Whether the bronze bushing can be repaired after wear mainly depends on the degree of wear, material properties and working conditions. For local slight wear (wear amount ≤ 0.1mm) or uniform wear (inner hole expansion ≤ 0.05mm), repair is more economical; but if there are serious cracks, fragmentation, and ablation (surface melting or oxide layer thickness > 0.1mm), it is recommended to replace it directly (the cost of repair may exceed that of a new part). The following are common repair methods and applicable scenarios:
一. Machining repair method (applicable to uniform wear or dimensional tolerance)
Removing the wear layer through cutting and restoring the inner hole size and precision of the bushing is the most commonly used repair method, especially suitable for bushings with sufficient wall thickness margin (remaining wall thickness ≥ 60% of the original wall thickness).
1. Boring + Honing Repair
Steps:
Use a horizontal boring machine or CNC lathe to bore the inner hole of the bushing to remove the wear layer (single-side removal of 0.03-0.1mm, and reserve 0.01-0.02mm honing margin).
Use a honing machine for precision honing (honing head particle size 800-1200 mesh) to make the inner hole surface roughness reach Ra0.8-Ra1.6μm, and the roundness error ≤0.005mm.
Advantages: The inner hole size can be accurately controlled (tolerance can reach H7 level), and the fit clearance is restored to the design value after repair (such as the original clearance 0.02-0.05mm).
Applicable scenarios: The sleeve is evenly worn (such as motor bearing sleeves, machine tool guide sleeves), and the seat hole is not loose.
2. Sleeve repair (for severe wear or too large inner hole)
Steps:
Bore the original sleeve to a larger size (such as φ50mm wear to φ50.5mm, boring to φ51mm), ensuring that the inner wall is smooth and free of defects.
Press in a thin-walled bronze sleeve (the material is the same as the original sleeve, the interference is 0.01-0.03mm), and then bore it to the designed size.
Advantages: The original design size can be restored to avoid replacing the seat hole (especially when the seat hole is cast iron or steel, saving costs).
Note: The sleeve wall thickness must be ≥2mm, otherwise it is easy to deform.
二. Surface repair method (applicable to local wear or scratches)
By filling the worn area or strengthening the surface, the matching accuracy of the bushing is restored, which is suitable for defects such as local depressions and scratches (depth ≤ 0.2mm).
1. Tin-bismuth alloy repair welding (for tin bronze bushings)
Principle: Tin bronze (such as ZCuSn10Pb1) has a high tin content, and can be welded at low temperature (temperature 350-450℃) with oxygen-acetylene flame, and tin-bismuth alloy (melting point 138℃) is used to fill the worn area.
Steps:
Grind the worn area with sandpaper, remove the oxide layer, and clean it with alcohol.
Flame heats the defect to 200-250℃, apply flux (such as rosin), melt the tin-bismuth alloy to fill the defect, and smooth it with a file after cooling.
Advantages: The welding temperature is low, which avoids the annealing of the bushing (the annealing temperature of bronze is usually >500℃), and does not affect the strength of the matrix.
Applicable scenarios: ZCuSn10Pb1, ZCuSn5Pb5Zn5 and other tin bronze bushings (tin content > 5%), such as local wear of gearbox bushings.
2. Brush plating repair (applicable to precision bushings)
Principle: Using electrolysis, a layer of copper alloy plating (such as Cu-Sn alloy) is deposited on the worn surface, and the thickness can be controlled at 0.01-0.1mm.
Steps:
Surface pretreatment: degreasing → pickling (5% dilute sulfuric acid) → activation (removal of oxide film).
Brush plating: Dip the plating pen into the plating solution (such as acidic copper sulfate solution) and move back and forth in the worn area. The current density is 10-20A/dm² to control the thickness of the plating.
Advantages: The bonding strength between the plating and the substrate is high (> 20MPa), and the dimensional accuracy can reach 0.001mm, which is suitable for precision matching scenarios (such as hydraulic valve bushings).
Limitation: The coating thickness is limited (>0.1mm is easy to peel), not suitable for heavy-duty conditions.
