I roto i te tikanga ki te whakapai ake etahi āhuatanga o te maitai, me te kia whiwhi etahi āhuatanga motuhake i roto i te tukanga whakarewa i āta tāpiri huānga i huaina koranu huānga. Ko nga mea whakauru noa he chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, silicon, ...
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