Lijevanje magnezija pod pritiskom: Rješenja za lagani metal

1. Uvod

Magnesium die casting represents a unique convergence of lightweight performance and high-volume manufacturability.

As the lightest structural metal, magnesium offers significant benefits in sectors where smanjenje težine, strength-to-weight ratio, i toplinske performanse su kritični.

What Is Die Casting?

Kasting is a metal-forming process where molten metal is injected at high speed and pressure into a steel mold, producing near-net-shape parts with high dimensional accuracy.

Magnezij, due to its low melting point (~650°C), Izvrsna odljevanost, and high fluidity, is ideally suited for this process.

Why Magnesium?

• Gustoća: ~1.78 g/cm³ (≈33% lighter than aluminum, 75% lighter than steel)
• Omjer visoke snage i težine
• Excellent vibration damping and electromagnetic shielding

2. Magnesium Alloys for Die Casting

Magnesium die casting alloys are specifically engineered to deliver a combination of lightweight performance, odljenost, mehanička čvrstoća, i otpornost na koroziju.

The most commonly used magnesium alloys in die casting belong to the AM, AZ, and AE series, with other specialty alloys developed for high-temperature or niche industrial applications.

Classification of Magnesium Die Casting Alloys

Magnesium alloys are categorized based on their principal alloying elements. The naming convention typically reflects the kemijski sastav, gdje:

• A = Aluminum
• Z = Zinc
• M = Manganese
• E = Rare Earths (Npr., cerijum, yttrium, neodymium)
• S = Silicon
• K = Zirconium

Na primjer, AZ91D consists primarily of aluminij (9%) i cinkov (1%), with trace additions of manganese and other elements for grain refinement and stability.

Common Magnesium Alloy Series for Die Casting

3. Magnesium Die Casting Processes

Magnesium die casting is a precision manufacturing technique in which molten magnesium alloy is injected into a steel mold under high pressure to produce net-shape or near-net-shape components.

Hot-Chamber vs. Cold-Chamber Die Casting

Magnesium alloy die casting employs two primary machine types: hot-chamber i cold-chamber sustava.

Each is tailored to different alloy characteristics, component sizes, and production requirements.

Hot-Chamber Die Casting

Hot-chamber machines, often referred to as gooseneck systems, are the most common choice for magnesium due to the metal’s relatively low melting point and non-reactivity with steel.

This method is particularly efficient for small to medium-sized components, typically weighing manje nego 2 kg.

In this configuration, the melting pot is integrated into the injection unit.

The molten magnesium alloy resides in this pot, and a plunger mechanism injects it through a gooseneck-shaped channel directly into the die cavity.

The short path between the molten pool and the mold minimizes thermal losses and maintains consistent injection temperatures, obično okolo 640–680 °C—ideal for magnesium’s fluidity.

Cycle times range between 10–30 seconds, making hot-chamber casting well-suited for high-volume production of thin-walled or geometrically complex parts such as:

• Mobile device housings
• Camera frames
• Small electronics enclosures

Međutim, the integrated melting-injection system also has limitations.

Alloys with higher melting points or those more prone to oxidation and contamination (such as aluminum or rare-earth-rich compositions) jesu not compatible s ovim procesom.

Continuous exposure of molten metal to air increases the risk of oxidation, reducing alloy cleanliness over time.

Cold-Chamber Die Casting

Za razliku od, cold-chamber machines are engineered for larger and more complex parts, often weighing up to 25 kg ili više.

This method separates the melting furnace from the injection system, ponuda greater control over alloy quality and temperature stability.

In operation, molten magnesium is ladled manually or robotically from an external crucible into the shot sleeve.

A hydraulic plunger then forces the metal into the die at high injection pressures—typically between 50 i 150 MPA.

This separation allows for better handling of alloys sensitive to thermal cycling and air exposure.

Cold-chamber die casting is commonly used in producing:

• Automobilski chassis components
• Structural brackets
• Prijenosna kućišta
• Large e-mobility castings

Although cycle times are longer due to the extra ladling step and extended solidification periods,

the process is better suited for applications that demand veća snaga, dimenzijska preciznost, i thicker wall sections.

