No. 6555 Songze Avenue, Chonggu Town, Qingpu District, Shanghai, China
What materials can be used to make die casting molds?
Introduction: The Steel Behind the Spark
Hi, I’m Barry Zeng, a manufacturing engineer at Shanghai Yunyan Prototype & Mould Manufacture Factory. If you’ve ever wondered what kind of superhero metal can withstand molten aluminum shot at 1,000 miles per hour, day after day — you’re about to find out. The materials used to make die casting molds are nothing like the steel in your kitchen knives or car frame. They’re specially formulated to resist heat, pressure, wear, and thermal fatigue. In this guide, I’ll walk you through the most common materials for die casting molds, from the workhorse H13 to premium grades like Dievar, as well as stainless steels, copper alloys for cooling, and even 3D‑printed options. I’ll also share some hard‑learned lessons about what happens when you pick the wrong steel. (Spoiler: it involves cracked molds and sad engineers.) Grab a coffee, and let’s dive in.
Chapter 1: What Makes a Good Die Casting Mold Material?
Before we talk about specific materials, let’s understand what a die casting molds material needs to do. The mold faces:
- Extreme heat: Molten aluminum is around 650°C (1200°F). Zinc is cooler at 400°C, but still hot enough to make you reconsider your career choice.
- Thermal cycling: Heat up to 650°C, then cool down to 200°C, then heat up again. Every. Single. Cycle. This repeats thousands or millions of times. It’s like putting your hand in an oven, then ice water, then back in the oven. Fun, right?
- High pressure: Die casting injection pressures range from 10,000 to 20,000 psi. That’s like having a elephant stand on a postage stamp.
- Erosion: Molten metal flowing at high velocity erodes the steel over time, like a river cutting through rock.
- Soldering (sticking): Aluminum loves to weld itself to steel. The mold material needs to resist this.
A good mold steel must balance hardness (wear resistance), toughness (resistance to cracking), thermal conductivity (to cool quickly), and resistance to heat checking (those tiny surface cracks). It’s a tall order. But the right material makes all the difference.
Chapter 2: H13 — The Workhorse (You Can’t Go Wrong Here)
If die casting molds had a Hall of Fame, H13 would be the first inductee. It’s the most common material for aluminum die casting molds, and for good reason.
What is H13?
H13 (DIN 1.2344, AISI H13) is a chromium hot‑work tool steel. Its composition: 0.35–0.45% carbon, 5.0–5.5% chromium, 1.2–1.5% molybdenum, and 0.8–1.2% vanadium.
Properties:
- Hardness after heat treatment: 46–52 HRC
- Good toughness (doesn’t crack easily)
- Excellent resistance to thermal fatigue
- Good machinability (in annealed condition)
- Reasonable cost
Best for: Aluminum and magnesium die casting molds with expected life of 50,000–150,000 shots. Perfect for automotive brackets, electronics housings, and general industrial parts.
The catch: H13 will eventually develop heat checking after 50,000–100,000 cycles. For high‑volume applications (500,000+ shots), you’ll want to upgrade to a premium grade.
Pro tip: Always buy H13 from a reputable supplier with certified chemistry. Cheap “H13” from unknown sources might be mystery metal. I learned this the hard way — the mold cracked after 10,000 shots. The supplier ghosted me. I cried a little. Now I only buy certified material.
Chapter 3: Premium Hot‑Work Steels — For When You Need a Million Shots
When H13 isn’t enough, it’s time to bring in the big guns. Premium hot‑work steels offer longer life, better heat checking resistance, and higher toughness.
3.1 Dievar (Uddeholm)
Dievar is the rock star of die casting mold steels. It’s a premium H13 variant with exceptional purity and microstructure. Benefits:
- 2–3× longer life than standard H13
- Superior resistance to heat checking and gross cracking
- Excellent toughness at high hardness (48–52 HRC)
- Better resistance to soldering
Best for: High‑volume aluminum die casting molds (500,000–1,000,000+ shots). Used for engine blocks, transmission housings, and complex structural parts.
