Evaluation of the corrosion and mechanical properties of a range of experimental CrMn stainless steels

Abstract

In this resumed investigation, the effectiveness of manganese as an austenite-forming element in 17% and 20% chromium stainless steels has been investigated. The effect of manganese on the corrosion and mechanical properties of a range of experimental, low-cost, manganese-containing, dual-phase stainless steels is evaluated and reported.Metallographic examination and image analysis of the alloys revealed that manganese contents of up to 9%, in both 17% and 20% chromium alloys, are effective in producing a dual-phase structure comprising ferrite and austenite/martensite. It was found that manganese acts as an austenite-forming element under the conditions of the investigation.Mechanical testing of the alloys included hardness, tensile and Charpy impact testing. The results of the hardness testing showed that a 1050 °C normalizing treatment, followed by a 600 °C heat treatment and water quenching, resulted in alloys in their softest condition. It was found that manganese additions increased the toughness of the stainless steels, while tensile testing revealed that manganese additions increased the ultimate tensile strength of the alloys, but had little effect on the yield strength.The addition of manganese was found to reduce both the general and pitting corrosion resistances. Under reducing conditions, manganese additions resulted in a dramatic deterioration of the corrosion properties of the alloys.