Welding sheet metal can be challenging, especially if you want to avoid common problems such as warping, burn-through, and excessive heat-affected zones. Sheet metal is thinner than other materials, so it requires a different approach and technique. In this blog post, we will share some tips for welding sheet metal with MIG or TIG, two of the most popular and versatile welding processes.
I. What is MIG Welding?
MIG welding, or metal inert gas welding, is a process that uses a continuous wire feed as an electrode and an inert gas as a shielding gas to create a weld. MIG welding is also known as gas metal arc welding (GMAW) or wire welding. MIG welding is suitable for many metals, such as aluminum, carbon steel, and stainless steel. MIG welding is often preferred for projects that need high production rates and user-friendly operation, making it suitable for various applications.
II. What is TIG Welding?
TIG welding, or tungsten inert gas welding, is a process that uses a non-consumable tungsten electrode and an inert gas as a shielding gas to create a weld. TIG welding is also known as gas tungsten arc welding (GTAW) or heliarc welding. TIG welding is suitable for many metals, such as aluminum, copper, titanium, and nickel alloys. TIG welding offers precision and clean, aesthetic welds that are ideal for intricate or specialized tasks.
Learn MIG VS TIG Welding: What are the Differences?
III. MIG vs TIG Welding for Sheet Metal
Both MIG and TIG welding can be used for welding sheet metal, but they have different advantages and disadvantages depending on the situation. Here are some factors to consider when choosing between MIG and TIG welding for sheet metal:
Thickness: MIG welding is better for welding thicker metals, while TIG welding is better for welding thinner metals. MIG welding can handle thicker materials more easily and faster, while TIG welding can produce more precise and delicate welds on thin materials.
Speed: MIG welding is faster than TIG welding, as it uses a continuous wire feed that melts and joins the metal. TIG welding is slower, as it requires more manual control and skill to feed the filler metal and manipulate the arc. MIG welding is more efficient and productive, while TIG welding is more accurate and refined.
Quality: MIG welding produces good quality welds, but it can also produce more spatter, slag, and porosity. TIG welding produces high-quality welds, but it can also produce more heat-affected zones and distortion. MIG welding is more forgiving and easier to learn, while TIG welding is more demanding and requires more experience.
IV. Tips for MIG Welding Sheet Metal
If you choose to use MIG welding for sheet metal, here are some tips to follow:
Use the smallest wire diameter possible, as smaller wires take less heat to melt and heat the metal less. Smaller wires also provide more control over the weld bead and a better chance of recovering from mistakes. As a rule of thumb, don’t use a filler metal thicker than the base metal. It’s recommended to use a 0.023- or 0.024-inch wire for most light gauge sheet metal work. When the material is 18-gauge and thicker, you may be able to use a 0.030-inch wire.
Use a higher argon-based shielding gas, such as 75% argon/25% carbon dioxide. Argon carries less heat than pure CO2, and you’ll experience less spatter. For welding stainless steel, use a tri-mix gas, such as 90% helium, 8% argon, and 2% CO2.
Use electrode positive (EP, or reverse polarity) when welding with solid wires. Electrode positive produces more heat than electrode negative, but it also provides better penetration and fusion. Don’t attempt to weld thin metal with flux-cored wires, which put more heat into the base metal.
Use a short-circuit transfer MIG (short arc) welding process, which is the most common and easiest way to weld sheet metal. Short-circuit transfer MIG uses low voltage and low current to create a series of short circuits between the wire and the metal. This reduces the heat input and minimizes the risk of burn-through and warping.
Use a push or forehand technique, which means moving the torch in the same direction as the wire feed. This creates a flatter and wider weld bead, which is better for thin metal. A pull or backhand technique, which means moving the torch opposite to the wire feed, creates a narrower and deeper weld bead, which is better for thicker metal.
Use a short and fast travel speed, which means moving the torch quickly along the joint. This reduces the heat input and prevents burn-through and distortion. A slow and long travel speed, which means moving the torch slowly along the joint, increases the heat input and causes more problems.
Use a small and consistent weld bead, which means making a smooth and even weld along the joint. This reduces the heat input and improves the appearance and strength of the weld. A large and irregular weld bead, which means making a rough and uneven weld along the joint, increases the heat input and causes more defects.
Know How to MIG weld different metal thicknesses?
V. Tips for TIG Welding Sheet Metal
If you choose to use TIG welding for sheet metal, here are some tips to follow:
Use a smaller tungsten electrode, as smaller electrodes start easier and perform better at lower heat settings. Smaller electrodes also allow you to better focus the arc in a smaller area. Created or lanthanated tungsten electrodes are preferred, with thoriated tungsten electrodes as a second option. The diameters down to 0.020, 0.040, and 1/16-inch tungsten are popular.
Keep the tungsten electrode pointed, and grind it parallel with the length. This creates a sharper and more stable arc, which is better for thin metal. A balled or blunt tungsten electrode, which is sometimes used for aluminum welding, creates a wider and less stable arc, which is better for thicker metal.
Use a filler metal that is thinner than the base metal, or as close as possible. This ensures you won’t overheat the base metal before the filler metal gets a chance to join with it. For welding steel, ER70S-2 filler metal is a common choice. For welding stainless steel, ER308, ER308L, and ER308LSI filler metals are compatible. For welding aluminum, ER4043 and ER5356 filler metals are suitable.
Use a pulsed TIG welding process, which is a variation of TIG welding that alternates between high and low current. Pulsed TIG welding reduces the heat input and minimizes the risk of burn-through and distortion. Pulsed TIG welding also improves the weld bead appearance and penetration, and allows you to weld in any position.
Use a torch angle of 15 to 20 degrees, which means tilting the torch slightly away from the direction of travel. This creates a better shielding gas coverage and a smoother weld bead. A torch angle of 0 degrees, which means holding the torch perpendicular to the metal, creates a narrower and deeper weld bead, which is better for thicker metal. A torch angle of more than 20 degrees, which means tilting the torch too far away from the direction of travel, creates poor shielding gas coverage and a turbulent weld bead.
Use a filler metal angle of 90 degrees, which means holding the filler metal perpendicular to the metal. This allows you to feed the filler metal more easily and precisely into the weld pool. A filler metal angle of less than 90 degrees, which means holding the filler metal closer to the torch, creates a longer arc length and a larger weld pool, which is better for thicker metal. A filler metal angle of more than 90 degrees, which means holding the filler metal farther from the torch, creates a shorter arc length and a smaller weld pool, which is better for thinner metal.
Use a dab-and-move technique, which means feeding the filler metal into the weld pool and then moving the torch along the joint. This creates a uniform and consistent weld bead, which is better for thin metal. A continuous feed technique, which means feeding the filler metal continuously into the weld pool, creates a larger and more irregular weld bead, which is better for thicker metal.
Know How To TIG Weld Different Metal Thickness?
VI. Conclusion
Welding sheet metal is not as easy as it may seem, but with the right process, equipment, and technique, you can achieve excellent results. MIG and TIG are two of the most common and versatile welding processes for sheet metal, and each has its own advantages and disadvantages. By following the tips we shared in this blog post, you can avoid common pitfalls and improve your welding skills and quality. Whether you are a hobbyist, a professional, or a beginner, welding sheet metal with MIG or TIG can be a rewarding and satisfying experience.
