Bending and straightening of metal. Straightening of strip and sheet material Straightening of metal using the mallet rule
The original rolled metal, both sheet and bulk, does not always have flatness characteristics sufficient for high-quality performance of subsequent deformation operations. In such cases, metal straightening is used as a preliminary operation. A related term, metal straightening, is a type of this operation that results in the alignment of only the axis of the rod.
State standards are specified the following types tolerances of finished rolled products:
- For round and square bars cross section- spatial curvature and apparent curl
- For rods square section, in addition - concavity and convexity of the edges;
- For steel strips - non-flatness, crescent shape, convexity of the side edges.
- For sheets - non-flatness.
- For tapes and rolls - telescopicity and edge curvature.
In the case of high-precision stamping, all of the above defects provoke accelerated wear of the dies, and the accuracy finished products decreases. The cause of such distortions can also be separation operations on sheet and grade shears, when the edges of the sheet/strip or the ends of the rods are unacceptably bent.
Even more prerequisites for straightening during hot stamping. Finished forgings are bent when:
- Pushing the die strand out of the cavity (this happens especially often with forgings of complex shape);
- Heat treatment, after which internal residual stresses arise in the metal;
- Trimming of flash due to uncontrolled shrinkage of metal.
In cold stamping technologies, metal straightening is performed after bending parts made of high-carbon or spring steels, as well as during cold extrusion of products with a long core part. It is also quite common to straighten and straighten metal in the form of a roll before dissolving it into strips.
The basis for including such an operation in technological process production are based on the results of measurements of the shape of parts, for which either special templates or a universal measuring tool are used. For minor deviations, manual straightening of the metal is sometimes acceptable, but in most cases this is not enough.
Types of metal straightening
The operation in question can be performed in a cold or hot state. In the hot state, forgings are adjusted that have already gone through all the deformation transitions, including trimming the flash. In this case, a separate operation is not provided, but deformation is carried out in the final groove of the cutting press die (although in justified cases, hot straightening of the metal can also be performed on the main stamping equipment). The advantages of such processing are considered to be lower energy consumption, as well as a beneficial effect on the structure and performance properties of the forging material.
Cold straightening in hot stamping is used after the stamped products have undergone heat treatment. The tool for performing such an operation is very simple, and the configuration of the working cavity fully corresponds to the dimensions of the forging, which are shown in its drawing. The operation is often performed simultaneously in two planes, which improves quality finished product.
In sheet stamping, editing is performed:
- After cutting and punching thick sheet metal, when cutting the metal fibers of the workpiece leads to the occurrence of internal stresses;
- After free bending (especially without clamping), to remove defects in the shape of the workpiece that arose due to springing;
- When stamping directly, when the curvature of the metal workpiece occurs due to intense friction of the product on the matrix;
- After multi-transition drawing of parts with flanges.
In cold sheet stamping, compression is distinguished by smooth, point and wafer dies. In the first case, a flat surface calibration is carried out, therefore this method effective for thin-sheet workpieces made of metals of high ductility. Specific forces do not exceed 100 MPa, and there are no tool marks on the surface of the finished product.
For workpieces with greater thickness, as well as from metals of increased hardness, it is necessary to perform spot/wafer straightening. Small notches in the form of teeth are made on the working tool, and their points on the punch and matrix should not coincide. The specific forces are higher - up to 250...300 MPa, but as a result, all surface defects are corrected.
Sometimes flat straightening is done before rolling. The original sheet or strip of metal is rolled through several regular rollers (their number should always be unpaired, and the number of upper, pressure rollers is always one more than the lower, support rollers).
Straightening equipment
If these transitions are combined with the main deformation operations (as is often the case with hot stamping), then no special equipment is required. Cold straightening of metal rods or strips is performed on. They are horizontal machines that operate on the principle of rotational stamping.
The difference is that the pressures created by the working rollers should not exceed the plasticity limit of the straightened material. Such machines operate automatically, and therefore differ high performance. Rods are straightened in the same way, only the profile of the working rollers in this case is not flat, but corresponds to the cross-section of the source material.
You can also straighten voluminous workpieces using presses. If the specific force does not exceed 300 MPa, then screw presses with an arc drive of the F17__ series are used. The effect is achieved due to the high speed of collision of a flat die (attached to a slide) with the product that requires straightening. Since the pressure distribution over the entire surface is the same, several identical overall dimensions details. This reduces the labor intensity of the operation.
