Rolling Failure Research Articles

Finite Element Creep-Fatigue Analysis of a Welded Furnace Roll for Identifying Failure Root Cause

Creep-fatigue induced failures are often observed in engineering components operating under high temperature and cyclic loading. Understanding the creep-fatigue damage process and identifying failure root cause are very important for preventing such failures and improving the lifetime of engineering components. Finite element analyses including a heat transfer analysis and a creep-fatigue analysis were conducted to model the cyclic thermal and mechanical process of a furnace roll in a continuous hot-dip coating line. Typically, the roll has a short life, <1 year, which has been a problem for a long time. The failure occurred in the weld joining an end bell to a roll shell and resulted in the complete 360° separation of the end bell from the roll shell. The heat transfer analysis was conducted to predict the temperature history of the roll by modeling heat convection from hot air inside the furnace. The creep-fatigue analysis was performed by inputting the predicted temperature history and applying mechanical loads. The analysis results showed that the failure was resulted from a creep-fatigue mechanism rather than a creep mechanism. The difference of material properties between the filler metal and the base metal is the root cause for the roll failure, which induces higher creep strain and stress in the interface between the weld and the HAZ.

Furnace Roll Failure Analysis on Hot-Dip Coating Line Spurs New Design and Welding Process

Abstract A new design and welding process may extend the life of furnace rolls in hot-dip coating lines, which often fail in less than one year. This article is a case study of analysis of a failed furnace roll that led to a proposed improved design to extend component life.

Contact Deformation Analysis of Elastic–Plastic Asperity on Rough Roll Surface in a Strip Steel Mill

In this paper, the deformation behaviors of elastic–plastic asperity on rough roll surface in a strip steel mill were simulated by a three-dimensional finite element (FE) model. The asperity characterized a sinusoidal profile and all objects in the FE model were elastic–plastic with linear strain hardening. The deformation behaviors including contact stresses, strains (including elastic and plastic strains), and contact radii of different rolling force densities and different geometrical shapes and sizes were calculated and analyzed. It revealed that the tall-thin type asperity caused larger plastic strain in the asperity itself and larger Von Mises stress in the mating roll subsurface. Long-term repeated effects of large cyclic strain and stress were liable to spark subsurface cracks and increased the risk of fatigue failure of rolls in strip rolling mills.

Failure analysis of work rolls of a thin hot strip mill

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 1.0–12.7mm. 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).Destructive testing (including metallography and chemical analysis) was carried out on the failed roll samples in the first case and gross abnormality in microstructure was observed. Some foreign particle/entrapment was observed after dressing of the working surface of roll at 566mm diameter (initial diameter of roll was 620mm and scrap diameter was projected to be 540mm). The chemical composition of the particle was analyzed by a portable X-Ray Fluorescence (XRF) alloy analyzer and it was confirmed that the particle is basically a ferroalloy which was entrapped in the shell of the roll, probably during casting/manufacturing of roll.

Ribbon Fatigue Spalling of a Forged Work Roll Used at a Cold Rolling Mill

Catastrophic failure of a forged work roll used in a cold rolling mill was investigated. The spalled roll showed fatigue arrest marks in a smooth continuous path along the circumferential direction. Characteristic features of the fracture surface were similar to that of surface initiated spalling which is known as ribbon fatigue spalling. The investigation consisted of visual observation, profiling of crack using ultrasonic testing, microstructural characterization by optical and scanning electron microscopy, XRD analysis, and hardness measurements. Ultrasonic evaluation confirmed the initiation of root crack on the roll surface followed by an extensive sub-surface propagation (~815 mm length) of fatigue crack. Microstructural analysis revealed the presence of dendritic columnar structure and coarse irregular carbides indicating improper manufacturing process. Retained austenite content (~12%) as measured using XRD was higher than the usual desirable limit for such application. These microstructural abnormalities deteriorated the fatigue resistance of the roll. Since the roll failed within few hours of the running campaign and there was no operational abnormality reported in the campaign, it can be inferred that the initiation of the fatigue crack was conceived prior to the running campaign. It was an inspection deficiency that the crack was not detected prior to the start of the campaign. Initiation of fatigue crack which could not be detected during inspection led to the premature failure of roll in the early stage of campaign.

