Heat treatment method for vacuum coating of high-carbon chromium bearing steel

Abstract

The invention belongs to the technical field of metal surface heat treatment, and particularly relates to a high-carbon-chromium bearing steel vacuum coating heat treatment method. And a vacuum negative pressure environment is established to provide necessary process guarantee conditions for SV, so that the purity of the environment in the vanadinizing process is ensured. In the vanadizing process, ultrasonic waves are additionally added to provide extra energy for a coating medium, meanwhile, the diffusion resistance of the medium is reduced, the vanadizing speed is increased, and finally through continuous multiple SV treatment verification on the GCr15 pin shaft, the pin shaft with a uniform infiltrated layer and good compactness and adhesive force is obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal surface heat treatment, and particularly relates to a vacuum cladding heat treatment method for high-carbon chromium bearing steel. Background Art

[0002] In recent years, with the rapid development of the manufacturing industry, the requirements for chains in industry have become increasingly high. Among them, the wear resistance of the chain is a key requirement, and the wear resistance of the pin shaft is closely related to the wear resistance of the chain. In order to improve the wear resistance of the pin shaft surface, vanadium is infiltrated on the pin shaft surface. There are three types of vanadium infiltration methods: solid method, liquid method, and gas method. However, the existing solid vanadium infiltration process has the following problems:

[0003] 1. Low production efficiency and uneven infiltration layer

[0004] 2. It is difficult to be used for the processing of large quantities of high-precision parts. Summary of the Invention

[0005] The present invention discloses a vacuum cladding heat treatment method for high-carbon chromium bearing steel. By establishing a vacuum negative pressure environment, necessary process guarantee conditions are provided for SV (vanadium infiltration) to ensure the purity of the environment during the vanadium infiltration process. During the vanadium infiltration process, the intervention of ultrasonic waves is added to provide additional energy for the cladding medium while reducing the diffusion resistance of the medium and accelerating the vanadium infiltration speed. Finally, through the verification of continuous multiple SV treatments on GCr15 pin shafts, pin shafts with uniform, dense, and good adhesion infiltration layers are obtained.

[0006] To achieve the above object, the technical solution of the present invention is:

[0007] A vacuum cladding heat treatment method for high-carbon chromium bearing steel, comprising the following steps:

[0008] (1) Detect the vacuum cladding equipment to ensure that the equipment is in normal working condition;

[0009] (2) Start the vacuum cladding equipment, rotate the furnace chamber, mix the cladding medium powder with the pin shaft, and add them into the furnace chamber in multiple times;

[0010] (3) The vacuum cladding equipment starts the temperature rising program, and gradually raises the temperature in the furnace chamber to dry the cladding medium powder;

[0011] (4) After drying the set test piece, purge the furnace cavity with inert gas to increase the stability of the pin shaft surface and reduce the contact between the surface and oxygen;

[0012] (5) Close the furnace mouth and start the mixing mode. During the mixing process, the furnace chamber makes a reciprocating motion of tilting and leveling;

[0013] (6) Evacuate to avoid the residual oxygen in the furnace chamber;

[0014] (7) Fill the furnace chamber with inert gas and discharge the waste gas;

[0015] (8) Evacuate the furnace chamber again;

[0016] (9) Fill with inert gas again and discharge the waste gas until the pressure in the furnace chamber returns to 0 Bar;

[0017] (10) Start slowly heating up in combination with ultrasonic metal infiltration;

[0018] (11) Start the air-cooling program to cool down the furnace chamber;

[0019] (12) Discharge the materials and separate the pin shafts from the cladding medium by screening.

[0020] Preferably, in step (2), the mass ratio of the cladding medium powder to the pin shaft is 3:5.

[0021] Preferably, in steps (6) and (8), the vacuum degree in the furnace chamber is made to reach -0.7 Bar to -0.6 Bar by evacuation.

