US3927545A - Rolling method for rolling mills - Google Patents

Rolling method for rolling mills Download PDF

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Publication number
US3927545A
US3927545A US568193A US56819375A US3927545A US 3927545 A US3927545 A US 3927545A US 568193 A US568193 A US 568193A US 56819375 A US56819375 A US 56819375A US 3927545 A US3927545 A US 3927545A
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Prior art keywords
rolling
rolling reduction
value
reduction
passes
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Expired - Lifetime
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US568193A
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English (en)
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Yasuo Morooka
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Hitachi Ltd
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Hitachi Ltd
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    • 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

Definitions

  • the mean rolllng reductlon 18 selected as a rolhng [58] Field 01 Search 72/6, 8, 16, 13, 19 reduction P in initial and terminating stages of the rolling operation, while a value larger 5 References Cited than the mean rolling reduction is selected as a rolling UNITED STATES PATENTS reduction for each pass in other stages, whereby the sum of the rolling reductions obtained in all the passes 3 can made equal to the product of the mean rolling 3:600:9l9 8/l97l Sindzingrezz 1111111111..
  • FIG. 1 A first figure.
  • This invention relates to rolling methods for rolling mills, and more particularly it deals with a rolling method for rolling mills which is suitable for carrying out rolling in a minimum period of time, and effecting temperature control and contour control.
  • the reduction in temperature due to air cooling is proportional to the entire surface area of the rolled material, so that if the value of a rolling reduction for each pass in initial stages of the rolling operation is high, then the rolled material will show a great reduction in temperature in passing it in initial stages of the operation and its temperature will become too low when it is passed in terminating stages of the operation. As a result, the temperature of the rolled material will be below the predetermined level when the rolling operation is completed.
  • this device operates satisfactorily when the rolling load is below a range between 700 to 800 tons. It will thus be seen that it is essential that the temperature of the rolled material be in the neighborhood of a suitable value when it is 2 passed in terminating stages in order satisfactorily to effect contour control of the rolled products.
  • a principal object of the present invention is to provide a rolling method for rolling mills which enables to produce rolled products of high quality in a stable manner by obviating the afore-mentioned problems raised in effecting temperature control and contour control in rolling methods of the prior art.
  • Another object of the invention is to provide a rolling method for rolling mills wherein no high loads are ap plied to the rolling mill and the screwdown electric motor.
  • Another object of the invention is to provide a rolling method for rolling mills which enables to satisfactorily effect temperature control and contour control in a simple and practical manner.
  • the outstanding characteristics of the invention are that at first a mean rolling reduction Ah and the number n of passes in which the desired total rolling reduction is achieved in a minimum period of time are ob tained from the rolling specifications including the hardness of rolled material, the allowable maximum rolling load, the allowable maximum rolling torque, the limit of the biting angle, the desired thickness of sheet material at the exit side of the rolling mill and the desired temperature at the exit side of the rolling mill, and the detected values of the thickness and temperature of sheet material at the exit side of the rolling mill, and then the rolling schedule is determined such that pass ing is effected in initial and terminating stages of the operation with a rolling reduction of a value lower than the mean rolling reduction Ah and yet the total rolling reduction achieved is equal to the product of the mean rolling reduction Ah and the number n of passes in which the desired total rolling reduction is achieved.
  • One of the features of the invention is that, in calculating a mean rolling reduction, a maximum limit rolling reduction, a load rolling reduction and a torque limited rolling reduction are obtained and the smallest value of these rolling reductions is used.
  • Another feature of the invention is that, in calculating the number of passes, the ratio of the desired total rolling reduction to a value obtained by multiplying the smallest value of the rolling reductions by a coefficient smaller than one, is obtained and the value obtained is used as the number of passes by counting the fraction of the value as a whole number.
  • Another feature of the invention is that, in calculating the number of passes, the ratio of the desired total rolling reduction to a value obtained by multiplying one of the maximum limit rolling reduction, the load limited rolling reduction and the torque limited rolling reduction by a coefficient smaller than one is obtained and the value obtained is used as the number of passes by counting the fraction of the value obtained as a whole number.
