GCr15 steel workpiece surface strengthening method, GCr15 steel workpiece surface strengthening treatment equipment and workpiece strengthened by GCr15 steel workpiece surface strengthening method

Abstract

The invention discloses a GCr15 steel workpiece surface strengthening method, treatment equipment and a workpiece strengthened through the method. The method comprises the steps that a GCr15 steel workpiece is placed in an ammonia gas environment; a high-energy laser beam is used for carrying out laser quenching treatment on a GCr15 steel workpiece, ammonia gas around a quenching area is heated and decomposed under the action of high-energy laser, active nitrogen molecules are generated after the ammonia gas is decomposed, energy is absorbed, the cooling speed of the bearing is increased, and a laser quenching layer is formed; and meanwhile, active nitrogen molecules are diffused on the metal surface of a quenching area and permeate into the GCr15 steel workpiece to form a nitriding layer, so that double strengthening of laser quenching and nitriding is realized on the surface of the bearing track.

Description

Technical Field

[0001] The invention belongs to the field of surface strengthening of GCr15 steel workpieces, and more specifically, relates to a surface strengthening method and processing equipment for a GCr15 steel workpiece and a workpiece strengthened by the method. Background Art

[0002] GCr15 steel workpiece is a representative steel type of high carbon chromium bearing steel. After quenching and tempering, it has high and uniform hardness, high wear resistance, high contact fatigue resistance and good hot workability. It is mainly used to manufacture steel balls, rollers and sleeves on transmission shafts of internal combustion engines, electric locomotives, machine tools, tractors, rolling equipment, drilling machines, railway vehicles and mining machinery. However, with the increasingly high performance requirements of drive motor bearings, robot bearings and precision machine tool bearings, the hardness, wear resistance, toughness, finish and dimensional accuracy after traditional oil quenching treatment are difficult to meet the requirements.

[0003] Nitriding is a heat treatment method to improve the surface performance of bearings. The nitriding process needs to be carried out in a high-temperature furnace. It faces problems such as long cycle, high energy consumption, large deformation, and low degree of automation, which restricts the further improvement of bearing life and reliability. Conventional GCr15 bearing carbonitriding technology (CN101343747A) first performs nitriding and nitriding treatment (6-8 hours) in a high-temperature furnace (830-850℃), and then puts the high-temperature bearing into quenching oil for quenching. Patent CN104805393B proposes a carburizing and quenching technology for metal parts, which also performs carburizing treatment in a high-temperature furnace (880℃) and then puts it into coolant for quenching. Summary of the invention

[0004] To solve the above problems, the present invention provides a GCr15 steel workpiece surface strengthening method, processing equipment and workpiece strengthened by the method. The method uses laser to simultaneously perform nitriding and quenching treatment in a closed chamber at room temperature, completing two processes in one step, does not require a high temperature environment, has high efficiency and low energy consumption.

[0005] The present invention adopts the following technical solution.

[0006] The surface strengthening method of GCr15 steel workpiece comprises the following steps: (1) Place the GCr15 steel workpiece in an ammonia environment; (2) A high-energy laser beam is used to perform laser quenching on the GCr15 steel workpiece. The ammonia gas around the quenching zone is heated and decomposed under the action of the high-energy laser. After the ammonia gas is decomposed, active nitrogen molecules are generated, which absorb energy, accelerate the cooling speed of the bearing, and form a laser quenching layer. At the same time, the active nitrogen molecules diffuse on the metal surface of the quenching zone and penetrate into the interior of the GCr15 steel workpiece to form a nitriding layer, thereby achieving dual strengthening of laser quenching and nitriding on the bearing track surface.

[0007] Furthermore, the ammonia environment refers to an oxygen-free environment with an ammonia purity of >99.99% and a pressure between 200-400Kpa; the high-energy laser beam refers to a laser beam with an energy density between 80-200w / cm2.

[0008] Furthermore, in step (2), the laser quenching temperature is 800-900°C.

[0009] The present invention also provides a GCr15 steel workpiece treated by a surface strengthening method of a GCr15 steel workpiece, comprising a GCr15 steel workpiece substrate and a strengthening layer arranged on the substrate, wherein the thickness of the strengthening layer is 0.2-0.5 mm; the strengthening layer comprises martensite and residual austenite, the martensite is a mixed structure of lath martensite and needle martensite, and the residual austenite is distributed between martensite laths and between martensite needles and cementite particles.

[0010] The present invention also provides a processing device for the surface strengthening method of a GCr15 steel workpiece, comprising: The sealed cavity is provided with a laser window and an air inlet, and the air inlet is used to connect to the ammonia delivery system; A rotating mechanism is disposed in the closed cavity and is used to carry the GCr15 steel workpiece and drive it to rotate; The laser is connected to the laser quenching head through an optical fiber. The laser is used to emit laser light. The laser quenching head is used to focus and change the laser beam. The transformed laser beam passes through the laser window of the closed cavity.