The most difficult and responsible is the straightening of parts after cold extrusion. Since the strain hardening of the material is very high, the specific forces can reach the plasticity limit, i.e. 600...800 MPa and even more. Impact nature of the load created screw press, does not provide the proper quality of editing due to the inertia of the material. Therefore, special presses of the K82__ and K83__ series with a crank-knee working mechanism are used. The peculiarity of the design of such a press is the ability to ensure that the part is held (up to 2...3 s) under pressure with the equipment slide in the lowest position. As a result, internal stresses are overcome and the part is leveled.
The presence of curvature in parts is checked by eye, or the part to be straightened is placed on a plate and the gap between the plate and the part determines whether there is curvature.
When editing, you need to choose the right places to strike. The blows should be accurate, commensurate with the amount of curvature, and gradually decrease as you move from the greatest bend to the smallest. The work is considered complete when all the irregularities disappear and the part appears straight, which can be checked by applying a ruler. The straightened part or workpiece must be positioned correctly on the plate.
You should work with gloves. Edit. strip metal It is carried out in the following order: the detected bend is marked with chalk, after which the curved part is taken by the end with the left hand and placed on a plate or anvil with the curved part up. IN right hand
take a hammer and strike the convex places on the wide side, making strong blows on the largest convexity and reducing them depending on the magnitude of the curvature; the greater the curvature and thickness of the strip, the stronger the blows need to be applied, and vice versa, as the strip straightens, weaken them, finishing the editing with light blows.
The force of the blows should be reduced as the size of the spots decreases.
When straightening the strip, as necessary, you need to turn it from one side to the other, and after finishing editing the wide side, start straightening the edge. To do this, you need to turn the strip on its edge and apply strong blows at first, and as the curvature is eliminated, weaker and weaker in the direction from the concave to the convex outline. After each blow, the strip should be rotated from one edge to another. The elimination of irregularities is checked by eye, or more precisely, on a marking plate along the clearance or by applying a ruler to the strip. The straightened material may have defects mainly due to incorrect
location determination
, on which it is necessary to strike, an uneven decrease in the force of the blow; lack of proper accuracy when striking; leaving nicks and dents. This is a more complex operation. The bulges formed on the workpieces are most often scattered over the entire surface of the sheet or are located in the middle, therefore, when editing workpieces with bulges, you should not hit the convex sheet with a hammer, since this will not only not reduce them, but, on the contrary, will stretch them out even more (Fig. 93, b).
Before you start straightening workpieces with bulges, you need to check and determine where the metal is stretched the most. Outline convex places in the form of bulges with a pencil or chalk. After this, place the workpiece so that its edges lie on the entire surface and do not hang down. Then, supporting the sheet with the left hand, a series of hammer blows are applied with the right hand from the edge of the sheet towards the convexity.
As you approach the bulge, the blows should be applied weaker, but more often.
Straightening of thin sheets is done with wooden mallets, and very thin sheets are placed on flat slab and smooth with ironing irons.
Straightening of bar material. Short rods are straightened correct slabs, striking with a hammer on convex places and curvatures. Having eliminated the bulges, they achieve straightness by applying light blows along the entire length of the rod and turning it with the left hand. Straightness is checked by eye or by the gap between the plate and the rod.
Highly springy and very thick workpieces are straightened on two prisms, striking through a soft spacer to avoid scoring on the workpiece. If the force developed by the hammer is not enough to perform straightening, then use manual or mechanical presses. In this case, the workpiece is placed on the prisms with the convex part up and pressure is applied to the curved part.
Editing (straightening) of hardened parts. After hardening steel parts sometimes they warp.
Straightening of hardened parts is called straightening. Straightening accuracy can be achieved in the range from 0.01 to 0.05 mm.
Depending on the nature of straightening, different hammers are used: when straightening precision parts on which traces of hammer blows are not acceptable, soft hammers (made of copper, lead) are used. If, when straightening, you have to pull out or lengthen the metal, use steel hammers weighing from 200 to 600 g with a hardened striker or special straightening hammers with sharp strikers.
Thin products (thinner than 5 mm) are always calcined through, so they need to be straightened not in convex places, but, on the contrary, in concave places. The fibers of the concave part of the part are stretched and lengthened by hammer blows, and the fibers of the convex part are compressed and the part is extruded.
