Gas nitriding process method for 3J68 high-temperature elastic alloy shaft parts

Abstract

The invention discloses a 3J68 high-temperature elastic alloy shaft part gas nitriding process method. The 3J68 high-temperature elastic alloy shaft part gas nitriding process method comprises the steps that 1, a 3J68 high-temperature elastic alloy shaft part is pretreated; 2, drying the quartz sand, mixing ammonium chloride with the quartz sand, and charging the mixture into a furnace along with the part; step 3, charging the parts into a furnace; 4, nitrogen is introduced into the furnace, and exhaust is conducted; 5, the temperature of the nitriding furnace is increased to 400 DEG C or above, ammonia gas is introduced into the furnace in two paths, one path is constant ammonia, the flow of the constant ammonia is 5 L / min-15 / min, the other path is controlled ammonia, and the flow of the controlled ammonia is 5 L / min; step 6, heating the nitriding furnace to 530 DEG C + / -5 DEG C, detecting whether the decomposition rate of ammonia in the furnace is 30%-50% or not, if yes, preserving heat for 60 h + / -1 h, and if not, adjusting the constant ammonia flow in the step 5 until the decomposition rate of the ammonia in the furnace is 30%-50%; and step 8, stopping introducing the ammonia gas into the furnace, introducing nitrogen into the furnace, cooling the part to below 150 DEG C along with the furnace, and discharging the part from the furnace.

Description

Technical Field

[0001] The invention relates to the field of surface modification heat treatment of metal materials, and in particular to a gas nitriding process method for 3J68 high-temperature elastic alloy shaft parts. Background Art

[0002] 3J68 is a nickel-based high-temperature high-elastic alloy with high high-temperature strength and high high-temperature elasticity. It is mainly used to manufacture elastic components such as pins, bases, valves, etc. that work in high-temperature environments below 600°C. In order to improve the wear resistance of parts, nitriding treatment is required on the surface of the parts. The hardness of the nitriding layer is required to be greater than 800HV and the thickness of the nitriding layer is ≥5μm.

[0003] Since Ni and N elements cannot form alloy nitriding products during the nitriding process, parts that are partially nitrided are generally treated with nickel plating to prevent nitriding. The mass fraction of Ni in 3J68 alloy is about 68%, the mass fraction of Cr is about 19%, the mass fraction of Ti is about 3%, the mass fraction of W is about 10%, and the mass fraction of Al is about 1.5%. Although alloy elements such as Cr, W, and Ti can form alloy nitriding products during nitriding and can be nitrided, nitriding treatment is very difficult due to the high Ni content. The industry is not yet mature in the research of gas nitriding process for 3J68 materials, and gas nitriding technology is still blank in the aviation industry system and there are no relevant technical parameters. Summary of the invention

[0004] The purpose of the present invention is to provide a gas nitriding process method for 3J68 high temperature elastic alloy shaft parts, and to improve the surface hardness of 3J68 high temperature elastic alloy shaft parts and the wear resistance of the parts through the gas nitriding process method.

[0005] Technical solution:

[0006] A gas nitriding process for 3J68 high temperature elastic alloy shaft parts, comprising the following steps:

[0007] Step 1: Pre-treat the 3J68 high temperature and high elasticity alloy shaft parts, and clean the surface of the 3J68 high temperature and high elasticity alloy shaft parts after pre-treatment;

[0008] Step 2: Dry the quartz sand, mix the ammonium chloride and quartz sand in a certain proportion, put them into the catalytic box, and load them into the furnace together with the parts;

[0009] Step 3: 3J68 high temperature and high elastic alloy shaft parts are loaded into the furnace;

[0010] Step 4: introduce nitrogen into the furnace and exhaust it;

[0011] Step 5: The temperature of the nitriding furnace is raised to above 400°C, and ammonia is introduced into the furnace in two ways, one of which is constant ammonia with a flow rate of 5L / min to 15 / min, and the other is controlled ammonia with a flow rate of 5L / min;

[0012] Step 6: The nitriding furnace is heated to 530°C ± 5°C, and the ammonia decomposition rate in the furnace is detected to be between 30% and 50%. If so, step 7 is performed; otherwise, the constant ammonia flow rate in step 5 is adjusted until the ammonia decomposition rate in the furnace is between 30% and 50%.

