Metal welding is a time-honored process that is still used today. There are many different types of welding, and the type of project usually influences the type of welding used by the manufacturer. Tack welding is a particularly important type of metal welding.
So what is tack welding? What are the different types of this welding process? What are the advantages or disadvantages of this type of welding? Which materials are best suited for this process? Read on to find out these and other things about tack welding.
Table of Contents
What is Tack Welding?
Tack welding is a temporary welding process. It joins metal parts using low heat and a very short arc before the final welding. It makes welding easier by preventing the metal sheets from moving before the sheet metal welding process is complete. Without this process, it would be impossible to weld to specification. And precise welding can be difficult.
The aim of tack welding is to hold the parts to be welded in place. This helps to maintain consistency in position, distance, and alignment before the final welding. In other words, tack welding is used to hold parts in place while the workpiece is being assembled. It therefore needs to be strong enough to withstand considerable stress.
Why is Tack Welding so Important?
Although tack welding only serves a temporary fixing function, it is crucial to the success of any welding operation. Its main functions throughout the welding process are to:
- Ensure that the materials are correctly aligned
- Hold the components in place during the welding process to define their position
- It helps to define the joint gap
- Maintaining the joint gap to ensure that it does not change further
- It increases the strength of the weld while reducing distortion
- It enhances the function of fixtures or replaces them completely if necessary
- It helps to maintain the mechanical strength of the component, albeit temporarily. The aim is to ensure that the component retains its shape in the event of any changes.
Since this form of welding is reversible, manufacturers can better control the manufacturing process. In addition, it saves time and money identifying design problems. Because the manufacturer can see how the component will look before the final weld is applied. This helps to achieve a high-quality, precise end result.
How Does Tack Welding Work?
In this process, an electrode helps to join metals by supplying an electric current that partially heats the workpiece component. Like other sheet metal welding processes, this process also uses heat and pressure. The key to successful tack welding is distributing small tack welds between metal components.
They help to prevent warping and overheating of the workpiece before the final weld. These spots are usually between 1/2 and 3/4 inches apart, but no longer than 1 inch, which helps keep the workpiece tidy. They are also ideal for small production runs and are often used as fixtures.
If you would like to find out more about sheet metal joining processes. Then please take a look at our riveting and welding comparison guide.
Materials for Tack Welding
Weldable metals can also be tack welded. However, the difference between them lies in the technique used during the welding process.
In addition, the ease with which a tack weld can be made depends on the thickness and type of material. Thin materials with a low melting point are more difficult to tack weld than others.
The most common metals for this welding process are steel and stainless steel, aluminum, cast iron, copper and brass, titanium and magnesium alloys.
Types of Tack Welding
There are various different types of tack welding, each with its own optimal use. We will introduce the five types most commonly used by welders.
Standard Tack Weld
Standard tack welding is the best choice when a final welded support is required. The welds in this process are usually large enough to support the weight of the welded parts and prevent them from breaking. It should be noted that they should not be too large so that the final weld consumes them.
Bridge Tack Weld
This spot welding is used by the welder when there are gaps between the materials that need to be filled with a weld seam. Such gaps are often the result of a cutting error or a deformation of the material supplied by the supplier.
Using bridge tack welding in this case involves alternately spot welding small welds on each component. The purpose of alternating the spot welds is to allow one side to cool before re-welding.
However, this type of tack welding is best suited to flux-cored welding or MIG and TIG welding. This is because they are relatively easy to trigger.
Thermit Tack
Thermit tack is made from a mixture of pure magnesium metal, aluminum powder, and iron oxide powder. This mixture usually produces a very hot reaction, with temperatures exceeding 4000 degrees Fahrenheit.
Hot Tacking
Hot tacking is the deposition of excess filler metal in the gaps between metal parts. The aim is to use the weld to bridge the metal gaps. Hot tacking is the best option when the welded components need to come into contact, but for some reason cannot.
Although this method is similar to bridge tack welding. The difference is that after the welder bridges the parts with a weld, he will use a sledgehammer to strike the parts into place.
Ultrasonic Tack
Ultrasonic tack welding is done using an electric or gas welding process. The welder applies ultrasonic speed to the welding area by pushing or pulling it several times in a short burst. The welder then uses a filler wire to press molten material into the base metal and fuse the parts together.
The Four Forms of Tack Welding
Tack welding holds parts together before they are fully welded. Tack welding therefore helps to join parts. There are four main forms of tack welding:
- Square: This form of tack welding is strong and durable. It involves tack welding in a square pattern and is suitable for joining two parts at right angles.
- Vertical: This form of tack welding involves placing a tack between two metal parts so that it runs vertically from the top to the bottom of the parts. It is best to tack the top metal piece when you need to align two components vertically.
- Right Angle: This tack welding is ideal for welding two metal parts that are positioned vertically. For example, if you want to join two parts at a right angle. Then the bottom part is ideal for joining.
