USRE28149E - Harbaugh etal rolling mill control system - Google Patents
Harbaugh etal rolling mill control system Download PDFInfo
- Publication number
- USRE28149E USRE28149E US28149DE USRE28149E US RE28149 E USRE28149 E US RE28149E US 28149D E US28149D E US 28149DE US RE28149 E USRE28149 E US RE28149E
- Authority
- US
- United States
- Prior art keywords
- gage
- mill
- exit
- stand
- stands
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
- B21B37/16—Control of thickness, width, diameter or other transverse dimensions
- B21B37/165—Control of thickness, width, diameter or other transverse dimensions responsive mainly to the measured thickness of the product
Definitions
- ABSTRACT OF THE DISCLOSURE Described is a rolling mill control system for tandem rolling mills based on the constant volume principle and wherein anticipated or predicted exit gage is calculated from measured entry gage and the length of material entering and leaving the mill. This predicted exit gage is compared with desired exit gage as determined by the mill operator to generate an error correction signal to the mill screwdowns if the predicted and desired gages are not the same.
- a mill screwdown or the like is controlled from a gage measurement taken several feet beyond the exit side of the mill.
- the material after reduction, progresses to the gage which may be several feet beyond the bite of the mill rolls before any error present in the material thickness can be detected.
- This distance ⁇ from the bite of the rolls to the gage is commonly referred to as transport distance.
- transport time The time required for the material to reach the exit gage
- sensing time Transport time and sensing time are major elements in developing error commands.
- Transport distances of ve feet or more are common in most of the commercial rolling equipment presently available, meaning that such systems are not capable of detecting an error signal until tive feet of material has passed from the bite of the mill rolls. The corrective signal is then transmitted to the mill screwdown; but the measuring gage does not detect the result of this action until five feet more of the material has passed through the mill.
- a high gain system of this type a natural frequency of oscillation results; and if this oscillation is left to exist without any attempt to control it, the results are undesirable. That is, for material entering the mill with fairly noticeable changes in gage, the system described would cause wide variations in output gage that in all probability would eventually result in tearing of the strip.
- an error signal for the rolling mill screwdown is derived by calculating the desired input gage, Fu, from the length of material entering the mill, the length of material leaving the mill, and calculated desired output gage, Gzd. Calculated desired input gage is then compared with the actual measured value of input gage. That is,
- the present invention seeks to provide a rolling mill control system based on the constant volume principle and wherein predicted exit gage is compared with desired exit gage to derive an error signal for the rolling mill screwdown.
- Another object of the invention is to provide a rolling mill control system of the type described for a tandem rolling mill wherein predicted exit gage is derived from a consideration of the actual gage of the material entering the rst stand of the mill, the length of the material entering the first stand, and the length of the material leaving the last stand.
- Still another object of theinvention is to provide a rolling mill control system which predicts exit gage which will occur if rolling conditions remain unchanged and wherein corrective control action can be taken with no exit gage error actually occurring.
- a rolling mill control system comprising means for deriving electrical signals proportional tothe actual gage, Gx, of the material entering the mill, the length, L1, of the material entering the mill over a given time interval, and the length, L2, of the material leaving the mill over said given time interval.
- Gx the actual gage
- L1 the length of the material entering the mill over a given time interval
- L2 the length of the material leaving the mill over said given time interval
- VConsequentllhe Vexit-gage can be predicted by cornparing the electrical signalsproportional to Gl, L1 and L3 in accordance with the equation:
- Errol' z-Ggd Errol' z-Ggd Additionally, actual output gage is measured to produce an electrical signal, G2, proportional to the actual measured output gage. This signal is averaged over a relatively long time period and compared with predicted exit gage, O2, averaged over the same relatively long time. If the two are not the same, an error signal is produced which alters the output of the circuitry for computing G3 until the averaged predicted exit gage matches the averaged actual output gage.
