Mr. Lu asked: A die for cold heading with a small intermediate step and a sleeve cracked after being used for over 10,000 cycles. The material of the part is 10B21. We’ve tried tungsten steel and white steel—are there any die steels with better toughness?
Cold heading die plates are the parts that are struck, and since they are very thin, they require exceptionally high toughness.
Tungsten steel is a tungsten-cobalt alloy with extremely high hardness and excellent wear resistance, but it is very brittle—this is the wrong material for the application.
White steel is also a type of high-speed steel. Although its toughness is slightly better than that of tungsten steel, it still fails to meet the toughness requirements for parts subjected to impact, so this is clearly the wrong material choice.
For cold heading die inserts like these, our past customers have used 8566 anti-chipping steel because its resistance to chipping is four times that of SKH-9 high-speed steel 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 severe conditions—such as stainless steel stamping, sharp-corner stamping, narrow-flange stamping, and operations where the hole diameter is smaller than the sheet thickness or the stamping ratio is less than 1:1—cracking issues that standard die steels cannot resolve are consistently addressed using 8566 die steel.
Mr. Li was cold heading carriage screws using die plates. The customer reported that the die plates were prone to cracking. He had tried both Cr12MoV and 8566 steel, but both were prone to cracking. He asked for a recommendation on a suitable die steel. After switching to 8566 crack-resistant die steel, the die plates stopped cracking. Using 8566 die steel for the punches made all the difference—it was like night and day.
Mr. Lu’s cold heading die plates, made of tungsten steel and white steel, cracked after just 10,000 strokes. You’re using the wrong material—you need to use 8566 crack-resistant steel.
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Wu Dejian’s tool steel, the chief of staff of the user, bought everything he had used.