High-strength alloy steel bolt surface laser phase change strengthening method

Abstract

The invention belongs to the field of high-strength alloy steel bolt manufacturing, and relates to a high-strength alloy steel bolt surface laser phase change strengthening method. The method comprises the following steps: carrying out cold machining and heat treatment on a high-strength alloy steel material to obtain a bolt to be subjected to laser phase change strengthening; a special tool or an adjustable sizing block is used for assisting in clamping the bolt in place, and alignment and leveling are carried out; after leveling, a special tool is used for cross inspection, and the uniformity of light spot size and energy distribution in a light beam area is ensured; and laser phase change strengthening is conducted on the polished rod outer circle and the threaded end face of the bolt.

Description

Technical Field

[0001] The invention belongs to the field of high-strength alloy steel bolt manufacturing and relates to a high-strength alloy steel bolt surface laser phase change strengthening method. Background Art

[0002] After conventional heat treatment, high-strength alloy steel bolts cannot meet the design requirements of high reliability, high wear resistance and long fatigue life under large loads. Now they can only be replaced by ultra-high-strength steel with higher strength. The material cost and processing cost are much higher than high-strength alloy steel bolts. The use of laser phase change strengthening technology can achieve the local heat treatment requirements of special parts of parts, improve the fatigue life of parts and the wear resistance of assembly surfaces. Summary of the invention

[0003] Purpose of the invention: To provide a laser phase change strengthening method, by which strengthening layers of different depths can be prepared on the outer cylindrical surface of the polished rod and the end surface of the thread of a high-strength alloy steel bolt of a specified size, so as to achieve the best performance of the alloy bolt. The best strengthening layer depth of the outer cylindrical surface of the polished rod is 0.6mm, and the best strengthening layer depth of the end surface of the thread is 0.4mm.

[0004] Technical Solution

[0005] A method for laser phase transformation strengthening of a high-strength alloy steel bolt surface is provided, comprising:

[0006] Cold working and heat treatment are performed on high-strength alloy steel materials to obtain bolts to be strengthened by laser phase transformation;

[0007] Use special tooling or adjustable washers to assist in clamping the bolts into place, and align and level them;

[0008] After leveling, use a dedicated tooling to cross-check to ensure uniformity of spot size and energy distribution within the beam area;

[0009] The outer circle of the bolt's polished rod and the threaded end face are laser phase transformation strengthened respectively.

[0010] Furthermore, the laser wavelength is 1080±5nm, the collimation focal length is 150mm, the focusing focal length is 300mm, and the spot size is 10×2mm.

[0011] Furthermore, the laser phase change strengthening process parameters corresponding to the outer cylindrical surface of the polished rod are: laser power: 1000-1100W; travel speed: 1.7-1.9mm / s; rotation speed: F6000; the laser phase change strengthening path adopts a spiral motion mode.

[0012] Furthermore, the laser phase change strengthening process parameters corresponding to the thread end face are: laser power: 1000-1100W; travel speed: 8-9mm / s; the laser phase change strengthening path adopts a reciprocating motion mode.

[0013] Furthermore, the requirements for the surface of the bolt to be laser phase transformation strengthened are: the surface is smooth and clean, the roughness is not less than Ra0.4, and there are no defects that may affect the laser phase transformation strengthening effect.

[0014] Furthermore, before laser phase change strengthening, the method further includes: performing process preparation;

[0015] Process preparation includes:

[0016] Before the laser phase change strengthening process begins, the bolts should be kept at the same ambient temperature as the laser used for laser phase change strengthening for at least 4 hours;

[0017] The heat treatment state of the parts is quenched and tempered, with a hardness of HRC 31.5~45;

[0018] During laser phase change strengthening, it is necessary to determine the path of the scanning beam on the surface of the workpiece being processed and use visible light for alignment.

