Aluminum Die Casting: The Complete B2B Guide

Below we walk through the process the way a shop-floor metallurgist walks through it: alloy families actually used in production (not the textbook-only ones), the cold-chamber vs hot-chamber split, the four parameter windows that quietly decide 80% of porosity and fill outcomes, and the defect-cost math you can hand to a sourcing manager. Where numbers matter, we cite AFS und NADCA industry data rather than guesswork.

What Aluminum Die Casting Actually Is (and What It Is Not)

In the strict NADCA sense, Aluminiumdruckguss refers to forcing molten aluminum into a hardened steel die under high pressure, holding it under intensifier pressure until the skin freezes, then ejecting a near-net-shape part. Two flavors dominate B2B:

• High-pressure die casting (HPDC). Cold-chamber machines typically 80–4,000 ton clamp force, injection speeds above 30 m/s on the gate, cycle times 30–180 s. This is what most buyers mean by “die cast.”
• Low-pressure / gravity die casting (LPDC / GDC). Metal fills the cavity under 0.3–1 bar gas pressure or pure gravity. Slower fill, denser skin, lower tooling cost. Common for wheels and large structural housings where HPDC would generate unacceptable porosity.

What it is not: a substitute for sand or investment casting on very low volumes (tooling amortization kills the unit cost below ~1,000 parts/year) or for very large parts above ~10 kg where shot weight and machine tonnage spike. For those, our complete metal casting guide walks through which process fits which geometry.

Why Buyers Choose Aluminum Over Zinc or Magnesium in Die Casting

Aluminum sits between the two neighbors on the die-casting alloy chart:

• vs. zinc (Zn) — zinc die casting wins on flow length, as-cast detail and lower melt temperature (~420 °C, gentle on dies). But zinc density is ~2.7× higher than aluminum and tensile strength after casting caps around 280 MPa for common ZAMAK alloys. Where weight or thermal conductivity matter, aluminum wins on both: density 2.7 g/cm³ and thermal conductivity ~92 W/m·K for A380 vs ~110 W/m·K for zinc — and aluminum dissipates heat through the part rather than just absorbing it.
• vs. magnesium (Mg) — magnesium die casting is lighter still (~1.74 g/cm³) but requires SF₆ cover gas, tighter corrosion coatings, and most buyers treat it as a specialty play. For ~80% of automotive, industrial, and electronics housings, aluminum is the safe, commercially-stocked choice.

The macro numbers, drawn from AFS casting alloy datasheets:

The Aluminum Alloys That Actually Run in B2B Die Casting

Alloy choice is rarely driven by tensile strength alone. The buying decision is driven by pressure-tightness, machinability, and the cosmetic finish the part has to carry straight out of the die. The short list that covers ~95% of orders we run at Supro MFG:

A380 — the default workhorse

A380 (and its near twin A383) accounts for the majority of HPDC production globally because it flows well at thin walls (≥1.5 mm is realistic), holds ~325 MPa ultimate tensile strength as-cast, and resists hot cracking. For most housings, brackets, and covers where finish, pressure tightness, and dimensional stability must all coexist, A380 is the right starting point. Reference: AFS Casting Alloy Data Sheet series.

A360 — when corrosion and elevated temperature matter

A360 has higher silicon and tighter iron control than A380, which translates to better corrosion resistance in salt-spray tests and better retention of strength above ~150 °C. Choose A360 for underbody automotive brackets, marine hardware, and electronics enclosures that will sit near heat sources.

A390 — hypereutectic for wear and dimensional stability

A390 brings ~17% Si primary silicon content and is the alloy to reach for when the part must resist wear (pump bodies, pistons, certain gearbox components) or hold tight dimensions through thermal cycling. The trade is reduced fluidity — wall thickness below ~2.5 mm becomes risky — and a tougher machining cycle because of tool wear from the dispersed silicon particles.