- the last stand is normally used for tempering purposes; and very little reduction is taken here. That is, almost all of the reduction in the material is taken in the first stands. Therefore, the error signal derived by comparing predicted exit gage with desired exit gage is fed to the screwdown controls for the first two stands only.
- the screwdowns for the first two stands in a three-stand tandem mill are moved the same amount by the exit gage regulator to correct for predicted exit gage gage error.
- the load force readings on the first two stands are averaged over a relatively long time and compared to each other. If the average load for the first stand exceeds that for the second, then the roll gap for the first stand is increased an additional amount. On the other hand, the roll gap for the first stand is decreased if the second stand load exceeds that on the first stand. In this manner, the loads on the two stands are kept nearly equal.
- the screwdowns for the first two stands are moved the same amount by the exit gage regulator to correct for predicted exit gage error.
- the exit gage of the first stand is averaged over a relatively long time and compared to the desired value set by the operator. If this measured gage is less than desired, then the first stand roll gap is in creased an additional amount. Conversely, the roll gap on the first stand is decreased if the measured gage is greater than desired. In this manner the exit gage of the first stand is kept near the desired value.
- the error signal produced by comparison of calculated exit gage with desired exit gage is used to control the tension in the strip, with or without screwdown correction, which tension also regulates the gage of the issuing strip.
- FIG. 1 is a schematic diagram of one embodiment of the invention wherein predicted exit gage is utilized to control the screws on the first two stands of a tandem rolling mill, and incorporating means including load sensitive devices under the screws for maintaining the loads on the first two stands nearly equal;
- FIG. 2 is a schematic illustration of an Valternative embodiment of the invention wherein the actual gage of the strip material between the first two stands is averaged over a relatively long period of time and utilized to maintain the exit gage of the first stand in a tandem rolling mill near the desired value;
- FIG. 3 is a plot of entry velocity of strip material passing through the mills of FIGS. l and 2 versus the prediction time of the control system shown therein;
- FIG. 4 illustrates other possible control schemes embodying the principles 0f the invention.
- a tandem rolling mill including three stands identified by the reference numerals 10, 12 and 14.
- Each stand includes an outer housing 16 which supports upper and lower rolls 18 and 20, the spacing or gap between the rolls being controlled by means of a screwdown mechanism generally indicated by the reference numeral 22.
- Each screwdown mechanism 22, in turn, is controlled by means of a screwdown control 24 which conventionally includes a drive motor mechanically connected to the screwdown mechanism itself, t0- gether with electrical controls for the drive motor.
- the material being reduced in the mill is identified by the reference numeral 26. As will be appreciated, the material is successively reduced in thickness as it passes between the rolls 18 and 20 of each stand.
- a first X-ray thickness gage 28 At the entrance end of the mill is a first X-ray thickness gage 28 which produces an electrical signal on lead 30 proportional to the thickness of the entering strip material.
- an X-ray gage 32 measures the thickness of the strip material as it emerges from the third or last stand 14.
- the signal on lead 30 is passed through a gate 34 to a binary digitizer 36 where it is converted into a plurality of ON and OFF signals representative of the measured input gage in binary notation. These ON and OFF signals are then applied to the input of a shift register or the like, identified by the reference numeral 38.
- a pulse generator 42 which will produce output pulses on lead 44, the frequency of the Output pulses being proportional to the speed of the entering strip material. These pulses are applied to an L, counter 46 as well as an interval counter 48.
- a roll 50 riding on the surface of the strip material emerging from the last stand 14 is mechanically coupled to a second pulse generator 52 which will produce output pulses on lead 54 having a frcquency proportional to the speed of the emerging strip material. These pulses are applied to an L4 counter 56.
- the interval counter 48 is preset to count up the number of pulses which will be produced by the generator 42 each time the entering strip material travels one foot. Consequently, each time the strip material travels through one foot, the gate 34 is opened, the L1 counter 46 is reset, and the L., counter S6 is also reset. At the same time, a shift pulse from the interval counter 48 is applied to the shift register 38 to advance gage measurements stored therein to successive storage units until they reach the output.
