Using the wrong die steel is common, but if the die steel is suitable for the mold, there will be no issues with the mold.
I just received a phone consultation from a netizen. They are using Cr12MoV for 1.5-thick stainless steel drawing, but the steel gets scratched after drawing a few hundred pieces. The drawing height is 10mm, and the product quantity is high, with a demand of 30,000 pieces per month. The dimensions are not large, and the material usage is not extensive. They are drawing square boxes from plates, but the molds need to be rough machined, quenched and hardened, and then fine machined. Tungsten steel cannot be used, and the mold steel cost should not be too expensive. What die steel should be used?
Using Cr12MoV to stretch stainless steel is a major mistake. Using Cr12MoV to stretch stainless steel will inevitably cause the die to stick and result in wire drawing, even with a coating. Therefore, this is an irreversible mistake.
The wire drawing of the stretched mold is caused by the adhesive wear of the viscous material, which is due to the presence of microcracks in the mold steel structure. When these microcracks come into contact with stainless steel during stretching, adhesive wear of the viscous material occurs, resulting in wire drawing of the product.
Cr12MoV is a high-carbon Cr12 series die steel with a carbon content of 1.5%, which exhibits severe segregation and numerous microcracks. Therefore, using Cr12MoV for drawing dies will inevitably result in wire drawing, and coating is also ineffective.
Given his request for lower die steel costs and considering that it is 1.5mm thick stainless steel with harsh working conditions, the only solution is to use non-stick mold steel with a surface coating.
Easy to coat, with few fine cracks, and at an affordable price, we recommend three types of tool steel:
1) 8503 tool steel, which is non-stick to materials, has a hardness of HRC59-61. Its resistance to chipping is twice that of DC53. However, compared to DC53, while its performance is doubled, its price remains the same, and it also offers the added benefit of being non-stick to materials. This is the preferred choice for balancing multiple properties such as toughness, strength, non-stickiness, and ease of coating.
2) Wear-resistant steel 6077, with a hardness of 60-63HRC, has an anti-chipping performance three times that of chromium steel. A customer once stretched a 0.7mm thick galvanized sheet for a motor housing, with a stretching height of 30mm. The wear-resistant steel 6077 was used to stretch 3 million products, and the mold did not break down. The customer did not complain, and the results were much better compared to the original DC53. When using DC53, the Teel would start to wire-draw shortly after production, leading to customer complaints and severe criticism. Now, with 8503, the results are very satisfactory.
3) We recommend the Cr8 series cold work die steel, specifically Cr8Mo2VSi, which has a carbon (C) content of 1.0% and a hardness of HRC60-62. This steel has a low carbon content, minimal segregation, and less severe microcracks compared to Cr12MoV. The coating can cover these defects, and it is widely recognized and relatively inexpensive.
The main grades of cold work die steel in the Cr8 series include PD613, AB88, K340, DC53, and other die steels.
Selecting tool steel is like answering multiple-choice questions. Only when the preconditions are clear can there be a correct answer. The more specific the working conditions are, the more obvious the answer becomes. However, without understanding tool steel and lacking case experience, even with clear preconditions, it can be difficult to find the right answer. Similarly, the current material selection is also incorrect.
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