Tungsten steel hot-forging dies are too expensive—what die steel should be used as a substitute? I can tell you now that 8566 die steel, with its high heat resistance, high hardness, and high toughness, is the most suitable replacement.
I saw 17 pieces of 8566 round bar ordered by a nut hot-forging die manufacturer in the workshop, which prompted me to share this with you. This customer manufactures nut hot-forging dies for 35CrMo material. They used to use tungsten carbide dies, which worked fine, but after the price of tungsten carbide tripled, the die costs became unsustainable. The customer couldn’t accept the price hike, which resulted in them losing orders.
Tungsten carbide is a tungsten-cobalt alloy with excellent heat resistance and a hardness of 86–89 HRA. When used as die steel for hot-forged nut dies, this high-heat-resistant, high-hardness tungsten carbide offers exceptional wear resistance; as long as the die doesn’t crack, its service life can reach hundreds of thousands of cycles. However, with the price of tungsten carbide having tripled, some dies have become unaffordable, affecting the die manufacturer’s ability to secure orders—hence the need to find an alternative material.
However, for our hot-forging die sets for nuts, we still prefer a die steel that offers high heat resistance, high hardness, and excellent resistance to thermal wear to ensure a long die life, as well as good toughness to prevent cracking.
Thermal wear resistance is a comprehensive metric. First, the die steel must possess high heat resistance so that its hardness is not annealed away during high-temperature operation—only then can red hardness be guaranteed, which is the foundation for preventing die collapse. On this basis, the die steel must also possess high hardness to ensure good thermal wear resistance.
Resistance to thermal wear is fundamental to ensuring the longevity of your hot-forging dies. High toughness and high thermal conductivity ensure that the die will not develop cracks during rapid cooling and heating with water, resulting in products with a good surface finish rather than cracks that would render them scrap. The only die steel that meets the requirements of high heat resistance, a hardness of HRC 60, and excellent toughness is 8566 die steel.
The heat resistance of 8566 is comparable to that of high-speed steel SKH-51, with a hardness of 58–60 HRC and four times the toughness of SKH-51. 8566 strikes the perfect balance between high heat resistance, high hardness, and high toughness—a feat that other die steels cannot achieve. Thanks to its high heat resistance and hardness, 8566 also exhibits excellent resistance to thermal wear. Combined with its high toughness, the die remains crack-free, resulting in products with a superior surface finish.
As our boss Zhang said, when hot-forging 304 stainless steel, 8566 earns a five-star rating—the finished products have excellent surface finish, looking just like they were made from tubing. Our hot-forging dies for nuts require high heat resistance, high hardness, and high toughness. Since 8566 possesses all three of these properties, the hot-forging dies for nuts made from it have a long service life.
After the price of tungsten steel tripled last year, this client began searching for an alternative. He scoured the country for every available hot-work die steel to compare, and after testing them all, he found that 8566 still offered the longest service life. He has now started purchasing in bulk and has ordered another 17 pieces this time.
If you want your hot-forging dies for nuts to have a long service life, but tungsten steel is too expensive and other die steels are prone to die collapse and have short lifespans—and you’re unsure which material to use—then 8566 die steel, with its high heat resistance, high hardness, and high toughness, is definitely worth a try.
*************
Wu Dejian’s tool steel, the chief of staff of the user, bought everything he had used.