Cost: About 2× standard H13. But when you’re running a million parts, the tooling cost per part is still pennies. And you don’t have to stop production to replace a cracked mold. Worth every penny.
3.2 QRO 90 (Uddeholm)
QRO 90 is another premium hot‑work steel with high temperature strength. It’s often used for cores and inserts that experience the most severe thermal exposure. Think of it as the special forces team of mold steels — you only call them in for the toughest jobs.
3.3 1.2367 (X38CrMoV5-3)
This European grade has higher molybdenum and vanadium content than H13. It offers better high‑temperature strength and wear resistance. Popular in Europe for high‑pressure die casting of aluminum and magnesium. It’s like H13’s slightly more athletic cousin.
Chapter 4: P20 — The Low‑Volume Option (But Don’t Get Greedy)
P20 (DIN 1.2738, AISI P20) is a pre‑hardened mold steel with hardness of 30–36 HRC. It is NOT a hot‑work steel — it lacks the heat resistance of H13. So why would anyone use it for die casting molds?
When to use P20:
- Prototype molds (100–1,000 shots)
- Low‑volume production (up to 5,000 shots for small parts)
- Zinc die casting (lower temperatures — zinc melts at 400°C)
- Permanent mold casting (gravity casting, not high pressure)
The danger: Do NOT use P20 for high‑pressure aluminum die casting. The mold will heat check within 1,000–5,000 shots. I’ve seen it happen. It’s not pretty. The mold looks like a dried riverbed, and your parts look like garbage. Just don’t.
Pro tip: If a customer asks for a P20 mold for aluminum die casting, I politely decline. Then I explain why. Then I show them pictures of cracked P20 molds. They usually upgrade to H13.
Chapter 5: Stainless Steels — For Corrosive Alloys and Clean Rooms
Sometimes you need a die casting molds that won’t rust. That’s where stainless steel comes in.
- 420 (DIN 1.2083): Martensitic stainless, hardenable to 48–52 HRC. Used for molds that require mirror polish or corrosion resistance. Great for medical devices and food contact parts.
- 136 (DIN 1.2083 ESR): Electro‑slag remelted version of 420. Higher purity, better polishability. Expensive, but worth it for cosmetic parts.
- 316 (DIN 1.4401): Austenitic stainless, cannot be hardened. Used for prototype molds only. It’s like the tofu of mold steels — soft, but sometimes that’s what you need.
When to use stainless: Medical devices, food processing equipment, pharmaceutical packaging, or any application where corrosion resistance is critical.
The trade‑off: Stainless steel has lower thermal conductivity than H13 — about 25 W/m·K vs. 28 W/m·K for H13. That means longer cycle times. But if you need corrosion resistance, you don’t have a choice.
Chapter 6: Copper Alloys — For Cooling (The Unsung Heroes)
Most of the mold is made of steel, but some areas — especially cores and hot spots — benefit from copper alloys.
- Beryllium copper (BeCu, C17200): Extremely high thermal conductivity (105–130 W/m·K, about 4× steel). It pulls heat out of the cavity like a vacuum cleaner. Used for inserts in hot spots.
- AMPCOLOY 940 / 944: High‑strength copper alloys with good wear resistance. Used for core pins and thin sections.
Warning: Beryllium copper is toxic when machined (beryllium dust is nasty). We use it only when necessary, with strict dust control. It’s the hazardous materials suit of mold steels — effective, but you don’t want to mess around with it.
Chapter 7: 3D‑Printed Mold Components — The New Kid on the Block
With metal 3D printing (DMLS), we can now print mold components — especially conformal cooling channels — that are impossible to machine. Materials for printed molds include:
- Maraging steel (MS1, 1.2709): Very high strength, good hardness (50–55 HRC after heat treatment). Used for mold inserts with complex cooling channels.
- H13 (printed): Same chemistry as wrought H13, but properties can vary. Getting better every year.
- Stainless 316L (printed): For corrosion‑resistant inserts.