3. Laser cladding repair (for high-strength bronze bushings)
Principle: Use a laser beam to melt bronze powder (matching the base material, such as Cu-Al alloy powder for aluminum bronze) to form a cladding layer (thickness 0.1-1mm) on the worn surface.
Advantages: Small heat-affected zone (<0.5mm), no deformation, high hardness of the cladding layer (the hardness of aluminum bronze after cladding can reach HB200-250, 30% higher than the base).
Applicable scenarios: Local wear of high-strength bronze (such as ZCuAl10Fe3) bushings (such as excavator pin bushings), especially suitable for heavy-duty conditions.
三. Repair of wear caused by dry friction or poor lubrication (surface modification required)
If the bushing has adhesive wear due to dry friction (metal transfer marks on the surface), the surface lubrication performance needs to be enhanced after repair:
After repair, perform sulfidation treatment: put the bushing in a sodium sulfide solution (concentration 10%) and soak it at 80℃ for 2 hours to form a copper sulfide film (thickness 0.005-0.01mm) on the surface, reducing the friction coefficient (from 0.15 to 0.08).
For bushings with high frequency movement (such as punch slider bushings), an oil storage tank (width 2mm× depth 0.5mm) can be opened in the inner hole after repair to enhance the lubrication effect.
四. Verification after repair
No matter which method is used, the following tests are required after repair:
Dimensional accuracy: The inner hole diameter tolerance must meet the design requirements (such as H7 grade), and the clearance with the shaft is 0.01-0.05mm (adjusted according to the speed, the high-speed shaft takes a small clearance).
Surface quality: no cracks, pores, roughness ≤Ra1.6μm (detected by a roughness meter).
Load test: For heavy-load bushings (such as crane drum bushings), a 1.2 times rated load test is required for 1 hour, with no abnormal wear.
Summary
The feasibility of repairing bronze bushings depends on the degree of wear: minor wear is preferably treated with machining or brush plating; local defects can be repaired with welding or laser cladding; severe wear is recommended to be replaced. When repairing, attention should be paid to matching materials (such as tin bronze to avoid high-temperature repair), and lubrication should be strengthened in combination with working conditions to extend the secondary service life.
Whether the bronze bushing can be repaired after wear mainly depends on the degree of wear, material properties and working conditions. For local slight wear (wear amount ≤ 0.1mm) or uniform wear (inner hole expansion ≤ 0.05mm), repair is more economical; but if there are serious cracks, fragmentation, and ablation (surface melting or oxide layer thickness > 0.1mm), it is recommended to replace it directly (the cost of repair may exceed that of a new part). The following are common repair methods and applicable scenarios:
一. Machining repair method (applicable to uniform wear or dimensional tolerance)
Removing the wear layer through cutting and restoring the inner hole size and precision of the bushing is the most commonly used repair method, especially suitable for bushings with sufficient wall thickness margin (remaining wall thickness ≥ 60% of the original wall thickness).
1. Boring + Honing Repair
Steps:
Use a horizontal boring machine or CNC lathe to bore the inner hole of the bushing to remove the wear layer (single-side removal of 0.03-0.1mm, and reserve 0.01-0.02mm honing margin).
Use a honing machine for precision honing (honing head particle size 800-1200 mesh) to make the inner hole surface roughness reach Ra0.8-Ra1.6μm, and the roundness error ≤0.005mm.
Advantages: The inner hole size can be accurately controlled (tolerance can reach H7 level), and the fit clearance is restored to the design value after repair (such as the original clearance 0.02-0.05mm).
Applicable scenarios: The sleeve is evenly worn (such as motor bearing sleeves, machine tool guide sleeves), and the seat hole is not loose.
2. Sleeve repair (for severe wear or too large inner hole)
Steps:
Bore the original sleeve to a larger size (such as φ50mm wear to φ50.5mm, boring to φ51mm), ensuring that the inner wall is smooth and free of defects.
Press in a thin-walled bronze sleeve (the material is the same as the original sleeve, the interference is 0.01-0.03mm), and then bore it to the designed size.
Advantages: The original design size can be restored to avoid replacing the seat hole (especially when the seat hole is cast iron or steel, saving costs).
Note: The sleeve wall thickness must be ≥2mm, otherwise it is easy to deform.
