Saad Al-Motham
SABIC Technology Center
Saudi Arabia
Title: An assessment of the effects of varying martensite layer depth on the mechanical properties of quenched and self-tempered steel rebars
Biography
Biography: Saad Al-Motham
Abstract
After rolling quenched and self-tempered (QST) steel rebars, high water pressure is applied on the bar resulting in a martensite ring formation on the rebar surface. Subsequently, the core of the bar transforms to a high temperature transformation product and the martensite layer is tempered by the heat flowing outwards from the core. The combination of these two macro-constituents determine the overall mechanical properties of the bar. The depth of the martensite layer is an important material design parameter determining important material characteristics such as TS/YS ratio which is becoming increasingly of interest. A novel procedure to assess the relationship between the martensite layer depth and mechanical properties is devised in this work. Using industrially supplied QST rebars, a series of cylindrical samples of decreasing diameters have been prepared. By machining the samples to gradually decreasing diameters, the martensite ring is gradually removed until samples with only the core structure are obtained. Tensile testing is performed for all samples, therefore, enabling the assessment of varied martensite thickness effects on the mechanical properties of the overall rebar. The correlation between the amount of tempered martensite and yield strength, tensile strength, TS/YS ratio, elongation, reduction in area are characterized and quantified using this procedure.