The study of metals is metals. Welding Metallurgy is the study of how welding affects the microstructure of metals. Did you know that there are metallurgists who dedicate their lives to studying only carbon steel? So what about all the other metals like stainless steel, nickel alloys, aluminum, magnesium, titanium, cobalt and copper alloys? Metallurgy is such a deep and mysterious subject that it would take a lifetime to fully understand carbon steel to the exclusion of everything else. So if it’s such a deep subject, what are the chances of a welder understanding enough metallurgy to be a good welder.
There is good news. And it doesn’t look like I’m saving much money on my car insurance by switching to GEICO.
The good news is that you don’t have to understand everything about economics.
You just need to understand a few basic principles. The most important thing to understand is that metals are affected by the heat produced by melting. It sounds so simple but it is profound. why? Because heat affects different metals in different ways.
If you heat a piece of metal news, and then submerge it in a bucket of cold water, what do you think will happen? If you answered “difficult”, you missed only part of it. Some metals are hardened by rapid heating and cooling. Most other metals behave quite differently. Carbon and low alloy steels such as 4130, machine steels, cast iron, and such 400 series stainless steels are hardened by rapid cooling from red heat. However, other stainless steels, nickel alloys, aluminum, magnesium, titanium, cobalt and copper alloys melt and lose their properties again due to hot heat and rapid cooling.
So what does this mean for your welder?
When welding 4130 chromo, you must be careful not to cool the weld too quickly or it will harden.
If you are welding 6061 t6 aluminum, you must be aware that the weld point will cool if it is too hot, and strength will be lost and not regained unless full heating is achieved.
Welding 301 fully hardened steel is easy, but the heat of the weld recrystallizes the hardworking microstructure and strength and durability go right out the window.
304 stainless welding can cause carbon and chromium to bond and form chromium carbides if the weld zone gets too hot.
So you got the picture. Temperature affects different metals differently.
Welding Metallurgy studies exactly how the heat of welding affects metals and if your welder takes the time to study metallurgy, the knowledge you gain will improve you.