- the shift register 38 serves to store and advance successive actual entry gage measurements from gage 28 in synchronous correlation with the movement of strip 26. That is, each time the gate 34 is enabled by the interval counter 48, it feeds the instantaneous entry gage measurement to the binary digitizer which, in turn, feeds the information in binary form to the shift register 38 which progressively advances these instantaneous measurements from one end of the shift register to the other.
- the time required to advance from one end of the shift register 38 to the other is equal to the time required for the strip 26 to travel from the gage 28 to the bite of the rolls in stand 10.
- the gage 28 is spaced six feet in front of the bite of rolls 18 and 20 for stand i form, is fed into the lirst storage unit of the shift register '38. After the strip has traveled another foot, the gate is again opened and the instantaneous gage measurement again fed into the shift register 38; however by this time the previous gage measurement has been advanced one unit in the shift register 38. This process continues until six feet of material has passed from the gate to the bite of the rolls; and it will be appreciated that at this time the gage measurement taken at a point which now has progressed six feet beyond the gage 28 will be directly at the bite of the rolls 18and 20 of stand 1I).
- the output of the binary digitizer 36 is representative of actual input gage, G1, and must be used to compute predicted exit gage which is compared with desired exit gage to generate an error signal for the rolling mill screwdowns. There is, however, a certain time delay between generation of an error signal and response to that signal by the mill screwdowns.
- the time elapse i.e., prediction time
- the prediction time decreases from about four seconds at a strip speed of 90 feet per minute to about 0.5 second at 720 feet per minute.
- the mill screwdown cannot respond in this time. It is, of course, desirable to make an error correction as quickly as possible after it is detected; and at lower speeds below about 18() feet per minute, the mill screwdown can respond well in advance of the prediction time.
- the input gage signal, Gl is taken from the lirst unit of the shift register on lead 58. That is to say, there is no delay in the shift register.
- the lead 58 is connected to units farther down the shift register so that the mill, in effect, is responding to gage measurements taken closer to the bite of the rolls than six feet. Circuitry for accomplishing this will hereinafter be described in detail.
- the interval counter 318 resets the L1 counter 46 and L, counter 56 for each foot of strip travel. Consequently, the outputs of the L1 counter 46 and L, counter 56 will be electrical signals indicative of the length of material which has passed into and out of the mill between successive gage measurements. These electrical signals are applied via leads 60 and 62 to a computer exit gage regulator circuit which performs the computation:
- G1 X L1/L4 this being equal to predicted exit gage, G2, as explained above.
- the predicted exit gage at the output of computer circuit 64 is then applied via lead 66 to a comparator 68 where it is compared with an electrical signal proportional to desired exit gage, Gm, from circuit 70.
- the value of the electrical signal, Gm is set by the operator. If the elec trical s ignal on lead 66 proportional to predicted exit gage, G2, is not equal to the magnitude of the electrical signal from circuit 70 proportional to desired exit gage, Gm, an output will be produced on lead 72 from comparator 68 which is applied to the screw control circuits 24 for stands 10 and 12, thereby causing them to move upwardly or downwardly, depending upon whether G2 is larger or smaller than Ggd.
- the material need not move though the mill before an error in gage can be anticipated.
- the output of the exit gage 32 is applied to a binary digitizer 74; and the output of this digitizer is applied to an averaging circuit 76 where it is stored. This stored, averaged value of exit gage is then compared with the averaged or computed predicted exit gage from computer circuit 64 in comparator 78. If the two are not the same, a signal is applied via lead 80 to the computer circuit 64 to vary its output such that actual measured exit gage and average computed exit gage are the same. It should be understood, however, that the circuitry including gage 32 and comparator 78 does not, in and of itself, control the rolling mill as in a conventional feedback system. Rather it is used only as a monitor for the computing circuit 64 to make certain that average predicted exit gage is, in fact, equal to average actual exit gage.
