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Ejector Pin Material Comparison
Materials covered
H13(SKD61), SKH‑51(M2), 65Mn, 38CrMoAl(SACM645 /1.8509)
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- General ejector pins overview
- Slender long ejector pin
- Large‑diameter nitrided ejector sleeve
- Die‑casting mold ejector pins
Material Comparison Table
| Material | Heat Treatment | Core Hardness | Surface Hardness | Key Features | Application Scenarios | Important Notes |
|---|---|---|---|---|---|---|
| H13 (SKD61, 4Cr5MoSiV1) | Quench & Temper; optional nitriding | HRC48‑52 | HRC48‑52 (HV 500‑550); higher after nitriding | Excellent toughness, thermal fatigue resistance, good bending resistance, universal grade | General plastic injection molds, slender long ejector pins, aluminum die‑casting molds, ABS / PP / PC materials | Most widely‑used standard ejector pin material. Suitable for high L/D ratio slender pins. Nitriding can further improve surface wear performance. |
| SKH‑51 (M2, W6Mo5Cr4V2) | Quench & Temper | HRC60‑64 | HRC60‑64 | Ultra‑high wear resistance; high hardness; relatively brittle | High‑volume production molds, plastic filled with glass fiber, abrasive molding compounds | Not recommended for extremely slender pins, risk of breakage under heavy impact. Higher cost than H13. |
| 65Mn | Quench & Temper | HRC42‑48 | HRC42‑48 | Low‑cost spring steel, ordinary wear resistance | Short & thick low‑demand ejector pins, non‑critical ejection positions | Economical option. Poor wear resistance. Not for glass‑filled material, slender pins or die‑casting conditions. |
| 38CrMoAl (SACM645, 1.8509 /41CrAlMo7‑4) | Tempering + Gas Nitriding | HRC28‑35 | HV900‑1100 (nitrided layer) | Superb anti‑galling, anti‑wear, low distortion after nitriding | Large‑diameter ejector pins & ejector sleeves (≥Φ10mm), thermoset molds, DIN1530 nitrided custom parts | Not fit for slender long pins, easy bending. Not for Al die‑casting; nitride layer may peel under thermal shock. Mostly custom‑made, few stock items. |
Detailed Description
1. H13 (SKD61)
H13 / SKD61 is the dominant universal ejector‑pin material for mold industry. It balances toughness, heat resistance and mechanical strength. It performs well for long thin ejector pins and aluminum die‑casting environment. Surface nitriding treatment can enhance wear resistance if facing slightly abrasive plastics.
2. SKH‑51 (M2 High‑Speed Steel)
M2 high‑speed steel delivers top‑level wear resistance among these four grades. It is selected for mass‑production molds with glass‑filled or fire‑retardant plastics. Due to intrinsic brittleness, avoid using for very slim ejector pins which bear repeated bending stress. Unit price is significantly higher than H13.
3. 65Mn Spring Steel
65Mn is a low‑cost spring steel solution only for simple, low‑requirement ejection structures. It cannot sustain abrasive material or long‑time cyclic loading. Never adopt for thin pins or die‑casting tools.
4. 38CrMoAl (SACM645)
38CrMoAl is a specialized nitriding steel. High surface hardness comes from nitriding layer instead of full quenching. Its core hardness remains moderate. It shines for thick ejector pins and sleeves, showing excellent anti‑seize performance. ⚠️ Critical limits:
- Slender pins (high L/D ratio): easy bending because of low core hardness
- Die‑casting application: nitride coating will fail under thermal cycling
- Almost no ready stock, most orders need custom machining plus nitriding heat treatment.
Quick Selection Guide
- General plastic mold, mixed pin sizes including slim pins → H13 / SKD61
- Glass‑fiber filled plastic, high mass production → SKH‑51 (M2)
- Low‑budget, short thick non‑critical pins → 65Mn
- Large‑diameter ejector sleeves / thick pins, need anti‑galling performance → 38CrMoAl (SACM645)
- Aluminum die‑casting mold → H13 / SKD61 (first choice); SKH‑51 for heavy‑duty case
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