Process method for controlling tufftriding hardness layer depth

Abstract

The technical method for controlling the tufftriding hardness layer depth is provided, the calculated basic atmosphere content serves as an adjustment basis, tufftriding is conducted on a workpiece according to the basic atmosphere content and optimized ammonia and ethyl alcohol parameters, the mutual restriction relation between the ammonia flow and the ethyl alcohol dripping amount and the nitrided white bright layer and the surface hardness is determined, and the tufftriding hardness layer depth is controlled. Under the condition that the actual flow of the ammonia gas is consistent, the actual dripping number of the ethanol is in direct proportion to the thickness of the diffusion layer; under the condition that the actual dripping number of the ethanol is consistent, the actual flow of the ammonia gas is in direct proportion to the white bright layer and the surface hardness of the tufftriding, so that the control on the hardness layer depth of the tufftriding is realized; the method has the advantages of simple operation, accurate control of the use amount of ethanol and ammonia gas, guarantee of the technical indexes of the product, optimization of the resources in the tufftriding process, shortening of the research and development period of the process debugging, stabilization of the product quality, broadening of the processing thought, and mastering of the key influence factors in the tufftriding process debugging.

Description

Technical Field

[0001] This invention belongs to the field of diesel engine technology, specifically relating to a process method for controlling the depth of the soft nitriding hardness layer. Background Technology

[0002] Soft nitriding, also known as salt bath nitriding or gas nitrocarburizing, is a low-temperature chemical heat treatment process. It involves primarily nitriding and secondarily carburizing to infiltrate nitrogen (N) and carbon (C) atoms into the surface of a steel workpiece, forming a dense nitrocarburite layer (bright white layer) and a diffusion layer. This significantly improves the surface properties of the parts—the bright white layer possesses high hardness, excellent wear resistance, and corrosion resistance, while the nitrogen atoms in the diffusion layer are dissolved in the matrix, enhancing the fatigue strength of the matrix. The temperature of the soft nitriding process is below the A1 line, typically between 530℃ and 570℃, within the stable range of the α-Fe phase. For medium-carbon alloy steel, the soft nitriding temperature needs to be maintained at 570℃. The main atmosphere is ethanol and ammonia. After treatment, the surface of the steel workpiece mainly forms a strengthening ε phase (Fe2-3N) and a diffusion layer (α-Fe + nitrides).

[0003] In current production, the soft nitriding process control revolves around the atmosphere ratio of ethanol dripping rate to ammonia flow rate. This ratio directly affects the depth of the bright and diffused layers, and the surface hardness of the steel parts is primarily determined by these layers. However, existing process control methods are inconsistent and fail to grasp the influence of ammonia flow rate and ethanol dripping rate on the bright and transition layers, making it impossible to achieve large-scale control over these layers. Therefore, improvements are necessary. Summary of the Invention

[0004] The technical problem solved by this invention is to provide a process method for controlling the depth of the soft nitriding hardness layer. Using a calculated base atmosphere content as the adjustment basis, the workpiece is soft nitrided according to optimized ammonia and ethanol parameters based on the base atmosphere content. The method determines the mutual constraint relationship between ammonia flow rate and ethanol dripping amount on the white gloss layer and surface hardness of the nitrided material. It is found that when the actual ammonia flow rate is consistent, the actual ethanol dripping amount is directly proportional to the diffusion layer thickness; and when the actual ethanol dripping amount is consistent, the actual ammonia flow rate is directly proportional to the white gloss layer and surface hardness of the soft nitriding, thus achieving control over the depth of the soft nitriding hardness layer. This method is easy to operate, allows for precise control of the ethanol and ammonia usage, ensures product technical specifications, optimizes resources in the soft nitriding process, shortens the process debugging and development cycle, stabilizes product quality, broadens processing ideas, and identifies key influencing factors in the soft nitriding process debugging.

