In mold making, the material you choose for the cavity, core, and mold base directly determines the mold's lifespan, part quality, cycle time, and manufacturing cost. A mold built with the wrong steel may fail after 10,000 cycles instead of 1,000,000 cycles — or produce parts consistently out of tolerance due to thermal distortion.
China is the world's largest producer of tool steel, supplying over 60% of the global mold steel market. Chinese steel mills like Baosteel, Fushun Special Steel, Daye Steel, and Dongbei Special Steel produce grades equivalent to international standards at 30-50% lower prices. The key to successful procurement lies in understanding grade equivalency, verifying material certification, and ensuring proper heat treatment.
| Chinese Grade | Steel No. | International Equivalent | Hardness | Application |
|---|---|---|---|---|
| 3Cr2Mo | 1.2311 | P20 (AISI), 40CrMnMo7 | HRC 28-32 | General plastic molds, low-mid volume |
| 3Cr2NiMo | 1.2738 | P20+Ni, 40CrMnNiMo7 | HRC 30-36 | Large molds, polished parts, automotive |
| 4Cr5MoSiV1 | 1.2343 | H11 (AISI) | HRC 48-52 (HT) | Aluminum die casting, hot work |
| 4Cr5MoSiV1 V2 | 1.2344 | H13 (AISI) | HRC 46-52 (HT) | Die casting, forging, extrusion |
| 10Ni3MnCuAl | NAK80 | NAK80 equivalent | HRC 37-43 | High-polish lenses, clear parts |
| Cr12MoV | 1.2379 | D2 (AISI) | HRC 58-62 (HT) | Stamping dies, cold work |
| 7CrSiMnMoV | CH-1 | No direct equivalent | HRC 56-60 (HT) | Stamping, cold extrusion |
| CrWMn | 5CrWMn | O1 (AISI) | HRC 58-62 (HT) | Small precision dies, gauges |
| 38CrMoAl | 1.8509 | Nitriding steel | HV 900-1100 case | Wear-resistant sliding parts |
| Mold Type / Volume | Recommended Steel | Hardness | Expected Life |
|---|---|---|---|
| Prototype / Low vol (Up to 10K) | Al 7075-T6 or P20 (3Cr2Mo) | HRB 85-90 / HRC 28-32 | 1K-10K cycles |
| Medium vol (10K-100K) | 3Cr2NiMo (1.2738) | HRC 30-36 | 50K-100K cycles |
| High vol (100K-500K) | H13 (1.2344) or S136 (1.2083) | HRC 48-52 | 300K-1M cycles |
| Abrasive plastics (glass-filled) | S136 / D2 + TiN coating | HRC 56-62 | 500K-2M cycles |
| Optical / high-polish | NAK80 (10Ni3MnCuAl) | HRC 37-42 | 100K-500K cycles |
Die casting dies face extreme conditions: molten aluminum at 660-700°C injected at 200-800 bar. H13 (1.2344) is the global standard. For longer life, specify premium-grade H13 (vacuum degassed, ESR refined) at HRC 46-50. A good H13 die achieves 80,000-150,000 shots before major heat checking. For brass die casting (900-1000°C), use TZM or Anviloy for core pins with H13 cavities; expect 5,000-20,000 shots before replacement.
D2 (Cr12MoV) is the most widely used stamping die material in China. For high-speed stamping (>300 SPM), specify powder metallurgy steel (e.g., ASP23 or Chinese PM HSS grades) for superior wear resistance. Carbide (WC-Co) inserts at $30-$80/kg are commonly used for high-volume progressive dies — about 50% of the Western price.
Heat treatment quality varies dramatically between Chinese workshops. A mold from imported Bohler steel can be ruined by poor HT at a local shop. Key specs to communicate:
| Grade | Pre-heat | Austenitizing | Tempering | Target HRC | Quench |
|---|---|---|---|---|---|
| P20 (3Cr2Mo) | 650-700°C | 840-880°C | 580-620°C | 28-32 | Oil/air |
| 1.2738 (3Cr2NiMo) | 650-700°C | 840-880°C | 560-620°C | 30-36 | Oil |
| H13 (1.2344) | 650-700°C | 1020-1050°C | 540-590°C (2×) | 46-52 | Air/N2 gas |
| D2 (Cr12MoV) | 600-650°C | 960-1020°C | 180-220°C or 500-540°C | 58-62 | Oil/air |
| S136 (1.2083) | 650-700°C | 980-1030°C | 200-250°C (3×) | 48-52 | Oil |
Critical: For die casting H13, request vacuum heat treatment with high-pressure gas quenching (N2 at 2-5 bar) to prevent decarburization and ensure uniform hardness. Chinese HT shops specializing in mold steel are concentrated in Shenzhen (Bao'an), Dongguan (Changan), and Ningbo.
