USRE26996E - Computer control system for metals rolling mill - Google Patents

Description

Dec. 8, 1970 R. G. BEADLE ETAL Re. 26,996

COMPUTER CONTROL SYSTEM FOR METALS ROLLING MILL 18 Sheets-Sheet 1 Original Filed Dec. 10, 1963 kw? mOEa Dec. 8, 1970 BEADLE ETAL Re. 26,996

COMPUTER CONTROL SYSTEM FOR METALS ROLLING MILL 18 Sheets-Sheet 2 Original Filed Dec. 10, 1963 Dec. 8, 1970 R. G. BEADLE ETA!- COMPUTER CONTROL SYSTEM FOR METALS ROLLING MILL Original Filed Dec. 10, 1963 FIG.

FIG. FIG. FIG.

2B 2C 2D FIG.2 PRIOR ART l8 Sheets-Sheet 3 GR-I Dec. 8, 1970 R. G. BEADLE ErAL Re. 26,996

COMPUTER CONTROL SYSTEM FOR METALS ROLLING MILL 18 Sheets-Sheet 4 Original Filed Dec. 10, 1963 Dec. 8, 1970 R. G. BEADLE ETAL Re. 26,995

COMPUTER CONTROL SYSTEM FOR METALS ROLLING MILL l8 Sheets-Sheet 5 Original Filed Dec. 10, 1963 FIG.2C

Dec. 8, 1970 R. G. BEADLE ETAL Re. 26,996

COMPUTER CONTROL SYSTEM FOR METALS ROLLING MILL Original Filed Dec. 10, 1963 18 Sheets-Sheet 6 G R'G ,VXR

FIG.2D

Dec. 8, 1970 BEADLE E'I'AL Re. 26,996

COMPUTER CONTROL SYSTEM FOR METALS ROLLING MILL l8 Sheets-Sheet '7 Original Filed Dec. 10, 1963 FIG.3

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COMPUTER CONTROL SYSTEM FOR METALS ROLLING MILL 18 Sheets-Sheet 8 Original Filed Dec. 10, 1963 Ill IIIL r lllllll II .I .11.}?! u m u m n .l T HL HIL m n n u 4 Q 9 n u n mm me: n IRMV u n m If a W F u m R. NON h ll IZII. w n 4 n u I H II v III J H u 0 L n n m imv r 6 QB v u on .llr (J\||\ ..I uh v0 1970 R. G. BEADLE E L COMPUTER COXTROL SYSTEM FOR METALS ROLLING MILL 18 Sheets-Sheet 9 Original Filed Dec. 10, 1963 mmdi Dee. 8, 1970 R. G. BEADLE EI'AL Re. 26,996

COMPUTER CONTROL SYSTEM FOR METALS ROLLING MILL l8 Sheets-Sheet 10 Original Filed Dec. 10, 1963 R. G. BEADLE ErAL Re. 26,996

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COMPUTER CONTROL SYSTEM FOR METALS ROLLING MILL 18 Sheets-Sheet 12 Original Filed Dec. 10, 1963 FZmZOmZOO mmhDQZOO .ZEFDO Im I I l I l I JQEFZOO IIIIII III'IIIIIIIII'IIII'III'IIIII'IIII lllllvl. all I ll IIII'lI-lll'llllllll'lllllnblll II'IIII'Ill-lllllllll'llli [I ll-Ill mmdl Dec. 8, 1970 R. a. BEADLE ETAL Re. 26,996

COMPUTER CONTROL SYSTEM FOR METALS ROLLING MILL 18 Sheets-Sheet 13 Original Filed Dec. 10, 1963 m mmIm Ema m o I 56E $61 8 0m MU QEEIQEE 055 05? 36E mmoi m w .I.ll|||.l|| 1|. It'll-l l-l IIL' Dec. 8, 1970 R. G. BEADLE ETAL Re. 26,996

COMPUTER CONTROL SYSTEM FOR METALS ROLLING MILL Original Filed Dec. 10, 1963 18 Sheets-Sheet 1L ALOG OUTPUT 1970 R. G. BEADLE Er L 26,996

