Abstract: A strip treatment line in which downstream of the processing roll stand for stainless steel strip, first and second tension rolls are provided to directly form a prestretching zone A for elastic or elastoplastic stretching of the strip following the dressing mill stand and for providing an afterstretching zone with elastoplastic or plastic stretching of the strip.

Abstract: The invention aims at a method of producing a metal strip on a continuous treatment line comprising a de-scaling station coupled with a cold rolling section. According to the invention, in order to adapt to a change in the production constraints, such as a spool change, the rolling speed is caused to vary on a very wide range down to less than 1 m/min and the cold rolling operation is done between working rolls the diameter of which is so small that, on said whole wide speed variation range, the rolling strength to be applied remains compatible with the product thickness adjustment possibilities, taking the characteristics thereof into account.

Abstract: A tandem strip-rolling line has a strip store between the mill so that when the upstream mill is open on the approach of a weld seam joining successive lengths, the downstream mill rolls strip stored in the strip store and conversely when the strip is halted upstream of the second mill, the strip is rolled in the first mill and fed to the strip store.

Abstract: Rolling stock is transported in a transporting device from a front roll stand to a rear roll stand. Between the roll stands, the rolling stock carries out an oscillation transverse to the transporting direction. At least one characteristic property, amplitude or frequency, of the oscillation is determined quantitatively and, from this determination, a tension or compression, existing in the rolling stock between the roll stands is determined. One of the roll stands is readjusted in such a manner, that a desired tension is built up in the rolling stock between the roll stands.

Abstract: Strip tension in metal strip subjected to a plastic deformation such as skin or dressing rolling, stretch bend leveling or stretching is adjusted by local variation of the temperature to establish a temperature profile which minimizes waviness and camber in metal strip.

Abstract: A roller leveller has an upper roller assembly 1 made of a plurality of taper rollers 7 each having a small diameter end with a collar 14 and a large diameter end, with the large diameter ends being set on a same side, and a lower assembly 2 made of a plurality of taper rollers 8 each having a small diameter end with a collar 15 and a large diameter end, with the large diameter ends being disposed on opposite sides of the large diameter ends of the taper rollers 7. The center axes of the upper and lower taper rollers 7 and 8 are inclined by a half-apex angle of the taper roller relative to a passing plane of a plate 50, and the upper and lower taper rollers are disposed in a zigzag way. A plate or coil plate 50 is passed between the upper and lower taper rollers to repetitively bend it and remove defective form.

Abstract: The present invention is to provide a tandem cold rolling method conducted by a tandem cold rolling mill, the number of rolling stands of which is not less than 4, wherein a rolling tension, the intensity of which is not lower than 30%, preferably not lower than 40% of the deformation resistance of material to be rolled, is given at least by the final rolling stand. The present invention is also to provide a tandem cold rolling mill satisfying the inequality of JC≧(0.375{overscore (h)}+0.275)JM, wherein the average thickness of a product sheet on the delivery side of the final rolling mill is {overscore (h)}, and an output of one coiler arranged on the delivery side of the tandem cold rolling mill, or a sum of an output of one coiler on the delivery side and an output of the bridle roller on the delivery side is JC, and an output of the main motor of the final rolling stand of the tandem cold rolling mill is JM.

Abstract: A high-speed rolling apparatus for bars includes a finishing mill and an associated first mill motor and a sizing mill and an associated second mill motor downstream of the finishing mill. The first mill motor power (Wf) and second mill motor power (Ws) satisfy the expression: Wf/Ws≧5. The apparatus provides simple and highly accurate control of the tension that is applied to the bars between the finishing mill and the sizing mill.

Abstract: A leveling technique that produces a high degree of flatness of strips and gives strips a characteristic such that parts cut from the strips by etching do not warp. Also, a method of leveling strips including the steps of rectifying a trip by tensioning and bending the strip with a tension leveler. The load acting on the strip by the tensioning and bending being 70% or more of the yield or proof stress of the strip. The method also including rectifying the strip by tensioning the strip with a roller leveler. The tension acting on the strip by the roller leveler being 50 N/mm2 or less.

Abstract: The invention relates to an installation for cold rolling strip-shaped rolling material, with a reversing stand disposed between two reel-up or unreeling coils or reels, and a second reversing stand in the rolling line of the first reversing stand, with both stands capable of being adjusted corresponding to consecutive passes for performing the rolling process, and to a method of cold rolling.