4. Mold Design and Tooling in Magnesium Die Casting

Izvedba, pouzdanost, and cost-efficiency of magnesium die casting depend heavily on mold (umrijeti) design and tooling strategy.

A well-designed die not only ensures dimensional accuracy and repeatability but also maximizes tool life and minimizes casting defects such as porosity, warpage, or incomplete filling.

Die Materials and Surface Coatings

Given the high injection pressures (do 150 MPA) and rapid thermal cycling (from ~650 °C molten magnesium to die temperatures of ~200–250 °C), the die material must possess:

• High thermal fatigue resistance
• Excellent wear resistance
• Good toughness and polishability

Common Die Materials:

• H13 tool steel: Industry standard for magnesium alloy die casting dies; air-hardening steel with high chromium and molybdenum content.
• Premium H11 or H21: Selected when additional hot strength or toughness is needed in complex geometries.

Površinski tretmani:

To extend die life and reduce soldering (metal adhesion), surface treatments are applied:

• PVD/CVD Coatings (Npr., Kositar, CrN): Provide low-friction, high-hardness surfaces.
• Nitriranje: Enhances surface hardness and wear resistance.
• Boronizing: Used in critical areas prone to erosion.

Critical Design Elements

• Sustavi hlađenja: Multi-channel circuits reduce cycle time by up to 25%.
• Gating and Venting: Thin-walled vents (0.05–0.1 mm) minimize gas porosity.
• Die Life Expectancy: 500,000–2 million cycles, depending on alloy and maintenance.

5. Magnesium Alloy Properties

Magnesium alloys offer a unique combination of lightweight, good mechanical strength, odljenost, i toplinske performanse, making them ideal for structural and electronic applications.

Key Properties of Common Magnesium Die Casting Alloys

6. Corrosion Behavior and Surface Protection

While magnesium is prized for its lightweight and strength-to-weight ratio, its corrosion behavior presents a significant engineering challenge, especially in humid, saline, ili kemijski agresivne okoline.

Intrinsic Corrosion Tendencies of Magnesium

Magnesium has a highly reactive surface and sits low on the galvanic series, making it thermodynamically vulnerable to oxidation and electrochemical attack.

Unlike aluminum, magnesium’s natural oxide layer (MgO) is porous and non-adherent, offering limited protection.

Key corrosion risks:

• Galvanic corrosion when in contact with more noble metals (Npr., čelik, bakar)
• Pitting corrosion in chloride-containing environments (Npr., road salt, morska voda)
• Filiform and crevice corrosion under coatings or at tight joints
• Hydrogen evolution, which can exacerbate micro-cracking and porosity

Corrosion Performance by Alloy

Different magnesium alloys offer varying levels of corrosion resistance:

• AZ91D: Moderate resistance; suitable for indoor or mildly corrosive environments.
• AM60B: Slightly better due to its lower aluminum content.
• AE44 / QE22: Enhanced corrosion resistance due to rare earth elements, even at elevated temperatures.

Surface Protection Strategies

Due to the limitations of magnesium’s native oxide film, post-casting surface treatments are almost always required, especially in automotive, zrakoplovstvo, or marine applications.

Chromate Conversion Coatings (CCC)

• Traditional method, often yellow or iridescent in color
• Provides moderate corrosion protection
• Hexavalent chromates are being phased out due to environmental regulations

Anodirajući (Magoxid, Dow 17, HAE)

• Produces a thicker oxide layer for enhanced corrosion resistance
• Less effective than aluminum anodizing; often used as a base for paint

Micro-Arc Oxidation (MAO) / Plasma Electrolytic Oxidation (PEO)

• Advanced ceramic-like surface layer
• Excellent thermal stability, wear and corrosion resistance
• Suitable for high-end applications (Npr., zrakoplovstvo, vojnog, EV batteries)

Organic Coatings & Paint Systems

• Epoxy or polyester coatings applied via powder coating or electrocoating (e-coat)
• Must be used with appropriate pretreatment (Npr., phosphate or zirconium conversion)
• Effective in providing multi-year protection in automotive service

Bezelektrično niklanje

• Provides both corrosion and wear resistance
• Suitable for precision components requiring dimensional stability

8. Applications of Magnesium Die Casting

Automobilska industrija

Magnesium is extensively used in the automotive industry to reduce vehicle weight and improve fuel efficiency and performance.