- the exit gage predictor 64 furnishes information for the screw controls 24 to take control action with the purpose of adjusting rolling conditions such that any predicted gage error will not occur. It is possible to construct a regulator which adjusts or causes to be adjusted any mill setting which will cause the exit gage to change. Since any mill setting which affects exit gage also affects other mill parameters, the manipulated settings must be chosen with consideration for possible undesirable effects on mill operations.
- the computer 64 effects control by varying the screwdown setting of stands 10 and l2. However, a strategy is required to determine the relative amount of screw movement between stands 10 and 12.
- FIG. l one arrangement is shown for determining the amount of screw movement between stands 10 and 12 which incorporates load cells 90 and 92 on the screws for stands 10 and 12.
- the output, of the load cells 90 and 92 comprises electrical signals which are proportional to the rolling forces on the respectives stands. Electrical signals proportional to roll force are averaged over a relatively long time in circuits 94 and 96 and compared with each other in comparator 98. If the average load on stand 10, for example, exceeds the average load on stand 12, then the output of the comparator 98 will be such as to actuate the screw control 24 for stand 10 to increase the gap between its rolls. On the other hand, the roll gap is decreased if the load on stand 12 exceeds that on stand 10. In this manner, the loads on stands 10 and l2 are kept nearly equal.
- FIG. 2 an alternative embodiment of the invention is shown wherein elements corresponding to those shown in FIG. 1 are identified by like reference numerals.
- the screws for stands 10 and 12 are moved the same amount by exit gage regulator or computer 64 to correct for a predicted exit gage error.
- the exit gage of stand l0 as measured by X-ray gage 100 is averaged over a relatively long time in circuit 102 and compared in comparator 104 with a signal from circuit 106 proportional to the manual setting of the desired exit gage for stand 10 as determined by the operator. If the thickness as measured by gage 100 is less than desired, then stand 10 roll gap is increased an additional amount by screw control 24. On the other hand, the roll gap is decreased if the measured gage is greater than desired. In this manner, the exit gage from stand 10 is kept near the desired value.
- the screw on the third stand 14 can be adjusted to maintain the roll force on this stand at an operators desired value for the purpose of maintaining the roll bending and thus the steel shape more constant.
- the exit gage regulator or computer 64 can manipulate steel tension through a tension regulator reference to effect exit gage regulation.
- FIG. 4 Other possible control schemes are shown in FIG. 4.
- the basic system shown in FIG. 4 is the same as that of FIGS. 1 and 2 and, accordingly, elements in FIG. 4 which correspond to identical elements in FIGS. 1 and 2 are identified by like reference numerals.
- the system of FIG. 4, however, incorporates additional control features.
- the length, L2 of the material leaving the rst stand 10 can be determined by means of an L2 counter 108 having its input connected to a pulse generator 110 which is, in turn, connected to a roll 112 on the exit side of the stand 10.
- the L2 counter 108 is reset, along with counters 46 and 56, after each foot of strip travel. Its output is applied to an exit gage predictor or computer 114. Also applied to the predictor 114 is the output of L1 counter 46 and the entry gage measurement from gage 28.
- the computer 114 computes the quantity:
- This factor represents the predicted exit gage at the output of the first stand l in accordance with the explanation given above.
- the predicted exit gage from stand is then applied via lead 116 to a comparator 118 where it is compared with a gage value for the lirst stand determined by an operator adjust circuit 120. It will be appreciated that with the arrangement shown, the gage 100 between the first two stands can be eliminated; and the rst stand gage is controlled independently in much the same manner as the entire tandem rolling mill is controlled.
