Failure Analysis of Work Rolls of a Thin Hot Strip Mill

A new interesting article published in « Case Studies in Engineering Failure Analysis »

In hot rolling mills, premature failure of rolls is a major concern as it adversely affects the mill operation and as well as production. Analysis of failed roll materials and actual rolling conditions in service are therefore necessary to understand the roll failure mechanism and thereby improve the wear resistance and extend the service life of rolls.

This work describes two different types of roll failure cases and their analysis which was carried out using destructive as well as non-destructive testing techniques (NDT). The cases are as follows:

(a)

Case I: Enhanced ICDP Bottom roll of fifth stand (F#5) which failed from the neck portion.

(b)

Case II: Analysis of sub-surface defect of ICDP rolls of the last stand (F#6

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Failure analysis of work rolls of a thin hot strip mill

A new case study of failure analysis published on Sciencedirect.com

In hot rolling mills, premature failure of rolls is a major concern as it adversely affects the mill operation as well as production. Analysis of failed roll materials and actual rolling conditions in service are therefore necessary to understand the roll failure mechanism and thereby improve the wear resistance and extend the service life of rolls.

The hot strip mill referred here consists of six stands wherein high chromium (Hi-Cr) iron rolls and Indefinite Chilled Double Poured (ICDP) cast iron rolls are being used for finishing rolling of the strips in the last two stands. The thin strip mill produces strips in the thickness range of 1.0–12.7 mm. This work describes two different types of roll failure cases and their analysis which was carried out using destructive as well as non-destructive testing techniques (NDT).

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Fissure sur une drague du port autonome de Nantes-St-Nazaire

Une fissure importante découverte sur la drague André Gendre du Port Autonome de Nantes Saint-Nazaire a obligé les équipes techniques à réagir vite lors de sa mise à sec. Elles ont fait appel au Cetim.
Pour en savoir plus, lire l’article en cliquant ici

 

Failure analysis of Co–Cr hip resurfacing prosthesis during solidification

A paper published on january 2013 in « Case Studies in Engineering Failure Analysis« .

In this study a failure originated during solidification process into the femoral stem component of Hip Resurfacing prosthesis was investigated.  The results exhibited hot tearing, shrinkage porosity and metal oxide films due to inadequate heat dissipation during solidification process, as a consequence of poor investment casting ceramic mold configuration. Also in this paper was improved the casting design solving this kind of defects.

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Failure analysis on unexpected wall thinning of heat-exchange tubes in ammonia evaporators

ScienceDirect.com publishes a new « Case Studies in Engineering Failure Analysis« .

A failure incident of heat-exchange tubes in ammonia evaporators, which suffered from unexpected wall thinning after only one-year service with respect to their original design lifetime of fifteen years, was reported and carefully analyzed. The analysis results demonstrated that the unexpected wall thinning of tubes was primarily ascribed to multiple corrosion factors including uniform corrosion, pitting and interaction behavior between them. Relative failure mechanisms were discussed in detail and prevention measures were also proposed for ammonia evaporators under similar operating condition.

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Failure analysis of the pulleys during the press-fit assembling process

A new case studie in engineering  failure analysis published on SienceDirect.com. The present article highlights failure investigation of the pulleys during a press-fit assembling process. Pulleys are used to transmit power between rotational mechanical elements.  It was found that cooperative influence of higher carbon content with combination of elongated sulphides is reason for pulleys cracking. Steel cleanliness and homogeneous structure is an important factor for users of steel. The success of production process is connected with the optimal quality of steel.

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Surveillance en service des éoliennes

Les éoliennes au banc d’essai.

20 % de l’énergie consommée devrait provenir des énergies renouvelables d’ici à 2020. Selon les projections du Grenelle de l’environnement, la moitié de cette énergie devrait être fournie par l’éolien. Autant dire que la fiabilité des équipements constitue un enjeu majeur. Qui plus est, la moindre casse ou défaillance génère des coûts très importants. Un fait qui s’explique par les conditions particulières d’exploitation (chaîne cinématique complexe pour la surveillance, conditions de fonctionnement aléatoires et sévères en termes de température ou d’accessibilité, faible rigidité de l’ensemble, etc.). Le Cetim a donc décidé de développer des outils permettant de surveiller en temps réel l’état de santé d’une machine tournante afin d’assurer une maintenance prévisionnelle de ce type d’équipement. En s’appuyant sur les développements des grands projets mécatroniques* (Adeolys, Kastrion, Supreme), il s’agit de définir les moyens permettant de prévoir la durée de vie résiduelle des équipements en prenant en compte le cumul de charge et l’environnement vibratoire. Les défauts et dysfonctionnements seront ainsi détectés au plus tôt… et l’information devra ensuite être fusionnée avec l’estimation de la durée de vie. Pour parvenir à ce résultat, le Cetim a conçu et réalisé un banc d’essai qui reproduit la chaîne cinématique d’une éolienne à l’échelle 1/100e  en termes de puissance et qui fonctionne à vitesse variable. Ce banc comporte un moteur à chaque extrémité. L’un sert à simuler le vent qui entraîne l’hélice, l’autre représente la génératrice.

*Le banc d’essai est ainsi déjà utilisé pour mener à bien trois projets.

  1. Adeolys. Projet destiné aux essais d’endurance.
  2. Kastrion. Programme axé sur la validation d’un nouveau système de surveillance.
  3. Supreme. Action destinée à la création de nouveaux outils de maintenance prédictive.

Pour plus d’information rendez-vous sur le site du Cetim où contactez le service Question-Réponse

Observing early stage rail axle bearing damage

Railway bearingA paper presented   at the Sixth International Conference of Engineering Failure Analysis on July 2014 in Lisbon – Protugal. This paper brings out the detail of investigation carried out on failing  rail axle bearing.

A novel condition monitoring system has for the first time enabled reliable extraction from service and detailed forensic examination of failing rail axle bearings, before the usual catastrophic destruction of the evidence. Computed Tomography has been used to produce a map of the damage allowing targeted sectioning of subsurface cracking. Traditional metallographic techniques have revealed large white etched layers associated with the subsurface cracking, while observations with a scanning electron microscope have confirmed rolling contact fatigue crack propagation, possibly initiated from pre-existing electrical arcing damage of the raceways.

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Reduction in diversion due to coil break in CRNO grades of coils

A new « Case study in Engineering Failure Analysis » published on ScienceDirect.com.

This paper reports investigations after diversion due to coil break in cold rolled non oriented (CRNO) grades of coils showed an increasing trend during Jan–May’12 at Silicon Steel Mill (SSM), Rourkela Steel Plant (RSP). Coil break increased from a level of less than 1% during to a level of 30% in May’12. Samples from hot rolled coils and finished coils were taken and detailed metallurgical investigation was carried out to ascertain the genesis of such defects. Further studies were carried out in the processing lines and material flow was tracked from steel making to final product. The probable reasons were identified and corrective measures were taken leading to reduction in diversion due to coil break less than 2%.

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Fracture mechanisms of failed IN-738LC gas turbine blades

An interesting  paper in « Case study in Engineering Failure Analysis » published on ScienceDirect.com. This paper outlines the problem of blades failure occurred because of excessive temperature exposure. Nickel based superalloys are widely used as gas turbine blade material. They suffer from microstructural instabilities and environmental damages. Creep properties of alloy was deteriorated by γ‘ particles dissolution.

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