Mold Steel

Selecting the correct mold steel is the foundational engineering choice that dictates tool life, thermal cycle times, surface polishability, and corrosion resistance during plastic injection molding. Tool steel choices range from pre-hardened P20 and 718H for cost-effective medium-volume production to fully hardened S136 stainless steel and H13 tool steel (52+ HRC) for 1,000,000+ shot Class 101 molds. At Jucheng Precision, a certified ISO 9001 and IATF 16949 contract manufacturer, we specialize in high-hardness steel mold building. Utilizing 25+ in-house 5-axis CNC machining centers, vacuum heat treatment, and SPI A-1 diamond mirror polishing, we machine steel cavities to ±0.005mm tolerances verified by Zeiss CMM inspection.

Mirror-polished-S136-stainless-steel-injection-mold-cavity

Our available materials

P20 Mold Steel

Eliminating post-machining heat treatment distortion while securing an economical tooling solution for medium-volume production runs requires an engineered pre-hardened alloy, which AISI P20 (DIN 1.2311) mold steel delivers. Pre-hardened to a uniform 28–34 HRC, P20 steel provides excellent machinability, uniform core hardness, and good polishability up to an SPI B-2 finish. At Jucheng Precision, a certified ISO 9001 and IATF 16949 contract manufacturer, we specialize in 5-axis CNC machining of P20 steel mold cavity inserts. Delivering tool shot lives up to 500,000 cycles, our P20 injection molds process commodity and engineering thermoplastics, verified by Zeiss CMM inspection.

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H13 Tool Steel

Resisting severe abrasive tool wear from fiber-reinforced compounds and enduring rapid thermal cycling without heat checking requires a high-hardness hot-work alloy, which AISI H13 (DIN 1.2344) tool steel delivers. Vacuum hardened and triple tempered to 50–54 HRC, H13 chromium-molybdenum-vanadium steel provides exceptional thermal shock resistance, high compressive strength, and unyielding gate wear resistance. At Jucheng Precision, a certified ISO 9001 and IATF 16949 contract manufacturer, we specialize in 5-axis CNC machining of H13 steel mold cavities. Delivering class 101 tool shot lives exceeding 1,000,000 cycles, our H13 molds reliably process high-temperature super-polymers and abrasive filled resins, verified by Zeiss CMM inspection.

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S136 Mold Steel

Eliminating microscopic surface pitting and protecting mold cavity walls from acidic outgassing in high-purity medical and optical molding requires an electroslag-remelted stainless alloy, which S136 mold steel delivers. Vacuum hardened to 48–52 HRC, ESR S136 stainless tool steel contains 13.6% chromium, offering exceptional resistance to cooling line rust and corrosive polymer degradation. At Jucheng Precision, a certified ISO 9001 and ISO 13485 contract manufacturer, we specialized in 5-axis CNC machining and diamond mirror polishing of S136 steel mold inserts. Achieving an SPI A-1 optical surface finish, our S136 production molds guarantee over 1,000,000 shots verified by Zeiss CMM inspection.

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718 Mold Steel

Eliminating thermal quench distortion in large-scale mold blocks while securing superior core hardness uniformity over standard P20 requires an advanced nickel-alloy pre-hardened steel, which 718H (DIN 1.2738) mold steel delivers. Pre-hardened to a uniform 32–38 HRC, 718H steel contains nickel additives that ensure consistent hardness across thick tool sections up to 400mm depth, taking a fine SPI B-1 polish and crisp photo-etched textures. At Jucheng Precision, a certified ISO 9001 and IATF 16949 contract manufacturer, we specialize in 5-axis CNC machining of large 718 steel mold cavities. Delivering tool shot lives up to 500,000+ cycles, our 718 molds reliably process automotive panels and appliance enclosures, verified by Zeiss CMM inspection.

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NAK80 Mold Steel

Achieving an optimal balance between pre-hardened core steel strength, pinhole-free EDM spark-eroded finishes, and mirror-level surface polishability without post-machining heat treatment distortion requires a precipitation-hardened alloy, which NAK80 mold steel delivers. Age-hardened at the mill to a uniform 37–43 HRC, NAK80 (Cu-Al-Ni alloyed steel) provides exceptional machinability, uniform grain structure, and high weldability. At Jucheng Precision, a certified ISO 9001 and IATF 16949 contract manufacturer, we specialize in 5-axis CNC machining and precision EDM eroding of NAK80 steel mold inserts. Delivering tool shot lives exceeding 500,000 cycles, our NAK80 molds produce high-gloss cosmetic enclosures and clear optical lenses verified by Zeiss CMM inspection.

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Selecting the correct mold steel is the single most critical engineering decision in Fabricación de Moldes Personalizados. From pre-hardened steels for cost-effective pilot runs to fully hardened stainless steels for 1,000,000+ cycle production tools, choosing the right alloy dictates part surface finish, tool longevity, and thermal cycle efficiency.

