Method for treating high hardness stainless steel surface using microwave-assisted micro-forging technology

Abstract

The invention relates to a method for treating the surface of high-hardness stainless steel using a microwave-assisted micro-forging technology. The method comprises the following steps: (1) immersing a workpiece in an alkaline solution for degreasing; (2) water washing; (3) performing primary micro-forging: performing micro-forging using particles with a particle size of 100 to 200 μm to form a roughness of 5 to 20 μm; (4) immersing the workpiece after the primary micro-forging in an acidic cleaning solution for 30 seconds to remove dust and oxides; (5) rinsing the workpiece with deionized water and alcohol, and drying it in an oven at 80°C; (6) placing the workpiece in a microwave cavity that is evacuated or filled with an inert gas, and then subjecting it to microwave radiation; (7) performing secondary micro-forging on the surface of the workpiece: performing micro-forging using particles with a particle size of 20 to 100 μm to strengthen the stainless steel surface and control the morphology, thereby generating micron-sized pits on the surface of the workpiece; (8) pickling the workpiece after the secondary micro-forging for 30 seconds to remove fine particle dust; (9) rinsing with deionized water and alcohol, drying it in an oven at 80°C, and packaging it for standby use.

Description

Technical Field

[0001] The invention belongs to the technical field of metal surface strengthening, and in particular relates to a method for treating a high-hardness stainless steel surface using a microwave-assisted micro-forging technique. Background Art

[0002] Micron particle forging technology (abbreviated as micro-forging) is a new metal surface strengthening and modification technology developed based on traditional shot peening technology. This technology uses a high-speed (above 200m / s) stream of microparticles (particle size 20-200μm) to forge and strike the metal surface, instantly converting the coarse surface grains into fine grains. On the one hand, it improves the density of the metal surface structure, and on the other hand, it forms an ordered metal fiber structure. Ultimately, deformation strengthening of the structure can be achieved within a surface depth range of 20-40μm, resulting in a significant improvement in the plasticity, toughness, finish, corrosion resistance, and fatigue strength of the treated metal workpiece. It has been well applied in a number of metal material products such as harmonic gears and springs. The deeper the depth of the microparticle stream on the metal surface, the better the strengthening effect. As far as the current micro-forging process technology is concerned, the above-mentioned strengthening effect can be achieved for workpieces made of conventional metal alloys. However, when treating the surface of high-hardness alloy materials, the depth of the strengthening effect is greatly limited, resulting in the strengthening effect failing to meet the expected requirements.

[0003] Microwaves are a type of electromagnetic wave with a frequency between 300MHz and 300GHz. Microwave heating methods offer the advantages of non-contact heating, selective heating, rapid heating, and volumetric heating. For smooth bulk metals, microwaves interact only with the metal surface and are unable to generate volumetric heating, manifesting as reflected electromagnetic waves. Furthermore, as good conductors, metals exhibit a significant skin effect in electromagnetic fields. The alternating electromagnetic field induces a surface electric field on the metal surface, and the resulting induced current is distributed only on the surface, causing Joule heating. The higher the microwave frequency, the greater the metal's conductivity, the more pronounced the skin effect, and the smaller the skin depth. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies in the above-mentioned prior art and provide a method for treating high-hardness stainless steel surfaces with microwave-assisted micro-forging technology by cooperating with one another, thereby achieving a significant improvement in material hardness and fatigue life, strengthening and controlling the morphology of the stainless steel surface, generating micron-sized pits on the workpiece surface, thereby improving the hardness of the stainless steel workpiece, optimizing the fatigue resistance of the parts, and utilizing the characteristic of skin heating of metal conductors by microwaves to solve the pain points of microparticle forging of high-hardness alloys, thereby increasing the depth of strengthening effect of microparticles on high-hardness materials, and greatly extending the service life of high-hardness alloy workpieces. Another purpose of the present invention is to provide a method for treating high-hardness stainless steel surfaces with microwave-assisted micro-forging technology by only strengthening the metal surface while leaving the metal interior unaffected. After the metal surface temperature rises and the surface metal becomes soft and tough, the strengthening area and effect after microparticle forging are increased, while the original properties of the metal interior remain unchanged.

[0005] The technical solution of the present invention is a method for treating a high-hardness stainless steel surface using the microwave-assisted micro-forging technology, which is special in that it comprises the following steps:

[0006] ⑴ Soak the workpiece in alkaline solution for degreasing;

[0007] ⑵Washing;

[0008] (3) First-level micro-forging: Use particles with a particle size of 100-200 μm for micro-forging to form a roughness of 5-20 μm;

[0009] (4) Immerse the workpiece after the first-level micro-forging in acidic cleaning solution for 30 seconds to remove dust and oxides;

[0010] (5) Rinse the workpiece with deionized water, alcohol, and dry it in an oven at 80°C;

[0011] (6) Place the workpiece in a microwave cavity that is evacuated or filled with inert gas, and then irradiate it with microwaves;

[0012] ⑺ Perform secondary micro-forging on the workpiece surface: Use particles with a particle size of 20 to 100 μm for micro-forging to strengthen the stainless steel surface and control the morphology, and generate micron-sized pits on the workpiece surface;

[0013] ⑻ Pickle the workpiece after the secondary micro-forging treatment for 30 seconds to remove the fine dust particles;

[0014] ⑼ Rinse with deionized water, rinse with alcohol, dry in an oven at 80℃, and pack for later use.