English

A number of 30 buffaloes with uterine torsion were described in a period of 2010 to 2011 in our clinic in Basrah Province Alnashwa. All animals were treated first by rolling but only four cases responded and were corrected by this method, 86.67% of cases were corrected by caesarian section (CS). We found that the right uterine torsion was more incidence 73.33% than left uterine torsion, from the result, we found 4 cases of uterine torsion with malprsentation. The fetus survivability after caesarian section was only 46.51%. The study concluded that caesarian operation in early diagnosed uterine torsion in buffaloes is the best method for saving the fetal and maternal life in case of rolling failure. Key words: Buffaloes, Basrah Province, uterine torsion.

Failure of high-chromium iron roll in compact strip production MILL

A high chromium (HiCr) iron work roll broke in three pieces in finishing stand 4 in a compact strip production (CSP) mill of a steel company. This roll breakage was examined by means of visual inspection, analysis of the mill process data, and chemical and microscopic analysis of a sample from the spheroidal graphite (SG) iron roll core. The roll broke due to inferior quality of the roll core. Due to strong contamination with chromium (1.5%), far above the limit for the CSP mill (max. 0.50%Cr), the core microstructure contained abundant millimeter-sized (Cr,Fe)-carbide clusters, leading to a poor impact toughness.The quality criteria in the test report were adequate, and depending on the data the mill put the roll in service. Unfortunately, the supplied roll contained incorrect data with respect to the chromium level (0.5%Cr) and to a lesser extent the Mo levels in the roll core after solidification. If the test certificate had shown the actual core composition, would have been rejected and the roll failure would have been prevented.The paper describes the causes of the roll failure manufactured from high chrome grade steel along with the precautionary measure.

Surface Wave Based Ultrasonic Technique for Finding the Optimal Grinding Condition of High Speed Steel (HSS) Work Rolls

AbstractOver the last few years, the use of work rolls for hot rolling of flat steel has been changed from clear chill rolls to indefinite chill, then high chrome steel and now high speed tool steel (HSS). HSS rolls are highly crack‐sensitive because of its high surface hardness. The crack propagation develops within the working surface of the roll, gradually increases in depth and width followed by a large “cats‐tongue” band type spalls of the overlying barrel surface and that leads to abnormal roll failure. This paper presents the development of surface wave based ultrasonic technique to optimize the grinding procedure for having crack free roll surface.

Damage resistance and roughness retention of work rolls in cold rolling mills

For every mill the ideal roll can be considered as one that can be used in a mill stand indefinitely. Unfortunately for the roll user, such ideal rolls do not exist. One major reason for work roll changes (planned or unplanned) is “wear”. In the context of cold rolling and temper rolling, “wear” primarily refers to loss of roughness and/or surface texture. Another limitation to roll performance is the fact that mill incidents – minor as well as major incidents – inflict damage on the work rolls, requiring redressing in the roll shop. If a major defect is present in a forged roll, e.g. due to a mill incident, catastrophic roll failure may occur in a violent, explosive manner. Improvement of the value-in-use of a work roll implies a superior wear resistance, a superior damage resistance, and elimination of the safety risks associated with explosive roll failures. In order to deal with this in a concerted R&D approach, a consortium of two roll users in the steel industry, a leading roll manufacturer, a high-tech supplier of roll damage detection equipment, and specialised research institutes have joined forces. Cold rolling trials have been performed, using pilot mills as well as industrial mills, with both novel forged HSS work rolls and conventional forged 3–5%Cr steel work rolls. Separate trials have been designed to focus on either the aspect of roughness evolution or damage resistance. Complementary data from various laboratory tests and industrial mill and roll shop data have been collected. Models have been developed for damage evolution in a roll, and for roughness evolution of the roll surface. In addition, novel non-destructive detection systems and sensors have been designed and tested. This paper provides a concise overview of the results achieved.

Failure of Tungsten Carbide Rolls from a Wire and Rod Mill

The paper presents the failure analysis of tungsten carbide rolls for the Wire and Rod Mill (WRM) and establishes the failure reasons and the corrective and preventive actions taken to improve roll performance. A sharp continuous increase in failure rate and decrease in average time between failure (ATBF) was observed during 2001 to 2004. The increase in premature failure of these rolls (16 rolls in 2003 and 38 rolls in 2004) raised the cost of operations. Due to unscheduled stoppage of the mill after roll failures, the unplanned mill delays also increased, causing production losses. The analysis revealed significant increase in premature failure of rolls in the finishing stands 19, 22, 23, and 24 and prefinishing stand 14. The primary causes of such failures were faulty roll cooling and roll mounting and accumulation of cobbles. Implementation of modified cooling headers, a calibrated gage to monitor hydraulic pressure during roll mounting, and eddy current inspection resulted in decreasing the trend in roll failure and increasing the trend in ATBF.