[0005] The technical solution adopted in this invention is a process method for controlling the depth of the soft nitriding hardness layer, comprising the following steps: 1) Equipment selection and basic parameter determination: Select the soft nitriding furnace model according to the size of the workpiece, and determine the furnace volume, replacement gas exchange rate and ammonia decomposition rate of the soft nitriding furnace according to the selected soft nitriding furnace. 2) Basic atmosphere flow rate calculation: Calculate the ammonia flow rate Qn according to the following formula: Qn=V×n / a Where V is the furnace volume of the soft nitriding furnace, in meters. 3 n represents the number of air replacements; a represents the ammonia decomposition rate, in percentage; and the ammonia flow rate Qn is in meters per second (m³). 3 / h; Calculate the ethanol flow rate Qc using the following formula: Qc=K×Qn Wherein, K is the ratio of ethanol flow rate Qc to ammonia flow rate Qn, and the value of K ranges from 0.1 to 0.2; The mass of ethanol dripped per minute, Mc, is determined based on the ethanol flow rate, Qc. Mc = Qc × 1000 (ml / L) × ρ / 60, Where ρ is the density of ethanol, in g / ml; at 20℃, the density of ethanol ρ = 0.789 g / ml; the mass of ethanol dropped per minute Mc is in g / min. Number of ethanol drops per minute (N): N=Mc / mc Where mc is the mass of one drop of ethanol, in g. Experimental calculations show that the mass of one drop of ethanol is approximately 0.02–0.05 g; the number of ethanol drops per minute (N) is measured in drops / min. 3) Exhaust operation: Open the cooling water pipe valve of the soft nitriding furnace to connect the cooling water, then start the fan and connect the power supply to raise the furnace temperature of the soft nitriding furnace to the preset temperature and keep it at that temperature for 60-90 minutes; after keeping it at that temperature for 30 minutes, adjust the dripping rate of the ethanol dripper to 70-100 drops / min, and perform preliminary exhaust by dripping ethanol. At the same time, turn on the exhaust gas combustion device of the soft nitriding furnace to combust the exhaust gas. 4) Furnace temperature calibration and stabilization: Raise the furnace temperature from the preheating temperature to 570±10℃, hold it for 30 to 60 minutes, and then use a standard thermocouple to calibrate the furnace temperature to ensure that the furnace temperature is stable within the range of 570±10℃. 5) Loading the workpiece into the furnace and secondary exhaust: Transfer the workpiece to be processed into the soft nitriding furnace and adjust the ethanol dripping rate to 100-120 drops / min for secondary exhaust. 6) Soft nitriding treatment: Based on the basic ammonia flow rate Qn and ethanol drop number N determined in step 2), the actual ammonia flow rate is maintained at Qn±1.0 and the actual ethanol drop number is maintained within the range of (N-10) to (N+40). The workpiece is subjected to soft nitriding treatment at a furnace temperature of 570±10℃ for 6 hours. 7) Diffusion dehydrogenation: After the soft nitriding treatment of the workpiece is completed, the supply of ammonia gas is stopped, and ethanol is continuously dripped in to perform diffusion dehydrogenation on the workpiece. The dehydrogenation time is 15 to 60 minutes. 8) Cooling and testing: Transfer the dehydrogenated workpiece to an oil bath for cooling. After the workpiece has cooled to room temperature, test the thickness of the white bright layer, the thickness of the diffusion layer, and the hardness of the workpiece surface. 9) Based on the technical parameter ranges of ammonia and ethanol in step 6), determine multiple sets of technical parameter combinations for actual ammonia flow rate and actual ethanol dripping number. Repeat steps 3) to 8) for each set of technical parameters to obtain the mutual constraint relationship between actual ammonia flow rate and actual ethanol dripping number and the white gloss layer and surface hardness of soft nitriding.

[0006] In step 3) above, the preset temperature is 450±10℃.

[0007] In step 5) above, the secondary exhaust time is 45 to 60 minutes.

[0008] In step 9) above, based on the test results of each set of technical parameters, it is concluded that: when the actual ammonia flow rate is consistent, the actual number of ethanol drops is directly proportional to the thickness of the diffusion layer; when the actual number of ethanol drops is consistent, the actual ammonia flow rate is directly proportional to the white gloss layer and surface hardness of the soft nitrided layer.