| Treatment | Hardness | Application | Cost (China) |
|---|---|---|---|
| Nitriding (Gas/PVD) | HV 900-1200 | Sliding surfaces, die cast core pins | $0.50-$2/kg |
| TiN Coating (PVD) | HV 2200-2500 | Injection cavities (abrasive plastics) | $3-$8/kg |
| TiCN Coating | HV 2800-3300 | High-wear stamping dies | $5-$12/kg |
| CrN Coating | HV 1800-2200 | Die casting (anti-soldering) | $4-$10/kg |
| DLC Coating | HV 3000-4000 | High-polish molds, no-lube apps | $8-$20/kg |
| Hard Chrome | HRC 65-70 | Wear repair, anti-corrosion | $2-$5/kg |
| Type | Key Suppliers | Location |
|---|---|---|
| Mold Steel Mills | Baosteel Special Steel, Fushun, Daye, Dongbei, Xining | Shanghai, Liaoning, Hubei, Qinghai |
| Mold Base Suppliers | LKM (Lung Kee), FCS, Hasco China, DME China | Shenzhen, Kunshan, Dongguan |
| Heat Treatment Shops | Shenzhen HT Center, Dongguan JieLi, Kunshan KaiXing | Major mold clusters |
| PVD Coating Centers | Balzers China, Ionbond China, Platit China | Shenzhen, Shanghai, Suzhou |
| Component | Share | Notes |
|---|---|---|
| Mold Base | 15-25% | LKM/FCS standard base: $200-$2,000 |
| Cavity Steel | 20-35% | Domestic P20: $2-4/kg; Imported H13: $8-15/kg |
| Core Steel | 10-20% | Same grade, lower polish requirement |
| Slides / Lifters | 8-15% | H13 or S136 for moving components |
| Ejector Pins | 5-10% | DME/Hasco standard: $2-$15 each |
| Heat Treatment | 3-8% | Vacuum HT for H13: $200-$800 |
| Surface Coating | 2-8% | TiN cavity coating: $100-$500 |
Q: Can I trust Chinese domestic steel to be equivalent to Bohler/Uddeholm?
A: Yes, for standard applications. Baosteel's 3Cr2NiMo (1.2738 equivalent) and Fushun's H13 are reliable for 80% of mold applications. For extreme requirements (mirror-polish optical molds, high-pressure die casting), imported Bohler M333 or Uddeholm Elmax may still be justified. The price gap has narrowed — imported steel is only 20-40% more than top Chinese grades now, compared to 100-200% ten years ago.
Q: What is the most common steel substitution fraud in China?
A: Labeling 3Cr2Mo (P20) as 3Cr2NiMo (1.2738). The extra nickel in 1.2738 provides better through-hardening and polishability. Verify by checking Ni content on the MTC — 3Cr2Mo has <0.3% Ni, while 1.2738 has 0.8-1.2% Ni. Another common trick: selling un-heat-treated steel as "pre-hardened." Always verify the actual hardness with your own tester.
Q: How should I specify material requirements in an RFQ?
A: Include: (1) Chinese steel grade and international equivalent, (2) steel mill name (or "equivalent approved"), (3) required hardness range, (4) MTC requirement (yes/no), (5) heat treatment spec (vacuum HT, double temper), (6) UT requirement and acceptance criteria. Example: "Cavity: 3Cr2NiMo (1.2738), Baosteel or approved equivalent, pre-hardened HRC 30-36. MTC required. Vacuum HT with double temper. UT per ASTM A388."
Q: Should I buy imported or domestic steel for my first mold order?
A: For the first order from a new Chinese mold maker, consider paying the premium for imported steel (Bohler or Uddeholm). This removes one variable — if the mold fails, it's not because of poor steel. Once you trust the mold maker's process and material handling, switch to top Chinese grades for subsequent orders. The cost savings can be 30-50% on material alone.
Q: What is the shelf life of mold steel?
A: Indefinite if stored properly (indoor, dry, oiled surface). However, pre-hardened steel can age-soften slightly over years — the drop is typically <1 HRC over 5 years. The bigger risk is surface rust pitting, which creates defects transferred to molded parts. For long-term storage, request the steel to be rust-proof coated (VCI paper + oil).