Impurity-free and high-wear-resistant modification method for 5CrNiMo steel

Abstract

The invention discloses an impurity-free and high-wear-resistant modification method for 5CrNiMo steel, which specifically comprises the following steps: step 1, pretreatment: cutting and milling a test block workpiece, processing the test block workpiece into a fixed size and shape, and then cleaning the processed workpiece by using an ultrasonic cleaning machine; step 2, preparing a sample, and polishing the test block by using a metallographic polishing machine until the test block is polished; 3, electron beam treatment, wherein electron beams are adopted for conducting continuous scanning treatment on the sample. And 4, tissue and performance testing: observing the microstructure by adopting a scanning electron microscope, measuring the hardness by utilizing a microhardness tester, and detecting the wear resistance by utilizing a friction wear testing machine. According to the method disclosed by the invention, the surface hardness, the wear resistance and the corrosion resistance of the 5CrNiMo steel can be remarkably improved, and the method has an extremely good application scene.

Description

Technical Field

[0001] The invention belongs to the technical field of high-energy beam surface modification, and in particular relates to a modification method for 5CrNiMo steel with no impurities and high wear resistance. Background Art

[0002] With the continuous upgrading of the manufacturing industry, the requirements of mechanical equipment for material performance are also increasing. Especially for mechanical structures and components operating under high strength, high load and complex working environments, their performance stability and service life are directly related to the efficiency and safety of industrial systems. Therefore, improving the service performance of key components under harsh working conditions has become an important research direction in the current field of materials engineering. As a typical alloy structural steel, 5CrNiMo steel is widely used in heavy-duty mechanical parts, hot forging dies and high-strength transmission parts due to its excellent hardenability, high strength and good toughness. However, with the continuous improvement of modern industry's requirements for product precision and service life, it is difficult to meet the actual application needs by relying solely on traditional heat treatment methods, especially in improving wear resistance, fatigue resistance and corrosion resistance. In order to further improve the service ability of 5CrNiMo steel under complex working conditions and extend its service life, material surface strengthening treatment has become a key technical approach. At present, commonly used surface treatment methods such as induction hardening, electroplating, carburizing, nitriding and traditional heat treatment can improve surface properties to a certain extent, but they generally have problems such as complex process, high energy consumption, high cost and environmental pollution, which restricts its large-scale promotion and application. Therefore, developing a new 5CrNiMo steel surface strengthening technology that is both efficient, economical and environmentally friendly has become an inevitable trend to meet the needs of modern industrial manufacturing. This not only helps to improve the overall performance of parts, but also has important significance for promoting the engineering application of high-performance materials. Electron beam surface modification is a process in which an electron beam acts on the surface of the material to cause a strong melting phenomenon in the shallow surface layer of the material. Since the matrix is ​​still in a cold state, the shallow surface layer instantly transfers heat to the matrix, and after rapid cooling, the composition and organizational structure change, thereby achieving the desired performance. Compared with other material surface modification technologies, the advantages of electron beam surface modification are: (1) High power density, flexible control, good repeatability, and the ability to accurately control surface temperature and penetration depth; (2) It is carried out under vacuum conditions, which can protect the metal well and obtain higher bonding strength and performance, thus ensuring quality.

[0003] Therefore, this patent proposes to use a scanning electron beam surface modification method to modify the surface of 5CrNiMo steel. Electron beam surface modification is to bombard the material surface with an electron beam, causing the surface temperature of the material to rise rapidly and then cool rapidly, thereby achieving the effect of improving wear resistance. Because of the presence of grain refinement, the wear resistance and corrosion resistance of 5CrNiMo steel can be improved. The mechanism research and experimental conclusions are applied to the surface modification of other metal materials, expanding the field of high-energy beam material surface processing. Summary of the invention

[0004] The objects of the present invention are: The present invention processes 5CrNiMo steel into a fixed size shape, uses a metallographic polishing machine to polish it, and obtains a sample; and then performs surface modification treatment with a scanning electron beam to obtain a finished sample. The present invention effectively improves the surface wear resistance while also improving the surface hardness and corrosion resistance of the test block, and has an excellent practical application scenario.

[0005] To solve the above problem, the technical solution adopted by the present invention is: a method for electron beam processing 5CrNiMo steel, comprising the following steps: Step 1: Pre-treatment: Cut and mill the test piece into a fixed size and shape, and then use an ultrasonic cleaner to clean the processed workpiece to remove surface oil and impurities.

