1. Common Types of Mold Steel Plates and Their Applications
(1) P20 Steel (1.2311)
P20 steel is often regarded as the industry’s most versatile mold material. Supplied in a pre-hardened state (typically HRC 28–33), it offers good machinability and polishability. It is widely used for manufacturing large or general-purpose plastic product molds, such as those for TV housings, household appliances, and daily-use items.
For general-purpose molds where cost efficiency matters, P20 steel remains a safe and reliable option.
(2) 718 Steel (1.2738)
You can think of 718 as an upgraded version of P20. With the addition of nickel it provides better hardenability and more uniform hardness distribution across the entire cross-section.
This makes it particularly suitable for large mold bases, effectively preventing soft cores in thick sections. It is commonly applied to molds for automotive bumpers and large appliance housings.
(3) S136 / 420SS
S136 (also known as 420 stainless steel) belongs to the corrosion-resistant, mirror-polish mold steel category.
If you are producing transparent plastic parts such as lenses or light guides, or products requiring a high-gloss surface like CDs, S136 is the ideal choice. Its high chromium content ensures excellent rust resistance, allowing it to withstand corrosive plastics such as PVC and maintain a mirror finish over long production cycles.
2. Beyond Selection: Mold Maintenance is Key to Longevity
(1) Proper Storage
Molds should be stored in a clean, dry environment, protected with anti-rust oil, and covered to prevent dust or moisture contamination.
(2) Cleaning and Upkeep
After each production run, thoroughly clean the cavity, runners, and vents to prevent residual plastic from decomposing and carbonizing. Regularly lubricate moving components such as ejector pins and sliders.
(3) Damage Repair
Minor scratches or rust should be repaired promptly using professional polishing tools to prevent further deterioration.
3. Conclusion: A Smart Choice Multiplies Your Results
Understanding the economic practicality of P20, the superior hardenability of 718, and the corrosion resistance of S136 provides a strong foundation for sound decision-making.
Once in production, consistent and careful mold maintenance protects your investment and ensures long-term reliability.
By combining smart material selection with dedicated upkeep, your molds become truly powerful assets in value creation.