Solid State Phenomena Vol. 89 (2003) pp. 321-326 online at http://www.scientific.net © 2003 Trans Tech Publications, Switzerland
Mechanical Spectroscopy of Rolling Oil Films on Cold-Rolled Steel Sheets
Leszek B. Magalas1, Serge Etienne2, Laurent David3 and Tomasz Malinowski1 1
University of Mining and Metallurgy, Faculty of Metallurgy and Materials Science al. Mickiewicza 30, 30 - 059 Kraków, Poland 2 Ecole des Mines, Laboratoire de Physique des Matériaux Parc de Saurupt, 54042 Nancy Cedex, France 3 Groupe d'Etudes de Métallurgie Physique et Physique des Matériaux Institut National des Sciences Appliquées, 20 avenue Albert Einstein 69621 Villeurbanne Cedex, France
Keywords: mechanical spectroscopy, steel sheets, cold rolling, rolling oils, infrared spectroscopy, Snoek-Köster relaxation Abstract. Mechanical spectroscopy is a unique technique that is capable of detecting extremely fine traces of rolling oil left on the surface of cold-rolled steel sheets. In this study we have demonstrated that a characteristic mechanical loss spectrum occurs in the low-temperature range from 180 K to 280 K only in the two following situations: (1) if traces of the rolling oil are left on the surface of sheets or (2) if the sheets are covered with a thin film of the rolling oil. Nearly the same loss spectra have been observed in subresonant mechanical loss measurements of paper micro-samples covered with a thin film of rolling oil. It can therefore be concluded that the observed mechanical loss phenomena take place in the rolling oil, that is, they do not depend on whether the substrate is metallic or paper. Moreover, the subresonant mechanical spectroscopy can readily resolve the complex mechanical loss spectrum into three constituent peaks located at 188 K, 215 K, and at around 270 K, respectively. Rolling oils containing different amounts of sulphur generate low-temperature peaks of substantially different height. The asymmetrical peak observed at 270 K on heating is produced by a phase transformation of the rolling oil from the solid into liquid phase. Introduction Mechanical spectroscopy of ferritic steels is commonly used to study a variety of effects, which are directly or indirectly related to Snoek and/or Snoek-Köster (SK) peaks. In this paper different phenomena related to mechanical loss peaks generated by surface effects of steel sheets were investigated. The results demonstrate that mechanical spectroscopy is a very sensitive technique to detect fine traces of rolling oil remaining on steel surface after cold rolling and cleaning on the production line. The presence of oil traces on steel sheets generates complex mechanical loss spectra in the temperature range between 180 K and 300 K. A large number of different mechanical loss peaks in the same temperature range has been reported in the literature but mechanisms responsible for these peaks have not been fully elucidated. In this paper we present the first mechanical loss measurements performed on cold-rolled steel sheets with different states of the surface: (1) as-received cold-rolled steel sheets, (2) after thorough surface cleaning, (3) after covering a clean sample with thin films of four different rolling oils containing various amounts of sulphur. It is noteworthy that mechanical spectroscopy of cold-rolled steel sheets can also be used to determine susceptibility of steel sheets to the ‘dulling’ effect, also known as ‘steel reflectivity’.
