Mold Building Materials
In mold manufacturing, selecting the right materials isn’t just a technical detail—it’s a strategic business decision. Components like high-grade mold steel and specialized alloys are critical to ensuring precision, durability, and long-term performance. Premium materials maintain structural integrity under demanding conditions, directly boosting the efficiency of injection molding operations. This translates to consistently flawless plastic parts, reduced downtime, and faster cycle times—key drivers for maximizing ROI and customer satisfaction. When you invest in top-tier materials, you’re not just building molds; you’re securing a competitive edge in quality and reliability.
Overview of Different Mold Building Materials
| Material Type | Common Grades | Characteristics | Physical Properties | Typical Applications |
|---|---|---|---|---|
| Tool Steel | P20 | Pre-hardened, good polishability | Density: ~7.85 g/cm³; Elastic Modulus: ~200 GPa; Thermal Conductivity: ~29 W/m·K; Machinability: ~60% | General-purpose molds, plastic injection molds, and mold bases |
| Tool Steel | S7 | Shock-resistant | Density: ~7.83 g/cm³; Elastic Modulus: ~207 GPa; Thermal Conductivity: ~28.5 W/m·K; Machinability: ~72% | Tools requiring high impact resistance such as shock-resistant dies, punches, and shear blades |
| Tool Steel | A2 | Air-hardening, good dimensional stability, moderate wear resistance | Density: ~7.86 g/cm³; Elastic Modulus: ~190 GPa; Thermal Conductivity: ~26 W/m·K; Machinability: ~60% | Cold-work tooling including blanking dies, forming dies, and punches requiring good wear resistance and toughness |
| Tool Steel | S5 | High impact toughness, oil-hardening, good wear resistance | Density: ~7.85 g/cm³; Elastic Modulus: ~210 GPa; Thermal Conductivity: ~24 W/m·K; Machinability: ~55% | Medium-impact tooling like chisels, punches, and light forging dies |
| Tool Steel | O1 | Oil-hardening, excellent dimensional stability, good machinability | Density: ~7.83 g/cm³; Elastic Modulus: ~214 GPa; Thermal Conductivity: ~33.4 W/m·K; Machinability: ~85-90% | General-purpose tool steel for low to medium production tooling such as cutting tools, punches, and dies |
| Tool Steel | M42 | High-speed steel, excellent hot hardness, wear resistance | Density: ~8.12 g/cm³; Elastic Modulus: ~210 GPa; Thermal Conductivity: ~24 W/m·K; Machinability: ~50% | High-speed cutting tools including taps, drills, milling cutters, and reamers with excellent wear resistance |
| Tool Steel | A6 | Air-hardening, minimal distortion, intermediate wear resistance | Density: ~7.85 g/cm³; Elastic Modulus: ~200 GPa; Thermal Conductivity: ~24 W/m·K; Machinability: ~60% | Cold-work tooling with a balance of toughness and wear resistance for blanking, forming, and piercing dies |
| Tool Steel | A7 | Air-hardening, high hardness, moderate toughness | Density: ~7.85 g/cm³; Elastic Modulus: ~200 GPa; Thermal Conductivity: ~25 W/m·K; Machinability: ~65% | Cold-work tooling requiring high toughness and wear resistance |
| Tool Steel | A10 GraphAir | Self-lubricating, good wear resistance, minimal distortion | Density: ~7.85 g/cm³; Elastic Modulus: ~200 GPa; Thermal Conductivity: ~25 W/m·K; Machinability: ~60% | Cold-work applications requiring improved machinability and wear resistance such as dies and punches |
| Tool Steel | O6 | Oil-hardening, good wear resistance, minimal distortion | Density: ~7.85 g/cm³; Elastic Modulus: ~200 GPa; Thermal Conductivity: ~24 W/m·K; Machinability: ~60% | General-purpose tool steel for cutting tools, punches, and dies with good wear resistance and toughness |
| Tool Steel | D2 | High wear resistance | Density: ~7.70 g/cm³; Elastic Modulus: ~210 GPa; Thermal Conductivity: ~20 W/m·K; Machinability: ~50% | High wear resistance cold-work tooling including stamping dies, cutting tools, and shear blades |
| Tool Steel | D3 | High-carbon, high-chromium, excellent wear resistance | Density: ~7.80 g/cm³; Elastic Modulus: ~210 GPa; Thermal Conductivity: ~20 W/m·K; Machinability: ~40% | Cold-work tooling with excellent wear resistance for heavy-duty stamping and forming dies |
| Tool Steel | D7 | High wear resistance, high hardness, moderate toughness | Density: ~7.85 g/cm³; Elastic Modulus: ~200 GPa; Thermal Conductivity: ~25 W/m·K; Machinability: ~50% | Cold-work dies and tooling requiring wear resistance and toughness, including blanking and forming dies |
