Introduction
Manufacturers working with high-pressure molding or heat-sensitive parts face a difficult trade-off. Materials with good thermal conductivity often lack strength. Stronger metals like steel fail to dissipate heat quickly enough. The result? Long cycle times, part defects, and frustrated production teams.
Ampco 940 solves this problem. This premium copper-nickel-silicon-chromium alloy combines exceptional thermal conductivity with impressive strength and hardness. It is engineered for demanding mold applications where both heat management and durability matter.
This guide explores how Ampco 940 performs in challenging scenarios. You will learn about its unique properties, where it excels, and how to work with this material effectively.
What Is Ampco 940?
Ampco 940 is a precipitation-hardened copper alloy. It is formulated with nickel, silicon, and chromium to enhance strength and hardness while retaining excellent thermal and electrical conductivity. Unlike traditional beryllium copper, it achieves these properties without beryllium, making it more environmentally friendly.
Standard specifications: Ampco 940 complies with RWMA Class 3 standards for resistance welding materials. Its chemical composition is approximately:
- Copper: 96%
- Nickel: 2.5%
- Silicon: 0.7%
- Chromium: 0.4%
Supplier brands: Ampco Metal Inc. (USA) is the primary manufacturer. They supply Ampco 940 in rods, plates, and custom shapes for mold components like cooling pins and injection nozzles.
Industry usage: Ampco 940 is used in 10 to 15 percent of high-pressure molds, particularly in plastic injection molding, cold-chamber die casting, and resistance welding. Its ability to handle pressures above 20,000 psi while dissipating heat quickly makes it a top choice for automotive and electronics manufacturing.
What Properties Make Ampco 940 Unique?
| Property | Ampco 940 | Comparison |
|---|---|---|
| Thermal Conductivity | 208 W/m·K | Steel: 40–50 W/m·K; Pure copper: 401 W/m·K |
| Electrical Conductivity | 48% IACS | Ideal for in-mold heating or sensors |
| Tensile Strength | Up to 689 MPa | Comparable to low-carbon steel |
| Hardness | 380 HBV | Standard copper: 100–200 HBV; 6061-T6 aluminum: 95–105 HBV |
| Thermal Expansion | 17.5 μm/m·°C | Between steel and aluminum; compatible with multi-material designs |
High Thermal Conductivity
At 208 W/m·K, Ampco 940 conducts heat significantly better than steel. This rapid heat dissipation reduces cooling times by 25 to 30 percent compared to steel molds. For thin-walled parts, this means shorter cycle times and higher output.
High Tensile Strength
Ampco 940 achieves tensile strength up to 689 MPa, surpassing most copper alloys and even some low-carbon steels. This strength allows it to withstand injection pressures up to 25,000 psi without deformation. In high-volume production, this extends mold life significantly.
High Hardness
At 380 HBV, Ampco 940 is much harder than standard copper alloys. This hardness minimizes wear from repeated contact with molten plastic or metal. Less wear means less maintenance and more consistent part quality.
Good Corrosion Resistance
Ampco 940 resists corrosion from water-based coolants, mild chemicals, and humidity. This outperforms uncoated steel in damp production environments. Corrosion-free surfaces transfer heat more efficiently and maintain consistent thermal performance over time.
No Beryllium
Unlike traditional beryllium copper, Ampco 940 contains no beryllium. This eliminates toxicity concerns, making it safer to work with and more environmentally friendly.
Where Is Ampco 940 Used in Mold Making?
Plastic Injection Molding Components
Ampco 940 is ideal for injection nozzles, cooling pins, and mold inserts. Its thermal conductivity accelerates cooling of heat-sensitive plastics like polycarbonate and nylon. Its hardness prevents wear from abrasive additives in engineering plastics.
Blow Molding
For large, thin-walled parts—automotive fuel tanks, industrial containers—Ampco 940’s strength resists deformation during high-pressure air inflation. Its thermal conductivity ensures uniform cooling and consistent part dimensions.
Resistance Welding Tips and Fixtures
The combination of electrical conductivity and hardness makes Ampco 940 perfect for resistance welding tools. It withstands repeated high-current, high-pressure cycles without degradation.
Cold-Chamber Aluminum Die Casting
In die casting, Ampco 940 components like shot sleeves and plungers resist wear from molten aluminum while dissipating heat quickly. This reduces cycle times and extends tool life.
Paper Winding Rolls
For industrial paper processing, Ampco 940 rolls maintain uniform pressure and heat distribution. This prevents paper tearing or uneven winding—thanks to the alloy’s strength and thermal stability.
How Do You Machine and Fabricate Ampco 940?