Abstract: A take-up equipment and a take-up method for a finish rolling mill for dividing a strip into a plurality of coiled products when taking up the strip on the exit side of the finish rolling mill are provided. A plurality of take-up machines (24, 26, K1, K2) are disposed at the downstream side of a hot finish rolling mill; a shearing machine (27, 2) is provided on the upstream side of a pinch roll (23, 4) of the take-up machines (24, K1) at the uppermost stream end; and a strip passing device (28, 6a) is provided between the shearing machine and the pinch roll at the uppermost stream to prevent a strip from rising. The strip passing devices are guiding devices for restricting the height of the rise of the strip or the airflow suction type strip passing devices for drawing in a strip under suction using airflow. The plurality of take-up machines are down coilers or carousel type reels having two winding drums (66a, 66b).

Abstract: A method of dynamic adjustment of the roll gap in a roll stand of a mill train having multiple stands for rolling a strip, with a strip stock, i.e., a loop, between two roll stands being adjusted or limited by a loop or a strip stock control, with the dynamics in adjustment of the roll gap being limited as a function of state variables of the mill train, in particular state variables of the loop or strip stock control.

Abstract: A system for controlling front and tail end gauge of a continuous hot rolled product in a rolling mill includes first and second individually driven roll stands arranged successively along said pass line in advance of a group of roll stands. A controller adjusts the operating speed relationship between the first and second individually driven roll stands to achieve an increased level of tension in the front and tail end segments of the product passing between the first and second individually driven roll stands. The increased level of tension results in the decrease in product cross sectional area sufficient to compensate for the lack of cross sectional area reduction resulting from the absence of interstand tension experienced by said front and tail end segments while being rolled in the group of roll stands.

Abstract: An apparatus for stretch leveling thin metal strips, in particular aluminum strips between 0.1 and 0.5 mm thick, has a group of braking rollers that are interconnected via differential transmissions and controlled jointly with respect to speed to form a first leveling path with a downstream central speed-controlled leveling roller and that downstream a group of pulling rollers connected together by means of differential transmissions and controlled jointly with respect to speed form a second leveling path with the central leveling roller.

Abstract: A method of controlling a continuous skin-pass and reduction operation for a metal strip includes the steps of passing a strip through a gap between working rollers of at least two successive rolling stands, only an upstream one of the stands providing substantial thickness reduction of the strip; determining an extension rate of the strip provided by the upstream stand; determining a tension of the strip downstream of the upstream stand; adjusting the speed of the working rollers of the upstream stand compared to the speed of the working rollers of a downstream one of said stands according to the determination of the extension rate; and adjusting the squeezing force of the upstream stand according to the downstream tension determination. A response time to the step of adjustment of the squeezing force is longer than a response time to the step of adjusting the speed of the working rollers.

Abstract: A method of rolling out the ends of a coiled strip in a reversing rolling mill having reels disposed on both sides thereof minimizes a length of strip at the strip ends having a non-conforming thickness. A start of the strip is introduced into the roll gap without inlet side strip tension and without rolling force at the start of each reduction pass. The rolling force is then gradually increased. The inlet side strip tension is subsequently reduced substantially to zero at the end of each reduction pass while the strip end still connected to the uncoiling reel, such that the strip end passes tension-free completely through the rolling gap and is consequently reduced in thickness. An apparatus for carrying out the method on a reversing mill includes a control system which selectively controls, via regulating and adjusting devices, the inlet and outlet strip tensions and the rolling force in a manner dependent upon respective locations of the start and end of the strip.

Abstract: The present invention is an apparatus and method for reducing the total number of required rolling passes of a metal strip in a cold rolling mill to achieve a desired strip thickness. This is accomplished by increasing the exit strip tension of the metal up to 85% of the yield strength Y of the metal strip. This increase in exit strip tension allows a manufacturer to process strip in an apparatus at a maximum thickness reduction of about 50 to 55% in a single rolling pass. At the same time, the increased exit strip tension will result in a reduced lever arm of the work roll of the cold rolling mill and will substantially reduce all of the roll separating force, motor torque and roll mill power of the apparatus.

