In the field of Investment Casting, SS 304, 316, and 316L are the three most utilized materials at CDL LOST WAX CASTING JOINT STOCK COMPANY. These grades account for over 65% of our monthly stainless steel output (total capacity of 60 tons/month).
Choosing the right grade is not just about price; it directly impacts castability, dimensional accuracy, corrosion resistance, and surface treatment costs. Selecting the wrong grade can increase scrap rates by 10–18% or result in products failing export standards (FDA, HACCP, NSF).
Based on over 5,000 production heats at our ISO 9001:2015 certified facility, this article compares these three grades across 7 critical criteria.
1. Chemical Composition – The Foundation of Difference
| Element | SS 304 | SS 316 | SS 316L |
| Cr (%) | 18–20 | 16–18 | 16–18 |
| Ni (%) | 8–10.5 | 10–14 | 10–14 |
| Mo (%) | – | 2–3 | 2–3 |
| C (%) | $\leq$ 0.08 | $\leq$ 0.08 | $\leq$ 0.030 |
- Key Insight: The 2–3% Molybdenum (Mo) in 316/316L increases chloride corrosion resistance by 3–5 times compared to 304. The low carbon ($\leq$ 0.03%) in 316L prevents sensitization (intergranular corrosion) during the high-temperature casting process.
2. Corrosion Resistance
- SS 304: Good for organic acids and freshwater. Vulnerable to “pitting corrosion” in saline or chloride-rich environments.
- SS 316: Superior resistance to chlorides, sulfuric, and phosphoric acids. Ideal for food, pharma, and marine fittings.
- SS 316L: Equivalent to 316 in corrosion but superior in welding and casting environments as it prevents grain boundary carbide precipitation.
3. Mechanical Properties Post-Casting
| Property | SS 304 | SS 316 | SS 316L |
| Tensile Strength (MPa) | 515–620 | 550–700 | 550–700 |
| Yield Strength (MPa) | 205–310 | 220–290 | 220–290 |
| Elongation (%) | $\geq$ 40 | $\geq$ 40 | $\geq$ 40 |
| Hardness (HB) | 150–180 | 160–190 | 160–190 |
4. Castability in Investment Casting
- Pouring Temperature: All grades at 1580–1600°C.
- Shrinkage:
- 304: 2.3–2.5%
- 316: 2.2–2.4%
- 316L: 2.1–2.3% (Lowest, easiest for dimensional control).
- Fluidity: 316L offers the best fluidity due to Molybdenum stabilizing the molten structure.
- Scrap Rate: 304 is prone to higher inclusion rates compared to 316L.
5. Surface Finish & Post-Cast Aesthetics
All three grades achieve $Ra \leq 3.2$ µm after shot blasting and pickling.
- 316L: Produces the cleanest and most uniform surface after pickling ($HNO_3 + HF$), making it the top choice for FDA/HACCP compliant parts.
6. Comprehensive Cost Analysis
| Material | Raw Material Price Index | Casting & Processing Cost | Recommended Use |
| SS 304 | Base | +0% | Mild environments, no chlorides |
| SS 316 | High | +8–10% | Moderate chloride exposure |
| SS 316L | Very High | +10–12% | Food, Pharma, High-end Marine |
Summary Comparison Table
| Criterion | SS 304 | SS 316 | SS 316L (Highest Rec.) |
| Chloride Resistance | Low | Moderate-High | Highest |
| Sensitization Resistance | Moderate | Good | Excellent |
| Shrinkage & Precision | 2.3–2.5% | 2.2–2.4% | 2.1–2.3% (Best) |
| FDA/HACCP Compliance | Not Rec. | Good | Excellent |
| Relative Cost | Lowest | Moderate | +10–12% |
| Casting Success Rate | 92–95% | 96–97% | 97–99% |
Conclusion
While all three are excellent for Investment Casting, SS 316L is typically the optimal choice due to its superior corrosion resistance, low shrinkage, and hygiene compliance. Choosing 316L can reduce scrap rates to below 3% and offer 10–18% long-term savings by extending component life.
Lostwaxcasting CDL – With 2026-level technology and ISO 9001:2015 controls, we are ready to support you with:
- Free drawing analysis and material recommendation within 24 hours.
- Test casting samples.
- Detailed quotations for 304, 316, and 316L grades.
