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One thing a lot of welders sometimes talk about is the strongest weld out there. They’re really talking about the best welding joint. At face value, this sounds like a trivial topic, but there are many circumstances wherein the best type of weld matters. In fact, when you think about it, the strongest joint you can do ensures the quality of the weld as well as the strength of the material you’re doing.
Many welders don’t use all types of welding. A typical welder would focus on a few types of joints, depending on his usual tasks, even though he knows virtually all types of welds. Nonetheless, seasoned welders know that some welds are stronger than others. That doesn’t mean that the lesser types are necessarily weaker and less useful. Each type of welding has its unique purpose. It’s important to remember that to be able to make strong welds you need a good machine, read our Esab Rebel Review to see if it is the right choice for you.
Strength: A Relative Term
An argument can be made for welding in terms of the strength of the pieces of metal being held together. In other words, the joint is just as strong as the materials being joined. However, sometimes the resulting weld is stronger than the pieces joined together. One reason is because the process of welding changes the properties of the edges of the metals being joined together.
Essentially, it’s hard to answer the question about the strongest weld there is for a number of reasons. One reason is the varying operational definition of strength. Strong in what sense? Does it mean resistance to stress or material fatigue? Does it mean durability? Does it mean resistance to extreme temperatures? Materials can be strong in one regard and not so in another. Just because something yields to axial stress sooner than another material, that doesn’t necessarily mean it’s weaker.
Factors that Affect Weld Strength
Since we’re trying to make rational comparisons, it’s time to talk a bit about the parameters that determine the strength of the welded joint (1).
- Length of the weld
- Size of the weld
- Filler material used
In other words, if you make separate welds of the same length and size and the same filler metal, you’ll come up with welds of more or less similar strengths. Nonetheless, complete joint penetration welds with the same weld lengths have roughly similar strengths even if they are made from different processes as long as the filler metals used have the same tensile strengths.
Some welders may argue that welding that requires more power and higher temperatures results in more robust joints. The physics behind this is that materials under extreme heat cool down more slowly, hence resulting in a weld that’s stronger and more ductile. But while this is true for carbon steel, it’s not true for other types of materials.
Tensile Strength
Tensile strength is a term you often hear in your physics class. It’s the maximum stress (i.e. stretching or pulling force) a material can handle before breaking.
The filler metal you use partly determines how strong your weld is. Filler metal is the electrode used in welding. As it melts, the filler metal is deposited along the edges of the metals being joined and forms the weld bead.
The American Welding Society has specified the tensile strengths of electrodes or filler metals. Basically, you want a filler metal whose tensile strength is close or equal to the tensile strength of the base metal. So if the tensile strength of the base metal is 70,000 psi, you need a filler with the same tensile strength. Otherwise, the resulting weld is weak. One issue with regard to choosing a filler metal is it’s not always easy. Nonetheless, AWS has structural codes that specify filler metals for industrial applications.
Okay, so what’s the strongest weld?
A lot of welders will agree that tungsten inert gas (TIG) welding creates the strongest weld. Also called GTAW welding, TIG welding results in clean and robust welds due to high deposition efficiency. That means more of the electrode is deposited to the weld joint. In contrast, stick welding produces a lot of spatter that reduces the deposition efficiency. This is why TIG welding has numerous industrial, automotive, and aeronautic applications. The drawback of TIG welding is it requires expertise.
Anyway, just because TIG welding creates the strongest joints, that doesn’t mean the other types of welds aren’t strong enough. MIG or stick welding produce weld joints that are fairly strong for their specific purpose and should suffice typical welding applications.
Conclusion
Weld strength is sometimes a vague concept, considering different types of welds are and should be strong for the purpose they serve. Factors like weld length and size and filler metal used determine the strength of the weld joint. For purposes of answering the question, TIG welds are possibly the strongest in the industry, but other types of welds should be sufficiently strong.
Welding is a dangerous occupation. See our Best Welding Respirators page for recommendations on respirators to keep you safe.