[0011] Furthermore, the rotating mechanism includes a rotating motor and a clamp provided on the rotating motor, the clamp is used to clamp the GCr15 steel workpiece, and the rotation speed of the rotating motor can be adjusted.

[0012] Furthermore, the ammonia delivery system includes an ammonia cylinder and a pressure regulating valve, and the pressure regulating valve is connected to the air inlet and is used to adjust the air pressure in the closed cavity. Beneficial Effects

[0013] Compared with the prior art, the present invention has the following beneficial effects: The laser "quenching + nitriding" proposed in the present invention uses laser to simultaneously perform nitriding and quenching treatments in a closed chamber at room temperature, completing two processes in one step. It can improve the hardness and wear resistance of the surface, meet the manufacturing needs of high-end precision bearings, do not require a high temperature environment, and has high efficiency and low energy consumption.

[0014] The laser quenching strengthening technology has obvious advantages in improving the surface performance of GCr15 bearing rings, such as significantly reducing energy consumption, reducing workpiece deformation, obtaining higher surface hardness and wear resistance, and a high degree of automation, which can greatly improve production efficiency. It is a green and safe surface strengthening method. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the bearing raceway laser "quenching + nitriding" composite strengthening method according to an embodiment of the present invention.

[0016] Figure 2 It is a schematic diagram of a processing device for a surface strengthening method of a GCr15 steel workpiece according to an embodiment of the present invention.

[0017] Figure 3 It is a schematic diagram comparing the cross-sectional views of the inner ring of a bearing before and after quenching according to an embodiment of the present invention.

[0018] Figure 4 This is a microstructure diagram of the GCr15 steel workpiece matrix and after strengthening according to an embodiment of the present invention.

[0019] Figure 5 This is a comparison chart of the surface hardness of the bearing inner ring before and after the laser quenching and nitriding composite treatment according to an embodiment of the present invention.

[0020] Figure 6 This is a comparison chart of the friction coefficients of the inner ring of the bearing before and after the laser quenching and nitriding composite treatment according to an embodiment of the present invention.

[0021] Figure 7 This is a comparison chart of the wear rates of the inner ring of the bearing before and after the laser quenching and nitriding composite treatment according to an embodiment of the present invention.

[0022] In the figure: 1. Bearing ring; 2. Sealed cavity; 3. Clamp; 4. Laser beam; 5. Laser window; 6. Laser quenching head; 7. Laser; 8. Rotating motor; 10. Gas cylinder; 11. Gas control valve; 12. Gas inlet; 13. Gas outlet; 14. Control computer. DETAILED DESCRIPTION

[0023] The present invention is further described below in conjunction with specific embodiments and drawings. Example 1

[0024] See also Figure 1-7 , an embodiment of the present invention provides a surface strengthening method for a GCr15 steel workpiece.

[0025] In the illustrated embodiment, the GCr15 steel workpiece is a bearing made of GCr15 steel. It is understood that in other embodiments, other workpieces made of GCr15 steel may be surface strengthened.

[0026] The surface strengthening method of GCr15 steel workpiece comprises the following steps: (1) Place the GCr15 steel workpiece in an ammonia environment; (2) A high-energy laser beam is used to perform laser quenching on the GCr15 steel workpiece. The ammonia gas around the quenching zone is heated and decomposed under the action of the high-energy laser. After the ammonia gas is decomposed, active nitrogen molecules are generated, which absorb energy, accelerate the cooling rate of the GCr15 steel, and form a laser quenching layer. At the same time, the active nitrogen molecules diffuse on the metal surface of the quenching zone and penetrate into the interior of the GCr15 steel workpiece to form a nitriding layer, thereby achieving dual strengthening of laser quenching and nitriding on the surface of the GCr15 steel workpiece.

[0027] The ammonia environment contains cold ammonia.

[0028] Furthermore, the ammonia environment refers to an oxygen-free environment with an ammonia purity of >99.99% and a pressure between 200-400Kpa; the high-energy laser beam refers to a laser beam with an energy density between 80-200w / cm2.

[0029] Laser beams include Gaussian beams, uniform energy rectangular spots, etc.

[0030] Furthermore, in step (2), the laser quenching temperature is 800-900°C.

