Surface strengthening fixture and method for titanium alloy support parts

Abstract

The present invention belongs to the field of methods for surface strengthening of parts, and relates to fixtures and methods for surface strengthening of titanium alloy support parts. The present invention utilizes a special fixture for positioning, fixing and clamping to ensure that the parts are accurately positioned and firmly clamped during the strengthening process; utilizes the configured titanium alloy cleaning fluid to clean the laser shock strengthened surface of the parts, removes dirt contaminated during the parts processing process, and ensures the laser shock strengthening effect; utilizes a special strengthening process to obtain the required surface residual pressure value and stress layer depth. The laser shock strengthening method used in the present invention effectively prevents cracks in the material and effectively inhibits crack propagation. The present invention can strengthen the surface of a plane or a regular rotating body, and can also strengthen irregular surfaces, and can accurately cover the surface of the parts. The present invention can better ensure the surface roughness and dimensional accuracy of the parts, and the operator has low labor intensity, high efficiency, and good safety.

Description

Technical Field

[0001] The invention belongs to the field of methods for strengthening the surface of parts, and relates to a fixture and method for strengthening the surface of titanium alloy support parts. Background Art

[0002] The support parts are machined from titanium alloy die forgings and consist of lugs, irregular octagonal webs, vertical plates, flanges, and reinforcing ribs. To improve fatigue resistance and service life, enhance resistance to external damage, prevent crack initiation, and reduce stress corrosion cracking, stress concentration areas such as the flat surfaces on both sides of the lugs and the filleted corners on the vertical plates need to be reinforced.

[0003] Currently, mechanical shot peening is commonly used in China to strengthen the surface of parts. This process uses steel balls to impact the metal surface at high speed, causing plastic deformation upon impact, thereby achieving the desired surface strengthening. However, mechanical shot peening cannot precisely control coverage, consumes a lot of energy, and produces a residual stress layer depth of only 0.1mm to 0.2mm. Surface roughness and dimensional accuracy cannot be guaranteed, and the operator is labor-intensive and inefficient. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a surface strengthening fixture and method for titanium alloy support parts. The present invention adopts laser shot peening (also known as laser shock strengthening) to strengthen the surface of the parts; uses a configured titanium alloy cleaning fluid to clean the laser shock strengthened surface of the parts; and uses a designed special tooling fixture to clamp the parts to ensure the stability of the parts during the strengthening process and the dimensional accuracy of the strengthened area.

[0005] The specific technical solutions of the present invention are as follows:

[0006] A surface strengthening fixture for titanium alloy support parts comprises: a base plate 1, a pressure plate 2, a fastening bolt 3, a connecting hole 4, and a lifting ring 5.

[0007] The base plate 1 is designed with a lower limit groove according to the shape of the web of the support part to be surface-strengthened, which plays the role of supporting the part and positioning. Threaded holes and connecting holes 4 are drilled on the upper surface of the base plate 1. The threaded holes are used to install fastening bolts 3, and the connecting holes 4 are used to connect the fixture to the robotic arm, thereby realizing the overall movement of the fixture and the support part; four threaded holes are provided on the side surface of the base plate 1 for fixing the lifting ring 5.

[0008] The pressing plate 2 is placed on the base plate 1 , and after the support parts are placed in the lower limit groove, the parts are fixed on the base plate 1 through the pressing plate 2 and the fastening bolts 3 .

[0009] The set bolts 3 are used to fix parts.

[0010] The lifting ring 5 is used for lifting the clamp.

[0011] Furthermore, the base plate 1 and the pressure plate 2 are made of aluminum alloy to reduce the weight of the fixture, enable the robot arm to operate better, and prevent wear on the parts when the tooling is clamped.

[0012] Furthermore, the fastening bolt 3 is made of stainless steel.

[0013] Furthermore, the lifting ring 5 is made of carbon steel.

[0014] A method for using a surface strengthening fixture for titanium alloy support parts, the specific method is as follows:

[0015] 1) Factory acceptance: Check the surface quality of the parts. There should be no fingerprints, oil, water, bumps, scratches and other contaminants on the surface. The surface roughness of the laser shock peening area should be Ra3.2μm.

