Welder in protective gear sparks bright blue welding on a metal table inside an industrial workshop, machines and gas cylinders nearby.

What Welding Process Should I Use for A36 vs Stainless?

Choosing the right welding process for A36 carbon steel and stainless steel is crucial for achieving strong, reliable, and corrosion-resistant joints.

Whether you are fabricating structural frames, repairing equipment, or joining dissimilar metals, understanding the properties of these materials and the best welding methods will help you avoid common pitfalls and ensure high-quality results.

This comprehensive guide explores the differences between A36 and stainless steel, compares the most suitable welding processes, addresses the challenges of welding these metals (individually and together), and provides expert recommendations and safety tips to help you make the best choice for your project.

Understanding A36 Carbon Steel and Stainless Steel

1) A36 Carbon Steel: Properties and Applications

A36 is a widely used low-carbon structural steel, prized for its excellent weldability, ductility, and affordability.

Its typical chemical composition includes 0.25–0.29% carbon, with small amounts of manganese, phosphorus, sulfur, and silicon.

A36 carbon steel I-beam and flat plate, showing the slightly matte, gray surface texture typical of mild steel

Key mechanical properties include a minimum yield strength of 36,000 psi (250 MPa) and an ultimate tensile strength of 58,000–80,000 psi (400–550 MPa).

A36 is easy to form, machine, and weld, making it ideal for building frames, bridges, machinery, and general fabrication. However, it lacks significant corrosion resistance and often requires protective coatings for outdoor use.

2) Stainless Steel: Types and Properties

Stainless steel is a family of iron alloys containing at least 10.5% chromium, which provides excellent corrosion resistance. The most common types include:

  1. Austenitic (e.g., 304, 316): Non-magnetic, highly corrosion-resistant, and easily weldable. Used in food processing, chemical, and marine applications.
  2. Ferritic: Magnetic, good corrosion resistance, and higher thermal conductivity.
  3. Martensitic: Can be hardened by heat treatment, used for cutlery and tools.
  4. Duplex: Combines austenitic and ferritic properties for high strength and corrosion resistance.
stainless steel samples, each labeled as austenitic (304, 316), ferritic, martensitic, and duplex

Stainless steels are generally more expensive than carbon steels but offer superior durability and performance in harsh environments.

Overview of Welding Processes

Selecting the right welding process depends on the material, thickness, application, and desired weld quality. Here are the most common methods for A36 and stainless steel:

1) MIG Welding (GMAW)

  • Description: Uses a continuously fed wire electrode and shielding gas (argon, CO₂, or mix).
  • Advantages: Fast, easy to learn, produces clean welds, and is highly productive for both A36 and stainless steel.
  • Limitations: Requires clean surfaces and is sensitive to wind (not ideal for outdoor use. 
MIG welding torch on a steel plate, with a visible spool of wire feeding into the gun. Bright, controlled sparks and a clear shielding gas plume are present

2) TIG Welding (GTAW)

  • Description: Uses a non-consumable tungsten electrode and inert gas (usually argon) for precise, high-quality welds.
  • Advantages: Produces the cleanest, most precise welds ideal for thin materials and critical joints, especially in stainless steel.
  • Limitations: Slower, requires more skill, and is less efficient for thick sections. 
TIG welding process on a stainless steel sheet. The welder’s gloved hands are steady, holding a tungsten electrode torch in one hand and a filler rod in the other.

3) Stick Welding (SMAW)

  • Description: Uses a consumable flux-coated electrode, creating its own shielding gas and slag.
  • Advantages: Versatile, works on dirty/rusty metal, suitable for outdoor and fieldwork, and has low equipment costs.
  • Limitations: Slower, more spatter, and requires post-weld cleanup.
A rugged, outdoor scene with a welder using a stick welding electrode on a rusty steel beam.