[0013] Step 7: Keep the 3J68 high temperature and high elastic alloy shaft parts at 530℃±5℃ for 60h±1h;

[0014] Step 8: Stop introducing ammonia into the furnace and 3 ~3m 3 / h nitrogen is introduced into the furnace, and the temperature of 3J68 high temperature and high elastic alloy shaft parts is reduced to below 150℃ along with the furnace, and the introduction of nitrogen is stopped and the parts are taken out of the furnace.

[0015] Further, in step 1, the 3J68 high temperature and high elasticity alloy shaft parts are pretreated, including solution treatment and aging treatment;

[0016] Solution treatment: put 3J68 high temperature and high elastic alloy shaft parts into a box-type electric furnace for preheating, the preheating temperature is 650-660℃, keep warm for 40-50min; then heat to 1080±10℃, keep warm for 40-50min, and water cool;

[0017] Aging treatment: Place 3J68 high temperature and high elastic alloy shaft parts into a box-type electric furnace, heat to 800±10℃, keep warm for 180-190min; cool down to 700±10℃ with the furnace, keep warm for 240-250min, and air cool.

[0018] Further, in step 2, quartz sand is dried at a temperature of 280°C to 300°C and a holding time of 20min to 30min. After drying, the mixture is cooled to room temperature. Ammonium chloride and quartz sand are mixed in a ratio of 50g:150g, placed in a catalytic box, and loaded into the furnace together with the parts.

[0019] Further, in step 3, the 3J68 high temperature elastic alloy shaft parts are vertically inserted into the holes of the furnace loading tooling, wherein the furnace loading tooling is a plate mesh structure with holes.

[0020] Further, step 4: nitrogen is introduced into the furnace and exhausted; the nitrogen flow rate is 2-3m 3 / h, exhaust time 50min~70min, after exhausting, stop introducing nitrogen and start heating.

[0021] Further, step 6 specifically includes the following steps:

[0022] Step 6.1 Open the valve of the nitriding furnace test gas inlet and the test gas flow meter knob switch to ensure that the test gas flow meter value is 0.2L~0.5L / min;

[0023] Step 6.2: Adjust the opening of the constant ammonia valve to ensure that the pressure difference between the furnace and the atmosphere is within the range of 200 kPa to 1000 kPa;

[0024] Step 6.3: Fine-tune the constant ammonia and control the flow rate of ammonia to ensure that the ammonia decomposition rate is maintained at 30% to 50%.

[0025] Furthermore, in step 7, the 3J68 high temperature and high elastic alloy shaft parts are kept at 530°C ± 5°C for 60h ± 1h, while fine-tuning the constant ammonia and controlling the flow rate of ammonia to ensure that the ammonia decomposition rate is maintained at 40%.

[0026] Furthermore, the method further comprises step 9, cleaning the 3J68 high temperature elastic alloy shaft parts with clean kerosene and drying them.

[0027] Furthermore, the method further comprises step 10, inserting a single 3J68 high temperature elastic alloy shaft part into a foam board for packaging to prevent collision.

[0028] Beneficial effect: The present invention proposes a gas nitriding process for 3J68 high temperature elastic alloy shaft parts, which improves the surface hardness of 3J68 high temperature elastic alloy shaft parts and improves the wear resistance of the parts, so that the thickness of the nitriding layer of the parts is greater than 5μm, and the hardness of the nitriding layer is HV 0.1 Reach above 800, and the core hardness of the part HRC reaches above 35. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. It is obvious that the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 It is the solid solution process curve of the present invention;

[0031] Figure 2 It is the aging process curve of the present invention;

[0032] Figure 3 A top view of the furnace loading tooling of the present invention;

[0033] Figure 4 It is a side view of the furnace loading tooling of the present invention;

[0034] Figure 5 It is a schematic diagram of the parts structure;

[0035] Figure 6 It is a schematic diagram of clamping parts of the furnace loading tooling of the present invention. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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 making creative work are within the scope of protection of the present invention.