ADC12 / A384 — the Japan and EU cross-reference

If you are quoting to European or Japanese OEMs you will see ADC12 (JIS H 5302) and EN AC-46000 / AlSi9Cu3(Fe). These are the cross-Atlantic twins of A380. Tolerances, post-casting operations, and quality documents should be written against the OEM’s reference standard rather than the closest U.S. equivalent — see how to choose a casting alloy for the full selection logic.

Cold-Chamber vs Hot-Chamber: Pick the Right Machine Class

Aluminum’s melt temperature (~660 °C) and its affinity for iron make it incompatible with the iron-rich gooseneck of a hot-chamber machine. Cold-chamber die casting is the standard, with a separate furnace ladling melt into the shot sleeve each cycle. Typical tonnage classes we run:

• 125–500 ton. Small electronics housings, brackets, LED heatsink frames. Cycle time 40–90 s.
• 800–1,600 ton. Automotive structural nodes, gearbox housings, EV inverter covers. Cycle 60–180 s.
• 2,000–4,000 ton. Large one-piece body panels, large structural castings. Cycle often 3–6 min.

For parts with shot weight above ~5 kg or projected area above ~0.5 m², an LPDC or GDC cell may be a more honest answer than forcing the geometry into HPDC and fighting porosity — see die casting vs sand casting for the deeper side-by-side.

The Four Parameter Windows That Decide 80% of Part Quality

Most common casting defects in HPDC trace back to one of four controls. Get these right and the rest is fine-tuning:

1. Melt temperature at the sleeve

Target the alloy’s recommended pouring range — typically 660–700 °C for A380 / A360 measured in the sleeve just before injection. Temperature too low: misruns, cold shuts. Too high: excessive die soldering, premature die wear, oxide inclusions that show up as hard spots downstream. Real production runs hold ±5 °C with a thermocouple at the sleeve, not the furnace.

2. Slow-shot to fast-shot transition and gate velocity

The slow-shot phase pushes metal through the sleeve without entrapping air; the switchover to fast-shot at 0.25–0.5 m/s plunger velocity is the moment that decides fill quality. NADCA’s published target for gate velocity is typically 30–50 m/s for thin-wall aluminum castings. Below that: cold shuts and unfilled features. Above: severe air entrapment and porosity that survives intensification pressure.

3. Intensification pressure and dwell time

After cavity fill, intensification pressure (typically 600–1,200 bar depending on tonnage) compresses the still-liquid core to feed shrinkage. The dwell has to last until the critical cross-section has frozen — usually 3–8 s for thin-wall parts. Hold intensification too short and you get centerline porosity that opens up in machining; hold too long and you waste cycle time.

4. Die temperature and cooling balance

Die surface temperature should sit at 180–260 °C across the cycle, with hot spots (cores, slides, deep bosses) actively heated and overheated zones (near the gate) actively cooled. Variation above ~30 °C across the die face predicts surface defects and inconsistent dimensions before you cut the part open. This is also why aluminum die casting mold design is not a CAD afterthought — it is a thermal problem solved in steel.

Tolerances, Surface Finish, and Post-Casting Operations

What you can hold straight out of the die (NADCA tolerance grade):

• Linear: ±0.15% of nominal, with a floor of ±0.1 mm for critical features under 100 mm; wider on long dimensions.
• Flatness: 0.10–0.30 mm typical on a 100 mm reference, depending on part stiffness and die temperature control.
• Surface as-cast: Ra 3.2–6.3 µm straight from the die. Vibratory deburring or shot blasting brings this to Ra 1.6–3.2 µm. Machined faces reach Ra 0.8 µm or better.
• Draft: 1° minimum on walls in the draw direction, 2° preferred for textured surfaces or long cores. Under-drafted walls drag and shorten die life.

Common secondary operations: CNC machining for sealing faces and bearing bores, impregnation for pressure-tightness (often specified by valve or pump buyers), powder coating or e-coating for cosmetic and corrosion performance. If the part is going to be anodized, talk to the die caster before tooling — silicon content above ~13% can leave cosmetic dark spots after anodizing that are not defects but alloy-characteristic.

