Composite surface treatment method for metal fixed disc of automatic agricultural seeder

Abstract

The invention belongs to the technical field of surface treatment of metal materials, and particularly relates to a composite surface treatment method for a metal fixed disc of an automatic agricultural seeder, which comprises the following steps: S1, pretreatment; s2, shot blasting treatment; s3, high-temperature carbonitriding is carried out; s4, performing ultrasonic rolling post-treatment; and S5, ultrasonic cleaning. Through the combination of shot blasting, high-temperature carbonitriding and ultrasonic rolling treatment technologies, the surface performance (including strength and hardness, corrosion resistance, roughness, adhesive force and appearance quality) of the metal fixed disc is remarkably improved, and the metal fixed disc has higher reliability and durability in actual working condition application.

Description

Technical Field

[0001] The invention belongs to the technical field of surface treatment of metal materials, and in particular relates to a composite surface treatment method for a metal fixed plate of an automated agricultural seeding machine. Background Art

[0002] Agriculture is the foundation of a country and the basis of a strong country. At present, my country's agriculture has entered a stage of high-quality development, hoping to promote the rapid development of agricultural productivity through scientific and technological revolution. The mechanization of agricultural production is one of the key contents of the agricultural scientific and technological revolution. At present, some key technologies, parts materials and manufacturing processes of my country's agricultural machinery products are controlled by others, and there is a gap between major equipment and developed countries. The overall level of the agricultural machinery industry is not high, and there is a problem of "no machines available and no good machines to use" in some fields. For example, the reliability and service life of key components such as metal fixed plates in domestic automated seeding machines are somewhat different from those of imported seeding devices.

[0003] The metal plate made of 403 stainless steel works together with the metal paddle in the automatic seeder to complete the seed sowing work. It is necessary to ensure that the seeds can be output at a uniform speed and that the number of seeds is consistent each time. In the actual sowing process, the metal plate and the metal paddle will rub from time to time, which will cause friction and wear on the surface of the metal plate over time. Not only will pits be formed on the surface of the metal plate, causing stress concentration and seed jamming; it will also provide favorable conditions for corrosion at the pits. In the actual use of the metal plate, due to the doping of seeds and chemical fertilizers, the surface of the metal plate will be corroded to a great extent during the years of use. Therefore, how to ensure the service life and sowing stability of the metal plate has become a problem that needs to be solved urgently. As a key component in the seeder, the metal plate is limited by factors such as tensile strength, yield strength, surface hardness and service life under working conditions.

[0004] In recent years, there are mainly the following methods for metal surface processing:

[0005] 1. Surface modification technology by changing the chemical composition of the material surface;

[0006] 2. Surface treatment technologies that change the organizational structure without changing the chemical composition of the material surface, such as roller pressing, laser heat treatment, and nano-processing;

[0007] 3. Surface coating technology that prepares a coating with better performance on the surface of the substrate.

[0008] However, in practical applications, it is found that the above-mentioned single surface treatment method can hardly meet the performance indicators required by the increasingly developed materials. Summary of the invention

[0009] The technical problem to be solved by the present invention is to provide a composite surface treatment method for the metal fixed plate of an automated agricultural seeder in view of the deficiencies in the prior art. The present invention can effectively improve the thickness, hardness and wear resistance of the strengthening layer of the metal fixed plate of the automated agricultural seeder and combines the actual working conditions of the metal fixed plate, so that the metal fixed plate can perform better in actual use, and the process operation process is simple and practical.

[0010] This scheme is achieved through the following technical measures: A composite surface treatment method for a metal plate of an automated agricultural seeding machine, which includes the following steps:

[0011] S1: Pretreatment: grinding the surface of the metal plate to remove oil and rust from the surface of the metal plate, cleaning it with anhydrous ethanol, and drying it for later use;

[0012] S2: Shot peening, using cast steel shots of conventional hardness as shot peening media to shot peen the metal plate, clean the surface after treatment, and dry it for later use;

[0013] S3: High-temperature carbonitriding: put the workpiece into a gas carburizing furnace for carbonitriding. After carbonitriding is completed, the temperature is lowered to below 700°C, the carbon supply is stopped, the metal plate is taken out, and put into oil for rapid cooling;

[0014] S4: ultrasonic rolling post-processing, using a processing platform including a vertical machining center and an ultrasonic surface rolling device to process the surface of the metal plate;

[0015] S5: Ultrasonic cleaning: put the metal plate into anhydrous ethanol for ultrasonic cleaning for 15-30 minutes, and then dry it.

