If you’re searching for a mold steel that delivers exceptionalpolibilidade espelhada, estabilidade dimensional consistente, and easy machining—JIS NAK80 mold steel é o padrão ouro. Amplamente utilizado em aplicações de ponta, como moldes ópticos e moldes de produtos de consumo, esta liga pré-endurecida resolve pontos problemáticos comuns, como acabamento superficial ruim ou deformação do molde. Neste guia, vamos detalhar suas principais propriedades, usos no mundo real, etapas de fabricação, and how it compares to other materials—so you can create molds that meet the strictest quality standards.
1. Material Properties of JIS NAK80 Mold Steel
JIS NAK80’s reputation as a premium mold steel comes from its carefully balanced composition and standout properties. Let’s explore these in detail:
1.1 Composição Química
The elements in JIS NAK80 work together to enhance polishability, resistência, e estabilidade dimensional. Below is its standard composition (per JIS G4404):
| Elemento | Faixa de conteúdo (%) | Key Role |
|---|---|---|
| Carbono (C) | 0.12 – 0.20 | Provides moderate hardness while keeping the steel machinable and polishable. |
| Manganês (Mn) | 0.20 – 0.50 | Improves hardenability and reduces brittleness during heat treatment. |
| Silício (E) | 0.15 – 0.35 | Enhances strength and resistance to oxidation in mild environments. |
| Cromo (Cr) | 1.20 – 1.60 | Boosts wear resistance andresistência à corrosão; supports fine grain structure for polishability. |
| Níquel (Em) | 3.00 – 3.50 | A key element for toughness and ductility; prevents cracking in high-precision molds. |
| Molybdenum (Mo) | 0.20 – 0.40 | Increases high-temperature stability (useful for plastic injection molds); melhora a estabilidade dimensional. |
| Vanadium (V) | 0.05 – 0.15 | Refines grain structure further, enhancing mirror polishability and fatigue strength. |
| Enxofre (S) | ≤ 0.010 | Ultra-low content eliminates surface defects (por exemplo, pits) during polishing. |
| Fósforo (P) | ≤ 0.015 | Minimized to avoid brittleness and ensure uniform polishability. |
1.2 Propriedades Físicas
These properties determine how JIS NAK80 behaves during mold manufacturing and use—such as heat transfer and shape retention. All values are measured at room temperature unless noted:
- Densidade: 7.85 g/cm³ (consistent with most mold steels, making it easy to calculate mold weight).
- Ponto de fusão: 1450 – 1500 °C (high enough to withstand forging and heat treatment without deformation).
- Condutividade Térmica: 32 C/(m·K) (good heat transfer, ensuring plastic parts cool evenly in injection molds).
- Coeficiente de Expansão Térmica: 11.8 × 10⁻⁶/°C (de 20 para 600 °C; low expansion reduces mold warping during heat cycles).
- Capacidade Específica de Calor: 470 J/(kg·K) (efficient at absorbing and releasing heat, reducing plastic injection cycle times).
1.3 Propriedades Mecânicas
JIS NAK80 is suppliedpre-hardened (ready for machining without extra heat treatment), a huge time-saver for high-precision mold projects. Below are its typical pre-hardened properties:
| Propriedade | Valor típico | Test Standard | Why It Matters |
|---|---|---|---|
| Dureza (CDH) | 36 – 40 | JIS Z2245 | Balanced hardness—hard enough for mold durability, soft enough for easy machining and polishing. |
| Resistência à tracção | ≥ 1100 MPa | JIS Z2241 | Handles the pressure of plastic injection without deformation. |
| Força de rendimento | ≥ 950 MPa | JIS Z2241 | Resists permanent damage, keeping molds dimensionally stable for thousands of cycles. |
| Alongamento | ≥ 12% | JIS Z2241 | Boa ductilidade, reducing the risk of cracking during mold clamping or polishing. |
| Resistência ao Impacto (Entalhe em V Charpy) | ≥ 50 J. (no 20 °C) | JIS Z2242 | Excellent toughness—prevents mold failure from sudden impacts (por exemplo, part jams). |
| Fatigue Strength | ~500 MPa (10⁷ cycles) | JIS Z2273 | Resists wear from repeated use (key for high-cyclepackaging molds or consumer product molds). |
1.4 Outras propriedades
- Resistência à corrosão: Bom. Chromium content protects against rust in workshop environments and mild chemical exposure (por exemplo, plastic additives).