[0009] Advantages of this invention compared to existing technologies: 1. This technical solution uses the calculated basic atmosphere content as the basis for adjustment. Based on the basic atmosphere content, the workpiece is soft nitrided according to the optimized ammonia and ethanol parameters. The mutual constraint relationship between ammonia flow rate and ethanol dripping amount on the white bright layer and surface hardness of nitriding is determined, so as to achieve control over the depth of the soft nitriding hardness layer. 2. This technical solution establishes a quantitative relationship between ammonia flow rate, ethanol dripping amount, and the white bright layer, diffusion layer, and surface hardness. Based on the performance requirements of different diesel engine components (e.g., high wear-resistant components require a thick white bright layer, while high fatigue strength components require a reasonable diffusion layer), the process parameters can be precisely adjusted to achieve a wide range of control over the hardness layer depth. 3. This invention employs a gaseous nitrogen-carbon co-infiltration process, which avoids the salt residue pollution problem caused by salt bath nitriding; at the same time, by accurately calculating the amount of ammonia and ethanol used, gas waste is reduced, production costs are lowered, and the requirements of green production are met. 4. This technical solution is easy to operate and allows for precise control of the amount of ethanol and ammonia used. It not only ensures the technical specifications of the product but also optimizes the resources for the soft nitriding process, shortens the process debugging and development cycle, stabilizes product quality, broadens processing ideas, and helps to understand the key influencing factors in the debugging of the soft nitriding process. Attached Figure Description

[0010] Figure 1 This is a metallographic image of the soft nitrided white bright layer of Embodiment 1 of the present invention; Figure 2 This is a metallographic image of the soft nitride diffusion layer in Embodiment 1 of the present invention; Figure 3 This is a metallographic image of the soft nitrided white bright layer in Embodiment 2 of the present invention; Figure 4 This is a metallographic image of the soft nitride diffusion layer in Embodiment 2 of the present invention; Figure 5 This is a metallographic image of the soft nitrided white bright layer in Embodiment 3 of the present invention; Figure 6 This is a metallographic image of the soft nitriding diffusion layer in Embodiment 3 of the present invention. Detailed Implementation