[0016] Preferably, in step S2, the residual compressive stress and residual compressive stress depth of the metal platen surface after shot peening are calculated using the Almen test piece method, and the formula used is as follows:

[0017]

[0018] Where: f is the arc height; h is the thickness of the test piece; E is the elastic modulus; v is the Poisson coefficient; σ mr is the average residual compressive stress in the strengthening layer; δr is the residual compressive stress depth; a is the equation constant, representing the intensity of the shot peening process.

[0019] Preferably, the high temperature carbonitriding step in step S3 is as follows:

[0020] (a) preparing an osmotic mixture: selecting 30% ammonia and 70% methanol as co-osmotic agents, and adding carbon tetrachloride and titanium chloride in a weight ratio of 3:1-5:1 to the methanol as activators to prepare an osmotic mixture;

[0021] (b) Exhaust stage: The carbonitriding furnace is preheated, and the heating rate is maintained at 10-15°C / min. At the same time, the dripping amount of the catalytic mixture is 80-100 drops / min, the methanol flux is 100-150L / h, and the time is 30min. At this time, the temperature in the furnace is between 300-450°C;

[0022] (c) Strong infiltration stage: the dripping rate of the infiltration mixture is 60-65 drops / min, the methanol flux is 400-450L / h, the furnace pressure is maintained at 30-40mm oil column, the furnace temperature is continuously increased, the heating rate is maintained at 10-15℃ / min, the time is 1-3 hours, and the furnace temperature is about 600-900℃;

[0023] (d) Heating and diffusion stage: the dripping rate of the catalytic mixture is 50-55 drops / min, the methanol flux is 500-600 L / h, the furnace pressure is increased to 50-70 mm oil column, the furnace temperature is stably maintained at 850-950 ° C, and the temperature is kept for 15-17 hours, while nitrogen is introduced as a protective gas;

[0024] (e) Cooling stage: stop dripping the catalytic mixture, turn off the power, stop heating, maintain the methanol flux at 600 L / h, and keep the furnace pressure at 60 mm oil column;

[0025] (f) After the carbonitriding furnace is cooled to below 700°C, the carbon supply is stopped, the metal plate is taken out and placed in oil for rapid cooling.

[0026] Preferably, the ultrasonic rolling post-processing method in step S4 is: using a processing platform including a vertical machining center and an ultrasonic surface rolling device, the ball moves 3mm at both ends of the metal plate, the downward pressure is selected to be 1mm, and oil lubrication is continuously performed during the ultrasonic rolling process.

[0027] Preferably, the adjustable parameters of the ultrasonic surface rolling device are: feed speed, static pressure, rolling times, step distance, amplitude, and a 5-factor 4-level ultrasonic rolling processing orthogonal experiment is designed according to the value range of each parameter, wherein:

[0028] Rolling times (times): 3, 4, 5, 6;

[0029] Amplitude (μm): 6, 8, 10, 12;

[0030] Static pressure (N): 400, 500, 600, 700;

[0031] Feed speed (m / min): 0.8, 1.0, 1.2, 1.4;

[0032] Step distance (mm): 0.15, 0.20, 0.25, 0.30.

[0033] Preferably, in step S2, the shot peening intensity of the metal plate surface is obtained by experiment using the Almen test piece method, and the shot peening time is 45-50 seconds; wherein the arc height value-time curve equation used in the Almen test piece method is as follows:

[0034] f=a(1-e-bt)

[0035] Where: f is the arc height value; t is the shot peening time; a is the equation constant, representing the saturation level of the arc height value after a sufficiently long shot peening time; b is the equation constant, which is related to the rate of the shot peening process and affects the speed at which the arc height value reaches the saturation state; e is the base of the natural logarithm, which is approximately equal to 2.71828.

