Mold Making Materials

Mold making materials at Fecision are matched to function, not defaulted to a single steel grade. Material choice is locked in alongside the mold design, not bolted on afterward. Steel grade, hardness target, and coating plan get decided at the DFM stage, before a single cavity is cut.

Explore Mold Steels

50,000+cycles with coated inserts

Tool Steel for Mold Components

Mold Making Materials: Tool Steel for Mold Components

The selection of mold steel is one of the most critical decisions in injection mold tooling. The steel grade directly influences tool life, part quality, production efficiency, maintenance frequency, and overall tooling cost. An incorrect choice can result in premature wear, dimensional drift, surface finish degradation, or catastrophic tool failure.

Wear ResistanceCorrosion ResistancePolishabilityToughness

Selection by operating niche

Different Types of Mold Steels

Every steel choice represents a trade-off between upfront cost and long-term production stability. The primary selection drivers are: Wear Resistance, Corrosion Resistance, Polishability, and Toughness. No single grade is universally superior; each occupies a distinct operational niche.

Pre-Hardened Mold Steels

Pre-hardened mold steels are delivered in a heat-treated condition, typically at 28-43 HRC. They require no post-machining heat treatment, which significantly reduces lead time, eliminates distortion risk from hardening, and lowers overall tooling cost. These grades are the workhorses of general-purpose injection molding.

P20 (1.2311 / 3Cr2Mo)

Classification: chromium-molybdenum plastic mold steel
Features: 28-32 HRC, good toughness, low corrosion resistance, excellent machinability
Equivalent Grades: DIN 1.2311, AISI P20, JIS PDS-3, GB 3Cr2Mo
Applicable Mold Types: General-purpose injection molds, prototype tooling, bridge tooling, medium complexity molds, mold bases
Tool Life: 100,000 - 500,000 shots (unfilled resins)
Compatible Resins: ABS, PP, PE, PS, PC/ABS (unfilled commodity resins)
Surface Finish: SPI B2-B1 (standard texture, semi-gloss); not suitable for mirror polish
Cost: ★☆☆☆☆ / Most economical mold steel
Key Limitation: Not suitable for glass-filled resins, PVC, or high-temperature materials; rapid gate wear with abrasive compounds

718H (1.2738 / P20+Ni)

Classification: nickel-modified plastic mold steel
Features: 33-38 HRC (some offers 38-42 HRC), excellent toughness, through-hardening, good machinability
Equivalent Grades: DIN 1.2738, ASSAB 718, GB 3Cr2NiMo
Applicable Mold Types: Large cross-section molds, high-volume production molds, precision plastic molds
Tool Life: 500,000 - 1000,000 shots (unfilled resins)
Compatible Resins: ABS, PP, PA, PC/ABS, general engineering resins (unfilled)
Surface Finish: SPI B1-A3 (standard to semi-gloss)
Cost: ★★☆☆☆
Key Limitation: Not recommended for glass-filled resins or highly abrasive materials without H13 inserts

NAK80

Classification: precipitation-hardening plastic mold steel
Features: 37-43 HRC, good toughness, medium-high wear resistance, good machinability
Equivalent Grades: Daiso NAK80, modified 1.2738
Applicable Mold Types: High-gloss product molds, devices requiring mirror finish
Tool Life: 1000,000+ shots (with proper maintenance)
Compatible Resins: PMMA, clear PC, ABS, PP, PS, general-purpose resins
Surface Finish: SPI A1-A2 (mirror polish, Ra ≤ 0.025 μm); excellent optical-grade finish capability
Cost: ★★★☆☆
Key Limitation: Not suitable for glass-filled or highly abrasive resins

S136H

Classification: martensitic stainless mold steel
Features: 37-43 HRC, medium wear resistance, good corrosion resistance, good machinability
Equivalent Grades: ASSAB S136H, DIN 1.2083H, AISI 420H-modified
Applicable Mold Types: Medium-precision molds, corrosive environment molds, food-contact tooling
Tool Life: 500,000 - 800,000 shots
Compatible Resins: PC, PMMA, PVC (short runs), ABS, medical-grade resins
Surface Finish: SPI A2-A3 (high gloss); polishable to ~12,000 grit
Cost: ★★★☆☆
Key Limitation: Lower polish ceiling than fully heat-treated S136

Through-Hardened Tool Steels

Through-hardened tool steels require heat treatment after rough machining to achieve their full working hardness (typically 48-54 HRC). They offer superior wear resistance, compressive strength, and thermal stability compared to pre-hardened grades, but require longer lead times and higher manufacturing costs due to the additional heat treatment process and harder machining conditions.

