Just a reminder: Material sticking and stringing in drawing dies has nothing to do with the hardness of the die steel; it is determined by the quality of the steel’s smelting process. Whether your die steel was smelted to a high standard—and whether it contains any microscopic cracks—will determine whether your die experiences sticking or stringing issues.
If you’re talking about high hardness, many people use cemented tungsten steel for their drawing dies, yet they still experience sticking and stringing. Sticking and stringing aren’t caused by insufficient hardness of the die steel; they’re caused by poor metallurgical quality in the die steel you’ve chosen. If the grain size of the tungsten steel is too coarse, it will cause adhesion—which is what we refer to as sticking and stringing.
We have a client in Shanghai working with 1.0-thick stainless steel and a 10mm drawing height. He previously used DC53 and SKH-9 high-speed steel, both of which were prone to mold sticking and wire drawing, resulting in scratches on the product’s side walls and chipping on the corners of narrow-edge punches. However, after switching to Yuhui 8566 die steel—with a hardness of just 58–60 HRC— the die was able to produce 30,000–40,000 parts without cracking or stringing.
Their die punch features a step with a narrow edge that used to be prone to chipping. Without even asking me, they simply purchased the 8566 and put it to use. After producing 30,000–50,000 parts, they told me, “I’m drawing 1.0-thick stainless steel with a 10mm draw height, and the 8566 handled 30,000–50,000 parts without any issues—no stringing at all.” This case really surprised me.
Lately, many people have been asking me, “What’s the best tool steel for drawing dies?” and “Is stringing in drawing dies caused by the tool steel being too soft?” So I’d like to use this case to explain it to everyone.
Sticking and stringing in your drawing dies have nothing to do with the hardness of the die steel; they are determined by the quality of the steel’s smelting process. If the die steel you purchase has poor smelting quality—with severe segregation and a structure containing numerous microscopic cracks invisible to the naked eye—the die will stick to the drawn material during the drawing process. This sticking is what you refer to as stringing and material adhesion.
Moreover, this sticking tends to get worse over time—the more it sticks, the more severe it becomes. You might polish the die to make it usable again, but the problem will return before long. This recurring issue is caused by the poor smelting quality of the die steel.
I’d like to remind everyone: when selecting material for drawing dies—regardless of the material you’re drawing—the quality of the die steel’s smelting, the uniformity of its microstructure, and the absence of microcracks are absolutely critical. These factors are fundamental to determining whether your product will develop wire marks or whether the die will stick to the material.
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Wu Dejian’s tool steel, the chief of staff of the user, bought everything he had used.