In the structual shape mill at Kashima Steel Works of Sumitomo Metal Industries, Ltd., all large H-beams ranging up to H900×300 and H500 ×500 have been produced by rolling 250-mm thick continuously cast slabs in one heat with a new split rolling method.
Compared with the conventional rolling method which starts from ingots, the rolling yield has raised by 10% and the energy consumption has been significantly improved.

View full abstract

The 3-roll rolling process is analyzed by the energy method. A simplified admissible velocity field defined by three variable parameters is introduced. The solutions are derived by minimizing the consumed energy rate. Numerical calculations are done for hexagon-flat pass and the results are compared with the experiments. Both results on the roll torque and reduction in cross-sectional area agree satisfactorily.

View full abstract

Mandrel mill hydraulic screwdown control was successfully installed at the Kainan Steel Tube Works of Sumitomo Metal Industries, Ltd. in July, 1985. The purpose o f the control is to preform tube ends in a thin tapered form. By preforming the tube ends, it is possible to cancel the end thickening in the reducer and reduce the length of crop losses.
The analysis of variations in inter-stand tensions when the above end thinning control is carried out and the methods of roll speed control to prevent these variations are first discussed. Secondly, the causes of the wall eccentricity in the end thinning control and its countermeasures are described. Thirdly, the computer control system installed at the Kainan Steel Tube Works is presented. Lastly, the effects of the end thinning control are described.

View full abstract

In spite of recent developments of new plan view pattern control methods in plate, width loss by trimming is a significant problem.
This paper reports the method for manufacturing trimming-free plates on the basis of the analysis of edging characteristics in lead model tests, the features of commercial edger and its control system and squaring characteristics of edge in production rolling process. The results obtained are as follows:
(1) Width reducing efficiency is small in V rolling. A small amount of width screw-down improves the efficiency.
(2) The V roll of edger is provided with a flat part and a caliber part so that the edge can be shaped in square by selective use of either part according to the rolling pass.
(3) A powerful, highly accurate AWC is necessary for highly accurate width control over the whole length of rolling material.
(4) Width loss can be drastically reduced by combination of chamfer rolling with finish-edging. Manufacturing of trimming-free plate can be achieved by applying this process.

View full abstract

Hearty width reduction has become increasingly important in the production of hot steel strip. When a thick slab is subjected to heavy width reduction, the rolling force is too great. Therefore, the edger must be large and expensive. On the other hand, when a wide slab compared with its thickness is subjected to heavy width reduction, most of slabs buckle convexly upwards along the transverse direction.
It was an objective of this study to develop an improved method to reduce heavily the width of thin materials without transverse buckling.
As the results, a new edger rolling method with a pair of edging rolls tilted in the entry direction was developed. The principle of operation is as follows; when the edging rolls are tilted in the entry direction, the vertical force is applied upward to the edges of slab. The resultant force of this vertical force and transverse force of edge rolling bends the slab convexly downwards. When heavy reduction is applied to a slab bent in this manner, the slab bending is constrained by the table rollers and buckling does not take place. In the model tests, the critical width reduction without buckling of the new-type edger is three or four times than that of the conventional-type edger.

View full abstract

A looper optimal multivariable control system based on an optimal regulator theory has been developed. Goal of controlling the hot strip finishing mill loopers is to stabilize rolling operation and to maintain product quality by controlling the tension applied to the strip and the looper angle within their reference values.
The most difficult problem in looper control is to achieve simultaneously the interfering tension control and looper angle control. In recent years, a non-interactive control employing cross-controllers has been adopted and brought a dramatic increase in control accuracy, although the response time is limited. Thus, a new method with improved response time is desirable.
In this paper, a looper optimal multivariable control based on the optimal regulator theory employing a looper drive system with speed control loop is proposed. Other topics discussed includes the results of an investigation of simplifying the control system by the use of a programmable controller. In addition, it is demonstrated that the optimal multivariable control is effective compared with the conventional control and the non-interactive control as employed in the hot strip finishing mill of Hirohata Works of Nippon Steel Corporation.

