Question from a live stream viewer: How does M42 perform when punching 1.5 304 stainless steel or performing drawing operations?
M42 is a W2Mo9Cr4V2Co8 high-speed steel with 8.0% cobalt content. It has a heat-treated hardness of 65–68 HRC and offers excellent wear resistance and red hardness; However, due to its high total alloy content, the material is relatively brittle and prone to chipping when used for punching thick, hard sheets. Additionally, as it is a conventionally cast high-speed steel, it suffers from severe segregation, which further reduces its resistance to chipping. The presence of numerous microcracks also makes it susceptible to adhesive wear caused by material buildup.
Therefore, using M42 to punch 1.5-thick 304 stainless steel will most likely result in chipping or cracking, unless you’re simply punching a round hole with no narrow edges or sharp corners. If you lower the hardness slightly, it might work, but its wear resistance is also excellent—this is something we must acknowledge.
However, from an economic standpoint, given that the price has already reached the level of M42, I would rather use PM23 powdered high-speed steel with a hardness of HRC 64–66. Using it to punch 1.5 mm thick 304 stainless steel will prevent corner chipping, and it also offers excellent wear resistance. We have a customer who uses PM23 powdered high-speed steel to punch 1.5mm-thick stainless steel. They’ve been able to produce 200,000 parts, quadrupling the die’s service life while also resolving the two frustrating issues of material sticking and part damage caused by pressure.
If you use M42 high-speed steel to draw 1.5mm-thick 304 stainless steel, the die is very likely to develop drawing marks unless it is coated. This is because M42 suffers from severe microstructural segregation and contains many fine cracks, making it prone to drawing marks when used for drawing dies. Generally, M42 is not recommended for stainless steel drawing dies because it is too expensive, and the likelihood of drawing marks is very high—it’s not worth the risk.
For drawing 1.5mm-thick 304 stainless steel, if the budget allows, you can use carbide dies directly. If a coating is required, M2 high-speed steel is sufficient. With a hardness of HRC 62–64, it offers adequate hardness and wear resistance, along with the added benefits of lower cost and better toughness. Using M42 for drawing dies is a compromise—it’s neither here nor there—and it’s exorbitantly expensive, making it uneconomical.
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Wu Dejian’s tool steel, the chief of staff of the user, bought everything he had used.