H70 BRASS

Product introduction

📌 Designation and Standard

Common Name: H70 Brass
Also Known As: Cartridge Brass or 70/30 Brass (historically used for ammunition casings) .
Chinese Standard (GB): H70 (GB/T 5231-2012, GB/T 2059-2000) .
International Equivalents: C26000 (UNS), C2600 (JIS), ASTM B36/B36M .
Material Type: Wrought Copper-Zinc Alloy / Single-Phase Alpha (α) Brass .

⚗️ Chemical Composition (by mass)

H70 is a high-copper binary brass with a strictly controlled composition to ensure its characteristic ductility .

Element	Content (%)	Notes
Copper (Cu)	68.5% – 71.5%	The nominal "70" refers to this high copper content.
Zinc (Zn)	Remainder	Approximately 29-31%.
Lead (Pb)	≤ 0.03%	Kept low to preserve hot workability.
Iron (Fe)	≤ 0.10%	Impurity limit.
Total Impurities	≤ 0.3%	Includes elements like Ni, Sb, Bi.

🔬 Microstructure & Physical Properties

Microstructure: Due to its high copper content (over 68%), H70 has a single-phase alpha (α) solid solution structure at room temperature . This face-centered cubic structure is inherently soft and ductile, giving H70 the best plasticity among all common brasses .
Physical Properties :

Density: 8.53 g/cm³
Melting Point: 966 – 1001 °C
Thermal Conductivity: ~140 W/(m·K) (Excellent for heat dissipation)
Electrical Conductivity: ~28-32% IACS (Sufficient for general applications)
Elastic Modulus: ~105 GPa

📊 Mechanical Properties (Strongly Temper-Dependent)

Like H65, the mechanical properties of H70 vary dramatically with its temper (degree of cold work). It is available in various conditions from soft annealed to spring hard. The values below represent typical ranges:

Temper (Condition)	Tensile Strength (MPa)	Yield Strength (MPa)	Elongation (%)	Hardness (HV)	Typical Application Notes
M (Annealed/Soft)	≥290 - 315	~90	≥40 - 50	55 - 70	For extremely deep drawing and complex forming.
Y4 (1/4 Hard)	340 - 410	~250 - 300	~30 - 40	85 - 110	For moderate forming with some added stiffness.
Y2 (1/2 Hard)	370 - 460	~300 - 380	~20 - 30	100 - 130	General-purpose parts, connectors.
Y (Hard)	≥390 - 540	~400 - 450	≥3 - 12	130 - 160	High-strength stamped parts, springs, cartridge cases.
T (Extra Hard)	520 - 620	~500 - 580	≥4	150 - 190	For very high strength requirements.

Note: The table compiles data from multiple technical sources. The exact values depend on the specific product form (sheet, strip, wire) and testing standards. H70's key advantage is its ability to achieve a wide range of strengths while maintaining excellent formability in softer tempers .

✨ Key Characteristics

Best Formability: H70 possesses the highest plasticity and cold workability of all common brass grades, making it the top choice for the most challenging deep-drawing and bending operations .
Excellent Strength-Ductility Balance: It offers a unique combination of high strength (when work-hardened) and exceptional ductility (when annealed), unmatched by lower-copper brasses .
Good Joinability: It has excellent solderability (soft soldering and brazing) and good weldability (with argon protection) .
Corrosion Resistance: Provides good resistance to atmospheric corrosion, fresh water, and some chemicals . However, it is susceptible to stress corrosion cracking (season cracking) if internal stresses from cold working are not relieved by annealing .

🛠️ Typical Applications

H70 is the material of choice for parts requiring severe cold forming .

Ammunition: Cartridge cases (its historical and most famous application) .
Automotive: Radiator cores and tanks, heat exchanger components, cooling system parts .
Industrial: Deep-drawn parts,波纹管 (bellows), flexible hoses, pump components, gaskets .
Hardware & Electronics: Connectors, terminals, fasteners, springs, eyelets, rivets, zippers .

⚙️ Comparison: H70 vs. H65 Brass

You asked about H65 earlier. Here is a quick comparison to highlight the differences:

Feature	H70 Brass	H65 Brass
Cu Content	68.5-71.5% (Higher)	63.0-68.5% (Lower)
Microstructure	Single-phase α	Single-phase α (at higher Cu end)
Key Strength	Best plasticity & formability	Excellent formability, slightly higher strength potential in hard tempers
Typical Use	Most severe deep drawing (e.g., cases)	Deep drawing + general parts (e.g., terminals)

In short, H70 is the specialist for ultimate formability, while H65 offers a slightly more balanced and cost-effective option for a wider range of applications.

If you have a specific application in mind (e.g., deep drawing a complex shape), I can help you decide between H70 and H65.

Are you also interested in further steel processing (machining)?

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