INVESTIGATION OF FRACTURE PROPERTIES OF PHOSPHORIC IRON

Abstract

Phosphorus is traditionally known to be detrimental to the mechanical properties of steel and is therefore avoided. However, the beneficial effect of phosphoric iron in conferring corrosion resistance in attested by several archeological iron structure in India, one famous example being the 1600 year old Delhi iron pillar. The iron of the pillar contains am average amount of 0.25 wt % phosphorus. Therefore there was need for a detailed research on corrosion resistance of iron containing phosphorus. Iron- phosphorus alloys containing low amount of phosphorus are termed as phosphoric iron. The aim of the present thesis is to determine the mechanical properties and fracture behavior of phosphoric iron Phosphoric iron of two different phosphorus content, namely P1 (Fe-0.30P-0.226C), P2 (Fe-0.11 P-.028C) were first prepared by ingot casting route. The ingot were soaked and forged at 1150 °C. The microstructures of the phosphoric iron and its relevant mechanical properties such as hardness and tensile properties have been characterized. J-R curves of the material have been determined at room temperature. Fracture behavior under tearing load has been studied through fracture toughness tests on phosphoric iron using Compact Tension (CT) specimens of Width (VT) =50 mm and thickness (B) =12.5mm. J-R curves were obtained from specimens precracked to a/W 0.5 The single specimen unloading compliance method have been used for generating J-R curves. The initiation toughness Ji, obtained at the intersection of the blunting line and the power-law fit to the J-R curve, and the critical toughness JQ, determined following the procedure of the ASTM standard, were estimated. The results of fracture studies under loading infer: (a) phosphoric iron P1 (Fe-0.30P-0.226C) exhibits low fracture toughness at room temperature (b) phosphoric iron P2 (Fe-0.11P-.028C) exhibits high fracture toughness at room temperature.