In Fig. 94 shown straightening the square. If the square has sharp corner, then it needs to be straightened at the top internal corner, if it is an obtuse angle, then at the vertex of the outer corner. Thanks to this straightening, the edges of the square will stretch and it will take correct form with an angle of 90°.
Rice. 94. Techniques for straightening (straightening) hardened parts of squares
In the case of warping of a product along a plane and a narrow edge, straightening is performed separately: first along the plane, and then along the edges.
The difficulty of straightening sheet metal depends on what type of defect the sheet has - a waviness on the edge, or a bulge, or a dent in the middle of the sheet, or both (Fig. 15).
Rice. 15. Techniques for straightening sheet metal: a – with a deformed middle of the sheet; b – with deformed edges of the sheet; c – using a wooden trowel; d – using a metal smoother.
When straightening a convexity, blows must be applied starting from the edge of the sheet towards the convexity (Fig. 15 a, b).
The most common mistake is that the strongest blows are applied to the place where the convexity is greatest, and as a result small dents appear on the convex area, which further complicates uneven surface. In addition, the metal in such cases experiences very strong tensile deformation. You need to do just the opposite: the blows should become weaker, but more frequent, as the edit approaches the center of the convexity. The sheet of metal must be constantly rotated horizontal plane so that the impacts are evenly distributed over its entire surface.
If the sheet has more than one convex section, but several, you must first reduce all the convex areas into one. To do this, strikes with a hammer in the intervals between them. The metal between the protrusions is stretched, and they combine into one. Then you need to continue editing in the usual way. If the middle of the sheet is smooth, and the edges are distorted by waves, then the sequence of blows when editing should be the opposite: they should be applied starting from the middle, moving towards the curved edges (Fig. 15, b). When the metal in the middle of the sheet stretches, the waves on its edges will disappear.
Very thin sheets cannot be straightened even with hammers made of soft material: Not only will they leave dents, but they can also tear thin metal.
In this case, smoothing bars made of metal or wood are used for straightening, with which the sheet is smoothed on both sides, turning it periodically. The quality of editing can be checked using a metal ruler.
Anyone who has taken on the task of straightening a steel sheet knows that this work is quite difficult: while you straighten one bend, others appear on the sheet. However, this can be avoided and thus make the work much easier. The steel sheet must be laid for straightening not on a smooth plate, as is usually done, but on a backing plate with many small blunt tubercles evenly spaced on its surface. In this case, the quality of work should increase, and labor intensity should decrease. Metal under attack rubber mallet It will be as if he himself is looking for his place. At the same time, barely noticeable waves are formed on the sheet; when puttying and painting, they will begin to fill in and help ensure that the putty and paint adhere very firmly to the metal. Irregularities after metal coating are completely invisible. The only difficulty is how to make the required backing plate. It is really difficult to make it at home: the tubercles are usually obtained by cutting on a smooth slab big number mutually intersecting and located close to one another grooves. This can be done on a planing or milling machine, therefore, if there is such an opportunity, it is better to take advantage of it.
Straightening (straightening) is a metalworking operation in which deformed, warped metal workpieces or parts are given the correct flat shape. Editing is applied after cutting sheet material scissors, chopping with a chisel and other operations. Straightening is also used to straighten strip and rod material, pipes and wire. Cast iron parts are not straightened, since cast iron is too brittle and can crack during straightening.
In metalworking and especially in toolmaking, correction of bent and warped products with great accuracy (up to tenths of a millimeter), after mechanical or heat treatment, is often called straightening the product.
Editing can be done manually or by machine.
Pipes are bent manually or by machine, with or without filler, in a cold or hot state. The choice of method depends on the pipe diameter, wall thickness, material and bend angle (Fig. 8).
Pipes with a diameter of more than 100 mm are bent in a hot state with filler (fine dry sand). The ends of the pipes are closed with plugs and holes are drilled into them to release gases. Heating is carried out with a gas burner or blowtorch. Pipes with a diameter of up to 15 mm are bent using pins inserted into the holes of a steel plate, which is clamped in a vice. For thicker pipes, pipe benders mounted on a special workbench are used. The pipe is inserted between two rollers against the stop. Bend the pipe by turning the lever with rollers with your hands
Rice. 8 Pipe bending: 1 - pipe, 2 - stop, 3 - template, 4 - movable bracket, 5 - roller, 6 - support, 7 - lever
Copper and brass pipes are cold bent with filler (molten rosin, stearin, paladin, lead). The pipe is annealed before bending. Copper is heated to 600-700 °C and cooled in water; bronze - up to 600-700 °C, in air; duralumin - up to 350-400 °C, in air.