[0019] Furthermore, laser phase transformation strengthening is performed on the outer circle of the polished rod and the end face of the thread of the bolt, respectively, including:

[0020] Start the laser, move forward from the starting point, use the long side of the light spot to scan the outer circle of the polished rod or the end face of the thread, and the scanning distance is ≥80mm. Set the program command to turn off the laser after completing the unidirectional strengthening, adjust to the positioning red light, move horizontally to the third point, use the long side of the light spot to scan the outer circle of the polished rod or the end face of the thread in the opposite direction, and turn off the laser after the operation is completed.

[0021] Furthermore, the high-strength alloy steel is 40CrNiMoA steel.

[0022] Beneficial effects:

[0023] The present invention realizes the strengthening requirements of the threaded end face and the outer cylindrical surface of the polished rod of the high-strength alloy steel bolt through laser phase change strengthening treatment, thereby improving the wear resistance and fatigue life of the high-strength alloy steel bolt. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the main view and end face area (frame line) of the high-strength bolt.

[0025] Figure 2 It is a schematic diagram of the main view of the high-strength bolt and the outer circular area of ​​the bare rod (frame line).

[0026] Figure 3 This is the complete process flow chart of bolt processing.

[0027] Figure 4 This is the process flow chart of laser phase change strengthening.

[0028] Figure 5 Schematic diagram of the laser phase transformation strengthening path on the end face.

[0029] Figure 6 Schematic diagram of the laser phase transformation strengthening path of the outer cylindrical surface. DETAILED DESCRIPTION

[0030] The present invention provides a method for laser phase transformation strengthening of the surface of a high-strength alloy steel bolt, comprising:

[0031] (1) Preparation of high-strength steel bolts

[0032] The material of high-strength steel bolts is 40CrNiMoA, and the pre-heat treatment state is "quenching + tempering". The high-strength steel bolts are pre-heat treated as a whole to σb = 1080 ± 100MPa. The main heat treatment processes are as follows:

[0033] Quenching: air furnace (III), set temperature 850℃, keep warm for 20-40min, oil cooling;

[0034] Tempering: air furnace (III), set temperature 520-600℃, insulation ≥120min, water cooling;

[0035] Hardness test: Sanding position is the outer cylindrical surface, sanding depth ≤ 0.15mm, surface roughness Ra requirement is not more than 3.2μm, 100% test Rockwell hardness HRC. After qualified heat treatment, it is machined to the finished product size and enters the laser phase change strengthening process.

[0036] (2) Laser phase transformation strengthening preparation

[0037] Bolts Figure 1 , 2 As shown, the end face area is located at one end of the left dotted frame line, and the outer circle area of ​​the bare rod is located in the middle dotted frame line.

[0038] A fiber laser is used with a laser wavelength of 1080 nm. The main technical parameters of the laser are shown in Table 1.

[0039] Table 1

[0040] Serial number project unit parameter 1 Maximum output power kW 6 2 Working Mode / Continuous / Modulated 3 Power adjustment range ％ 10～100 4 wavelength nm 1080±5

[0041] The technical parameters of the phase change enhanced beam shaping process head are shown in Table 2.

[0042] Table 2

[0043]

[0044]

[0045] The beam shaping process head is installed at the end of the manipulator, and the movement of the manipulator drives the linear motion of the laser spot. The surface of the high-strength steel bolt's polished rod to be strengthened is a curved surface. In order to achieve the coupling of the rectangular spot and the curved surface, the high-strength steel bolt is installed on the three-jaw chuck of the turntable, and the turntable drives the polished rod surface to rotate.

[0046] The measurement is divided into two parts: the measurement of high-strength steel bolts and the measurement of the beam shaping head. A dial indicator is used to measure the installation of the high-strength steel bolts and adjust them to the appropriate position. For the beam shaping head, the robot's built-in program is first used for leveling. After leveling, a special tooling is used for cross-checking to ensure the uniformity of the spot size and energy distribution in the beam area.