[0036] Preferably, in step S2, a pneumatic shot peening machine is used for shot peening, the spraying distance is 190 mm, the shot peening air pressure is 3 Bar, the shot peening flow rate is 10 kg / min, the shot peening coverage is 200%, and the shot peening time is 90-100 seconds.

[0037] Preferably, in step S1, 500-grit sandpaper is selected to grind the surface of the metal plate until a frosted sample with scratches in a consistent direction appears on the surface of the metal plate, anhydrous ethanol is dripped onto the surface of the metal plate, and then the surface of the metal plate is dried with a hair dryer.

[0038] Preferably, the metal plate is a 403 stainless steel plate with a length of 10 mm, a width of 10 mm and a height of 2 mm.

[0039] Beneficial effects of the present invention: The present invention significantly improves the performance of the metal plate surface (including strength, hardness, corrosion resistance, roughness, adhesion and appearance quality) through the combination of shot peening + high temperature carbonitriding + ultrasonic rolling treatment technology, so that the metal plate has higher reliability and durability in actual working conditions. It can be seen that compared with the prior art, the present invention has outstanding substantive characteristics and significant progress, and the beneficial effects of its implementation are also obvious. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a process flow chart of the present invention;

[0041] Figure 2 This is a comparison chart of hardness values ​​of Example 1, Example 2 and Example 3 of the present invention;

[0042] Figure 3 This is a comparison chart of the service life of Example 1, Example 2 and Example 3 of the present invention;

[0043] Figure 4 1 is the metallographic diagram of Example 1, Example 2 and Example 3 of the present invention. DETAILED DESCRIPTION

[0044] In order to clearly illustrate the technical features of this solution, this solution is described below through specific implementation methods and in conjunction with the accompanying drawings.

[0045] A composite surface treatment method for a metal plate of an automated agricultural seed drill comprises the following steps:

[0046] S1: Pretreatment: the metal plate is a 403 stainless steel plate with a length of 10 mm, a width of 10 mm, and a height of 2 mm. Use 500-grit sandpaper to grind the surface of the metal plate to remove oil and rust on the surface of the metal plate until the surface of the metal plate has a frosted pattern with scratches in the same direction. Then, add anhydrous ethanol to the surface of the metal plate, wash it with anhydrous ethanol, and then use a hair dryer to dry the surface of the metal plate for later use;

[0047] S2: Shot peening, using cast steel shot of conventional hardness (40-50HRC) as the shot peening medium, using a pneumatic shot peening machine to peen the metal plate, the spray distance is 190mm, the shot peening air pressure is 3Bar, the shot peening flow rate is 10kg / min, the shot peening coverage is 200%, and the shot peening time is 90-100 seconds. After shot peening, the surface of the metal plate is cleaned and dried for standby use;

[0048] S3: High-temperature carbonitriding: put the workpiece into a gas carburizing furnace for carbonitriding. After carbonitriding is completed, the temperature is lowered to below 700°C, the carbon supply is stopped, the metal plate is taken out, and put into oil for rapid cooling;

[0049] S4: ultrasonic rolling post-processing, using a processing platform including a vertical machining center and an ultrasonic surface rolling device to process the surface of the metal plate;

[0050] S5: Ultrasonic cleaning: put the metal plate into anhydrous ethanol for ultrasonic cleaning for 15-30 minutes, and then dry it.

[0051] In step S2, the shot peening intensity of the metal plate surface is obtained by experiment using the Almen test piece method, and the shot peening time is 45-50 seconds; wherein the arc height value-time curve equation used in the Almen test piece method is as follows:

[0052] f=a(1-e-bt)

[0053] Where: f is the arc height value; t is the shot peening time; a is the equation constant, representing the saturation level of the arc height value after a sufficiently long shot peening time; b is the equation constant, which is related to the rate of the shot peening process and affects the speed at which the arc height value reaches the saturation state; e is the base of the natural logarithm, which is approximately equal to 2.71828.

[0054] In step S2, the residual compressive stress and residual compressive stress depth of the metal plate surface after shot peening are calculated using the Almen test piece method, and the formula used is as follows:

[0055]

[0056] Where: f is the arc height; h is the thickness of the test piece; E is the elastic modulus; v is the Poisson coefficient; σ mr is the average residual compressive stress in the strengthening layer; δr is the residual compressive stress depth; a is the equation constant, representing the intensity of the shot peening process.