[0037] The features and illustrative embodiments of various aspects of the present invention will be described in detail below. In the detailed description below, many specific details are proposed to provide a comprehensive understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without the need for some of these specific details. The following description of the embodiments is only to provide a better understanding of the present invention by illustrating examples of the present invention. The present invention is by no means limited to any specific settings and methods proposed below, but covers any improvements, replacements and modifications of structures, methods, devices without departing from the spirit of the present invention. In the accompanying drawings and the following description, known structures and technologies are not shown to avoid unnecessary ambiguity in the present invention.

[0038] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other, and the embodiments can refer to and quote each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0039] One embodiment of the present invention is to provide a gas nitriding process method for 3J68 high temperature elastic alloy shaft parts, including solid solution and aging preparatory heat treatment before rough machining of 3J68 high temperature high elastic alloy shaft parts, and nitriding treatment after fine machining. Nitriding adopts RN2-50-80 type pit nitriding furnace, the furnace temperature uniformity is ±5℃, and an atmosphere circulation device is provided in the furnace to ensure uniform atmosphere. Before nitriding, quartz sand is dried at 280℃~300℃, and the insulation time is 20min~30min. After drying, it is cooled to room temperature, and then the catalyst ammonium chloride and quartz sand are evenly mixed in a mass ratio of 1:3, and then put into the nitriding box and loaded into the furnace with the parts.

[0040] The operator inserts the parts into the tray grid, and the parts are placed vertically with a spacing of 7mm between the parts. After the parts are put into the furnace, the furnace door is closed. The main valve, pressure reducer, and needle valve on the nitrogen pipeline are opened to supply nitrogen to the gas distribution cabinet. Nitrogen is introduced to exhaust, and the furnace pressure is controlled in a positive pressure state. The nitrogen bypass hand valve in the distribution cabinet is opened, and the nitrogen flow rate is 2 to 3m 3 / h. Start the operation after 50min to 70min of exhaust time. Press the fan start button, turn on the exhaust gas and ignite it, then start the heating.

[0041] The operator sets the nitriding process parameters: nitriding temperature 530℃±5℃, holding time 60h±1h, ammonia decomposition rate 30%~50%, and ammonia decomposition rate setting value 40%. When the furnace temperature reaches 400℃, open the ammonia main valve and the needle valve on the bus, adjust the outlet pressure of the ammonia pressure reducer to 0.06MPa~0.12MPa, close the nitrogen bypass hand valve after ammonia is introduced, open the constant ammonia needle valve and adjust it to 5L / min~15 / min, open the control ammonia needle valve and adjust the control ammonium flowmeter to a position close to 5L / min. After the main control instrument reaches the temperature, open the valve of the test gas inlet and the knob switch of the test gas flowmeter. And keep the test gas flowmeter value at 0.2L~0.5L / min. Adjust the opening of the constant ammonia valve and keep the pressure difference of the U-type pressure gauge at 200KPa~1000KPa. By adjusting the constant ammonia and controlling the flow of ammonia, ensure that the ammonia decomposition rate is maintained at 30%~50%. After nitriding, introduce nitrogen and maintain positive pressure in the furnace. The nitrogen flow rate is 2-3m 3 / h, then close the valve of the liquid ammonia tank, and finally close the main valve on the bus. Close the valve of the test gas inlet and the inlet knob of the test gas flow meter.

[0042] When the furnace temperature drops below 150℃, turn off the nitrogen and take the parts out of the furnace. When taking the parts out of the furnace, pay attention to: insert the parts into the foam board and pack them to prevent them from being bumped, clean the parts with clean kerosene, and dry them. Then insert the parts into the foam board and pack them to prevent them from being bumped.