H13 (1.2344 / SKD61 / 4Cr5MoSiV1)

Classification: Chromium-molybdenum-vanadium hot work tool steel
Features: 48-52 HRC, high wear resistance, good toughness, moderate corrosion resistance, poor machinability
Equivalent Grades: DIN 1.2344, JIS SKD61, GB 4Cr5MoSiV1, AISI H13
Applicable Injection Mold Uses: High-volume production molds, hot runner systems, slides/lifters in abrasive applications, gate inserts, and core pins
Tool Life: 1000,000 - 2000,000+ shots
Compatible Resins: GF-PA66, GF-PP, GF-PBT, PPS, PEI, LCP, all glass-filled/mineral-filled resins, high temperature engineering plastics
Surface Finish: SPI A2-B1 (good polish but labor-intensive due to hardness); functional surfaces prioritized over cosmetic
Cost: ★★★☆☆
Key Limitation: Not suitable for PVC or corrosive resins (will pit within 50,000 shots from HCl attack)

8407 (Premium H13 / ESR)

Classification: Premium ESR hot work die steel (H13 class)
Features: 45-52 HRC, very high wear resistance, excellent toughness, good machinability
Equivalent Grades: ASSAB 8407, DIN 1.2344 (ESR), NADCA #207 premium
Applicable Injection Mold Uses: High-quality plastic molds, high-polish cavities, wear inserts, precision cores, and long-life production molds
Tool Life: 2000,000+ shots
Compatible Resins: All engineering resins including GF-filled, PEEK, PPS
Surface Finish: SPI A2-B1; ESR purity enables better polish than standard H13
Cost: ★★★☆☆

S136 (Stainless / ESR)

Classification: Martensitic stainless tool steel with ESR processing
Features: 58-62 HRC, very high wear resistance, very high compressive strength, moderate machinability (annealed)
Equivalent Grades: DIN 1.2379, JIS SKD11, AISI D2, GB Cr12Mo1V1
Applicable Mold Types: Wear plates, high-wear inserts, gate components for GF resins, cutting dies, precision gauges, cold shear blades
Tool Life: Extremely long in wear-dominated applications (varies by use case)
Compatible Resins: Highly filled resins (GF >30%), metal powder injection molding, abrasive compounds
Surface Finish: Functional surfaces; limited polishability due to large carbides
Cost: ★★★☆☆
Key Limitation: Very low toughness; brittleness restricts use to non-impact, non-thermal-cycling applications; poor corrosion resistance

Cold Work & Special-Purpose Steels

Cold work tool steels and special-purpose grades serve niche but critical roles in injection molding, typically as inserts, core pins, shut-off components, or for extreme wear/corrosion conditions where standard plastic mold steels are insufficient.

D2 / SKD11 (1.2379)

Classification: High-carbon, high-chromium cold work tool steel
Features: 48-54 HRC, medium-high wear resistance, excellent corrision resistance, good machinability
Equivalent Grades: ASSAB S136 / STAVAX ESR, DIN 1.2083 (ESR), AISI 420 ESR-modified
Applicable Mold Types: food-contact tooling, PVC molds, transparent part tooling, corrosive-resistance molds
Tool Life: 1000,000+ shots (optical/medical applications)
Compatible Resins: PC, PMMA, PVC, POM, FR-ABS, medical-grade resins, all corrosive resins
Surface Finish: SPI A1 (mirror polish, Ra ≤ 0.01 μm); optical-grade finish capability
Cost: ★★★☆☆
Key Limitation: Not optimal for highly abrasive glass-filled resins; higher cost limits use to technically-required applications

S7

Classification: Air-hardening shock-resisting tool steel
Features: 54-58 HRC (for cold work); 45-55 HRC (for hot work applications), moderate wear resistance, moderate compressive strength, good machinability in annealed condition
Equivalent Grades: T41907; no direct DIN/JIS equivalent
Applicable Mold Types: Fragile shut-offs, edge-loaded features, slides under impact, thin-wall sections, ejector pins, hot shear blades
Tool Life: Highly variable; toughness prevents catastrophic failure
Compatible Resins: All resin types; primarily selected for mechanical loading rather than resin compatibility
Surface Finish: Functional; moderate polishability
Cost: ★★★☆☆
Key Limitation: not suitable for high-abrasion applications without surface treatment

1.2316

Classification: Pre-hardened martensitic stainless mold steel with Mo addition
Features: 30-34 HRC, moderate wear resistance, excellent corrosion resistance, good machinability
Equivalent Grades: X38CrMo16
Applicable Mold Types: PVC molds, corrosive resin molds, food containers, humid processing environments, medical device molds
Tool Life: 500,000+ shots for corrosive applications
Compatible Resins: PVC, fluoropolymers, flame-retardant grades, all acidic off-gassing resins
Surface Finish: Good; suitable for high-quality surface finishes in corrosive environments
Cost: ★★★☆☆
Key Limitation: require nitriding for high-wear areas

DC53

Classification: High-performance cold work die steel (improved SKD11/D2)
Features: 60-62 HRC, very high wear resistance, extremely high compressive strength, moderate machinability
Origin: Japanese grade (Daido Steel); improved version of SKD11
Applicable Mold Types: Ultra-wear-resistant molds, high GF-content inserts, thin-wall high-pressure molds, precision blanking dies
Tool Life: Extremely long in high-wear applications
Compatible Resins: High glass-fiber content (>30%) resins, metal-powder injection molding, carbon- fiber filled materials
Surface Finish: Functional; hardness limits cosmetic polish capability
Cost: ★★★☆☆
Key Limitation: Very difficult to machine and polish; strictly for localized wear inserts, not full cavities

Grade changes by component

Mold Steel by Component

Different parts of a mold see different loads, so the steel grade changes by component rather than running one grade throughout the tool.

