Plastic Mould Steels

Tool steels are used for working, cutting, and forming metal components, moulding plastics, and casting dies for metals with lower melting points than steel. Accordingly, tool steels need high hardness and strength combined with good toughness over a broad temperature range.

Plastic mould steels

Tools for processing plastics are mainly stressed by pressure and wear. According to the type of plastic, corrosive conditions can prevail in addition to stresses. The type of plastic and processing method define the key requirements in addition to those generally valid to hot-work steels:

Economic machinability or cold-hobbing ability
Smallest possible distortion upon heat treatment
Good polishing behavior
High compressive strength
High wear resistance
Sufficient corrosion resistance

AISI-SAE tool steel grades
Defining property	AISI-SAE grade	Significant characteristics
Water-quenched	W	Molybdenum alloying optional
Cold-working	O	Oil-hardening, O6-0.3% molybdenum, cold-work steel used for gauges, cutting tools, woodworking tools and knives
	A	Air-hardening, low distortion during heat treatment, balance of wear resistance and toughness, all molybdenum alloyed – 0.15-1.8%
	D	High carbon, high chromium, 0.9% molybdenum, very high wear resistance but not as tough as lower alloyed steels
Hot-working	H	H1-H19 – chromium base H20-H39 – tungsten base H40-H59 – molybdenum base
Plastic moulding	P	Low segregation: reduced alloying of silicon, manganese and chromium Through hardenability: increased molybdenum and vanadium
High-speed	T	Tungsten base (today mostly replaced by M22)
High-speed	M	Molybdenum base
Shock resisting	S	Chromium-tungsten, silicon-molybdenum, silicon-manganese alloying, very high impact toughness and relatively low abrasion resistance
Special purpose	L	Low alloy, high toughness
Special purpose	F	Carbon-tungsten alloying, substantially more wear resistant than W-type tool steel