An Evaluation of the Mechanical Properties of Mn-Mo and Mn-Mo-Ni Steels

A study of the effects of normalizing and austenitizing on the mechanical properties of Mn-Mo and Mn-Mo-Ni steels is presented. It is shown that the quenched and tempered condition has superior notch toughness, elevated temperature tensile properties, and creep ductility than the normalized and tempered condition. The basis of comparison used for strength is the percentage of the room temperature strength. The creep strength and rupture resistance of the normalized and tempered condition are better than those of the quenched and tempered condition. Also, a comparison of the properties of the steels is made to evaluate the effects of a 0.5 percent Ni addition. While it improves hardenability, Ni tends to impair the elevated temperature creep strength and rupture resistance. Significant effects of Ni are seen on the elevated temperature tensile properties. The loss in ultimate tensile strength with increasing temperature is greater for the Ni modified grade than for the unmodified Mn-Mo. In the quenched and tempered condition, both yield strength and ultimate tensile strength are less affected by temperature when no Ni is added.