In the process of manufacturing plastic injection molds, purchasing personnel and engineers frequently encounter the material names 1.2311 and P20. Because both often appear together in mold steel catalogs, many people assume they are the same type of steel. In reality, while they are generally considered corresponding or very similar grades, their naming systems differ. P20 primarily belongs to the AISI/SAE system, while 1.2311 is a common Werkstoff material number under the DIN/EN system. Therefore, in actual procurement, one cannot simply assume they are interchangeable based on their names; it is also necessary to verify the chemical composition, hardness, delivery condition, and material certification.
What is 1.2311 mold steel?
1.2311 is a pre-hardened chromium-molybdenum plastic mold steel, commonly known as 40CrMnMo7. Depending on the supplier and standard, its pre-hardened state typically ranges from approximately 280–325 HB, or about 29–33 HRC. Due to its combination of strength, toughness, and good machinability, 1.2311 is widely used in the cavities, cores, mold bases, and other mold structural components of plastic injection molds.
A major advantage of 1.2311 is that it can be directly machined in its pre-hardened delivery state. For common molds, this means that complex quenching processes are usually unnecessary during roughing and finishing, reducing the risk of deformation from heat treatment and shortening the mold manufacturing cycle. Furthermore, 1.2311 has good polishing properties, meeting the surface requirements of many common plastic product molds.
What is P20 steel?
P20 is a very common pre-hardened plastic mold steel in the mold industry, mainly used for injection molds, mold bases, cores, and cavities. Depending on the specific standard, steel mill, and delivery condition, the hardness of P20 is typically around 28–36 HRC.
P20 is widely used primarily because it achieves a good balance between machinability, toughness, strength, and polishability. For general plastic molds and medium-volume production, P20 provides sufficient performance while offering a better cost advantage compared to some high-alloy, high-hardness mold steels.
So what exactly is the difference between 1.2311 and P20?
The most important point to note is that 1.2311 and P20 are not two completely different mold steels. In the mold industry, they are often used as corresponding grades under different standard systems. Some steel suppliers even directly list 1.2311 as the corresponding material for AISI P20.
However, it's crucial to understand that "corresponding grade" does not mean "completely identical in all cases." Different standards and steel mills may have differences in chemical composition, steel purity, hardness, heat treatment conditions, and flaw detection requirements. Therefore, if the customer's drawings explicitly specify P20, it's best to confirm the corresponding standard and technical requirements during procurement, rather than simply substituting "P20 = 1.2311".
For example, when the mold size is large, the steel cross-section is thick, and high requirements are placed on the uniformity of hardness and polishing effect across the entire cross-section, ordinary P20/1.2311 may not be the most ideal choice. In this case, upgraded mold steels such as nickel-containing 1.2738/P20+Ni can be considered to obtain better cross-sectional uniformity and polishing performance.
Should you choose P20 or 1.2311?
For general plastic injection molds, mold frames, cores, and cavities, P20 or 1.2311 is usually an economical and practical choice. However, if the project involves large molds, deep cavities, high-gloss products, or has higher requirements for cross-sectional hardness uniformity and polishing performance, you shouldn't simply focus on "P20 or 1.2311," but should further consider more suitable materials such as 1.2738.
For purchasing personnel, a more reliable material selection method is to simultaneously compare material certificates, chemical composition, hardness, ultrasonic testing, and delivery condition. The grade is only the first step in purchasing decisions; what truly determines the mold's performance is the quality of the steel itself and the specific technical requirements.
If you need to purchase P20/1.2311 mold steel, it is currently available in various forms such as plates, blocks, flat bars, square bars, and round bars, and can be further processed by cutting, milling, grinding, and drilling.
In conclusion, 1.2311 vs P20 is not simply a comparison between two different mold steels. In most plastic mold applications, they belong to pre-hardened plastic mold steels that are highly correlated under different standard systems. What truly matters is the material standard, chemical composition, production quality, hardness, and delivery condition. Don't just look at the grade when purchasing, especially for large, high-precision, or high-gloss molds; you should select the material based on the actual application requirements.
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FAQ
Q1: Is 1.2311 the same as P20?
They are often considered corresponding or equivalent grades, but the specific standards, chemical composition, and delivery condition should still be confirmed during actual procurement.
Q2: Is 1.2311 suitable for making injection molds?
Yes. It has good processability, toughness, and polishing properties, making it suitable for a wide range of common plastic injection molds.
Q3: What are the common hardness values for P20/1.2311?
Depending on different standards and suppliers, the pre-cured state is typically around 28–36 HRC.