Vanadium (V)
Vanadium forms very stable carbides and nitrides in steel. These fine particles block grain growth at high temperatures and keep the structure fine-grained. This increases strength and toughness, but too much vanadium makes the steel hard and prone to cracking.
Vanadium is an important alloying element in fine-grained structural steels. It forms fine carbides and nitrides that inhibit grain growth and increase strength without ruining toughness. That's good for welding because the heat-affected zone doesn't become coarse-grained so quickly. But be careful: too much vanadium makes the material harder and more susceptible to cold cracking. Especially during multi-layer welding or stress-relief annealing, precipitates can form that embrittle the structure. Then the heat-affected zone can tear. So always check the material certificate for how much vanadium is in it. Match the filler metal to the base metal and control the heat input. If you anneal, avoid the critical temperature range where carbides precipitate. After welding, you can check hardness – if it's too high, something's wrong with your parameters.