<span><span>тугоплавкие металлы</span><span> — </span><span>вольфрам</span><span>, </span><span>молибден</span><span>, </span><span>ванадий</span><span>, </span><span>тантал</span><span>, </span><span>ниобий</span><span>, </span><span>хром</span><span>, </span><span>марганец</span><span>, </span><span>цирконий</span><span>;</span></span>