As automotive manufacturers pursue more stringent CO₂ emissions targets and electric mobility gains traction, magnesium’s relevance is rapidly expanding.

Common Automotive Components:

• Steering wheel cores
• Dashboard cross beams
• Prijenosna kućišta
• Seat frames and recliner mechanisms
• Instrument panel supports
• Transfer cases and gearbox covers
• Clutch housings
• Kućišta za baterije (for EVs)

Zrakoplovstvo i obrana

In aerospace applications, the demand for lightweight materials with high strength and vibration-damping makes magnesium alloys particularly valuable.

Their superior strength-to-weight ratio and good machinability are beneficial in both military and commercial aviation.

Zrakoplovne komponente:

• Rotorcraft transmission housings
• Airframe fittings and access panels
• Avionics housings
• Interior brackets and supports
• Cargo bay and cockpit enclosure components

Electronics and Telecommunications

Magnesium die castings are widely adopted in the electronics industry, where electromagnetic compatibility (EMC) and thermal management are critical.

Magnesium provides both mechanical support and shielding against electromagnetic interference (EMI).

Common Electronic Parts:

• Laptop and tablet enclosures
• Smartphone frames
• Camera bodies
• TV and monitor frames
• Hard disk drive (HDD) kućišta
• Projector housings
• Server and telecom equipment covers

Industrial and Power Tools

For handheld or portable tools, magnesium’s low weight and high fatigue strength offer significant ergonomic advantages.

The material also enhances shock absorption and thermal conductivity in heavy-duty environments.

Tooling Applications:

• Power drill housings
• Circular saw casings
• Impact wrench bodies
• Battery tool enclosures
• Heat sinks and motor frames

Emerging Markets and Future Trends

Kako se tehnologija razvija, magnesium is finding new roles in disruptive applications—particularly those involving lightweight robotics, autonomous systems, and electric mobility.

Emerging Applications:

• Drones and UAV airframes
• E-bike frames and battery modules
• Autonomous vehicle sensor housings
• Medical device components (Npr., protetika, zagrada)
• Sustainable transportation (e-scooters, micro-mobility platforms)

9. Advantages and Disadvantages of Magnesium Die Casting

Magnesium die casting is increasingly favored in modern manufacturing for its exceptional weight-to-performance characteristics.

Advantages of Magnesium Die Casting

Lightest Structural Metal

Magnesium has a density of 1.74 g/cm³, približno 35% lighter than aluminum i 75% lighter than steel,

making it ideal for applications where weight reduction is critical (Npr., zrakoplovstvo, EVS, handheld tools).

Izvrsna odljevanost

Magnesium alloys exhibit superior flow characteristics, enabling the casting of tankog zida, kompleks, i highly detailed geometries with minimal porosity or shrinkage defects.

Visok omjer čvrstoće i težine

Many magnesium alloys (Npr., AZ91D, AE44) provide impressive mechanical performance relative to their mass, offering tensile strengths in the 200–280 MPa domet.

Vrhunska obradivost

Magnesium machines faster and with less tool wear than aluminum, reducing production time and tool maintenance. Its chips break easily and carry heat away from the cutting zone.

Electromagnetic Shielding

Magnesium offers effective EMI/RFI shielding, making it highly suitable for enclosures in electronics, telecom, and automotive control units.

Prigušivanje

The material has excellent vibration-damping properties, helping to reduce noise, šok, i umor in automotive and power tool components.

Reciklalnost

Magnesium alloys are 100% recyclable with minimal degradation of properties, supporting circular manufacturing and sustainability initiatives.

Disadvantages of Magnesium Die Casting

Corrosion Susceptibility

Magnesium is highly reactive and prone to galvanic and pitting corrosion, especially in chloride-rich or humid environments. Surface protection (Npr., premazivanje, Anodirajući) is typically mandatory.

