Los ntawm nruab nrab ntawm lub xyoo pua 20th, ib lo lus tshwm sim hauv kev tshawb fawb tshuaj - hlau ntawm qhov tseem ceeb. Nws txhais tau hais tias ib pawg ntawm cov ntsiab lus uas nws lub cev muaj zog ua rau nws siv tau rau hauv kev tsim cov tub rog-kev lag luam complex. Peb tab tom tham txog cov hlau xws li chromium, tantalum, niobium, molybdenum thiab tungsten. Vanadium, uas nws cov khoom peb yuav xav txog hauv tsab xov xwm no, kuj muaj cai nyob hauv ib qho chaw hauv nruab nrab ntawm cov hlau siv nyob rau hauv niaj hnub engineering, ferrous metallurgy