[0057] The high temperature carbonitriding step in step S3 is as follows:

[0058] (a) preparing an osmotic mixture: selecting 30% ammonia and 70% methanol as co-osmotic agents, and adding carbon tetrachloride and titanium chloride in a weight ratio of 3:1-5:1 to the methanol as activators to prepare an osmotic mixture;

[0059] (b) Exhaust stage: The carbonitriding furnace is preheated, and the heating rate is maintained at 10-15°C / min. At the same time, the dripping amount of the catalytic mixture is 80-100 drops / min, the methanol flux is 100-150L / h, and the time is 30min. At this time, the temperature in the furnace is between 300-450°C;

[0060] (c) Strong infiltration stage: the dripping rate of the infiltration mixture is 60-65 drops / min, the methanol flux is 400-450L / h, the furnace pressure is maintained at 30-40mm oil column, the furnace temperature is continuously increased, the heating rate is maintained at 10-15℃ / min, the time is 1-3 hours, and the furnace temperature is about 600-900℃;

[0061] (d) Heating and diffusion stage: the dripping rate of the catalytic mixture is 50-55 drops / min, the methanol flux is 500-600 L / h, the furnace pressure is increased to 50-70 mm oil column, the furnace temperature is stably maintained at 850-950 ° C, and the temperature is kept for 15-17 hours, while nitrogen is introduced as a protective gas;

[0062] (e) Cooling stage: stop dripping the catalytic mixture, turn off the power, stop heating, maintain the methanol flux at 600 L / h, and keep the furnace pressure at 60 mm oil column;

[0063] (f) After the carbonitriding furnace is cooled to below 700°C, the carbon supply is stopped, the metal plate is taken out and placed in oil for rapid cooling.

[0064] The ultrasonic rolling post-processing method in step S4 is: using a processing platform including a vertical machining center and an ultrasonic surface rolling device, the ball moves 3mm at both ends of the metal plate, the downward pressure is selected to be 1mm, and oil lubrication is continuously performed during the ultrasonic rolling process. The adjustable parameters of the ultrasonic surface rolling device are: feed speed, static pressure, rolling times, step distance, amplitude, and a 5-factor 4-level ultrasonic rolling orthogonal experiment is designed according to the value range of each parameter, wherein:

[0065] Rolling times (times): 3, 4, 5, 6;

[0066] Amplitude (μm): 6, 8, 10, 12;

[0067] Static pressure (N): 400, 500, 600, 700;

[0068] Feed speed (m / min): 0.8, 1.0, 1.2, 1.4;

[0069] Step distance (mm): 0.15, 0.20, 0.25, 0.30.

[0070] In addition, the synergistic relationship between the diameter of the ultrasonic rolling head and the contact force was studied for the metal fixed plate of the automated agricultural seeder.

[0071] According to Hertz's elastic contact theory, when the applied pressure is the same, the larger the ball diameter, the larger the contact radius, and the machined surface will become smoother. Smaller ball sizes will cause more local deformations. According to the reasonable range of each parameter value, a 4-factor 3-level ultrasonic rolling orthogonal experiment was designed, as shown in Table 1, to explore the effects of spindle speed, contact force, feed speed, and pass on hardness and surface roughness. Through the analysis of experimental data, it can be seen that contact force is the most important parameter affecting hardness and surface roughness. Therefore, for surface morphology and performance, the process range in which the indenter diameter and contact force work together is preferably: the indenter diameter is 12-15mm, the contact force is 17.5-20MPa, the surface roughness is 0.04-0.06μm, and the surface hardness is 720-840HV.