Mold base

S50C

Structural frame and load-bearing plates

Cavity

SKD61 or S136

Wear-facing surface that defines part geometry

Core

S136

Wear-facing surface opposite the cavity

High-wear inserts

Cr12MoV

Wear-critical zones, typically paired with DLC coating

Rapid tooling (validation)

Aluminum 7075 / P20 / NAK80

Short-run tooling for 100-5,000 piece validation

Long-life mold protection

Surface Treatment: Turning Tool Steel Into a Long-Life Mold

Steel selection is half the equation. Surface treatment is the other half, and it's where most of the cycle-life gain actually comes from. Fecision's standard path takes a mold from quench-and-temper up through a DLC coating, with nitriding and hard chrome plating available where a project calls for a different wear or corrosion profile.

Base hardness (post quench-temper)HRC 58-62

Coating typeDLC (diamond-like carbon)

Coating hardness≥2200 HV

Coating thickness6-8 μm

Friction coefficient (post-coating)0.1-0.2

Working surface roughnessRa≤0.2 μm

Chemical nickel (connector inserts)5-10 μm

Gold plating (connector inserts)1-30 μm, as required

Process sequence: quench and temper the base steel to HRC 58-62, ultrasonic clean to remove oil and debris, polish the working surface to Ra≤0.2 μm, activate the surface with a plasma treatment, deposit the DLC layer by PVD or CVD, then verify thickness, Vickers hardness, and adhesion with a cross-hatch test before the mold goes back into production.

Choose by wear, geometry and volume

Get a Material and Coating Recommendation

Choosing mold making materials is really a wear-versus-cost decision made early: S50C carries the structural load, SKD61 or S136 hold the working geometry, and Cr12MoV plus DLC coating goes wherever a mold sees the most cycles. Every material decision happens at the DFM stage, whether the mold is headed for in-house production, standalone sale, or a rapid-tooling validation run first.

Precision behind the grade

Machining Capability Behind the Material Choice

Cutting and finishing these steels to the tolerances a production mold needs takes dedicated equipment, not general-purpose machining.

CNC machining centers±0.01 mm

EDM (spark erosion)±0.01 mm

Wire EDM, slow-speed±0.002 mm

Wire EDM, fast-speed—

Mills / grinders—

Coating thickness gauge±0.1 μm

Vickers hardness testerHV0.1–HV100

Match investment to validation stage

Production Mold Steel vs. Rapid Tooling Material

Production Mold Steel

S50C / SKD61 / S136 / Cr12MoV

Production mold steel (S50C / SKD61 / S136 / Cr12MoV): built for 50,000+ cycle life, 15-20 day mold build, standard for volume runs of 50,000+ pieces (LSR) or 100,000+ (precision connector parts).

Rapid Tooling

Aluminum 7075

Rapid tooling, aluminum 7075: 7-10 day build, suited to early process and material validation before cutting a production mold.

Rapid Tooling

P20 / NAK80 / S136

Rapid tooling, pre-hardened steel (P20 / NAK80 / S136): 12-15 day build, closer to production fidelity for a 100-5,000 piece validation run.

Mold material questions

Frequently Asked Questions

What steel goes into the mold base versus the cavity?

The mold base uses S50C, a structural steel suited to the frame and load-bearing plates. The cavity and core use SKD61 or S136, hardened tool steels that hold tight geometry under repeated injection pressure.

How much longer does a DLC-coated mold last than an untreated one?

Quench-and-temper alone typically holds up to about 15,000 cycles. Adding a DLC coating — ≥2200 HV hardness, 6-8 μm thick — extended that to 50,000+ cycles on a documented Cr12MoV insert project.

Can the mold be purchased without the molding service?

Yes. Standalone mold sales include full DFM support, design drawings, and trial-run guidance, so the mold can run in-house or at your own factory. Fecision also offers mold-plus-molding as a bundled service — the material and design specs stay the same either way.

What surface finish can the mold cavity hold?

Working surfaces polish to Ra≤0.2 μm before plasma activation and DLC deposition. That finish is tight enough to keep surface defects from transferring onto molded parts, particularly on cosmetic or sealing surfaces where flash and drag marks are not acceptable.

Build the Material Plan Before the Mold

Review steel grade, hardness target, surface treatment and production volume with our tooling team.

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