Injection mold inserts play an important role in mold performance and product quality.
Choosing the right steel is not only about cost, but also about mold life, stability, and maintenance frequency.

In this guide, we will explain how to choose the best steel for injection mold inserts in a simple and practical way.

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🟦 1. What Is an Injection Mold Insert?

An injection mold insert is a replaceable steel part inside a mold. It is widely used in complex or high-wear areas.

For example:

  • ribs and bosses
  • threads
  • gate areas
  • detailed surface features

👉 The main advantage is simple maintenance. Only the insert is replaced instead of the full mold.

🟦 2. Why Steel Selection Is Very Important

Steel selection directly affects mold performance and production cost.

If the wrong steel is used, you may face:

  • early wear
  • rust problems
  • surface defects
  • short mold life

Therefore, correct steel selection is very important for long-term production.

👉 In addition, good steel reduces maintenance cost significantly.

🟦 3. Key Factors for Choosing Mold Insert Steel

✔ 3.1 Production Volume

First, consider how many parts you will produce.

  • Low volume → P20 steel
  • Medium volume → 718H steel
  • High volume → H13 or S136 steel

👉 As production increases, steel hardness becomes more important.

✔ 3.2 Plastic Material Type

Different plastics require different steel types.

For example:

  • Glass fiber reinforced plastics → high wear steel needed
  • PVC materials → corrosion resistance required
  • Standard PP/ABS → general steel is enough

✔ 3.3 Surface Quality Requirement

If your product needs high gloss surface, you should use:

  • S136 steel
  • NAK80 steel

👉 These steels support mirror polishing and high-end surface finish.

✔ 3.4 Wear Resistance Requirement

In high wear areas such as gates or sliders, steel must be strong enough.

Common choices include:

  • H13 steel
  • DC53 steel

👉 This helps extend mold life and reduce maintenance.

🟦 4. Common Mold Steel Types Comparison

🔹 P20 Steel

P20 is easy to machine and low cost.
However, it is not suitable for high-volume production.

👉 It is commonly used in prototype or low production molds.

🔹 718H Steel

718H provides a good balance between cost and performance.
Therefore, it is widely used in export molds.

🔹 H13 Steel

H13 has high hardness and excellent heat resistance.
In addition, it performs well in high wear conditions.

👉 It is ideal for gate inserts and high-pressure areas.

🔹 S136 Steel

S136 is a stainless mold steel.
It offers strong corrosion resistance and high polishing capability.

👉 Therefore, it is widely used in medical and optical parts.

🟦 5. Practical Engineering Recommendation

In real mold projects, we usually do not use only one type of steel.

Instead, we combine different steels for different areas.

For example:

  • Core insert → 718H
  • Gate area → H13
  • High gloss surface → S136

👉 This method improves performance and reduces cost at the same time.

🟦 6. Common Mistakes to Avoid

Many mold problems come from wrong steel selection.

For example:

  • Using P20 in high wear areas
  • Ignoring corrosion conditions
  • Choosing steel only based on price

👉 As a result, mold life becomes much shorter.

🟦 Conclusion

Choosing the best steel for injection mold inserts is not only a technical decision, but also a cost and performance balance.

If you select correctly, you can:

  • extend mold life
  • improve part quality
  • reduce maintenance cost

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https://www.fentormold.com