← Home | Blog

Injection Mold Steel Comparison: P20 vs 718H vs H13 vs NAK80

Published: April 27, 2026 | Category: Materials

Choosing the right steel for your injection mold is one of the most important decisions in the tooling process. The steel grade affects mold cost, production lifespan, part quality, and maintenance requirements. Here’s a comprehensive comparison of the most common mold steels used in injection molding.

P20 / P20HH (1.2311, 3Cr2Mo) — General-Purpose Pre-Hardened

P20 is the workhorse pre-hardened mold steel for general-purpose injection molding. In our tooling program it is supplied pre-hardened through the P20HH / IMPAX PX88 channel, and it suits commodity plastic parts where machining speed and cost matter more than mirror finishes. Because P20 is delivered already hardened, Taize can machine cavities, bores and slides without a post-machining heat-treatment step, which shortens overall tooling lead time on straightforward projects.

Where it is used: consumer-goods housings, interior trim with a satin finish, and prototype-to-mid-volume tools where the part allows a stable, low-cost steel. For applications requiring a high-gloss or optical surface, we escalate to one of the 718 / NAK series grades below.

718H / 718S (1.2738, 40CrMnNiMo) — Higher Hardness, Finer Polish

The 718 family (IMPAX 718S and 718HH in our steel supply) is a pre-hardened grade with noticeably higher hardness than P20 and markedly better polishability. It is the standard choice on our shop floor for tooling that must hold a smooth draw-polish across large areas — automotive interior and exterior panels, appliance housings and glass-filled compounds that would quickly dull a P20 cavity.

Why it is recommended: 718 keeps a clean polish over longer production and resists the fine wear that abrasive fillers cause. Taize selects 718H when the customer specifies a Class-A-style surface or when run volume is expected to justify the modest premium over P20.

H13 / 1.2344 / GS2344 (4Cr5MoSiV1) — Hot-Work Steel

H13 is the hot-work tool steel. It appears in our steel program through the ORVAR8407, 1.2344 and GS2344 supply channels (ASSAB, Böhler/Buderus and Saarstahl respectively). H13 retains strength at elevated temperature and resists heat checking, which is why it is used for die-casting molds and for injection tools running engineering plastics that generate sustained tool temperature.

When we move to H13: die-casting applications, molds for nylon (PA), PC and PEEK, and high-cavitation or abrasive-material tools. H13 is heat-treated after machining, so Taize runs it through our normal post-processing and inspection sequence before delivery.

NAK80 / NAK55 — Mirror-Finish Pre-Hardened

NAK80 and NAK55 are Japanese (Daido) pre-hardened grades known for excellent polishability. NAK80 supports the mirror-like cavity finish needed for transparent and optical components, while NAK55 offers similar machinability at a lighter cost profile for semi-gloss tools. Both are supplied pre-hardened and machined directly in our mold shop.

Best for: clear and translucent parts, lenses, medical-device housings and cosmetic surfaces where the cavity finish is the deciding factor rather than raw hardness.

S136 / STAVAX (1.2083-type) — Corrosion-Resistant, High Polish

For food-contact, medical and corrosive-resin applications, Taize specifies S136 / STAVAX stainless mold steel. It combines high hardness with corrosion resistance and an excellent achievable surface, and it is the grade we quote when hygiene, cleaning cycles or aggressive polymers are part of the specification.

How Taize Selects and Verifies Mold Steel

Steel selection at Taize follows the part material, surface requirement and projected run volume — not a one-size table. Before committing, our engineers confirm the grade against DFM (mold-flow and deformation analysis), then machine it on high-speed CNC (Makino/Jingdiao, to ±0.003–0.005 mm), finish with mirror EDM and slow-wire cutting (±0.003 mm), and verify with a Hexagon CMM (±0.003 mm). T1/T2 mold trials and a sample-confirmation gate happen before production release, so the grade you approve is the grade you ship.

Because properties interact with tool design, Taize does not quote a single “correct” grade. Send your 3D model and material for a free DFM-based steel recommendation.