A 2.3 mm diam steel wire broke during cable twisting. The fracture occurred obliquely to the longitudinal axis of the wire and showed a constriction at the end. Therefore it was a ductile fracture. File mark type work defects were noticeable on the wire surface at both sides of the fracture, but they had no effect on the breakage of the wire. Away from the fracture area, the wire had a normal structure of hyperfine lamellar pearlite (sorbite) of a “patented” and cold drawn steel wire. In the vicinity of the fracture, the cementite of the pearlite was partially spheroidized, while at the fracture itself it was completely spheroidized. Therefore the wire was locally annealed at this point. It was likely that the wire cracked at this point during the last drawing and then broke during twisting due to its lower strength in the weakened cross section after prior deformation.

Gross wastage and embrittlement were observed in plain carbon steel desuperheaters in five new Naval power plants. The gross wastage could be duplicated in laboratory bomb tests using sodium hydroxide solutions and was concluded to be caused by free caustic concentrated by high heat flux. The embrittlement was shown to be caused by the flow of corrosion generated hydrogen which converted the cementite to methane which nucleated voids in the steel. A thermodynamic estimate indicated that a small amount of chromium would stabilize the carbides against decomposition by hydrogen in this temperature range, and laboratory tests with 2-14% Cr steel verified this.

Six wrist pins in a high-performance six-cylinder automotive engine failed after 4800 km (3000 mi) of normal operation. The pins were made of low-carbon steel that had been carburized both inside and outside. Two failed pins were examined. One had fractured into three pieces. The other had not fractured, but exhibited circumferential cracks on the surface of the central zone. Visual surface examination and metallographic and chemical analyses were performed on the specimens. Cracking was attributed primarily to poor heat treatment, resulting in a brittle grain-boundary network of cementite, and to a design that had a raised central section of the inner diameter whose fillets were locations of high stress concentration. Rough machining of the inner diameter and an excessively deep case also contributed to failure. A double type of heat treatment after carburizing and change of the design to eliminate the raised central section were recommended.

A failed SAE-192 carbon steel tube from a 6.2-MPa (900-psig), 200-Mg/h (180-ton/h) capacity refinery boiler was analyzed to determine its failure mode. Optical and SEM examination results were combined with knowledge of the boiler operating conditions to conclude that the failure was hydrogen-induced. The hydrogen was probably generated by the steam-iron reaction. The source of steam on the flue gas side could be traced to a cracked fillet weld in the boiler The failure mode was unusual in that the attack was found to originate from the flue gas side of the tube rather than the steam side.

Pipes made of low-carbon Thomas steel had been welded longitudinally employing the carbon-arc process with bare electrode wire made for argon-shielded arc welding. Difficulties were encountered during the cutting of threads because of the presence of hard spots. Microstructural examination showed welding conditions were such that a carburizing atmosphere developed, which led to an increase in carbon content and hardening at certain locations such as terminal bells and lap joints. This explained the processing difficulties during the threading operation.

The right front spring hanger on a dual rear axle of the tractor of a tractor-trailer combination failed, causing the vehicle to roll-over. The hanger was made from malleable cast iron that had been heat treated to produce a decarburized surface layer and a pearlitic transition layer. It had been repair welded after breaking into two pieces longitudinally in a prior incident, using cast iron as weld metal. The repair weld bead on both surfaces missed the fracture over 15 to 20% of their lengths. The incomplete repair weld and brittleness of the weld metal and heat-affected zones led to the failure.

Sucker-rod pumps are operating in very aggressive environments in oil well production. The combined effect of a corrosive environment and significant mechanical loads contribute to frequent cases of failure of the rod string during operation. Standards and recommendations have been developed to control and avoid those failures. This study presents various failure cases of sucker rods in different applications. The heat treatment of the steel material and the resulting microstructure are an important factor in the behavior of the sucker rod. A spheroidized microstructure presents a weaker resistance to corrosion affecting the rod life. Non-metallic inclusions are a pitting preferential site leading to fatigue crack initiation. Heterogeneous microstructure as banded martensite and ferrite/pearlite decreases the ductility of the material affecting the fatigue propagation resistance.

