammonia with nitrogen, characterized in that: The following steps are involved: S3. After the mold is nitrided and heat-insulated, the temperature is lowered. The gas introduced into the nitriding furnace is switched from ammonia to nitrogen until the temperature drops to a preset value. Then, the nitrogen is stopped and the mold is removed.

2. The implementation process of nitrogen replacement of ammonia nitridation according to claim 1, characterized in that: Before step S3, the method further includes the following steps: S1. Install the mold to be treated in a nitriding furnace, start the nitriding furnace and introduce ammonia gas. The ammonia gas decomposes to produce active nitrogen atoms and hydrogen. The nitrogen atoms are absorbed by the surface of the mold to form a nitriding layer.

3. The implementation process of nitrogen replacement of ammonia nitridation according to claim 2, characterized in that: Between step S1 and step S3, the following steps are also included: S2, entering the nitriding insulation stage, controlling the decomposition temperature and inflow flow rate of ammonia to ensure the nitriding effect.

4. The implementation process of nitrogen replacement of ammonia nitridation according to claim 1, characterized in that: In step S1, the heating temperature of the nitriding furnace ranges from 380°C to 550°C.

5. The implementation process of nitrogen replacement of ammonia nitridation according to claim 3, characterized in that: In step S2, the pressure difference in the nitriding furnace is controlled between 80 mm and 100 mm.

6. The implementation process of nitrogen replacement of ammonia nitridation according to claim 3, characterized in that: In step S2, the decomposition temperature of ammonia is controlled to be above 400°C.

7. The process for implementing nitrogen nitridation by replacing ammonia with nitrogen according to claim 1, characterized in that: In step S3, when the temperature in the nitriding furnace drops below 400°C, the ammonia gas is turned off and nitrogen gas is introduced at the same time. The introduction of nitrogen gas continues until the mold can be taken out of the furnace.

8. The process for implementing nitrogen nitridation by replacing ammonia with nitrogen according to claim 1, characterized in that: A nitrogen pipeline is provided at the air inlet of the nitriding furnace, and the nitrogen pipeline is equipped with a pressure reducing valve to adjust the nitrogen pressure.

9. The process for implementing nitrogen nitridation by replacing ammonia with nitrogen according to claim 1, characterized in that: In step S1, the interior of the nitriding furnace is evacuated before the temperature is raised.

10. The process for implementing nitridation by replacing ammonia with nitrogen according to claim 1, characterized in that: Before step S1, the mold surface is pretreated to remove surface contaminants to improve the nitriding effect.

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