How To Choose The Right Material for plastic injection mould

There are hundreds of metal alloys available for plastic injection mould. Which one is best for your next project depends on a number of factors, including price, workability, corrosion resistance, strength, weight and cosmetic appearance. To help you choose, here’s a closer look at the ones we use every day and what benefits they may have for your next project.


Daido High Performance, High Precision Plastic Mould Steel

Delivered Hardness:
Pre-hardened to HB344-400

Chemical Content(%):(For reference only)


This is the most common general purpose grade. The main alloying ABS material with Polish or texture surface , and mold life within 300k, PS and PP, ABS/PC and so on, this steel hardness will be 42HRC, and cost is not very expensive for injection mould insert material . and its wide availability means that it’s economical.

NAK80 made in Japan DaDao


  • Solution-treated and Age-hardened to 37-43 HRC 
    Can be processed in delivered condition without heat treatment
  • Ni-Al-Cu Age-hardening steel 
    Good Machinability 
    Can be easily ground after EDM processing 
    Good welding performance 
    Good dimensional stability 
    Uniform surface and core hardness
  • Special Melting Process 
    Can be polished up to #8000 mirror finishing 
    Excellent photo etching and EDM properties

Major Application:
High performance, high precision plastic mould
Transparent or mirror finishing
High-requirement EDM surface finishing

Can be machining in delivered condition without extra heat treatment process

Typical Polishing Procedures:

  • Grinding (#220 -> #320 -> #400)
  • Emery Paper Polsihing(#320 -> #400 -> #600 -> #800 -> #1000)
  • Diamond Paste finishing(#1200 -> #1800 -> #3000 -> #8000 -> #14000)

S136 /S136H

S136 is a higher grade of tool steel, alloyed mainly with PC. It’s one of the strongest alloys, with excellent strength-to-weight characteristics.

ASSAB Premium grade stainless tool steel

Delivered Hardness:
S136H pre-hardened to HB290-330
S136 annealed to HB200

Chemical Content(%):(For reference only)


Comparable Standard
AISI 420 ESR Mod or WNr. 1.2083ESR or SUS 420J2 ESR


  • Good corrosion resistance
  • Excellent polishability
  • Good wear resistance
  • Good machinability
  • Good dimensional stability during heat treatment

Major Application:

  • Corrosion/staining resistance : moulding of corrosive plastics, e.g. PVC, acetates, and for moulds subjected to humid working/storage conditions
  • Wear resistance : Moulding abrasive/ filled materials, including injection moulded thermosetting grades. S136 is recommended for moulds with long production runs, e,g, disposable cutlery and containers
  • High surface finish : production of optical parts, e.g. camera and sunglass lenses. Moulding of medical components, e.g. syringes and analysis vials

Hi-end plastic injection mould, made treat-men the hardness will be 50HRC.


ASSAB high performance hot work steel,

Delivered Hardness:
Annealed to HB185

Chemical Content(%):(For reference only)


Comparable Standard:
AISI H13, WNr. 1.2344, SKD61

Brass takes a high polish that looks much like gold. This is the reason it’s often found in cosmetic applications. Brass is electrically conductive but non-magnetic, and can be easily recycled.

Characteristics: plastic mould steel

  • High level of resistance to thermal shock and thermal fatigue
  • Good high-temperature strength
  • Excellent toughness and ductility in all directions
  • Good machinability and polishability
  • Excellent through-hardening properties
  • Good dimensional stability during hardening


SSAB High performance plastic mould steel

Delivered Hardness
pre-hardened to HB330-380


  • No hardening risks
  • No hardening costs
  • Time saving
  • Lower tool costs
  • Modifications easily carried out
  • Can be subsequently nitrided to increase surface wear resistance and locally flame hardened to reduce surface damage
  • Good polishing and photo-etching properties
  • Good machinability
  • High purity and good homogeneity
  • Uniform hardness

Chemical Content(%):(For reference only)


Comparable Standard:
WNr.1.2738Stainless Steel 303