In Investment Casting (Lost Wax Casting), selecting the right stainless steel or cast steel grade does not only determine the final product quality but also directly impacts costs, lead times, and component lifespan. A minor miscalculation can lead to a 15–20% increase in scrap rates, high secondary machining costs, or failure to meet export standards.

At CDL LOST WAX CASTING JOINT STOCK COMPANY (Dong Nai) – an ISO 9001:2015 certified facility with a 60-ton/month capacity – we have synthesized 8 critical considerations based on over 5,000 production heats.

1. Corrosion Resistance – The Primary Criterion

This is the most vital factor for 70% of CDL’s clients.

• Stainless Steel 304: Excellent for mild environments (freshwater, food oils, atmospheric conditions). Not suitable for chloride-rich environments (sea salt, strong cleaning agents).
• Stainless Steel 316/316L: Contains 2–3% Molybdenum (Mo), offering 3–5x better chloride resistance than 304. Ideal for marine, food, and pharmaceutical industries.
• Duplex 2205: Offers the highest corrosion resistance in the stainless group, used for oil, gas, and chemical processing.
• Carbon Steel: Corrodes rapidly without protective coating or plating.

Practical Note: For gas stove components (exposed to acids and heat), CDL recommends 316L over 304 to prevent oxidation within 6–12 months.

2. Evaluation of Mechanical Properties

• Tensile Strength:
  • SS 304: 515–620 MPa
  • SS 316: 550–700 MPa
  • Carbon Steel: 400–600 MPa
  • Alloy Steel 4140 (Heat-treated): 900–1200 MPa
• Hardness: Alloy steels easily achieve HB 200–300 post-heat treatment, making them ideal for wear-resistant parts like gears and shafts.
• Elongation: SS 304/316 exceeds 40%, offering superior impact resistance compared to the 15–25% of carbon steel.

3. Working Temperature and Heat Resistance

• SS 304/316: Withstands continuous heat up to 800–900°C (excellent for gas stoves and kilns).
• Alloy Steel: 600–700°C (post-heat treatment).
• Carbon Steel: Limited to 400–500°C due to rapid oxidation.

4. Shrinkage Analysis and Dimensional Accuracy

Shrinkage is the “No. 1 enemy” of precision:

• SS 304/316: 2.2–2.5% shrinkage.
• Carbon Steel: 1.6–2.0% shrinkage.
• Alloy Steel: 1.3–1.7% shrinkage.

CDL Solution: We apply precise shrinkage allowances in CAD design and use Moldflow to predict deformation, ensuring stable tolerances of $\pm$0.08 mm.

5. Comprehensive Cost Analysis (Material + Casting + Machining)

Saving Tip: If chloride resistance is not required, using SS 304 instead of 316 saves 15–18% in total costs.

6. Castability & Flowability

• SS 316L: Offers the best flowability (due to Ni and Mo), ideal for pouring complex, thin-walled geometries.
• Carbon Steel: Easy to cast but prone to localized shrinkage.
• Alloy Steel: Requires 20–30°C higher pouring temperatures and larger risers.

7. Surface Finish and Hygiene Requirements

• Food/Pharma: Requires $Ra \leq 3.2$ µm and FDA-compliant acid pickling ($HNO_3 + HF$). SS 316L is the industry standard here.
• CDL Process: Our 4-step closed-loop cleaning (Acid $\rightarrow$ Pressure Rinse $\rightarrow$ 100°C Drying) ensures zero residual acid.

8. Compliance with Industry Standards

• FDA / HACCP / NSF: SS 316L required.
• IATF 16949 (Automotive): Heat-treated Alloy Steel 4140.
• ABS / DNV (Marine): Duplex or 316L Stainless Steel.

Quick 8-Point Checklist for Engineers:

1. Corrosive environment? $\rightarrow$ 316L/Duplex
2. High mechanical stress? $\rightarrow$ Alloy Steel
3. Temperature >600°C? $\rightarrow$ SS 316
4. Tolerance $\pm$0.1 mm required? $\rightarrow$ SS 304/316
5. Limited budget? $\rightarrow$ Carbon Steel + Surface Coating
6. Complex, thin-walled design? $\rightarrow$ SS 316L
7. Food-grade application? $\rightarrow$ 316L + FDA Finishing
8. Export requirements? $\rightarrow$ Verify MTC (Material Test Certificate)

Conclusion

Selecting the right stainless or cast steel grade is not about choosing the most expensive material, but the most suitable one based on these 8 criteria. A correct decision can save 15–25% in costs and increase component lifespan by 3–5 times.

Lostwaxcasting CDL – With decades of experience and ISO 9001:2015 systems, our technical team is ready to analyze your drawings and recommend the optimal material within 24 hours.