THE INFLUENCE OF STRIP TEMPERATURE ON THE LOAD OF THE HOT STRIP MILL FINISHING GROUP LOOPER. Evgeny E. Didenko, Victor N.

Transcription

1 Journal Journal of Cheical of Cheical Technology Technology and Metallurgy, and Metallurgy, 5, 4, 5, 017, 4, THE INFLUENCE OF STRIP TEMPERATURE ON THE LOAD OF THE HOT STRIP MILL FINISHING GROUP LOOPER Evgeny E. Didenko, Victor N. Meshcheryakov Lipetsk State Technical University 30 Moskovskaya St Lipetsk, Russian Federation E-ail: Received 05 January 017 Accepted 04 May 017 ABSTRACT The article describes the dependence of the coponent of the load the rolled strip bending oent in the interstand space on its teperature. It researches the change of the load character on the depending on the interstand space of the hot strip ill finishing group. Keywords:, load oent coponent by strip bend, load oent coponent by strip tension, load oent coponent by strip weight, etal tensile strength, rolled strip teperature. INTRODUCTION It is known that the teperature of a etal strip is not unifor throughout its length when the strip is approaching the finishing group. This non-unifority is deterined by a nuber of factors. Aong the are the different ties when different strip cross-sections are in the delay table (and, hence, the different cooling tie), the non-unifority of slab heating in continuous furnaces, the presence of scale. Besides, the unifority of heating seifinished rolled products before the finishing group is influenced by the presence of skid arks. The strip head is generally hotter than its tail. The nonunifority of strip teperature throughout its length is also observed in interstand spaces, whereby due to accelerated rolling under reduction (with the etal heated up) the strip teperature distribution throughout its length ay be reversed, i.e. the strip tail becoes hotter than the head. In any case, the non-unifority of strip teperature throughout its length is ost distinctly observed in the first interstand space and is priarily deterined by the seifinished rolled products teperature. The non-unifority of rolled strip teperature in the interstand space influences greatly the change in the load, the work of its electric drive and the syste of regulating strength as a whole, as well as the stability of the rolling process. The non-unifority of strip heating throughout its length influences the load through the coponent of the load oent by strip bend M bend. It should be noted that in setting the autoatic control syste of strip tension of the hot strip ill finishing group and in calculating the s drive oent, the value of the coponent M bend is often neglected because it is considered insignificant [1-3]; this, however, holds in soe cases only. The neglection of the coponent M bend in adjusting the strip tension in this space strongly influences adjusting the strip tension in interstand spaces, which is especially iportant for the first space. MATHEMATICAL MODEL The tensile strength value used for calculating the bend oent depends on the teperature of rolling. The tensile strength value in hot rolling can be estiated by the forulas and diagras given in [4-6]. One of such forulas is written as: σ s A ε e u t 1 3 (1) 70

2 Evgeny E. Didenko, Victor N. Meshcheryakov 0.15, ), 40Х13 (coefficients А 40, , 0.80, ) [6]. In rolling, the ar experiences the load oent М load (static oent) which is the su of the following coponents [], [3], [10], [11] (see Fig. ): M loadm + M weight+ M tension+m (3) bend 1. Load oent on the shaft fro unbalanced parts of the structure: Fig. 1. The change of the tensile strength of etal according to teperature for steels 45, 08Ю, 40Х13 in the interstand space. where σ s is the tensile strength of etal in hot rolling (МPа), tº - rolled etal teperature (ºС), A, 1,, 3 epirically deterined coefficients individual for each etal (deterined according to the tables [6]), u strain rate of etal (s -1 ), ε strain rate during the pass easured in fractions. Considering that in order to investigate the load oent, the tensile strength value is not deterined in the deforation zone, but in the interstand space, the values of u1 and ε1 and, consequently, the equation (1) will be written as [7-9]: σ s e A 1 () t Fig. 1 shows the change of σ s for steel grades 45 (coefficients А 1330, , 0.5, ), 08Ю (coefficients А 1195, , ' (4) M M cos α where M is the oent fro unbalanced parts at the horizontal position of the, α the s angle of elevation, M the value deterined by the structure weight.. Load oent on the shaft by strip weight: M weight γ B H L g R cos α (5) where γ is the rolled etal density, g 9.81 /s² - gravitational acceleration, H - etal thickness in the interstand space, B - etal strip width, R - the s ar radius, L - interstand space length. 3. Load oent on the shaft by bend: M tension σ B H R sin L α (6) where σ is the specific strip tension in the interstand space. 4. Load oent on the shaft by bend is written as: Fig.. A diagra of one interstand space of the hot strip ill. 703