[0031] The decomposition temperature of ammonia is just in the quenching temperature range of GCr15 steel (NH3 decomposition temperature 800-900℃). After the ammonia is decomposed, it generates active nitrogen molecules, which absorb a lot of energy, accelerate the cooling speed of the bearing, and form a laser quenching layer. At the same time, the active nitrogen molecules diffuse on the metal surface of the quenching zone and penetrate into the interior of the GCr15 steel to form a nitriding layer, thereby achieving the dual strengthening of "laser quenching + nitriding" on the surface of GCr15 steel, and improving the hardness and wear resistance of GCr15 steel.

[0032] The present invention also provides a GCr15 steel workpiece treated by a surface strengthening method of a GCr15 steel workpiece, comprising a GCr15 steel substrate and a strengthening layer arranged on the substrate, wherein the thickness of the strengthening layer is 0.2-0.5 mm; the strengthening layer comprises martensite and residual austenite, the martensite is a mixed structure of lath martensite and needle martensite, and the residual austenite is distributed between martensite laths and between martensite needles and cementite particles.

[0033] In this embodiment, the workpiece is a bearing, and the quenched portion is the bearing ring raceway. The hardness and wear resistance of the bearing ring are improved through the dual strengthening of "laser quenching + nitriding".

[0034] The present invention also provides a processing device for the surface strengthening method of a GCr15 steel workpiece, comprising: The sealed cavity is provided with a laser window and an air inlet, and the air inlet is used to connect to the ammonia delivery system; A rotating mechanism is disposed in the closed cavity and is used to carry the GCr15 steel workpiece and drive it to rotate; The laser is connected to the laser quenching head through an optical fiber. The laser is used to emit laser light. The laser quenching head is used to focus and change the laser beam. The transformed laser beam passes through the laser window of the closed cavity.

[0035] The sealed cavity is provided with an air inlet and an air outlet for charging and discharging ammonia. The laser window allows the laser beam to pass through the window and act on the workpiece. It is generally made of high-transmittance quartz glass or sapphire glass.

[0036] The laser is used to generate a high-energy laser beam, including a fiber laser, a semiconductor laser, a carbon dioxide laser, etc. The laser mode can be a continuous laser and a pulsed laser; the laser quenching head is used to focus and change the laser beam to form a focused Gaussian beam or a uniform rectangular spot that meets the energy density.

[0037] The device fills a closed cavity with ammonia through an ammonia delivery system to make it meet the conditions in the method; a rotating mechanism drives the workpiece in the closed cavity to rotate; a laser beam performs laser "quenching + nitriding" composite strengthening on the rotating workpiece (in this embodiment, the bearing ring raceway).

[0038] Furthermore, the rotating mechanism includes a rotating motor and a clamp provided on the rotating motor, the clamp is used to clamp the GCr15 steel workpiece, and the rotation speed of the rotating motor can be adjusted.

[0039] The rotating mechanism is used to fix and rotate the GCr15 steel workpiece, and can adjust the speed v to complete the strengthening treatment of the corresponding position of the workpiece in cooperation with the laser beam. It includes a rotating motor and a tooling holder, in which the holder is inserted into a closed cavity filled with ammonia.

[0040] Furthermore, the ammonia delivery system includes an ammonia cylinder and a pressure regulating valve, and the pressure regulating valve is connected to the air inlet and is used to adjust the air pressure in the closed cavity.

[0041] The equipment also includes a control system for controlling the laser and the rotating mechanism to achieve precise control of the laser power, the rotating speed, and the light emission time, thereby achieving control over the depth and performance of the composite strengthening layer.

[0042] Among them, the light emission time t satisfies: t=1 / v. Example 2

[0043] The specific implementation process of Example 2 of the present invention is as follows: (1) The bearing ring 1 is mounted on a holder 3, which is mounted on a rotating motor 8 and extends into the closed cavity 2, so that the bearing ring 1 is in the closed cavity 2, and the rotation speed v is set by the control computer 14.

[0044] (2) Close the gas outlet 13, and then open the gas control valve 11, so that the NH3 in the gas cylinder 10 enters the closed cavity 2 through the gas inlet 12. By controlling the computer 14 and the gas control valve 11, the gas flow rate and pressure are set to ensure that the gas pressure in the closed cavity is controlled at 200-400 KPa.

[0045] (3) The power p and the light emission time t (t=1 / v) of the laser 7 are set by controlling the computer 14. The laser is transmitted to the laser quenching head 6 through the optical fiber, and a rectangular spot is formed after optical transformation. The transformed laser beam 4 is irradiated onto the raceway of the bearing ring 2 through the laser window 5 of the closed cavity 2, and a laser "quenching + nitriding" composite strengthening treatment is performed to form a strengthening layer with a certain thickness of 0.2-0.5 mm ( Figure 3 ).