[0015] Preferably, the alkaline degreasing in step (1) is to immerse the workpiece in an alkaline degreasing solution for 5 to 10 minutes at 50 to 90° C. to remove oil stains and fingerprints on the surface of the workpiece.

[0016] Preferably, the water washing in step (2) refers to rinsing with deionized water for 10 to 30 seconds.

[0017] Preferably, the first-level micro-forging in step (3) is to micro-forge the workpiece surface with 120-160 μm white corundum particles to form a roughness of 5-20 μm on the workpiece surface to increase the surface's absorption of microwaves.

[0018] Preferably, the acidic cleaning solution in step (4) is composed of the following components by weight: 5 parts of sulfuric acid, 5 parts of hydrochloric acid, and 90 parts of water, and is used to remove oxide scale, metal powder generated by primary micro-forging, and residual particles embedded in the workpiece surface.

[0019] Preferably, the drying in step (5) refers to baking the workpiece in an oven at 80-120° C. for 2-5 minutes.

[0020] Preferably, the microwave frequency in step (6) is 2.45 GHz, the irradiation time is 30 to 60 s, and the irradiation power is 1000 to 3000 W.

[0021] Preferably, the secondary micro-forging in step (7) refers to the microparticle size being between 20 and 100 μm, the coverage being 100%, the micro-forging scanning speed being 20 to 5 mm / s, the microparticle shooting speed being 200 to 350 m / s, and the angle between the spray gun and the workpiece surface being 15 to 90°.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The present invention strengthens the surface of stainless steel and controls the morphology by combining microwave radiation heating and secondary micro-forging, generates micron-sized pits on the surface of the workpiece, improves the hardness of the stainless steel workpiece, and optimizes the fatigue performance of the part.

[0024] (2) This invention utilizes the skin-heating property of microwaves on metal conductors, achieving heating only on the metal surface without causing any heat treatment effect on the metal's interior. As the metal's surface temperature rises and the surface metal softens and toughens, the area and effect of the strengthening effect after the microparticles forging are increased, while the metal's internal properties remain unchanged. In short, only the surface is strengthened while the interior is unaffected.

[0025] ⑶ The experimental results of the present invention show that only the cooperation of the first-stage micro-forging roughening, microwave irradiation and the second-stage micro-forging can achieve a significant improvement in the material hardness and fatigue life. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a process flow chart of the present invention;

[0027] Figure 2FIG. 4 is a schematic diagram of the dimensions of fatigue test samples according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with the accompanying drawings:

[0029] M390 steel typically has a Vickers hardness between 700 and 750 HV, making it one of the hardest stainless steels on the market. Even under extreme conditions, M390 steel maintains its high hardness and wear resistance, making it a preferred material for high-end folding knives, hunting knives, and other precision tools. All examples of this invention use M390 steel as the raw material, with the specimens measuring 70 × 19 × 4 mm flat.

[0030] Example 1

[0031] See also Figure 1 As shown, the sample surface treatment method steps are:

[0032] 1) Soak the workpiece in alkaline solution for degreasing;

[0033] 2) Rinse with deionized water;

[0034] 3) Use 120-160μm white corundum particles to perform first-level micro-forging on the workpiece surface;

[0035] 4) Soak the workpiece after the first-level micro-forging in an acidic solution for 30 seconds, take it out and rinse it with deionized water, rinse it with alcohol, and dry it in an oven at 80°C;

[0036] 5) Place the workpiece in the microwave cavity, then evacuate the cavity or fill it with inert gas (helium, nitrogen, argon, etc.), turn on the power and start microwave heating for 30 seconds, microwave frequency 2.45 GHz, and power 3000 W;

[0037] 6) After the microwave work is completed, the secondary micro-forging is immediately carried out, the particle size is 40-100 μm, the coverage is 100%, the micro-forging scanning speed is 20 mm / s, the particle shooting speed is 300 m / s, and the angle between the spray gun and the workpiece surface is 15°;

[0038] 7) Soak the micro-forged workpiece in an acidic solution for 30 seconds, rinse with deionized water, rinse with alcohol, dry in an oven at 80°C, and pack for later use.

[0039] The operating steps of Examples 2-5 and Comparative Examples 1-3 are the same as those of Example 1, with only the relevant parameters being different. The parameters and results of all Examples and Comparative Examples are listed in Table 1.