  • Another feature of the invention is that, in calculating the number of passes, the ratio of the desired total rolling reduction to a value obtained by multiplying the mean value of the maximum limit rolling reduction, the load limited rolling reduction and the torque limited rolling reduction by a coefficient smaller than one is obtained and the value obtained is used as the number of passes by counting the fraction of the value obtained as a whole number.
  • Another feature of the invention is to calculate the load limited rolling reduction by using the detected values of the temperature and thickness of material to be rolled.
  • Another feature of the invention is to calculate the torque limited rolling reduction by using the detected values of the temperature and thickness of material to be rolled.
  • Another feature of the invention is to obtain a rolling reduction for each pass in initial and terminating stages of the rolling operation as the product of the mean rolling reduction and a distribution rate.
  • Another feature of the invention is to obtain the distribution rate as a function of the number of passes.
  • Another feature of the invention is to obtain a rolling reduction for each pass in initial and terminating stages of the rolling operation from the cumulative distribution ratio of the thickness of parent material to that of the product.
  • Another feature of the invention is to obtain the cumulative distribution ratio as a function of the number of passes.
  • FIG. 1 is a diagrammatic representation of the rolling reductions in relation to the total rolling time
  • FIG. 2 is a diagrammatic representation of the thickness in relation to the temperature of material to be rolled with the number of passes being used as a parameter;
  • FIG. 3 is a systematic view showing one embodiment of the invention.
  • FIG. 4 is a chart showing the order in which the mean rolling reduction and the number of passes in which the desired total rolling reduction is achieved are calculated;
  • FIG. 5 is a diagrammatic representation of the relation between the cumulative load distribution ratio, the number of passes and the thickness, the cumulative load distribution ratio being used in a calculating method of a rolling reduction for each pass from the mean rolling reduction;
  • FIG. 6 is a diagrammatic representation of the relation between the distribution ratio and the number of passes, the distribution ratio being used in an other calculating method of a rolling reduction for each pass from the mean rolling reduction.
  • I is the length of rolled material at the exit side of the rolling mill for each pass, and v; is the mean rolling velocity.
  • the length I of the rolled material can be expressed by the following equation:
  • H is the thickness of the rolled material before rolling
  • 3 is the width of the rolled material before rolling
  • L is the length of the rolled material before rolling
  • h is the thickness of the rolled material after rolling in each pass
  • b,- is the width of the rolled material after rolling in each pass.
  • equation (5) can be further converted into the following equation (6):
  • the total rolling time T is a function of the mean rolling reduction Ah with the number n of passes being a parameter.
  • FIG. 1 shows the reduction between the mean rolling reduction and the total rolling time by combining conditional equation (8) with equation (7).
  • the smaller the number of passes the shorter is the total rolling time, and the smaller the mean rolling reduction Ah, the shorter is the total rolling time, provided that the number of passes remains unaltered. If it is desired to reduce the number of passes, one has only to increase the mean rolling reduction Ah.
  • the essential minimum condition for realizing the shortest rolling time is that the rolling reduction for each pass should be uniform and its value should be below the rolling reduction limiting value Ah max, and that the number of passes should be minimized.
  • the value of the minimum number of passes can be obtained by substituting into equation (10) the rolling reduction limiting value Ah max as a mean rolling reduction Ah. Since n must be an integer when it is obtained from equation (10), the value of n obtained may be made into in integer by counting the fraction as a whole number. 1f the value of n obtained in this way is used in equation (9), then it is possible to obtain the value of the mean rolling reduction Ah which corresponds to the A point in FIG. I.
  • a curve [I represents a rolling process in which the rolling reduction which is high in initial stages of operation is gradually lowered.
  • the use of this rolling process gives a small amount of heat retained in the rolled material when the final pass is reached, so that the temperature of the rolled product is low upon completion of the final passing.