Abstract: A reversing rolling mill for rolling metal strip includes an entry side coiler and an exit side coiler and at least one mill rolling stand including a central roll, an entry side outer roll and an exit side outer roll having their respective longitudinal axes disposed in a first, horizontal, plane and parallel to a longitudinal axis of the central roll, a top outer roll in contact with the central roll, and a bottom outer roll, longitudinal axes of the top outer roll and bottom outer roll being disposed in a second, vertical, plane passing through the longitudinal axis of the central roll and parallel thereto, motors to drive the rolls and rotate the rolls about their respective longitudinal axes, devices to vertically move the central roll and the top outer roll, and devices to move the side outer rolls horizontally and to move the bottom outer roll vertically into and out of rolling contact with the central roll in a lowered position of the central roll.

Abstract: A bending machine for closing channels which simultaneously bends both side walls of a "U" shaped metal channel, comprising: a support frame; a lower male member slide mounted on the support frame, having a normally closed two-halves male member, each half having a notch in lateral wall thereof, and is associated with driving means for opening the halves of the male member when receiving a channel and for releasing the channel once its side walls thereof have been bent inside each notch, allowing to remove it therefrom; and two lateral bending inserts each slide mounted on the support frame, and associated with driving means, for bending both side walls of the channel into the notches. If desired an upper member, mounted on lowering and lifting means, is provided, having a blank holder to retain a channel on the lower male member when it is closed and/or a die member for simultaneously bend a plate forming a channel, and then close both side walls thereof forming a closed channel.

Abstract: The present invention is to tension and guide hot strip for coiling in a hot strip mill, the hot strip mill includes a runout table with driven rollers for delivering hot strip from a train of finishing mill stands along a pass line of a runout table to a coiler. The coiler having driven mandrel for coiling strip thereon and pinch rolls having an operative position to direct the leading end of strip from the runout table to the coiler and tension the deflected leading end portion of strip during the formation of initial convolutions of coiled strip on the driven mandrel. Gag roll assembly upstream of the pinch rolls at the runout table for tensioning strip conveyed by the runout table after a trailing strip end emerges from the train of finishing mill stands.

Abstract: There is provided a refuging system for transfer bars of a transfer feeder of a transfer press, in which the transfer bars are driven by a transfer bar driving mechanism including an induction type servo motor. The refuging system includes a servo control for controlling the induction type servo motor, a detector for detecting an occurrence of an abnormal condition of the servo control and urgently stopping operations of a slide of a press body of the transfer press and the induction type servo motor, a detector for detecting a crank angle of the press body and discriminating an area in which the slide or a mold of the press body interfere with the transfer bar of the transfer feeder or an attachment therefor attached to the transfer bar, and a driver for driving the transfer bar to a position at which the slide and the mold of the press body do not interfere with the transfer bar of the transfer feeder and the attachment by applying an A.C.

Abstract: Flattening group (18) for levelling machine with operative rollers (60-65, 70-74) of increasing diameter.

Abstract: The stretch leveling or stretch-bend leveling of aluminum or stainless steel strip of a thickness of 0.1 to 0.5 mm is carried out following a measurement of strip nonplanarity or strip profile by regulating the stretch in the stretch leveler or the contour of a roller thereof or both and/or by regulating the depth of penetration or degree of bending by the stretch-bend rollers. The tension in the strip just before coiling is varied in response to measurement of the thickness of the strip across the width, thereby optimizing the leveling and surface qualities of the strip.

Abstract: The stretch leveling or stretch-bend leveling of aluminum or stainless steel strip of a thickness of 0.1 to 0.5 mm is carried out following a measurement of strip nonplanarity or strip profile by regulating the stretch in the stretch leveler or the contour of a roller thereof or both and/or by regulating the depth of penetration or degree of bending by the stretch-bend rollers. The tension in the strip just before coiling is varied in response to measurement of the thickness of the strip across the width, thereby optimizing the leveling and surface qualities of the strip.

Abstract: A system and method for achieving an optimum interstand strip tension providing substantially equal loading of adjacent stands of a tandem rolling mill where such optimum tension is determined by the expression ##EQU1## where A1 and B1 are, respectively, the load ratio intercept and the slope of the load ratio versus interstand tension function for a first mill rolling stand, and A2 and B2 are, respectively, the load ratio intercept and the slope of the load ratio versus interstand tension function for an adjacent second mill rolling stand, and whereby the rolling capacity of the mill is substantially fully utilized.

