How To Set Up A Tig Welder For Stainless Steel
Last Updated on 2 mins by Peter Jacobs
Tungsten Inert Gas (TIG) welding, one of the most intricate and sophisticated welding techniques, is particularly vital when working with materials renowned for their delicate nature, such as stainless steel. Stainless steel, with its corrosion-resistant properties and commendable strength, is a popular choice in many industrial applications.
However, its distinct composition demands a specific approach in welding to ensure optimal strength and aesthetic finish. Thus, understanding how to set up a TIG welder for stainless steel becomes an indispensable skill for welding professionals and enthusiasts alike. The nuances in selecting the right tungsten electrode, appropriate shielding gas, and maintaining the correct amperage can dramatically affect the welding outcome. As industries continue to prioritize the durability and appearance of their stainless steel products, mastering the setup of a TIG welder for this material can be seen as an art form, combining the technical know-how with the finesse of execution. Here is the guide on how to set up a Tig welder for stainless steel
To Set Up A Tig Welder For SS
1. Selection of the Right Tungsten Electrode
There are several types of tungsten electrodes, but for stainless steel, pure tungsten or 2% thoriated are the most recommended. Their electrical conductivity and heat resistance properties suit the characteristics of stainless steel. When sharpening, always grind longitudinally, never circumferentially. This ensures better arc stability and control during welding.
2. Choose the Appropriate Gas
Argon’s inert properties make it the best shielding gas for TIG welding, especially with stainless steel. A consistent flow rate between 15-20 cfh is crucial to keep out atmospheric contaminants like oxygen and nitrogen, which can adversely affect the weld’s quality.
3. Welding Polarity
Stainless steel requires DCEN (Direct Current Electrode Negative) polarity. This setup provides maximum heat at the workpiece, ensuring deep penetration and reducing potential defects like porosity or lack of fusion.
Also read: What Shade Lens for Mig Welding
4. Filler Metal Selection
308L is the standard filler for 304 stainless steel. The ‘L’ stands for low carbon, which reduces the risk of corrosion in the weld. Always ensure the filler metal matches the base material’s composition. This harmony ensures optimal strength and corrosion resistance.
5. Setting the Amperage
The amperage setting corresponds to the thickness of the metal. Typically, a ratio of 1 amp per 0.001-inch thickness is recommended. However, factors like joint configuration, position, and tungsten size can also influence the optimal amperage.
6. Clean the Base Metal
Any oil, rust, or oxide layers can negatively impact weld quality. Using a dedicated stainless steel brush, rigorously clean the work area. Ensure the brush hasn’t been used on other metals to prevent cross-contamination.
7. Torch and Cup Selection
The torch’s cup size determines the shielding gas’s spread. While smaller cups might suffice for intricate welds, broader, more exposed welds may need larger cups for adequate gas coverage. Remember, proper coverage ensures a cleaner, more consistent weld.
Also read: What is the 7018 Welding Rod Used for
8. Postflow Time
After completing the weld, the tungsten and weld area remain hot and vulnerable to atmospheric contamination. Setting a postflow time of around 6-10 seconds ensures they stay shielded with argon until they’ve cooled sufficiently.
9. Tack Welds First
To ensure stability during welding, place small tack welds at intervals along the joint. This process ensures proper alignment, reduces distortion, and offers a guideline for the main welding process.
Also read: What is Tack Welding
10. Welding Technique
Mastery comes with practice. Focus on maintaining a tight, consistent arc length. The angle between the torch and workpiece, typically around 20-25 degrees, can affect penetration and bead profile. A steady hand, consistent travel speed, and rhythmic addition of filler metal lead to aesthetically pleasing and structurally sound welds.
In essence, the precision in setting up a TIG welder directly translates to excellence in welding outcomes, especially with challenging materials like stainless steel. Always prioritize safety, and remember that each weld is a step towards perfection.
Also read: What is Spot Welding
What’s Challenging About Welding Stainless Steel?
Stainless steel, with its gleaming appearance and resistance to rust, is a favorite in various industries, from kitchenware to architecture. But when it comes to fusing pieces together, this metal has a distinct temperament. Welding stainless steel isn’t quite the same as welding more common materials. Here’s a deeper dive into the challenges:
1. Thermal Expansion and Contraction
Stainless steel’s higher coefficient of thermal expansion, compared to carbon steel, causes it to expand more when exposed to heat. This differential expansion, combined with its relatively lower heat conductivity, can create problems. On cooling, the material undergoes rapid contraction. This behavior, especially in thinner sections or intricate geometries, can result in warping, distortion, and residual stresses within the weld and heat-affected zones.
This is a microstructural change occurring in some stainless steels. When exposed to temperatures between 500°C and 850°C, chromium carbides can form around grain boundaries, depleting the surrounding area of chromium. This area becomes susceptible to intergranular corrosion. The phenomenon, termed sensitization, undermines the primary advantage of stainless steel’s corrosion resistance.
3. Discoloration and Oxidation
Stainless steel is particularly prone to oxidation when subjected to high temperatures without proper shielding. The resulting oxidation can lead to a chromatic discoloration on the surface, manifesting as a rainbow or blue hue. This might be acceptable, or even desirable in some artistic applications, but in industrial settings, it’s often considered a defect, indicating a thin oxide layer that could compromise corrosion resistance.