Cross wedge rolling failure mechanisms and industrial application

Cross wedge rolling (CWR) is an innovative metal forming technology with several well-documented benefits over other traditional manufacturing processes. Over the past several years, CWR technology has obtained overwhelming popularity within the United States, especially in the automotive industry. Based on the authors’ academic and industrial experience, recent development techniques for the CWR process are presented. Initially, the experimental and numerical research techniques for analyzing fundamental CWR failure mechanisms are presented with particular emphasis on the finite element method. This is followed by discussion on industrial implementation of cross wedge rolling system, including the required tooling manufacturing process and major supporting systems. Finally several industrial examples are presented to demonstrate feasibility and efficiency of the CWR process with the goal of removing hesitation of US manufacturers to adopt novel CWR technology.

複層鋳込みクラッド法による&lt;br&gt;熱間圧延用ハイスロールの基本特性

In an attempt to accommodate a smaller-diameter roll in hot rolling, a high-speed steel roll has been developed using tool-steel material on the outer surface, since tool steel has good abrasion resistance and mechanical strength. To employ such a roll in the existing hot-rolling process, it was necessary to develop a roll manufacturing technology to ensure a uniform structure for each large-size roll, and the same time, it was necessary to carry out an analysis of the properties required of rolls for hot rolling and to develop other supporting technology. We have optimized the chemical composition and size of the carbide, and improved the matrix structure, and thereby improved the roll's resistance to abrasion, roughened surfaces, and roll failure. At the same time, we developed a good lubricant suitable for the high-speed steel roll. As a result, we have successfully developed a high-speed steel roll with good abrasion resistance and mechanical strength.

熱間圧延用ハイスロールの圧延特性

A high-speed steel roll has been developed for use in hot-rolling employing tool steel compositions, which exhibits good abrasion resistance and good resistance against roughened surfaces. To apply the high-speed steel roll in an existing hot strip mill, it was necessary to develop supportive technologies for preventing roll failure, for accommodating thermal expansion and for stabilizing the friction coefficient. We have improved the flow-detecting technology, and established a control technology to accommodate changes in shape and friction coefficient, and also quantified the aforementioned basic characteristics. The high-speed steel roll development has enabled not only the extension of the roll life, but also the improvement of productivity and quality, and the reduction of production cost.

Failure Mechanism of Reflow Conductor Roll of Electroplating Tinning Line

Abstract The surface roughness of reflow conductor roll was checked on membrane sample. The surface morphology of conductor roll was observed by microscope, and the composition of adhered layer on conductor roll surface was analyzed by X-ray spectroscope. The results show that tin adhesion is the main reason for failure of conductor roll, and the failure of conductor roll is accelerated by wear. The measures to decrease tin adhesion and improve wear resistance were put forward.

공리설계와 반응표면모델에 의한 형상제어 압연기의 추력모델 개발

Rolling process to fabricate a strip with even thickness is significant to enhance the quality of the strip. The thickness of a strip can be effectively controlled by pair-cross mills. However, pair-cross mill generates thrust in the axial direction of roller and causes skewness, deflection, twist and even accidental roll chock failure. Therefore, accurate estimation of the thrust of the pair-cross mill during rolling process is necessary to monitor the failure of roll and the quality of products. An empirical equation given by Mitsubishi Heavy Industry (MHI) is hitherto employed, where the thrust is expressed in terms of rolling force, reduction ratio and crossed angle. However it turns out that the MHI empirical equation provides somehow inaccurate and unsuitable thrust in practical rolling processes. Moreover, we learn that three parameters involved in MHI equation are coupled each other. In this paper, axiomatic design principle is employed to select appropriate parameters involved in approximate equation in order to make parameters uncoupled. A quadratic equation using response surface method with new parameters is suggested. The accuracy of the approximate model is examined by comparing with real experimental data.