Licensed to Akademia Górniczo-Hutnicza - Kraków - PolandLeszek B. Magalas (
[email protected]) - University of Mining and Metallurgy - Poland All rights reserved. No part of the contents of this paper may be reproduced or transmitted in any form or by any means without the
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Experimental Procedure Mechanical loss measurements were carried out in a resonant inverted torsion pendulum and in a subresonant mechanical microspectrometer. The logarithmic decrement of steel samples (plates 0.22×2.0×90.0 mm3 ) was obtained from free decaying oscillations of the resonant frequency around 1.3 Hz [1]. Three kinds of samples were studied: (1) steel sheets in the as-received state, that is, after cold rolling and industrial cleaning, (2) laboratory-cleaned samples (the surface layer was cleaned or chemically etched away), (3) clean samples obtained as in (2) covered with thin films of rolling oils. The oils contained the following four concentrations of sulphur: 0.40 %, 0.41 %, 0.70 %, and 0.74 %. The study was performed on two substrates: steel sheets (composition: 0.02 %C, 0.23 %Mn, 0.02 %Si, 0.008 %P, 0.010 %S, 0.04 %Cr, 0.035 %Al, 0.0039 %N2, and 0.02 %Cu) and for comparison, on paper (0.09 mm thick) covered with a film of oil. The subresonant measurements of the latter were carried out for two constant frequencies 0.10 Hz and 0.31 Hz in the temperature range from 175 K to 300 K. Infrared spectroscopy of rolling oils was performed with use of a Perkin-Elmer DSC7 IR spectrometer. Results and Discussion Figure 1 shows typical mechanical loss spectra, Q-1 = f(T), obtained for the as-received steel sheets (curve 1) and for laboratory-cleaned samples (curve 2). For the former the spectra in the lowtemperature range from 150 K to 300 K were always complex (curve 1). The low-temperature peaks were never observed in clean samples. A peak at around 270 - 280 K (Fig. 1, curve 1) located on the low-temperature side of the SK peak cannot be misinterpreted as the nitrogen Snoek peak. Figure 2 shows typical mechanical loss spectra, Q-1 = f(T), obtained for the laboratory-cleaned steel sample covered with rolling oil films containing various amounts of sulphur, i.e.: 0.41 % (curve 1), 0.70 % (curve 2), and 0.74 % (curve 3). Figure 2 provides evidence that an oil film deposited on the steel surface generates low-temperature mechanical loss spectra, which were not observed in samples with a clean surface (compare Fig. 1, curve 2). An increase in sulphur content results in a substantial decrease in the height of the low-temperature peaks, with their temperature location unaltered. The IR spectra of rolling oils in Fig. 3 prove that all of the oils supplied by different producers are one arachis oil. Consequently, the only difference between the oils is their sulphur content. In Fig. 4 mechanical loss spectra of steel and paper samples both covered with films of the rolling oil containing 0.40 %S, obtained with resonant and subresonant techniques, respectively are compared. Interestingly, the mechanical loss spectra overlap regardless of substrate. Figure 5 presents the temperature dependence of the mechanical loss angle, tg j, measured for the paper covered with the rolling oil film containing 0.40 %S at two different frequencies. The peaks in Fig. 5, having been recorded several times, were found to be typical of oil-induced mechanical loss peaks measured in the subresonant mechanical microspectrometer. The results shown in Fig. 4 and Fig. 5 demonstrate that while the resonant technique provided complex mechanical loss spectra extremely difficult to interpret, the subresonant technique provided excellent resolution of the spectra into three separate peaks located at 188 K, 215 K, and at around 270 K [2, 3]. Another interesting point in Fig. 5 is the shape of the 270 K peak. The peak is sharp and asymmetrical with the high-temperature side independent of frequency. The peak represents typical features of a mechanical loss peak induced by the phase transformation of the rolling oil from the solid into liquid state [3, 4].
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Mechanical loss spectra of a cold-rolled steel sheet. Curve 1 – as-received, i.e. after cold rolling and industrial cleaning, curve 2 – after surface cleaning in laboratory.
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Mechanical loss spectra of laboratory-cleaned cold-rolled steel sheets covered with a thin film of rolling oils containing various amounts of sulphur. Curve 1 - 0.41 %S, curve 2 - 0.70 %S, curve 3 - 0.74 %S.
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6,0 0.40 %S
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Infrared spectroscopy of rolling oils under examination. Oils contained different amounts of sulphur: 0.40 %, 0.41 %, 0.70 %, and 0.74 %.
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Typical mechanical loss spectra obtained in the resonant mode for steel sheets covered with a film of the rolling oil containing 0.40% of sulphur (curve 2 - Q-1 = f(T), frequency of free oscillations » 1.3 Hz) and in the subresonant mode for a paper substrate covered with a film of the same rolling oil (curve 1 - tg j = f(T), frequency of forced oscillations = 0.31 Hz).
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Mechanical loss angle versus temperature for a paper substrate covered with a film of the rolling oil containing 0.40 % of sulphur. Forced oscillations at 0.10 Hz and 0.31 Hz.