When heated copper pipes bend, filling with sand. Properly bent pipes do not have wrinkles or dents.
Calculation of workpiece lengths
When bending parts at right angles without rounding on the inside, the bend allowance is taken from 0.5 to 0.8 of the thickness of the material. Folding length internal sides square or bracket, we obtain the length of the development of the workpiece.
In Fig. 4 a, b shown respectively are a square and a staple with right internal angles.
Square size: A= 30 mm; b =70mm G= 6mm. Workpiece development length l= a + b+ 0.5t 30+ 4+ 70 + 3 = 103 mm.
Bracket dimensions: A= 70 mm b = 80 mm; With= 60 mm; t = 4 mm. Workpiece development length
l= a + b+ s + 0.5t = 70+80+60+2=212 mm.
a, b - square and staples with right internal angles
A b
When manually straightening sheet blanks and parts, steel or cast iron leveling plates or anvils, steel hammers weighing 400 - 600 g, copper, lead, brass, wooden, bakelite hammers, etc. are used.
Machine leveling is carried out on manual and driven three-rollers, on driven pneumatic hammers and on presses. This manual covers only manual editing used in training workshops.
Straightening is carried out by striking with steel hammers or hammers made of soft material in certain places, proportioning the force of the blows to the size of the convexity and the thickness of the straightened product. The surface of the leveling plate, as well as the hammer heads, must be even, smooth and well ground. When manually straightening, it is more convenient to use hammers with. round, and not with a square striker, since incorrect blows or distortions of a hammer with a square striker may leave notches or even holes on the surface of the sheet. The hammer head should lie flat on the sheet, without distortion. The hammer should be held by the end of the handle and only the hand should be used to strike.
Techniques for editing sheet material are as follows. Having laid the deformed sheet on the slab with the bulges up, if possible, trace the bulges with a graphite pencil or chalk. After this, frequent but not strong blows are applied along the straight edges of the sheet towards the convexity. The material, under the influence of blows, will be stretched, releasing the tightened middle and gradually leveling out the bulge. As you approach the bulge, the blows should be applied weaker, but more often.
After each blow, you need to check what effect it has on the sheet. It should be remembered that incorrect blows can render the sheet unusable. Under no circumstances should you hit the bulges directly, as the bulges will increase rather than decrease.
Thus, the essence of the process of straightening sheet parts is the gradual stretching of straight sections of the sheet due to some thinning of the material in these places.
Metal straightening
TO category:
Metal bending and straightening
Metal straightening
The curvature of parts is checked by eye or by the gap between the plate and the part laid on it. The edges of curved areas are marked with chalk.
When editing, it is important to choose the right places to strike. The force of the blows should be commensurate with the amount of curvature and gradually decrease as one moves from the greatest bend to the smallest. Editing is considered complete when all irregularities disappear and the part becomes straight, which can be determined by applying a ruler. Straightening is carried out on an anvil, a straight plate or reliable pads that prevent the part from slipping off them upon impact.
To prevent your hands from shocks and vibrations when straightening metal, you must wear gloves and firmly hold the parts or workpieces on the plate or anvil.
Straightening of strip metal is carried out in the following order. On the convex side, mark the boundaries of the bends with chalk, after which left hand put on a mitten and take a strip, and take a hammer in your right hand and take a working position.
The strip is placed on the correct plate so that it flat surface lay on the slab with its convex upward, touching at two points. Impacts are applied to the convex parts, adjusting the impact force depending on the thickness of the strip and the amount of curvature; the greater the curvature and the thicker the strip, the stronger the impacts. As the strip straightens, the impact force is weakened and the strip is more often turned over from one side to the other until it is completely straightened. If there are several bulges, those closest to the ends are straightened first, and then those located in the middle.
The straightening results (straightness of the workpiece) are checked by eye, or more precisely, on a marking plate along the clearance or by applying a ruler to the strip.