| Tool Steel | L6 | Oil-hardening, good toughness, high impact resistance | Density: ~7.84 g/cm³; Elastic Modulus: ~200 GPa; Thermal Conductivity: ~36 W/m·K; Machinability: ~60% | High toughness cold-work tools including shear blades, punches, and forging dies |
| Tool Steel | LescoWear | Air-hardening, good toughness and wear resistance | Density: ~7.85 g/cm³; Elastic Modulus: ~200 GPa; Thermal Conductivity: ~25 W/m·K; Machinability: ~60% | Heavy-duty cold-work tooling applications requiring exceptional wear resistance and toughness such as dies and punches |
| Tool Steel | CPM 1V | Powder metallurgy steel offering exceptional impact toughness, solid hot hardness, and good wear performance | Density: ~7.85 g/cm³; Specific Gravity: 7.80; Elastic Modulus: 207 GPa; Machinability: ~65–70% of 1% carbon steel | High-stress tooling such as blanking and sizing dies, shear blades, hot/cold forging punches, and gear rolling dies |
| Tool Steel | CPM 3V | Powder metallurgy, excellent toughness, good wear resistance | Density: ~7.80 g/cm³; Elastic Modulus: ~210 GPa; Thermal Conductivity: ~25 W/m·K; Machinability: ~50% | High-impact mold components such as core pins, ejector pins, and inserts requiring superior toughness and wear resistance |
| Tool Steel | CPM 4V | Powder metallurgy, high wear resistance, good toughness | Density: ~7.80 g/cm³; Elastic Modulus: ~210 GPa; Thermal Conductivity: ~25 W/m·K; Machinability: ~50% | Mold parts subjected to heavy wear and moderate impact, including die inserts, cores, and cold work tooling |
| Tool Steel | CPM 9V | High-vanadium powder steel delivering excellent wear resistance and notable toughness, with thermal fatigue resistance for warm/hot work tools | Density: ~7.42 g/cm³; Specific Gravity: 7.41; Elastic Modulus: 221 GPa; Machinability: ~35–40% of 1% carbon steel | Injection molding feed screws, non-return valves, shear blades, and forging dies |
| Tool Steel | CPM 10V | Premium powder steel known for extreme wear resistance and good toughness due to high vanadium content and refined microstructure | Density: ~7.42 g/cm³; Specific Gravity: 7.41; Elastic Modulus: 221 GPa; Machinability: ~35–40% of 1% carbon steel | Tooling needing exceptional wear life, outperforms D2 and D7 in demanding applications |
| Tool Steel | CPM 15V | A cold work powder metallurgy steel with superior wear resistance due to increased vanadium carbides, delivering longer tool life and an alternative to carbide in complex tooling | Density: ~7.25 g/cm³; Elastic Modulus: 235 GPa; Machinability: Data not specified | Cold work applications requiring extreme durability and where carbide tools risk fracture or are hard to produce |
| Tool Steel | 718H (P20+Ni) | Pre-hardened, high polishability, toughness | Density: ~7.80 g/cm³; Elastic Modulus: ~205 GPa; Thermal Conductivity: ~30 W/m·K; Machinability: ~70% | High-precision automotive/optical plastic molds |
| Tool Steel | 1.2311 (DIN) | Pre-hardened, corrosion-resistant | Density: ~7.85 g/cm³; Elastic Modulus: ~210 GPa; Thermal Conductivity: ~29 W/m·K; Machinability: ~75% | Transparent plastic molds, electronics |
| Tool Steel | QRO 90 SUPREME | High thermal fatigue resistance, hot hardness | Density: ~7.80 g/cm³; Elastic Modulus: ~210 GPa; Thermal Conductivity: ~35 W/m·K; Machinability: ~60% | Die casting, extrusion of nonferrous metals |
| Tool Steel | 440C | High hardness, wear/corrosion resistance | Density: ~7.62 g/cm³; Elastic Modulus: ~200 GPa; Thermal Conductivity: ~24.2 W/m·K; Machinability: ~35% | Precision cutting tools, bearings |
| Tool Steel | Premium H13 | Premium-grade H13 hot work die steel with excellent toughness, thermal fatigue resistance, and polishability; produced via AOD and VAR for superior cleanliness and microstructure | Density: ~7.80 g/cm³; Hardness: Up to ~52 HRC (heat treated); Ac1: 1544°F / 840°C; Ac3: 1634°F / 890°C; Machinability: Moderate | Shot sleeves, extrusion dies, plastic mold cavities, hot forging dies, die casting inserts. |
| Copper Alloy | BeCu-20 (C17500) | High thermal conductivity, corrosion-resistant | Density: ~8.25 g/cm³; Elastic Modulus: ~130 GPa; Thermal Conductivity: ~210 W/m·K; Machinability: ~85% | Rapid-cooling molds, high-gloss surfaces |
| Aluminum Alloy | Prodax-7 (Al-Zn) | Lightweight, rapid prototyping | Density: ~2.70 g/cm³; Elastic Modulus: ~70 GPa; Thermal Conductivity: ~150 W/m·K; Machinability: ~90% | Prototype molds, low-pressure injection |