  • Rolling reductions in terminating stages are an important factor in effecting contour control. Control of widthwise or edge-to-edge thickness of rolled material to produce uniform flatness is effected by controlling the bending of the rolls in passes in initial stages of operation. However, since the bending of the rolls may vary in proportion to the rolling load, rolling reductions are affected by this factor. For example, it is possible to produce uniform flatness or good contour if rolling reductions are such that the rolling load is about 700 tons. From this, it will be appreciated that contour control makes it necessary to reduce rolling reductions for passes in terminating stages of the operation.
  • the rolling reduction for each pass in intermediate stages should be greater in value than the mean rolling reduction Ah, it is important that it should not exceed the rolling reduction limiting value Ah max.
  • the mean rolling reduction Ah should be slightly smaller in value than the rolling reduction limiting value Ah max.
  • the number n of passes which would enable to obtain a minimum rolling time is obtained from equation (ID).
  • a value slightly smaller than the rolling reduction limiting value Ah max or qb. Ah max (0 qb 5 l) is substituted into the equation 10) to obtain the number n of passes. If the calculated value of the number n of passes has a fraction, the fraction should be counted as a whole number so that the value may be an integer. Then the value of the number n of passes obtained in this way is substituted into equation (9) to calculate the mean rolling reduction Ah. Thereafter a rolling reduction for each pass is calculated by correcting the mean rolling reduction Ah for each pass.
  • the correction of the rolling reduction for each pass is effected such that the rolling reductions for passes in initial and terminating stages should become smaller in value than the mean rolling reduction Ah-
  • the method for effecting correction is subsequently to be described.
  • the aforesaid coefficient rl) can be selected beforehand empirically or experimentarily.
  • FIG. 3 is a systematic view showing the embodiment.
  • l is a material to be rolled
  • 2 a reversible rolling mill
  • 3 a screw-down electric motor for positioning the rolling mill for effecting screw-down.
  • 4 is a radiation pyrometer for detecting the initial entrance side temperature of the material 1 to be rolled
  • 5 a thickness meter for detecting the initial entrance side thickness of the material 1.
  • 6 refers to a first arithmetic unit for calculating the total number n of passes and an average rolling reduction Ah which would enable the desired total rolling reduction to be achieved in a minimum interval of time.
  • 7 refers to a second arithmetic unit for calculating a rolling reduction Ah, for each pass by taking temperature control and contour control into consideration.
  • 8 refers to a third arithmetic unit for determining a screw-down position at which the rolling mill should be set based on the rolling reduction Ah,- for each pass calculated by the second arithmetic unit 7,
  • 9 designates a load cell which detects whether or not the material I is bitten by the rolls to time nicely the setting of the screw-down position of the rolls for each pass.
  • 10 designates a gate circuit which switches to the rolling mill an output of the third arithmetic unit 8 when signal from the load cell 9 indicates that the material I is not bitten by the rolls.
  • ll refers to a screw-down position setting means for setting the rolling mill at a screwdown position indicated by an output of the gate circuit l0.
  • the first arithmetic unit 6 is rendered operative to perform calculation when the material 1 to be rolled is withdrawn from a soaking pit (not shown) or the like and reaches the pyrometer 4 and thickness meter 5. From outputs of the pyrometer 4 and thickness meter 5, the first arithmetic unit 6 calculates the total number of passes and a mean rolling reduction adapted to achieve the desired total rolling reduction in a shortest interval of time, and the result of calculation is produced as an output. The process of calculation performed by the first arithmetic unit 6 will be described with reference to FIG. 4.
  • a temperature To and a thickness H, of the material 1 before rolling reductions are fed into the unit 6.
  • information .Q on the hardness of the material 1 to be rolled, eg the carbon content of the material, and a final thickness h, to be produced in the rolled product are fed into the unit 6 as set values.
  • a maximum limit rolling reduction Ah which may vary depending on the diameter R of the rolls of the rolling mill, the biting angle limit value 8,. and the types of steel is inputed as a set constant.
  • the maximum limit rolling reduction Ah may be obtained from the equation;
  • a rolling pressure P per unit area is calculated from the mean value h,,,, the initial temperature T the hardness Q, and the maximum limit rolling reduction Ah I by using a known deformation resistance equation and a known rolling load correcting term equation. More specifically, P is calculated as follows:
  • A The strain velocity (l/Sec).
  • k The deformation resistance.
  • a minimum value is selected from among the values of Ah, and AM obtained by equations (14) and (I5) and the value of set maximum limit rolling reduction Ah, and the minimum value thus selected is used as the rolling reduction limiting value Ah max which is multiplied by (0 5 S l) to obtain a limited rolling reduction Ah
