A number of rotating blades in a diffuser at a sugar beet processing plant fabricated from rectangular bars cut from rolled carbon-manganese steel plate fractured brittlely. However, apparently identical blades underwent significant plastic deformation without fracture. Inspection of both fractured and bent blades revealed similar preexisting cracks at the toes of bar attachment welds. Metallographic examination of the bent and the fractured bars revealed they had been cut parallel and transverse, respectively, to the rolling direction of the steel plate. Due to the combined effects of the low fracture toughness of the plate on planes parallel in the rolling direction, the presence of the preexisting cracks, and the relatively large section thickness of the bars, the bars whose lengths were transverse to the rolling direction fractured brittlely when subjected to impact loads. Had the poor transverse properties of thick-section plate been recognized, and all the bars properly cut with respect to the rolling direction, the premature fractures would not have occurred.

A steel lifting eye, manufactured from grade 1144 steel, failed during service. The eye ring fractured in two places, adjacent to the threaded shank and diametrically opposite to this region. Woody overload features, typical for resulfurized steels were revealed by SEM. The directionality of the features was found to be suggestive of shear overload. It was observed that fracture preferentially followed the nonmetallic inclusions. The fracture was revealed to be parallel to the direction of the manganese sulfide stringer inclusions. The presence of significant banding of the ferrite and pearlite microstructure was revealed by etching. It was also observed that the fracture is primarily along the inclusions and through bands of ferrite. It was concluded that the lifting eye failed as a result of overload. Fracture occurred parallel to the rolling direction, through manganese-sulfide stringers and ferrite bands in the base metal matrix. The material used for this application was very anisotropic, exhibiting substantially poorer long and short transverse mechanical properties than longitudinal properties.

A number of failures involving carbon and alloy steels were analyzed to assess the effects of inclusions and their influence on mechanical properties. Inclusions, including brittle oxides and more ductile manganese sulfides (MnS), affect fatigue endurance limit, fatigue crack propagation rates, fracture toughness, notch toughness, and transverse tensile properties, and do so in an anisotropic manner with respect to rolling direction. Significant property anisotropy has been documented in the failures investigated, providing evidence that designers failed to account for it. Typical fracture morphologies observed in such cases and metallographic appearances of MnS-containing materials are illustrated.

The locking collar on a machine failed suddenly when the shaft it restrained was inadvertently subjected to an axial load slightly higher than the allowable working load. The locking collar fractured abruptly, producing four large fragments. This allowed the shaft to be propelled forcefully in the direction of the load, causing substantial damage to other machinery components in the vicinity. The failed component, which was 43 cm (17 in.) in diameter, was machined from 4140 plate and heat treated to 34 to 36 HRC. Analysis (visual inspection, composite micrographs, scanning electron microscopy, and mechanical-property analysis) supported the conclusions that the alloy steel plate used in this application contained significant brittle microstructural fibering or banding. This condition produced considerable anisotropy in ductility and toughness as revealed by mechanical testing. Unfortunately, the potential effects of anisotropy were apparently neglected when this component was designed and manufactured from the plate stock, because the loading was applied in a direction that stressed the weakest planes in the material, that is, a direction normal to the fibering. No recommendations were made.

A metallurgical failure analysis was performed on pieces of the cracked vent header pipe from the Edwin I. Hatch Unit 2 Nuclear power plant. The analysis consisted of optical microscopy, chemical analysis, mechanical Charpy impact testing, and fractography. It was found that the material of the vent header met the mechanical and chemical properties of ASTM A516 Grade 70 carbon-manganese steel material and microstructures were consistent with this material. Fracture faces of the cracked pipe were predominantly brittle in appearance with no evidence of fatigue contribution. The NDTT (Nil ductility Transition Temperature) for this material was approximately -51 deg C (-60 deg F). The fact that the material's NDTT was significantly out of the normal operating range of the pipe suggested an impingement of low temperature nitrogen (caused by a faulty torus inerting system) induced a thermal shock in the pipe which, when cooled below its NDTT, cracked in a brittle manner.

Routine magnetic-particle inspection revealed crack indications in a number of shafts produced from hot-rolled 4130 steel bar. A pronounced indication of this size is cause for rejection if the defect is not eliminated during subsequent machining. A microstructural analysis of the shaft cross section revealed that the crack was approximately 0.5 mm (0.020 in.) deep and oriented in a radial direction. Furthermore, no stringer-type nonmetallic inclusions were observed in the vicinity of the flaw, which did not display the intergranular characteristics of a quench crack. The defect did, however, contain substantial amounts of oxide, which evidently resulted from the hot-working operation. This evidence supports the conclusion that the appearance of this discontinuity, with the long axis parallel to the working direction and radial orientation with regard to depth, strongly suggests a seam produced during rolling. Use of components with surface-defect indications as small as 0.5 mm (0.02 in.) can be risky in certain circumstances. Depending on the orientation of the flaw with respect to applied loads, the nature of the applied forces (for example, cyclic), and the operating environment, such a surface flaw can become the initiating site for a fatigue crack or a corrosion-related failure.

A support arm on a front-end loader failed in a brittle manner while lifting a load. The arm had a cross section of 50 x 200 mm (2 x 8 in.). Material used for the arm was hot-rolled ASTM A572, grade 42 (type 1), steel, which exhibited poor impact properties in the as-rolled condition and had a ductile-to-brittle transition temperature exceeding 93 deg C (200 deg F). This transition temperature was much too high for the application. It was recommended that a modified ASTM A572, grade 42 (0.15% C max), type 1 or 2, steel be used (type 1, which contains niobium, may be needed to meet strength requirements). The steel should be specified to be killed, fine-grained, and normalized, with Charpy V-notch impact-energy values of 20 J (15 ft·lbf) at -46 deg C (-50 deg F) in the longitudinal direction and 20 J (15 ft·lbf) at -29 deg C (-20 deg F) in the transverse direction.

This paper describes the superplastic characteristics of shipbuilding steel deformed at 800 °C and a strain rate less than 0.001/s. After the superplastic deformation, the steel presents mixed fractures: by decohesion of the hard (pearlite and carbides) and ductile (ferrite) phases and by intergranular sliding of ferrite/ferrite and ferrite/pearlite, just as it occurs in stage III creep behavior. The behavior is confirmed through the Ashby-Verrall model, according to which the dislocation creep (power-law creep) and diffusion creep (linear-viscous creep) occur simultaneously.

Several cases of failures in gray cast iron paper machine dryer rolls were evaluated. The rolls were found have ground outer cylindrical surfaces on which the paper web is dried. They were found to rotate about their longitudinal axes at speeds from 50 to 250 rpm while containing saturated steam from 35 to 380 kPa. Failures were found to occur in the shell body, in a head near a hand hole or a manhole opening, or in a head near the journal-to-head interface. A cleavage fracture was revealed by scanning electron microscopy regardless of the driving stress for failure. Fracture surface were found to exhibit chevron marks typical of fatigue or raised points or tears pointing in the direction of the probable origin of failure. The characteristics of the thinwall cast iron structures like the variation in composition due to pouring from multiple ladles, variation in solidification rates, and variation in tensile strength to be noted during inspection were described.