CN117305552A - A method to improve the surface mechanical properties of 45 steel - Google Patents

Abstract

The invention discloses a method for improving the surface mechanical properties of 45 steel, which specifically includes the following steps: Step 1: pre-processing, milling the cut test block workpiece, then processing a powder groove on the surface of the test block, and finally using cleaning solvent to The workpiece is cleaned after milling. Step 2: Pretreatment, pre-coat the cleaned workpiece with W‑Ni mixed powder. Step 3: Electron beam processing, using a ring electron beam to continuously scan the surface of the workpiece. Step 4: Structure and performance testing. Use a laser microscope to obtain the cross-sectional morphology, a scanning electron microscope to observe the internal structure; a microhardness tester to measure the hardness, and a friction and wear testing machine to test its wear resistance. That is to say, the method disclosed in the present invention can not only improve the surface hardness of 45 steel, but also improve its wear resistance, and has excellent application prospects.

Description

A method to improve the surface mechanical properties of 45 steel

【Technical field】

The invention belongs to the technical field of high-energy beam surface modification of 45 steel, and specifically relates to a method for improving the surface mechanical properties of 45 steel.

【Background technique】

45 steel is a high-quality carbon structural steel with good comprehensive mechanical properties: high strength, good cutting performance, low processing cost, and wide use in industry. In actual production, it is mostly used in shaft parts, and is also commonly used in gears, racks, connecting rods, etc. in machinery. Due to the working conditions of gears, shafts, etc., the surface of the material needs to have high hardness and wear resistance. However, the surface hardness of 45 steel after heat treatment is generally low, and it is easy to fail in high temperature and high stress environments, and 45 steel in There is a problem of being easily corroded during use, so the scope of use is greatly restricted. If you can choose the appropriate surface treatment process to improve the surface properties of 45 steel, you can not only significantly reduce the manufacturing cost, but also save energy and expand its scope of use.

Electron beam surface modification technology uses high-energy-density electron beams to bombard the material surface and convert kinetic energy into thermal energy on the sub-surface, causing the material surface to rapidly heat up and then cool rapidly to achieve the surface modification effect. Electron beams can convert 90% of electrical energy into thermal energy, with high energy utilization. It has a "self-quenching" effect and does not require cooling and quenching, so it will not pollute the environment and is green and environmentally friendly. Therefore, this patent proposes a method to improve the surface mechanical properties of 45 steel, which can not only improve the surface hardness of 45 steel, but also enhance its wear resistance and expand the application of electron beams in the field of material surface modification.

[Content of the invention]

The purpose of this invention is:

This invention mills and cuts a 45 steel workpiece, cleans the milled test block with acetone and absolute ethanol solvents, and finally obtains a finished sample through electron beam processing. The present invention can effectively improve the surface hardness and at the same time improve the wear resistance of the test block surface, and has excellent practical application scenarios.

In order to solve the appeal problem, the technical solution adopted by the present invention is:

1. A method to improve the surface mechanical properties of 45 steel, including the following steps:

Step 1: Pretreatment, mill the cut test block workpiece, then machine a powder groove on the surface of the test block, and finally clean the milled workpiece with acetone and absolute ethanol solvents to remove surface oil and impurities.

After step 1, proceed to step 2;

Step 2: Pretreatment, perform W-Ni mixed powder, uniformly mix W powder with a purity of 99.9% and an average particle size of 44 μm and Ni powder with an average particle size of 10 μm in a ratio of W:Ni=7:3 Finally, pre-coat the cleaned workpiece in the powder tank.

After step 2, proceed to step 3;

Step 3: Electron beam processing, place the pre-processed workpiece on the workbench of the electron beam welding machine, and then evacuate the welding processing chamber to a vacuum degree of 6.5×10-3Pa. Set the process parameters of the electron beam welding machine on the control panel as follows: acceleration voltage 60kV, beam current 24mA, electron gun moving speed 1mm/s, and scanning frequency 300Hz. The energy densities of samples 1#, 2#, 3# and 4# are 98, 132, 201 and 425J/cm ² respectively. The finished product is obtained by continuously scanning the surface of the workpiece with a ring electron beam.

After step 3, proceed to step 4;

Step 4: Structure and performance testing, obtain the cross-sectional morphology through a laser microscope, and observe the microstructure of the sample using a Quanta FEG450 field emission scanning electron microscope. The HXD-1000TM microhardness tester is used to measure the microhardness of the workpiece with a load of 0.981N and a loading time of 10s. Every 100 μm on the center line of the cross-section of the sample is used as a measurement point. Data are recorded every 50 μm on the left and right of each test point. Five data are recorded for each test point. After removing the maximum and minimum values, the average value is taken as the test. The microhardness of the point. The CFT-I material surface performance comprehensive tester was used to conduct the tribological test of the sample. The test conditions were: diameter The GCr15 ball is used as the friction pair, the working load is 30N, the reciprocating friction distance is 3mm, the speed is 1mm/s, and it lasts for 45 minutes at room temperature. The wear amount is tested with its test component probe surface profiler.