[0072]

[0073] Table 1: Ultrasonic rolling processing orthogonal test table

[0074] Example 1

[0075] A composite surface treatment method for a metal plate of an automated agricultural seed drill comprises the following steps:

[0076] S1: Pretreatment: the metal plate is a 403 stainless steel plate with a length of 10 mm, a width of 10 mm, and a height of 2 mm. Use 500-grit sandpaper to grind the surface of the metal plate to remove oil and rust on the surface of the metal plate until the surface of the metal plate has a frosted pattern with scratches in the same direction. Then, add anhydrous ethanol to the surface of the metal plate, wash it with anhydrous ethanol, and then use a hair dryer to dry the surface of the metal plate for later use;

[0077] S2: Shot peening, using conventional hardness cast steel shot as the shot peening medium, using a pneumatic shot peening machine to shot peen the metal plate, the spray distance is 190mm, the shot peening air pressure is 3Bar, the shot peening flow rate is 10kg / min, the shot peening coverage is 200%, and the shot peening time is 95 seconds. After shot peening, the surface of the metal plate is cleaned and dried for use;

[0078] Using the Almen test piece method, the shot peening intensity of the metal plate surface was obtained through experiments, and the shot peening time was 45 seconds; wherein, the equation of the arc height value-time curve used in the Almen test piece method is as follows:

[0079] f=a(1-e-bt)

[0080] Where: f is the arc height value; t is the shot peening time; a is the equation constant, representing the saturation level of the arc height value after a sufficiently long shot peening time; b is the equation constant, which is related to the rate of the shot peening process and affects the speed at which the arc height value reaches the saturation state; e is the base of the natural logarithm, which is approximately equal to 2.71828.

[0081] The Almen test piece method is used to calculate the residual compressive stress and residual compressive stress depth of the metal plate surface after shot peening. The formula used is as follows:

[0082]

[0083] Where: f is the arc height; h is the thickness of the test piece; E is the elastic modulus; v is the Poisson coefficient; σ mr is the average residual compressive stress in the strengthening layer; δr is the residual compressive stress depth; a is the equation constant, representing the intensity of the shot peening process.

[0084] S3: Ultrasonic cleaning: put the metal plate into anhydrous ethanol for ultrasonic cleaning for 20 minutes and then dry it.

[0085] Example 2

[0086] A composite surface treatment method for a metal plate of an automated agricultural seed drill comprises the following steps:

[0087] S1: Pretreatment: the metal plate is a 403 stainless steel plate with a length of 10 mm, a width of 10 mm, and a height of 2 mm. Use 500-grit sandpaper to grind the surface of the metal plate to remove oil and rust on the surface of the metal plate until the surface of the metal plate has a frosted pattern with scratches in the same direction. Then, add anhydrous ethanol to the surface of the metal plate, wash it with anhydrous ethanol, and then use a hair dryer to dry the surface of the metal plate for later use;

[0088] S2: Shot peening, using conventional hardness cast steel shot as the shot peening medium, using a pneumatic shot peening machine to shot peen the metal plate, the spray distance is 190mm, the shot peening air pressure is 3Bar, the shot peening flow rate is 10kg / min, the shot peening coverage is 200%, and the shot peening time is 95 seconds. After shot peening, the surface of the metal plate is cleaned and dried for use;

[0089] Using the Almen test piece method, the shot peening intensity of the metal plate surface was obtained through experiments, and the shot peening time was 45 seconds; wherein, the equation of the arc height value-time curve used in the Almen test piece method is as follows:

[0090] f=a(1-e-bt)

[0091] In the formula, f is the arc height, t is the shot peening time, and a and b are equation constants;

[0092] The Almen test piece method is used to calculate the residual compressive stress and residual compressive stress depth of the metal plate surface after shot peening. The formula used is as follows:

[0093]

[0094] Where: f is the arc height; h is the thickness of the test piece; E is the elastic modulus; v is the Poisson coefficient; σ mr is the average residual compressive stress in the strengthening layer; δr is the residual compressive stress depth; a is the equation constant, representing the intensity of the shot peening process.

