C70350 is a high-strength silicon copper alloy, also known as silicon white copper. It belongs to a type of Cu Fe P lead frame material, and according to the American ASTM Processing Copper and Copper Alloy Chemical Composition Table (99 Edition), C70350 contains Fe element. BSi2-0.5 is another representation of C70350, which refers to a special type of silicon bronze containing approximately 0.5% silicon. This material is widely used in various manufacturing fields due to its high strength and excellent performance
C70350 copper nickel silicon alloy, not belonging to copper nickel alloy, belongs to the category of white copper, with excellent cold workability, good hot forming, and excellent cold and hot brazing and gas shielded arc welding; Used for manufacturing high-strength parts that require good formability, high endurance relaxation ability, and moderate conductivity
Standards & Specifications
- ASTM: B422, B534 (strip/plate forms)
- SAE: J461, J463
- Military: MIL-C-24138 (if applicable)
- ISO: CuNi3Si (similar but not identical)
Chemical Composition
| Element | Content Range | Purpose |
|---|---|---|
| Copper (Cu) | 94.0 - 96.0% | Base metal |
| Nickel (Ni) | 2.5 - 3.5% | Strength, precipitation hardening |
| Silicon (Si) | 0.5 - 0.8% | Forms strengthening precipitates with Ni |
| Magnesium (Mg) | 0.05 - 0.30% | Grain refinement, enhances stress relaxation |
| Iron (Fe) | ≤ 0.10% | Impurity control |
| Zinc (Zn) | ≤ 0.10% | Impurity control |
| Other elements | ≤ 0.50% total |
Physical Properties
|
Alloys |
C70350 |
|
Gravity |
8.82 |
|
(Coefficent of thermail expansion) |
17.6 |
|
Thermal Conductivity |
0.2 |
|
Electrical Conductivity |
48 |
Mechanical Properties
By Temper Condition
| Temper | Tensile Strength (MPa) | Yield Strength (0.2% offset, MPa) | Elongation (%) | Hardness (Rockwell) |
|---|---|---|---|---|
| Annealed (O60) | 310 - 380 | 110 - 170 | 25 - 35 | B50 - B65 |
| 1/4 Hard (H01) | 380 - 450 | 310 - 380 | 12 - 20 | B75 - B85 |
| 1/2 Hard (H02) | 450 - 520 | 380 - 450 | 8 - 15 | B85 - B95 |
| Hard (H04) | 520 - 590 | 480 - 550 | 3 - 10 | B95 - 100B |
| Extra Hard (H08) | 590 - 660 | 550 - 620 | 1 - 5 | 100B - 25C |
| Age-Hardened | 690 - 830 | 620 - 760 | 2 - 8 | 28C - 35C |
Processing Characteristics
Heat Treatment
- Solution Annealing: 900-950°C (1650-1740°F), rapid quench
- Aging Treatment: 450-500°C (840-930°F) for 2-4 hours
- Typical Process: Form in soft condition → Age harden → Final form/set
Forming & Machining
- Machinability: 30% (relative to free-cutting brass = 100%)
- Cold Working: Excellent response to cold work
- Hot Working: Possible but less common
- Joining: Can be soldered, brazed, welded (resistance welding preferred)
Advantages
- High Strength-to-Conductivity Ratio: Unusual combination for copper alloys
- Excellent Stress Relaxation Resistance: <10% loss after 1000 hours at 150°C
- Good Fatigue Resistance: Particularly in spring applications
- Thermal Stability: Properties maintained up to ~300°C
- Formability: Good in annealed condition before final aging
- Corrosion Resistance: Superior to brass, comparable to other copper-nickels
Comparison with Similar Alloys
| Alloy | Composition | Strength | Conductivity (%IACS) | Primary Use |
|---|---|---|---|---|
| C70350 | Cu-Ni-Si-Mg | Very High | 30-50 | High-strength connectors |
| C70250 | Cu-Ni-Mg-Si | High | 35-55 | Spring contacts |
| C19025 | Cu-Ni-P-Sn | High | 40-50 | Lead frames |
| C19400 | Cu-Fe-P-Zn | Medium | 50-70 | Circuit board materials |
| C17200 | Cu-Be | Highest | 18-25 | Springs, diaphragms |
Need help on material comparison? Read our lead‑frame copper alloy selection guide to compare C19400, C70250, C18150 and other grades.
Test Equipments
Applications
C70350 strip is often used in applications requiring high strength + good electrical conductivity, such as:
- Electrical connectors (especially in automotive and high-reliability electronics)
- Spring contacts and terminals
- Lead frames in semiconductors
- Switches, relays, and circuit breakers
- Battery contacts
- Heat sinks where both strength and thermal conductivity are needed.
FAQ
Q1: What is C70350 material?
A: C70350 is a high‑performance copper‑nickel‑cobalt‑silicon (Cu‑Ni‑Co‑Si) alloy, typically supplied as strip or sheet. It belongs to the precipitation‑hardening family of copper alloys and was jointly developed by Wieland and Olin Brass (USA). This material is an alternative to C70250 in high‑strength annealed tempers.
Q2:What information should i confirm you when i send inquiry
A:Sometimes we need product specification like material standard or Grade, size, Qty, shipping port, Terms like FOB or CIF etc.
Q3: Which standards does C70350 comply with?
A: C70350 strip and sheet are generally produced in accordance with ASTM B422/B422M. Additionally, strip used for electrical connectors or spring contacts also meets ASTM B888/B888M. In the Japanese market, JIS H3130‑2006 is also referenced.
Q4: How long of the delivery time?
A: Usually, the shipment can be delivery within 15-30days after the order confirmed.
Q5: How about the payment items?
A: LC, T/T, PayPal, Western Union etc.
Q6: Which country have you exported to?
A: Our main market is South America, Middle East, Africa and Europe. And have built long time relationship with Pakistan, US, Norway, Germany, Korea, Russia,Taiwan customers.And got continue orders from them every month.
Q7: Can i visit your factory?
A: Sure! Welcome in any time.
Q8: How about the MOQ?
A: Normally MOQ is 200kg, We always expect more opportunities with you. But for some special material or special size let's communicate the actual status.
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