4) Flux-Cored Arc Welding (FCAW)

  • Description: Uses a tubular wire filled with flux, can be self-shielded or use external gas.
  • Advantages: High deposition rates, suitable for thick materials and outdoor use, tolerant of dirty surfaces.
  • Limitations: More fumes and slag, less suitable for thin materials.
welder using a flux-cored arc welding gun on a thick steel plate.

Best Welding Processes for Stainless Steel

Stainless steel requires careful process selection to maintain corrosion resistance and avoid defects:

  • TIG Welding: Preferred for thin, critical, or decorative welds due to its precision and clean results.
  • MIG Welding: Suitable for thicker sections and high-productivity environments; easier to learn than TIG.
  • Stick Welding: Used for outdoor or fieldwork, but welds may be less visually appealing.
  • Flux-Core Welding: Used for heavy-duty or outdoor applications, but less common for stainless steel.

Welding A36 to Stainless Steel: Challenges and Solutions

Welding A36 carbon steel to stainless steel (such as 304 or 316) is common in fabrication but presents unique challenges

Key Challenges

  • Metallurgical Incompatibility: Different chemical compositions can create brittle or weak welds.
  • Thermal Expansion Differences: Stainless steel expands more than carbon steel, causing distortion.
  • Heat Input and Sensitization: Excessive heat can reduce stainless steel’s corrosion resistance.
  • Weld Cracking: Over-dilution from carbon steel can increase cracking risk.
  • Corrosion Issues: Cross-contamination can accelerate corrosion at the weld. 

Solutions and Best Practices

  • Filler Metal Selection: Use a high-alloy filler like E309 or ER309L, designed for dissimilar metal welding.
  • Joint Preparation: Bevel thick sections, maintain proper fit-up, and clean both metals thoroughly.
  • Heat Control: Minimize heat input, use controlled passes, and monitor interpass temperatures.
  • Tool Segregation: Use separate tools for stainless and carbon steel to prevent contamination.
  • Post-Weld Cleaning: Clean welds thoroughly and consider protective coatings for the carbon steel side.

Safety Considerations

Welding A36 and stainless steel involves several safety risks

  1. Toxic Fumes: Stainless steel welding produces hazardous fumes (hexavalent chromium, nickel, manganese). Use local exhaust ventilation and appropriate respirators.
  2. UV Radiation: Protect skin and eyes with proper PPE (welding helmet, gloves, flame-resistant clothing).
  3. Electric Shock: Inspect equipment, keep work areas dry, and follow electrical safety protocols.
  4. Fire Hazards: Remove flammable materials, keep fire extinguishers nearby.
  5. Physical Injuries: Use proper lifting techniques and handle sharp edges with care.
  6. Noise: Use hearing protection during grinding and welding operations.

Always follow OSHA and local safety regulations, provide regular training, and maintain a clean, organized workspace.

Conclusion

Selecting the right welding process for A36 carbon steel and stainless steel depends on your project’s requirements, material thickness, desired weld quality, and working environment.

MIG and Stick welding are excellent for A36, while TIG and MIG are best for stainless steel. When joining A36 to stainless, use a high-alloy filler, control heat input, and follow strict cleanliness protocols to ensure strong, corrosion-resistant welds.

Always prioritize safety and follow industry best practices for optimal results.

Frequently Asked Questions (FAQs)

1. Can you weld A36 to stainless steel?

Yes, but it requires special filler metals (like E309/ER309L), careful heat control, and strict cleanliness to avoid weak or corroded joints.

2. What is the best welding process for A36 steel?

MIG and Stick welding are most common for A36 due to their speed, versatility, and ability to handle thick or dirty material.

3. What is the best welding process for stainless steel?

TIG welding is preferred for thin, critical, or decorative welds; MIG is suitable for thicker sections and higher productivity.

4. How do you prevent corrosion when welding A36 to stainless?

Use the correct filler metal, segregate tools, clean surfaces thoroughly, and consider post-weld cleaning and protective coatings.

Back to blog