- gage at the output of the second stand 12 can be determined in accordance with the constant volume principle:
- a pulse generator 122 is connected to a roll 124 between stands 12 and 14. The output of this pulse generator 122 is then applied to an L3 counter 126 which, like counters 46 and S6, is reset by the interval counter 48 for each foot of strip travel. The output of the L3 counter 126 is applied to computer 128 along with the electrical signal on lead 62 proportional to L4 and the gage measurements on lead 130 from exit gage 32. The output of the computer 128, therefore, will be proportional to the desired gage at the output of stand 12. In this case, however, the gage is not predicted but is rather calculated after the material has passed through the stand.
- the output of the computer 128 is then compared in comparator 132 with a preset value established by an operator adjust circuit 134; and if the two are not the same an error signal is fed to the screw control 24 for stand 12 to raise or lower the rolls, as the case may be.
- a system for controlling a rolling mill gage varying device in accordance with the principle of constant volume of material entering and leaving the mill by compariSon of calculated exit gage with desired exit gage including electrical computer apparatus for deriving calculated exit gage by comparison of actual input length of material entering the mill, actual output length of material leaving the mill and actual measured gage of material entering the mill, [and] means coupled to said computer apparatus for comparing an electrical signal proportional to the exit gage calculated by the computer apparatus with an electrical signal proportional to desired output gage as determined by the mill operator to derive an error signal for said gage varying device means for measuring the actual exit gage of material leaving the mill, means for comparing the measured actual exit gage with calculated exit gage, and means connecting said comparing means to said com puter apparatus for varying the output of the compuler apparatus when calculated exif gage and actual exit gage are not the same.
- gage varying device comprises means for varying the roll force exerted by the rolls of said rolling mill.
- gage varying device comprises means for varying the tension in material passing through the mill.
- the mill includes a plurality of tandem stands, the actual input length of material entering the mill is that entering the rst stand, and the actual output length of material leaving the mill is that leaving the last stand.
- the system of claim 1 including means for measuring the actual exit gage of material leaving the mill, means for comparing the measured actual exit gage with calculated exit gage, and means connecting said comparing means to said computer apparatus for varying the output of the computer apparatus when calculated exit gage and actual exit gage are not the same] 6.
- a system for controlling the exit gage of material passing through a plurality of tandem rolling mill stands the combination of means for producing a trst electrical signal proportional to a calculated gage of material passing through the mill from a consideration of an actual gage measurement of material passing through the mill and the actual lengths of material entering and leaving the mill over a predetermined period of time, means for comparing said first electrical signal with a second electrical signal to derive an error signal, said second electrical signal being a function of the desired output gage of material leaving the mill as determined by the mill operator, screwdown mechanisms for said tandem stands, and means responsive to said error signal for controlling the screwdown mechanisms on stands preceding the last stand only.
- the system of claim 7 including means for measuring the roll forces on said lirst two stands, means for comparing the measured roll forces, and means coupled to said last-mentioned comparing means for actuating the screwdown on at least one of said rst two stands when the measured roll forces are not the same.
- the system of claim 7 including means for measuring the actual gage of material passing between the first two stands, means for comparing said measured gage between the first two stands with the gage setting for the rolls on the first stand, and means for actuating the screwdown for said first stand when the measured gage between the first two stands is not the same as said gage setting.
- the means for producing electrical signals proportional to L1 and L2 includes a rst pulse generator for generating a number of pulses proportional to L1, a second pulse generator for generating a number of pulses proportional to L2, a first counter for counting the pulses from said rst pulse generator, a second counter for counting the pulses from the second pulse generator, and means for resetting said counters simultaneously each time material passing through said mill has moved through a predetermined distance.
- said rolling mill includes a plurality of tandem stands and including means for measuring actual output gage from the first stand of the mill, and means for comparing said actual measured gage at the output of the stand with the gage setting for that stand as determined by the mill operator to derive an error signal for controlling the screwdown for said first stand.
- said rolling mill includes a plurality of tandem stands, means for measuring the roll forces on the first two stands in said plurality of stands, means for comparing said roll forces on the iirst two stands, and means coupled to said comparing means for controlling the screwdowns for said first two stands.