4. Requirement of Back Purging
The welding of closed sections, like tubes or pipes, presents another hurdle. The interior, or backside of the weld, is just as prone to oxidation. To combat this, back purging is employed. An inert gas, typically argon, is introduced inside the section to shield the back of the weld. Without back purging, the inner side of the weld can become heavily oxidized, leading to what’s colloquially termed “sugar” due to its granulated appearance. This not only affects appearance but also drastically reduces corrosion resistance and weld strength.
5. Gas Tungsten Arc Welding (GTAW/TIG) Sensitivity
TIG welding is frequently the method of choice for stainless steel due to its precision and cleanliness. However, it’s a sensitive process. Any contamination—whether it originates from the filler metal, the base metal, ambient conditions, or even oils from the welder’s skin—can introduce defects into the weld. Such impurities can lead to porosity, inclusions, or lack of fusion, all of which compromise the integrity of the weld.
6. Difficulty in Visual Inspection
Stainless steel, with its shiny surface, can sometimes mask defects. Small imperfections like microcracks, subsurface discontinuities, or undercuts can be especially challenging to discern. This calls for rigorous inspection methods, often employing tools like ultrasonic testers or dye penetrants to ensure weld quality.
Tips To Use A TIG Welder For Stainless Steel For A Better Result
TIG welding stainless steel requires a meticulous approach, blending both art and science. Here’s a comprehensive exploration from three unique viewpoints the Practical Welder, the Aesthete, and the Longevity-focused Professional.
From the Lens of a Practical Welder
1. Workpiece Preparation
In the world of welding, clean surfaces are paramount. Any lingering contaminants can drastically affect weld quality. Before starting, use a specialized stainless steel brush to meticulously scrub away any residues, oils, or oxides. This simple act lays the foundation for a successful weld, ensuring a seamless fusion between base and filler metals. Avoid using brushes or tools that have been used on other metals, as they can introduce contaminants.
2. Electrode Choice
The electrode is your conduit for creating a stable, effective arc. While the classic choices have been pure tungsten or 2% thoriated, the evolving world of welding has seen lanthanide versions becoming increasingly popular. The right choice will depend on the specific project and personal preference, but always ensure the electrode is sharply pointed for optimum arc control.
3. Master Torch Control
The torch is an extension of the welder’s hand. Its movement dictates the bead’s formation and penetration depth. Consistent torch angles and steady hand movements are essential. Additionally, maintaining a short and focused arc can ensure deep penetration and reduced chances of weld puddling.
From an Aesthete’s Perspective:
4. Heat Control for Appearance
Stainless steel’s beauty can be marred by excessive heat, leading to discoloration. The pulsing technique is a boon for those concerned about aesthetics. This method not only reduces total heat input but ensures even distribution, helping maintain the material’s natural luster. Proper cooling methods post-weld can further preserve the metal’s pristine appearance.
5. Smooth, Even Beads
An aesthetically pleasing weld bead is the mark of a master welder. Achieving this requires a rhythmic coordination between adding filler material and moving the torch. A consistent rhythm and speed can produce evenly spaced ripples, creating a weld that’s as beautiful as it is strong.
6. Finish with Flair
A weld’s appearance post-process speaks volumes. After completing the welding, using pickling paste can help remove any tarnish or oxidation. This step is crucial to restoring the stainless steel’s signature shine, making your work stand out.
With an Eye on Longevity:
7. Shielding Gas Flow
The invisible shield of argon gas plays a crucial role in the weld’s future integrity. A consistent, optimal gas flow ensures the molten weld pool remains uncontaminated. This protection translates to a weld-free from potential weak spots like porosity or inclusions, which could compromise the joint’s longevity.
8. Match Filler to Base Metal
Metals have complex structures and compositions. For a lasting weld, the filler material should have a composition that complements the base metal. This synergy ensures that the weld area doesn’t become a site of future vulnerabilities, such as corrosion or cracking.
9. Back Purging for Tubular Structures
Tubular structures present a unique challenge. Their interiors, unless protected, can oxidize during welding. Back purging introduces an inert gas inside the tube, safeguarding the interior weld zone. This process ensures the inside remains as robust and corrosion-resistant as the exterior.
10. Regular Inspections
Welding is a journey, and regularly checking your progress ensures you stay on the right path. Periodic inspections, whether visual or using specialized tools, can catch inconsistencies or defects early on. Correcting these in real-time ensures the final weld stands the test of time.
TIG welding stainless steel elegantly melds the worlds of craftsmanship, precision, and technical prowess. While each perspective be it the pragmatism of a hands-on welder, the discerning eye of an aesthete or the foresight of a longevity-focused professional offers its unique lens, they collectively converge on a singular truth: Mastery in welding isn’t just about joining metals; it’s about understanding the nuance of the material, respecting its characteristics, and using that knowledge to create work of both form and function. As welders harness these insights, they not only elevate the quality of their work but also the art and science of welding itself. Whether one is aiming for structural integrity, visual brilliance, or time-tested resilience, the journey of TIG welding stainless steel underscores the importance of continuous learning, adaptation, and, most importantly, passion for the craft.