[0016] 2) Cleaning: Use an ultrasonic cleaner with the supplied cleaning fluid at a temperature of 55°C to 60°C and an ultrasonic output frequency of 25kHz to 27kHz for 15 to 30 minutes. After cleaning, rinse in warm water at 40°C to 60°C for approximately 5 minutes and then dry with a clean white cotton cloth. Acetone may be used to clean the laser shock peening area a second time.

[0017] The ratio of special cleaning fluid is as follows:

[0018] ①Sodium hydroxide (NaOH) 5g / L~8g / L

[0019] ②Sodium phosphate (Na3PO4) 40g / L~60g / L

[0020] ③Sodium carbonate (Na3CO3) 20g / L~30g / L

[0021] ④ Water glass (Na3O·nSiO2) 30g / L~35g / L

[0022] ⑤The rest is deionized water

[0023] 3) Applying aluminum foil tape: Apply two layers of aluminum foil tape to the reinforced area of the part. Ensure the surface of the aluminum foil tape is firmly adhered and smooth, with no bubbles, wrinkles, obvious scratches, or damage. The adhesive coverage area should extend at least 5mm beyond the boundary of the reinforced area.

[0024] 4) Parts clamping: First, install the tooling base 1 on the manipulator using the mounting hole 4. Then place the support part with the web facing downward in the lower limit groove of the base 1. Place the four pressure plates 2 in the designated positions and tighten them with bolts 3 to ensure that the parts are firm.

[0025] 5) Robot path trajectory program setting

[0026] The laser path is set according to the laser shock strengthening area of the part, and the center spacing of adjacent spots is set to 1.7mm to 2.1mm to ensure that the spot overlap rate is 40% to 50%.

[0027] 6) Constraint layer preparation

[0028] Adjust the position of the water nozzle so that the water can flow evenly in the position to be strengthened. Use deionized water to ensure that the conductivity is ≤1μs / cm or the resistivity is ≥1MΩ·cm. The thickness of the water flow layer is about 1mm to 1.5mm.

[0029] 7) Laser shock peening

[0030] Start the pulse width of the strengthening device at 15ns, set the laser pulse energy to 26J, and the spot size φ

[0031] 4.2mm. In circular spot mode, perform laser shock peening along the path set in step 5), recording the actual output pulse energy. The operator monitors the pulse energy and robot's operating posture throughout the process. If any abnormalities are detected in the absorption layer or the constraint layer, the machine must be stopped immediately for processing and recorded.

[0032] The laser shock peening process parameters are as follows:

[0033] ①Laser pulse energy: 26J±2J;

[0034] ②Pulse width: 15ns±3ns;

[0035] ③Spot size: φ4.2mm±0.5mm;

[0036] ④ Overlap rate: 40% to 50%;

[0037] ⑤Number of impacts: 2 times;

[0038] ⑥ Constraint layer: deionized water, thickness 1mm~1.5mm;

[0039] ⑦Sacrificial layer: aluminum foil tape, thickness 140μm±10μm;

[0040] ⑧ To ensure the light spot coverage rate in the R corner area, the number of light spot rows at the R corner should be determined according to the light spot diameter and the R angle size.

[0041] Number of light spot rows Where R is the rounded corner, D is the spot diameter, and θ is the angle between the two sides of the R corner.

[0042] 8) Aluminum foil appearance inspection

[0043] Observe the overlap of the light spots on the aluminum foil to ensure full coverage of the reinforced area and record the light spot coverage. If there are any missed reinforcements or incomplete coverage, additional reinforcements are required and the reinforcement results are recorded.

[0044] 9) Surface cleaning

[0045] Remove the part from the fixture and place it on the workbench. Remove the aluminum foil tape from the part and clean the surface with clean cotton wool dipped in alcohol. If any burnishing is found in the reinforced area or adjacent areas, use a rubber sander or scouring pad to remove it.

[0046] 10) Repeat steps 3) to 9) to perform secondary laser shock peening.

[0047] 11) Inspection

[0048] Visually inspect the surface of the parts: ensure that there are no signs of ablation on the reinforced surface, but signs of grinding with a rubber grinding head or scouring pad are allowed.