Abstract: A process for operation of a two-stand reversing mill optimizes product yield and time productivity in rolling strip in two or more passes through the mill, by bringing, in each pass, a tail end of the rolled strip to but not into the first roll stand through which the remainder of the strip has last been passed, gripping said tail end on a reel serving as an exit reel, rolling the strip and coiling it onto said exit reel. In a next to last pass after the first pass, a portion, e.g. about 1 1/2 wraps, of the strip may be left on a reel serving as an entry reel to maintain strip tension.

Abstract: A method of controlling and maintaining a drawing force applied to a length of rolled stock between two-spaced apart rolling units includes the steps of determining the value of at least one of a frequency and an amplitude of a transversed vibration of the rolled stock between the drawing units, correlation of the determined value to a corresponding value of drawing force, comparison of the correlated value of the drawing force to a reference value, and adjustment of the drawing force to maintain it at a substantially constant selected value. In another aspect of the invention an apparatus is provided which includes elements for measuring at least one of a frequency and an amplitude of a traversed vibration experienced by a length of rolled stock between two drawing units, a unit for correlating the measured value to a corresponding value of applied drawing force, and a control unit for adjusting the applied drawing force as necessary to maintain it substantially at a selected constant value.

Abstract: The present invention relates to a process and to a device for the rolling of bands (B) with uneven thickness and/or length distribution over their width by using at least one control roller (5, 9, 21, 27, 41, 43) located on the inlet and/or outlet side of a mill (W, W', W") and capable of swiveling in its position relative to the band (B), making it possible in case of minor disturbances, independently of the existing operating conditions, to compensate for the running of a band caused by unevenness in the thickness and/or length distribution over the width of the band. This is achieved according to the invention in that the distribution of the tensile stress over the width of the band (B) is detected with at least one measuring device (7, 11, 25) and in that the control roller (5, 9, 21, 27, 41, 43) is adjusted in function of the detected distribution of tensile stress until the detected distribution of tensile stress is equal to a desired value.

Abstract: A method and an apparatus for an anticipatory thickness control in foil rolling by using characteristic lines stored in a process control computer of the individual manipulated variables (for example, strip tensions, rolling speeds) for various operating points (conditions of operation) or by using an on-line operating physical computing model, also in combination with a monitor control. The method includes the steps of determining the thickness deviations of the foil at the entry side of the roll stand and of compensating the thickness deviations by an anticipatory thickness control. The apparatus includes a thickness measuring device between the running-off reel and the rolling mill or the roll gap of the roll stand. The thickness measuring device is connected to a superordinated process control computer. Following the thickness measuring device is arranged a tensioning unit which serves to change the travel path of the foil strip between the running-off reel and the roll gap.

Abstract: A bowing correction apparatus for a temper rolling mill corrects vertical bowing of a cold-rolled steel sheet. The bowing correction apparatus includes at least a first bowing correction auxiliary roll, first deflector roll, second deflector roll and second bowing correction auxiliary roll. These rolls are arranged in the running direction of the cold-rolled steel sheet and are alternately positioned on upper and lower sides of the cold-rolled steel sheet to correct bowing of the sheet.

Abstract: A looper control system has a looper that is interposed between two rolling stands of a tandem rolling mill and is actuated by a hydraulic actuator; and a control calculating section for calculating a speed change rate command value of a primary rolling machine and a pressure command value of a hydraulic looper actuator so that an interstand tension and a looper height can be both controlled at target tension and looper height values, respectively, on the basis of a detected looper height value and a previously determined control gain. A resonance frequency changing section detects hydraulic flow rate of the hydraulic actuator and multiplies it by a gain to obtain a first speed change rate command value; and a damping constant changing section detects pressure in the hydraulic actuator and multiplies it by another gain to obtain a second speed change rate command value.

Abstract: The stretch leveling or stretch-bend leveling of aluminum or stainless steel strip of a thickness of 0.1 to 0.5 mm is carried out following a measurement of strip nonplanarity or strip profile by regulating the stretch in the stretch leveler or the contour of a roller thereof or both and/or by regulating the depth of penetration or degree of bending by the stretch-bend rollers. The tension in the strip just before coiling is varied in response to measurement of the thickness of the strip across the width, thereby optimizing the leveling and surface qualities of the strip.

