I actually have a whole list of things where the popular opinion is wrong. Here's an example that applies to almost no one here, but it might be interesting. And I have plenty more.
"Annealing." After welding high carbon steel, you have to "anneal" it. But you aren't actually annealing. If it's made of high carbon steel, it is hardened; that's why it's made of high carbon steel to begin with. And after welding it, you still want it to be hardened. The reason you are reheating it to cherry red is not to anneal it.
When you weld on this high carbon steel, you are hardening it (which is what you want), but you are exceeding the critical temperature by a large margin. When the steel cools (from air and the rest of the metal drawing the heat out) it hardens, but the excessive temperature increases the grain size, making the steel lose toughness. It is prone to cracking. If you wanted to make this steel softer, you could just temper it all the way to dead soft. But that wouldn't fix the grain structure.
When you reheat the steel to just slightly glowing, you are not doing it to soften or anneal the steel. You do it to re-harden the steel, properly. By heating it to just barely reach critical temp, the grain structure is fine as you can make it. When you harden steel (whether you quench it with oil or just let it air harden), you want to barely reach glowing, and it's best to do it indoors. In direct sunlight, you can't see where the steel starts to glow, and you will reach an excessive temperature by the time you can detect the glow. Like what happens when you weld on it.
This is not simply semantics. Because people think this is actually annealing/softening the steel, they think you don't have to temper the steel after. You don't have to do anything but die and pay taxes. But you should temper, because you didn't anneal the steel. You re-hardened it, properly. And it will still be suspect to internal stress fracture until it has been tempered.
Likewise, if you braze high carbon steel. You are re-hardening it. You didn't use excessive temp; you just barely got it beyond critical. So you don't have to anneal the steel, after. But you should still temper it.
Even if the result after annealing/brazing is softer than you would like, you should still temper. Otherwise the steel will be prone to spontaneous breakage after repeated bend cycles, even if you keep the bending in the elastic limit, well below the yield point of the steel.
The easy way to remember this is anytime you get high carbon steel to glow red, and you don't get the entire piece to glowing and then let it cool over a period of at least 12 hours in a sealed oven, you haven't fully annealed it. You will get various formations of steel. And if you let it cool fast enough, even by room temperature air, many alloys will harden to some degree (martensenite? formation) even without quenching. And whether or not it is softer than it was before, you still have residual stress in the newly formed martensenite and should temper it. But because in the english language we have to call everything backwards, we call this "annealing," even it cases where it's not.
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More forum related:
A lot of people on this forum know my pet peeve about aquarium bubbler "cupric chloride" etching.
But there's not too many electronics related things I can think of, where the general opinion is so wrong. I guess we're not that dumb, on average.