[0046] The laser "quenching + nitriding" treatments under different laser powers of five groups A1, A2, A3, A4, and A5 were carried out by the method of Example 2. The air pressure in the closed cavity was set to 300 KPa, the laser used a semiconductor laser with a wavelength of 1080 nm, the laser beam spot was a uniform energy rectangular spot, and the spot size after focusing was 6 mm × 3 mm. The settings of the bearing rotation speed v, laser power p, and light emission time t are shown in Table 1.

[0047] Table 1 Bearing inner ring laser "quenching + nitriding" composite treatment process parameters

[0048] After treatment, the microstructure, microhardness and friction and wear properties of A1, A2, A3, A4 and A5 were analyzed and found to be: (1) The matrix structure of GCr15 steel is spheroidized. After laser quenching and nitriding, the strengthening layer obtains martensite and retained austenite. The martensite is a mixed structure of lath martensite and needle martensite. The retained austenite is distributed between martensite laths and between martensite needles and cementite particles. The thickness of the strengthening layer is about 0.4 mm ( Figure 4 ).

[0049] (2) After the composite strengthening of "quenching + nitriding", the microhardness of the strengthening layer under the five groups of parameters is higher than 65HRC, which is about 2.6 times that of the GCr15 steel matrix ( Figure 5 ), indicating that the laser "quenching + nitriding" composite treatment can significantly improve the microhardness of the bearing raceway surface.

[0050] (3) After the composite strengthening of "quenching + nitriding", the average friction coefficient of the strengthening layer under the five groups of parameters is 0.52, which is less than the friction coefficient of the GCr15 steel matrix 0.66. The wear rate after strengthening treatment is much lower than the wear rate of the GCr15 steel matrix ( Figure 6 ). It can be seen that the laser "quenching + nitriding" composite treatment can greatly improve the wear resistance of the bearing raceway.

[0051] The examples described in the present invention are merely descriptions of the preferred implementation modes of the present invention, and are not intended to limit the concept and scope of the present invention. Without departing from the design concept of the present invention, various modifications and improvements made to the technical solutions of the present invention by engineers and technicians in this field should all fall within the protection scope of the present invention.

Claims

1. A surface strengthening method for a GCr15 steel workpiece, characterized in that: Includes steps: (1) Place the GCr15 steel workpiece in an ammonia environment; (2) A high-energy laser beam is used to perform laser quenching on the GCr15 steel workpiece. The ammonia gas around the quenching zone is heated and decomposed under the action of the high-energy laser. After the ammonia gas is decomposed, active nitrogen molecules are generated, which absorb energy, accelerate the cooling speed of the bearing, and form a laser quenching layer. At the same time, the active nitrogen molecules diffuse on the metal surface of the quenching zone and penetrate into the interior of the GCr15 steel workpiece to form a nitriding layer, thereby achieving dual strengthening of laser quenching and nitriding on the bearing track surface.

2. The surface strengthening method of a GCr15 steel workpiece according to claim 1, characterized in that: Ammonia environment refers to an oxygen-free environment with ammonia purity of >99.99% and a pressure between 200-400Kpa; high-energy laser beam refers to an environment with an energy density of 80-200w / cm 2 between the laser beams.

3. The surface strengthening method of a GCr15 steel workpiece according to claim 1, characterized in that: In step (2), the laser quenching temperature is 800-900°C.

4. A GCr15 steel workpiece treated by the surface strengthening method of a GCr15 steel workpiece according to claim 1, characterized in that: It includes a GCr15 steel matrix and a strengthening layer arranged on the matrix, wherein the thickness of the strengthening layer is 0.2-0.5mm; the strengthening layer includes martensite and residual austenite, wherein the martensite is a mixed structure of lath martensite and needle martensite, and the residual austenite is distributed between martensite laths and between martensite needles and cementite particles.

5. A processing device for the surface strengthening method of a GCr15 steel workpiece as claimed in claim 1, characterized in that: include: The sealed cavity is provided with a laser window and an air inlet, and the air inlet is used to connect to the ammonia delivery system; A rotating mechanism is disposed in the closed cavity and is used to carry the GCr15 steel workpiece and drive it to rotate; The laser is connected to a laser quenching head through an optical fiber. The laser is used to emit laser light. The laser quenching head is used to focus and change the laser beam. The transformed laser beam acts on the surface of the GCr15 steel workpiece through a laser window in a closed cavity.

6. The processing device according to claim 5, characterized in that The rotating mechanism includes a rotating motor and a clamp provided on the rotating motor, the clamp is used to clamp a GCr15 steel workpiece, and the rotating speed of the rotating motor can be adjusted.

7. The processing device according to claim 5, characterized in that The ammonia delivery system comprises an ammonia cylinder and a pressure regulating valve, wherein the pressure regulating valve is connected to the air inlet of the sealed cavity and is used to regulate the air pressure in the sealed cavity.

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