[0022] Preferably, in step (10), when the temperature in the furnace chamber reaches 700 - 900 °C and the pressure is between 0.4 Bar - 0.5 Bar, hold for 1 hour, then start to relieve the pressure to 0.25 Bar, then continue to heat up to 900 - 1000 °C, and keep the temperature for 5 hours; during the process of heating up to 900 - 1000 °C, when the temperature is 800 °C, start the ultrasonic emission device, and stop emitting ultrasonic waves after working for 6 hours.

[0023] Preferably, in step (11), cool down the furnace chamber to 70 ± 10 °C.

[0024] Preferably, in steps (2), (3) and (10), the rotation speed of the furnace liner is 1 r / min before the furnace chamber temperature reaches 850 °C, 3 r / min from 850 °C to before cooling down, and 2.5 r / min during the cooling stage.

[0025] The beneficial effects of a vacuum cladding heat treatment method for high-carbon chromium bearing steel of the present invention are as follows: The present invention overcomes the problems of low production efficiency, uneven infiltration layer and difficulty in being used for the processing of large quantities of high-precision parts in the existing process, and has the following advantages:

[0026] (1) The single-sided infiltration layer of the pin shaft reaches 0.025 - 0.035 mm, obtaining a sufficient infiltration layer thickness, leaving enough margin for subsequent polishing and further laying a solid foundation for the wear resistance of the pin shaft.

[0027] (2) The cavitation effect of ultrasonic waves can disperse the cladding medium more evenly on the surface of the workpiece, ensuring that all parts of the workpiece can come into full contact with the vanadium permeating agent, making the permeated layer more uniform. The converter can also make the contact between the medium and the pin shaft more uniform, which greatly improves the overall consistency of the pin shaft after permeation.

[0028] (3) The surface hardness of the pin shaft is greatly increased, and the surface hardness of the pin shaft is 2400HV0.1 - 2700HV0.1.

[0029] (4) Ultrasonic waves accelerate the speed of vanadium permeation. The cavitation effect of ultrasonic waves provides additional energy for the cladding medium, reduces the activation energy required for medium diffusion, and at the same time ultrasonic waves reduce the diffusion resistance of the medium, accelerating the speed of vanadium permeation. Description of the Drawings

[0030] Figure 1 It is a schematic diagram of the process temperature - pressure - time curve.

[0031] Figure 2 It is a metallographic structure and permeated layer diagram. Detailed Implementation Modes

[0032] The following description is only for the preferred embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0033] The following embodiments can be understood as separately expressing a part of the local structure or method of the present invention, or can also be understood as the embodiments combined with each other to explain the connotation of the structure or method of a larger scope of the present invention.

[0034] Example 1

[0035] A vacuum cladding heat treatment method for high - carbon chromium bearing steel, as Figure 1 shown, includes the following steps:

[0036] (1) Detect the vacuum cladding equipment to ensure that the equipment is in normal working condition; usually including airtightness and smoothness detection: for the special equipment used in the vacuum SV cladding hardening treatment technology, parameters such as temperature, pressure, time, and rotation speed are set by process personnel and input into the program to achieve automatic control; before the equipment operates, it is necessary to detect the airtightness and smoothness of the pipeline and the heating furnace to prevent damage to the SV permeating agent due to unqualified vacuum degree and oxidation reaction with air. Usually, inflation and pressure maintenance for 6 hours are used to observe the change of the pressure value (generally not exceeding 0.02Bar) to judge the airtightness of the heating furnace and the pipeline;

[0037] (2) Start the vacuum cladding equipment, rotate the furnace chamber, and mix the cladding medium powder and the pin shaft and add them into the furnace chamber in multiple batches;

[0038] (3) The vacuum cladding equipment starts the heating-up procedure to gradually dry the cladding medium powder in the furnace chamber.

[0039] (4) After drying the set test piece, purge the furnace chamber with inert gas to increase the surface stability of the pin shaft and reduce the contact between the surface and oxygen.

[0040] (5) Close the furnace opening and start the mixing mode. During the mixing process, the furnace liner makes reciprocating motions of tilting and leveling.

[0041] (6) Avoid residual oxygen in the furnace chamber by vacuum pumping.

