Sheet metal welding plays an important role in modern manufacture, whether it is in automobile manufacturing, construction projects, or electronic equipment and household appliances, the application of sheet metal welding technology can be seen everywhere.

In this article, we will introduce the types of sheet metal welding, techniques, and common problems to help you fully understand this technology and improve the quality of your welds.

What is Sheet Metal Welding?

Sheet metal welding is a welding process used to join thin metal sheets, usually involving metal materials with a thickness of 1/16 inch (about 1.5 mm) to 1/4 inch (about 6 mm). The process is commonly used for different types of metals, such as aluminum, stainless steel, and carbon steel, and is widely used in manufacturing, construction, automotive, and aerospace industries.

Types of Sheet Metal Welding

1. METAL INERT GAS WELDING (MIG WELDING)

MIG welding is a common type of welding. The basic principle is to use a solid wire electrode in the welding tool to melt the wire by the heat generated by the arc, forming a molten pool and joining the metal parts using the melted wire as filler material. To prevent the molten pool from being contaminated by the surrounding atmosphere, MIG welding also uses a shielding gas, usually argon, carbon dioxide, or a mixture of them.

MIG is widely used in a variety of industries, especially in automotive manufacturing, home improvement, and metal fabrication. It has become the welding method of choice in these industries due to its ability to work with a wide range of metal materials (e.g., aluminum, stainless steel, and carbon steel), its relative simplicity, and its high welding efficiency. In addition, MIG welding is suitable for high-volume production due to its low equipment costs and high degree of process automation.

Pulsed MIG welding is an upgraded version of MIG welding, in which a pulsed current is applied instead of a constant current. Pulsed MIG welding allows the operator to weld at lower currents, which reduces spatter and improves the quality of the weld, making it particularly suitable for thin plate welding. The advantage of pulsed MIG is the precise control of the heat input and the reduction of heat distortion, which makes it suitable for welding scenarios with high demands on the quality of the weld.

2. TUNGSTEN INERT GAS WELDING (TIG WELDING)

TIG welding is another widely used arc welding technique. The method uses a non-consumable electrode made of tungsten, which is passed through an electric current to form an arc that heats the metal and makes the weld. Similar to MIG welding, TIG welding also utilizes inert gases (such as helium and argon) to protect the weld from atmospheric contamination and electrode oxidation.

TIG welding excels at working with non-ferrous metals such as aluminum, magnesium, titanium, nickel, and chromium, making it widely used in industries such as automotive manufacturing, motorcycle frames, aerospace, and more. Due to its high degree of control over the welding process, TIG welding enables high-quality welds, especially for applications that require delicate welding.

However, TIG welding requires a high level of operator skill and is relatively slow. This is due to the need for the operator to manually feed filler material into the molten pool and the precise control of welding parameters such as current, gas flow, and welding speed. Beginners need to master basic TIG welding techniques so that they can later attempt more complex welding methods.

Pulsed TIG welding is a variation of conventional TIG welding in which the current is distributed in pulses. This method offers advantages in several ways, including higher quality welds, better heat input control, and suitability for welding both thin and thick metals. Although pulsed TIG welding provides better weld results, it is correspondingly more difficult to operate, so it is advisable to familiarize yourself with conventional TIG welding methods before attempting it.

3. SHIELDED METAL ARC WELDING (STICK WELDING)

Stick arc welding, also known as shielded metal arc welding, is one of the oldest types of welding. In stick welding, the core tool is a flux-coated welding rod, which plays the role of an electrode. Similar to MIG and TIG, electrode welding involves the use of an electrode to excite an electric arc between the metal parts to be welded, completing the welding operation.

It is important to note that electrode welding does not require the inert gas protection that MIG or TIG typically require. But that doesn’t mean that the weld area is left unprotected and exposed to unfavorable environmental conditions – and that’s where the flux plays an important role. The flux on the outer layer of the electrode responds to the high temperatures of the weld by breaking down and forming a protective layer of slag that covers the weld seam and effectively shields it from external contamination.

Although electrode welding may not be as accurate or aesthetically pleasing as MIG or TIG welding, it has significant advantages in terms of simplicity and cost-effectiveness. At the same time, electrode welding is widely used in various industries such as shipbuilding, construction, and steel manufacturing due to its portability.

4. ELECTRON BEAM WELDING/ LASER WELDING

Electron beam welding and laser welding, despite being relatively costly and application-specific methods in the field of welding technology, have demonstrated high precision and excellent performance, making them irreplaceable in specific industrial sectors.

Both welding methods rely on highly sophisticated equipment to generate the heat required for welding using a laser or electron beam. This precise heat source allows them to achieve micron-level welding accuracy, making them ideal for manufacturing high-precision metal parts. Whether electron beam or laser welding, they are capable of handling a wide range of high-strength metal materials, such as carbon steel, stainless steel, and titanium, while maintaining the aesthetics and consistency of the weld.