- Right Angle Corner: A right angle corner is suitable if two vertically positioned parts are combined to form a T shape. In this case, the welder joins the parts at a 90-degree angle.
Practical Ways to Ensure High-quality Tack Welding
It is best to carry out tack welding in such a way that it does not affect the final welding. Defective tack welding can make the welds prone to cracking and insufficiently strong for their function. Such welds in assemblies can endanger people and property. They can tear, fall, or tip over during movement.
It is therefore essential to carry out high-quality tack welding. This gives the manufacturer a clear idea of how the final welded product will look. It also avoids the dangers associated with poor tack welding. This is particularly true when connecting boilers and pressure vessels. Here are some key tips for ensuring high-quality tack welding.
Testing Metal Parts
Testing the metal parts is essential for confirming the quality of the tack welding. The aim of this method is to determine the sequence in which the parts are laid and the amount of filler wire required for the entire process. To avoid waste, carry out this test on scrap metal.
Clean the Metal Filler Wire
Contamination can affect the success of the tack welding and result in the parts not joining properly. Therefore, it is important to keep both metal parts clean and free from contaminants such as rust, debris, and oil.
Secure with Tape
To prevent unwanted movement during the welding process, fix the parts together with adhesive tape. This helps to prevent alignment problems when the metal parts cool and return to their natural shape. In addition, the use of adhesive tape ensures that the parts remain vertical. This avoids problems due to imbalances.
Know the Area
Since tack welding is not used to fix the entire part, it is important to choose the most suitable welding position. In other words, find two or three fixing points on the part to hold it together.
Controlling Distortion with Tack Welding
The most effective way to control distortion is to plan the sequence and direction of tack welding in advance. For example, when welding longer seams, start in the middle. Then tack weld or back weld in both directions alternately over the length of the seam. This helps prevent distortion and stress build-up.
It is advisable to tack weld in sequence. Tack welding from one end to the other may result in shrinkage. This shrinkage may cause one sheet to overlap the other or close the gap at the other end.
Ensure that You Use a Filler Wire with High Strength
The type of welding determines the type of filler wire. For example, if you are welding with a Mig welding machine, you must use the correct shielding gas.
Maintain Heat Balance
Provide the same amount of heat on both sides of the weld to ensure that the metal gets the right amount of heat while preventing warping and melting. One second is ideal.
Allow the Metal to Cool
Moving the metal before it has completely cooled may cause it to break. Therefore, it is best to allow the weld to cool completely before moving the metal.
Advantages and Disadvantages of Tack Welding
Like most manufacturing methods, tack welding has advantages and disadvantages. Let’s examine some of them.
Advantages of Tack Welding
- This welding method enables manufacturers to test their designs before making a permanent connection.
- The welding process is simple and can be completed quickly.
- Tack welding is inexpensive. This is because manufacturers can use non-consumable welding wire instead of expensive filler materials.
- Fixed parts can be moved even if they are not rewelded.
- It helps to fix parts that are difficult to fix with hands or work clamps.
Disadvantages of Tack Welding
- This welding method is usually less effective and does not last long.
- Both parts need to be heated. It is therefore difficult to tack weld larger parts or near the edges of parts.
- Using filler wire only may increase the cost of welding. This is especially true if scrap wire is not available.
- This method requires a high level of concentration to avoid accidentally tack welding the wrong parts together.
- If the welding area is too large, it may make the final welding more difficult. The welder must then grind it down to a smaller size.
Why Choose Yonglihao Machinery?
Tack welding is beneficial to the manufacturing process, which is why many metal manufacturers use it. However, if tack welding is not done properly, it can waste more time and money. That is why you need a reliable and trustworthy company to complete the task. Yonglihao Machinery can provide you with quality metal welding services.
Whether you need unique metal prototypes or metal parts. Yonglihao Machinery can provide you with sheet metal fabrication and other production services. If you need welding services, we use high-quality welding equipment and inspection processes to produce precision metal parts that exceed your expectations.
In addition, we offer short delivery times and reduce your manufacturing costs with reasonable pricing and cost-effective shipping options. If you need help. Upload your design files to our website to get a quick quote. Yonglihao Machinery also provides in-depth and free DFM feedback.
Conclusion
Tack welding can temporarily hold metal parts together. It also helps manufacturers and welders ensure that parts are oriented correctly and leave adequate space for the connection. The strength of spot welds depends on the filler material used and the number of spot welds.
FAQ
Why Does Tack Welding Crack?
Cracks are caused by defects in the tack welding. Rapid cooling, high thermal stress, and shrinkage due to solidification are common causes. This is particularly the case when the weld cools.
Is Tack Welding Strong?
The strength of the tack welding depends on the filler material used and the amount of welding. However, if done correctly, tack welding can withstand considerable force without breaking.
Can Galvanized Steel Be Tack Welded?
Yes, you can tack weld galvanized steel. However, you must do so with care. The zinc in this steel becomes toxic when heated.