TPT July 2009

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Feeding back the results of the thickness measurements in the directions of channels 1, 8 and 7 controls the extent of groove closure caused by cylinder 4c and 4d. In figure 6-b the same concept is illustrated at No 5 stand. The extent of groove closure caused by cylinder 5a and 5b is controlled by feeding back the results of the thickness measurements in the directions of channels 1,2 and 3.

The invention practiced

The invention not practiced

5 0 Deviation in wall thickness (mm) Frequency  Figure 9 : Graphic representation of the distribution of the deviations in thickness before and after cylinder control 0.3 0.5 0.7 0.9 1.1 1.3 1.5

 Figure 8 : Graphic representation of the changes in deviation in thickness using cylinder control

The extent of groove closure caused by cylinder 5c and 5d is controlled by feeding back the results of the thickness measurements in the directions of channels 5, 6 and 7. The mean value wt_ave of thickness measurement data for channels 1 to 8 can be represented as follows: wt_ave = (wt1+wt2+wt3+wt4+…+wt8)/8 wt(i) = thickness measurement of channel(i) The difference of channel (i) between thickness measurement and mean value (wt_ave) is represented as follows: dwt(i) = wt(i) - wt_ave When the controlled variables for cylinders 4a and 4b are represented by d4a and d4b, and the direction of opening of the cylinders is represented by + and -, the following equations can be formulated: d4a + d4b= - 2 x dwt4 d4a - d4b= k·(dwt5 - dwt3) According to geometric calculations, k is equal to 2 0.5 L/R, where L is cylinder distance and R is the roll radius. But k may be determined empirically by mill conditions or reduction sizes. In the same way, the following equations can be formulated: d4c + d4d= -2 x dwt8 d4c - d4d= k·(dwt1 - dwt7) d5a + d5b= -2 x dwt2 d5a - d5b= k·(dwt3 - dwt1) d5c + d5d= -2 x dwt6 d5c - d5d= k·(dwt7 - dwt5) Therefore, the controlled variable for every cylinder is obtained. After the tube is rolled and measured by a hot wall thickness meter, the position of every cylinder is adjusted. At every rolling, the roll’s positions are adjusted and the wall thickness is measured again. By repeating, adjusting and measuring, the deviation of wall thickness is minimised. Conclusion Premium seamless steel tubes are produced at Wakayama Steel Works. Two of the most important new-generation technologies for the production are:

1. The high-toe-angle and high-expansion piercing technology, enabling SMI to produce high-strength pipes and stainless pipes without defects. 2. The new method of measuring and controlling hot wall thickness, enabling SMI to produce pipes of very accurate dimensions. References 1. C.Hayashi,M.Akiyama,T.Yamakawa: Advancements in cone-type rotary piercing technology, Trans. ASME, Journal of Manufacturing Science and Engineering, August 1999,vol.121/313 2. C.Hayashi, T.Yamakawa: Influences of feed and cross angle on inside bore and lamination defects in rotary piercing for materials with poor hot workability, ISIJ International, vol.37 (1997), No.2, pp.153-160 3. C.Hayashi, M.Akiyama, S.Tumura, T.Yamakawa, K.Shimoda: Influences of feed and cross angle on inside bore and lamination defects in rotary piercing for materials with poor hot workability, ISIJ international, vol.37 (1997), No.9, pp.892-898 4. C.Hayashi, T.Yamakawa: Influences of feed and cross angle on rotary forging effects and redundant shear deformations in rotary piercing process, ISIJ International, vol.37 (1997), No.2, pp.146-152 5. C.Hayashi, T.Yamakawa: Comparison of double and single piercing process in seamless tube manufacture, Materials Science Research International, Vol.3 (1997), No 3 pp 143-150 6. H.Hori, M.Tawara, R.Nakanishi, T.Yamada, H.Kawabata: Medium size seamless pipe mill at wakayama steel works, Tube Veracruz 2003 7. Sumitomo Metal: New-generation technologies for the production of medium size seamless pipes and tubes, Okochi Memorial Foundation, Japan, March 2003 8. Y.Arai,K.Kondo,M.Hamada,N.Hisamune,N.Murao,H.Osako,T.Murase: Development of high-strength heavy-wall sour-service seamless line pipe for deep water by applying inline heat treatment, International Pipeline Conference, October 2004 9. A Yamane, H Iwamoto: Synchronous learning algorithm with gain scheduling for both time-variant and rolling conditional factor, IFAC 2004 This paper was first presented at Tube Ukraine International Conference, 2007, and is reproduced with the generous permission of the joint organisers, Ukrtruboprom Association and International Tube Association.

Sumitomo Metal Industries Ltd Fax : +81 6 6223 0305 Website : www.sumitomometals.co.jp

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