[0040] Table 1

[0041]

[0042] See also Figure 2 As shown, fatigue testing involves high-frequency tensile and compression testing of metal components, as well as fatigue performance, fracture mechanics, and fatigue life testing under alternating tension and compression loads. Fatigue life refers to the number of stress or strain cycles required for a material to experience fatigue failure under cyclic loading. During fatigue testing, a sinusoidal waveform was used, with a stress ratio of R = -1, a dynamic load of 935 MPa, a test loading frequency range of 81 to 83 Hz, and a laboratory temperature maintained at approximately 25°C. The structural dimensions of the fatigue specimens were prepared in accordance with GB / T 15248-2008. To facilitate statistical characterization of material properties, the specimens were cut from homogeneous raw material blanks.

[0043] The sample in Reference Example 1 was subjected to only one-stage micro-forging, without microwave and two-stage micro-forging. Its fatigue life under a load of 935 MPa was a minimum of only 538,468 times. Reference Example 2 was subjected to two-stage micro-forging, but without microwave irradiation. The hardness increased by 5%, and the fatigue life increased to 1,625,387 times. Reference Example 3 was subjected to microwave irradiation and two-stage micro-forging, but without the first-stage micro-forging to roughen the sample surface. The microwave irradiation efficiency was low, and the micro-forging effect was not good. The hardness increased to 8%, and the fatigue life increased to 1,856,214 times. Examples 1-5 were subjected to the complete operation of one-stage micro-forging, microwave irradiation, and two-stage micro-forging. The hardness increased by more than 15%, and the fatigue life was at least six times that of Reference Example 1. This shows that only the cooperation of one-stage micro-forging, microwave irradiation, and two-stage micro-forging can achieve a significant increase in material hardness and fatigue life.

[0044] The above descriptions are merely preferred embodiments of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention shall fall within the scope of the claims of the present invention.

Claims

1. A method for treating high-hardness stainless steel surface using microwave-assisted micro-forging technology, characterized in that: The following steps are involved: ⑴ Soak the workpiece in alkaline solution for degreasing; ⑵Washing; (3) First-level micro-forging: Use particles with a particle size of 100-200 μm for micro-forging to form a roughness of 5-20 μm; (4) Immerse the workpiece after the first-level micro-forging in acidic cleaning solution for 30 seconds to remove dust and oxides; (5) Rinse the workpiece with deionized water, alcohol, and dry it in an oven at 80°C; (6) placing the workpiece in a microwave cavity that has been evacuated or filled with an inert gas, and then irradiating it with microwaves, wherein the microwave frequency in step (6) is 2.45 GHz, the irradiation time is 30 to 60 seconds, and the irradiation power is 1000 to 3000 W; ⑺ Perform secondary micro-forging on the workpiece surface: Use particles with a particle size of 20 to 100 μm for micro-forging treatment, with a particle shooting speed of 200 to 350 m / s, to strengthen the stainless steel surface and control the morphology, and generate micron-level pits on the workpiece surface; ⑻ Pickle the workpiece after the secondary micro-forging treatment for 30 seconds to remove the fine dust particles; ⑼ Rinse with deionized water, rinse with alcohol, dry in an oven at 80°C, and package for later use.

2. The method for treating high-hardness stainless steel surface using microwave-assisted micro-forging technology according to claim 1, characterized in that: The alkaline degreasing in step (1) refers to immersing the workpiece in an alkaline degreasing solution for 5 to 10 minutes at 50 to 90° C. to remove oil stains and fingerprints on the surface of the workpiece.

3. The method for treating high hardness stainless steel surface by microwave-assisted micro-forging technology according to claim 1, characterized in that: The water washing in step (2) refers to rinsing with deionized water for 10 to 30 seconds.

4. The method for treating high hardness stainless steel surface by microwave-assisted micro-forging technology according to claim 1, characterized in that: The first-level micro-forging in step (3) is to micro-forge the workpiece surface with 120-160 μm white corundum particles to form a roughness of 5-20 μm on the workpiece surface to increase the surface's absorption of microwaves.

5. The method for treating high hardness stainless steel surface by microwave-assisted micro-forging technology according to claim 1, characterized in that: The acidic cleaning solution in step (4) is composed of the following components by weight: 5 parts of sulfuric acid, 5 parts of hydrochloric acid, and 90 parts of water, and is used to remove oxide scale, metal powder generated by primary micro-forging, and residual particles embedded in the surface of the workpiece.

6. The method for treating high-hardness stainless steel surface using microwave-assisted micro-forging technology according to claim 1, characterized in that: The drying in step (5) refers to baking the workpiece in an oven at 80-120° C. for 2-5 minutes.

7. The method for treating high hardness stainless steel surface by microwave-assisted micro-forging technology according to claim 1, characterized in that: The secondary micro-forging in step (7) means that the particle size is between 20 and 100 μm, the coverage is 100%, the micro-forging scanning speed is 20 to 5 mm / s, and the angle between the spray gun and the workpiece surface is 15 to 90 degrees.

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