Prediction of the wear profile of a roll groove in rod rolling using an incremental form of wear model

A model for predicting the wear profile of the ductile cast iron roll during rod (or bar) rolling is proposed using Archard's wear equation. Archard's wear equation was reformulated as an incremental form and the hardness of the roll was expressed as a function of rolling time under a high temperature. The wear profile of the roll is calculated at each deformation step by consideration of relative sliding velocity and normal roll pressure at contact area. The coefficients required in the proposed wear model have been obtained using the high-temperature wear tester of pin-on-disc type. A three-dimensional finite element analysis coupled with the proposed wear model has been carried out for the oval-round pass rolling sequence widely used in present continuous rod (or bar) rolling mills. To describe the deformation behaviour of material at the roll/material interface better, a contact-searching algorithm that can be applied efficiently to the finite element mesh was also suggested. The results showed that, for an oval groove, the maximum wear occurs at the centre part of the roll and, for a round groove, at the shoulder area of the roll. The wear profiles moves to the spread direction of workpiece (i.e. roll axis direction) as well as the direction of roll centre as the production (tonnage) increases. The proposed wear model might be used for adjusting the gap (pass height) of rolls to set up a suitable rolling schedule for keeping dimensional tolerance of the product and avoid catastrophic failure of rolls after rolling a characteristic tonnage.

Microstructural Features of Prematurely Failed Hot-Strip Mill Work Rolls: Some Studies in Spalling Propensity

Work rolls made of indefinite chill double-poured (ICDP) iron are commonly used in the finishing trains of hot-strip mills (HSMs). In actual service, spalling, apart from other surface degeneration modes, constitutes a major mechanism of premature roll failures. Although spalling can be a culmination of roll material quality and/or mill abuse, the microstructure of a broken roll can often unveil intrinsic inadequacies in roll material quality that possibly accentuate failure. This is particularly relevant in circumstances when rolls, despite operation under similar mill environment, exhibit variations in roll life. The paper provides an insight into the microstructural characteristics of spalled ICDP HSM work rolls, which underwent failure under similar mill operating environment in an integrated steel plant under the Steel Authority of India Limited. Microstructural features influencing ICDP roll quality, viz. characteristics of graphite, carbides, martensite, etc., have been extensively studied through optical microscopy, quantitative image analysis (QIA), and electron-probe microanalysis (EPMA). These are discussed in the context of spalling propensity and roll life.

Influence of microstructure on the premature failure of a second-intermediate sendzimir mill drive roll

Although a precise understanding of roll failure genesis is complex, the microstructure of a broken roll can often unravel intrinsic deficiencies in material quality responsible for its failure. This is especially relevant in circumstances when, even under a similar mill-operating environment, the failure involves a particular roll or a specific batch of rolls. This paper provides a microstructural insight into the cause of premature breakage of a second-intermediate Sendzimir mill drive roll used at a stainless steel sheet rolling plant under the Steel Authority of India Limited. Microstructural issues influencing roll quality, such as characteristics of carbides, tempered martensite, retained austenite, etc., have been extensively studied through optical and scanning electron microscopy, electron-probe microanalysis, image analysis, and x-ray diffractometry. These are discussed to elucidate specific microstructural inadequacies that accentuated the failure. The study reveals that even though retained austenite content is low (6.29 vol%) and martensite is non-acicular, the roll breakage is a consequence of intergranular cracking caused by improper carbide morphology and distribution.

Evaluation of Subsurface Fatigue Damage in Strip Mill Rolls by an X-ray Diffraction Method

The X-ray diffraction line profile analysis technique has been applied to the study of fatigue damage below the surface of the work and the backup rolls of a cold strip mill, and the backup rolls of a hot strip mill. Half value breadth has been taken as a measure of fatiguing.The fatigued zone below the surface of the rolls correlated well with the half contact length, L, being 0.03L in the work roll of cold strip mill and 0.1L in the other rolls. Changes in the half value breadth with an increase in the number of cycles of roll contact differ according to the surface hardness of the roll: continued cycling results in a decrease in the half value breadth at the surface in hard rolls (Hs≥60), and an increase in soft rolls (Hs≤50). This technique, the X-ray study of fatigue, can be extended to the prediction and prevention of accidental failure of rolls due to fatigue fracture such as spalling. Furthermore, the amount of surface dressing at regular maintenance of rolls can be saved significantly on the basis of an accurate evaluation of the depth of the fatigue damaged zone.

Nature and causes of back-up roll failure on the 1700 mill

Nature and causes of back-up roll failure on the 1700 mill