[0095] S3: High-temperature carbonitriding: put the workpiece into a gas carburizing furnace for carbonitriding. After carbonitriding is completed, the temperature is lowered to below 700°C, the carbon supply is stopped, the metal plate is taken out, and put into oil for rapid cooling;

[0096] The high temperature carbonitriding steps are as follows:

[0097] (a) preparing an osmotic mixture: selecting 30% ammonia and 70% methanol as co-osmotic agents, and adding carbon tetrachloride and titanium chloride in a weight ratio of 3:1 into the methanol as activators to prepare an osmotic mixture;

[0098] (b) Exhaust stage: The carbonitriding furnace is preheated, the heating rate is maintained at 12°C / min, the dripping rate of the catalyst mixture is 85 drops / min, the methanol flux is 120L / h, the time is 30min, and the furnace temperature is 350°C at this time;

[0099] (c) Strong infiltration stage: the dripping rate of the infiltration mixture is 65 drops / min, the methanol flux is 400L / h, the furnace pressure is maintained at 35mm oil column, the furnace temperature is continuously increased, the heating rate is maintained at 15℃ / min, the time is 2 hours, and the furnace temperature is about 800℃;

[0100] (d) Heating and diffusion stage: the dripping rate of the catalytic mixture was 52 drops / min, the methanol flux was 550 L / h, the furnace pressure was increased to 60 mm oil column, the furnace temperature was kept stable at 900 °C for 16 hours, and nitrogen was introduced as a protective gas;

[0101] (e) Cooling stage: stop dripping the catalytic mixture, turn off the power, stop heating, maintain the methanol flux at 600 L / h, and keep the furnace pressure at 60 mm oil column;

[0102] (f) After the carbonitriding furnace is cooled to below 700°C, the carbon supply is stopped, the metal plate is taken out and placed in oil for rapid cooling;

[0103] S4: Ultrasonic cleaning: put the metal plate into anhydrous ethanol for ultrasonic cleaning for 20 minutes and then dry it.

[0104] Example 3

[0105] A composite surface treatment method for a metal plate of an automated agricultural seed drill comprises the following steps:

[0106] S1: Pretreatment: the metal plate is a 403 stainless steel plate with a length of 10 mm, a width of 10 mm, and a height of 2 mm. Use 500-grit sandpaper to grind the surface of the metal plate to remove oil and rust on the surface of the metal plate until the surface of the metal plate has a frosted pattern with scratches in the same direction. Then, add anhydrous ethanol to the surface of the metal plate, wash it with anhydrous ethanol, and then use a hair dryer to dry the surface of the metal plate for later use;

[0107] S2: Shot peening, using conventional hardness cast steel shot as the shot peening medium, using a pneumatic shot peening machine to shot peen the metal plate, the spray distance is 190mm, the shot peening air pressure is 3Bar, the shot peening flow rate is 10kg / min, the shot peening coverage is 200%, and the shot peening time is 95 seconds. After shot peening, the surface of the metal plate is cleaned and dried for use;

[0108] Using the Almen test piece method, the shot peening intensity of the metal plate surface was obtained through experiments, and the shot peening time was 45 seconds; wherein, the equation of the arc height value-time curve used in the Almen test piece method is as follows:

[0109] f=a(1-e-bt)

[0110] In the formula, f is the arc height, t is the shot peening time, and a and b are equation constants;

[0111] The Almen test piece method is used to calculate the residual compressive stress and residual compressive stress depth of the metal plate surface after shot peening. The formula used is as follows:

[0112]

[0113] Where: f is the arc height; h is the thickness of the test piece; E is the elastic modulus; v is the Poisson coefficient; σ mr is the average residual compressive stress in the strengthening layer; δr is the residual compressive stress depth; a is the equation constant, representing the intensity of the shot peening process.

[0114] S3: High-temperature carbonitriding: put the workpiece into a gas carburizing furnace for carbonitriding. After carbonitriding is completed, the temperature is lowered to below 700°C, the carbon supply is stopped, the metal plate is taken out, and put into oil for rapid cooling;

[0115] The high temperature carbonitriding steps are as follows:

[0116] (a) preparing an osmotic mixture: selecting 30% ammonia and 70% methanol as co-osmotic agents, and adding carbon tetrachloride and titanium chloride in a weight ratio of 3:1 into the methanol as activators to prepare an osmotic mixture;

[0117] (b) Exhaust stage: The carbonitriding furnace is preheated, and the heating rate is maintained at 10-15°C / min. At the same time, the dripping rate of the catalytic mixture is 85 drops / min, the methanol flux is 120L / h, and the time is 30min. At this time, the temperature in the furnace is 350°C;