[0042] (7) Fill the furnace chamber with inert gas and discharge the waste gas.

[0043] (8) Vacuum pump the furnace chamber again.

[0044] (9) Fill with inert gas again and discharge the waste gas until the pressure in the furnace chamber returns to 0 Bar.

[0045] (10) Start slow heating combined with ultrasonic metal infiltration.

[0046] (11) Start the air-cooling procedure to cool down the furnace chamber.

[0047] (12) Discharge the materials and screen and separate the pin shaft from the cladding medium.

[0048] Example 2

[0049] Based on Example 1, this example discloses that in step (2), the mass ratio of the cladding medium powder to the pin shaft is 3:5.

[0050] Example 3

[0051] Based on Example 1, this example discloses that:

[0052] In steps (6) and (8), the vacuum degree in the furnace chamber reaches -0.7 Bar to -0.6 Bar by vacuum pumping.

[0053] Example 4

[0054] Based on Example 1, this example discloses that:

[0055] In step (10), when the temperature in the furnace chamber reaches 700 - 900 degrees Celsius and the pressure is between 0.4 Bar and 0.5 Bar, hold for 1 hour, then start to release pressure to 0.25 Bar, and then continue to heat up to 900 - 1000 °C and keep it warm for 5 hours; during the process of heating up to 900 - 1000 °C, when the temperature is 800 degrees Celsius, start the ultrasonic emission device and stop emitting ultrasonic waves after working for 6 hours.

[0056] Example 5

[0057] Based on Example 1, this example discloses:

[0058] In step (11), the temperature in the furnace is reduced to 70 ± 10 °C.

[0059] Example 6

[0060] Based on Example 1, this example discloses:

[0061] In steps (2), (3), and (10), the rotation speed of the furnace liner is 1 r / min before the furnace temperature reaches 850 °C, 3 r / min from 850 °C to before cooling, and 2.5 r / min during the cooling stage.

[0062] Example 7

[0063] First, the vacuum cladding equipment is inflated and pressurized for 6 hours to observe the change in pressure value (generally not exceeding 0.02 Bar) to judge the sealing performance of the heating furnace and the pipeline.

[0064] First step: Place 60 Kg of the required SV powdered cladding medium in the stirrer, stir evenly, and pour it into the heating furnace in multiple batches with 100 kg of workpieces (pin shafts), and start the rotation of the furnace liner;

[0065] Second step: Start the program heating, raise the temperature outside the furnace to 200 - 250 °C, control the temperature inside the furnace to reach 170 °C ± 5 °C, keep it for 30 minutes, then stop heating and close the furnace mouth;

[0066] Third step: First vacuumize, control the pressure inside the furnace to be between -0.7 Bar and -0.6 Bar and keep it pressurized for 25 minutes;

[0067] Fourth step: The program automatically executes filling argon gas into the furnace and starts the exhaust valve to exhaust waste gas, and runs for 20 minutes;

[0068] Fifth step: Second vacuumize again, control the pressure inside the furnace to be between -0.7 Bar and -0.6 Bar and keep it pressurized for 20 minutes;

[0069] Sixth step: Fill argon gas again to make the pressure inside the furnace return to 0 Bar and keep it, and exhaust waste gas continuously for 20 minutes;

[0070] Step 7: Continue heating. Slowly raise the temperature outside the furnace to 980 °C within 6 hours, and slowly raise the temperature inside the furnace to 700 - 900 °C. Keep the pressure inside the furnace at 0.4 - 0.5 Bar for 1 hour, then start to relieve the pressure to 0.25 Bar and continue to raise the temperature to 900 - 1000 °C, and keep the temperature for 5 hours. When the temperature reaches 800 °C, start the ultrasonic emission device and let it work for 6 hours (adjust the frequency of the generator to 70 - 90 KHZ, and the duty cycle to 70%), then stop working.

[0071] Step 8: Start air cooling and cool down to 70 ± 10 °C within 5 hours.

