Metallurgy is the science that explores why metals behave the way they do. It explains the properties, behavior and internal structure of metals. Metallurgy also describes the treatments and processes that allow us to tailor a metal’s properties to a specific application.
Metallurgy is a relatively broad and, at times, complex subject. Most welders do not need to be experts. However, all welders should have a good grasp on basic metallurgical principals. Why? Because welding involves the heating and cooling of metals, and the heating and cooling of metals affects the mechanical properties of the resulting part.
For example, carbon and low alloy steels like 4130, tool steel, cast iron, and some 400 series stainless steels, harden by quick cooling from a red hot temperature. But most other stainless steels, nickel alloys, aluminum, magnesium, titanium, cobalt, and copper alloys will actually soften and lose properties by heating up red hot and quickly cooling.
This is just a generalization. A welding procedure, technique, or filler metal may be entirely appropriate for one these materials and disastrous for another. In other words, you really have to be familiar with different types of base materials and how they are affected by heating and cooling processes in order to avoid lack of fusion, cracking, porosity, and other weld defects that can lead to mechanical failures and deadly disasters like the San Bruno pipeline explosion that killed 8 people in 2010.
Most welders come by their knowledge of metals and a metal’s weldability over many years on the job. However, this knowledge is often incomplete because it is limited to the processes and materials used in a particular shop or industry. A more complete understanding of metallurgical principles, such as the relationship between a metal’s properties and its composition, and the function of processes such as cold working, alloying, and heat treatments, will not only allow you to master the process and materials that he or she is accustomed to working with, but it will also allow you to take the next step in their career. Whether it’s welding space age alloys in the aerospace industry or becoming a Certified Welding Inspector, the future is in your hands.
Carlos Plaza
I am absolutely agree, I have the experience of work with many welders and they (generally) do not have enough knowledge about the impact of heat input on the steel.
I have 20 years of experience in welding technology, I was welder and instructor, now, I’m working as welding general supervisor, also I work through my own company. The point is; the welders do not have enough knowledge of metallurgy, but I know that with a good training process, we can to awaken the desire to learn more, to know more.
The welders need a didactic method to learn, the use drawings, good use of the words, not much “SCIENTIFIC TERMS”…well; this is my method and gives me very good results.
Mikayah Levi
I also agree while I am still a young man I have taken on task of welding in a machine shop where I weld not just only mild steel but exotics and castings. I had some metallurgy experience but find that daily my job is made easier by the more knowledge I can spounge in. I am daily learning something new and am always training myself with this ever evolving puzzle
So what are the points should the welders be aware about?
Aws kindly would give a lecture about that points in detail.
AWS has developed a metallurgy course that lays out the basic prerequisite knowledge (behaviour of atoms, properties of metals, crystal structure) necessary to understand how welding affects the properties of joined metals. AWS is currently working on a second online course that addresses the more advanced topics in welding metallurgy.
I so want to learn more , I’m 58 and been welding around 30 years or so and need to learn so much more on this subject.
It’s interesting to learn that even though they don’t need to be experts, it might be a good idea for welders to have a good idea on basic metallurgical principals. This makes sense because, like you said, there is a lot of heating and cooling and they need to know the affects it has on the mechanical properties. To me, this is why it is always good for them to know what might possibly happen to the material they are working with.