  • a value 0.8 may be selected for dz.
  • the total number n of passes and the mean rolling reduction Ah are determined by the following formula which utilizes equations and Where the brackets 1 indicates that any fraction is counted as a whole number.
  • the outputs n and Ah of the first arithmetic unit 6 are inputed to the second arithmetic unit 7 where a rolling reduction Ah, for each pass is determined.
  • the method used for determining the value of rolling reduction Ah will be described with reference to FIG. 5 which shows the relation between the cumulative load distribution ratio q, the number of passes n, and the thickness h This functional relation has been determined empirically from the data obtained by practicing rolling operations, and can be expressed as, the following equations:
  • n is the total number of passes
  • i is a number of each pass
  • a, b and c are the coefficients.
  • the cumulative distribution ratio 6,- for each pass is obtained by equation (19), and the value of 6; obtained in this way is substituted into equation (22), so that the thickness h, to be produced in each pass can be calculated.
  • the rolling reduction Ah for the first pass can be obtained from the following equation:
  • the second arithmetic unit 7 calculates the thickness to be produced or rolling reduction to be achieved in each pass and transmits as its outputs the values obtained to the third arithmetic unit 8.
  • the third arithmetic unit 8 makes estimates of the temperature, deformation resistance and rolling load of the rolled material for each pass by using the rolling reduction Ah (or the thickness h.) and the temperature T and hardness Q of the rolled material inputed to the first arithmetic unit 6, and calculates according to the Hookes law the screw-down position S; for each pass at which the rolling mill should be set.
  • the screw-down position S is transmitted to the gate circuit 10 after completion of the (:'l )th passing.
  • the gate circuit 10 receives ON-OFF signals from the load cell 9 and transmits an output signal to the screwdown position setting means 1] indicating the screwdown position set value S, for the next following passing.
  • the screw-down position setting means 11 actuates the screw-down electric motor 3 in order to effect screw-down positioning by setting the roll pass of the rolling mill 2 at a desired degree of opening. Upon completion of positioning, the material I is fed to the rolling mill 2 to effect an ith passing through the roll pass.
  • FIG. 6 shows another method by which the rolling reduction Ah, for each pass is calculated by the second arithmetic unit 7.
  • the following relation is used:
  • equation (25) a is expressed in a cubic of the ratio of the pass number i to the total number n of passes, which can be solved empirically.
  • the coefficients d, e, fand g in equation (25) should satisfy the following conditions:
  • the distribution ratio a,- for each pass is calculated from equation (25 and the rolling reduction Ah,- for each pass is determined from equation (24).
  • the screw-down position is set by utilizing the rolling reduction h,- obtained in this way, and the screwdown position is set in the same manner as aforemen tioned to carry out rolling.
  • the rolling method provided by the present invention is suitable for effecting temperature control and contour control satisfactorily, because the values for rolling reductions are selected such that the value of rolling reduction for each pass in initial stages of the rolling operation is smaller than that of the mean rolling reduction, and the value of rolling reduction for each pass in terminating stages is also smaller. This enables to produce rolled products which are high in quality and stable.
  • the mean rolling reduction is obtained by using the smallest value of the maximum limit rolling reduction Ah, the load limited rolling reduction Ah,, and the torque limited rolling reduction Ahr.
  • the mean rolling reduction may be obtained by using one of the limited rolling reductions, or the mean value of the limited rolling reductions.
  • a rolling method for rolling mills comprising the steps of:
  • A11 a load limited rolling reduction (M1,) and a torque limited rolling reduction (AM) by a coefficient less than l
  • a rolling method as claimed in claim I wherein the ratio of the total rolling reduction to a value obtained by multiplying the mean value of a maximum limit rolling reduction (Ah a load limited rolling reduction (Ah,,) and a torque limited rolling reduction (Ahr) by a coefficient smaller than 1, is used as the number of passes by counting as a whole number the fraction of the value of the ratio obtained.
  • a rolling method as claimed in claim I wherein the rolling reduction for each pass in the initial and terminating stages is obtained by multiplying the mean rolling reduction by a distribution ratio.
  • a rolling method as claimed in claim I wherein the rolling reduction for each pass in the initial and terminating stages is obtained from the thickness of a parent material, the thickness of a product and a cumulative distribution ratio.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
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US568193A 1974-04-17 1975-04-15 Rolling method for rolling mills Expired - Lifetime US3927545A (en)