Abstract: A control device for the purpose of achieving highly precise rolled material. The response and robust stability of the rolled material tension and looper height are specified, and a controller is designed so that the rolling mill main motor and looper operate in concert to suppress variations in rolled material tension, thereby achieving stable optimum control which is responsive to the rolling state and rolling conditions.

Abstract: A feed control system for a metal forming machine. The feed control system includes a feed assembly mounted on the metal forming machine. The feed assembly includes a slide assembly and a rotating ball-screw operatively connected to the slide assembly. The slide assembly is linearly movable in response to rotation of the ball-screw which is driven by a servo-motor. A control system is operatively connected to the feed assembly for automatically cycling the feed assembly in synchronization with the press so as to feed the metal stock into the press.

Abstract: Downstream of an uncoiler, a stretch-bend leveler is provided in a strip line to correct curvature in the strip plane. One or more rollers of the stretch-bend leveler are swingable about a horizontal or vertical axis at the end of the roller in response to a measurement of the longitudinal edge arcs of the strip to effect correction.

Abstract: A process for planishing under traction a thin metal strip in an installation including a planisher comprising at least one bending unit with two planishing sets and a multi-roller leveling assembly comprising two rows of rollers. The imbrication of the planishing sets and the multi-roller leveling assembly and two tension blocks, respectively, are adjusted upside and downside to obtain a prescribed elongation of the strip. Flatness faults in the planisher are corrected by adjusting the through-speeds and imbrication of the planishing sets, such that the prescribed elongation for planishing is substantially attained by the time the strip leaves the planisher.

Abstract: An interstand tension controller for a continuous rolling mill having a plurality of rolling stands and provided with a looper between the adjacent rolling stands controls two controlled variables, i.e., the interstand tension of the workpiece and the looping angle of the looper, to adjust the measured interstand tension and the measured looping angle to desired values, has control loops that control the rotating speed of the rolls of the rolling stand and the looping torque or the looping speed of the looper to regulate the interstand tension and the looping angle, estimates disturbances acting on the control loops, the variation of the characteristics of the controlled system and the interference between the control loops, and operates manipulated variables to offset the disturbances.

Abstract: Tension bridles for a cold rolling reducing mill are provided. The reducing mill reduces the thickness of a metal strip passing through the reducing mill. The tension bridles create tension on the metal strip between the bridle and the first reducing stand to receive the metal strip and between the final reducing stand and the exit bridle so that a greater reduction can be made in the thickness of the metal strip in the first reducing stand and in the final reducing stand than is ordinarily possible. When the reducing mill is a reversible mill, a tension bridle positioned at each end of the mill enhances the reducing qualities of the mill and also enhances the quality of the metal strip being coiled after it passes through the mill.

Abstract: Method and apparatus for producing large-area metal, especially steel, plates. The metal strip unwound from a coil is continuously treated by a heat treatment followed by stretch-bend leveling and then stretcher-leveling, the latter being discontinuously carried out by clamping the strip at two locations and urging those locations apart. Only subsequently is the strip cut to form the plates.

Abstract: A can body making apparatus has an encoder that generates a signal representative of the angular position of the crankshaft. The signal is input to a controller that controller an feeding mechanism in phased timed relationship to the rotation of the crankshaft allowing greater control of the feeding mechanism.

Abstract: The cross bowing in metal strip, especially thin metal strip of a thickness less than 2 mm, is removed by providing downstream of the high tensioned section of the strip at which stretch leveling or stretch bend leveling is effected at least one correcting roller which has an adjustable depth of penetration into the path of the strip at a low tension section, the depth of penetration being controlled by measuring the cross bowing also in the low tension section.

Abstract: A film of lithium capable for example of providing the anode of a polymer electrolyte battery is produced by laminating a lithium sheet between two working rolls. At the outlet, the film remains attached to one of the two rolls up to a given point of the circumference of the latter where it forms an angle of about 90.degree. with the meeting point between the two rollers. A sufficient tension is thereafter exerted on the film, which in any case is inferior to the limit of elasticity of lithium, by pulling the film in order to detach it from the surface of the roller and usually so that the given point moves into an intermediate position between 90.degree. and the meeting point, for example about 45.degree.. The product obtained may also be used any time there is a need for a film of lithium having a thickness for example between 10 and 100 .mu.m.