2. A method for improving the surface mechanical properties of 45 steel according to claim 1, characterized in that: cutting processing is required before step 1, and a CNC milling machine is used to cut the 45 steel material into

50mm×50mm×50mm test block.

3. A method for improving the surface mechanical properties of 45 steel according to claim 1, characterized in that: in step 1, the powder slot is processed on the surface of the test block with a size of 47mm×7mm×0.9mm. Slot, during the milling process, keep the feed amount and milling speed of each workpiece consistent, and obtain the milled test block.

4. A method for improving the surface mechanical properties of 45 steel according to claim 1, characterized in that: the main components of the cleaning solvent in step 1 are acetone and absolute ethanol.

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

1. The present invention uses electron beam scanning to treat the surface of 45 steel, which not only improves the surface hardness, but also effectively enhances its surface wear resistance. The invention adopts electron beam scanning method to instantly heat 45 steel to the melting point of the material, and then rapidly cool down. The rapid thermal and quenching process causes a large temperature gradient on the surface of the test block, which can quickly harden and achieve an overall improvement in surface hardness and wear resistance.

2. When the present invention processes 45 steel with scanning electron beams, the electron beam acts on the surface of the test block, generating a large amount of heat in a short period of time and then spreading. Because the matrix conducts heat quickly and has a large cooling rate, the structure of the molten layer and heat-affected zone of the material is refined through rapid cooling and rapid heating, and the surface hardness and wear resistance are improved, similar to the quenching effect of heat treatment. Due to the lower heating temperature of the test block matrix, the internal structure remains unchanged, and the material still has high toughness inside. Therefore, the present invention can improve surface properties such as hardness and wear resistance.

3. The process of electron beam processing of 45 steel in the present invention is carried out in a vacuum processing chamber, which can ensure that the environment during the processing is pollution-free and avoid contact between 45 steel and the outside world; at the same time, the energy transfer medium is electrons, which has high energy conversion and good effect. Features.

4. The microhardness of the 45 steel matrix prepared by the present invention is 223.7HV, the microhardness of the modified layer is 877.6HV, and the hardness of the modified layer is 3.9 times the hardness of the matrix. That is, through the electron beam scanning process of the present invention, the surface hardness of the 45 steel test block is significantly improved. When the working load is 30N, the reciprocating length is 3mm, the speed is 1mm/s, and it lasts for 45 minutes at room temperature, the wear amount is 0.0054mm3, which is only 11.6% of the base body ( ^0.0466mm3 ).

[Picture description]

Figure 1(a) is a surface morphology diagram of 45 steel obtained after the implementation of the present invention;

Figure 1(b) is a cross-sectional morphology diagram of 45 steel obtained after the implementation of the present invention;

Figure 2 is a microstructure diagram of the modified layer of 45 steel obtained after the implementation of the present invention;

Figure 3 is a microhardness distribution diagram along the depth direction after the implementation of the present invention;

Figure 4 is a wear test chart of the 45 steel surface obtained before and after the implementation of the present invention.

【Detailed ways】

The following are specific embodiments of the present invention. The solutions of the present invention are further described with reference to the accompanying drawings, but the present invention is not limited to these embodiments.

A method to improve the surface mechanical properties of 45 steel, including the following steps:

Step 1: Pretreatment, mill the cut test block workpiece, then machine a powder groove on the surface of the test block, and finally clean the milled workpiece with acetone and absolute ethanol solvents to remove surface oil and impurities.

After step 1, proceed to step 2;

Step 2: Pretreatment, perform W-Ni mixed powder, uniformly mix W powder with a purity of 99.9% and an average particle size of 44 μm and Ni powder with an average particle size of 10 μm in a ratio of W:Ni=7:3 Finally, pre-coat the cleaned workpiece in the powder tank.

After step 2, proceed to step 3;

Step 3: Electron beam processing, place the pre-processed workpiece on the workbench of the electron beam welding machine, and then evacuate the welding processing chamber to a vacuum degree of 6.5×10-3Pa. Set the process parameters of the electron beam welding machine on the control panel as follows: acceleration voltage 60kV, beam current 24mA, electron gun moving speed 1mm/s, and scanning frequency 300Hz. The energy densities of samples 1#, 2#, 3# and 4# are 98, 132, 201 and 425J/cm ² respectively. The finished product is obtained by continuously scanning the surface of the workpiece with a ring electron beam.

After step 3, proceed to step 4;

Step 4: Structure and performance testing, obtain the cross-sectional morphology through a laser microscope, and observe the microstructure of the sample using a Quanta FEG450 field emission scanning electron microscope. The HXD-1000TM microhardness tester is used to measure the microhardness of the workpiece with a load of 0.981N and a loading time of 10s. Every 100 μm on the center line of the cross-section of the sample is used as a measurement point. Data are recorded every 50 μm on the left and right of each test point. Five data are recorded for each test point. After removing the maximum and minimum values, the average value is taken as the test. The microhardness of the point. The CFT-I material surface performance comprehensive tester was used to conduct the tribological test of the sample. The test conditions were: diameter The GCr15 ball is used as the friction pair, the working load is 30N, the reciprocating friction distance is 3mm, the speed is 1mm/s, and it lasts for 45 minutes at room temperature. The wear amount is tested with its test component probe surface profiler.

