Today, we received another inquiry from a customer asking which is the best steel for injection molds. We then asked how many units of the product were planned for mass production. The customer said that within 5 years, only a little over one hundred thousand products would be made. We roughly reviewed the product dimensions. With a two-cavity mold, that actually comes to only about 70,000 to 80,000 molding cycles. As for precision requirements, they were only moderate, not especially high, so we felt there was no need to use such a high-grade steel.
The more expensive the steel, the more stable it is. The higher the hardness, the more reassuring it feels. The higher the grade, the less likely problems will occur. This idea is not entirely wrong, but in numerous instances, it is not completely suitable for a specific project. If a project can be completed with only a small investment, but an expensive steel mold is purchased anyway, then that extra money is simply wasted.
It is exactly because we have encountered this type of question so many times over the years that today MoldSteelLS wants to write this article specifically to discuss a very practical topic:
The first thing to consider is how many units you estimate can be produced in about two years. Do not assume that one mold can produce parts for a lifetime; that is unrealistic. Even if the steel itself does not age, product updates happen so quickly that a mold opened this year may already be obsolete next year. Unless you are producing multiple batches every year for 5 to 8 consecutive years, with hundreds of thousands of products.
Below 50,000 Mold Cycles
If the product is non-transparent, 45# steel is sufficient, and the price is also relatively reasonable. Although many people feel that 45# steel is soft, it is still steel after all, and its hardness is much higher than that of plastic. In actual use, it is adequate and also helps save cost.
Around 100,000 Mold Cycles
If the product does not have high transparency requirements, P20 mold steel can be selected. Approximately 50% of injection molds use this grade, and it is very common in China’s injection molding industry. Its delivery hardness is about 35 HRC, making it suitable for most household product molds and automotive part molds. It has good machinability, and its polishing performance is also acceptable. Overall, it offers relatively high cost performance.
Above 200,000–300,000 Mold Cycles
If the product size is tiny and the mold to be made is also not large, choosing 718 will not cost much more, so it is better to use 718 directly. If the product has high transparency requirements, or if the mold needs to run for several hundred thousand cycles, we recommend directly purchasing 718 steel.
By comparing the previous approach of blindly using the best steel with the more reasonable approach of selecting suitable steel after understanding the production quantity of the product, it becomes clear approximately how much cost can be saved.
| Steel Grade | Approximate Price Range (USD/kg) | How Much Cheaper Than 718 | Recommended Mold Life Range |
|---|---|---|---|
| 45# Steel | $0.92—$1.38 | Approximately 60% — 75% cheaper | Below 50,000 mold cycles, non-transparent parts, budget-sensitive projects |
| P20 | $1.85—$2.77 | Approximately 30% — 50% cheaper | Around 100,000 mold cycles, conventional products, general automotive parts |
| 718 | $3.08—$4.62 | — | Transparent parts, small high-requirement products, above several hundred thousand mold cycles |
Note: The above prices are approximate ranges and do not represent current official prices. Actual prices still depend on the latest quotations from various steel brands. Based on the long-term price differences among these three steel grades, the range is approximately within this level.
