To eliminate effects of nitrogen in the heat-affected zone when using HSLA steels, which element is added up to 0.025%?

• A. Vanadium up to 0.05%
• B. Niobium up to 0.02%
• C. Manganese up to 0.10%
• D. Titanium up to 0.025%

Answer: (D)

Nitrogen in the heat-affected zone can cause grain growth and reduced toughness during welding of HSLA steels. To counter this, a strong nitride-forming element is added so it binds nitrogen as stable nitrides, which slows or stops the grain coarsening that occurs in the HAZ. Titanium is particularly effective because it forms TiN particles that pin grain boundaries and keep the grain size finer during welding. Adding titanium up to about 0.025% provides enough Ti to sequester nitrogen and improve HAZ toughness without overdoing the alloying. That’s why this option is the best fit. Vanadium and niobium can produce nitrides too, but the specified limit here aligns with titanium’s role, and manganese doesn’t address nitrogen in the HAZ in the same way.