二. Surface repair method (applicable to local wear or scratches)
By filling the worn area or strengthening the surface, the matching accuracy of the bushing is restored, which is suitable for defects such as local depressions and scratches (depth ≤ 0.2mm).
1. Tin-bismuth alloy repair welding (for tin bronze bushings)
Principle: Tin bronze (such as ZCuSn10Pb1) has a high tin content, and can be welded at low temperature (temperature 350-450℃) with oxygen-acetylene flame, and tin-bismuth alloy (melting point 138℃) is used to fill the worn area.
Steps:
Grind the worn area with sandpaper, remove the oxide layer, and clean it with alcohol.
Flame heats the defect to 200-250℃, apply flux (such as rosin), melt the tin-bismuth alloy to fill the defect, and smooth it with a file after cooling.
Advantages: The welding temperature is low, which avoids the annealing of the bushing (the annealing temperature of bronze is usually >500℃), and does not affect the strength of the matrix.
Applicable scenarios: ZCuSn10Pb1, ZCuSn5Pb5Zn5 and other tin bronze bushings (tin content > 5%), such as local wear of gearbox bushings.
2. Brush plating repair (applicable to precision bushings)
Principle: Using electrolysis, a layer of copper alloy plating (such as Cu-Sn alloy) is deposited on the worn surface, and the thickness can be controlled at 0.01-0.1mm.
Steps:
Surface pretreatment: degreasing → pickling (5% dilute sulfuric acid) → activation (removal of oxide film).
Brush plating: Dip the plating pen into the plating solution (such as acidic copper sulfate solution) and move back and forth in the worn area. The current density is 10-20A/dm² to control the thickness of the plating.
Advantages: The bonding strength between the plating and the substrate is high (> 20MPa), and the dimensional accuracy can reach 0.001mm, which is suitable for precision matching scenarios (such as hydraulic valve bushings).
Limitation: The coating thickness is limited (>0.1mm is easy to peel), not suitable for heavy-duty conditions.
3. Laser cladding repair (for high-strength bronze bushings)
Principle: Use a laser beam to melt bronze powder (matching the base material, such as Cu-Al alloy powder for aluminum bronze) to form a cladding layer (thickness 0.1-1mm) on the worn surface.
Advantages: Small heat-affected zone (<0.5mm), no deformation, high hardness of the cladding layer (the hardness of aluminum bronze after cladding can reach HB200-250, 30% higher than the base).
Applicable scenarios: Local wear of high-strength bronze (such as ZCuAl10Fe3) bushings (such as excavator pin bushings), especially suitable for heavy-duty conditions.
三. Repair of wear caused by dry friction or poor lubrication (surface modification required)
If the bushing has adhesive wear due to dry friction (metal transfer marks on the surface), the surface lubrication performance needs to be enhanced after repair:
After repair, perform sulfidation treatment: put the bushing in a sodium sulfide solution (concentration 10%) and soak it at 80℃ for 2 hours to form a copper sulfide film (thickness 0.005-0.01mm) on the surface, reducing the friction coefficient (from 0.15 to 0.08).
For bushings with high frequency movement (such as punch slider bushings), an oil storage tank (width 2mm× depth 0.5mm) can be opened in the inner hole after repair to enhance the lubrication effect.
四. Verification after repair
No matter which method is used, the following tests are required after repair:
Dimensional accuracy: The inner hole diameter tolerance must meet the design requirements (such as H7 grade), and the clearance with the shaft is 0.01-0.05mm (adjusted according to the speed, the high-speed shaft takes a small clearance).
Surface quality: no cracks, pores, roughness ≤Ra1.6μm (detected by a roughness meter).
Load test: For heavy-load bushings (such as crane drum bushings), a 1.2 times rated load test is required for 1 hour, with no abnormal wear.
Summary
The feasibility of repairing bronze bushings depends on the degree of wear: minor wear is preferably treated with machining or brush plating; local defects can be repaired with welding or laser cladding; severe wear is recommended to be replaced. When repairing, attention should be paid to matching materials (such as tin bronze to avoid high-temperature repair), and lubrication should be strengthened in combination with working conditions to extend the secondary service life.