[0047] (3) Laser phase change strengthening

[0048] ① Use gauze dipped in anhydrous ethanol to wipe the surface of the high-strength steel bolt to remove stains and protective oil, and expose the smooth surface;

[0049] ② Use a hair dryer to quickly dry the surface of the sample. The surface of the high-strength steel bolt should be free of water stains and no color changes.

[0050] ③ Turn on the laser to locate the red light spot;

[0051] ④ Adjust the robot teaching pendant to manual teaching mode, adjust the robot movement rate to 30%, adjust the robot position so that the beam shaping process head moves to the position of the tooling surface, use a ruler to roughly measure the distance from the process head to the tooling surface, and compare it with the corresponding focusing distance. When the distance is close, use a vernier caliper to measure the focal length, adjust the robot movement rate to 1%, and accurately approach the focal length within ±1mm;

[0052] ⑤ For the end face of the high-strength steel bolt, place the part flat inside the tooling with lateral constraints, adsorb the dial indicator base on the flat part of the robot end effector, and execute the motion program to make the stylus gently scratch the surface of the high-strength steel bolt. Observe that the value jump range is within a reasonable range, and then end the clamping;

[0053] ⑥ For the bare rod part of the high-strength steel bolt, gently feed its clamping end into the three-jaw chuck on the turntable device, and slowly tighten the chuck with a special tool until it is tightened. Adsorb the magnetic base of the dial indicator on a nearby horizontal surface, adjust it until the needle touches the outer cylindrical surface of the bare rod high-strength steel bolt away from the clamping end, and adjust it to zero. Adjust the turntable to the handwheel mode, slowly turn the handwheel to rotate the high-strength steel bolt one circle, observe the indication range of the dial indicator needle, and adjust the installation angle of the high-strength steel bolt by loosening and tightening the chuck, installing the gasket, etc. according to the indication result of the dial indicator needle, and control the pointer jump to ≤0.1mm.

[0054] Example 1

[0055] The specific implementation method of preparing the laser phase change strengthening layer on the outer cylindrical surface and thread end surface of the polished rod of the high-strength alloy steel bolt is as follows:

[0056] Step 1: Process Preparation

[0057] 1. Before the laser phase change strengthening process begins, the parts should be kept at the same ambient temperature as the equipment for at least 4 hours.

[0058] 2. The material of the parts is 40CrNiMoA steel.

[0059] 3. Before the laser phase change strengthening process, the parts are in a quenched and tempered state with a hardness of HRC 31.5 to 45.

[0060] 4. Fiber lasers should be used preferentially. The laser phase change strengthening processing head should use a robot as a motion control device. Auxiliary motion devices such as turntables should be selected according to the geometric shape of the bolts. The auxiliary motion device should have external control capabilities and be controlled by the same host computer as the robot.

[0061] 5. To prevent the laser from directly radiating or being reflected or diffusely reflected by the workpiece onto the operator's body and eyes and causing harm, the processing site must be equipped with appropriate shielding devices.

[0062] 6. The laser phase change enhancement timing determines the path of the scanning beam on the surface of the processed workpiece, which can be aligned using the red light generated by a He-Ne laser or visible light generated by other devices.

[0063] Step 2: Processing

[0064] 1. The whole process of bolt processing is as follows Figure 3 As shown in the figure, the bolt laser phase transformation strengthening process diagram is as follows Figure 4 As shown:

[0065] 2. The surface of the bolt to be laser phase change strengthened is smooth and clean, with a roughness of not less than Ra0.4, and free of oxidation, stains, cracks and other defects that may affect the laser phase change strengthening effect.

[0066] 3. Use special tooling or adjustable shims to assist parts in clamping into place, and align and level them.

[0067] 4. Use the robot's built-in program for leveling, and use a dedicated tool to cross-check after leveling to ensure the uniformity of the spot size and energy distribution in the beam area. Under the guidance of the measuring tool, adjust the robot so that the focal length is accurately approached to within ±1mm.