Limited High-Temperature Strength

Most commercial magnesium alloys soften at elevated temperatures, limiting their use above 120–175 °C. Specialized alloys like AE44 and QE22 offer modest improvements.

High Cost

The raw material cost of magnesium is generally 30% higher than that of aluminum.

Dodatno, the processing of magnesium alloys requires specialized equipment and handling due to the metal’s reactivity, increasing overall production costs.

Oxidation and Flammability

Molten magnesium can ignite if not handled properly. This necessitates strict foundry protocols, protective atmospheres (Npr., SF₆ substitutes), and safety equipment.

Lower Ductility than Aluminum

Although magnesium alloys like AM60B offer decent elongation, most alloys are more brittle than their aluminum counterparts, which may limit deformation in crash zones or forming applications.

Welding Limitations

Magnesium is difficult to weld, especially using conventional methods. Friction stir welding and laser welding offer alternatives but add complexity and cost.

10. Why is Magnesium Die Casting Costlier?

The higher cost of magnesium alloy die casting can be attributed to several factors.

Prvo, the raw material cost of magnesium is higher than that of more commonly used die-casting metals like aluminum.

Magnesium production requires more energy-intensive processes, contributing to its relatively expensive price.

Secondly, magnesium alloys are more reactive and require specialized handling and equipment during the melting, lijevanje, and processing stages.

This includes the use of protective atmospheres during melting to prevent oxidation, which adds to the operational costs.

Dodatno, the need for surface treatments to enhance corrosion resistance further increases the overall cost of magnesium die-cast parts compared to some other metals that may require less extensive treatment.

11. Comparison with Other Die-Casting Materials

Magnesium die casting is often compared with other common materials, takav aluminij i cinkov, due to their widespread use in precision components.

Each material offers a unique balance of properties, koštati, and processability.

Key Comparative Parameters

12. Zaključak

Magnesium die casting has evolved into a critical manufacturing technology for industries prioritizing lightweight strength, točnost dimenzije, and high production throughput.

While it comes with material, alatna oprema, and surface protection challenges, njegov performance advantages—particularly in transportation and electronics—continue to justify its use.

As the global shift toward electrification, održivost, and lightweight engineering accelerates, magnesium die casting will only become more vital in modern design and manufacturing strategies.

Usluge tlačnog lijevanja po narudžbi tvrtke DIE

OVAJ nudi visoku kvalitetu običaj usluge tlačnog lijevanja skrojeni kako bi zadovoljili vaše točne specifikacije.

Uz dugogodišnje iskustvo i naprednu opremu, specijalizirani smo za proizvodnju preciznih metalnih komponenti pomoću aluminij, cinkov, i magnezij legure.

Što nudimo:

• OEM & ODM rješenja za lijevanje pod pritiskom
• Podrška za male do velike proizvodnje
• Prilagođeni dizajn kalupa i inženjerska podrška
• Niske tolerancije dimenzija i izvrsna završna obrada površine
• Secondary operations, uključujući CNC obrada, površinska obrada, i skupština

Česta pitanja

Is magnesium easy to cast?

Magnesium is relatively easy to cast due to its excellent fluidity and low melting point (~650°C).

Međutim, its high chemical reactivity requires controlled atmospheres and specialized equipment to prevent oxidation and ensure high-quality castings.

How are magnesium dies made?

Magnesium dies are typically made from high-strength tool steels such as H13, which are heat-treated for hardness and durability.

They often include precise cooling channels and surface coatings (like PVD or CVD) to resist thermal fatigue and wear during repeated casting cycles.

What metal is best for die casting?

The best metal depends on the application: magnesium offers the lightest weight and good strength; aluminum balances strength, otpor korozije, i trošak; zinc excels in detail resolution and low melting temperature.

Selection is based on performance, koštati, and design requirements.

Why use magnesium instead of aluminum?

Magnesium is preferred over aluminum when weight reduction is critical because it is about 35% lighter.

It also offers superior machinability and good dimensional stability, making it ideal for automotive and aerospace parts where minimizing mass improves fuel efficiency and performance.