During my 295th live stream, a viewer asked me: “For PA6 reinforced with 30% glass fiber, with a required mold life of 300,000 cycles, what type of mold steel should be used?”
30% glass-fiber-reinforced nylon is a material that causes significant erosion to molds. To withstand the erosion caused by nylon reinforced with 30% glass fiber, you must select a mold steel with high hardness that resists material adhesion. However, since the required mold life is only 300,000 cycles—which is not a large number—you simply need to opt for a hard mold steel.
A “hard mold” refers to a plastic mold steel that can be quenched and tempered to a hardness of 50 HRC. Specific grades include 4Cr5MoSiV1 (H13), SKD61, 2344, and 8407.
If you prefer stainless steel, you can choose 4Cr13-type grades, such as S136 or 2083. These materials are all suitable, provided you opt for a “hard mold” and harden the mold to 50 HRC through quenching and tempering, which will meet your requirement of 300,000 cycles.
However, if you require 1 million cycles, I recommend using 8503 mold steel, which resists material sticking. This is because, based on feedback from past customers, standard mold steel quenched and tempered to 50 HRC can only achieve 300,000 to 500,000 cycles when molding 30% glass-fiber-reinforced nylon. However, one of our customers, Mr. Wan, told me that with a 30% glass-fiber-reinforced nylon compound, 8503 can achieve 1 million mold cycles.
8503 is a non-stick mold steel exclusive to Yuhui Mold Steel. With a hardness of 55–61 HRC, it has twice the toughness of DC53. Compared to DC53, its performance doubles without doubling the price, while also offering the added benefit of non-stick properties. In particular, this non-stick property, combined with its high hardness, provides a fundamental and effective solution to the problem of molds being worn down by nylon compounds with high fiber content, which often leads to flash on the products.
As Mr. Yu from Zhejiang put it, using 8503 mold steel for a 30% glass-fiber-reinforced nylon compound works quite well—you can keep molding without any flash. Now we can add that, as Mr. Wan says, 30% glass-fiber-reinforced nylon compounds processed with 8503 mold steel can easily withstand 1 million cycles.
As for the netizen who mentioned only 300,000 cycles for 30% glass-fiber-reinforced nylon—you just need to opt for a hard mold. You can use H13, SKD61, 2344, or even stainless steel grades like S136, 2083, or even 4Cr13. The key is to harden it to 50 HRC through quenching and tempering, which will meet your requirement for a 300,000-cycle lifespan. However, if you need 1 million cycles, you’ll have to use 8503 mold steel, which resists material sticking.
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Wu Dejian’s tool steel, the chief of staff of the user, bought everything he had used.