[0011] The following will be based on embodiments of the present invention. Figure 1-6 The technical solutions in the embodiments of the present invention are clearly and completely described herein. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0012] In this document, the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0013] A process for controlling the depth of the soft nitriding hardness layer, characterized by comprising the following steps: 1) Equipment selection and basic parameter determination: Select the soft nitriding furnace model according to the size of the workpiece. That is, select the matching soft nitriding furnace model (such as pit-type soft nitriding furnace or box-type soft nitriding furnace) based on the maximum external dimensions (length, diameter, height) of the workpiece to be processed (such as diesel engine piston pin, rocker arm shaft) and the number of pieces loaded at one time. Ensure that the workpiece can be heated evenly in the furnace chamber and does not interfere with the furnace wall or the tooling inside the furnace. Based on the selected soft nitriding furnace, determine the furnace chamber volume, replacement gas exchange rate and ammonia decomposition rate of the soft nitriding furnace, make reasonable use of the furnace chamber size and optimize resource allocation. 2) Basic atmosphere flow rate calculation: Calculate the ammonia flow rate Qn according to the following formula: Qn=V×n / a Where V is the furnace volume of the soft nitriding furnace, in meters. 3 n represents the number of air replacements; a represents the ammonia decomposition rate, in percentage; and the ammonia flow rate Qn is in meters per second (m³). 3 / h; where, the replacement air exchange rate is determined according to the furnace volume and the amount of workpiece loaded into the furnace. The principle is to ensure that the air in the furnace can be fully replaced into a nitriding atmosphere. The value is usually in the range of 4-8 times (the larger the amount of workpiece loaded into the furnace, the more the air exchange rate needs to be increased to avoid residual air affecting the nitriding effect); the ammonia decomposition rate 'a' is determined according to the heating method of the soft nitriding furnace (resistance heating, induction heating) and the sealing of the furnace. It is generally controlled at 30%-50% (too low a decomposition rate will lead to insufficient nitrogen source, while too high a rate will produce too much hydrogen, affecting the stability of the atmosphere. It can be monitored and adjusted in real time by an in-furnace gas analyzer). Calculate the ethanol flow rate Qc using the following formula: Qc=K×Qn Wherein, K is the ratio of ethanol flow rate Qc to ammonia flow rate Qn, and the value of K ranges from 0.1 to 0.2. When the workpiece requires a thick white bright layer, K is taken as the upper limit of 0.15-0.2; when it is necessary to improve the fatigue strength of the diffusion layer, K is taken as the lower limit of 0.1-0.15. The mass of ethanol dripped per minute, Mc, is determined based on the ethanol flow rate, Qc. Mc = Qc × 1000 (ml / L) × ρ / 60, Where ρ is the density of ethanol, in g / ml; at 20℃, the density of ethanol ρ = 0.789 g / ml; the mass of ethanol dropped per minute Mc is in g / min. Number of ethanol drops per minute (N): N=Mc / mc Where mc is the mass of one drop of ethanol, in g. Experimental calculations show that the mass of one drop of ethanol is approximately 0.02–0.05 g; the number of ethanol drops per minute (N) is measured in drops / min. 3) Exhaust Operation: Open the cooling water pipe valve of the soft nitriding furnace to connect the cooling water, then start the fan and connect the power supply to raise the furnace temperature to 450±10℃ and hold it for 60-90 minutes. After holding for 30 minutes, adjust the dripping rate of the ethanol dispenser to 70-100 drops / min to perform initial exhaust by dripping ethanol. At the same time, turn on the exhaust gas combustion device of the soft nitriding furnace to burn the exhaust gas. This initial exhaust replaces the oxygen in the furnace and increases the reducing atmosphere, laying a good foundation for the soft nitriding layer structure. The purpose of the exhaust operation is to remove air (mainly oxygen and nitrogen) from the furnace to prevent air from reacting with ammonia and ethanol to form oxides (affecting the density of the white bright layer) or inert gases (impeding the penetration of nitrogen and carbon). 4) Furnace temperature calibration and stabilization: Raise the furnace temperature from 450±10℃ to 570±10℃, hold for 30 to 60 minutes, and then use a standard thermocouple to calibrate the furnace temperature to ensure that the furnace temperature is stable within the range of 570±10℃. Since the soft nitriding temperature is a key factor affecting the diffusion rate of nitrogen and carbon atoms, it is necessary to ensure that the furnace temperature is accurately stabilized at 570±10℃. 5) Loading the workpiece into the furnace and secondary exhaust: Transfer the workpiece to be processed into the soft nitriding furnace, adjust the ethanol dripping rate to 100-120 drops / min for secondary exhaust, and the secondary exhaust time is 45-60min. 6) Soft nitriding treatment: Soft nitriding treatment is the core stage for nitrogen and carbon atoms to penetrate into the surface of the workpiece. It is necessary to strictly control the atmosphere parameters and treatment time. That is, according to the basic ammonia flow rate Qn and ethanol drop number N determined in step 2), the actual ammonia flow rate should be maintained at Qn±1.0 and the actual ethanol drop number should be maintained within the range of (N-10) to (N+40). The workpiece should be soft nitrided at a furnace temperature of 570±10℃. The soft nitriding treatment time is set at 6h (this time can be slightly adjusted according to the required hardness and layer depth of the workpiece: it can be extended to 6.5-7h when a thick white gloss layer is required, and shortened to 5.5-6h when a thin white gloss layer is required, but the adjustment range should not exceed 1h to avoid affecting the performance of the diffusion layer). 7) Diffusion Dehydrogenation: After the workpiece has undergone soft nitriding, the ammonia flow supply is stopped, and ethanol is continuously dripped in to perform diffusion dehydrogenation on the workpiece. The dehydrogenation time is 15-60 minutes. A reducing gas is continuously introduced into the furnace to ensure that the H atoms from the ammonia cracking are fully combusted, preventing increased brittleness after soft nitriding. During the soft nitriding process, ammonia decomposes to produce hydrogen, and some of the hydrogen will penetrate into the workpiece (leading to hydrogen embrittlement and reducing the fatigue strength of the workpiece), which needs to be removed by diffusion dehydrogenation. 8) Cooling and testing: Transfer the dehydrogenated workpiece to an oil bath for cooling. After the workpiece has cooled to room temperature, test the thickness of the white bright layer, the thickness of the diffusion layer, and the hardness of the workpiece surface. 9) Based on the technical parameter ranges of ammonia and ethanol in step 6), determine multiple combinations of technical parameters for actual ammonia flow rate and actual ethanol drop count. Repeat steps 3) to 8) for each set of technical parameters to obtain the mutual constraint relationship between actual ammonia flow rate, actual ethanol drop count, and the white gloss layer and surface hardness of soft nitriding. Specifically, based on the test results of each set of technical parameters, it is found that: when the actual ammonia flow rate is consistent, the actual ethanol drop count is directly proportional to the diffusion layer thickness; when the actual ethanol drop count is consistent, the actual ammonia flow rate is directly proportional to the white gloss layer and surface hardness of soft nitriding.

