Mr. Yu asked which die steel material would be more wear-resistant for the cutting edge and punch when processing titanium alloy, with a material thickness of 0.3 mm.
I asked him in return, “What die steel are you currently using, and what problems have you encountered?”
He said he is currently using SKH-9, but the cutting edge wears down easily—he has to resharpen it before reaching 10,000 units.
If the cutting edge needs sharpening before reaching 10,000 units, barring any unforeseen issues, this is likely caused by adhesive wear due to material sticking, resulting in burrs on the product. There are two solutions:
First, apply a coating to the current SKH-9 high-speed steel to improve surface finish, eliminate the fine cracks inherent in SKH-9, and prevent adhesive wear caused by material sticking. This will extend the mold’s service life. Furthermore, the coating will enhance wear resistance, making the cutting edge more durable.
Second, use tungsten steel or powdered high-speed steel for stamping 0.3mm-thick sheet metal. The primary consideration here is wear resistance; using materials with a higher total alloy content and greater hardness will improve wear resistance, thereby extending the service life of both the cutting edge and the punch. Of course, the quality of the smelting process is also critical. Adhesive wear caused by material sticking is often due to poor smelting quality of the die steel, resulting in deviations in the steel’s properties and the presence of microscopic cracks invisible to the naked eye. These defects lead to adhesive wear during the friction of the stamping process.
Mr. Yu replied that he had tried using tungsten steel, but it was not durable either.
If even tungsten steel is not durable, it further confirms that the rapid wear of the cutting edge is caused by adhesive wear due to material sticking. We must improve the smelting quality of the die steel and use high-quality powdered high-speed steel with no segregation or micro-cracks in its microstructure, such as PM23 or PM60.
SKH-9 is a conventionally cast general-purpose high-speed steel with a hardness of 62–64 HRC. While it offers excellent wear resistance, the conventional casting process can lead to alloy segregation and the formation of numerous microscopic cracks that are invisible to the naked eye. When these fine cracks come into contact with titanium materials during stamping, they cause adhesive wear, resulting in burrs on the finished product. This type of adhesive wear is unrelated to the mold’s hardness level. The fact that this issue occurs after just 10,000 stamping cycles further corroborates this point.
In contrast, PM23 is a powder-metallurgically produced high-speed steel. Thanks to the advanced powder metallurgy process, it eliminates these microscopic cracks invisible to the naked eye. Consequently, it prevents material adhesion and product scratching while also enhancing the mold steel’s resistance to chipping. PM23 has a hardness of 64–66 HRC, with 6.5% tungsten (W) and 3.0% vanadium (V). It features high carbon content for high hardness, high alloy content for high wear resistance, and no material adhesion, making it a high-speed steel that combines both high hardness and high strength.
Mr. Song was stamping nickel-plated steel strips made of 0.4mm-thick hard SUS304 material
with a hardness of 3/4 HRC. The material’s surface was nickel-plated. When using SKH-9 as the punch, it wore out after only 30,000 stamping cycles. However, when switching to Yuhui PM23 powder-metallurgy high-speed steel, the punch withstood 50,000 stamping cycles without any signs of wear.
This nickel-plated strip is similar to titanium in that it tends to stick to the die, and SKH-9 also wears out easily. However, using PM23 doubles the service life and delivers the desired results.
Considering the performance requirements for stamping 0.3mm titanium, I recommend PM23 powdered high-speed steel with a hardness of HRC 64–66. Its service life is definitely better than SKH-9, and the cost is lower than tungsten steel. If your budget allows and you want even better performance, you can use PM60 powdered high-speed steel with a hardness of HRC 67–69.
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Wu Dejian’s tool steel, the chief of staff of the user, bought everything he had used.