Machining Ampco 940 requires attention to its hardness, but the process is manageable with proper techniques.
| Process | Recommendations |
|---|---|
| Precision Machining | Use carbide tools; cutting speeds 100–150 SFM; light feeds; use coolant to prevent heat buildup; achieve tolerances ±0.0002 inches |
| CNC Milling | Rigid setups to avoid tool deflection; adaptive milling strategies for intricate features |
| EDM | Lower current settings to prevent excessive electrode wear; process faster than with steel |
| Grinding | Silicon carbide wheels; 400-grit wheel achieves Ra 0.05 μm finish; light pressure prevents wheel clogging |
| Surface Finishing | Polishes to Ra 0.02–0.05 μm with 600-grit sandpaper and buffing wheel; no additional plating needed for most applications |
Key advantage: Ampco 940 requires no post-machining heat treatment. It comes ready to use at full hardness. This reduces production time and eliminates the risk of distortion.
How Do You Maintain and Repair Ampco 940 Molds?
Welding Repair
Ampco 940 can be welded using Ampco-Trode 940 filler wire or Ampco-Trode 940 laser wire. These match the alloy’s composition and restore worn or damaged areas without compromising strength or thermal conductivity.
When joining Ampco 940 to stainless steel components, use Ampco-Trode 10 filler. This ensures a strong bond and prevents galvanic corrosion between the dissimilar metals.
Mold Cleaning
Clean surfaces with mild detergents and soft brushes. Avoid abrasive cleaners, which can scratch the surface and reduce thermal conductivity.
Preventive Maintenance
Inspect Ampco 940 components monthly, especially in high-pressure areas like injection nozzles. Polishing worn surfaces restores thermal performance and prevents part defects.
Inspection
Use ultrasonic testing to detect internal cracks or voids. These can compromise both strength and heat transfer. Visual checks for corrosion or tarnish ensure cooling channels remain unobstructed.
How Does Ampco 940 Compare to Other Copper Alloys?
| Material | Thermal Conductivity (W/m·K) | Tensile Strength (MPa) | Hardness (HBV) | Safety |
|---|---|---|---|---|
| Ampco 940 | 208 | Up to 689 | 380 | No beryllium |
| Beryllium copper (C17200) | 200–250 | 690 | 200–300 | Contains toxic beryllium |
| Chromium copper | 300–350 | 400–500 | 200–250 | Moderate strength |
| Copper-tungsten | 200–250 | 500–600 | 200–250 | Lower hardness |
Ampco 940 offers similar strength to beryllium copper with comparable thermal conductivity—but without the toxicity. It is harder than chromium copper and more wear-resistant than standard copper-tungsten alloys.
Yigu Technology’s Perspective
As a custom manufacturing supplier, we recommend Ampco 940 for clients needing high-strength, thermally efficient mold components. We have found it particularly effective in automotive injection molds.
Performance gains: Its 208 W/m·K thermal conductivity reduces cycle times by 25 percent for thin-walled parts. Its 689 MPa tensile strength withstands pressures above 20,000 psi, outperforming standard copper alloys in durability.
Cost-effectiveness: While Ampco 940 costs more upfront, its longer life and improved part quality make it cost-effective for high-volume runs. Our team uses carbide tools and EDM to achieve tight tolerances, ensuring seamless integration with steel or aluminum molds.
For demanding applications, Ampco 940 delivers unmatched performance.
Conclusion
Ampco 940 solves the classic trade-off between thermal conductivity and strength. Its high thermal conductivity—208 W/m·K—reduces cooling times and cycle times. Its tensile strength—689 MPa—withstands high pressures without deformation. Its hardness—380 HBV—resists wear in demanding applications.
From plastic injection molding to die casting and resistance welding, Ampco 940 performs where other materials fall short. It machines well with proper techniques, requires no post-heat treatment, and maintains its properties over extended production runs. For manufacturers facing demanding thermal management challenges, Ampco 940 offers a reliable, high-performance solution.
FAQ
How does Ampco 940 compare to beryllium copper in terms of safety?
Ampco 940 is safer than traditional beryllium copper because it contains no beryllium—a toxic material requiring special handling. This makes it easier to work with and more environmentally friendly, while still offering comparable strength and conductivity.
Can Ampco 940 be used in food-grade or medical mold applications?
Yes. Ampco 940’s copper-based composition, with no toxic additives, meets FDA standards for indirect food contact. Its corrosion resistance also makes it suitable for medical device molds requiring frequent cleaning with mild disinfectants.
What is the maximum number of cycles an Ampco 940 mold component can handle?
Ampco 940 components last 100,000 to 200,000 cycles for non-abrasive plastics, far exceeding standard copper alloys (50,000–100,000 cycles). For abrasive materials like glass-filled plastics, expect 50,000 to 80,000 cycles with proper maintenance.
Contact Yigu Technology for Custom Manufacturing
Looking for mold components that combine high strength with exceptional thermal conductivity? Yigu Technology specializes in custom non-standard plastic and metal products. Our team has experience working with Ampco 940 and other high-performance materials.
Reach out today to discuss your next project. Let us help you optimize your molds for demanding applications.
