If you’ve been welding for a while, you’d know that it is the process of fusing metals together with the help of electricity. Welding is used in almost every industry to create complex structures and frameworks of metals.
However, if you want to be successful in your projects, you don’t need to know just how to weld, but also how to undo it.
This could be for any reason. Maybe you messed up. Maybe you need to take apart a previously welded piece for another project.
How do you remove welding? Removing welding depends on many things. Because there are different types of welding, there are different requirements to undo a weld.
Typically, you can remove welding through plasma cutting, torch cutting, grinding or circular saws, drills, or oxy-acetylene torches.
Because welding creates a strong bond between two metals, this bond usually ends up being stronger than the metals themselves, which means that you can’t undo a weld as easily as you could break a piece of metal – for example, with a hammer.
Mistakes are natural and to be expected, and if you are starting out, then there is a very high chance you will make mistakes on your projects. In most cases, to correct these mistakes, you need to know how to undo welds.
There are several ways to do this than just applying heavy force on the weld. The process of undoing welds depends on the type of weld you want to undo.
And depending on that, you would need to decide whether you want to undo it mechanically or thermally.
Here are some tips on how to remove welding:
The word ‘therm’ means heat in greek, so ‘thermal’ refers to anything that involves heat.
Thus, as the name suggests, thermal methods require you to use high temperature in order to undo welds. This is usually done by using oxy-acetylene torches or plasma cutters.
Plasma cutting is a process that involves cutting through electrical conductors with the help of an accelerated jet of hot plasma. Here’s a video on plasma cutting for beginners to check out:
With the help of direct current, an arc can be created, the temperature of which can reach up to 20,000 degrees Celsius. The heat is generated by the high-pressure airflow that comes out of the small nozzle.
Plasma cutting can be beneficial in terms of its cutting speed, since they are about five times faster than manual torches, and can cut through a wide range of material of various thicknesses, so any deep welds can also be undone. They are easy to use and do not employ flammable gases, so they are safer and even more economical than water-jet and laser cutting.
Acetylene torches combine acetylene with oxygen to produce flames at very high temperatures (about 3500 degrees Celsius) to cut or weld metals together.
This method is a little more dangerous, especially for novices. The torch uses a mixture of two gases that are mixed with the help of the cutting torch and create a flame that is hot enough to be able to cut through very thick pieces of metal.
All you have to do is mark a line where you want to perform the cut, ignite the torch, and fine-tune the arch before you follow the line slowly until you cut all the way through.
Torch cutting can be advantageous in that it is easy to use and does not take too much time. The equipment is also cheaper, more portable, and can be used on larger and different kinds of metals for welding and cutting alike.
Here’s a video on how to cut with a torch:
In thermal processes, you used heat to be able to get through the cutting process. In mechanical processes, you perform the cut manually.
There are a few techniques you can choose to employ depending on the kind of weld you are dealing with. For example, spot-welded sheets are challenging to separate, and you often have to perform the separation process by drilling into the sheets themselves.
Sometimes, separating metals can be impossible without causing some damage to the base metals. Mechanical processes usually involve cutting, grinding, or drilling.
Undoing welds without grinders
If you want to break apart welds without using grinders, you can either drill or use plasma and oxy-acetylene torches as a thermal reversal process. You can also go beyond the usual, and use a band saw or a hacksaw.
Steps to take:
- First, you mark the metal where you want to make the cut. This doesn’t need any specific tools, and can quickly be done with a regular pencil or marker.
- Then you hold the metal pieces in place and secure them, so they don’t move. Usually, this is done with clamps or vices.
- If using a gas torch, you will need to open the gas tank. If you are using a plasma cutter, you would have to connect the power cord and turn on the torch. Turn on the compressor and make sure the machine is connected. Then adjust the flame of the torch.
- Move your tool – torch, saw, or anything else – along the line that you made with the pen/marker in the first step. Do this slowly to avoid mistakes, and for safety. Be sure not to linger too long on the same spot. Keep doing this until you have made a successful cut.
- After you’ve turned off your tools, leave the metals and allow them to cool down before you handle them. The machines you use will produce a lot of heat, and handling the metals immediately after cutting can be very dangerous.
Undoing welds with a grinder or circular saw
After welding, it is common practice to grind a weld bead down by using an angle grinder. They can be used to create beveled edges or prepare metal surfaces, and also cut them.
Though the cuts made with grinders are not as precise as plasma cutting, it is cheaper, and since it doesn’t produce as much heat, the surrounding base metal does not reach a temperature that is high enough to alter its properties.
Steps to take:
- Mark the place you want to make the cut with a marker.
- Secure the piece you want to cut using vices or clamps.
- Put on your protective gear.
- Connect your tool – the grinder or the saw – to the electric outlet.
- Slowly allow the grinder to start cutting the metal. Don’t push it with too much force to the base metals. Let it do the work. If you push too hard, you can face the problem of breaking the cutting disc, which is very dangerous.
- Cut the power and let the metal cool down. This heat is due to friction, and not because of the grinder, unlike with plasma or torch cutting.
Which process is better for you?
To decide which process is better suited for undoing a weld, you have to determine the type of base metal that has been used. If the welds are very strong or if you want to undo sheets that are joint together, you may have to drill or grind it open.
Often, welding leaves either one of the pieces damaged. This can be because of filler metals, but it is easily fixed with a grinder or metal file.
After cutting the weld, you often have to grind the bead to weld the pieces again. Grinding off the excess metal allows for a better bead the next time, as opposed to welding the metals without removing the excess.
What causes bad welding?
Bad welding can be a result of many things. Either air may have crept into the weld to cause porosity, or heat can cause cracking. Sometimes bad welding techniques can contribute to the problem.
Can you weld over a weld?
Welding over welds is very common, though there are some concerns.
Differences in welding procedures of overlapping welds – such as heat inputs or cooling rates of the two metals can cause problems. Compositional variation can also lead to issues.
How do you know a weld is bad?
There are some signs of a bad weld. Though different types of welding have different signs, these could have some overlap, such as undercutting, thin welding lines, porosity, lack of uniformity, cracking, spatter, etc.