COMPUTER CONTROL SYSTEM FGR METALS ROLLING MILL Original Filed Dec. 10, 1963 18 Sheets-Sheet 15 o c (D n a: 2 O c I: x x o .2 E c F r- D L 2 c 90.105 numou 3 I to I a: g 50 2 ANALOG OUTPUT Dec. 8, 1970 R. G. BEADLE ETAL Re. 26,996

COMPUTER CONTROL SYSTEM FOR METALS ROLLING MILL 18 Sheets-Sheet 16 Original Filed Dec. 10, 1963 4ndu Jamo 80.805 JO 4ndu1 JGMOd Dec. 8, 1970 R. cs. BEADLE ETAL Re. 26,996

COMPUTER CONTROL SYSTEM FOR METALS ROLLING MILL l8 Sheets-Sheet 17 Original Filed D80. 10, 1963 FIGJZSG D B G F Thickness (input) 5O 75 I00 I25 EZ s 3.5a

Tmolmua (mill) 3, 1970 R. G. BEADLE ETAL Re. 26,996

COMPUTER CONTROL SYSTEM FOR METALS ROLLING MILL 18 Sheets-Sheet 18 Original Filed Dec. 10, 1963 STAND$ m a H m n F E R T S g m .m w m L F M m 2 m K O F 5 R a T s I K .L p 1 v F A wOmOu 25:35am Q United States Patent Int. Cl. B2111 37/12 US. Cl. 72-7 37 Claims Matter enclosed in heavy brackets appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

ABSTRACT OF THE DISCLOSURE Methods and apparatus are disclosed for rolling hot steel strips in a multistand mill, preferably with a computer to perform multiple control functions rapidly. Performance is enhanced by determination of driving power for each stand and interstand gages are derived from stored data representing the appropriate one of a stored family of cumulative power curves, each applicable for a different range of delivery gages. Individual stand speeds are established from the mass flow relation based upon the desired final stand speed and delivery gage fed into the system, with forward slip taken into account. From the determined interstand gages, the forces to be exerted by the respective stands are derived from stored data representing the appropriate one of a family of cumulative force vs. thickness curves, each curve being applicable for a different range of delivery gages. Such force values are then used to derive from stored, nonlinear stretch curves, the individual stand stretches which are combined with the determined interstand gages to establish commands for screw setting servos, thereby to adjust the unloaded roll openings appropriately for the desired interstand gages. Screw settings can be corrected according to exponential functions of the times when hot metal is present or absent in the stands, thereby to compensate for thermal expansion or contraction.

The determined driving powers and speeds for the several stands are compared with stored values of rated or limit power and speed capabilities, and if the commanded values fall outside the limits, the setup commands are determined again with different power proportioning, or at dlfifreltl final stand speed, or the operation of the system is terminated if impossible operating conditions are called for.

Errors in interstand gages during actual rolling of a steel strip, as determined by comparing values derived from load cell signals (gagemeter gages and actual speed and delivery gage sensor signals (mass flow gages), are used to partially update factors included in the stored data, so that set-up determinations for subsequent strips will become progressively more accurate. This is called adaptive interstand gage feedback. Also, the sensed actual driving powers for the several stands during rolling of a strip are compared with the powers calculated from the appropriate one of the stored power curves based upon actual interstand gages, and any errors are used to partially update factors included in the stored data, so that set-up determinations for subsequent strips will become progressively more accurate. This is called adaptive load distribution feedback. For adaptive roll speed feedback, commanded roll speeds are compared with actually measured roll speeds during rolling of a strip, and any errors are employed to partially update factors included in the stored data, so that setup for subsequent strips Re. 26,996 Reissued Dec. 8, 1970 will become progressively more accurate. Adaptive roll force feedback is accomplished by computations comparing actual roll forces sensed by load cells with predicted forces calculated from stored force curve data and interstand gages actually being rolled on a strip, and by utilizing any discrepancies to partially update factors included in the stored data, so that set-up for successive strips becomes more accurate. Such adaptive feedback corrections inherently reflect the particular characteristics of the steel being rolled and of the mill being controlled, and automatically compensate for the steel characteristics and for changes in mill characteristics due to aging or wear.