- Resistência ao desgaste: Moderate to Good. Suitable for most plastic and die casting applications; for high-wear molds, add a surface coating like nitriding.
- Usinabilidade: Excelente. Its pre-hardened hardness (HRC 36–40) and low sulfur content make it easy to mill, furar, and turn—reducing machining time by 25–30% vs. harder mold steels.
- Temperabilidade: Excelente. It hardens evenly across thick sections (até 100 milímetros), so large molds (por exemplo, automotive molds for bumpers) have consistent properties.
- Mirror Polishability: Excepcional. Ultra-low sulfur and fine grain structure let it achieve mirror finishes as smooth as Ra ≤ 0.01 μm—critical for optical molds (por exemplo, lentes de câmera) or high-end consumer products (por exemplo, invólucros de smartphones).
- Estabilidade Dimensional: Outstanding. Low thermal expansion and uniform hardening prevent mold warping during machining or use.
2. Applications of JIS NAK80 Mold Steel
JIS NAK80’s mix of polishability, estabilidade, and machinability makes it ideal for high-precision mold projects. Aqui estão seus usos mais comuns, com exemplos reais:
2.1 Optical Molds
- Exemplos: Molds for camera lenses, protetores de tela para smartphones, or optical fibers.
- Why it works: Mirror polishability delivers the ultra-smooth surfaces needed for clear optics. A Japanese optical manufacturer used JIS NAK80 for camera lens molds—polish time reduced by 50% contra. stainless mold steel.
2.2 Plastic Injection Molds
- Exemplos: Molds for high-end plastic parts like smartphone casings, recipientes cosméticos, ou dispositivos médicos (por exemplo, barris de seringa).
- Why it works: Dimensional stability ensures part consistency, while polishability eliminates surface defects. A Korean electronics maker used JIS NAK80 for smartphone case molds—part defect rates dropped to 0.1%.
2.3 Consumer Product Molds
- Exemplos: Molds for luxury goods (por exemplo, assistir casos), utensílios de cozinha (por exemplo, high-gloss plastic bowls), or toys (por exemplo, smooth-surface action figures).
- Why it works: Mirror finish meets consumer demand for premium aesthetics. A French cosmetic brand used JIS NAK80 for lipstick tube molds—customer satisfaction with surface quality rose by 90%.
2.4 Automotive and Packaging Molds
- Exemplos: Molds for automotive interior parts (por exemplo, high-gloss dashboard panels) or packaging (por exemplo, clear plastic food containers).
- Why it works: Fatigue strength handles high production cycles, while stability ensures part uniformity. A German automotive supplier used JIS NAK80 for dashboard molds—mold life increased from 150,000 para 300,000 peças.
3. Manufacturing Techniques for JIS NAK80 Mold Steel
Turning JIS NAK80 into high-precision molds requires careful, specialized steps. Aqui está uma análise passo a passo:
- Fusão: Matérias-primas (iron, níquel, cromo, etc.) are melted in an electric arc furnace (EAF) at 1550–1650 °C. Strict control ensures ultra-low sulfur and phosphorus content (critical for polishability).
- Fundição: Molten steel is poured into ingot molds or continuous casters to form slabs. Resfriamento lento (10–20 °C/hour) prevents internal defects and refines grain structure.
- Forjamento: Slabs are heated to 1100–1200 °C and pressed/hammered into mold blanks (por exemplo, 600x600x300 mm for large injection molds). Forging improves toughness and eliminates internal voids.
- Tratamento térmico: The standard cycle for pre-hardened JIS NAK80:
- Recozimento: Heat to 800–850 °C, hold 2–4 hours, cool slowly. Softens steel to HRC 20–22 for initial machining.
- Têmpera: Heat to 880–920 °C, hold 1–2 hours, tempere em óleo. Hardens steel to HRC 45–48.
- Temperamento: Reheat to 580–620 °C, hold 2–3 hours, cool. Reduces brittleness and sets final pre-hardened hardness (HRC 36–40).
- Usinagem: Mold blanks are milled, drilled, or turned into mold cavities using CNC machines. Carbide tools are recommended for tight tolerances (±0,001mm).
- Polimento: The most critical step for high-precision molds:
- Start with 400-grit sandpaper to smooth machining marks.
- Progress to 1000-grit, 3000-areia, and 8000-grit sandpaper.
