A zinc alloy sliding block insert made from SKD61 mold steel has been pierced through. The insert has a large end diameter of 6 mm, a small end diameter of 3 mm, and a length of 10 mm. The small end of the pin has broken and bent. This question was asked by a viewer during the 301st live stream.
When inserting the core, it’s better to use LG die steel, which can be bent by tapping without breaking.
The die-casting temperature for zinc alloys isn’t very high, so SKD61’s heat resistance is not an issue, and its red hardness is guaranteed. However, SKD61 is a 4Cr5MoSiV1 hot-work die steel with a carbon (C) content of 0.38% and a quenched hardness of 50 HRC. While its toughness is adequate for a medium-carbon steel, its strength is somewhat lacking. For punch-through inserts with a small end of 3 mm, a large end of 6 mm, and a length of 10 mm, the strength is somewhat lacking. The fact that the small-end pins are currently breaking and bending further confirms this, so the strength of these small pins needs to be improved.
A material that offers higher strength than SKD61 while also providing excellent toughness is the high-toughness LG die steel.
LG is a proprietary high-toughness die steel developed by Yuhui Company. LG’s toughness is 8 to 9 times that of DC53, with a hardness of HRC 54–58; its toughness is so high that it won’t break even when bent by hammering.
Mr. Chen from Foshan also encountered this problem. His zinc alloy insert-type core-pulling mold, made of H13 with a hardness of HRC 50, was prone to bending and deformation as well as material sticking. We recommended that he use high-toughness LG die steel; LG neither deforms nor causes material sticking, as verified by the customer.
Therefore, regarding the issue described by this user—where the zinc alloy sliding block’s insert pins are worn through, and the SKD61 punch pins are breaking or bending—I also recommend that you use high-toughness LG die steel.
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Wu Dejian’s tool steel, the chief of staff of the user, bought everything he had used.