SAE J527 Copper-Plated Bundy Tube with 4.76-12.7 mm Outer Diameter for Brake Line Applications
SAE J527 Bundy Tube Double-Layer Copper-Plated Low-Carbon Steel Tube for Brake Line
Material
SAE J527 double-layer copper-plated low-carbon steel tube, commonly known as Bundy tube, is a precision-formed, copper-brazed steel tubing product used in brake, fuel, hydraulic, and refrigeration systems. SAE J527 covers brazed double-wall low-carbon steel tubing for applications that require reliable bending, flaring, beading, forming, and brazing, while ASTM A254 covers the closely related double-wall copper-brazed steel tubing widely used in automotive and refrigeration service.
Specifications
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Structure: Double-wall rolled and copper-brazed low-carbon steel tube
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Base material: Cold-rolled low-carbon copper-coated steel strip
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Outer diameter range: 4.76-12.7 mm
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Main outer diameters: 4.76, 6.00, 6.35, 8.00, 9.52, 10.00, 12.70 mm
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Common wall thicknesses: 0.50, 0.60, 0.70, 0.80, 1.00, 1.20 mm
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Wall thickness tolerance: typically around ±0.05 mm in precision production
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Supply condition: Fully annealed for bending and secondary forming
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Optional surface finishes: Copper-plated, zinc-coated, PVF-coated, or other corrosion-protection finishes
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Supply form: Coils, straight lengths, or cut-to-length assemblies
Main Features
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360° circumferential brazed bonding for stable sealing performance and high structural integrity
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Double-wall construction for higher burst resistance and better vibration durability than ordinary single-wall welded tubing
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Very clean inner surface, with lubricant residue controlled below 0.05 g/m² in the PPT process description
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High dimensional accuracy and good concentricity for precision assembly
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Full annealing for excellent bendability, flareability, and formability in brake-line routing
Our Advantages
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Safer sealing for brake-line service
hidden leakage points. This tube uses a double-wall rolled structure with full circumferential copper brazing rather than a simple single seam, which improves wall integrity and sealing reliability in hydraulic brake applications. -
Easier installation in complex chassis layouts
whether the tube will crack or wrinkle during bending and flaring. The fully annealed condition, low-carbon substrate, and formability-focused SAE J527 scope make it suitable for routing through tight installation spaces while maintaining good processing performance. -
Cleaner and more durable fluid delivery
For brake, fuel, and hydraulic lines, internal cleanliness and corrosion control matter as much as strength. The PPT specifies inner-surface residue below 0.05 g/m², and the tube can be supplied with zinc, PVF, or similar protective coatings for improved underbody corrosion resistance.
Chemical Composition
| Reference Grade | Standard Reference | C (%) | Mn (%) | P (%) | S (%) | Si (%) |
|---|---|---|---|---|---|---|
| DC01 | EN 10130 | ≤0.12 | ≤0.60 | ≤0.045 | ≤0.045 | — |
| DC03 | EN 10130 | ≤0.10 | ≤0.45 | ≤0.035 | ≤0.035 | — |
| 10# | GB/T 699 | 0.07-0.13 | 0.35-0.65 | ≤0.035 | ≤0.035 | 0.17-0.37 |
| SAE 1008 | SAE/AISI reference | ≤0.10 | 0.30-0.50 | ≤0.04 | ≤0.05 | — |
| SAE 1010 | SAE/AISI reference | 0.08-0.13 | 0.30-0.60 | ≤0.04 | ≤0.05 | — |
Mechanical Properties
| Reference Grade | Tensile Strength (MPa) | Yield Strength (MPa) | Elongation (%) | Hardness |
|---|---|---|---|---|
| DC01 | 270-410 | ≥280 | ≥28 | HV 105 |
| DC03 | 270-370 | ≥240 | ≥34 | HV 100 |
| 10# | ≥335 | ≥205 | ≥31 | ≤137 HB |
| SAE 1008 | 300-360 | 180-300 | 20 | HB 95 |
| SAE 1010 | 365 | 305 | 20 | HB 105 |
Standards
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SAE: SAE J527 — brazed double-wall low-carbon steel tubing for automotive, refrigeration, hydraulic, and related applications requiring bending, flaring, beading, forming, and brazing.
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ASTM: ASTM A254/A254M — double-wall copper-brazed steel tubing for fuel lines, brake lines, oil lines, and heating/cooling service.
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EN / DIN: DIN 74234 — brake pipes and flares for hydraulic braking systems; covers dimensions, materials, and requirements for brake-pipe service.
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JASO / Japanese automotive reference: JASO M101:2022 — metal pipes for automobile tubing used for brake, fuel, and lubrication purposes.
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GB: GB/T 34020.2-2017 — double-wall copper-brazed steel tubes for automotive tubing systems, including dimensions, tolerances, technical requirements, test methods, and inspection rules.
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GOST: GOST 11249-80 — steel rolled-up soldered double-layer tubes for hydraulic systems, automobiles, and household refrigeration service.
Application Fields
This product is mainly used in automotive brake systems, fuel and hydraulic tubing systems, refrigeration equipment, and compact heat-transfer assemblies where pressure resistance, clean internal surface, good bendability, and stable dimensional control are required.
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Brake lines: Hydraulic brake pipes between the master cylinder, ABS unit, and wheel-end braking assemblies
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Fuel lines: Low-pressure fuel delivery tubing with good sealing and internal cleanliness
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Hydraulic lines: Power steering, transmission, and medium-pressure fluid transfer circuits
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Refrigeration tubing: Condensers, evaporators, anti-condensation loops, and air-conditioning connector tubes
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Industrial equipment: Hydraulic devices, engineering machinery, and heater assemblies requiring vibration resistance and compact routing
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