Failures of 10Cr-Mo9-10 and X 20Cr-Mo-V12-1 superheated pipes during service in steam power generation plants are described. Through micrographic and fractographic analysis, creep and overheating were identified as the cause of failure. The Larson-Miller parameter is computed, as a function of oxidation thickness, temperature and time, confirming the creep failure diagnostic.

In this study, the failure modes of cartwheel and mechanical properties of materials have been analyzed. The results show that rim cracking is always initiated from stringer-type alumina cluster and driven by a combination effect of mechanical and thermal load. The strength, toughness, and ductility are mainly determined by the carbon content of wheel steels. The fatigue crack growth resistance is insensitive to composition and microstructure, while the fatigue crack initiation life increases with the decrease of austenite grain size and pearlite colony size. The dynamic fracture toughness, KID, is obviously lower than static fracture toughness, KIC, and has the same trend as KIC. The ratio of KID/sigma YD is the most reasonable parameter to evaluate the fracture resistance of wheel steels with different composition and yield strength. Decreasing carbon content is beneficial to the performance of cartwheel.

A bolt manufacturer observed that products made from certain shipments of steel 41 Cr4 wire were prone to the formation of quench cracks in their rolled threads. The affected wire was tested and found to be highly sensitive to overheating because of the metallurgical method by which it was produced. A stronger decarburization of the case was a contributing factor that could not be prevented by working because the thread was rolled. Hardening tests conducted by the bolt manufacturer showed that quench cracks did not occur in specimens that were turned down before hardening and when notches were machined instead of beaten with a chisel.

Several back up rolls of 1400 mm barrel diam from a broad strip mill broke after a relatively short operating time as a result of bending stresses when the rolls were dismantled. The fracture occurred in the conical region of the neck at about 600 mm diam. The rolls were shaped steel castings with 0.8 to 1.0% C, 1% Mn, 1% Cr, 0.5% Mo and 0.4% Ni and were heat treated to a tensile strength of 950 N/sq mm. Because the bending stress on mounting was only 42 N/sq mm in the fracture cross section, it was evident at the outset that material defects had promoted the fracture. In the case of this roll and the other broken rolls, the cracking and fracture were promoted by various casting defects. Investigation of the rolls showed that both the breaking off of the neck and the disintegration of the barrel edges was caused by material defects, more exactly casting defects. The fractures on the other rolls examined were so badly rusted or contaminated that they were incapable of yielding any information.

Graphitization, the formation of graphite nodules in carbon and low alloy steels, contributes to many failures in high-temperature environments. Three such failures in power-generating systems were analyzed to demonstrate the unpredictable nature of this failure mechanism and its effect on material properties and structures. In general, the more randomly distributed the nodules, the less effect they have on structural integrity. In the cases examined, the nodules were found to be organized in planar arrays, indicating they might have an effect on material properties. Closer inspection, however, revealed that the magnitude of the effect depends on the relative orientation of the planar arrangement and principle tensile stress. For normal orientation, the effect of embrittlement tends to be most severe. Conversely, when the orientation is parallel, the nodules have little or no effect. The cases examined show that knowledge is incomplete in regard to graphitization, and the prediction of its occurrence is not yet possible.

The phenomenon of on-load corrosion is directly associated with the production of magnetite on the water-side surface of boiler tubes. On-load corrosion may first be manifested by the sudden, violent rupture of a boiler tube, such failures being found to occur predominantly on the fire-side surface of tubes situated in zones exposed to radiant heat where high rates of heat transfer pertain. In most instances, a large number of adjacent tubes are found to have suffered, the affected zone frequently extending in a horizontal band across the boiler. In some instances, pronounced local attack has taken place at butt welds in water-wall tubes, particularly those situated in zones of high heat flux. To prevent on-load corrosion an adequate flow of water must occur within the tubes in the susceptible regions of a boiler. Corrosion products and suspended matter from the pre-boiler equipment should be prevented from entering the boiler itself. Also, it is good practice to reduce as far as possible the intrusion of weld flash and other impedances to smooth flow within the boiler tubes.