For hot forging of 35 steel heated to 1100°C, the heat-resistant steel 8433 increased die life from 5,000 to 10,000 cycles. This good news was shared with me yesterday by Mr. Wang, who has been using 8433 for over two years.
Mr. Wang specializes in hot forging and stamping of 35 steel, a process with relatively high production speeds. Since 35 steel must be heated to 1100°C, he previously experienced frequent mold collapse. Believing the hardness was too low, he switched to higher-hardness steels like SKD11 and DC53, but these still were prone to cracking and wear.
He then considered applying a PVD coating to the DC53 and SKD11 to improve the dies’ wear resistance. However, even after coating, the dies would develop deep cracks along the cutting edges after producing just 5,000 parts, and there was also surface scuffing. He had always believed that the dies’ low hardness was the cause of the wear. He also tried using high-hardness DC53 and SKD11 and applying PVD surface treatment, but the die life remained short, which left him quite frustrated.
When hot forging professionals encounter die collapse, their first instinct is to increase the hardness of the die steel—this is their only solution. In fact, this approach is flawed.
After Mr. Wang contacted me on September 24, 2024, I observed that his hot forging dies were made from cold work die steel—a material selection error. Given that his hot forging equipment consists of high-speed punch presses—which involve a “clap-like” momentary contact—the die temperature typically reaches 600°C. You need to select a die steel with a tempering temperature close to 600°C; this ensures the die’s hardness won’t be easily annealed away, guarantees its red hardness, and prevents die collapse and cracking. I recommended he use heat-resistant steel 8433.
8433 is a proprietary heat-resistant steel from Yuhui Mold Steel. It far surpasses competing products in multiple metrics—including high heat resistance, fatigue resistance, and thermal conductivity—and its performance is second to none. The heat resistance and stability of 8433 are 2–3 times that of H13, with a hardness of 50–54 HRC, and it will not anneal out over its service life. It is particularly worth emphasizing that even if the mold is repaired to the point of being scrapped, the hardness on the back surface will not decrease. We have a customer who hot-forges 42CrMo flanges. Previously, when using H13 to produce 3,000 products, the mold would collapse and crack at the edge. However, after switching to heat-resistant steel 8433, the mold has been reground four times without any reduction in service life, consistently producing over 10,000 products each time.
Today, Mr. Wang also told me that when he hot-forges 35 steel at 1,100°C using 8433 die steel, the service life has remained stable at 10,000 cycles over the past two years, and he is very satisfied with the results. Compared to the high-hardness DC53 and SKD11 steels he used previously—which were even PVD-coated—the service life has doubled. He’s very pleased, and today he came to consult me on material selection for another new product. After our conversation, I received this good news, and I’m actually quite happy about it too.
Withstanding the heat of 1100°C and enduring two years of testing, the fact that 8433’s service life has remained stable at 10,000 cycles demonstrates its excellent heat resistance and stability. It clearly meets the high heat resistance requirements of hot forging dies, and a service life of 10,000 cycles—compared to the previous 3,000–5,000 cycles—represents a doubling of lifespan. I’m truly delighted that our product can help customers solve problems, extend service life, and improve production efficiency.
When it comes to hot forging dies prone to collapse and cracking, using 8433 die steel is even more satisfying than eating braised pork! If your hot forging dies are also experiencing collapse or cracking, you should definitely give 8433 die steel a try.
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Wu Dejian’s tool steel, the chief of staff of the user, bought everything he had used.