| Aluminum Alloy | A7075-T6 | High strength, excellent EDM performance | Density: ~2.81 g/cm³; Elastic Modulus: ~72 GPa; Thermal Conductivity: ~173 W/m·K; Machinability: ~95% | Prototyping, small-batch production |
| Aluminum Alloy | 6061 | Good mechanical properties, corrosion resistance, good weldability | Density: ~2.70 g/cm³; Elastic Modulus: ~69 GPa; Thermal Conductivity: ~167 W/m·K; Machinability: ~85% | Structural components, general-purpose molds, automotive parts |
| Beryllium Copper | Alloy 25 | High thermal conductivity, strength | Density: ~8.26 g/cm³; Elastic Modulus: ~131 GPa; Thermal Conductivity: ~105 W/m·K; Machinability: ~20% | Mold components exposed to high stress, including cores and inserts requiring toughness |
| Beryllium Copper | H13 | Hot work steel, high toughness | Density: ~7.80 g/cm³; Elastic Modulus: ~207 GPa; Thermal Conductivity: ~24 W/m·K; Machinability: ~65% | High-volume injection molds, hot-work tooling including die casting dies, extrusion dies, and forging dies requiring excellent toughness and heat resistance |
| Beryllium Copper | 4340 | High toughness, high strength | Density: ~7.85 g/cm³; Elastic Modulus: ~200 GPa; Thermal Conductivity: ~44 W/m·K; Machinability: ~50% | Heavy-duty mold bases, die shoes, and parts requiring high fatigue resistance and strength |
| Beryllium Copper | 1045 | Higher strength, medium carbon steel | Density: ~7.85 g/cm³; Elastic Modulus: ~200 GPa; Thermal Conductivity: ~49 W/m·K; Machinability: ~55% | Standard mold base material and general tooling with good machinability |
| Carbon Steel | 1018 | Good machinability, low cost | Density: ~7.87 g/cm³; Elastic Modulus: ~200 GPa; Thermal Conductivity: ~52 W/m·K; Machinability: ~70% | Mold support structures and fixtures with good weldability and ease of machining |
| Chromium Steel | 52100 | High-carbon, high-chromium steel known for excellent wear resistance and high hardness | Density: ~7.81 g/cm³; Hardness: up to 66 HRC (after heat treatment); Tensile Strength: ~760–880 MPa; Machinability: Low | Bearings, precision tools, wear-resistant components |
| Stainless Steel | 420 SS | Corrosion-resistant, moderate hardness | Density: ~7.70 g/cm³; Elastic Modulus: ~200 GPa; Thermal Conductivity: ~25 W/m·K; Machinability: ~50% | PVC/corrosive plastic molds |
| High-Speed Steel | M2 | Tungsten-molybdenum high-speed steel with excellent wear resistance and red hardness | Density: ~8.16 g/cm³; Hardness: ~62–67 HRC (after heat treatment); Tensile Strength: ~900–1000 MPa; Machinability: Low | Cutting tools, drills, taps, end mills |
| High-Speed Steel | 17-4PH | Precipitation-hardening stainless steel with high strength and corrosion resistance | Density: ~7.75 g/cm³; Hardness: ~28–44 HRC (depending on heat treatment); Tensile Strength: ~1100–1310 MPa; Machinability: Moderate | Aerospace components, nuclear reactor parts, surgical instruments |
| High-Speed Steel | CPM M4 / PM M4 | PM high-speed steel with exceptional wear resistance, impact toughness, and bend strength due to fine carbides and powder metallurgy microstructure; superior to conventional M1, M2, M7 steels | Density: 0.286 lb/in³ (7916 kg/m³); Specific Gravity: 7.92; Modulus of Elasticity: 31 x 10⁶ psi (214 GPa); Machinability: 40-45% of 1% carbon steel | Cold work tooling, cutting tools with longer life, wear-resistant applications |
| High-Speed Steel | CPM T15 / PM T15 | Cobalt-bearing super high-speed steel with hardness up to 67 HRC, very high wear resistance from vanadium carbides, excellent red hardness, easier grinding and double impact toughness vs traditional T15 | Density: 0.296 lb/in³ (8193 kg/m³); Specific Gravity: 8.19; Modulus of Elasticity: 30 x 10⁶ psi (207 GPa); Machinability: 35-40% of 1% carbon steel | High-performance broaches, form tools, milling cutters, end mills, taps, reamers; cutting strong or abrasive materials at high temps |
| High-Speed Steel | CPM Rex 76 / PM M48 | High-performance super high speed steel with superior red hardness (up to 70 HRC), wear resistance comparable to T15, and excellent toughness from powder metallurgy structure | Density: 0.298 lb/in³ (8256 kg/m³); Specific Gravity: 8.26; Modulus of Elasticity: 30 x 10⁶ psi (214 GPa); Machinability: 10-15% of 1% carbon steel | Form tools, broaches, milling cutters, hobs, and special cutting tools requiring high hot hardness |