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3236877A1 (de) * 1981-10-05 1983-07-07 Kawasaki Steel Corp., Kobe, Hyogo Verfahren zum steuern des walzdurchsatzes beim warmwalzen
US4633692A (en) * 1984-08-17 1987-01-06 Mitsubishi Denki Kabushiki Kaisha Device for determining a setting value of a shape operating amount in a rolling mill
US4648256A (en) * 1984-05-09 1987-03-10 Mitsubishi Denki Kabushiki Kaisha Shape control apparatus for flat material
US4658614A (en) * 1984-05-09 1987-04-21 Mitsubishi Denki Kabushiki Kaisha Shape control apparatus for flat material
GB2193348A (en) * 1986-07-01 1988-02-03 Sendzimir Inc T Rolling mill management system
US5047964A (en) * 1984-12-18 1991-09-10 Aluminum Company Of America Material deformation processes
US5255548A (en) * 1992-03-02 1993-10-26 Mesta International Method for roller levelling of heavy plate

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5983280B2 (ja) * 2012-10-12 2016-08-31 Ｊｆｅスチール株式会社 圧延能率向上を目的とした熱間圧延方法

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3177346A (en) * 1959-11-06 1965-04-06 United Steel Companies Ltd Apparatus for use in controlling a rolling mill
US3253438A (en) * 1962-09-21 1966-05-31 Westinghouse Electric Corp Automatic strip gauge control for a rolling mill
US3600919A (en) * 1968-07-05 1971-08-24 Realisa Cybernetique Et Process for automatic control of the hot rolling of metal flats
US3688555A (en) * 1969-02-08 1972-09-05 Hitachi Ltd Method of and an apparatus for determining an optimum schedule of operation for reversible hot rolling mills

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3177346A (en) * 1959-11-06 1965-04-06 United Steel Companies Ltd Apparatus for use in controlling a rolling mill
US3253438A (en) * 1962-09-21 1966-05-31 Westinghouse Electric Corp Automatic strip gauge control for a rolling mill
US3600919A (en) * 1968-07-05 1971-08-24 Realisa Cybernetique Et Process for automatic control of the hot rolling of metal flats
US3688555A (en) * 1969-02-08 1972-09-05 Hitachi Ltd Method of and an apparatus for determining an optimum schedule of operation for reversible hot rolling mills

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3236877A1 (de) * 1981-10-05 1983-07-07 Kawasaki Steel Corp., Kobe, Hyogo Verfahren zum steuern des walzdurchsatzes beim warmwalzen
US4648256A (en) * 1984-05-09 1987-03-10 Mitsubishi Denki Kabushiki Kaisha Shape control apparatus for flat material
US4658614A (en) * 1984-05-09 1987-04-21 Mitsubishi Denki Kabushiki Kaisha Shape control apparatus for flat material
US4633692A (en) * 1984-08-17 1987-01-06 Mitsubishi Denki Kabushiki Kaisha Device for determining a setting value of a shape operating amount in a rolling mill
AU571076B2 (en) * 1984-08-17 1988-03-31 Mitsubishi Denki Kabushiki Kaisha Device for determining a setting value of a shape operating amount in a rolling mill
US5047964A (en) * 1984-12-18 1991-09-10 Aluminum Company Of America Material deformation processes
GB2193348A (en) * 1986-07-01 1988-02-03 Sendzimir Inc T Rolling mill management system
GB2193348B (en) * 1986-07-01 1990-07-11 Sendzimir Inc T Rolling mill management system
US5255548A (en) * 1992-03-02 1993-10-26 Mesta International Method for roller levelling of heavy plate

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JPS50134957A (enrdf_load_html_response) 1975-10-25

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