Injection Mold Steel Grades: Complete Comparison Chart

Selecting the right steel grade for your injection mold is one of the most important decisions in tooling. This guide provides a complete comparison of common mold steel grades, their properties, and recommended applications.

Common Mold Steel Grades Overview

Grade	Hardness (HRC)	Mold Life	Polishing	Cost
P20	28-32	500K-1M	Good	$
718H	32-38	1M-2M	Excellent	$$
H13	44-52	2M-5M	Fair	$$$
NAK80	37-43	1M-3M	Excellent (mirror)	$$$
S136	48-52	2M-4M	Excellent	$$$$

P20 Steel

P20 is the most commonly used mold steel for general-purpose injection molding. It comes pre-hardened at 28-32 HRC and offers good machinability and polishability at a reasonable cost. Best for commodity plastic parts where surface finish requirements are moderate.

718H Steel

718H is an improved version of P20 with higher hardness and better polishability. It is ideal for automotive interior parts, appliance housings, and any application requiring a high-gloss surface finish. It offers longer mold life than P20 at a moderate price premium.

H13 Steel

H13 is a hot-work tool steel designed for high-temperature applications. It excels in molding engineering plastics like nylon, PC, and PEEK. Its high hardness and heat resistance make it suitable for long production runs of abrasive materials.

How to Choose the Right Grade

For most applications, start with P20 for general use, upgrade to 718H for better surface finish needs, and choose H13 or S136 for demanding engineering plastics or medical applications. For a detailed analysis of your specific application, read our full steel comparison guide.