[0006] After step 1, proceed to step 2; Step 2: Sample preparation: Use a metallographic polishing machine to grind from 600-grit sandpaper to 3000-grit and polish.

[0007] After step 2, proceed to step 3; Step 3: Electron beam treatment: Place the sample in the hot processing chamber of the electron beam welder and evacuate the chamber to a vacuum degree of 1.33×10 -3 Pa, the vacuum degree of the processing chamber is 6×10 -2 Pa. Set the electron beam welding machine process parameters, the electron beam acceleration voltage is 60kV, the electron beam current is 3mA, the electron gun moving speed is 6mm / s, and the electron beam radius is 3mm. Then cut the processed sample into small pieces, use an ultrasonic cleaner to clean the test block, and perform metallographic sample preparation to obtain the finished product.

[0008] After step 3, proceed to step 4; Step 4: Organization and performance testing: The microstructure of the sample was observed using a Quanta FEG450 field emission scanning electron microscope (SEM), and the microhardness of the sample cross section was measured using a HDX-1000TM microhardness tester with a load of 100 g, a test force of 0.981 N, and a loading time of 5 s. The friction and wear test was performed on the surface of the sample after sandpaper polishing using a CFT-I material surface performance comprehensive tester, with a loading load of 30 N, a reciprocating length of 3 mm, a rotation speed of 300 r / min, and a duration of 15 min.

[0009] According to claim 1, a modification method for 5CrNiMo steel without impurities and high wear resistance is characterized in that: before step 1, cutting treatment is required to cut the 5CrNiMo steel workpiece into test blocks of 10mm×15mm×5mm, and metallographic polishing is performed. The method for modifying 5CrNiMo steel without impurities and with high wear resistance according to claim 1 is characterized in that: in step 3, it is necessary to adjust the electron beam focusing current for surface modification.

[0010] According to the modification method for 5CrNiMo steel with impurities and high wear resistance as described in claim 1, it is characterized in that: in step 3, the surface modification of the sample using a continuous electron beam can obtain grain refinement and a large amount of martensite.

[0011] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention uses a continuous electron beam to modify the surface of 5CrNiMo steel, which can effectively improve the surface hardness and the wear resistance of the sample surface. The present invention uses a scanning electron beam treatment method with a large energy density, which can quickly heat the 5CrNiMo steel to the melting point of the material and then quickly cool it down. The rapid heating and cooling process causes the sample modified layer and matrix structure to change, the grains to be refined, and the martensite content to increase significantly. At the same time, the alloy carbides of the stainless steel produce solid solution strengthening, which greatly improves the wear resistance of the sample surface.

[0012] 2. The process of scanning electron beam treatment of 5CrNiMo steel in the present invention is carried out in a vacuum processing chamber, which can ensure that the processing environment is pollution-free and avoid contact between 5CrNiMo steel and the outside world; at the same time, the energy transfer medium is electrons, which has the characteristics of high energy conversion and good effect.

[0013] 3. The microhardness of the 5CrNiMo steel matrix prepared by the present invention is 345HV 0.1 The maximum microhardness of the modified layer is 875HV 0.1, which is 2.6 times the hardness of the matrix. That is, after the electron beam treatment of the present invention, the surface hardness of the 5CrNiMo steel test block is significantly improved. Under a load of 30N, a reciprocating length of 3mm, and a test of 15min, the friction coefficient is reduced from 0.882 of the matrix to 0.421, a decrease of 52%. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 It is a diagram of the working principle of the electron beam of the present invention; Figure 2 This is the cross-sectional structure of 5CrNiMo steel obtained after the implementation of the present invention; Figure 3 It is an enlarged microstructure diagram of 5CrNiMo steel before the implementation of the present invention; Figure 4 This is a wear resistance test diagram of 5CrNiMo steel before the implementation of the present invention; Figure 5 This is a wear resistance test diagram of 5CrNiMo steel after the implementation of the present invention; DETAILED DESCRIPTION The following are specific embodiments of the present invention, and the scheme of the present invention is further described with reference to the accompanying drawings, but the present invention is not limited to these embodiments.

[0015] A method for electron beam processing 5CrNiMo steel comprises the following steps: 1. A method for electron beam treatment of 5CrNiMo steel, comprising the following steps: Step 1: Pre-treatment: Cut and mill the test piece into a fixed size and shape, and then use an ultrasonic cleaner to clean the processed workpiece to remove surface oil and impurities.

[0016] Step 1: Pre-treatment: Cut and mill the test piece into a fixed size and shape, and then use an ultrasonic cleaner to clean the processed workpiece to remove surface oil and impurities.

