Yesterday, Mr. Shi came to Yuhui again to purchase 8566 crack-resistant steel, and he told me: “For cold heading dies, 6.0 40Cr forming dies are prone to cracking. I’ve tried Cr12MoV, DC53, 8566 from a fourth-hand supplier in Ningbo, and Yuhui’s 8566. After comparing them, your Yuhui 8566 die steel still has the longest service life.”
Mr. Shi’s die is used for cold heading 6mm-thick 40Cr material to reduce its thickness. Since 40Cr is an alloy steel with relatively high hardness, the cold heading die must withstand immense forces, requiring the die steel to possess excellent crack resistance. Additionally, because the die features a ramped profile, it demands high wear resistance as well. This is an application that requires both wear resistance and crack resistance simultaneously.
For this type of cold heading die, using Cr12MoV with a carbon (C) content of 1.5%—a high-carbon, high-chromium cold work die steel—is too brittle and is definitely the wrong choice; using DC53 with a slightly lower carbon content is somewhat more viable, but under such severe, high-stress conditions, even DC53 cannot withstand the load and is prone to chipping, as his current test results have already confirmed.
The “Four-Copy” 8566 purchased in Ningbo is also prone to chipping, which is to be expected. “Four-Copy” 8566 merely copies my product descriptions, advertising slogans, and case studies—but the mold steel grade is inferior to mine. Since they cannot replicate my material composition or heat treatment process, its resistance to chipping is naturally poor, and chipping is inevitable. After conducting verification and comparison, Mr. Shi stated that the “Four-Copy 8566” has a service life less than half that of your Yuhui 8566 anti-cracking steel, which further corroborates this point.
8566 is a proprietary anti-spalling steel developed by Yuhui Mold Steel, primarily designed to address mold spalling. It is not a national grade but rather our company’s proprietary grade and intellectual property; it is not in the public domain. 8566 anti-spalling steel has been used in over a thousand cases across five stamping operating conditions, six major material types, and seven major industries.
However, due to 8566’s high market visibility, strong sales, and customers specifically requesting it, it has attracted widespread “four-fold copying” by competitors across the internet. Not only are there direct copies of 8566, but also “shadow” versions of 8566; it has even become a reference standard for certain major steel mills—an unprecedented and bizarre phenomenon in the industry.
The 8566’s resistance to chipping is four times that of high-speed steel SKH-9 and twice that of D2, with a hardness of HRC 58–60. It resolves chipping issues that high-hardness die steels such as D2, DC53, and SKH-9 cannot address; In particular, under harsh conditions—such as stainless steel stamping, thick-plate stamping, cold heading dies, sharp-corner stamping, narrow-flange stamping, and stamping where the hole diameter is smaller than the plate thickness or the stamping ratio is less than 1:1—cracking issues that conventional die steels cannot resolve are all addressed using 8566 anti-cracking steel.
I was delighted to receive the good news that, after comparing Cr12MoV, DC53, 8566 (four-pass), and 6mm 40Cr cold heading steel, Yuhui’s 8566 still had the longest service life.
I believe there are many others facing similar cold heading conditions where their dies are prone to chipping, resulting in short service life. That’s why I’m documenting this case and sharing it with everyone—so that when cold heading dies chip, people will think of 8566 anti-chipping steel and avoid the frustration of chipping.
Using 8566 die steel for punch chipping makes all the difference—it’s like night and day.
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Wu Dejian’s tool steel, the chief of staff of the user, bought everything he had used.