Stainless steel is one of the most popular industrial metal materials due to its various advantageous characteristics. One of the best characteristics of stainless steel is its corrosion resistance making it the perfect choice for most critical tube and pipe applications. However, steel does not dissipate heat like other metals such as aluminum or mild steel, and poor metal welding methods will decrease its corrosion-resistant characteristic. For example, applying too much heat input and utilizing inappropriate filler materials are two common mistakes. So, as professional metal welders in Canada, we must help others improve their skills, and with this guide, you can learn welding stainless steel tubing basics.
The following techniques and tips are the best practices for welding stainless steel tubing and pipe and can improve results while ensuring that the metal maintains its beneficial characteristics. Furthermore, upgrading metal welding services can deliver productivity.
If you are new to welding systems, we recommend you reading Metal Welding Guide for Beginners.
Select a Low-Carbon Filler Metal for Welding Stainless Steel Tubing
Selecting filler metal for controlling carbon levels in stainless steel welding is crucial. The filler metal utilized for welding stainless steel tubing and piping enhances the weld properties and meets the client’s requirements.
Remember that you need to look for a filler metal with an “L” designation such as ER308L since they provide lower maximum carbon levels helping the steel retain corrosion-resistant characteristics in low-carbon alloys.
It is crucial to avoid filler metals with an “H” designation since they have higher carbon content and are designed for projects requiring strength at high temperatures.
For welding stainless steel tubing and piping, choosing a filler metal with low trace or tramp elements is crucial. Tramps are residual elements in the raw materials used to make the filler metal which can affect steel’s corrosion resistance characteristic.
Pay Attention to Metal Weld Preparation
Stainless steel is susceptible to heat input. So, joint preparation and proper fit-up are crucial in controlling the heat to maintain steel’s properties.
You need to add more filler metal and hold the welding torch longer in one spot if there are gaps or uneven fit-up between the parts. This will cause heat buildup in the focus point resulting in overheating the part. Poor fit-up can also cause other challenges, such as harder bridging between the gaps. So, for welding stainless steel tubing and piping, you must ensure the fit-up is perfect.
Moreover, cleanness is essential for the stainless steel welding process since minor contaminants or dirt in the joint can reduce the final product’s strength and corrosion resistance characteristics.
Control Sensitization With Temperatures While Welding Stainless Steel Tubing
Sensitization is the primary cause of corrosion resistance reduction in stainless steel products. Sensitization can occur when cooling rates or weld temperatures fluctuate too much.
If you want to prevent sensitization, you need to be precise with selecting the filler metal and controlling heat input. Although it is essential to choose a low-carbon filler for welding stainless steel tubing, carbon is needed to provide strength in some cases.
You can minimize the time that the heat-affected zone and the weld are held at higher temperatures. This will decrease the heat buildup.
Understand How Metal Welding Methods Impact Corrosion Resistance Steel
Using the gas metal arc welding method (GMAW) is the traditional way of welding stainless steel tubing and pipes. However, some of the current metal fabricators use wire welding processes. For the stainless steel welding process, it is crucial to understand how various shielding gases can affect the steel’s corrosion resistance characteristics.
Metal welders use a mixture of argon and oxygen, argon and carbon dioxide, or three-gas mixtures when welding stainless steel tubing with the GMAW method. Using pure argon with GMAW is not recommended.
Consider Using Different Processes for Welding Stainless Steel Pipes and Tubes
Using modified short-circuit GMAW processes for the root pass eradicates the back purge in specific stainless steel applications. Pulsed GMAW can follow the RMD root pass or flux-cored arc metal welding fill and cap passes, saving time and money compared to the GTAW stainless steel welding method.
The pulsed GMAW welding stainless steel tubing process creates a shorter arc length, narrower arc cone, and lower heat input level than conventional spray pulse transfer. Since this stainless steel welding process is a closed-loop, arc wandering and deviations in tip-to-work distances are eliminated. This delivers more straightforward welding pool control for in-position and out-of-position stainless steel welding.