[0043] Through the above-mentioned process method, the surface hardness of 3J68 high temperature elastic alloy shaft parts can be increased, and the wear resistance of the parts can be improved. The technical indicators of 3J68 high temperature elastic alloy shaft parts after the above-mentioned gas nitriding process method are shown in Table 1

[0044] Table 1 Technical indicators of 3J68 high temperature elastic alloy after nitriding

[0045] Serial number Material grade Nitriding layer thickness (um) <![CDATA[Hardness of nitrided layer (HV 0.1 )]]> Core hardness (HRC) 1 3J68 ≥5 ≥800 ≥35 .

[0046] A second embodiment of the present invention is:

[0047] A gas nitriding process for 3J68 high temperature elastic alloy shaft parts, comprising the following steps:

[0048] Step 1: Pre-treat the 3J68 high temperature and high elasticity alloy shaft parts, and clean the surface of the 3J68 high temperature and high elasticity alloy shaft parts after pre-treatment;

[0049] Pre-treatment of 3J68 high temperature and high elastic alloy shaft parts, including solution treatment and aging treatment;

[0050] Solution treatment: put 3J68 high temperature and high elastic alloy shaft parts into a box-type electric furnace for preheating, the preheating temperature is 650-660℃, keep warm for 40-50min; then heat to 1080±10℃, keep warm for 40-50min, and water cool;

[0051] Aging treatment: Place 3J68 high temperature and high elastic alloy shaft parts into a box-type electric furnace, heat to 800±10℃, keep warm for 180-190min; cool down to 700±10℃ with the furnace, keep warm for 240-250min, and air cool.

[0052] Solution treatment and aging treatment ensure that the core of the part is ≥HRC35, and prepare the structure for subsequent nitriding. The process parameters are the solution aging process parameters of 3J68 material. Different materials have different heat treatment process parameters.

[0053] Step 2: Dry the quartz sand, mix the ammonium chloride and quartz sand in a certain proportion, put them into a catalytic box, and load them into the furnace together with the parts; the quartz sand drying temperature is 280℃~300℃, and the insulation time is 20min~30min. After drying, cool to room temperature, mix the ammonium chloride and quartz sand in a ratio of 50g:150g, put them into a catalytic box, and load them into the furnace together with the parts.

[0054] In this step, the hydrogen chloride decomposed by ammonium chloride reacts with the oxide of the passivation film, such as chromium trioxide, and the reaction formula is as follows: Cr2O3+6HCl→2CrCl3+3H2O, thereby destroying the passivation film and allowing nitriding to proceed normally. The amount of ammonium chloride used has a great influence on the surface hardness and depth of the nitriding layer. If the amount is too much, pitting will occur on the surface of the workpiece, corroding the nitriding tank and blocking the pipeline; if the amount is too little, the effect of removing the passivation film is not good, and the nitriding layer will become thinner and uneven. Therefore, the amount of ammonium chloride used should be strictly controlled in production. Using this formula can solve the above problems and ensure the quality of parts after nitriding.

[0055] Quartz sand is easy to get wet when placed in the air for a long time, so use 280℃~300℃, keep warm for 20min~30min, and dry the quartz sand. Ammonium chloride and quartz sand are mixed in a ratio of 50g:150g=1:3 (mass ratio), which is an empirical exploration. The amount of ammonium chloride has a great influence on the surface hardness and depth of the nitriding layer. If the amount is too much, pitting will occur on the surface of the workpiece, corroding the nitriding tank and blocking the pipeline; if the amount is too little, the effect of removing the passivation film is not good, and the nitriding layer will be thinned and uneven.

[0056] Step 3: Loading 3J68 high temperature and high elastic alloy shaft parts into the furnace; specifically, vertically inserting the 3J68 high temperature elastic alloy shaft parts into the holes of the furnace loading tooling to prevent the parts from deforming, wherein the furnace loading tooling is a plate mesh structure with holes.

[0057] Step 4: Introduce nitrogen into the furnace and exhaust it; the nitrogen flow rate is 2-3m 3 / h, exhaust time 50min ~ 70min, ensure that there is no oxidizing atmosphere in the furnace, and ensure that the parts do not oxidize at high temperatures. After the exhaust is completed, stop introducing nitrogen and start heating. By adjusting the constant ammonia and controlling the flow of ammonia, ensure that the ammonia decomposition rate is maintained at 30% ~ 50%.