[0049] The beneficial effects of the present invention are as follows: the present invention provides a surface strengthening transposition and method for titanium alloy support parts, using a special fixture for positioning, fixing and clamping to ensure that the parts are accurately positioned and firmly clamped during the strengthening process; using the configured titanium alloy cleaning fluid to clean the laser shock strengthened surface of the parts, remove the dirt contaminated during the parts processing, and ensure the laser shock strengthening effect; using a special strengthening process to obtain the required surface residual pressure value and stress layer depth. The laser shock strengthening method used in the present invention effectively prevents the material from cracking and effectively inhibits crack propagation. The surface residual compressive stress value is ≥400MPa, and the residual compressive stress layer depth reaches ≥1mm. The present invention can strengthen the surface of a plane or a regular rotating body, and can also strengthen irregular surfaces, and can accurately cover the surface of the parts. The present invention can better ensure the surface roughness and dimensional accuracy of the parts, and the operator has low labor intensity, high efficiency and good safety. The invented fixture structure is practical, accurate in positioning, firm in clamping, and easy to process and manufacture. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a schematic diagram of the support parts.

[0051] Figure 2(a), Figure 2(b) and Figure 2(c) are schematic diagrams of parts and tooling installation, where: Figure 2(a) is a front view, Figure 2(b) is a side view, and Figure 2(c) is a top view.

[0052] Figure 3 It is a schematic diagram of the fixture.

[0053] Figure 4 This is a schematic diagram of the overall layout of the laser shock peening equipment.

[0054] In the figure: 1 base plate; 2 pressure plate; 3 fastening bolts; 4 connecting holes; 5 lifting rings. DETAILED DESCRIPTION

[0055] The specific embodiments of the present invention are further described in detail below with reference to the accompanying drawings:

[0056] Example: Method for using the surface strengthening fixture for titanium alloy support parts

[0057] like Figure 3 As shown in FIG, a surface strengthening fixture for titanium alloy support parts includes: a base 1, a pressure plate 2, a fastening bolt 3, a connecting hole 4, and a lifting ring 5. The structure of the support parts is as follows Figure 1 As shown, the parts and tooling are installed as shown in Figure 2(a), Figure 2(b), and Figure 2(c).

[0058] The base plate 1 is designed with a lower limit groove according to the shape of the web of the support part to be surface-strengthened, which plays the role of supporting the parts and positioning. There are four base plates 1, and threaded holes and connecting holes 4 are drilled on the upper surface. The threaded holes are used to install fastening bolts 3, and the connecting holes 4 are used to connect the fixture to the robotic arm, thereby realizing the overall movement of the fixture and the support part; four threaded holes are provided on the side surface of the base plate 1 for fixing the lifting ring 5.

[0059] The method of using the surface strengthening fixture of titanium alloy support parts is as follows:

[0060] 1) Factory acceptance: Check the surface quality of the parts. There should be no fingerprints, oil, water, bumps, scratches and other contaminants on the surface. The surface roughness of the laser shock peening area should be Ra3.2μm.

[0061] 2) Cleaning: Use an ultrasonic cleaner with the supplied cleaning fluid at a temperature of 55°C to 60°C and an ultrasonic output frequency of 25kHz to 27kHz for 15 to 30 minutes. After cleaning, rinse in warm water at 40°C to 60°C for approximately 5 minutes and then dry with a clean white cotton cloth. Acetone may be used to clean the laser shock peening area a second time.

[0062] Configuration of special cleaning fluid:

[0063] Before laser shock peening, the parts are already in the finished state, and cleaning solvents are required to remove cutting fluids, oils and other dirt on the surface of the parts to ensure that the water layer on the surface of the laser shock peening can flow continuously and evenly. The cleaning solvent ratio is as follows:

[0064] ①Sodium hydroxide (NaOH) 5g / L~8g / L

[0065] ②Sodium phosphate (Na3PO4) 40g / L~60g / L

[0066] ③Sodium carbonate (Na3CO3) 20g / L~30g / L

[0067] ④ Water glass (Na3O·nSiO2) 30g / L~35g / L

[0068] ⑤The rest is deionized water

[0069] 3) Applying aluminum foil tape: Apply two layers of aluminum foil tape to the reinforced area of the part. Ensure the surface of the aluminum foil tape is firmly adhered and smooth, with no bubbles, wrinkles, obvious scratches, or damage. The adhesive coverage area should extend at least 5mm beyond the boundary of the reinforced area.

