Welding has been the principal method of joining two metals for more than a hundred years. Its straightforward nature, easy application, and wide availability are the reasons behind its widespread popularity. Metal bending is a relatively newer process. So, welding vs bending is a common debate among people working with metal.
When forming a corner joint, you can either resort to welding or bending. Between two major types of metal joining, you can choose either depending on the type of metal. The principal concern would be the strength and mechanical properties of the joint in which case, bending is the winner.
Although bending takes the crown in terms of joint strength, what makes it the winner is a matter of discussion. In this article, I will discuss extensively on welding and metal bending, what sets them apart and which takes the cake on being stronger. So, keep on reading to have a proper idea of their differences.
How Welding Works?
Welding is the process of joining two metals by applying heat or pressure. It involves a filler metal that melts and joins the two metal pieces together. There are different types of weld joints such as butt joints, T-joints, corner joints, etc. We will focus on the corner joint because that’s where metal bending comes in.
A corner joint forms when two pieces of metals piece together at a 90-degree angle. There are various types of corner joints. Fillet weld corner joints have rounded corners. Manufacturers extensively use this type in the fabrication of boxes, frames, etc. Closed corner joints have pointed edges. It is used on light sheet metal where less strength suffices at the joint.
In open corner joints, the inner points of the two metal pieces attach and the outer points do not connect. So, there is a square-shaped open space at the corner. Open corner joint is best for heavier sheets of metals.
Welding forms pretty strong joints. The filler metal is stronger than the base metal. Usually, the joint is as strong or stronger than the base metal. However, welding always contains a heat-affected zone. It is the zone near the weld joint that has undergone molecular changes due to the application of extremely high temperatures.
The changes in the HAZ are undesirable. These changes make the heat-affected zone the weakest part of welding. Besides HAZ, welding joints have some disadvantages as follows:
- Welded pipes need to go through several steps to get the desired shape.
- There are chances of defects in joint welding.
- If not properly welded, joints become prone to cracking.
- The defects in the weld joints are more dependent on the type of metal than the quality of the weld.
- Not all welding methods can be fully automatic.
- There is no way to mitigate the effects of welding on the mechanical properties, unlike bending.
- Welding takes a long time to learn and largely depends on the skill of the operator. The surrounding environment also plays an important role in the quality of the weld.
How Bending Works?
Bending is a process in which metal is bent to achieve the desired angle. The angle can be V-shaped, U-shaped, or curvature. Manufacturers use a brake or press brake to bend metals. Cornice brakes are good for making simple bends. A box and pan brake make more complex bends and shapes.
There are several types of bending in the metal industry. They are rolling, hot bending, induction bending, rotary-draw bending, etc. Rolling is a continuous bending process. In this process, the piece of metal is passed continuously through several rollers. Each roller bends the metal slightly. This method is ideal for long metal pieces.
Hot bending is pretty self-explanatory. In this process, the manufacturers apply heat to the metal until it becomes red and flexible. Then they apply mechanical pressure to bend directly. The method of heating the metal can be a flame, furnace, or something else.
In induction bending, the manufacturers apply heat locally using high-frequency electricity. After achieving a specific temperature, the piece of metal is moved through an induction coil and bending force is applied.
Rotary draw bending is like induction bending but without heat. It’s like rolling a string around a bobbin. The operator bents the metal against a spool-like thing whose radius matches the desired radius.
In every type of bending, the outer surface of the metal undergoes tensile stress and the inner surface undergoes compressive stress. The stress is way less than what the metal can withstand. As far as HAZ is concerned, there are no such zones in metal bending.
As you can see, all the types of bending above can be categorized into two major types; processes that involve heat and processes that do not. Why is that important? I will get into that in the latter part of this article.
Which is Stronger: Welding or Bending?
Welding is strong but it has some downsides. The filler metal has to be stronger than the base metal for the join to be stronger. There is a heat-affected zone in every welding. In that zone, the metal sees a change in mechanical properties due to the heat. This negatively impacts the strength of welding.
The strength of welding also depends on the welding technique and skill of the operator. As long as there is heat in the procedure, a certain amount of deformity in the joint is a must. That’s why there is a lot of post-processing and polishing in welding. Even then, the original strength of the metal is difficult to restore.
In fact, this is the only reason most of the time to prefer bending to welding. Because welding always involves heating, the alteration in the mechanical properties of the metal is inevitable. In bending, the metal is simply subjected to the bending procedure in a precise manner. As there is no heat involved, there is no chance of mechanical distortion at the molecular level.
For these reasons, welding joints are weaker than bending. Welding joints are prone to crack and break, unlike bent joints. One important thing to remember is that this can only be said for cold bending. Hot bending causes mechanical alteration in the process. You need to cool the metal slowly after hot bending to achieve desired strength.
Every metal has a different method and timing of cooling. If you cool the metal rapidly, or even the slightest mistiming in the cooling process can lead to massive degradation in mechanical properties.
If you are aware of the cooling process after hot bending, then there is nothing to worry about. In that case, bending, both cold and hot, is much stronger and more efficient than welding.
Some Benefits of Metal Bending Over Welding
There are many benefits to metal bending over welding. These are reasons why many prefer metal bending.
Feel free to take a look at these benefits:
- Metal bending is cheaper because it doesn’t require much labor in the process.
- Waste material is very little in metal bending because this process does not need any filler material and no part of the metal needs to be cut off.
- The metal bending process is computer controlled which makes it fast and precise.
- Metal bending produces high-quality and clean-looking products with excellent mechanical properties.
- Metal bending is time-saving which boosts productivity.
- If you have a smaller batch of products then bending is more cost effective than welding.
- Metal bending is fully automatic, unlike welding. This ensures that every product has a constant quality.
- Welding requires skill but so is bending. But operating the bending machine requires less expertise than welding. It is easier and faster to learn.
When it comes to Welding vs. bending, both have their pros and cons. But when it comes to the raw strength, metal bending is ahead. It also has several other benefits. These benefits, combined with mechanical strength, quality, and aesthetics, make a metal bending a way more competent candidate to make corner joints.
Thanks a lot for reading till the end and have a nice day!
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