[0014] Based on the above steps, the effective dimensions of the soft nitriding furnace used in Examples 1-3 of this experiment are Φ450×1000mm, and the furnace chamber volume is 0.15m³. 3 The number of air replacement cycles is 4, and the ammonia decomposition rate is 30%. The range can be selected according to specific circumstances. Basic atmosphere flow rate calculation: n=4, ammonia flow rate Qn=V×n / a=0.15×4÷0.3=2.0m 3 / h; Ethanol flow rate: K is taken as 0.1, Qc = K × Qn = 0.1 × 2.0 = 0.2 m 3 / h, and then based on the ethanol flow rate, determine the mass of ethanol dripped per minute Mc = Qc × 1000 (ml / L) × ρ / 60 = 0.2 × 1000 × 0.79 / 60 = 2.6 g / min, mc = 0.05, N = Mc / mc, 2.6 / 0.05 = 52 drops / min; Example 1 The amounts of ethanol and ammonia used in the process are as follows: 1) Actual ethanol drip rate: 45±10 drops / min; actual ammonia flow rate: 2.2~2.5m³. 3 / h; 2) The test results are as follows: Figure 1 As shown, the bright white metallographic layer has a depth of approximately 4 μm and a hardness value of 734.1 HV0.3; Figure 2 As shown, the soft nitride diffusion layer is metallographic with a depth of approximately 0.20 mm; Example 2 The amounts of ethanol and ammonia used in the process are as follows: 1) Actual ethanol drip rate: 70±10 drops / min; actual ammonia flow rate: 2.2~2.5m³. 3 / h; 2) The test results are as follows: Figure 3 As shown, the white metallographic layer has a depth of approximately 14 μm and a hardness of 803.1 HV0.3. Figure 4 As shown, the depth of the soft nitride diffusion layer metallographic layer is approximately 0.4 mm; Example 3 The amounts of ethanol and ammonia used in the process are as follows: 1) Actual ethanol drip rate: 70±10 drops / min; actual ammonia flow rate: 1.2~1.5m³. 3 / h; 2) The test results are as follows; such as Figure 5 As shown: a bright white metallographic layer, approximately 11 μm deep; hardness value 556.1 HV0.3, as... Figure 6 As shown, the depth of the soft nitrided diffusion layer metallographic layer is approximately 0.35 mm.

[0015] This technical solution uses a calculated base atmosphere content as the basis for adjustment. Based on the base atmosphere content and optimized ammonia and ethanol parameters, the workpiece is soft-nitrided. The interrelationship between ammonia flow rate and ethanol dripping amount and the bright white layer and surface hardness of the nitrided material is determined. It is found that when the actual ammonia flow rate is consistent, the actual ethanol dripping amount is directly proportional to the diffusion layer thickness; when the actual ethanol dripping amount is consistent, the actual ammonia flow rate is directly proportional to the bright white layer and surface hardness of the soft nitrided material, thus achieving control over the depth of the soft nitrided hardness layer. This solution is easy to operate, allows for precise control of the ethanol and ammonia usage, ensures product technical specifications, optimizes resources in the soft nitriding process, shortens the process debugging and development cycle, stabilizes product quality, broadens processing ideas, and identifies key influencing factors in the soft nitriding process debugging.

