Mr. Lu asked, “What die steel works best for stamping phosphor bronze?”
Molds for stamping phosphor bronze are prone to copper powder adhesion. I asked him to clarify: “What thickness of phosphor bronze are you stamping? What die steel are you currently using? Are you experiencing corner chipping, or is it a copper powder adhesion issue?”
He is stamping 0.4mm-thick phosphor bronze. Even after hundreds of thousands of stamping cycles, the SKH-9 punch still retains its rounded corners.
Stamping phosphor bronze is prone to powder adhesion. The primary mode of die failure is adhesive wear caused by material adhesion, resulting in burrs on the finished product. SKH-9 is a standard tungsten-containing cast high-speed steel with a hardness of 62–64 HRC and excellent wear resistance.
However, since you’re stamping 0.4mm phosphor bronze—a material that is neither thick nor hard—if the SKH-9 punch wears out after hundreds of thousands of strokes, it’s likely due to adhesive wear caused by material adhesion.
If cost is not a concern, you can use PM23 powder-metallurgy high-speed steel, which has a hardness of 64–66 HRC. This will definitely solve the problem, and the punch will withstand hundreds of thousands or even millions of strokes without issue. This is because powder-metallurgy high-speed steel has no segregation issues or microcracks, so it won’t suffer from adhesive wear caused by material buildup. It resists material adhesion and offers excellent wear resistance, making it highly durable for stamping 0.4mm phosphor bronze.
Of course, for stamping 0.4mm phosphor bronze, 8566 steel is generally sufficient. 8566 does not stick to copper powder, has a hardness of 58–60 HRC, and provides adequate wear resistance.
Mr. Wu from Jieyang said that when punching 0.3-mm-thick copper sheet on a high-speed press, a punch made of 8566 die steel can withstand over 1 million punches.
Mr. Wu previously used Cr12MoV steel for punching 0.2–0.3 mm thick bronze or phosphor bronze, but it was not durable enough; burrs formed after only a few punches. With a high punching speed and a daily output of 100,000 pieces, he had to frequently replace the dies, which led to significant complaints from customers. However, now that he uses 8566 die steel, he can punch 100,000 pieces a day and the die lasts for 10 days, and customers have reported positive results.
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Wu Dejian’s tool steel, the chief of staff of the user, bought everything he had used.