Tooling
Die casting die design and maintenance: steels, gating, die life
How die steel, gating, venting and thermal balance decide casting quality, what limits die life, and the maintenance that keeps a die making good parts.
Die steel and hardness
| Choice | Typical use | Notes |
|---|---|---|
| H13 (1.2344) | Cavity inserts, cores, slides | The standard hot work steel for aluminium die casting; usually hardened to about 44 to 48 HRC |
| Premium H13 and 1.2367 | High volume or thin walled dies | Cleaner steel and better toughness give longer life against heat checking |
| Nitriding and PVD coatings | Cores, gates, areas prone to soldering | Harder surface resists erosion and soldering |
| Holder and bolster steels | Die frames | Pre hardened steels; not in contact with metal |
Design principles that decide quality
- Gating: gate area and position set gate velocity and fill pattern; fill thin areas last only if they are vented and overflowed.
- Overflows and venting: place them where metal fronts meet and at the end of fill, so cold metal, oxides and air leave the part.
- Thermal balance: cooling lines, jet coolers and thermal control units keep each zone at its working temperature.
- Draft and radii: about 1 to 2 degrees outside and 2 to 3 degrees inside, with generous fillets, for clean ejection.
- Ejection: enough pins on strong features to push the part out without distortion.
- Simulation: flow and solidification simulation checks fill and hot spots before steel is cut.
Die life and what limits it
| Failure mode | What you see | Main remedies |
|---|---|---|
| Heat checking | Fine crack network on the die, raised pattern on castings | Preheat the die, control spray, premium steel, stress relief |
| Erosion and washout | Worn steel opposite gates | Gate design, inserts, coatings |
| Soldering | Aluminium sticking to the die | Correct iron in alloy, die temperature, release agent, coatings |
| Gross cracking | Large cracks through an insert | Avoid thermal shock, correct hardness and radii |
Aluminium dies commonly make in the order of 80,000 to 150,000 shots before major refurbishment, and well maintained premium dies can go further. Part size, wall thickness and cycle time all change the figure.
Preventive maintenance checklist
- Preheat the die before production, never start cold
- Stress relieve inserts at set shot counts during the die's life
- Clean vents, overflows and cooling lines at each change
- Check slides, cores and ejector pins for wear and flash
- Polish and repair heat checking before it marks parts
- Record shot count, repairs and dimensional checks per die
At Alcast, die and machine maintenance is recorded with the process data, and customer tooling remains the customer’s property under NDA.
Values are typical published ranges for guidance. Every part is different: process windows are set and proven for each component through trials, and the governing standard and your drawing take precedence. Reviewed by the Alcast engineering team, November 2026.
Questions engineers ask
What steel is used for aluminium die casting dies?
H13 hot work tool steel (1.2344) is the standard, usually at about 44 to 48 HRC, with premium grades and coatings for high volume or demanding dies.
How long does an aluminium die casting die last?
Commonly in the order of 80,000 to 150,000 shots before major refurbishment, depending on part size, wall thickness, steel grade and maintenance.
What causes heat checking?
Thermal fatigue from heating by molten metal and cooling by die spray on every cycle. Preheating, controlled spraying, premium steel and stress relief all slow it down.
Who owns the die?
At Alcast the customer owns the tooling they pay for. It is maintained, stored and used only for their parts.