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Control Of Metal Rolling (AREA)
Abstract
MILL SCREWDOWNS IF THE PREDICTED AND DESIRED GAGES ARE NOT THE SAME.
Description
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US40251073A | 1973-10-01 | 1973-10-01 |
Publications (1)
Publication Number | Publication Date |
---|---|
USRE28149E true USRE28149E (en) | 1974-09-03 |
Family
ID=23592207
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US28149D Expired USRE28149E (en) | 1973-10-01 | 1973-10-01 | Harbaugh etal rolling mill control system |
Country Status (1)
Country | Link |
---|---|
US (1) | USRE28149E (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20110113848A1 (en) * | 2009-11-16 | 2011-05-19 | Quad Engineering Inc. | Methods for reducing ridge buckles and annealing stickers in cold rolled strip and ridge-flattening skin pass mill |
-
1973
- 1973-10-01 US US28149D patent/USRE28149E/en not_active Expired
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20110113848A1 (en) * | 2009-11-16 | 2011-05-19 | Quad Engineering Inc. | Methods for reducing ridge buckles and annealing stickers in cold rolled strip and ridge-flattening skin pass mill |
US8365563B2 (en) * | 2009-11-16 | 2013-02-05 | Quad Engineering, Inc. | Methods for reducing ridge buckles and annealing stickers in cold rolled strip and ridge-flattening skin pass mill |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US3561237A (en) | Predictive gauge control method and apparatus for metal rolling mills | |
US3564882A (en) | Rolling mill control system | |
US3613419A (en) | Rolling mill automatic gauge control with compensation for transport time | |
US3636743A (en) | Rolling mill control system | |
US3044297A (en) | Measuring system | |
USRE28149E (en) | Harbaugh etal rolling mill control system | |
US4398254A (en) | Method for controlling strip thickness in strip mill | |
US3841123A (en) | Rolling mill gauge control method and apparatus including entry gauge correction | |
KR890000118B1 (en) | Rolling mill control system | |
US3688532A (en) | Control system for tandem rolling mill based on the constant volume principle | |
US3768286A (en) | Interstand tension regulator for a multistand rolling mill | |
US3290912A (en) | Rolling mill control apparatus | |
US3702071A (en) | Gauge control method and apparatus for metal rolling mills | |
US4557126A (en) | Control device for continuous rolling machine | |
US3709008A (en) | Gauge control method and apparatus for metal rolling mills | |
US3820366A (en) | Rolling mill gauge control method and apparatus including temperatureand hardness correction | |
US3782153A (en) | Method and system for controlling a tandem rolling mill | |
EP0075944B1 (en) | Control device for successive rolling mill | |
JP2536970B2 (en) | Plate thickness measurement method | |
JPS6150047B2 (en) | ||
SU763014A1 (en) | Device for controlling strip thickness in rolling within the negative tolerance field | |
JP2562011B2 (en) | Shape control method for continuous rolling mill | |
JPH0262327B2 (en) | ||
JPH0390207A (en) | Meandering control method of plate rolling time | |
JPS631124B2 (en) |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: ALLEGHENY LUDLUM CORPORATION Free format text: CHANGE OF NAME;ASSIGNOR:ALLEGHENY LUDLUM STEEL CORPORATION;REEL/FRAME:004779/0642 Effective date: 19860805 |
|
AS | Assignment |
Owner name: PITTSBURGH NATIONAL BANK Free format text: SECURITY INTEREST;ASSIGNOR:ALLEGHENY LUDLUM CORPORATION;REEL/FRAME:004855/0400 Effective date: 19861226 |
|
AS | Assignment |
Owner name: PITTSBURGH NATIONAL BANK Free format text: ASSIGNMENT OF ASSIGNORS INTEREST. RECORDED ON REEL 4855 FRAME 0400;ASSIGNOR:PITTSBURGH NATIONAL BANK;REEL/FRAME:005018/0050 Effective date: 19881129 |