[0016] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0017] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A process method for controlling the depth of the soft nitriding hardness layer, characterized in that... Includes the following steps: 1) Equipment selection and basic parameter determination: Select the soft nitriding furnace model according to the size of the workpiece, and determine the furnace volume, replacement gas exchange rate and ammonia decomposition rate of the soft nitriding furnace according to the selected soft nitriding furnace. 2) Basic atmosphere flow rate calculation: Calculate the ammonia flow rate Qn according to the following formula: Qn=V×n / a Where V is the furnace volume of the soft nitriding furnace, in meters. 3 n represents the number of air replacements; a represents the ammonia decomposition rate, in percentage; and the ammonia flow rate Qn is in meters per second (m³). 3 / h; Calculate the ethanol flow rate Qc using the following formula: Qc=K×Qn Wherein, K is the ratio of ethanol flow rate Qc to ammonia flow rate Qn, and the value of K ranges from 0.1 to 0.2; The mass of ethanol dripped per minute, Mc, is determined based on the ethanol flow rate, Qc. Mc = Qc × 1000 (ml / L) × ρ / 60, Where ρ is the density of ethanol, in g / ml; at 20℃, the density of ethanol ρ = 0.789 g / ml; the mass of ethanol dropped per minute Mc is in g / min. Number of ethanol drops per minute (N): N=Mc / mc Where mc is the mass of one drop of ethanol, in g. The volume of one drop of ethanol is calculated to be approximately 0.02–0.05 g based on experiments; the number of ethanol drops per minute N is in drops / min. 3) Exhaust operation: Open the cooling water pipe valve of the soft nitriding furnace to connect the cooling water, then start the fan and connect the power supply to raise the furnace temperature of the soft nitriding furnace to the preset temperature and keep it at that temperature for 60-90 minutes; after keeping it at that temperature for 30 minutes, adjust the dripping rate of the ethanol dripper to 70-100 drops / min, and perform preliminary exhaust by dripping ethanol. At the same time, turn on the exhaust gas combustion device of the soft nitriding furnace to combust the exhaust gas. 4) Furnace temperature calibration and stabilization: Raise the furnace temperature from the preheating temperature to 570±10℃, hold it for 30 to 60 minutes, and then use a standard thermocouple to calibrate the furnace temperature to ensure that the furnace temperature is stable within the range of 570±10℃. 5) Loading the workpiece into the furnace and secondary exhaust: Transfer the workpiece to be processed into the soft nitriding furnace and adjust the ethanol dripping rate to 100-120 drops / min for secondary exhaust. 6) Soft nitriding treatment: Based on the basic ammonia flow rate Qn and ethanol drop number N determined in step 2), the actual ammonia flow rate is maintained at Qn±1.0 and the actual ethanol drop number is maintained within the range of (N-10) to (N+40). The workpiece is subjected to soft nitriding treatment at a furnace temperature of 570±10℃ for 6 hours. 7) Diffusion dehydrogenation: After the soft nitriding treatment of the workpiece is completed, the supply of ammonia gas is stopped, and ethanol is continuously dripped in to perform diffusion dehydrogenation on the workpiece. The dehydrogenation time is 15 to 60 minutes. 8) Cooling and testing: Transfer the dehydrogenated workpiece to an oil bath for cooling. After the workpiece has cooled to room temperature, test the thickness of the white bright layer, the thickness of the diffusion layer, and the hardness of the workpiece surface. 9) Based on the technical parameter ranges of ammonia and ethanol in step 6), determine multiple sets of technical parameter combinations for actual ammonia flow rate and actual ethanol dripping number. Repeat steps 3) to 8) for each set of technical parameters to obtain the mutual constraint relationship between actual ammonia flow rate and actual ethanol dripping number and the white gloss layer and surface hardness of soft nitriding.

2. The process method for controlling the depth of the soft nitriding hardness layer according to claim 1, characterized in that: In step 3) above, the preset temperature is 450±10℃.

3. The process method for controlling the depth of the soft nitriding hardness layer according to claim 1, characterized in that: In step 5) above, the secondary exhaust time is 45 to 60 minutes.

4. The process method for controlling the depth of the soft nitriding hardness layer according to claim 1, characterized in that: In step 9) above, based on the test results of each set of technical parameters, it is concluded that: when the actual flow rate of ammonia is consistent, the actual number of ethanol drops is directly proportional to the thickness of the diffusion layer. When the actual number of ethanol drops is consistent, the actual flow rate of ammonia is directly proportional to the white gloss layer and surface hardness of the soft nitrided surface.

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