Their applicability is not limited to high-end metals. They are equally capable of handling more common materials, such as aluminum and thermoplastics, under certain circumstances. Although application on these materials may not be the most cost-effective option.

5. GAS WELDING

Gas welding, a time-honored form of thermal welding, utilizes the heat generated by the combustion of a fuel (e.g., gasoline) mixed with oxygen or oxyacetylene to melt and join pieces of metal together.

Gas welding has a wide range of applications, not only for ferrous metals (e.g., iron, steel, etc.) but also for non-ferrous metals (e.g., copper, aluminum, etc.). It is also very effective and efficient for welding pipes, repairing ventilation and air-conditioning systems, etc. Unlike many other welding techniques, it does not require electricity. It is relatively economical, portable, and requires and requiressevel to operate.

6. PLASMA ARC WELDING

Plasma Arc Welding is similar in basic principle to TIG welding in that they both use a tungsten electrode as the conductor of the arc. However, the key difference in plasma arc welding is that it uses a smaller arc, which allows the electrode to be placed on the body of the torch. By applying additional pressurized gases (usually inert gases such as argon) to the arc, these gases are ionized at high temperatures, creating a hot plasma. The hot plasma has an extremely high temperature and energy density that rapidly melts the metal to be welded, resulting in a strong weld joint.

This welding technique requires low power, is fast, and produces precise welds that are widely used in the aerospace and marine industries.

Plasma arc welding eliminates the need for filler material, resulting in a high-quality weld with little or no subsequent cleaning. The low power requirements, high speeds, and precise weld seams have led to a wide range of applications in the aerospace and marine industries.

Types of Metals Used in Sheet Metal Welding

1. Mild Steel: Commonly used for automotive bodies and construction applications.

2. Stainless Steel: Offers excellent corrosion resistance, making it ideal for the food industry, medical devices, and marine applications.

3. Aluminum: Lightweight and corrosion-resistant, it is widely used in aerospace, automotive, and electrical applications.

4. Copper Alloys: Known for their thermal and electrical conductivity, these materials are used in HVAC systems and electrical equipment.

Tips for Sheet Metal Welding

1. Use the right metal technique: Choose the right welding technique for different metals (e.g. stainless steel, titanium, etc.). Each metal has different welding requirements, and careful selection and adjustment of the technique is the key to ensuring the quality of the weld.

2. Skipping Welding Method: Using the skipping welding technique when welding requires several short welds at key locations to fix the position of the thin metal plate. After cooling for a few minutes, continue to weld areas that could not be welded before, which can effectively reduce metal deformation and warpage.

3. Position welding technique: Use spot welding (tack welding) to join thin steel sheets, leaving a 1mm gap between the metals to ensure that the fusion of the spot welds does not affect the surface. The welds should be small enough to avoid damage to the material.

4. Carry out metal trial runs: Before formal batch welding, carry out small-scale trial runs to optimize welding parameters and ensure welding quality.

5. Select the appropriate filler metal: Select a filler metal that is compatible with the metal being welded. Pay attention to the thickness of the filler metal, too thick filler metal may lead to overheating, too thin, and the weld may not be strong.

6. Use a small electrode: Select an electrode that is less than 1/8 inch in diameter. This produces a tighter arc, reduces the risk of burn-through, and allows for more delicate welding work.

7. Use small diameter wire: Select the proper diameter wire for the material being welded. Beginners can use fine wire diameter wire to reduce the difficulty of operation, with increased experience, and gradually use a thicker wire.

8. Use high argon shielding gas: use high argon ratio shielding gas when welding aluminum. Argon is an inert gas, and will not react with the metal to prevent oxidation; if it is pure argon, properly add carbon dioxide to improve its density.

9. Adjust the heat control: when welding metal, heat is an important factor. Select different welding methods (such as GTAW) and adjust the heat according to the type of metal to prevent excessive melting leading to welded joint failure.

FAQ

1. What are the most common defects in sheet metal welding?

Common defects in the sheet metal welding process include weld cracks, porosity, and inclusions. Welding cracks are usually caused by excessive stress during welding or improper heat treatment; porosity may be due to insufficient shielding gas or contaminants on the weld surface; and inclusions may be caused by impurities in the weld material or instability in the welding process.

2. How to minimize deformation in sheet metal welding?

To reduce welding deformation, the following methods can be taken:

①Reasonable control of heat input: Reduce excessive heat input by adjusting welding current, welding speed, and arc length.

② Use of fixtures: Use fixed fixtures during the welding process to ensure that the workpiece stays in place and to prevent deformation during the welding process.

③Segmented Welding: Long welds are welded in segments to reduce the concentration of local heat and avoid weld distortion.

3. How to choose a suitable welding process in sheet metal welding?

The choice of welding process depends on the type of material, plate thickness, welding requirement, and productivity needs. For thick plate welding, MIG welding and laser welding are good choices; while for thin plate welding, TIG welding can provide higher precision and beautiful weld seams.