I saw two re-forged ejector pins in the workshop and wanted to share this with everyone. This is the first time we’ve used high-toughness LG die steel for ejector pins in aluminum extrusion dies, so I thought I’d document this new case.
These two ejector pins were forged from high-toughness LG tool steel. This customer manufactures aluminum extrusion dies. When they originally used H13 for the ejector pins, the material lacked sufficient strength and was prone to swelling and deformation. They wanted a tool steel with high hardness and good toughness. After comparing options, they opted for high-toughness LG die steel.
LG’s toughness is 8–9 times that of DC53, with a hardness of 54–58 HRC. It’s so tough that you can bend it with a hammer without breaking it. LG offers both high hardness and high strength—qualities H13 lacks—while also outperforming H13 in heat resistance, resistance to thermal stress, and resistance to metal erosion.
The ejector pins in aluminum extrusion dies are subjected to immense forces during the pushing process. These pins must possess both high hardness and high toughness: high hardness prevents them from being swaged out of shape or worn away, while high toughness prevents them from breaking.
H13 is a medium-carbon hot-work die steel (4Cr5MoSiV1) with a hardness of HRC 50 and good toughness; however, its strength is too low, which is why some ejector pins subjected to high loads are prone to bulging and deformation.
LG has 8–9 times the toughness of DC53 and a hardness of 54–58 HRC. Its toughness is so high that it won’t break even if you bend it with a hammer, making LG ideal for this type of aluminum extrusion die. If you use H13, it’s prone to bulging and deformation, and there’s no way to prevent it. In this case, you might want to consider using LG die steel.
After hot forging, the fiber structure of LG forms closed loops within the part, which helps improve the part’s strength. For this punch with a head diameter of 120 mm, we will upsize and elongate it using a 200 mm diameter die, and finally forge it to this size. The density will increase after the forging process, and the fiber structure will form closed loops within the part, which greatly helps improve the part’s strength—a property that machined parts simply do not possess.
If your pushrod or mechanical component requires high strength, and standard steels such as H13, 42CrMo, 40Cr, or 45 steel do not provide sufficient strength—even H13 would require upsetting—then you should consider trying high-toughness LG die steel for re-forging.
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Wu Dejian’s tool steel, the chief of staff of the user, bought everything he had used.