Tack welds are important when assembling parts. They temporarily secure the workpieces and make the final welding process straightforward even for beginners. Tack welds ensure the parts align properly and prevent mistakes that can be detrimental. However, there are instances where one or more tack welds fall off prematurely before full welding.
This brings us to a series of questions. Does it matter if one of the tack welds breaks during welding? Will the structural integrity of the final weld be compromised? This article explains the consequences of tack welding failure and how to strengthen tack welds so they do not break.
What Are Tack Welds
Tack welds are small and dot-like welds that temporarily hold workpieces together just before applying the main weld. They are important in sheet metal fabrication as they prevent misalignment and mistakes when joining parts to make a whole. Tack welds can be square, vertical, or right angle depending on the position of the workpieces from each other.
Furthermore, there are different types of tack welds you can use in product development. The most common are standard, bridge, hot, and ultrasonic
Standard Tack Welds
They are the basic type of tack weld produced with minimal heat input. Standard tack welds are strong and provide a secure connection. Furthermore, they are usually consumed during the final welding process.
Bridge Tack Welds
As the name implies, what this tack weld does is to close the gap between two workpieces. In this process, it holds the parts and brings them together. Depending on the width of this gap, you may need to use an additional filler material.
Hot Tack Welds
When making hot tack welds, the heat input is higher than that used for the standard type. This high temperature makes the weld penetrate deep. Hot tack welds are ideal for heavy-duty applications.
Ultrasonic Tack Welds
Ultrasonic tack welds are made when high-frequency electricity is converted to waves and vibrations. This generates friction that heats the workpiece. The process of ultrasonic tack welding is fast and reliable.
How Do Tack Welds Work
Tack welds are similar to clamping pins and rivets. However, they provide a stronger and more secure connection. You apply one or more tack welds along the length of the parts to properly align them. This will ensure consistency in the final weld and prevent distortion. Additionally, tack welds act as a guide as you can weld over them. After making the full welds, they are usually consumed through the process. For those that bulge out, you can remove them by grinding or by other suitable means.
Furthermore, tack welds are small and usually less than one inch in diameter. Note that the size depends on the type of tack welding technique and workpiece thickness. There are different techniques you can use for tack welding. They include TIG, MIG, and laser beam welding. They work in different ways and have distinct advantages and limitations.
Does it Matter if One of the Tack Welds Break During Welding
Yes, it matters if a tack weld breaks off during welding. This is because the absence of just one tack weld can affect the quality of the full weld. Tack welds must remain stable and intact before and during the major welding operation. A lot can happen when tack welds break. It can cause the part to shift which will lead to dimensional inaccuracies. Additionally, it can also result in residual stress and different types of welding defects. When tack weld breaks, the aesthetics and structural quality of the final parts become compromised.
Furthermore, there are different reasons why tack welds can break during welding.
- It can happen if the tack weld is too small and unable to withstand the rigorous welding operation.
- A tack weld can also break off if the heat input is too small which limits its penetration into the workpieces.
- You can also experience tack welds breaking off when there are excessive physical vibrations and movements.
- Additionally, tack welds fall during thermal expansion and contraction especially if they cannot resist the stress build-up.
How to Strengthen Tack Welds
To prevent tack welds from breaking off, there are some ways to strengthen and keep them intact. Let’s discuss some of these tips
Optimize Welding Parameters
The welding parameters you use when making tack welds will determine the result you get. These parameters such as current, travel speed, and arc length must be properly modified based on the material properties and workpiece thickness. Using less than the required current and moving the torch too fast will lead to weak welds.
Preheat the Material
You should also consider preheating the workpiece before making tack welds. There are many benefits you get from doing this. Reducing the temperature difference reduces the incidence of thermal shock which can lead to cracks in the weld. Furthermore, it allows for deeper penetration into the base material. Note that the preheat temperature you use depends on the material itself.
Prioritize Structural Points
There are certain points on the workpiece such as corners and joints that hold tack welds better. Making tack welds in these high-stress areas prevents them from breaking off prematurely. Furthermore, when making multiple tack welds along a joint, make sure they are evenly spaced. This will help distribute stress and produce stronger welds.
Use Double Tacking Technique
Consider double tacking, especially for thick and large workpieces. Double tacking describes the process of making a second tack next to the previous one. This technique reinforces the structural integrity of the joint and ensures stability in the welding process. Furthermore, double tacks hardly break off even in large assemblies.
Use Appropriate Filler Material
The filler material you use will also determine how strong the tack weld will be. Make sure the filler material matches the strength of the base metal. When working with relatively thin workpieces, consider low-heat fillers with a moderate diameter. With this, you can be sure of proper workpiece alignment without the tack welds breaking off.
Consider Environmental Factors
The environmental conditions when you are carrying out the tack welding process are important. The environment can affect the strength and quality of the tack welds. High humidity and temperature can lead to brittle microcracks. To control this, use a shielding gas system to protect that weld pool.
Conclusion
One of the common tack weld defects is when they break and fall off. While this might seem like a minor issue, it can cause irreversible damage. The workpieces will not be properly and can lead to dimensional inaccuracies. To prevent this, you should consider preheating the workpiece and welding in an optimized environment. Furthermore, make the tack welds at structural points and use double-tacking techniques if possible.