[0017] After step 1, proceed to step 2; Step 2: Sample preparation: Use a metallographic polishing machine to grind from 600-grit sandpaper to 3000-grit and polish.

[0018] After step 2, proceed to step 3; Step 3: Electron beam treatment, place the sample in the hot processing chamber of the electron beam welder, and evacuate it so that the vacuum degree of the electron gun chamber is 1.33×10^(-3)Pa, and the vacuum degree of the processing chamber is 6×10^(-2)Pa. Set the process parameters of the electron beam welder, the electron beam acceleration voltage is 60kV, the electron beam current is 3mA, the electron gun moving speed is 6mm / s, and the electron beam radius is 3mm. Then cut the treated sample into small pieces, clean the test pieces with an ultrasonic cleaner, and perform metallographic sample preparation to obtain the finished product.

[0019] After step 3, proceed to step 4; Step 4: Organization and performance test, using Quanta FEG450 field emission scanning electron microscope (SEM) to observe the microstructure of the sample, using HDX-1000TM microhardness tester with 100g load, 0.981N test force, 5s loading time to measure the microhardness of the sample cross section; using CFT-I type material surface performance comprehensive tester to conduct friction and wear test on the surface of the sample after sandpaper polishing, using 30N loading load, 3mm reciprocating length, 300r / min speed and 15min duration. The friction coefficient decreased by 52%. .

[0020] The microstructure of the samples was tested using a Quanta FEG450 field emission scanning electron microscope (SEM). Figure 2 As shown, the cross section is divided into a modified layer and a matrix. The fusion lines in each region are obvious, the grains in the modified layer are obviously refined, and the martensite content is increased, indicating that the matrix has a good modification effect. Figure 3 , Figure 4 To amplify the local modification effect, it can be found that the grains are refined and precipitated and the martensite content is greatly increased, and the mechanical properties of the material are greatly improved.

[0021] The above description is a specific and detailed description of a feasible example of the present invention, but the embodiment is not intended to limit the scope of the patent application of the present invention. All equivalent changes or modified changes completed under the technical spirit suggested by the present invention should fall within the patent scope covered by the present invention.

Claims

1. A method for improving the impurity-free and highly wear-resistant 5CrNiMo steel, comprising the following steps: Step 1: Pre-treatment: Cut and mill the test piece into a fixed size and shape, and then use an ultrasonic cleaner to clean the processed workpiece to remove surface oil and impurities.

2. After step 1, proceed to step 2.

3. Step 2: Sample preparation: Use a metallographic polishing machine to grind from 600-grit sandpaper to 3000-grit and polish.

4. After step 2, proceed to step 3.

5. Step 3: Electron beam treatment: Place the sample in the hot processing chamber of the electron beam welder and evacuate the chamber to a vacuum degree of 1.33×10 -3 Pa, the vacuum degree of the processing chamber is 6×10 -2 Pa. Set the electron beam welding machine process parameters, the electron beam acceleration voltage is 60kV, the electron beam current is 3mA, the electron gun moving speed is 6mm / s, and the electron beam radius is 3mm. Then cut the processed sample into small pieces, use an ultrasonic cleaner to clean the test block, and perform metallographic sample preparation to obtain the finished product.

6. After step 3, proceed to step 4.

7. Step 4: Organization and performance testing: The microstructure of the sample was observed using a Quanta FEG450 field emission scanning electron microscope (SEM), and the microhardness of the sample cross section was measured using a HDX-1000TM microhardness tester with a load of 100 g, a test force of 0.981 N, and a loading time of 5 s. The friction and wear test was performed on the surface of the sample after sandpaper polishing using a CFT-I material surface performance comprehensive tester, with a loading load of 30 N, a reciprocating length of 3 mm, a rotation speed of 300 r / min, and a duration of 15 min.

8. The method for improving 5CrNiMo steel with high wear resistance without impurities according to claim 1 is characterized in that: the pretreatment in step 1 requires cutting and milling, cutting the 5CrNiMo steel workpiece into test blocks of 10 mm×10 mm×5 mm, and performing metallographic polishing.

9. The method for improving 5CrNiMo steel with impurities and high wear resistance according to claim 1, characterized in that: step 3 uses a high-voltage continuous scanning electron beam for surface treatment.

10. A method for improving 5CrNiMo steel with high wear resistance without impurities according to claim 1, characterized in that: after the treatment in step 3, the wear resistance of the material is improved and the friction coefficient is reduced.

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