[0058] Step 5: The temperature of the nitriding furnace is raised to above 400°C, and ammonia is introduced into the furnace in two ways, one of which is constant ammonia with a flow rate of 5L / min to 15 / min, and the other is controlled ammonia with a flow rate of 5L / min;

[0059] Step 6: The nitriding furnace is heated to 530°C ± 5°C, and the ammonia decomposition rate in the furnace is detected to be between 30% and 50%. If so, step 7 is performed; otherwise, the constant ammonia flow rate in step 5 is adjusted until the ammonia decomposition rate in the furnace is between 30% and 50%.

[0060] The following steps are involved:

[0061] Step 6.1 Open the valve of the nitriding furnace test gas inlet and the test gas flow meter knob switch to ensure that the test gas flow meter value is 0.2L~0.5L / min;

[0062] Step 6.2: Adjust the opening of the constant ammonia valve to ensure that the pressure difference between the furnace and the atmosphere is within the range of 200 kPa to 1000 kPa;

[0063] Step 6.3: Fine-tune the constant ammonia and control the flow rate of ammonia to ensure that the ammonia decomposition rate is maintained at 30% to 50%.

[0064] Step 7, keep the 3J68 high temperature and high elastic alloy shaft parts at 530℃±5℃ for 60h±1h, and at the same time fine-tune the constant ammonia and control the ammonia flow rate to ensure that the ammonia decomposition rate is maintained at 40%.

[0065] The nitriding stage of the part designed by the present invention is a one-stage nitriding, including steps 6-7, which can make the heating rate of the part uniform and controllable, and the process parameters such as nitriding temperature and ammonia decomposition rate stable, so as to ensure that the part does not deform after nitriding, and the hardness and depth of the nitriding layer meet the requirements.

[0066] The gas nitriding temperature of 3J68 is 530±5℃, the holding time is 60h, the ammonia decomposition rate is 30%~50%, and the set value is 40%. This process parameter is the optimal process parameter after many tests. If this process parameter is not used, the hardness and nitriding layer depth of 3J68 gas nitriding will not meet the requirements. This process parameter is only applicable to gas nitriding of 3J68 material. Because the materials are different, the nitriding temperature, time, and ammonia decomposition rate are also different.

[0067] Step 8: Stop introducing ammonia into the furnace and 3 ~3m 3 / h introduce nitrogen into the furnace and maintain positive pressure in the furnace. When the temperature of 3J68 high-temperature and high-elasticity alloy shaft parts drops below 150℃ with the furnace, stop introducing nitrogen and take the parts out of the furnace. This can prevent the parts from high-temperature oxidation and eliminate the rest of the atmosphere in the furnace to ensure safety.

[0068] Step 9. Clean the 3J68 high temperature elastic alloy shaft parts with clean kerosene and dry them.

[0069] Step 10: Insert the single 3J68 high temperature elastic alloy shaft parts into the foam board for packaging to prevent bumps. Ensure the surface quality of the parts and prevent bumps.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the field can easily think of various equivalent modifications or substitutions within the technical scope disclosed by the present invention, and these modifications or substitutions should all be covered within the protection scope of the present invention.

Claims

1. A gas nitriding process for 3J68 high temperature elastic alloy shaft parts, characterized in that: The following steps are involved: Step 1: Pre-treat the 3J68 high temperature and high elasticity alloy shaft parts, and clean the surface of the 3J68 high temperature and high elasticity alloy shaft parts after pre-treatment; Step 2: Dry the quartz sand, mix the ammonium chloride and quartz sand in a certain proportion, put them into the catalytic box, and load them into the furnace together with the parts; Step 3: 3J68 high temperature and high elastic alloy shaft parts are loaded into the furnace; Step 4: Introduce nitrogen into the furnace and exhaust it; Step 5: The temperature of the nitriding furnace is raised to above 400°C, and ammonia is introduced into the furnace in two ways, one of which is constant ammonia with a flow rate of 5L / min to 15 / min, and the other is controlled ammonia with a flow rate of 5L / min; Step 6: The nitriding furnace is heated to 530°C ± 5°C, and the ammonia decomposition rate in the furnace is detected to be between 30% and 50%. If so, step 7 is performed; otherwise, the constant ammonia flow rate in step 5 is adjusted until the ammonia decomposition rate in the furnace is between 30% and 50%. Step 7: Keep the 3J68 high temperature and high elastic alloy shaft parts at 530℃±5℃ for 60h±1h; Step 8: Stop introducing ammonia into the furnace and 3 ~3m 3 / h nitrogen is introduced into the furnace, and the temperature of 3J68 high temperature and high elastic alloy shaft parts is reduced to below 150℃ along with the furnace, and the introduction of nitrogen is stopped and the parts are taken out of the furnace.