Straightening the bar. After checking by eye, the boundaries of the bends are marked with chalk on the convex side. Then the rod is placed on a plate or anvil (Fig. 1) so that the curved part is convex upward. Hammer blows are applied to the convex part from the edges of the bend to the middle part, adjusting the impact force depending on the diameter of the rod and the magnitude of the bend. As the bend is straightened, the impact force is reduced, ending the straightening with light blows and turning the rod around its axis. If the rod has several bends, those closest to the ends are straightened first, then those located in the middle.
Rice. 1. Straightening round metal
Rice. 2. Scheme of straightening sheet material: a, b - bent blanks, c. r - shock distribution
Sheet metal straightening is more complex than previous operations. Sheet material and blanks cut from it may have a wavy or bulging surface. On workpieces that have wavy edges (Fig. 2, a), the wavy areas are first outlined with chalk or a soft graphite pencil. After this, the workpiece is placed on the plate so that the edges of the workpiece do not hang down, but lie completely on the supporting surface, and pressing it with your hand, they begin straightening. To stretch the middle of the workpiece, blows with a hammer are applied from the middle of the workpiece to the edge as shown in Fig. 2, in circles. Circles with smaller diameters correspond to smaller impacts, and vice versa.
Stronger blows are struck in the middle and reduce the force of the blow as you approach its edge. To avoid the formation of cracks and hardening of the material, repeated blows should not be applied to the same place on the workpiece.
Particular care, attentiveness and caution are observed when editing workpieces made of thin sheet material. They do not strike hard, since if the blow is incorrect, the side edges of the hammer can either break through sheet blank, or cause metal extraction.
Rice. 3. Editing thin sheets: a - with a wooden hammer (mallet), b - with a wooden or metal block
When straightening workpieces with bulges, warped areas are identified and it is determined where the metal is bulged the most (Fig. 2). The convex areas are outlined with chalk or a soft graphite pencil, then the workpiece is placed on the slab with the convex sections up so that its edges do not hang down, but lie completely on the supporting surface of the slab. Straightening begins from the edge closest to the bulge, along which one row of blows is applied with a hammer within the limits indicated on the surface covered with circles (Fig. 2, d). Then blows are struck on the second edge. After this, a second row of blows is applied along the first edge and again moves to the second edge, and so on until they gradually approach the bulge. Hammer blows are applied often, but not hard, especially before finishing editing. After each impact, its impact on the workpiece at the impact site and around it is taken into account. Do not allow several blows to the same place, as this can lead to the formation of a new convex area.
Under the blows of the hammer, the material around the convex area is stretched and gradually leveled. If there are several bulges on the surface of the workpiece at a short distance from each other, blows with a hammer at the edges of the individual bulges force these bulges to join into one, which is then adjusted by blows around its boundaries, as indicated above.
Thin sheets rule light wooden hammers (mallets - Fig. 3, a), copper, brass or lead hammers, and very thin sheets are placed on a flat plate and smoothed with metal or wooden blocks(Fig. 3, b).
Editing (straightening) of hardened parts. After hardening, steel parts sometimes warp. Straightening parts that are bent after hardening is called straightening. The straightening accuracy can be 0.01-0.05 mm.
Depending on the nature of the straightening, hammers with a hardened head or special straightening hammers with a rounded
Rice. 4. Straightening of hardened parts: a - on the straightening head, b - square along the inner corner, c - along the outer corner, d - places of impact
the opposite side of the striker. In this case, it is better to place the part not on flat plate, and on the straightening headstock (Fig. 4, a). The blows are applied not on the convex side of the part, but on the concave side of the part.
Products with a thickness of at least 5 mm, if they are not hardened through, but only to a depth of 1-2 mm, have a viscous core, so they are straightened relatively easily; they need to be straightened like raw parts, that is, blows should be applied to the convex places.
The straightening of a hardened square, in which, after hardening, the angle between the flanges has changed, is shown in Fig. 4, 6-year If the angle has become less than 90°, then blows with a hammer are applied at the top of the inner corner (Fig. 84 b and d, left), if the angle has become more than 90°, blows are applied at the top of the outer corner (Fig. 4, c and d, right) .
In case of warping of the product along the plane and along a narrow edge, straightening is performed separately - first along the plane, and then along the edge.
Straightening of short rod material is carried out on prisms (Fig. 5, a), straightening plates (Fig. 5, b) or simple linings, striking with a hammer on convex places and curvatures. Having eliminated the bulges, they achieve straightness by applying light blows along the entire length of the rod and turning it with the left hand. Straightness is checked by eye or by the gap between the plate and the rod.
