Stainless steel is widely used due to its durability, corrosion resistance, and aesthetic appeal. TIG welding, resistance welding, and MIG welding are the most commonly used methods in the United States. Stainless steel contains at least 10.5% chromium content for added corrosion resistance.
TIG welding is a widely used method for welding stainless steel, focusing on the thickness and finish of the material. Welders use three methods: TIG, resistance, and MIG welding. In this reading, we’ll discuss stainless steel welding, its methods, best practices, and challenges.
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Stainless Steel Welding
Welding stainless steel is a challenging task due to its corrosion resistance and high hygiene requirements. However, with the right tips and advice, you can work with this material efficiently. Stainless steel has a lower thermal conductivity, allowing heat energy to dissipate more quickly from the welding zone.
With a minimum 10.5% Chromium content, it can take a lifetime to achieve the best results. Whether you’re just starting out or regularly working with this material, these tips can serve as a valuable learning aid or reminder. By following these tips, you can soon master the art of welding stainless steel.
Related: What is Stainless Steel? Its Properties, Types, How it’s Made
What are the Methods of Stainless Steel Welding?
The common methods of welding stainless steel are shielded metal arc welding SMAW, tungsten inert gas TIG welding or GTAW, metal inert gas MIG welding or GMAW, friction welding, resistance welding, and flux cored arc welding FCAW.
Shielded Metal Arc Welding
SMAW is a cost-effective and versatile method for welding stainless steel, suitable for various repair jobs and outdoor welding. Thicker pieces of stainless steel (above 2mm) are ideal for SMAW due to its difficulty in controlling heat input. The electrode selection, typically 316, 308, or 312, is crucial, and slag removal after welding can be challenging. SMAW is suitable for various environments and can be performed outdoors.
Tungsten Inert Gas Welding
TIG welding is a popular method for fabricating stainless steel due to its stable arc and automated process. This method allows precise control of heat applied to the weld, minimizing warping. TIG welding machines can switch between AC and DC polarities, providing flexibility and convenience. However, gas tungsten arc welding is costly due to the need for consumables like shielding gas and filler rods. Therefore, selecting the right electrode geometry and size is crucial for successful welding.
Metal Inert Gas Welding
MIG welding is a popular choice for stainless steel welding due to its faster speeds and continuous fed electrode. A Teflon wire liner ensures consistent wire feed and protection from contamination. Warpage can be avoided by backstepping, staggering, or allowing the joint to undergo cooling, as stainless steel retains heat well. However, this technique may not be as visually appealing as TIG welds.
Friction Welding
Friction welding stainless steel is an economical choice due to its lack of consumables and suitability for austenitic stainless steel due to its chromium and nickel composition. Factors like friction pressure, burn-off length, and rotational speed must be considered. Sub-types like friction hydro pillar processing, friction stir welding, and friction plunge welding may be suitable for specific applications.
Resistance Welding
Resistance welding, such as spot and seam welding, is a method that creates clean welds without filler material and reduces the risk of weld spatter. Its high electrical resistance allows for quick weld completion. However, a high-quality welder with sufficient power output is essential to prevent deformities in areas close to the HAZ. Higher current and voltage values are recommended for welding stainless steels compared to copper and aluminium alloys.
Flux Cored Arc Welding
Flux-cored arc welding (FCAW) is a preferred method for creating uniform weld beads in stainless steel, often paired with shielding gas for varying material thicknesses or demanding welding conditions. A 10° drag angle ensures sufficient flux rise at the weld pool.
Best Techniques for Welding Stainless Steel
Stainless steel welding best practices involve safety, preparation, filler material selection, and fine-tuning parameters to achieve high-quality welds. A dedicated stainless steel wire brush and protective gear are essential for reducing contamination risks. Filler material selection should match the grade of the stainless steel, ensuring similar properties.
Experienced welding providers understand the finer details of each stainless steel grade, weldable metals, and welding method, leading to better choices in parameters such as power supply, torch angle, travel speed, and deposition rate. The choice of shielding gas is crucial in protecting the weld pool from contamination, reducing the risk of defects and improving the overall outcome.
The ideal heat input for welding stainless steel should be about 20% less than for carbon steel to prevent corrosion. By following these best practices, we can ensure the highest quality welds for our clients.
Choosing The Right Stainless Steel Welding
Choosing the best method for welding stainless steel depends on your specific needs. Spot welding may be the best option for an affordable weld, while TIG or gas tungsten arc welding may be more suitable for thin materials. All-Type Welding and Fabrication, Inc. evaluates materials, capabilities, and finishing styles to determine the most effective method for each project. With extensive welding knowledge and experience, it’s crucial to consider the best stainless steel welding method for your project.
Related: What is Sheet Metal? its Types, Sizes & Forming Processes
Challenges In Stainless Steel Welding
Stainless steel welding presents unique challenges due to its mechanical properties, including its various grades and types. These challenges include warping and cracking, which can occur due to low thermal conductivity and high thermal expansion. To prevent these issues, it is essential to strike a balance between lower heat input and avoiding incomplete fusion between workpieces.
Another solution is to create a heat sink by clamping copper or brass behind the seam, absorbing unnecessary heat into copper alloys.
Despite stainless steel’s high corrosion resistance, excess heat can still generate rust in the weld. This can be due to the carbon from the filler material contaminating the heat-affected zone. To reduce the risk of rust formation, it is crucial to choose an optimal welding temperature and a stainless steel filler alloy depending on the job.
Welding dissimilar steels can be challenging due to their far apart melting points, causing issues in fusing. Selecting the optimal filler rod and preheating the metals can help. Switching between jobs can be problematic due to the lower melting temperature of stainless steel compared to mild steel.
Stainless steel welds produce toxic fumes, such as hexavalent chromium gas, which can occur during heating or cooling. To ensure safety, an effective breathing mask and proper ventilation are essential.