Cov ntaub ntawv muaj cov pa roj carbon, manghologes, phosphorus, sidfur, sillicon, tooj liab, chromium, molybdenum thiab vanadium nyob rau hauv nws cov muaj pes tsawg leeg. Txij li thaum lwm cov ntaub ntawv yog tsawg dua 1% ntawm cov lej, cov no yog hu ua cov pa roj carbon hlau.