| Alloy Steel | LSS™ 4140 and 4142HT | Versatile alloy steels; LSS 4140 annealed ≤217 HBW hardness; LSS 4142HT prehardened 28–32 HRC; thickness >3 in may have lower core hardness | Density: 0.283 lb/in³ (7833 kg/m³); Specific Gravity: 7.83; Modulus of Elasticity: 29 x 10⁶ psi (200 GPa) | Common uses span bending and brake dies, fixture supports, die holders, gear components, flange assemblies, collets, spindles, arbors, axles, clutch mechanisms, forming rolls, manual tools like wrenches, and a wide array of machine tool elements. |
| Zinc Alloy | ZA-12 | High strength and hardness, good wear resistance, suitable for thin-walled castings | Density: ~5.0 g/cm³; Elastic Modulus: ~96 GPa; Thermal Conductivity: ~113 W/m·K; Machinability: Good | Die cast parts, housings, brackets, small mechanical components |
| Pre-Hardened Steel | 4140 (pre-hardened) | Pre-hardened to 28–32 HRC; good toughness and machinability; suitable for tooling | Density: ~7.85 g/cm³; Hardness: ~28–32 HRC; Tensile Strength: ~1000 MPa; Machinability: Moderate | Molds, die holders, tool components, jigs and fixtures |
Mold Making Materials at KingStar Mold
High-Quality Materials for Superior Mold Production
At KingStar Mold, we offer a wide range of top-quality materials for mold building, ensuring durability, precision, and efficiency in every project. Our materials, including tool steels, aluminum alloys, and copper-based alloys, are selected for their strength, heat resistance, and ability to withstand the demands of high-volume production. Each material is chosen based on its specific properties to meet the needs of various industries, from automotive to medical.
We focus on delivering the best solutions for your mold production needs. With our expertise and material selection, we ensure molds that perform optimally, offering long-lasting results and minimal downtime in production.
Frequently Asked Questions
One of KingStar Mold’s key strengths is our expert material selection consultation. Our experienced engineers work closely with clients from the design stage, evaluating part geometry, production volume, wear, and thermal needs. We recommend the best materials to balance cost, durability, and performance, helping avoid costly mistakes, shorten lead times, and extend mold life. This tailored approach ensures efficient, high-quality manufacturing for every project.
Copper-based alloys, especially beryllium copper, are prized in mold making for their exceptional thermal conductivity, which is about four times higher than most tool steels. This property allows molds made with copper alloys to cool parts more rapidly and evenly, improving cycle times and reducing defects such as warping or sink marks. Furthermore, copper alloys provide good corrosion resistance and moderate strength, making them ideal for mold components like cores, inserts, or cooling channels.
KingStar Mold strategically integrates copper-based alloys in mold areas where enhanced heat dissipation is critical, thereby boosting production efficiency and part quality without compromising mold integrity.
Yes, KingStar Mold customizes material selection to meet the specific needs of various industries such as automotive, medical, electronics, and consumer goods. Each industry has unique demands for precision, surface finish, and compliance. For instance, medical molds often require stainless steels with corrosion resistance to meet hygiene standards, while automotive molds demand materials that handle high thermal loads and wear. Our engineering team works closely with clients to understand these requirements and recommend materials that optimize mold life, reduce maintenance, and deliver consistent part quality. This tailored approach ensures the mold supports the final product’s performance and regulatory needs.
Durability is critical for molds to maintain precision and reduce production downtime. KingStar Mold ensures durability by selecting materials with proven mechanical strength and resistance to wear and heat. For example, tool steels like H13 have excellent toughness and resistance to thermal fatigue, making them ideal for high-volume production runs. We also employ advanced heat treatment processes to optimize the hardness and longevity of steel molds. In addition, our quality control protocols include material certification and rigorous inspection, ensuring every mold meets strict standards before delivery. This combination of material quality and expert processing results in molds that withstand repeated cycles without degradation.