Cost Drivers a B2B Buyer Should Actually Negotiate

Unit price for an aluminum die casting is the result of four buckets, and three of them are negotiable if you understand them:

A practical rule of thumb: for a single-cavity die running ~50,000 parts/year on A380, tooling amortization is roughly 30–45% of the unit cost in year one and drops to 10–15% by year three as volume absorbs the one-time charge. The other 60–70% is alloy, cycle, and quality — those do not amortize, so a 10% cycle-time improvement is worth more than a 10% tooling discount.

Design Rules Worth Writing Into the Drawing Notes

A die casting drawing is a contract with the shop floor. The notes that actually move yield:

• Uniform wall thickness. Aim for ±15% across adjacent sections. A 4 mm wall next to a 6 mm wall is a porosity invitation; a 4 mm next to 4.5 mm is a fillable part.
• Generous fillets. Inside corner radius ≥0.5× wall thickness, outside ≥1× wall thickness. Sharp corners are crack starters and die-life killers.
• Draft 1–2° per side. More on textured surfaces, less on short cores. Verify draft against the actual draw direction, not the printed view.
• Boss-to-wall ratio ≤0.6. A boss diameter 0.6× the surrounding wall keeps the hot spot from generating shrinkage porosity in the boss root.
• Ejector pin marks allowed on non-cosmetic, non-sealing surfaces. Specify them on the drawing rather than relying on the shop to choose. Hidden ejector marks lead to warranty disputes.

These rules look obvious written down. The reason they are worth writing is that the geometry will be reviewed by a tooling engineer, a foundry engineer, and a quality engineer — none of whom are in the same room — and the drawing is the only artifact they all read.

When Not to Choose Aluminum Die Casting

Honesty in sourcing saves a tooling project. Step away from HPDC if:

• Annual volume is below ~1,000 parts — investment casting or 3D-printed sand molds are more honest answers.
• The part has internal passages below 3 mm with no post-machining — HPDC cannot hold them consistently.
• The part must survive a pressure-tightness test without impregnation and you cannot accept a vacuum-test or impregnation step in the routing.
• You need structural certification (e.g., aerospace fatigue-critical) — HPDC’s air-entrapment porosity makes fatigue life harder to certify than investment-cast equivalents. See CNC machining vs casting for the broader make-vs-buy picture.

FAQ

What is the typical minimum wall thickness for aluminum die casting?

1.5 mm is achievable on small, evenly-heated parts with thin-wall HPDC machines. For typical 800-ton cells running A380, plan for 2.0–2.5 mm as a safer design baseline, with the option to step down locally on features that have short flow length from the gate.

How long does an aluminum die casting die last?

For H13 tool steel dies running A380 with proper die temperature control and a competent tryout phase, tool life commonly lands between 80,000 and 200,000 shots before the die needs significant refurbishment. Alloys with higher silicon (A390) or runs with marginal die lubrication will pull that number toward the lower end.

Can aluminum die castings be welded or repaired?

TIG welding on A380 / A360 castings is possible but introduces heat-affected-zone porosity and is rarely allowed for safety-critical parts. For non-critical cosmetic repair, aluminum-compatible fillers and proper preheating can close small defects, but the more durable answer is impregnation for micro-porosity or machining out and sleeving the defective boss.

Is aluminum die casting suitable for food-contact or medical parts?

Yes, with the right alloy and surface finish. A380 with a smooth machined or polished surface, no decorative coatings, and compliance with regional food-contact regulations (e.g., FDA 21 CFR, LFGB in the EU) is common for food-processing equipment housings. For medical, the conversation usually shifts to validation, traceability, and finishing rather than the casting process itself.

*Data referenced from AFS Casting Alloy Data Sheets, NADCA product specification standards, and Supro MFG shop-floor records across automotive, electronics, and industrial housing programs.