3 Journal of Cheical Technology and Metallurgy, 5, 4, 017 B á σ H R cos S M bend L (7) where σ s is the rolled etal tensile strength. There are ethods and forulas for indirect estiation of strip teperature values in the interstand space, e.g., upon the readings of the pyroeter positioned behind the last stand of the roughing group [6] (because it is ipossible to easure the teperature directly in the interstand space due to utterly unfavorable environental conditions dense vapor, splashing water etc.). However, considering the first interstand space, it can be assued that the teperature of the strip passing through the space changes along its length by 60ºС e.g., fro 90 to 860ºС. Further, let us consider the rolling of 08Ю steel in the first interstand space of the finishing group. Let the diensions of the strip leaving the finishing group be: width , thickness - 3. Seifinished rolled products thickness before the finishing group is estiated according to the forula [6]: 0, h 8 h, (8) 0 where h 0 () is the seifinished rolled products thickness, h () finished strip thickness (3 in the considered case). Then h The thickness of etal in the spaces can conventionally be calculated according to the forula [6]: - j j h h h, (9) j 0 where j is the current pass index, - last pass index (the last stand), h 0,h - seifinished rolled products thickness and finished strip thickness. The given strengths in the interstand space of the finishing group (МPа) are estiated according to the forula [6]: [0,7(h +1,6)] σ 10 (j + 1) e (10) j where h is the thickness of the finished strip leaving the finishing group (), j the stand nuber starting fro the finishing scale breaker. It is worth noting that the expressions (8) - (10) should be used for theoretical estiation of the required values, because in practice the given rolling paraeters are priarily deterined by the working instructions and ay slightly differ fro those calculated theoretically. In particular, the real rolling paraeters ay be as follows: seifinished rolled products axiu thickness in the finishing group - 50, rolled strip axiu thickness - 16, specific tensions in the finishing group vary (depending on the final rolled etal thickness) fro 0.59 (first spaces) to 15 (last spaces) МPа. EXPERIMENTAL We define the ratios of the load values in the range in which the angle of rotation of its frae changes fro 0 to 45º for the first and the last spaces with account of the rolled etal teperature. We consider that the coponent of the load oent fro the s unbalanced parts depends on its design, does not depend on strip paraeters and is equal for all interstand spaces. Fig. 3. The coponents of the load oent depending on the angle of rotation of its frae (а) at strip teperature of 90ºС and (b) at strip teperature of 860ºС for the first interstand space. 704

