What Is Tack Welding?
Tack welding is the temporary welding operation on items before the final welding operations take place.
Tack welding can come in handy when placing work materials in location especially in the short-term welding process. The tack welds are short welds and are often used in construction. These tack welds are made briefly distances to hold the items together in one place.
There is a key benefit in tack welding. That is, if there is an error in the primary welding process, the items can be easily taken apart and repositioned. They can then be tack welded yet again.
Typically, the procedures followed in tack welding are same as standard welding. For example, when assembling aluminum-alloy a small tool, is used to join through friction stir welding.
On the other hand, electron beam tack welds can be utilized as well. These consume less power and capable of positioning items while maintaining the shape and dimensions before final electron beam welding.
Why Are Tack Welds Important?
One might think that the temporary tack welds are not that important regarding its nature. In reality, these secondary welds are just as important as the final welding operations. Thus, they need to be properly planned and operated. The importance of tack welds are as follows:
- Positions the individual items in order and keeps them in place.
- Maintains proper positioning
- Can be used as a compliment to item positioning and easily removable
- Keeps the movement and distortion while welding to the minimum
- Keeps the joint gap intact
- Boosts the mechanical strength of the elements for a short period for further operations
Defective Tack Welding Risks
Necessary precautions and observations are needed when performing tack welding. It will prevent any rupture, fall out of parts and damage to resources.
Tack welding should be done in such a way that it does to disrupt or degrade the overall quality of the final welding. It should not include welding flaws such as craters, cracks, slags and hard spots.
Numerous steels are prone to rapid cooling and quenching; that might have a harmful outcome in overall welding procedures. The higher the heat input, the slower the cooling rate. This will keep the microstructures in place.
Microstructures that are hard and prone to crack might be visible in the heat-affected zones (HAZ). It will occur when the metal items are quickly quenched. It will result in invisible cracks. They might be there even after removing the whole tack weld.
Distortion Control Procedures
To prevent distortion in the welding process, make sure to control the sequence and the direction of the tack welds. If you want to maintain enough weld penetrations, make sure to keep the joining gap and resist transverse shrinkage in your tack welding procedures.
When it comes to long seam, start your tack welding process at the middle and move along the common length. It will alter in both directions and help you prevent deformation.
You can also place your tack welds at the end of the joints. For doing so, you need to start at the middle and keep the process going on until the full length is covered.
Pay proper attention when positioning your pieces to maintain successful root past. Tack welding is vital when it comes to setting up your pipes for welding. Surely fitters are more than capable of performing this task. But make sure to supervise closely when workers are doing their job.
The number and size of tack welds depend heavily on the diameter and thickness of the pipe. Tack welds should be the same quality as final welds. Make sure to clean the tack welds before moving on to the final welding process.
Each end of the tack welds signifies the starting and ending points. They are vital when it comes to removing probable errors and represent a gradual slope.
When you are tack welding to braze the positioning, make sure to clean and eliminate the oxides developed in the process. Ensure your welding helmet is properly secured.
In the case of automatic/semiautomatic welding, the meeting sections of the finals weld can incur arc voltage control and filler wire feeding.
Simple or not, tack welding is of utmost importance in an efficient welding plan. You need to be extra careful at every step of this operation to maintain the quality of the entire project.