Rice. 5. Straightening of short shafts and rods: a - on prisms, b - on a plate
Highly springy and very thick workpieces are straightened on two prisms, striking through a soft spacer to avoid nicks on the workpiece. If the forces developed by the hammer are not sufficient for straightening, manual or mechanical presses are used.
Straightening (straightening) is an operation by which unevenness, curvature or other imperfections in the shape of workpieces are eliminated. Straightening and straightening have the same purpose, but differ in the methods of execution and the tools and devices used.
Straightening is the straightening of metal by applying pressure to one or another part of it, regardless of whether this pressure is applied by a press or by hammer blows. „
Editing is, as a rule, a preparatory operation preceding the main metal processing operations.
Subjected to editing steel sheets and sheets of non-ferrous metals and their alloys, strips, rod material, pipes, wire, as well as metal welded structures. Workpieces and parts made of fragile materials (cast iron, bronze, etc.) cannot be corrected.
There are two methods of straightening metals: manual straightening, performed with a hammer on steel cast-iron leveling plates, anvils, etc., and machine straightening, performed on straightening machines. When manually straightening, the mechanic looks for places on the surface of the workpiece or part that, if struck, would straighten the workpiece, that is, lie on the plate without bulges, bends or waviness.
The metal is straightened both in a cold and in a heated state. In the latter case, you need to keep in mind that editing steel billets and parts can be produced in the temperature range 1100-850 °C. Heating above the specified temperatures leads to overheating and then to burnout of the workpieces, i.e., to irreparable defects.
Straightening is used in cases where it is necessary to eliminate distortion of the shape of the workpiece - waviness, warping, dents, bending, bulging, etc. Metal can be straightened both cold and heated. Heated metal is easier to straighten; however, this is also true for other types of plastic deformation, such as bending.
At home, straightening should be done on an anvil or a massive plate of steel or cast iron. Working surface The slab must be level and clean. To reduce the noise from impacts, the stove should be installed on wooden table, with which, in addition, you can level the slab so that it is in a horizontal position.
To edit you need a special locksmith tool. You cannot do it with any hammer that you have at hand; the metal may not only not be straightened, but will receive even greater defects. The hammer must be made of a soft material - lead, copper, wood or rubber. In addition, you cannot straighten metal with square-headed hammers - it will leave marks in the form of nicks on the metal surface. The hammer head should be round and polished.
In addition to hammers, wooden and metal smoothers and supports are used. They are used for straightening thin sheet and strip metal. For straightening hardened parts with shaped surfaces there are proper money.
It is probably not worth reminding that straightening (straightening) of metal must be done in work gloves, regardless of whether the work is complex or not, whether the workpiece is large or small, and whether it is strongly curved.
To check the curvature of the workpiece, you need to lay it on a smooth plate with the surface that should be flat after straightening. The gap between the plate and the workpiece will indicate the degree of curvature that needs to be eliminated. Curved places must be marked with chalk, this makes it much easier to strike with a hammer than focusing only on the curvature noticeable to the eye.
Straightening strip metal bent in a plane is the most simple operation. The curved workpiece must be positioned so that it has two points of contact with the anvil. Strikes with a hammer or sledgehammer should be applied to the most convex places and reduce the force of the blows as the protuberances become smaller. Do not strike only on one side of the workpiece; the metal may bend in reverse side. To prevent this from happening, the workpiece must be turned over from time to time. For the same reason, you should not strike several times in a row at the same place.
If there are several bulges, you first need to straighten the edges of the workpiece, and then its middle.
Straightening round metal - this type of work is basically similar to straightening strip metal - you need to mark uneven places with chalk and position the workpiece with the convex upwards, blows should be applied to the convex part from the edges of the bend to the middle of the convexity. When the main curvature is corrected, the force of the blows must be reduced and the metal rod must be periodically rotated around its axis to prevent curvature in the opposite direction.
Metal rods of square section must be adjusted in the same sequence.
Straightening of metal twisted in a spiral is done by unwinding. In order to straighten the curvature, you need to clamp one end of the twisted metal in a large vice on metalwork table, the other - in a hand vise. Having untwisted the metal to the extent that can be controlled by eye, you need to continue editing on a smooth, verified plate the usual method, controlling the curvature of the light.