Tool Steel Grade Performance & HRC Hardness Matrix

We machine and heat-treat premium tool steel alloys from certified European and Asian steel mills to match your production volume and resin chemistry:

Tool Steel Grade Hardness (HRC) Corrosion & Wear Resistance Guaranteed Tool Shot Life
S136 Stainless Steel 48 – 52 HRC (Hardened) High chromium stainless steel. Exceptional corrosion resistance against acidic outgassing; takes an SPI A-1 diamond mirror polish. 1,000,000+ Shots
H13 Tool Steel 50 – 54 HRC (Hardened) Hot-work steel with extreme thermal shock resistance and high compressive strength. Resists abrasive glass-fiber wear. 1,000,000+ Shots
P20 / 718H Steel 28 – 34 HRC (Pre-hardened) Versatile pre-hardened steel offering excellent machinability and uniform core hardness without post-heat treatment distortion. 250,000 – 500,000 Shots
NAK80 Steel 37 – 43 HRC (Pre-hardened) Pre-hardened age-hardened steel providing superior EDM spark finish capability, high polishability, and excellent weldability. 500,000+ Shots

Tool Steel Compatibility with Engineering Resins

Different polymer chemistries exert distinct physical demands on tool cavity surfaces during Moldeo por Inyección de Plástico:

Resin Chemistry Class Recommended Tool Steel Engineering Tooling Rationale
Optical Clear & Medical Resins (Polycarbonate (PC), PMMA(Acrylic), Biocompatible & Medical Grade Resin) S136 Stainless Steel (50 HRC) High-purity stainless structure takes a diamond mirror polish (Acabados Superficiales SPI A-1) without micro-pitting or rust inclusions.
Abrasive Fiber Compounds (Glass Fiber (GF), Carbon Fiber (CF)) H13 Tool Steel (52-54 HRC) High surface hardness prevents gate erosion and cavity pitting caused by high-velocity glass or carbon fiber shear.
Corrosive & Flame Retardant Resins (Flame Retardant (FR), PVC (Polyvinyl Chloride)) High-Chromium S136 / M340 Stainless Resists acidic outgassing generated when flame retardants or vinyl compounds break down at high melt processing temperatures.
Standard Commodity Resins (Polypropylene (PP), Polyethylene (PE), ABS, Polystyrene (PS)) P20 / 718H / NAK80 Steel Optimizes tooling cost and delivery lead times while providing reliable 250k–500k shot lives for High Volume Injection Molding.

Steel Heat-Treatment & Anti-Corrosion Matrix

Executing precision mold building demands strict metallurgical heat-treatment control and 5-axis CNC machining:

Vacuum Heat Treatment & Stress Relieving

Hardened steels (S136, H13) undergo computer-controlled vacuum heat treatment followed by triple tempering to achieve uniform 50–54 HRC core hardness. This eliminates internal residual stress and prevents tool warpage during high-speed CNC milling.

5-Axis CNC Precision Cavity Machining

Utilizing 25+ in-house 5-axis CNC machining centers, we cut hardened steel inserts to ±0.005 mm tolerances. This ensures micro-gap shut-offs at parting lines, preventing flash even when running low-viscosity super-polymers like Poliéter éter cetona (PEEK) y Sulfuro de polifenileno (PPS).

Mirror Polishing & Surface Texturing

S136 cavities are hand-polished by master mold makers using diamond paste compounds to achieve SPI A-1 mirror clarity, while P20 and 718 steels support acid etching for Mold-Tech textures or VDI 3400 EDM spark finishes.

Preventive Maintenance & Lifetime Tool Warranty

Molds running at Jucheng undergo scheduled Mold Repair & Maintenance, including ultrasonic cavity cleaning and core alignment checks, ensuring long-term repeatability on Production Injection Mold tools.

Material Properties

Density (Tool Steel) 7.75 - 7.85 g/cm³
Hardness Range (Fully Hardened S136 / H13) 48 - 54 HRC
Hardness Range (Pre-Hardened P20 / NAK80) 28 - 40 HRC
Tensile Strength (Hardened H13 / S136) 1,500 - 1,950 MPa
Yield Strength (Hardened H13 / S136) 1,200 - 1,600 MPa
Thermal Conductivity (23°C) 24 - 30 W/(m·K)
Coefficient of Thermal Expansion (20-100°C) 11.5 - 12.8 10⁻⁶/K
Compressive Strength (52 HRC) 1,800 - 2,200 MPa
Impact Toughness (Charpy V-Notch) 20 - 35 J
SPI Polishing Surface Capability SPI A-1 (Diamond Mirror Polish) -
Guaranteed Tool Shot Life (Class 101 Hardened) 1,000,000+ Cycles
Maximum Mold Plate Size 2500 x 1800 mm
Minimum Machining Tolerance +/- 0.005 mm