Which mold steel doesn’t stick to aluminum chips? A question from a viewer during the 298th live stream.
When mold steel sticks to aluminum chips, it is due to adhesive wear caused by material adhesion—specifically, segregation issues in the mold steel. The microstructure contains a large number of microscopic cracks invisible to the naked eye. When aluminum powder comes into contact with these cracks, it penetrates into the mold along them, leading to adhesive wear—which is what we refer to as sticking and aluminum chip adhesion.
Therefore, for mold steel to prevent aluminum swarf adhesion, it must be of high metallurgical quality—free from segregation and microcracks. When the grain size is fine and the density is high, the mold steel will naturally not adhere to aluminum swarf.
As for high-speed steels such as Cr12MoV, DC53, SKD11, and even SKH51, their tendency to attract aluminum chips stems from their excessively high carbon (C) content. Their microstructure after heat treatment contains numerous microcracks—an inherent defect of high-carbon steel. Combined with poor smelting quality, this leads to severe segregation in the mold steel, The abundance of microscopic cracks makes it inevitable that these steels will stick to aluminum chips. Even if a coating is applied, it merely covers the cracks rather than eliminating them. The root cause of why some coated molds still stick to aluminum chips lies in these microscopic cracks.
I’d like to recommend two types of mold steel that do not stick to aluminum chips:
The first is the non-stick 8503 mold steel. 8503 is a proprietary non-stick mold steel developed by Wudejian Mold Steel. It has a hardness of 59–61 HRC and twice the toughness of DC53. Compared to DC53, its performance is doubled without a corresponding increase in price, and it offers the added benefit of being non-stick.
In the words of Mr. Lin from Tangxia, Dongguan: “We use 8503 tool steel for cold-extrusion aluminum profiles. It doesn’t stick to aluminum powder, doesn’t crack, and is quite affordable. We used to use Cr12MoV, DC53, and SKH-9—either they’d stick to the material or they’d crack—but now we’re having great results with this!”
The second option is 8566 chipping-resistant steel, with a hardness of HRC 58–60. Its resistance to chipping is four times that of SKH-9 high-speed steel and twice that of D2. It resolves the chipping issues that high-hardness die steels like D2, DC53, SKH-9—particularly in the harsh conditions of stainless steel stamping, sharp-corner stamping, narrow-flange stamping, and thick-sheet stamping, where conventional mold steels are prone to chipping or cracking. These issues are all effectively resolved with 8566 anti-chipping steel.
The reason 8566 has such excellent resistance to chipping is that it is produced through high-quality smelting—it has no segregation issues or microcracks, so it possesses both high hardness and high strength. Mr. Qi punches 2mm aluminum sheets. The narrow-edge punch is 2.05mm wide. With the original punch, it was prone to chipping and sticking to aluminum shavings, but with the 8566 punch, he has produced tens of millions of parts, and it has shown absolutely no wear. From last year to this year, the punch’s cutting edge has never needed sharpening.
According to the information provided by Mr. Qi, when punching 2mm aluminum sheet, the 8566 punch can withstand 1 million strokes without needing to be sharpened and without sticking to aluminum chips.
The user asked which die steel doesn’t stick to aluminum chips? Based on current successful case studies, the die steels that do not stick to material are 8503 or 8566 anti-chipping steel.
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Wu Dejian’s tool steel, the chief of staff of the user, bought everything he had used.