2. The gas nitriding process for 3J68 high temperature elastic alloy shaft parts according to claim 1 is characterized in that: In step 1, the 3J68 high temperature and high elasticity alloy shaft parts are pretreated, including solution treatment and aging treatment; Solution treatment: put 3J68 high temperature and high elastic alloy shaft parts into a box-type electric furnace for preheating, the preheating temperature is 650-660℃, keep warm for 40-50min; then heat to 1080±10℃, keep warm for 40-50min, and water cool; Aging treatment: Place 3J68 high temperature and high elastic alloy shaft parts into a box-type electric furnace, heat to 800±10℃, keep warm for 180-190min; cool down to 700±10℃ with the furnace, keep warm for 240-250min, and air cool.

3. The gas nitriding process for 3J68 high temperature elastic alloy shaft parts according to claim 2 is characterized in that: In step 2, quartz sand is dried at a temperature of 280°C to 300°C and a holding time of 20min to 30min. After drying, the mixture is cooled to room temperature. Ammonium chloride and quartz sand are mixed in a ratio of 50g:150g, placed in a catalytic box, and loaded into the furnace together with the parts.

4. The gas nitriding process for 3J68 high temperature elastic alloy shaft parts according to claim 3 is characterized in that: In step 3, the 3J68 high temperature elastic alloy shaft parts are vertically inserted into the holes of the furnace loading tooling, wherein the furnace loading tooling is a plate mesh structure with holes.

5. The gas nitriding process for 3J68 high temperature elastic alloy shaft parts according to claim 4 is characterized in that: Step 4: Introduce nitrogen into the furnace and exhaust it; the nitrogen flow rate is 2-3m 3 / h, exhaust time 50min~70min, after exhausting, stop introducing nitrogen and start heating.

6. The gas nitriding process for 3J68 high temperature elastic alloy shaft parts according to claim 5 is characterized in that: Step 6 specifically includes the following steps: Step 6.1 Open the valve of the nitriding furnace test gas inlet and the test gas flow meter knob switch to ensure that the test gas flow meter value is 0.2L~0.5L / min; Step 6.2: Adjust the opening of the constant ammonia valve to ensure that the pressure difference between the furnace and the atmosphere is within the range of 200 kPa to 1000 kPa; Step 6.3: Fine-tune the constant ammonia and control the flow rate of ammonia to ensure that the ammonia decomposition rate is maintained at 30% to 50%.

7. The gas nitriding process for 3J68 high temperature elastic alloy shaft parts according to claim 6 is characterized in that: In step 7, the 3J68 high temperature and high elastic alloy shaft parts are kept at 530°C ± 5°C for 60h ± 1h, while fine-tuning the constant ammonia and controlling the ammonia flow to ensure that the ammonia decomposition rate is maintained at 40%.

8. The gas nitriding process for 3J68 high temperature elastic alloy shaft parts according to claim 7 is characterized in that: The method also includes step 9, cleaning the 3J68 high temperature elastic alloy shaft parts with clean kerosene and drying them.

9. The gas nitriding process for 3J68 high temperature elastic alloy shaft parts according to claim 8, characterized in that: The method also includes step 10, inserting a single 3J68 high temperature elastic alloy shaft part into a foam board for packaging to prevent collision.

Images