[0070] 4) Parts clamping: such as Figure 3 As shown, first install the tooling base plate 1 on the manipulator using the mounting hole 4, then place the support part with the web facing downward in the lower limit groove of the base plate 1, place the four pressure plates 2 in the designated positions, and tighten them with bolts 3 to ensure that the parts are firm.

[0071] 5) Robot path trajectory program setting

[0072] The laser path is set according to the laser shock peening area of the part, and the center spacing of adjacent spots is set to 1.7mm to 2.1mm (the common value is 2mm) to ensure that the spot overlap rate is 40% to 50%.

[0073] 6) Constraint layer preparation

[0074] Adjust the position of the water nozzle so that the water can flow evenly in the position to be strengthened. Use deionized water to ensure that the conductivity is ≤1μs / cm or the resistivity is ≥1MΩ·cm. The thickness of the water flow layer is about 1mm to 1.5mm.

[0075] 7) Laser shock peening

[0076] Start the pulse width of the strengthening device at 15ns, set the laser pulse energy to 26J, and the spot size φ

[0077] 4.2mm. In circular spot mode, perform laser shock peening along the path set in step 5), recording the actual output pulse energy. The operator monitors the pulse energy and robot's operating posture throughout the process. If any abnormalities are detected in the absorption layer or the constraint layer, the machine must be stopped immediately for processing and recorded.

[0078] The overall layout of the laser shock peening equipment is as follows Figure 4 As shown, the laser shock peening process:

[0079] In order to obtain the required compressive stress and desired performance on the laser shock peening surface, the laser shock peening process parameters for titanium alloy support parts are as follows:

[0080] ①Laser pulse energy: 26J±2J;

[0081] ②Pulse width: 15ns±3ns;

[0082] ③Spot size: φ4.2mm±0.5mm;

[0083] ④ Overlap rate: 40% to 50%;

[0084] ⑤Number of impacts: 2 times;

[0085] ⑥ Constraint layer: deionized water, thickness 1mm~1.5mm;

[0086] ⑦Sacrificial layer: aluminum foil tape, thickness 140μm±10μm;

[0087] ⑧ To ensure the light spot coverage rate in the R corner area, the number of light spot rows at the R corner should be determined according to the light spot diameter and the R angle size.

[0088] Number of light spot rows Where R is the rounded corner, D is the spot diameter, and θ is the angle between the two sides of the R corner.

[0089] 8) Aluminum foil appearance inspection

[0090] Observe the overlap of the light spots on the aluminum foil to ensure full coverage of the reinforced area and record the light spot coverage. If there are any missed reinforcements or incomplete coverage, additional reinforcements are required and the reinforcement results are recorded.

[0091] 9) Surface cleaning

[0092] Remove the part from the fixture and place it on the workbench. Remove the aluminum foil tape from the part and clean the surface with clean cotton wool dipped in alcohol. If any burnishing is found in the reinforced area or adjacent areas, use a rubber sander or scouring pad to remove it.

[0093] 10) Repeat steps 3) to 9) to perform secondary laser shock peening.

[0094] 11) Inspection

[0095] Visually inspect the surface of the parts: ensure that there are no signs of ablation on the reinforced surface, but signs of grinding with a rubber grinding head or scouring pad are allowed.

