Cast irons containing graphite are formed under a metastable eutectic reaction. 2) ___ High carbon steels are easily welded. 3) ___ Hardenability refers to the ease with which a steel can be quenched to form pearlite. 4) ___ In the AISI system for designating steels, the first two numbers refer to the major alloying elements of the steel. 5) ___ Quenching hardens most steels while tempering increases the toughness.