Goutam Mukhopadhyay

Cracking of a Tool Steel Guide Roller in a Bar Mill

Failure analysis of a guide roller used in a bar mill of an integrated steel plant has been presented. The guide rollers are positioned at the entry of rolling stands and act as guide in the multi-grooved pass for aligning the hot bars and hold the twisted oval bar while it enters a round pass. The hot bar is at a temperature of ≈1100°C, and the rollers are water cooled. The component is subjected to cyclic thermal stress depending on the mill operating conditions. The rollers are cracking longitudinally leading to failure. The investigation consists of visual inspection, chemical analysis, fractography, characterization of microstructures using optical and scanning electron microscopes (SEM), energy dispersive spectroscopy (EDS) analysis, and measurement of micro-hardness. The chemical analysis indicates the material as AISI D2 grade of cold work tool steel. Visual observation of the failed component shows multiple longitudinal cracks on the roller surface associated with a dark circular band of oxidation. The fracture surface shows a dark oxidized area propagating from the roller surface followed by flat bright appearance indicating final brittle fracture. Fractography of the dark surface from where the crack initiates shows fatigue striations. Microstructural examination under optical and SEM shows a network of coarse carbide particles at the grain boundary as well as uniformly distributed fine carbide precipitates within the martensite matrix. Multiple cracks are observed to initiate and propagate from the surface through the clusters of grain boundary carbides. EDS analysis and elemental mapping suggest the carbides to be chromium carbides. SEM shows micro-cracking of carbide particles associated with the crack. Clustered distribution of carbides deteriorates toughness and initiates cracking at the roller surface subjected to thermal cycling because of their differential thermal expansion coefficient leading to the failure of the component.

Failure Analysis of the Liner Plate of CDQ Chamber Made of AISI 310

Failure analysis of liner plate of coke dry quenching chamber was carried out. Crack as well as thinning was observed in the failed plate. Chemical analysis revealed that the liner plate was made of AISI 310 stainless steel. A sample of failed plate was studied under SEM to understand the metallurgical changes. Results showed severe intergranular corrosion near the crack and at thinned region of the failed plate. EDS analysis revealed the formation of chromium carbides along the grain boundary. EDS result also showed the presence of sulfur at the corroded portion. Findings revealed that the plate failed due to intergranular corrosion at elevated temperature; the presence of sulfur compounds aggravated the rate of corrosion.

Construction failures due to improper materials, manufacturing, and design

Abstract Various engineering components and equipment are used in the construction industry, be it large scale or small scale. The construction industry generally includes buildings, structures, roads, dams, bridges, and other industrial constructions like power generation, mills, manufacturing, and chemical plants. Several kinds of equipment like earth moving, material handling, and construction vehicle are used for different operations that are involved in any construction project, that is, excavation and digging of massive quantities of earth, compacting and leveling, transfer of materials and heavy loads, and placement of construction materials. Failure of these components or equipment in the construction industry causes fatalities, property loss, degrading of the company image or loss of credibility, and many legal issues; therefore, it is of great concern to the construction industry. The causes of failures can be categorized mainly as design deficiencies, material and manufacturing deficiencies, maintenance deficiencies, service abuse, and aggressive environment. Failure of some engineering components as well as accessories used in various construction industries, such as, beams, wire rods, foundation bolts, chains and hooks, wire ropes, conveyors, excavators, and cranes have been investigated to find out its root cause of failure. This chapter includes description of the different failures, visual details of the failed component, testing and characterization, root cause analysis, and recommendations to prevent recurrence of such failures in the future.

Failures of construction equipment and accessories: metallurgical root-cause analysis

Abstract Construction equipment and accessories are a vital part of any structural engineering works or infrastructural projects. Massive equipment and construction vehicles are involved in excavation and digging of huge quantities of earth, compacting and leveling, transfer of materials and heavy loads, placement of construction materials, and construction process. Sudden failure of these equipment and accessories is a serious concern as it causes damage of properties, increase in cost, delay in project, production loss, and even fatality in some cases. Therefore, root-cause analysis of these failures is of utmost importance to prevent their recurrence. These failures could be a result of inadequate design, faulty material and manufacturing, service abuse, poor equipment maintenance, or unskilled operations.

Metallurgical and Tribological Evaluation of Fe-Cr-C Hardfacing Alloys

Raw material handling areas in an integrated steel plant experience severe wear of engineering components. The use of hardfacing plates is one of the ways to combat this problem. Three commercial hardfacing Fe-Cr-C alloys of varying Cr content were deposited on mild steel base plate and studied in this work. Abrasive wear tests were conducted by using pin-on-disk tribometer in accordance with the ASTM G99. Microstructural characterization was done by using optical and scanning electron microscopes. Energy- and wavelength-dispersive spectroscopies were carried out to study the carbide type and distribution in the hardfaced deposit. It was observed that wear resistance increases with increasing Cr content in the alloy. Along with hardness, morphology and type of carbide are also important factors to decide the wear resistance. An attempt has been made to corelate the chemical composition, carbide morphology, and macrostructural features with wear properties of hardfacing alloys.

Correction to: Metallurgical and Tribological Evaluation of Fe-Cr-C Hardfacing Alloys

In the original article, Aman Kumar Jha was inadvertently omitted as a co-author.

Catastrophic Failure of a Steel Chimney in a Lime Plant

Failure analysis of a steel chimney used in a lime plant was carried out. The chimney broke from two different locations during a storm. During the site visit, it was observed that the chimney was dislodged from weld joints. The chimney was made up of hot rolled mild steel plates. Investigations were carried out on the failed chimney plate and welding between plates. The investigation consists of visual observation, chemical analysis, characterization of macro- and microstructures, measurement of hardness, tensile property tests and energy-dispersive spectroscopy (EDS). Calculation of wind load at the location of breakage was also carried out. EDS analysis revealed entrapment of slag inside weld. Overall analysis suggested that the failure took place due to selection of improper reconditioning technique as well as poor workmanship in welding.

Failure Analysis of a Chain Link Used in Charger Drive of a Coke Oven Battery

Failure analysis of a chain link of charger drive in a coke oven battery has been presented. The chain facilitates the charging of stamped coal cake (about 25 tons) into the oven through charger plate with its drive mechanism. The chain failed during service due to the breakage of a pair of link plates from the pin-hole location. The failure investigation consists of visual observation, fractography, compositional analysis, microstructural characterization, scanning electron microscopy, energy-dispersive spectroscopy (EDS), and mechanical characterization like hardness, tension, and impact tests. Fractography confirmed initiation of fatigue crack (primary failure) from a surface defect present at the edge of the pin hole; other fracture surfaces exhibited brittle nature. Microstructural examination and EDS analysis at the location of surface defect on the link plate reveal the presence of manufacturing defect which originated at slab stage in the casting-rolling route of plate manufacturing. The link plates are made by slitting of plates manufactured via hot rolling of steel slabs. The presence of grain boundary as well internal oxidation suggests that the defect originated at the slab stage before hot rolling.