EFFECT OF ADDING CARBON POWDER, ANTRACITE, AND WOOD CHARCOAL AGAINST THE HARDNESS OF AMUTITE STEEL IN THE PROCESS OF HEAT TREATMENT WITH MEDIA COOLING WATER, SEA WATER, ICE WATER AND OIL. SNPPM [Internet]. 2021 Dec. 24 [cited 2026 Aug. 26];5:5-8. Available from: https://journal.ubb.ac.id/index.php/snppm/article/view/2672