The surface morphology of the electron beam-treated test block was observed using an optical microscope and the cross-sectional morphology observed under a laser microscope is shown in Figure 1 (a) and (b). In Figure 1(a), it can be observed that the surface exhibits metallic luster. It can be seen from Figure 1(b) that metallurgical bonding occurs between the 45 steel coating and the substrate after the implementation of the present invention, and the cross section is divided into alloy zone, heat-affected zone and substrate. The distribution boundary between the modified layer and the matrix is relatively obvious. Figure 2 shows the microstructure of the alloy area of the test block magnified to 1000 times. The structure is evenly distributed and the surface grains are significantly refined, thus improving surface properties such as hardness and wear resistance.

The HDX-1000TM microhardness tester was used to measure the microhardness of the workpiece under a load of 0.981N and a loading time of 10s. The microhardness of the modified layer was 877.6HV, the microhardness of the matrix was 223.7HV, and the overall hardness increased by 3.9 times, as shown in Figure 3. shown.

CFT-I material surface performance comprehensive tester in use diameter The GCr15 ball is used as the friction pair, the working load is 30N, the reciprocating friction distance is 3mm, the speed is 1mm/s, and the wear resistance test is conducted at room temperature for 45 minutes. As shown in Figure 4, the wear amount is 0.0054mm ³ , which is only 11.6% of the base body (0.0466mm ³ ), which greatly improves its wear resistance.

The above description is a specific detailed description of feasible examples of the present invention, but the examples are not used to limit the scope of the patent application of the present invention. All equivalent changes or modifications completed within the technical spirit of the present invention should be covered by the present invention. patent scope.

Claims (4)

1. A method for improving the mechanical properties of 45 steel surface comprises the following steps:

step 1: and (3) preprocessing, namely milling the cut test block workpiece, processing a powder placing groove on the surface of the test block, and finally cleaning the milled workpiece by using acetone and absolute ethyl alcohol solvent to remove oil stains and impurities on the surface.

Step 2 is carried out after the step 1 is finished;

step 2: pretreatment, carrying out W-Ni mixed powder, and carrying out W: ni=7:3, and the W powder with the purity of 99.9 percent and the average particle diameter of 44 mu m and the Ni powder with the average particle diameter of 10 mu m are evenly mixed and then are precoated in a powder placing groove of the cleaned workpiece.

Step 3 is carried out after the step 2 is finished;

step 3: and E, electron beam treatment, namely placing the pretreated workpiece on a workbench of an electron beam welding machine, and vacuumizing a welding processing chamber until the vacuum degree is 6.5X10-3 Pa. The technical parameters of the electron beam welding process are set on the control panel as follows: acceleration voltage is 60kV, beam current is 24mA, electron gun moving speed is 1mm/s, and scanning frequency is 300Hz. The energy densities of the samples No. 1, no. 2, no. 3 and No. 4 are 98, 132, 201 and 425J/cm respectively ² . And continuously scanning the surface of the workpiece by using an annular electron beam to obtain a finished product.

Step 3, after finishing the step 4;

step 4: and (3) tissue and performance testing, wherein the cross section morphology is obtained through a laser microscope, and the microstructure of the sample is observed by adopting a Quanta FEG450 field emission scanning electron microscope. Work piece microhardness was measured using an HXD-1000TM microhardness tester with a load of 0.981N and a loading time of 10 seconds. And taking every 100 mu m of the center line of the cross section of the sample as a measuring point, respectively recording data at every 50 mu m of the left and right of each test point, recording 5 data of each test point, removing the maximum value and the minimum value, and taking the average value as the microhardness of the test point. The tribology test of the sample is carried out by adopting a CFT-I type material surface property comprehensive tester, and the test conditions are as follows: GCr15 balls with diameter phi=3 mm were used as friction pairs, working load was 30N, reciprocating friction distance was 3mm, speed was 1mm/s, and duration was 45 minutes at room temperature, and abrasion loss was measured by using a probe type surface profiler of its test assembly.

2. The method for improving the mechanical properties of the surface of 45 steel according to claim 1, wherein the method comprises the following steps: cutting treatment is needed before the step 1, and a numerical control milling machine is adopted to cut the 45 steel material into test blocks with the dimensions of 50mm multiplied by 50 mm.

3. The method for improving the mechanical properties of the surface of 45 steel according to claim 1, wherein the method comprises the following steps: and (2) processing a powder placing groove on the surface of the test block in the step (1) to obtain a milled test block, wherein the surface of the powder placing groove is processed to be 47mm multiplied by 7mm multiplied by 0.9mm, and the feeding amount of each workpiece is kept consistent and the milling speed is the same in the milling process.

4. The method for improving the mechanical properties of the surface of 45 steel according to claim 1, wherein the method comprises the following steps: the main components of the cleaning solvent in the step 1 are acetone and absolute ethyl alcohol.