Claims

1. A method for surface strengthening of titanium alloy support parts, characterized in that: The surface strengthening fixture of titanium alloy support parts is used, and the fixture comprises a base plate (1), a pressure plate (2), a fixing bolt (3), a connecting hole (4), and a lifting ring (5); The bottom plate (1) is designed with a lower limit groove according to the shape of the web of the support part to be surface-strengthened, which plays the role of supporting the part and positioning. The upper surface of the bottom plate (1) is drilled with threaded holes and connecting holes (4). The threaded holes are used to install the fastening bolts (3), and the connecting holes (4) are used to connect the fixture to the robot arm, thereby realizing the overall movement of the fixture and the support part; the side surface of the bottom plate (1) is provided with four threaded holes for fixing the lifting ring (5); The pressing plate (2) is placed on the base plate (1), and after the support parts are placed in the lower limit groove, the parts are fixed on the base plate (1) through the pressing plate (2) and the fastening bolts (3); The fixing bolts (3) are used to fix parts; The lifting ring (5) is used for lifting the tooling; The method described is as follows: 1) Factory acceptance: Check the surface quality of the parts. There should be no fingerprints, oil, water, bumps, scratches and other contaminants on the surface. The surface roughness of the laser shock peening area should be Ra3.2μm. 2) Cleaning: Use the configured special cleaning fluid to clean the parts in an ultrasonic cleaning machine at a temperature of 55℃~60℃, an ultrasonic output frequency of 25kHz~27kHz, and a cleaning time of 15min~30min. After cleaning, rinse in warm water at 40℃~60℃ for 5min and wipe dry with a clean white cotton cloth. Use acetone to scrub the laser shock peening area a second time. The ratio of special cleaning fluid is as follows: ①Sodium hydroxide 5g / L~8g / L ②Sodium phosphate 40g / L~60g / L ③Sodium carbonate 20g / L~30g / L ④ Water glass 30g / L~35g / L ⑤The rest is deionized water 3) Attach aluminum foil tape: Attach two layers of aluminum foil tape to the reinforced area of the part. After attachment, the surface of the aluminum foil tape should be tightly adhered and smooth, without bubbles, wrinkles, obvious scratches, or damage. The attached coverage area should extend at least 5mm beyond the boundary of the reinforced area. 4) Parts clamping: First, install the tooling base plate (1) on the manipulator using the mounting hole (4), then place the support part with the web facing downward in the lower limit groove of the base plate (1), place the four pressing plates (2) in the designated positions, and tighten them with bolts (3) to ensure that the parts are firmly fixed; 5) Robot path trajectory program setting The laser path is set according to the laser shock peening area of the part, and the center spacing of adjacent spots is set to 1.7mm to 2.1mm to ensure that the spot overlap rate is 40% to 50%; 6) Constraint layer preparation Adjust the position of the water nozzle so that the water can flow evenly in the area to be strengthened. Use deionized water to ensure that the conductivity is ≤1μs / cm or the resistivity is ≥1MΩ·cm. The thickness of the water layer is 1mm to 1.5mm. 7) Laser shock peening Start the peening equipment with a pulse width of 15 ns, set the laser pulse energy to 26 J, and the spot size to φ4.2 mm. Perform laser shock peening in circular spot mode along the path set in step 5), and record the actual output pulse energy. The operator monitors the pulse energy and the robot's operating posture throughout the process. If any abnormality is found in the absorption layer or the constraint layer, the machine must be stopped immediately for processing and recorded. The laser shock peening process parameters are as follows: ①Laser pulse energy: 26J±2J; ②Pulse width: 15ns±3ns; ③Spot size: φ4.2mm±0.5mm; ④ Overlap rate: 40% to 50%; ⑤Number of impacts: 2 times; ⑥ Constraint layer: deionized water, thickness 1mm~1.5mm; ⑦Sacrificial layer: aluminum foil tape, thickness 140μm±10μm; ⑧To ensure the spot coverage rate in the R corner area, the number of spot rows at the R corner should be determined according to the spot diameter and the R angle size; Number of light spot rows Where R is the rounded corner, D is the spot diameter, and θ is the angle between the two sides of the R corner; 8) Aluminum foil appearance inspection Observe the overlap of the light spots on the aluminum foil to ensure full coverage of the enhanced area and record the light spot coverage. If there is any missed enhancement or incomplete coverage, additional enhancement is required and the enhancement status should be recorded. 9) Surface cleaning Remove the part from the fixture and place it on the workbench; remove the aluminum foil tape from the part and clean the surface of the part with clean cotton yarn dipped in alcohol; if ablation is found in the reinforced area or adjacent areas, use a rubber grinding head or scouring pad to grind and remove it; 10) Repeat steps 3) to 9) to perform secondary laser shock peening; 11) Inspection Visually inspect the surface of the parts: ensure that there are no signs of ablation on the reinforced surface, but signs of grinding with a rubber grinding head or scouring pad are permitted.

2. The method for surface strengthening of titanium alloy support parts according to claim 1, characterized in that: The base plate (1) and the pressing plate (2) are made of aluminum alloy material.

3. The surface strengthening method of titanium alloy support parts according to claim 1, characterized in that: The fastening bolt (3) is made of stainless steel.

4. The method for surface strengthening of titanium alloy support parts according to claim 1, characterized in that: The hanging ring (5) is made of carbon steel.

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