[0118] (c) Strong infiltration stage: the dripping rate of the infiltration mixture is 65 drops / min, the methanol flux is 400L / h, the furnace pressure is maintained at 35mm oil column, the furnace temperature is continuously increased, the heating rate is maintained at 15℃ / min, the time is 2 hours, and the furnace temperature is about 800℃;

[0119] (d) Heating and diffusion stage: the dripping rate of the catalytic mixture was 52 drops / min, the methanol flux was 550 L / h, the furnace pressure was increased to 60 mm oil column, the furnace temperature was kept stable at 900 °C for 16 hours, and nitrogen was introduced as a protective gas;

[0120] (e) Cooling stage: stop dripping the catalytic mixture, turn off the power, stop heating, maintain the methanol flux at 600 L / h, and keep the furnace pressure at 60 mm oil column;

[0121] (f) After the carbonitriding furnace is cooled to below 700°C, the carbon supply is stopped, the metal plate is taken out and placed in oil for rapid cooling;

[0122] S4: ultrasonic rolling post-processing, using a processing platform including a vertical machining center and an ultrasonic surface rolling device to process the surface of the metal plate;

[0123] The ultrasonic rolling post-processing method is: using a processing platform including a vertical machining center and an ultrasonic surface rolling device, the ball moves 3mm at both ends of the metal plate, the downward pressure is selected to be 1mm, and oil lubrication is continuously performed during the ultrasonic rolling process. The adjustable parameters of the ultrasonic surface rolling device are: feed speed, static pressure, rolling times, step distance, and amplitude, among which: the rolling times are 5 times; the amplitude is 10μm; the static pressure is 600N; the feed speed is 1.2m / min; the step distance is 0.25mm;

[0124] S5: Ultrasonic cleaning: put the metal plate into anhydrous ethanol for ultrasonic cleaning for 20 minutes and then dry it.

[0125] Through the comparative analysis of the performance and morphology of Examples 1-3, it can be seen that the surface hardness and service life of the workpiece processed by the complete composite surface treatment process in Example 3 are significantly improved compared with the workpieces obtained in Examples 1 and 2. In addition, according to the metallographic microscopic image, it can be found that the workpiece processed by the complete composite surface treatment process in Example 3 has a thicker infiltration layer and a more uniform surface morphology distribution.

[0126] Technical features not described in the present invention can be implemented by existing technologies and will not be described in detail here. The present invention is not limited to the above specific embodiments, and changes, modifications, additions or substitutions made by ordinary technicians in the field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A composite surface treatment method for a metal plate of an automated agricultural seeder. Its characteristics are: It includes the following steps: S1: Pretreatment: grinding the surface of the metal plate to remove oil and rust from the surface of the metal plate, cleaning it with anhydrous ethanol, and drying it for later use; S2: Shot peening, using cast steel shots of conventional hardness as shot peening media to shot peen the metal plate, clean the surface after treatment, and dry it for later use; S3: High-temperature carbonitriding: put the workpiece into a gas carburizing furnace for carbonitriding. After carbonitriding is completed, the temperature is lowered to below 700°C, the carbon supply is stopped, the metal plate is taken out, and put into oil for rapid cooling; S4: ultrasonic rolling post-processing, using a processing platform including a vertical machining center and an ultrasonic surface rolling device to process the surface of the metal plate; S5: Ultrasonic cleaning: put the metal plate into anhydrous ethanol for ultrasonic cleaning for 15-30 minutes, and then dry it.

2. The composite surface treatment method of the metal plate of the automated agricultural seeder according to claim 1, Its characteristics are: In step S2, the residual compressive stress and residual compressive stress depth of the metal platen surface after shot peening are calculated using the Almen test piece method, and the formula used is as follows: Where: f is the arc height; h is the thickness of the test piece; E is the elastic modulus; v is the Poisson coefficient; σ mr is the average residual compressive stress in the strengthening layer; δr is the residual compressive stress depth; a is the equation constant, representing the intensity of the shot peening process.