This invention relates to the rolling of steel and means for controlling such operations automatically.

More specifically, the invention relates to the automatic operation of a hot strip steel mill under the direction of a control computer. In this connection the computer not only carries a stored operational program, but also is arranged to receive input and external control data for combination therewith and to make regular inspections of the results of its own operational control data for further combination therewith and subsequent updating of its stored program.

A feature of the invention is the monitoring and accrual of data determined from one cycle of operation for modifying control data for a succeeding cycle of operation. This updating feature is brought about through automatically recaleulating certain critical input data necessary to the proper functioning of the strip mill control set-up.

Another feature of the invention is the automatic checking of a strip mill operation by comparison of calculated data and actual operational data through a part of the cycle of operation whereby disagreement between these data brings about a corrective control set-up."

The art of working metals is exceedingly old, and the art of rolling steel until recently might be considered to have been a craft. Basically a major part of the activities of the modern steel industry is not metallurgy, or the production of steel from its raw constituents, but the reduction in size of a quantity of steel to predetermined dimensions. Refinement in the production of steel bars, rails, rods, plates and strips has been made continually over the years; however, this production has been accomplished under strictly manually controls, the skill of the operator manipulating the controls being all important. With the advent of multiple stand, rolling mills, and particularly in the production of steel plates, sheets or strips, certain semiautomatic devices have been developed from time to time for the purpose of improving the accuracy of the process and the quality of the products; nevertheless, until the present invention materialized steel has been rolled almost exclusively under the control of human operators.

Initially, the rolling mill operator may be considered to have had a simple task. His job consisted merely in setting a pair of rolls to exit ductile metal of a predetermined Width and thickness different from that entering the rolls. However, trial and experiment, together with advance in metallurgical concepts, proved conclusively that the quality of the finished product depended upon more than the mere squeezing of the metal from one cross-sectional area to another. As a result the operator of a rolling mill became confronted with additional factors such as rolling speed, rolling temperature, intcrstand tension, scaling, roll wear, and many other facets entering into the production of finished steel material. Each operator thereafter became skilled in the manner of production according to his calculated hunch," based primarily upon his dexterity at manual manipulation according to past and current observations of the rolling process.

As further refinements and specifications became more and more demanding of the outputs of steel rolling mills certain semi-automatic controls were introduced to assist the operator during rolling operations; e.g., the gage control system illustrated in US. Patent 2,726,541, and devices such as these, together with so called looper controls for preventing loops or "cobbles" between stands of a strip mill. These rolling mill modifications improved the operators chances of meeting the rolling requirements. Nevertheless, the current requirements of a steel rolling mill leave much to be done by the mill operator that appears to be beyond his ability to do or comprehend within the time limits conducive to economical production.

For example, in a six stand, multiple stand hot strip mill the operator, prior to commencing the rolling operation, must:

(a) Ascertain the finish gage (thickness).

(b) Ascertain the finish width.

(c) Ascertain the finish temperature.

(d) Know the type of steel.

(e) Know the entry temperature.

(f) Know the characteristics of the steel being rolled.

(g) Know the mill condition, e.g., which rolls may be worn, etc.

(h) Know the drafting practice for the mill under the conditions of (g).

(i) Know the proper speed of rolling to produce the desired finish temperature.

Keeping the above factors in mind, the operator must also work out the mill set-up" at least for the follow- (l) Speeds for 6 stands (each may be different).

(2) Screwdown settings (roll openings) for 6 stands (each may be different).

(3) Sideguide settings for 7 positions along the rolling path.

(4) Initial X-ray setting.

During the rolling process the operator must also perform certain tasks necessary to the successful production of the desired items being rolled; e.g., the operator must:

(I) Control the speed of each stand, or be prepared to do so.

(II) Continually observe the looper heights, and be prepared to act.

