Abstract
A chromium-containing corrosion-resisting steel, provisionally designated SX 3 CR 12 (Patent application SA 78/4764), has been developed from AISI 409 grade in the laboratories of Southern Cross Steel, South Africa. Optical and electron microscopy have established the microstructures and recrystallization characteristics of the steel after heat treatments between 600° and 900°C and, in addition, the morphology and composition of impurity particles have been investigated. Hardness and tensile properties of the alloys have been measured at room temperature as a function of similar prior heat treatments and, in addition, elevated-temperature tensile tests (room temperature to 900°C) have been carried out. Studies have been made of the impact and forming properties of the alloys, and the structure and properties of welds have also been determined. The investigation indicates that the very fine stable microstructure of the alloys, which is derived from the duplex elevated-temperature microstructure, provides attractive mechanical properties combined with adequate corrosion resistance and weldability.
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