This Stainless Steel 660 has two important elements nickel and chromium. The chromium content is added to the steel to increase resistance to oxidation. The resistance ability increases as more chromium content. The nickel is added in high amount to form the most important class of corrosion and heat resistance. The effect of nickel to form austenite that leads to high strength and greater toughness. the alloy has also important elements is titanium. The main purpose of alloying elements in steel is for carbide stabilization