Six commonly used materials for opening plastic molds

In plastic mold manufacturing, the choice of mold opening materials is crucial for mold performance, service life, and production costs. Here are brief introductions to six common materials:

P20 Steel

Type: Pre-hardened mold steel, domestic grade 3Cr2Mo.

Performance: Hardness 30-35HRC ex-factory, no secondary heat treatment needed; good machinability, medium polishability (up to #2000-#4000); wear resistance meets general engineering plastics' needs, with good toughness.

Application: Medium-low complexity, small-batch injection molds, such as daily necessities (bottle caps, toy casings), home appliance parts, auto interior parts, for producing common engineering plastics like ABS, PP, PE.

Mold life: About 100,000-300,000 cycles, affected by cavity number, usage and maintenance.

718H Steel

Type: Improved P20, pre-hardened mold steel, domestic grade 3Cr2NiMo.

Performance: Hardness 35-40HRC ex-factory, more uniform hardness distribution, strong deformation resistance; excellent machinability, suitable for complex structures; enhanced wear resistance, good tolerance to glass fiber/mineral filled engineering plastics, with excellent toughness and fatigue resistance.

Application: High-precision, long-life medium-large injection molds, for reinforced plastics like PA+GF, PBT, such as precision electronic parts (connectors, casings), auto functional parts (lamp covers, dashboards), home appliance high-gloss panels.

NAK80 Steel

Type: Pre-hardened mirror mold steel.

Performance: No extra heat treatment needed, high hardness; excellent polishability, meeting optical grade requirements.

Application: High-gloss, high-precision injection molds, for transparent/high-gloss plastic products like PC, PMMA, such as optical lenses, light guide plates, transparent parts of medical equipment.

H13 Steel

Type: Hot work mold steel, domestic grade 4Cr5MoSiV1.

Performance: Excellent heat resistance and thermal fatigue resistance, withstanding high-temperature cyclic stress; high toughness, better impact resistance than ordinary tool steel.

Application: Molds for high-temperature environments, processing high-temperature engineering plastics like PEEK, LCP and glass fiber reinforced plastics; producing thick-walled or fast-cycling products (auto engine covers, battery cases); manufacturing high-precision engineering parts (electronic connectors, 5G antenna covers).

Mold life: Over 1 million cycles, especially excellent under high-temperature and high-pressure conditions.

S136 Steel

Type: High-chromium stainless steel mold steel, domestic grade 4Cr13.

Performance: Strong corrosion resistance, containing 13.6% chromium, resistant to corrosive media like PVC; medium wear resistance, improvable after treatment; excellent polishability.

Application: Molds for high cleanliness and contact with corrosive plastics, used in medical and food packaging fields, such as medical devices (surgical instruments, dialysis parts), food containers (bottle caps, fresh-keeping boxes), optical lenses, mobile phone lenses.

2344 Steel

Type: Chromium-molybdenum-vanadium alloy hot work mold steel.

Performance: Excellent thermal fatigue resistance, suitable for high-temperature and high-pressure conditions, similar to H13.

Application: Molds for high-temperature engineering plastics (processing temperature > 300℃) and glass fiber reinforced plastics; competing with H13 in some scenarios, with unique advantages due to performance differences, providing more options for mold manufacturing.

When choosing plastic mold opening materials, factors like plastic type, product precision, production batch, mold life and cost should be comprehensively considered. Only accurate matching can create high-performance and cost-effective molds.