4 Evgeny E. Didenko, Victor N. Meshcheryakov For the last space (the 7 th pass starting fro the finishing scale breaker) according to the forula (10) σ 7 17 МPа. The load distribution is shown in Fig. 4. For hot strip ill real strength values, e.g., 0.59МPа - for the first and 15МPа - for the last strip at rolled etal thicknesses indicated earlier and the rolled etal teperature of 90ºС, we have dependences shown in Fig. 5. CONCLUSIONS Fig. 4. The coponents of the load oent depending on the angle of rotation of its frae at strip teperature of 860ºС for the last interstand space. For all doestic electroechanical s М 5000 N. The first space (between the 1 st and the nd stands of the 7-stand hot strip ill finishing group with the finishing scale breaker). The strip teperature supposedly changes as indicated earlier (along its length by 60ºС - e.g. fro 90 to 860ºС). For the first interstand space h (according to the expression (9)). The specific tension according to the forula (10) σ j МPа. The drive load distribution by the coponents depending on the angle of rotation of its frae at strip teperature of 90ºС and at strip teperature of 860ºС is shown in Fig. 3 [11]. Now let us consider the last interstand space of the continuous wide-strip hot ill finishing group. We say that the rolled etal teperature is 860ºС. Then the tensile strength σ s according to the expression () will be equal to 139. МPа. According to the forula (9), the rolled strip thickness in the last space equals 4.6. The ain coponent of the drive load oent in the first interstand space in the whole rotation range of the frae is the coponent of the strip bending oent М bend which depends on the rolled etal teperature. Hence, in controlling the drive it would be wrong to neglect the coponent М bend. Besides, in order to guarantee a better work of the autoatic control syste of strip tension, it is also necessary to take into account the influence of the rolled etal teperature on the value М bend. In contrast, for the last interstand space, the ain value deterining the load on the drive shaft is the value of the coponent М tension. The influence of the coponent М bend is insignificant as well as that of М weight, which is explained by a low thickness of the rolled etal. In conclusion it should be noted that, in order to raise the efficiency of the autoatic control syste of strip tension of the hot strip ill finishing group, in its designing and setting, the strip bending oent М bend ust be taken into account as the function of the rolled etal teperature, which is especially iportant for the first interstand spaces. Fig. 5. The coponents of the load oent depending on the angle of rotation of its frae (а) for the last interstand space at strip teperature of 90ºС and (b) for the first interstand space at strip teperature of 90ºС. 705

5 Journal of Cheical Technology and Metallurgy, 5, 4, 017 REFERENCES 1. G.G. Foin, Mechanization and autoation of widestrip hot ills, G.G. Foin, A.V. Dubeykovsky, P.S. Grinchuk, Moscow, Metallurgy, 1979, pp. 31, (in Russian).. Chi-Cheng Cheng, Lan-Yuan Hsu, Yuan-Liang Hsu, Zhi-Shyong Chen, Precise siulation for hot strip ills using an auto-tuning approach, The International Journal of Advanced Manufacturing Technology, 7, 006, Lan-Yuan Hsu, Chi-Cheng Cheng, Yuan-Liang Hsu. Siulation of Looper Height Control in the Hot Strip Finishing Mill, The 5th Annual International Conference on Industrial Engineering -Theory, Applications and Practice, Deceber 13-15, 000, Hsinchu, Taiwan. 4. Yu.V. Konovalov, A.L. Ostapenko, V.I. Ponoarev, Calculation of sheet rolling paraeters, Reference book, Moscow, Metallurgy, 1986, pp. 430, (in Russian). 5. A.P. Grudev, Theory of rolling: Textbook for higher educational institutions, Moscow, Metallurgy, 1988, pp. 40, (in Russian). 6. Designing the paraeters and operating odes of sheet-rolling shops equipent, Manual, V. S. Zaytsev, V.A. Tretyakov, Lipetsk, Lipetsk State Technical University, 009, pp. 660, (in Russian). 7. V.A. Belyaev, Physical bases of plastic deforation of etals: Manual for students ajoring in High-energy devices of autoatic systes, V.A. Belyaev, P.V. Vereshchagin, Altai State Technical University, BTI.-Biysk. Altai State Technical University Publishing House, 006, pp. 106, (in Russian). 8. V.N. Meshcheryakov, E.E. Didenko, Influence of strip teperature in the hot strip ill finishing group on s drives load oent, 9 th International scientific and practical conference Equipent and Technology: New Developent Prospects, 013, pp. 16-1, (in Russian). 9. V.N. Meshcheryakov, The influence of seifinished rolled products teperature of the hot strip ill finishing group on the s drive perforance, V.N. Meshcheryakov, E.E. Didenko, Collection of scientific works Electrotechnical Systes and Coplexes of the Power Engineering and Autoated Systes Institute of Nosov Magnitogorsk State Technical University, Magnitogorsk, 0, 01, 41-5, (in Russian). 10. V.L. Stefanovich, Autoation of continuous and sei-continuous wide-strip hot ills,- Moscow, Metallurgy, 1975, pp. 08, (in Russian). 11. V.N. Meshcheryakov, The ratio of values coprising the s drive load oent, V.N. Meshcheryakov, E.E. Didenko, Ural Scientific Messenger, 5, 1, 016, 81-8, (in Russian). 706