C68700 Brass

Grade Name

Item	Specification
UNS Number	C68700
Chinese Designation	HAl77-2 (YS/T 649-2018)
European Standard	CuZn20Al2 (DIN 17660)
Common Name	Arsenical Aluminum Brass, Naval Aluminum Brass
Primary Standards	ASTM B111M, YS/T 649-2018, DIN 17672

Product Features

Exceptional Corrosion Resistance: Arsenic (As) inhibits dezincification (salt spray >720 hours with coating).
High Strength-Ductility Balance: Annealed tensile strength ≥360 MPa, elongation ≥50%; hardened strength up to 600 MPa.
Optimized Cold Workability: Cold deformation rate ≤80%, suitable for deep drawing/flaring.
Thermal Conductivity: 109 W/(m·K), electrical conductivity 28% IACS, ideal for heat exchange systems.
Environmental Safety: As ≤0.10%, compliant with REACH industrial exemptions for cooling water systems.

Common Product Forms & Dimensions

Form	Thickness/Dia. (mm)	Width/Length (mm)	Special Specifications
Tube	Wall: 0.15–10.0	OD: 3.0–260	Seamless/Welded condenser tubes (0.5–25m)
Bar	Φ3–200	Cut-to-length: 0.5–6m	Hex/Square/Forged rounds
Plate	0.5–80	1000–6000 (L) ×500–3000 (W)	Max. single plate: 5 tons
Strip	0.08–2.5	Coil width: 10–600	Slitting tolerance ±0.1mm

Note: Custom profiles available (MOQ: 500kg).

Chemical Composition

Element	Standard Range (wt%)	Typical (wt%)	Function
Cu	76.0–79.0	77.5	Matrix, ensures conductivity
Al	1.8–2.5	2.2	Enhances strength & atmospheric corrosion resistance
As	0.02–0.10	0.06	Suppresses dezincification
Zn	Balance	20.0	Improves fluidity, reduces cost
Fe	≤0.06	0.03	Refines grain structure
Pb	≤0.07	0.02	Enhances machinability
Total Impurities	≤0.30	0.15	Sn≤0.05%, Sb≤0.005% strictly controlled

Physical Properties

Property	Value	Test Condition
Density (g/cm³)	8.40	20°C
Melting Point (°C)	900–930	–
Thermal Conductivity (W/(m·K))	109	20°C
Electrical Conductivity (%IACS)	28	Annealed
Thermal Expansion (×10⁻⁶/K)	20.2	20–300°C
Elastic Modulus (GPa)	117	–

*Data per ASTM B193/E1225; values vary with processing.*

Mechanical Properties

Condition	Tensile Strength (MPa)	Yield Strength (MPa)	Elongation (%)	Hardness (HRB)
Annealed (O)	360 [340–380]	80 [70–90]	50 [45–55]	60 [55–65]
¼ Hard (H02)	450 [430–480]	250 [230–270]	25 [20–30]	100 [90–110]
Hard (H04)	600 [580–620]	540 [520–560]	10 [8–12]	175 [170–180]
Hot Rolled	550 [530–570]	350 [330–370]	20 [15–25]	120 [110–130]

Tube properties per ASTM B111 (min. wall thickness 0.5mm).

Core Advantages

1. Marine Corrosion Benchmark: Dezincification rate <0.1 mm/year (ASTM G48 seawater), service life >15 years.

2. Heat Exchange Efficiency: Condenser tube heat transfer coefficient ≥5200 W/m²·K, 30% higher than stainless steel.

3. Forming Adaptability: Cold bending radius ≥2× wall thickness; compatible with Ag/Cu-P brazing.

4. Cost Efficiency: 40% lower cost than titanium/cupronickel alternatives.

Product Applications

Marine Engineering: Ship condenser tubes, desalination pipelines, subsea valves.
Energy & Power: Thermal power plant condensers, nuclear cooling systems, refinery heat exchangers.
HVAC: Central AC evaporator tubes, chlorinated hot water pipes.
Industrial Components: Corrosion-resistant bearing bushings, deep-drawn sealing rings.

Processing Guidelines

Process	Key Parameters	Risk Control
Hot Working	750–830°C (finish >550°C)	Control O₂ at 0.5–1.5% (prevents Zn volatilization)
Welding	TIG: 80–120A	Argon purity ≥99.99% + preheat 150°C (prevents As porosity)
Annealing	Stress relief: 260–270°C×1h	N₂ atmosphere anti-oxidation
Cold Working	Deformation ≤80%	Intermediate annealing at 520–650°C
Surface Treatment	Pickling (HNO₃-H₂SO₄) + tinning	Essential for seawater exposure

Key Application Scenarios

Mega Vessels: 200k DWT ship condenser tube bundles (seamless, wall 1.5mm).
Nuclear Plants: AP1000 coolant pipes (chloride resistance design).
Coastal Power Stations: Seawater cooling valves (forged + Ni-Cr coated).
Premium HVAC: Central AC evaporator tubes (brazing integrity required).

FAQs

Q1: Is it suitable for potable water systems?

A: Restricted! Arsenic leaching risk. Use only in industrial cooling water systems.

Q2: How to resolve welding porosity?

A: Caused by As/Zn volatilization. Use ≥99.99% argon, preheat 150–200°C, post-weld stress relieve at 260°C×1h.

Q3: How to prevent hot cracking?

A: Control slightly oxidizing atmosphere (O₂: 0.5–1.5%), limit heating time ≤2h.

Q4: How to select vs. C44300 tin brass?

A: C68700 offers superior seawater resistance & 15% cost reduction; C44300 is arsenic-free for civilian applications.

Standard References

Standard System	Code	Scope
US Standard	ASTM B111M	Seamless Condenser & Heat Exchanger Tubes
Chinese	YS/T 649-2018	Extruded Copper/Copper-Alloy Bars
European	DIN 17672-1	Tolerances for Forged Cu Alloys
International	SAE J463	Mechanical Properties of Wrought Cu Alloys
General	ASTM B858	Dezincification Test Method

Technical Note

1. Data based on ASTM standard specimens. Actual properties subject to mill test certificates (MTC).

2. Critical applications require validation testing (e.g., ISO 9227 salt spray, ASME B96 brazing qualification).
Document Version: V2.1
Revision Date: 30 May 2025
Disclaimer: This document does not replace material test reports. FMEA analysis required for high-risk projects.

"The aluminum-arsenic synergy in C68700 establishes it as the premier choice for marine heat exchange systems."

— Copper Alloys in Marine Engineering White Paper, 2024 Edition

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