Can you weld 304 SS to mild steel?

Why Welding SA 240 GR 304 to Mild Steel is Feasible

SA 240 GR 304 is an austenitic stainless steel with excellent corrosion resistance, SS 304 non magnetic properties, and a SA 240 GR 304 density of 8.00 g/cm³, making it ideal for applications like plat stainless 304 and SA 240 GR 304 pipe. Mild steel, typically a low-carbon steel (e.g., A36 or S275), lacks the corrosion resistance of stainless but is cost-effective and strong. Welding these dissimilar metals is common in industries like construction and manufacturing, where corrosion resistance and structural strength are both needed. However, differences in thermal expansion, corrosion behavior, and metallurgy require specific techniques.

Gangsteel’s sa 240 gr 304 plates are designed for reliable welding performance.

Challenges in Welding SA 240 GR 304 to Mild Steel

• Thermal Expansion: SA 240 GR 304 has a higher coefficient of thermal expansion (17.2 × 10⁻⁶/K) than mild steel (~12 ×10⁻⁶/K), which can cause distortion or residual stresses.
• Corrosion Risks: The mild steel side is prone to rust, potentially affecting the joint unless protected (e.g., by coatings).
• Metallurgical Differences: Austenitic 304 and ferritic mild steel have different crystal structures, requiring a compatible filler metal to bridge the gap.
• Dilution: Mixing of the base metals in the weld pool can alter properties, necessitating a filler that balances both materials.

Recommended Filler Metals

To achieve a strong, corrosion-resistant weld, the filler metal must accommodate both SA 240 GR 304 and mild steel. The most commonly recommended filler metals are:

• ER309L (TIG/MIG Welding):
  • Composition: ~23% Cr, 13% Ni, ≤0.03% C.
  • Benefits: High alloy content compensates for dilution, ensuring corrosion resistance and strength. Maintains SS 304 non magnetic properties in the weld zone.
  • Use: Ideal for TIG (GTAW) or MIG (GMAW) welding of plat SS 304 3mm or thicker plates to mild steel.
• E309L (Stick Welding):
  • Composition: Similar to ER309L, with flux coating for SMAW.
  • Benefits: Suitable for field welding, providing robust joints for structural applications.
• Alternative: ER308L can be used for less critical applications, but ER309L is preferred for its higher chromium and nickel content, which better handles dissimilar metal welds.

For welding SA 240 GR 304L to mild steel, ER309L remains the top choice due to its low carbon content. Explore our sa 240 gr 304l for low-carbon options.

Best Practices for Welding SA 240 GR 304 to Mild Steel

To ensure a high-quality weld:

• Surface Preparation: Clean both materials thoroughly to remove rust, oil, or contaminants. Use acetone or a wire brush for SA 240 GR 304 and grind mild steel to remove mill scale.
• Welding Process:
  • TIG (GTAW): Preferred for precision and control, especially for thin plates like plate 2 mm SUS 304.
  • MIG (GMAW): Faster for thicker sections or SA 240 GR 304 pipe.
  • Stick (DMAW): Suitable for outdoor or structural welds.
• Shielding Gas: Use argon or argon-helium mixes for TIG/MIG to prevent oxidation and maintain SS 304 non magnetic properties.
• Heat Control: Keep heat input low (e.g., 0.5-2.0 kJ/mm) and interpass temperatures below 150°C to minimize distortion and maintain corrosion resistance.
• Weld Positioning: Favor the stainless steel side when applying the filler to ensure better corrosion resistance in the weld zone.
• Post-Weld Treatment:
  • Passivate the stainless side with nitric acid to restore the oxide layer.
  • Apply protective coatings (e.g., paint or galvanizing) to the mild steel side to prevent rust.

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

Applications of SA 240 GR 304 to Mild Steel Welds

Welding SA 240 GR 304 to mild steel is common in:

• Construction: Joining stainless cladding to mild steel frameworks for aesthetic and corrosion-resistant structures.
• Piping Systems: Combining SA 240 GR 304 pipe with mild steel components in mixed-material pipelines.
• Food Processing: Attaching stainless equipment to mild steel supports, balancing cost and hygiene.
• Automotive: Fabricating exhaust systems or structural parts requiring corrosion resistance and strength.

Gangsteel offers competitive SS 304 plate price options for such applications. For harsher environments, consider our sa 240 gr 316l.

Comparing with Other Grades

• SA 240 GR 304L: Preferred for welding to mild steel due to lower carbon (≤0.03%), reducing sensitization risks. ER309L remains the filler choice.
• SA 240 GR 316: Offers better pitting resistance for welds in chloride environments but requires ER316L or ER309L fillers, increasing SS 304 steel price.
• SA 240 GR 304H: Less suitable for dissimilar welds due to higher carbon content. See sa 240 gr 304h.

For high-temperature dissimilar welds, explore our sa 240 gr 321.

Why Choose Gangsteel?

Gangsteel supplies certified SA 240 GR 304 plates optimized for welding to mild steel, 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.