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

Ray, Amitava; Prasad, M. S.; Dhua, S. K.; Şen, Sadri; Jha, Sunil Kumar

doi:10.1361/105994900770345854

Cited by 10 publications

(5 citation statements)

References 1 publication

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“…The pressures exerted during rolling can lead to the crushing of some carbides and the subsequent transmission of the cracks generated through the network of these carbides [13]. Aside from the rolling process, the possible cracking and spalling of the surfaces of these rolls is strongly influenced by the microstructural characteristics of the working layer [14], especially by the presence of carbides [15]. For the above reasons, it follows that in addition to wear resistance in the working layer of these rolls, they must also present a high mechanical strength and a high fracture strength.…”

Section: Introductionmentioning

confidence: 99%

Enhanced Fracture Strength in the Working Layer of Rolls Manufactured in Ni-Hard Cast Iron Alloyed with Mo, Nb and Mg

Cofiño-Villar

Álvarez-Antolín

Lozano

2018

Metals

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One of the main in-service failure mechanisms of the work-rolls used in hot strip mill finishing stands is surface spalling. The indefinite chill double-poured rolls usually comprise of a peripheral working layer made of crushed Ni-hard cast iron and a grey cast iron core, mostly pearlitic matrix with spheroidal graphite. To enhance its wear resistance, the working layer can be alloyed with Mo and Nb. The possible cracking and spalling of the surfaces of these work-rolls is strongly influenced by the presence of carbides and the continuity of their network. The flexural and impact toughness tests are reliable testing methods to assess these properties. The aim of this paper is to identify those manufacturing factors that have a significant effect on the flexural strength and toughness of this material, correlating the results with the volume fraction of precipitated carbides. It is worth highlighting, among the analysed factors are the liquidus temperature, the %Si, the use of an inoculant with traces of Lanthanum, and inoculation with different amounts of FeB, SiCa and Mg. Inoculation with SiCa is found to have a positive effect on the toughness of the material, breaking up the continuity of the carbide network, while FeB is found to act as a heterogeneous nucleant for NbC precipitation. However, high FeB contents reduce flexural strength and do not have a significant effect on the hardness of the material. To enhance the fracture toughness of the working layer, a liquidus temperature in the 1270–1275 °C range is recommended, as well as inoculating the ladle with Mg, 3 kg/T FeB and 0.6 kg/T SiCa.

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Section: Introductionmentioning

confidence: 99%

Enhanced Fracture Strength in the Working Layer of Rolls Manufactured in Ni-Hard Cast Iron Alloyed with Mo, Nb and Mg

Cofiño-Villar

Álvarez-Antolín

Lozano

2018

Metals

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“…Except having excellent fracture resistance, its surface must have excellent wear and heat resistance, because the quality of rolls not only affects the product cost, but also immediately determines product quality and working rate of rolling mill. For these reasons, the study on improving the wear resistance of hot rolling rolls causes home and overseas attention, the materials of hot rolling rolls have been improved and developed ceaselessly, from common chilled iron [1], indefinite chilled alloy iron [2], high chromium cast iron and high chromium cast steel [3] to high speed steel (HSS) [4] and powder metallurgy (PM) hard metal [5] that are now widely used in overseas market.…”

Section: Introductionmentioning

confidence: 99%

A study of heat treatment of high‐boron high‐speed steel roll

Cen¹,

2013

Materialwissenschaft Werkst

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High-boron high-speed steel (HSS) is a cheap roll material. In the paper, the authors research the effect of heat treatment on the microstructure and properties of high-boron high-speed steel HSS roll containing 0.54% C, 1.96% B, 3.82% W, 7.06% Mo, 5.23% Cr and 2.62% Al by means of the optical microscopy (OM), the scanning electron microscopy (SEM), X-ray diffraction (XRD) and hardness test. The results showed that as-cast structure of boron-bearing high-speed steel HSS consisted of martensite, pearlite, M 2 (B, C), M 3 (B, C) and M 23 (B, C) 6 type borocarbides. After quenching, the matrix transformed into the lath martensite, and M 3 (B, C) dissolved into the matrix. When quenching temperature is lower than 1050 8C, the hardness is increased with the increase of quenching temperature under oil cooling, while quenching temperature excels 1100 8C, the hardness will decrease with the increase of quenching temperature. Under the condition of salt bath and air cooling, the effect of quenching temperature on the hardness is similar to the above law, but the quenching temperature obtaining the highest hardness is higher than that of oil cooling. The highest hardness is obtained while tempering at 525 8C. The hardness of high-boron high-speed steel HSS roll is 66.5 HRC, and its impact toughness excels 13.1 J/ cm 2 . Using in pre-finishing stands of high-speed hot wire-rod rolling mill, the wear rate of highboron HSS rolls is 0.26 mm/one thousand tons steel. However the manufacturing cost of highboron HSS rolls is obviously lower than that of powder metallurgy hard alloy rolls, it is only 28% of that of powder metallurgy (PM) hard alloy rolls.Keywords: High speed steel roll / boron alloying / heat treatment / rolling steel / wear resistance /

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“…The reasons leading to roll spalling are mainly caused by: roll materials, [1][2][3] stress concentration fatigue and overload, 4,5 accident during steel rolling, 5 and roll use process rules and management. 6 Most research has been concentrated on the spalling mechanism [7][8][9] and improving measures on roll material, manufacture, use and management, and inspection technology to solve the roll spalling problem in hot strip mill.…”

Section: Introductionmentioning

confidence: 99%

VCR back-up roll and negative work roll contour design for solving roll spalling and transfer bar profile problems in hot strip mill

Wang¹,

Li²,

Li³

et al. 2010

Ironmaking & Steelmaking

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During the first year of production in the 2250 mm hot strip mill of Qian'an Iron and Steel Company of Shougang Steel Corporation, roll spalling and broken rolls were frequent occurrences, especially on the second stand of roughing mill (R2), and resulted in enormous economic losses. In addition, improvements to strip shape were required. One of the factors resulting in strip shape defects after finish rolling is that the transfer bar usually had an unsound profile such as a large wedge, camber or negative crown after roughing rolling. To solve these problems, a variable contact back-up roll contour curve with six order of polynomials and negative crown contour was designed and applied to the back-up roll and work roll of roughing mill stands R1 and R2 instead of a conventional flat roll contour. After the application, roll spalling, crown and wedge quality of the transfer bar and strip quality all improved.

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

Cited by 10 publications

References 1 publication

Enhanced Fracture Strength in the Working Layer of Rolls Manufactured in Ni-Hard Cast Iron Alloyed with Mo, Nb and Mg

Enhanced Fracture Strength in the Working Layer of Rolls Manufactured in Ni-Hard Cast Iron Alloyed with Mo, Nb and Mg

A study of heat treatment of high‐boron high‐speed steel roll

VCR back-up roll and negative work roll contour design for solving roll spalling and transfer bar profile problems in hot strip mill

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