3D‑printed mold components are expensive, but they allow cooling channels that follow the part contour perfectly. Cycle time reductions of 20–40% are common. The payback period is often under 6 months. If you’re running high volumes, it’s a no‑brainer.
Chapter 8: Material Selection Guide — What Steel for What Job?
| Application | Recommended Steel | Expected Mold Life |
|---|---|---|
| Prototype / low volume aluminum (<5,000 shots) | P20 or H13 | 5,000–10,000 |
| Medium volume aluminum (50k–150k shots) | H13 | 50k–150k |
| High volume aluminum (150k–500k shots) | Premium H13 (Dievar) | 150k–500k |
| Very high volume aluminum (500k–1M+ shots) | Dievar + PVD coating | 500k–1M+ |
| Zinc die casting | H13 or P20 | 100k–500k |
| Magnesium die casting | H13 or Dievar | 50k–200k |
| Corrosive environment (medical, food) | 420/136 stainless | 50k–200k |
Chapter 9: Case Study — The $50,000 Lesson in Steel Selection
A client came to us with a broken die casting mold. They had used P20 steel for an aluminum automotive part — 5,000 shots in, the mold was covered in heat checks. Parts were scrap. They had lost $30,000 in downtime.
We rebuilt the mold in H13 with nitriding and AlCrN coating. Cost: $18,000. The new mold ran 150,000 shots with no issues. The client saved $200,000 in avoided downtime and scrap.
The moral: Don’t cheap out on mold steel. You might save $5,000 upfront, but you’ll pay $50,000 later. Ask me how I know. (Actually, don’t. I still have nightmares.)
Chapter 10: Summary — Choosing the Right Material for Your Die Casting Mold
- ☐ H13 is the workhorse for most aluminum and magnesium die casting molds.
- ☐ Premium grades (Dievar, QRO 90) offer 2–3× longer life for high‑volume production.
- ☐ P20 is for prototypes and low‑volume zinc only — never for aluminum die casting.
- ☐ Stainless steels (420, 136) are for corrosive applications (medical, food).
- ☐ Copper alloys (beryllium copper) are for cooling inserts in hot spots.
- ☐ 3D‑printed maraging steel enables conformal cooling channels.
- ☐ Always buy certified steel from reputable suppliers. Mystery metal = mystery failures.
Conclusion: The Right Steel Makes the Mold — The Wrong Steel Breaks It
Choosing the right material for die casting molds is not a place to cut corners. H13 is the industry standard for a reason. Premium grades like Dievar are worth every penny for high‑volume production. And for the love of all that is holy, don’t use P20 for aluminum die casting. We’ve been designing and building die casting molds for 12 years. Send me your part drawing, material (aluminum, zinc, magnesium), and annual volume. I’ll recommend the optimal mold steel, provide a free DFM report, and quote your mold — within 24 hours. Let’s build a mold that lasts.
👇 Need a Die Casting Mold? Let’s Pick the Right Steel Together.
Send me your CAD file, alloy, and annual volume. I’ll recommend the best mold steel — H13, Dievar, P20, or stainless — and provide a free DFM report and quote within 24 hours. No obligation, just honest advice.
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Call Barry
I answer the phone myself
(No robots, I promise)
+86 138 1894 4170
🌐
Visit Our Site
Download “Die Casting Mold Steel Guide”
(Steel comparison chart, heat treatment)
Not sure which steel fits your volume? Just say: “Barry, here’s my annual quantity — what mold steel should I use?” I’ll give you an honest recommendation. (Probably with a bad joke.)
🔥 Die Casting Molds — The Right Steel for the Right Job 🔥
P.S. Mention “mold steel guide” when you email, and I’ll send you a steel comparison chart, a heat treatment checklist, and a photo of my cat. You’re welcome.
Barry Zeng
Senior Manufacturing Engineer, Shanghai Yunyan Prototype & Mould Manufacture Factory
(12 years of matching the right steel to the right die casting mold. I’ve made mistakes so you don’t have to.)
