Welding is a popular joining process that’s also quite important in sheet metal fabrication. We can use welding to create a variety of permanent, mechanically strong joints between cut sheet metal pieces.
Depending on the part’s purpose, these welded joints can also be made to be leak or pressure-tight. Thanks to these advantages, welding is used extensively when creating functional parts like storage tanks and pipes from sheet metal.
In this article, we’ll be giving you a crash course on sheet metal welding. We’ll show you the different welding procedures available and give some important tips for welding sheet metal.
What is Sheet Metal Welding?
Welding involves joining two metals using either heat, pressure, or a combination of both. The surfaces of the metals to be joined together are heated until they are near or at their melting points.
At this point, the metals melt and fuse together to form a strong joint as they cool down. An additional piece of metal, known as filler metal, can be melted in with the metals to help form the joint.
The molten filler metal will flow in and fill the gap between the two base metals.
Types of Sheet Metal Welding Processes
There are many welding processes available for joining sheet metal together. What differentiates them is the source of energy they use in melting the metal and the joining technique.
Some of the popular sheet metal welding processes include:
√ Metal Inert Gas (MIG) Welding
MIG welding is an arc welding procedure that uses a continuous feed of a consumable wire electrode as the filler metal. It uses an electric current to strike an arc between the wire electrode and the base metal.
Note: The base metal refers to the metals being joined together.
The arc melts the base metal and the wire electrode into a weld puddle. The weld puddle cools and fuses to become the welded joint.
While welding goes on, a stream of inert or semi-inert gases protects the weld from oxidation while it cools. A common mixture welders use is Argon and Carbon Dioxide.
MIG welding is more suitable for joining larger and thicker pieces. It is also quite fast, which reduces labor costs and lead times.
Sometimes, the larger weld beads can also make for stronger joints. However, the weld puddle of MIG welds is hard to control, leading to messy, imprecise welds.
√ Tungsten Inert Gas (TIG) welding
TIG welding is another form of arc welding. However, unlike MIG welding, the wire electrode is a non-consumable tungsten electrode.
This means the electrode doesn’t melt into the weld puddle like filler metal. The welder has to feed in the filler metal manually.
This gives the welder greater control over the weld puddle resulting in high-quality, clean, aesthetically pleasing welds. The resulting TIG welds are also stronger than MIG welds.
Additionally, TIG welding produces less heat, making it more suitable for thinner sheet metal gauges. However, it is slower, more expensive, and requires more skill.
√ Laser Beam Welding
Laser welding uses a laser beam to join two metals together. The concentrated laser beam provides the heat source that melts and fuses the two metals together to form the weld.
Laser welding is a very fast and precise form of welding. Due to the tiny, intense nature of the laser beam, welders can achieve high weld rates with extreme accuracy.
They can also control how far the weld penetrates by adjusting the laser’s power output.
As a result, laser welding is more suited to mass production lines. Here, the laser beam is controlled by a computer to produce complex and accurate welds on the production line.
√ Gas Welding
Gas welding utilizes an oxyacetylene torch to join the sheet metal together. The torch mixes oxygen with acetylene and ignites it, then uses the flame to heat the base metals until they’re near their melting point.
Once the base metal is melting, the welder adds a filler metal to create a welded joint between the two metals.
Gas welding is versatile and can be used for ferrous and non-ferrous metals. It is also suitable for metals that require a slow heating and cooling rate.
However, it can be quite slow when compared to other methods. Additionally, it cannot reach the high temperature that methods like arc welding can reach.
As a result, it’s not suitable for thicker materials.
Types of Basic Sheet Metal Welding Positions
Knowing about the basic sheet metal welding positions is very important. During welding, flipping the part over to an optimal position might not be possible.
Metal joints are welded in place or in the position in which the part is meant to be used. As a result, welders often need to access joints to be welded from all sorts of angles.
Knowing the basic positions will help choose the right welding techniques, processes, and filler metal.
Here are the main sheet metal welding positions:
√ Flat Position
This is the simplest welding position. The parts for welding are placed flat, and the welding is performed from the joint’s upper side.
The weld puddle naturally flows into the joint, and the weld face and axis are horizontal. This position works with any welding process.
√ Horizontal Position
In this position, the weld axis is still horizontal. However, the welder approaches it from a side angle. Here are the two main types of welds performed in this position:
Fillet Weld (2F):This weld joins a vertical surface resting perpendicularly on a horizontal surface. The final joint forms an ‘L’ shape.
The weld face is horizontal.
Groove Weld (2G):This weld joins two vertical surfaces resting on each other in the same plane. The weld face here is vertical.
You can use all types of welding processes for this position.
√ Vertical Position
In this position, the face and the axis of the weld are vertical. This type of position is used when welding two vertical surfaces placed side by side.
The weld usually goes from top to bottom or vice versa. Welding in this position is hard, as molten metal can flow down and accumulate.
To solve this, the welder holds the torch and electrode away at an angle from the joint. Also, they weld from bottom to top.
√ Overhead Position
This is one of the most difficult positions to weld a joint. The welding is done from below the joint, which is between two horizontal surfaces.
Due to gravity, the material deposited from the weld can droop or sag before cooling, resulting in large beads. As a result, the weld puddle needs to be kept small to avoid large weld beads.
The overhead position is mostly used when the parts to be welded are large and immovable.
How to Get High-Quality Sheet Metal Welds
High-quality sheet metal welds increase the part’s aesthetic and result in a stronger joint. They also reduce the part’s costs as they require fewer finishing processes.
Here are some tips on how to get the best welds.
1. Choose the Right Welding Process
The best way to ensure you get the best final product is to select the right welding process. Some welding processes aren’t suitable for some materials or use cases.
For example, if the material isn’t used for cosmetic purposes, it might be more prudent to go with MIG welding. This process is faster and cheaper than other processes.
Also, MIG welds are better for joining thicker materials together.
However, if the product requires neat, accurate welds, you might need to go with TIG or Laser welding. It all depends on the order size and the machines available in the shop.
2. Choose the Right Filler Metal
The joint’s strength, corrosion resistance, and other physical properties depend on the filler metal. Choosing the right one will result in a long-lasting, mechanically strong joint.
So, you should always select a filler metal that is as physically and chemically similar as possible to the base metal.
Additionally, ensure the filler metal is always thinner than the sheet metal. Thinner fillers require less heat to melt, thus reducing the risk of overheating and its associated problems.
3. Choose a Small Wire Diameter
When welding sheet metal using the MIG welding process, you should always choose a small wire diameter. A small wire diameter requires less heat to melt.
It also produces a smaller weld puddle, which means less spatter and a neater weld.
4. Control the Heat
Defects like burn-throughs and warping can result from overheating the metal. They can be caused by overheating the metal and dwelling too much with the torch or electrode in one area.
To avoid this, welders first place tacks along the length of the joint before joining the tacks with intermittent welds. This helps deal with the overheating problem, especially when welding sheet metals.
The final quality of a welded sheet metal product depends heavily on the skill and experience of the welder. That’s why you should always go with a top-notch machine shop like RapidDone for all your sheet metal welding needs!