Mechanical Construction Materials in the Plastic Industry: Application of Copper-Beryllium

By Sérgio Mello 10 minutes ago 5 min read

In the plastic industry, the choice of materials for mechanical components and molds is essential to ensure performance and productivity of operations. Traditionally, we use steels such as AISI P20, AISI H13, 1.2343, and AISI 420, known for their wear resistance and high capacity to withstand severe hot working conditions. Additionally, aluminum 7050 stands out especially in processes such as blow molding and thermoforming, offering excellent lightness and good machinability.

However, a material that has been gaining prominence in terms of thermal efficiency and reduction of production cycles is the copper-beryllium alloy. This alloy, which combines copper and beryllium, has superior thermal conductivity, making it ideal for optimizing heat transfer processes and improving mold productivity.

Why do we continue using the same materials?

It's true that conventional steels solve many issues in the industry. P20 is that wildcard that every mold maker knows, H13 withstands high temperatures, and so on. But we need to recognize that in terms of thermal efficiency, these materials leave something to be desired.

If we analyze technically, AISI P20 (1.2311) has a thermal conductivity of approximately 29 W/m·K, while H13 is around 25 W/m·K. In practical terms? Slow heat dissipation, longer cycles, greater energy consumption. In many cases, we end up accepting longer cycles out of pure inertia, right? "We've always done it this way" is that excuse we hear in the corridors. But can we do it differently? The answer will always be yes!

Copper-Beryllium Alloy: The differential you may not have known you needed

Let's be serious: time is money. And that's where the copper-beryllium alloy comes in. This material is a game-changer when we talk about heat transfer in molds.

The copper-beryllium alloys most used in the industry (C17200 and C17510) have thermal conductivity in the range of 105-130 W/m·K. This is absurdly superior to steels! We're talking about a difference that can reach 5x in heat transfer capacity.

The copper-beryllium alloy is extremely useful in mold components that require high heat dissipation, such as:

• Inserts and cavities: They provide more efficient cooling, resulting in cycle time reduction of up to 20-40% in some cases I've monitored. Think about a 200ml cup cavity - change the inserts to Cu-Be in critical areas and the cycle drops from 12 to 8 seconds. That's a big difference!

• Ejector pins: Traditional steel pins can be real "hot spots" in the mold. Copper-beryllium pins dissipate heat much faster, minimizing the risk of plastic adhesion and increasing the lifespan of your equipment. This is a hack that few mold makers know, but it completely changes the game in technical parts.

• Injection nozzles and hot runners: My friend, who has never suffered with clogging or degradation in hot runner systems? The improvement in heat transfer optimizes material flow, ensuring parts with higher quality and fewer defects. In sensitive materials like PC or POM, the difference is striking!

  
  

Numbers don't lie

With thermal conductivity up to 10 times greater than traditional steels, the use of copper-beryllium is not just an engineer's whim. We're talking about practical results:

• Average reduction of 25-30% in production cycles

• Significant improvement in thermal stability of the process

• Reduction of internal tensions in the parts, resulting in better dimensional precision

• Lower energy consumption per part produced

• Reduction of up to 75% in the thermal stabilization time of the mold at the beginning of production

  
  

One of my clients replaced steel inserts with copper-beryllium in critical areas of a plastic cap mold and reduced the cycle from 12 to 8.5 seconds. Seems like a small change? Do the math: that's almost 30% more productivity without investing in new machines! By the end of the month, they were producing over 200,000 more parts on the same equipment.

The B side: costs and maintenance

Of course, it's not all wonderful. Copper-beryllium costs more than conventional steels, that's a fact. Depending on the supplier and the specific alloy, it can cost 3 to 8 times more per kilogram than P20 steel. In addition, it requires some care in machining and maintenance.

In machining, tools wear out faster due to the abrasiveness of the material. Cutting parameters need to be adjusted - higher speeds and smaller feeds generally work better. It's almost like machining high-strength brass.

Another thing that few people talk about: because it contains beryllium, it requires safety precautions during machining to avoid particle inhalation. Beryllium dust is toxic, so adequate exhaust systems are essential. But let's be practical: the return on investment generally compensates, especially in high-volume productions where each second saved in the cycle represents significant gains at the end of the month.

Practical application: where does it make the most sense?

Not every mold needs to be made 100% of copper-beryllium. The smartest approach is to identify the "hot spots" and use the alloy strategically:

• In areas of difficult cooling

• Near injection gates

• In regions where frequent warping occurs

• In thin-walled parts that need to solidify quickly

• In fine details that require quick and uniform filling

The intelligent combination of materials (steel + copper-beryllium) generally offers the best cost-benefit. It's like that story of "using the right tool for the right job."

Surface treatments and maintenance

Speaking of practical application, it's crucial to understand how to work with Cu-Be on a daily basis:

• Surface treatments: Plasma nitriding has shown excellent results for increasing surface hardness without compromising thermal conductivity. Hard chrome plating should be avoided, as it can create an unwanted thermal barrier.

• Polishing: Cu-Be accepts high-gloss polishing (mirrored), but requires specific techniques. The use of diamond pastes in decreasing granulometry, followed by polishing with chromium oxide, generally gives the best results.

• Weldability: In case of repair needs, Cu-Be can be welded with TIG techniques specific for copper alloys. It is important to use compatible filler material and perform adequate preheating.

• Cooling: As the material transfers heat faster, cooling circuits can be optimized. In some cases, it is possible to reduce the diameter of the channels or increase their spacing, facilitating mold design.

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Mechanical properties: what nobody tells you

Speaking of important numbers, copper-beryllium is not only good at heat transfer. The alloys for molds generally feature:

• Tensile strength: 1000-1400 MPa (comparable to many steels!)

• Hardness: 35-42 HRC after adequate heat treatment

• Fatigue resistance: Excellent, supporting millions of cycles

• Corrosion resistance: Superior to conventional steels

This means that, in addition to the thermal advantage, you don't lose mechanical strength.

Final considerations

In an increasingly competitive market, choosing the right material is fundamental to ensure high performance in production processes. If you have already used copper-beryllium in your processes, share your experience in the comments! Let's discuss how material innovation can directly impact efficiency in the plastic industry.

References:

1. Harada, J. "Molds for Thermoplastic Injection: Materials and Design". Artliber, 2nd Ed, 2020.

2. Copper Development Association. "Copper-Beryllium Alloys in Plastic Mold Applications". Technical Brief, 2021.

3. Menges, G.; Michaeli, W.; Mohren, P. "How to Make Injection Molds". Hanser, 4th Ed, 2019.

4. Brazilian Plastic Industry Association (ABIPLAST). "Good Practices Manual in Mold Manufacturing", 2020.