What is Stainless Steel Welding?

Stainless steel welding is a specialized fabrication process used to join pieces of stainless steel through the application of heat, pressure, or both. Unlike standard carbon steel, stainless steel contains a minimum of 10.5% chromium, which forms a passive “Chromium Oxide” layer on the surface. This invisible layer is what grants stainless steel its legendary corrosion resistance.

However, this characteristic also makes welding challenging. Stainless steel retains heat more effectively than other metals (low thermal conductivity but high thermal expansion), making it prone to distortion (warping) and heat tint (oxidation discoloration) if not managed correctly . At Flow Wing Metal, we master the thermal dynamics required to fuse stainless steel without compromising its structural integrity or anticorrosive properties.

Types of Stainless Steel Welding Processes:

Selecting the right process depends on the thickness of the material, the required aesthetics, and the structural demands of the project. Flow Wing Metal utilizes a range of processes, with a primary focus on precision:

1. GTAW (Gas Tungsten Arc Welding) / TIG (Tungsten Inert Gas):

Considered the gold standard for stainless steel welding, TIG welding uses a nonconsumable tungsten electrode and an inert gas shield (Argon/Helium). This method offers superior arc control and low heat input, producing exceptionally clean, spatterfree, and often “stack of dimes” aesthetic welds.

Flow Wing Advantage: Ideal for thinwall tubing, sanitary piping, and architectural railings where appearance is paramount.

2. GMAW (Gas Metal Arc Welding) / MIG (Metal Inert Gas):

This semiautomatic process uses a continuously fed consumable wire. It is significantly faster than TIG, making it economically viable for largescale industrial fabrication and thick plate welding in stainless steel welding applications.

Flow Wing Advantage: High deposition rates for structural components and heavy fabrications.

3. SMAW (Shielded Metal Arc Welding) / Stick Welding:

A manual process using a fluxcoated electrode. It is highly portable and versatile, making it the best choice for outdoor field repairs, construction sites, or heavy equipment where wind would disrupt gas shielding in stainless steel welding environments.

Material Mastery: Grades & Surface Treatments for Stainless Steel Welding

Stainless Steel Grades We Weld:

Understanding the metallurgy is key to a perfect weld. Flow Wing Metal engineers select specific filler rods and gas blends for each alloy to prevent “sensitization” (carbide precipitation) and cracking.

Austenitic (304, 304L, 316, 316L): The most common grades. 316L (Low Carbon) is the standard for pharmaceutical and marine welding due to its excellent resistance to chlorides and its ability to resist intergranular corrosion postweld.

Ferritic (430, 409): Magnetic and resistant to stress corrosion cracking, though they have limited ductility.

Martensitic (410, 420): Hard and strong, often used for wearresistant applications.

Duplex (2205): Twice as strong as austenitic grades; requires precise heat control to maintain the ferrite/austenite balance.

Surface Finishing & PostWeld Treatment:

A weld is not complete until the surface is restored. Raw welding destroys the protective oxide layer, turning the weld area blue or black (heat tint). At Flow Wing Metal, we finish every component to last.

1. Mechanical Cleaning:

We use dedicated stainless steel brushes and abrasive wheels (never contaminated by carbon steel) to remove heavy slag and begin the smoothing process.

2. Chemical Pickling & Passivation:

This is our standard for highcorrosion resistance. We apply specialized finishing chemicals (pickling gels/sprays) that chemically dissolve the “chromiumdepleted” layer and the embedded iron particles. This process does two things:

• Removes heat tint from the Stainless Steel Welding joint.

• Restores the uniform passive layer, ensuring the material is “stainless” again at the Stainless Steel Welding joint.

Research indicates that pickling is the only method that guarantees complete corrosion resistance on welds.

3. Electrolytic Cleaning (Weld Cleaning):

For finished products where aesthetics are critical (e.g., brewery tanks or elevator doors), we use electrolytic processes. A carbon fiber brush soaked in electrolyte conducts a current that lifts heat tint away without aggressive acids or abrasives, leaving a bright, shiny, and repassivated finish instantly.

Successful Case: Flow Wing Marine & Pharma Solutions

Kunde: Nordic Marine Systems (Confidential Project)

Industrie: Offshore Pharmaceutical Transport (Chemical Tankers)

Herausforderung: The client required 500 meters of 316L stainless steel piping (Schedule 10) for a highpurity chemical transfer system. The key requirements were:

• Zero corrosion allowance for 15 years.

• Smooth internal “bore” welds with no crevices for bacterial or chemical adhesion (sanitary standard).

• 100% Xray inspection with zero tungsten inclusions.

The Flow Wing Stainless Steel Welding Execution:

Phase 1: Precision Preparation

We utilized CNC beveling machines to ensure perfect joint alignment. All pipes were cleaned with acetone to remove oils, and a dedicated “clean room” welding bay was used to prevent carbon contamination.

Phase 2: The Welding Process (Orbital & Manual GTAW)

Process: GTAW (TIG) stainless steel welding with 100% Argon backing gas (purged inside the pipe).

Filler: ER316L (Low Carbon to maintain corrosion resistance).

Technique: Pulsed TIG stainless steel welding to reduce heat input by 30% compared to standard TIG, drastically minimizing distortion on the thin Schedule 10 pipe.

Inert Gas: We utilized a trailing shield cup to protect the hot weld zone from oxygen as it cooled, preserving the metallic color (silver/gold) and preventing “sugaring” (oxidation on the back of the weld).

Phase 3: PostWeld Restoration

After stainless steel welding, the heat tint was removed using a combination of electrolytic cleaning for the exterior (for a brushed 4 finish) and chemical pickling for the interior bore. This restored the passive layer to an average CPT (Critical Pitting Temperature) value exceeding the parent metal.

Phase 4: Quality Assurance

Visual Inspection: All welds exhibited a uniform silver/straw color (indicating perfect gas coverage).

Ferrite Testing: Verified to ensure the weld metal microstructure matched the 316L base metal, preventing embrittlement.

Pressure Test: The system held test pressure at 150% of operational capacity without a single pinhole leak.

The Result: Flow Wing Metal delivered the piping modules two weeks ahead of schedule. The client reported a 40% reduction in postfabrication cleanup time due to our “weldready” finish. The cargo tanks passed the IMO (International Maritime Organization) coating standards without requiring rewelding of any joints.

Why Choose Strömungsflügel Metal?

AntiCorrosion Assurance: We do not just weld; we passivate. We guarantee your welded joint will not rust.

Distortion Control: Our expertise in lowheat input techniques (Pulsed MIG/TIG) ensures your parts remain flat and square.

ContaminationFree: We strictly segregate carbon steel tools from stainless steel fabrication areas.