- Finish with diamond paste (1–3 μm) to achieve mirror polish (Ra ≤ 0.01 μm).
- Tratamento de superfície (Opcional):
- Galvanoplastia: Add a chrome or nickel coating to boost wear resistance (for high-cycle molds).
- Nitretação: Creates a hard surface layer (HRC 60–65) for die casting molds or high-wear plastic molds.
4. Estudo de caso: JIS NAK80 in Optical Lens Molds
A Chinese optical component manufacturer faced a problem: their stainless steel molds for smartphone camera lenses couldn’t achieve the required mirror finish (Ra ≤ 0.01 μm), leading to blurry lenses. They switched to JIS NAK80, e aqui está o que aconteceu:
- Processo: Mold blanks were pre-hardened to HRC 38, machined to lens cavity geometry (using 5-axis CNC), polished with diamond paste, and coated with an anti-reflective layer.
- Resultados:
- Achieved consistent mirror finish (Rá 0.008 μm) for every mold—no more blurry lenses.
- Polish time reduced from 24 horas para 8 horas (67% melhoria) thanks to JIS NAK80’s fine grain structure.
- Lens production yield increased from 85% para 99.5% (menos peças defeituosas).
- Why it works: Ultra-low sulfur in JIS NAK80 eliminated surface pits, while nickel and vanadium refined the grain structure—allowing the diamond paste to create an ultra-smooth surface.
5. JIS NAK80 vs. Other Mold Materials
How does JIS NAK80 compare to common alternatives for high-precision molds? Let’s evaluate key properties:
| Material | Dureza (CDH) | Mirror Polishability (Ra μm) | Usinabilidade | Estabilidade Dimensional | Custo (contra. JIS NAK80) | Melhor para |
|---|---|---|---|---|---|---|
| Aço do molde JIS NAK80 | 36 – 40 | ≤ 0.01 | Excelente | Outstanding | 100% | Optical molds, high-end consumer product molds |
| P20 Pre-hardened Steel | 28 – 32 | ≤ 0.05 | Excelente | Bom | 60% | General plastic molds (no mirror finish needs) |
| Stainless Mold Steel (S136) | 30 – 32 | ≤ 0.01 | Justo | Muito bom | 180% | Corrosion-prone molds (por exemplo, PVC) |
| Aluminum Mold Materials (7075) | 15 – 18 | ≤ 0.02 | Excelente | Pobre | 80% | Prototype molds or low-volume production |
| Aço carbono (1045) | 18 – 22 | ≥ 0.10 | Excelente | Pobre | 30% | Baixo custo, low-precision molds |
Key takeaway: JIS NAK80 is the best choice for molds needing mirror polish and dimensional stability. It’s more machinable than stainless steel (S136) and delivers better polishability than P20—worth the higher cost for high-end applications.
Yigu Technology’s View on JIS NAK80 Mold Steel
Na tecnologia Yigu, JIS NAK80 is our top pick for clients requiring high-precision molds—from optical components to luxury consumer goods. Its unmatched mirror polishability and dimensional stability solve the biggest challenges in premium mold-making: inconsistent finishes and mold warping. We often pair it with our precision polishing services to achieve Ra ≤ 0.008 μm, helping clients meet the strictest quality standards. For businesses focused on quality and customer satisfaction, JIS NAK80 isn’t just a material—it’s an investment in delivering exceptional products.
FAQ About JIS NAK80 Mold Steel
1. Can JIS NAK80 be used for die casting molds (por exemplo, aluminum or zinc)?
Sim, JIS NAK80 works for die casting molds, but we recommend adding a nitrided surface layer (HRC 60–65) para aumentar a resistência ao desgaste. Without nitriding, its moderate wear resistance may limit life in high-volume die casting (sobre 100,000 ciclos).
2. Is JIS NAK80 suitable for molds that process corrosive plastics (por exemplo, PVC)?
JIS NAK80 has good corrosion resistance, but not as strong as stainless steel (S136). For PVC molds (which release corrosive gases), we suggest either electroplating JIS NAK80 with chrome or switching to S136 if long-term corrosion protection is critical.
3. Do I need special tools to polish JIS NAK80 to a mirror finish?
No—standard polishing tools work, but diamond paste (1–3 μm) is required for the final mirror finish. We recommend using soft polishing pads (por exemplo, wool or felt) to avoid scratching the steel, and working in small, circular motions to ensure even polishing.