[0072] Step 9: Open the furnace mouth to pour out the material, and screen and separate the cladding medium from the pin shaft.

[0073] Example 8

[0074] The mixing mode described above runs through steps (5)-(12), and the specific process is as follows:

[0075] After closing the furnace mouth for 5 minutes, the included angle between the axis of the furnace mouth and the ground reaches 30 - 35°, keep it for 5 minutes, then the furnace mouth returns to be parallel to the ground, and then keep it for 5 minutes, and then start to repeat the previous action. When the number of reciprocating motions reaches 35 times, the included angle between the axis of the furnace mouth and the ground is 30 - 35° again, keep it for 5 hours, then the furnace mouth is parallel to the ground again. After 5 minutes, continue the reciprocating motion. After 27 reciprocations, end the reciprocating motion and wait for discharging. This tilting reciprocating motion of the furnace body further prevents the shaft materials and the penetrant from stacking in the furnace body, resulting in uneven penetration.

[0076] Example 9

[0077] Taking the pin shaft made of GCr15 bearing steel, with a length of 8.20 mm and a diameter of 2.37 mm (+0.005, 0) as an example, the implementation effect of the present invention is described as follows: As shown in the following table, the penetration layer data of the pin shaft is given (for the metallographic diagram, see Figure 2 ).

[0078] Penetration layer data table of the pin shaft

[0079]

[0080] To sum up, through the process provided by the present invention, the following several practical effects and advantages can be obtained:

[0081] (1) The single-sided penetration layer of the pin shaft reaches 0.025 - 0.035 mm, obtaining a sufficient penetration layer thickness, leaving enough margin for subsequent polishing and further laying a solid foundation for the wear resistance of the pin shaft.

[0082] (2) The cavitation effect of ultrasonic waves can disperse the cladding medium more evenly on the surface of the workpiece, ensuring that all parts of the workpiece can come into full contact with the vanadiumizing agent, making the penetration layer more uniform. The converter can also make the contact between the medium and the pin shaft more uniform, greatly improving the overall consistency of the pin shaft after vanadiumizing.

[0083] (3) The surface hardness of the pin shaft is greatly increased, and the surface hardness of the pin shaft is 2400HV0.1 - 2700HV0.1.

[0084] (4) Ultrasonic waves accelerate the speed of vanadiumizing. The cavitation effect of ultrasonic waves provides additional energy for the cladding medium, reduces the activation energy required for medium diffusion, and at the same time, ultrasonic waves reduce the diffusion resistance of the medium, thus accelerating the speed of vanadiumizing.

[0085] It should be noted that:

[0086] The vacuum cladding equipment of the present invention can select commercially available products (Example of commercially available vacuum cladding equipment: Name: Heat treatment industrial furnace, Model: ZY - 90 - 10) or products capable of realizing relevant functions recorded in the patent library. Of course, it can also be manufactured according to the process steps of the present invention. For example, a rotatable furnace chamber is manufactured, a heating device is arranged between the furnace chamber and the equipment housing to heat the furnace chamber; an electric door is arranged at one end of the furnace chamber opening, and a blow - pipe with a solenoid valve is penetrated through the electric door to connect an inert gas pipeline to blow inert gas into the furnace chamber, and a pressure - relief pipe is connected to the outer wall of the furnace chamber; a temperature sensor and an air pressure sensor (or the furnace chamber is connected with a pressure gauge for detecting the air pressure in the furnace chamber) are arranged on the inner wall of the furnace chamber to monitor the temperature and air pressure in the furnace chamber in real - time. The temperature sensor and the pressure sensor are respectively connected to a control room on the outer wall of one end of the furnace chamber away from the electric door through wires. A controller is arranged in the control room, and the pressure and temperature data are transmitted to the controller. The controller transmits the pressure and temperature signals to the human - machine interaction device on the equipment housing in real - time. Since the control room is located at one end of the furnace chamber with a heat - insulation layer, overheating or wire entanglement will not occur. The ultrasonic device is arranged at a position on the inner wall of the housing opposite to the furnace chamber for easy operation when ultrasonic intervention is required. The base of the whole equipment is set to be an inclined structure. One end of the base can be hinged to the ground, and a cylinder is connected to the side of the equipment away from the hinge axis. Both ends of the cylinder are respectively hinged to the housing and the ground, and the inclination and leveling of the whole equipment are realized through the expansion and contraction of the cylinder.

