Top 10 Tool Steel Grades Used in Plastic Mold Manufacturing

Top 10 Tool Steel Grades Used in Plastic Mold Manufacturing

Tool Steel Grades Used in Plastic Mold Manufacturing: Top 10 Proven Options

 Top 10 Tool Steel Grades Used in Plastic Mold Manufacturing
 Explore the top 10 tool steel grades used in plastic mold manufacturing, their properties, applications, advantages, and how to choose the right mold steel for your project.

Introduction

Plastic mold manufacturing is a precision-driven industry where the quality of mold steel directly impacts production efficiency, product quality, mold life, and maintenance costs. Selecting the right tool steel grade is essential for achieving superior performance, dimensional accuracy, and long-term durability.

Different plastic molding applications require specific steel properties such as hardness, wear resistance, corrosion resistance, machinability, polishability, and toughness. In this article, we explore the top 10 tool steel grades widely used in plastic mold manufacturing and their key benefits.

1. P20 Tool Steel

P20 is one of the most commonly used plastic mold steels worldwide. It is supplied in a pre-hardened condition, making it easy to machine and suitable for medium-volume production molds.

Key Properties:

  • Hardness: 28-32 HRC
  • Excellent machinability
  • Good polishability
  • Uniform hardness distribution

Applications:

  • Injection molds
  • Automotive components
  • Consumer products
  • Medium production runs

Benefits:

  • Reduced machining time
  • Cost-effective
  • Good dimensional stability

2. P20+Ni (P20 Nickel Alloy Steel)

P20+Ni contains additional nickel, improving toughness and hardness uniformity, especially for larger molds.

Key Properties:

  • Enhanced toughness
  • Better polishability
  • Improved core strength

Applications:

  • Large plastic molds
  • Automotive bumpers
  • Appliance housings

Benefits:

  • Longer mold life
  • Superior surface finish
  • Improved resistance to cracking

3. 718 Mold Steel

718 steel is an upgraded version of P20 with better hardness and polishing characteristics.

Key Properties:

  • Hardness: 33-38 HRC
  • High polishability
  • Excellent machinability

Applications:

  • Transparent plastic products
  • Cosmetic packaging molds
  • High-quality consumer goods

Benefits:

  • Better surface finish
  • Improved wear resistance
  • Increased production life

4. 718H Tool Steel

718H is supplied in a hardened condition and is ideal for high-volume plastic molding applications.

Key Properties:

  • Hardness: 34-40 HRC
  • Excellent toughness
  • High wear resistance

Applications:

  • Automotive molds
  • Electronic component molds
  • Large production molds

Benefits:

  • Reduced maintenance
  • Longer service life
  • Enhanced productivity

5. NAK80 Steel

NAK80 is a premium pre-hardened mold steel known for exceptional mirror polishing and EDM performance.

Key Properties:

  • Hardness: 37-43 HRC
  • Superior polishability
  • Excellent machinability

Applications:

  • Optical lenses
  • Cosmetic containers
  • Transparent plastic products

Benefits:

  • Mirror-like surface finish
  • Reduced machining costs
  • High precision molding

6. H13 Tool Steel

H13 is a hot-work tool steel offering excellent toughness and thermal fatigue resistance.

Key Properties:

  • High hardness
  • Excellent heat resistance
  • Good wear resistance

Applications:

  • High-temperature molding
  • Die casting molds
  • Compression molds

Benefits:

  • Long service life
  • Excellent thermal stability
  • Reduced risk of cracking

7. S136 Mold Steel

S136 is a stainless mold steel designed for applications requiring corrosion resistance and superior polishing performance.

Key Properties:

  • Excellent corrosion resistance
  • High hardness after heat treatment
  • Outstanding polishability

Applications:

  • Medical components
  • Food packaging molds
  • Optical products

Benefits:

  • Rust resistance
  • Superior surface quality
  • Low maintenance

8. S136H Steel

S136H is the pre-hardened version of S136, offering similar corrosion-resistant properties with improved processing convenience.

Key Properties:

  • Pre-hardened condition
  • Excellent corrosion resistance
  • Good wear resistance

Applications:

  • PVC molds
  • Medical equipment parts
  • Transparent plastic products

Benefits:

  • Faster mold production
  • Extended mold life
  • Reduced maintenance costs

10 Proven Tool Steel Grades Used in Plastic Mold Manufacturing

Selecting the right tool steel is essential for improving plastic mold performance, durability, and production efficiency. Proven grades such as P20, P20+Ni, 718, 718H, NAK80, H13, S136, S136H, D2, and 420 Stainless Steel are widely used because they offer the ideal balance of hardness, toughness, wear resistance, corrosion resistance, and polishability. These steels help manufacturers achieve better surface finishes, longer mold life, reduced maintenance, and consistent product quality. Whether for high-volume injection molding, transparent plastic products, automotive components, or medical applications, choosing the right tool steel grade can significantly enhance mold performance and overall manufacturing productivity.

 

9. D2 Tool Steel

D2 is a high-carbon, high-chromium cold-work steel known for exceptional wear resistance.

Key Properties:

  • High hardness
  • Excellent wear resistance
  • Good dimensional stability

Applications:

  • Abrasive plastic molding
  • High-production molds
  • Precision components

Benefits:

  • Outstanding durability
  • Reduced wear
  • Longer production cycles

10. 420 Stainless Tool Steel

420 stainless steel is widely used where corrosion resistance and high polishability are required.

Key Properties:

  • Excellent corrosion resistance
  • Good hardness
  • Mirror finish capability

Applications:

  • Medical molds
  • Food-grade products
  • Optical components

Benefits:

  • Rust-free performance
  • Superior finish quality
  • Extended mold lifespan

How to Choose the Right Tool Steel for Plastic Molds

When selecting mold steel, consider the following factors:

Production Volume

  • Low to medium volume: P20, 718
  • High volume: H13, S136, D2

Surface Finish Requirements

  • Mirror finish: NAK80, S136, 420 Stainless
  • Standard finish: P20, 718H

Corrosion Resistance

  • PVC processing: S136, S136H, 420 Stainless
  • Standard plastics: P20, H13

Wear Resistance

  • Abrasive materials: D2, H13
  • General applications: P20, 718

Budget Considerations

  • Economical: P20, 718
  • Premium performance: NAK80, S136, H13