Black Friday: lifetime access is on a special offer in the app, until November 30. Black Friday: special offer on lifetime access, until November 30. Download
텅스텐철은 강철의 성질을 향상시키는 데 사용됩니다.teongseutencheoreun gangcheoreul seongjireul hyangsangssikineun de sayongdoemnida.Ferrotungsten is used to enhance the properties of steel.