Sheet metal welding: MIG vs TIG

For metal fabricators, successful sheet metal welding includes selecting the appropriate welding method after considering matters such as material, productivity, burn-through, distortion, excessive heat-affected zones, weld appearance and secondary finishing methods.

• Material: MIG welding is suitable for a range of material thicknesses, from thin gauge sheet metal to more substantial structural parts. With TIG welding, the welder can control the heat input so it is often used at lower currents for fragile and soft exotic metals where heat and distortion must be minimal.
• Productivity (Cost & Speed): MIG welding often delivers higher productivity as it is a much quicker process that requires much less time and skill. However, this should not always be assumed. When part of a more comprehensive fabrication project, TIG welding can bypass the need for grinding and other finishing methods which can add to overall costs.
• Strength: Although TIG welding is more complex and slower than comparative approaches, the process provides the welder with greater control which allows for stronger, higher quality welds, particularly important when manufacturers are seeking fabrication of watertight components.
• Component Design: MIG welding is selected when sheet metal components require long welds to be made without pausing, when the weld needs to be applied quickly or if the sheet material is too thick for spot welding. TIG welding delivers a more precise superior finish and is the chosen method when the design includes intricate detail.
• Weld Appearance: Unfortunately, it is impossible to carry out sheet metal welding without leaving a visible burn mark on the surface of the sheet metal. The weld mark can be cleaned or linished, or the part painted or polished, so the joint becomes invisible. As a result, the desired weld appearance is a significant influence of the method used.

If a product specifies a powder-coated finish, for example, a MIG weld will deliver a more than sufficient quality weld with no visible defect. However, if fabrication products require the cleanest, most aesthetic weld possible and will not be undergoing a separate finishing process, TIG will deliver a significantly more attractive result.

Considering the above differences, typical applications for each method often differ.

Typical examples of products that are created by MIG welding aluminium and thin-gauge steel include the manufacture of power distribution units, HVAC systems, retail stands, electrical enclosures and various other metal cabinets.

On the other hand, TIG is favoured by metal fabricators for the sheet metal welding of stainless-steel products and components where an aesthetic appearance is key. For example; automotive parts, food processing equipment and cosmetic appliances such as catering and washroom products.