Claims

1. A vacuum cladding heat treatment method for high-carbon chromium bearing steel, characterized by the following steps: (1) Detect the vacuum cladding equipment to ensure that the equipment is in normal working condition; (2) Start the vacuum cladding equipment, rotate the furnace chamber, mix the cladding medium powder with the pin shaft and add them into the furnace chamber in multiple batches; (3) The vacuum cladding equipment starts the heating-up program, and gradually heats up inside the furnace chamber to dry the cladding medium powder; (4) After drying the set test piece, purge the furnace cavity with inert gas to increase the surface stability of the pin shaft and reduce the contact between the surface and oxygen; (5) Close the furnace opening and start the mixing mode. During the mixing process, the furnace chamber makes reciprocating motions of tilting and restoring to the flat state; (6) Avoid residual oxygen in the furnace chamber by evacuating; (7) Fill the furnace chamber with inert gas and discharge the waste gas; (8) Evacuate the furnace chamber again; (9) Fill with inert gas again and discharge the waste gas until the pressure in the furnace chamber returns to 0 Bar; (10) Start to slowly heat up and combine with ultrasonic metal infiltration; (11) Start the air-cooling program to cool down the furnace chamber; (12) Discharge the materials, and screen and separate the pin shaft from the cladding medium.

2. The vacuum cladding heat treatment method for high-carbon chromium bearing steel as described in claim 1, characterized in that, In the step (2) described above, the mass ratio of the cladding medium powder to the pin shaft is 3:

5.

3. A vacuum cladding heat treatment method for high-carbon chromium bearing steel as described in claim 1, characterized in that, In the steps (6) and (8) described above, evacuate to make the vacuum degree in the furnace chamber reach -0.7 Bar to -0.6 Bar.

4. A vacuum cladding heat treatment method for high-carbon chromium bearing steel according to claim 1, characterized in that, In the step (10) described above, when the temperature in the furnace chamber reaches 700 - 900 °C and the pressure is between 0.4 Bar - 0.5 Bar, hold for 1 hour, then start to relieve the pressure to 0.25 Bar, then continue to heat up to 900 - 1000 °C, and keep the temperature for 5 hours; during the process of heating up to 900 - 1000 °C, when the temperature is 800 °C, start the ultrasonic emission device, and stop emitting ultrasonic waves after working for 6 hours.

5. A vacuum cladding heat treatment method for high-carbon chromium bearing steel according to claim 1, characterized in that, In the step (11) described above, cool down the furnace chamber to 70 ± 10 °C.

6. A vacuum cladding heat treatment method for high-carbon chromium bearing steel according to claim 1, characterized in that, In the steps (2), (3), and (10) described above, the rotation speed of the furnace chamber is 1 r / min before the furnace chamber temperature reaches 850 °C, 3 r / min from 850 °C to before cooling down, and 2.5 r / min during the cooling stage.

7. A vacuum cladding heat treatment method for high-carbon chromium bearing steel as described in claim 1, characterized in that, The mixing mode runs through steps (5) - (12), and the specific steps are as follows: 5 minutes after closing the furnace opening, the included angle between the axis of the furnace opening and the ground reaches 30 - 35 °, keep it for 5 minutes and then the furnace opening returns to be parallel to the ground, then keep it for 5 minutes and then start to repeat the previous actions. When the number of reciprocating motions reaches 35 times, the included angle between the axis of the furnace opening and the ground is 30 - 35 ° again, keep it for 5 hours and then the furnace opening is parallel to the ground again. After 5 minutes, continue the reciprocating motion. After 27 reciprocating motions, end the reciprocating motion and wait for discharging the materials.

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