(III) Continually observe output gage of the mill, and be prepared to make corrections when necessary.

(IV) Continually observe and be prepared to correct screwdown settings.

(V) Record observations in the category of [(1) to (6)] (I) to (1V), above, to improve mill set-up."

(VI) Level the mill stands.

(VII) Be alert for emergencies.

Bearing in mind all of the above-noted duties and responsibilities, it is quite obvious that the rolling mill operator must be indeed a unique individual, if not an [artst,] artist, in the manipulation and operation of the multitude of activities necessary to be followed to deliver finished steel strip according to modern requirements.

It is, therefore, an object of this invention not only to provide certain improvements of setup and control of the operation of a hot strip mill for automatically performing the customary duties of the mill operator, but also to take over the actual operational control of the mill; i.e., to materially automate the steel rolling process.

[An essential component of the invention is provided by a computer of the type described and claimed in co-pending applications Ser. Nos. 70,549, Patent No. 3,311,885; 74,975, 74,976 and 76,220 filed respectively Nov. 21, 1960, Dec. 9, 1960, Dec. 9, 1960 and Dec. 16, 1960. The latter three are now US. Patent Nos. 3,461,855, 3,461,856 and 3,461,857. It is to be pointed out, how-] A computer suitable for use in the practice of the present invention is described in copending application Serial No. 70,549, filed November 21, 1960 and assigned to the assignee herein, and US. Patents Nos. 3,311,855; 3,161,855; 3,161,856 and 3,161,857. It is to be pointed out, however, that the inclusion of a computer component is not merely the establishment of a programmed operation in the process of rolling steel since in the present invention the computer performs functions outside the realm of its program in accordance with past and current conditions of operation, making decisions to optimize operating conditions, updating its own stored data for future operations of like nature, and halting a current operation when the conditions of operation indicated by the set-up or control become impossible of performance.

The principal functions of the computer component normally, as explained in detail hereinafter, are concerned with:

(a) Finish gage (from order sheet);

(b) Finish temperature (from order sheet);

(c) Type of steel (from order sheet);

(d) Deviation from normal drafting (from operator);

(e) Entry temperature (from sensors);

(f) Entry gage (from sensors);

(g) Entry width (from sensors);

(h) Stand speeds (set up by computer);

(i) Screwdown control settings (set up by computer);

(j) Initial gage control settings (set up by computer);

(k) Sideguards (set up by computer);

(1) X-ray gage datum (set up by computer).

Under these conditions the mill operator, therefore, is required to be responsible for the mill condition and speed/temperature characteristics to be fed to the computer input prior to mill set-up, and during the actual rolling operation to be prepared to meet emergencies and [handles] to handle such matters as levelling of the mill stands when required.

It is therefore an object of this invention to provide an automated steel rolling mill system wherein the active participation of a mill operator is normally only incidental to the completion of the process.

Another object of the invention is to provide an automated steel rolling mill system wherein the control of all operations is normally directed by a computer.

The subject invention is not to be confused with a mere stored program type of operation, one of the features of the system being not only to resolve and compute data derived from stored and current inputs, but also to constantly revise or update data from recorded operational functions previously directed and store such data for future references.

It is therefore another object of the invention to provide an automated steel rolling mill system having both data storing and data monitoring capabilities whereby the former characteristic is continually modified by the latter characteristic.

Still another object of the invention is to provide an automated steel rolling mill system having means for making operational control decisions resulting from data derived from one cycle of operation for modifying control decisions in a subsequent cycle of operation.

The invention is set forth with particularity in the appended claims. The principles and characteristics of the invention, as well as other objects and advantages are revealed and discussed through the medium of the illustrative embodiments appearing in the specification and drawings which follow.

In the drawings:

FIGURE 1, comprising FIGURES 1A and 1B, is a schematic view of a hot strip mill illustrating the basic requirements of control necessary to be exercised by a mill operator.

FIGURE 2, comprising FIGURES 2A, 2B, 2C and 2D, is a schematic view of a hot strip mill showing some of

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