The corrosion resistance of stainless steel makes it an attractive choice for many critical tube and pipe applications, including high-purity food and beverage, pharmaceutical, pressure vessel, and petrochemical uses. However, the material doesn’t dissipate heat as well as mild steel or aluminum do, and poor welding practices can decrease its ability to resist corrosion. Applying too much heat input and using the wrong filler metal are two culprits.

Following some best practices for stainless steel welding can help improve results and ensure that the metal maintains its corrosion resistance. Furthermore, upgrading the welding process can deliver productivity benefits without impacting quality.

Tip 1: Select a low-carbon filler metal

Look for filler metals with an “L” designation, such as ER308L, because these provide a lower maximum carbon content, which helps retain corrosion resistance in low-carbon stainless alloys. Welding a low-carbon base material with a standard filler metal can increase the carbon content of the weld joint and thereby increase the risk of corrosion. Avoid filler metals with an “H” designation, since these provide higher carbon content designed for applications that require greater strength at high temperatures.

Tip 2: Pay attention to weld preparation and proper fit-up

Because stainless steel is so sensitive to heat input, joint preparation and proper fit-up play key roles in controlling the heat to maintain the material’s properties.

Tip 3: Control sensitization with temperatures and filler metal

In stainless steel, sensitization is the primary cause of the loss of corrosion resistance. It can occur when weld temperatures and cooling rates fluctuate too much, changing the microstructure of the material.

 

Tip 4: Understand how shielding gas impacts corrosion resistance

Using gas tungsten arc welding (GTAW) for the root pass is the traditional method for welding stainless steel tube and pipe. This typically requires a back purge of argon gas to help prevent oxidation on the back side of the weld. However, using wire welding processes is becoming more common with stainless steel tube and pipe. In these applications, it’s important to understand how the various shielding gases affect the material’s corrosion resistance.

Tip 5: Consider different processes and waveforms