The so-called ‘oil peaks’ have widely been studied by Polish authors: Chomka, Samatowicz, Augustyniak, Haneczok, Denga, et al. [5 - 20]. They have reported complex mechanical loss spectra for various metallic samples and ceramics covered with thin films of oil or grease. However, despite a large number of experimental data now available, a self-consistent interpretation of the loss phenomena has not been formulated to date, but the asymmetrical, sharp peak such as the one obtained in this study at 270 K, is commonly recognized as resulting from the phase transformation of the oil itself. More recently, Samatowicz has suggested [16] that mechanical loss peaks observed in Ni, Fe, and steel samples covered with films of synthetic oil or synthetic grease be interpreted in terms of hydrogen-induced relaxation effects taking place in a metallic substrate, which she has later specified as hydrogen SK relaxation [17, 18]. This would imply that there exist interactions between an oil film and a metallic substrate. However, we have shown in this study that an oil film deposited on both metallic and paper substrates generates the same mechanical loss spectrum, which provides evidence that there is no interaction between an oil film and a metallic substrate. Conclusions We have shown that mechanical spectroscopy can be successfully applied in detecting fine traces of rolling oils on the surface of cold-rolled steel sheets. Low-temperature mechanical loss spectra recorded for cold-rolled steel sheets and for both the metallic and paper substrates covered with thin films of rolling oils are practically the same. The low-temperature mechanical loss spectrum is composed of three constituent peaks located at 188 K, 215 K, and at around 270 K as resolved by subresonant mechanical spectroscopy. This rules out the concept of possible interactions between an oil film and a metallic substrate as the origin of the loss peak. It can be further concluded that the low-temperature peaks result from loss phenomena occurring in the oil film itself. The peak observed at around 270 K is brought about by a phase transformation of the rolling oil from the solid into liquid phase, which takes place inside the film.
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Acknowledgements Financial support of the Polish State Committee for Scientific Research (KBN) under grant No 7 T08B 031 15 and 11.11.110.258 is gratefully acknowledged. References [1] L. B. Magalas, T. Malinowski, Measurement Techniques of the Logarithmic Decrement, this volume. [2] L. B. Magalas, T. Malinowski, S. Etienne, L. David, J. Kostro, Proc. Conf. XXIX KKBN, on Non-destructive Testing, SIMP, Warsaw, Poland 5, 223 (2000). [3] L. B. Magalas, S. Etienne, D. Laurent, Proc. Conf. XXXI KKBN on Non-destructive Testing, SIMP, Warsaw, Poland 7, 257 (2002). [4] T. Malinowski, PhD Thesis, University of Mining and Metallurgy, Kraków, Poland (2002). [5] W. Chomka, M. Pstroko ski, E. Denga, ‘Relaksacje niespr yste i opó nienia magnetyczne w ciałach stałych’, Katowice, Wydawnictwo Uniwersytet l ski, p. 91 (1980) (in Polish). [6] W. Chomka, E. Denga, P. Moser, Phys. Stat. Sol. (a) 62, K53 (1980). [7] W. Chomka, E. Denga, J. de Phys. 42, C5, 1165 (1981). [8] W. Chomka, E. Denga, J. de Phys. 44, C9, 505 (1983). [9] B. Augustyniak, G. Fantozzi, J. de Phys. 44, C9, 493 (1983). [10] W. Chomka, E. Denga, Prace Naukowe Uniwersytetu l skiego w Katowicach Nr 615, ‘Zjawiska anelastyczne i migracyjne opó nienia magnetyczne w ciałach stałych’, Uniwersytet l ski, Katowice, p. 191 (1984) (in Polish). [11] G. Haneczok, T. Poloczek, J. W. Moro , Prace Naukowe Uniwersytetu l skiego w Katowicach Nr 615, ‘Zjawiska anelastyczne i migracyjne opó nienia magnetyczne w ciałach stałych’, Uniwersytet l ski, Katowice, p. 200 (1984) (in Polish). [12] B. Augustyniak, Prace Naukowe Uniwersytetu l skiego w Katowicach Nr 615, ‘Zjawiska anelastyczne i migracyjne opó nienia magnetyczne w ciałach stałych’, Uniwersytet l ski, Katowice, p. 183 (1984) (in Polish). [13] W. Chomka, E. Denga, T. J. Levis, B. aba, J. de Phys. 46, C10, 817 (1985). [14] E. Denga, B. Augustyniak, Materials Science Forum 119-121, 331 (1993). [15] D. Samatowicz, O. Olszewski, Ceramics International 22, 187 (1996). [16] D. Samatowicz, E. Łunarska, Proc. IX Int. Conf. Imperfections Interaction and Anelasticity Phenomena in Solids, Izv. Akad. Nauk – Physics 62, No 7, 1317 (1998). [17] D. Samatowicz, A. Zieli ski, Proc. Int. Conf. on Engineering Materials Environmental Degradation, EDEM ’99, Gda sk - Jurata, Poland, September 19-23, 1999, p. 381 (1999). [18] D. Samatowicz, J. Alloys and Compounds 310, 457 (2000). [19] D. Samatowicz, A. Kulik, W. Benoit, Materials Science Forum 119-121, 529 (1993). [20] D. Samatowicz, J. de Phys. 48, C8, 525 (1987).
