For mold makers producing transparent and high-gloss plastic parts, material selection directly determines product appearance yield and mold service life. Many engineers confuse NAK80 mold steel with entry-level P20 steel, wasting budget or failing to meet surface standards. This article introduces core features of NAK80, contrasts it with P20, and delivers clear selection rules to solve your material confusion.
What is NAK80 Mold Steel?
NAK80 is vacuum remelted age-hardened pre-hardened steel developed by Daido Steel, delivered at uniform hardness of 37–43 HRC with no extra heat treatment needed. It supports top-tier mirror polishing up to 15,000 grit and delivers ultra-smooth EDM surfaces without extra texturing. Its internal grain is dense and even, so welded zones can be restored to consistent gloss after re-aging treatment. In terms of mold steel machining, P20 cuts 10–20% faster than NAK80 with carbide cutters , and no stress relief is required after heavy milling.
It is widely applied for PMMA lenses, PC light guide plates, cosmetic transparent packaging and automotive lamp housings, with stable mold life of 500,000–1,000,000 shots. Its main shortcoming is limited corrosion resistance; it cannot mold PVC and other corrosive plastics without surface coating.
| Comparison Items | NAK80 Mold Steel | P20 Mold Steel |
| Hardness | 37–43 HRC uniform | Uneven 28–32 HRC |
| Polishing | 15,000 grit mirror | Matte finish only |
| Mold Life | 500k–1,000k shots | ≤300k shots |
| Machining Speed | Slower | Faster |
| Cost | Higher | Low |
| Main Use | Gloss/transparent molds | Ordinary plastic molds |
Both steels are pre-hardened and ready for direct machining. NAK80’s high purity eliminates surface pinholes after polishing, while P20 can only satisfy non-aesthetic structural plastic parts without strict gloss standards. Neither steel has inherent rust resistance for corrosive resins.
Production-Oriented Material Selection Guide
Choose NAK80 mold steel if you manufacture transparent optical components, high-gloss cosmetic casings or medium-long continuous production runs with strict surface requirements. Its superior polishing capacity reduces post-polishing rework and raises finished product yield.
Stick to P20 if you only produce internal structural plastic parts, small prototype batches and items without mirror appearance demands. Using NAK80 for simple low-standard molds will create unnecessary cost waste with no performance gain.
Summary
Do not judge NAK80 merely by its higher raw price. Calculate full lifecycle costs including polishing labor, reject rate and mold replacement frequency. NAK80 is irreplaceable for high-gloss transparent plastic molds, while P20 remains the cost-effective pick for general low-appearance molding tasks.
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FAQ
Q1: Can P20 replace NAK80 for PMMA lens molds?
A1: No. P20 cannot reach mirror polishing standards, resulting in foggy, defective transparent plastic surfaces. NAK80 is mandatory for optical parts.
Q2: Does NAK80 need quenching after rough machining?
A2: No. It is pre-hardened from factory; only simple aging treatment is needed after welding to restore consistent hardness.
Q3: Can NAK80 mold PVC plastic directly?
A3: Not recommended. NAK80 has weak anti-corrosion ability. Nitriding or hard chrome plating must be done before molding corrosive materials.
Q4: What’s the biggest machining advantage of NAK80 over P20?
A4: Uniform internal metal grain, no hard spots, and EDM surfaces achieve decorative texture effect without additional etching steps.