3. The composite surface treatment method of the metal plate of the automated agricultural seeder according to claim 1 or 2, Its characteristics are: The high temperature carbonitriding step in step S3 is as follows: (a) preparing an osmotic mixture: selecting 30% ammonia and 70% methanol as co-osmotic agents, and adding carbon tetrachloride and titanium chloride in a weight ratio of 3:1-5:1 to the methanol as activators to prepare an osmotic mixture; (b) Exhaust stage: The carbonitriding furnace is preheated, and the heating rate is maintained at 10-15°C / min. At the same time, the dripping amount of the catalytic mixture is 80-100 drops / min, the methanol flux is 100-150L / h, and the time is 30min. At this time, the temperature in the furnace is between 300-450°C; (c) Strong infiltration stage: the dripping rate of the infiltration mixture is 60-65 drops / min, the methanol flux is 400-450L / h, the furnace pressure is maintained at 30-40mm oil column, the furnace temperature is continuously increased, the heating rate is maintained at 10-15℃ / min, the time is 1-3 hours, and the furnace temperature is about 600-900℃; (d) Heating and diffusion stage: the dripping rate of the catalytic mixture is 50-55 drops / min, the methanol flux is 500-600 L / h, the furnace pressure is increased to 50-70 mm oil column, the furnace temperature is stably maintained at 850-950 ° C, and the temperature is kept for 15-17 hours, while nitrogen is introduced as a protective gas; (e) Cooling stage: stop dripping the catalytic mixture, turn off the power, stop heating, maintain the methanol flux at 600 L / h, and keep the furnace pressure at 60 mm oil column; (f) After the carbonitriding furnace is cooled to below 700°C, the carbon supply is stopped, the metal plate is taken out and placed in oil for rapid cooling.

4. The composite surface treatment method of the metal plate of the automated agricultural seeder according to claim 3, Its characteristics are: The ultrasonic rolling post-processing method in step S4 is: using a processing platform including a vertical machining center and an ultrasonic surface rolling device, the ball moves 3mm at both ends of the metal plate, the downward pressure is selected to be 1mm, and oil lubrication is continuously performed during the ultrasonic rolling process.

5. The composite surface treatment method of the metal plate of the automated agricultural seeder according to claim 4, Its characteristics are: The adjustable parameters of the ultrasonic surface rolling device are: feed speed, static pressure, rolling times, step distance, and amplitude. A 5-factor 4-level ultrasonic rolling processing orthogonal experiment is designed according to the value range of each parameter, wherein: Rolling times (times): 3, 4, 5, 6; Amplitude (μm): 6, 8, 10, 12; Static pressure (N): 400, 500, 600, 700; Feed speed (m / min): 0.8, 1.0, 1.2, 1.4; Step distance (mm): 0.15, 0.20, 0.25, 0.

30.

6. The composite surface treatment method of the metal plate of the automated agricultural seeder according to claim 5, Its characteristics are: In step S2, the shot peening intensity of the metal plate surface is obtained by experiment using the Almen test piece method, and the shot peening time is 45-50 seconds; wherein the arc height value-time curve equation used in the Almen test piece method is as follows: f=a(1-e-bt) Where: f is the arc height value; t is the shot peening time; a is the equation constant, representing the saturation level of the arc height value after a sufficiently long shot peening time; b is the equation constant, which is related to the rate of the shot peening process and affects the speed at which the arc height value reaches the saturation state; e is the base of the natural logarithm, which is approximately equal to 2.71828.

7. The composite surface treatment method of the metal plate of the automated agricultural seeder according to claim 6, Its characteristics are: In the step S2, a pneumatic shot peening machine is used for shot peening, the spraying distance is 190 mm, the shot peening air pressure is 3 Bar, the shot peening flow rate is 10 kg / min, the shot peening coverage is 200%, and the shot peening time is 90-100 seconds.

8. The composite surface treatment method of the metal plate of the automated agricultural seeder according to claim 7, Its characteristics are: In the step S1, 500-grit sandpaper is selected to grind the surface of the metal plate until a frosted sample with scratches in a consistent direction appears on the surface of the metal plate, anhydrous ethanol is dripped onto the surface of the metal plate, and then the surface of the metal plate is dried with a hair dryer.

9. The composite surface treatment method of the metal plate of the automated agricultural seeder according to claim 8, Its characteristics are: The metal plate is a 403 stainless steel plate with a length of 10 mm, a width of 10 mm, and a height of 2 mm.

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