[0068] 5. Using fiber laser, laser wavelength 1080±5nm, collimation focal length 150mm, focusing focal length 300mm, spot size 10×2mm.

[0069] 6. The laser phase change strengthening process parameters corresponding to the outer cylindrical surface of the polished rod are: laser power: 1000~1100W; travel speed: 1.7~1.9mm / s; rotation speed: F6000.

[0070] 7. The laser phase change strengthening process parameters corresponding to the thread end face are: laser power: 1000~1100W; travel speed: 8~9mm / s.

[0071] 8. As Figure 5 As shown in Figure 1, the laser phase transformation strengthening path of the thread end face adopts a reciprocating motion mode; Figure 6 As shown, the laser phase change strengthening path of the outer cylindrical surface of the optical rod adopts the mode of spiral motion.

[0072] 9. Start the laser, move forward from the starting point, use the long side of the light spot to scan the surface to be processed, and the scanning distance should be ≥80mm. Set the program command to turn off the laser after completing the unidirectional strengthening, adjust to the positioning red light, move horizontally to the third point, use the long side of the light spot to scan the surface to be processed in the reverse direction, and turn off the laser after the operation is completed.

Claims

1. A method for laser phase transformation strengthening of the surface of a high-strength alloy steel bolt, characterized in that: include: Cold working and heat treatment are performed on high-strength alloy steel materials to obtain bolts to be strengthened by laser phase transformation; Use special tooling or adjustable washers to assist in clamping the bolts into place, and align and level them; After leveling, use a special tooling to cross-check to ensure the uniformity of the spot size and energy distribution in the beam area; The outer circle of the bolt's polished rod and the threaded end face are laser phase transformation strengthened respectively.

2. The method according to claim 1, characterized in that The laser wavelength is 1080±5nm, the collimation focal length is 150mm, the focusing focal length is 300mm, and the spot size is 10×2mm.

3. The method according to claim 2, characterized in that The laser phase change strengthening process parameters corresponding to the outer cylindrical surface of the polished rod are: laser power: 1000-1100W; travel speed: 1.7-1.9mm / s; rotation speed: F6000; the laser phase change strengthening path adopts a spiral motion mode.

4. The method according to claim 3, characterized in that The laser phase change strengthening process parameters corresponding to the thread end face are: laser power: 1000-1100W; travel speed: 8-9mm / s; the laser phase change strengthening path adopts a reciprocating motion mode.

5. The method according to claim 1, characterized in that The requirements for the bolt surface to be laser phase transformation strengthened are: the surface is smooth and clean, the roughness is not less than Ra0.4, and there are no defects that may affect the laser phase transformation strengthening effect.

6. The method according to claim 1, characterized in that Before laser phase change strengthening, the method further comprises: performing process preparation; Process preparation includes: Before the laser phase change strengthening process begins, the bolts should be kept at the same ambient temperature as the laser used for laser phase change strengthening for at least 4 hours; The heat treatment state of the parts is quenched and tempered, with a hardness of HRC 31.5~45; During laser phase change strengthening, it is necessary to determine the path of the scanning beam on the surface of the workpiece being processed and use visible light for alignment.

7. The method according to claim 4, characterized in that Laser phase transformation strengthening is performed on the outer circle of the bolt's polished rod and the thread end face, including: Start the laser, move forward from the starting point, use the long side of the light spot to scan the outer circle of the polished rod or the end face of the thread, and the scanning distance is ≥80mm. Set the program command to turn off the laser after completing the unidirectional strengthening, adjust to the positioning red light, move horizontally to the third point, use the long side of the light spot to scan the outer circle of the polished rod or the end face of the thread in the opposite direction, and turn off the laser after the operation is completed.

8. The method according to claim 1, characterized in that The high-strength alloy steel is 40CrNiMoA steel.

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