Can you weld 304 and 316 together?

Why Welding SA 240 GR 304 and SA 240 GR 316 is Feasible

SA 240 GR 304 (ASTM A240 304, 1.4301) and SA 240 GR 316 (ASTM A240 316, 1.4401) are austenitic stainless steels with similar SS 304 non magnetic properties and a shared SA 240 GR 304 density of 8.00 g/cm³. The key difference is 316’s 2-3% molybdenum content, which enhances pitting and crevice corrosion resistance in chloride environments. Welding these grades together is common in applications requiring a balance of cost (304 is cheaper) and corrosion resistance (316 excels in harsh conditions). Gangsteel’s sa 240 gr 304 and sa 240 gr 316 plates are designed for reliable welding.

Challenges in Welding SA 240 GR 304 to SA 240 GR 316

• Compositional Differences: 316’s molybdenum and higher nickel (10-14% vs. 8-10.5% in 304) require a filler metal that balances both alloys’ properties.
• Corrosion Resistance: The weld must maintain 316’s superior resistance to chlorides to avoid compromising the joint in corrosive environments.
• Thermal Expansion: Both grades have similar coefficients (17.2 × 10⁻⁶/K for 304, 16.0 ×10⁻⁶/K for 316), minimizing distortion risks, but heat control is still critical.
• Dilution: Mixing of 304 and 316 in the weld pool can dilute molybdenum, affecting corrosion resistance unless the right filler is used.

Recommended Filler Metals

To achieve a strong, corrosion-resistant weld between SA 240 GR 304 and SA 240 GR 316, the filler metal should match or exceed 316’s corrosion resistance. The most commonly recommended filler metals are:

• ER316L (TIG/MIG Welding):
  • Composition: ~18% Cr, 12% Ni, 2-3% Mo, ≤0.03% C.
  • Benefits: Matches 316’s molybdenum content, ensuring pitting resistance in chloride environments. The low carbon minimizes sensitization, maintaining SS 304 non magnetic properties.
  • Use: Ideal for TIG (GTAW) or MIG (GMAW) welding of plat SS 304 3mm or SA 240 GR 304 pipe to 316 plates.
• E316L (Stick Welding):
  • Composition: Similar to ER316L, with flux coating for SMAW.
  • Benefits: Suitable for thicker plates or field welding, providing robust joints.
• Alternative: ER309L (~23% Cr, 13% Ni, ≤0.03% C) can be used for dissimilar stainless welds, offering higher alloy content to compensate for dilution. It’s also suitable for welding 304 to mild steel, as noted in our sa 240 gr 304 welding guide.

For low-carbon variants, use ER316L when welding SA 240 GR 304L to SA 240 GR 316L. Explore our sa 240 gr 316l and sa 240 gr 304l.

Best Practices for Welding SA 240 GR 304 to SA 240 GR 316

To ensure high-quality welds:

• Surface Preparation: Clean both materials to remove contaminants like oil, dirt, or oxides using acetone or a stainless steel wire brush to prevent weld imperfections.
• Welding Process:
  • TIG (GTAW): Preferred for precision, especially for thin plates like plate 2 mm SUS 304 or 316.
  • MIG (GMAW): Suitable for thicker sections or faster production.
  • Stick (SMAW): Effective for structural welds in field conditions.
• Shielding Gas: Use argon or argon-helium mixes for TIG/MIG to prevent oxidation and maintain SS 304 non magnetic properties.
• Heat Control: Maintain low heat input (0.5-2.0 kJ/mm) and interpass temperatures below 150°C to avoid sensitization in 304 and ensure corrosion resistance in 316.
• Post-Weld Treatment: Passivate with nitric acid to restore the chromium oxide layer, enhancing corrosion resistance, especially in chloride-rich environments.

For detailed welding specs, refer to our SS 304 data sheet.

Applications of SA 240 GR 304 to SA 240 GR 316 Welds

Welding these grades together is common in:

• Chemical Processing: Combining 304’s cost-effectiveness with 316’s corrosion resistance for mixed-material vessels.
• Marine Equipment: Using 316 for chloride-exposed parts and 304 for less critical components to optimize SS 304 plate price.
• Food and Pharmaceutical: Joining 304 and 316 for equipment requiring hygiene and localized corrosion resistance.
• Piping Systems: Welding SA 240 GR 304 pipe to 316 components in mixed environments.

For harsher conditions, consider our sa 240 gr 317l.

Comparing with Other Grades

• SA 240 GR 304L/316L: Low-carbon variants reduce sensitization risks, using ER316L filler for similar welds. See sa 240 gr 304l.
• SA 240 GR 304H: Higher carbon makes it less suitable for dissimilar welds compared to 304/316. Explore sa 240 gr 304h.
• SS204 vs SS 304: 304 and 316 outperform 200-series grades in corrosion resistance and weldability.

Why Choose Gangsteel?

Gangsteel supplies certified SA 240 GR 304 and SA 240 GR 316 plates optimized for welding, with competitive SS 304 sheet price and custom sizes like plat stainless 304. Our expertise ensures reliable welds for your projects. For quotes or welding guidance, visit our astm a 240 stainless plate page or email admin@gangsteel.com.