View full abstract

Characteristics of rolling in hot roll bonding process has not been fully understood.
Some mathematical models and experimental simulation methods are developed to give the following results.
A rolling load model of cladding plates is established. Variation of cladding ratio in a clad plate in hot roll bonding process is quantitatively analyzed for the improvement of thickness accuracy can be expected. Furthermore, new techniques to improve the yield ratio in manufacturing are developed.

View full abstract

The hardness of adamite roll materials for hot work rolls depends on their microstructures; the amount and hardness of coarse carbides and the hardness of matrix. The high-hardened adamite roll materials are excellent in wear resistance when the amount of coarse carbides is about 8%, but the wear resistance deteriorates when the amount of coarse carbides \exceeds a critical level.
The reason is considered to be as follows: As the volume of coarse carbides increases, the spacing between coarse carbides decreases and the area of coarse carbides in contact with hot strip surfaces also increases, to induce a partial disintegration of brittle coarse carbides.
The high-hardened adamite rolls with about 8% of coarse carbides have a hardness from Hs 65 to 70 and can be used for hot work rolls with satisfactory results.

View full abstract

Three-dimensional analysis for strip rolling, in which elastic deformation of rolls and plastic deformation of a strip are treated as one system, is expanded to calculate the nonsymmetric deformation of both rolls and strip and applied to evaluate the off-centering or cambering of a strip and the fundamental characteristics of snaking of a strip. The phenomena of nonsymmetric rolling and off-centering or cambering of a strip can be predicted accurately by the present analysis.

View full abstract

A new compact multi-reduction mill (NCM), which can substitute one stand for two or three stands in a cold tandem mill, has been developed. This new mill is based on a three pass rolling in one stand and enables a 70% reduction in thickness in the cold rolling of mild carbon steel. The rolling experiments and numerical calculations showed that a strip-pulling-out type NCM rolling was more suitable than a strip-enveloping type NCM rolling and gave excellent characteristics in rolling lubrication, roll cooling and preventing heat scratch.

View full abstract

Increasing the rolling reduction in thickness in one mill stand contributes to realize a compact mill line and less initial and running cost.
For this purpose many studies about the effect of the work roll diameter in case of conventional mill were tried out and it was recognized that the maximum rolling reduction per stand is about 45-55% at most.
In order to achieve the high reduction over 70% in one cold rolling stand, “The three-gap rolling method” has been investigated. This New Compact Multi-Reduction Mill (NCM) consists of four work rolls arranged vertically in one housing and the strip is threaded through three roll gaps.
The practical stable rolling condition has been accomplished on a test mill by regulating the tension, roll speed difference, rolling force, etc. Such rolling characteristics as the number of work rolls to be driven, the conditions to realize the optimum inter-gap tensions, and the position of the neutral points have been investigated theoretically. Further the rolling characteristics such as rolling force, torque, tensions, forward slip, rolling energy, and the optimum rolling conditions have been investigated experimentally.
The new compact multi-reduction mill enables the high reduction over 70% in one stand and gives sound strip surfaces by applying improved lubrication.
Finally the possibility of practical applications for tandem cold mills and reversing cold mills are discussed.

View full abstract

Fundamental study on automatic gauge control (AGC) of reversing cold rolling mill was carried out. The study includes the method of evaluating performance of AGC system and designing a control system according to the results of the study.
It was concluded that the response of AGC system depends on the dynamic characteristics of a reel motor current control in either case of controlling reel motor current or roll position. The AGC system controlling the reel motor current is better than the AGC system controlling the roll position even with a hydraulic screwdown system.
A new AGC system controlling reel motor current and roll position has been developed based on the above results. This system has been applied to Sendzimir and 4-high reversing mills.

View full abstract