Abstract: A setting means sets variables for expressing the process model, a target thickness value of the rolled material, a target interstand tension value of the rolled material, variables for responses of the thickness and the interstand tension and variables for adjusting the responses of a control system for controlling the thickness and the interstand tension. A control gain arithmetic means obtains control gains as numeric values by substituting the set variables into predetermined control gain operation expressions. A control arithmetic means calculates the speed command values and the roll gap command values for causing the thickness to follow up the target thickness and the interstand tension to follow up the target interstand tension while reducing an interaction between the thickness and the interstand tension by use of the calculated control gains.

Abstract: Continuous rolling is conducted by interposing loopers respectively between a plurality of successive stands and connecting a rear end of a preceding bar to a top end of a next bar. Roll gaps of the respective stands are each controlled by thickness control units. Interstand mass flow variations are each controlled by mass flow control units. Looper heights are controlled by looper height control units. Further, interstand tensions are controlled by looper tension control units. If no looper is provided, the interstand tensions are controlled by looperless control units. A flying thickness change control unit tracks a connecting point. The flying thickness change control unit switches over looper tension control and looperless control and changes a reference tension and a reference looper angle so that tensile and flexural forces are not applied to this connecting point.

Abstract: A method of longitudinal rolling of seamless pipes in a continuous rolling procedure on an internal tool in a multiple-stand rolling train, wherein the rolls of successive rolling stands are mounted off set relative to each other. In accordance with the present invention, in a first of only two successive rolling passes, a roll thickness reduction is produced with opened roll groove sides in the roll groove bottom which reduction corresponds to or is slightly greater than the roll thickness of the finished pipe. In the second rolling pass, the side portion of the first rolling pass is reduced in the direction of the width to the wall thickness of the finished pipe in the roll groove bottom of the second rolling pass.

Abstract: The bridle or bridles of a stretching or levelling line for a thin metal strip, e.g. of a thickness of up to 1 mm, can have at least one roll of a periphery variable between an outwardly convex and an inwardly concave bulge to compensate for dishing of the strip or edge waviness.

Abstract: A leveling device for correcting defective shape of a strip by repeatedly bending the strip under a tensioned condition of the strip, comprising a tension leveler including a stretching roll unit for correcting local elongations of the strip and a C-warp correcting roll unit for correcting the warp in the crosswise direction of the strip, and at least a tension fluctuation suppressing means for suppressing the tension fluctuation transferred from the bridle rolls and preventing the generation of charter mark. The tension fluctuation suppressing means may be composed of a rotary resistant body of at least two deflector rolls or of a pair of pinch rolls arranged one above the other.

Abstract: The invention is directed to provide a rolling method which enables an enlarged range of reduction ratio in sizing-rolling in the common drive system. The invention provides that when tension applied to rolled material between the upstream and downstream-placed mills is made higher than a value that tension/average resistance to deformation of rolled material is 0.2, the upstream-placed mill is caused to perform force rolling, and when compressive force of the rolled material is made higher than a value that compressive force/average resistance to deformation of rolled material is 0.1, the downstream-placed mill together with the upstream-placed mill are caused to perform tensile rolling in the common drive system. The rolling methods provides a stable rolling in a larger sizing range without decrease of diameter or buckling of rolled material.

Abstract: A method and an arrangement for the treatment of metal strip, particularly for the treatment of hot-rolled metal strip in an entry portion of a pickling line through which the metal strip travels continuously. The method includes straightening the metal strip which is being uncoiled from an uncoiling reel under a predetermined strip tension, then severing the unstraightened ends of the strip for producing straightened ends of the strips, and subsequently connecting the strip end of an advancing metal strip to a strip end of a subsequent metal strip. Immediately after being uncoiled, the metal strip is straightened by stretch-bending and a strip tension is produced which is sufficiently high for straightening by stretch-bending without increasing the uncoiling tension.

Abstract: The invention relates to a process for levelling continuously moving metal strips exclusively by tensile rolling levelling. The strip to be levelled is subjected to two successive tensile rolling operations in the direction in which it moves. In the first tensile rolling operation the tensile rolling levelling is performed with relatively low tensile stressing and considerable rolling deformation, while over the second tensile rolling distance the strip is subjected to only slight bending with substantially higher tensile stressing. The result of these successive different kinds of stretching-and-rolling levelling is a flat strip which maintains its flatness even after a prolonged storage period.