Straightening of strip metal bent along a plane. Straightening sheet metal Straightening steel sheet

Metal straightening

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Bending and straightening of metal

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.

Edit strip metal 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 right hand take a hammer and take a working position.

The strip is placed on the correct slab so that its flat surface lies 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

Edit sheet metal 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 frequently, but not forcefully, 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 are adjusted with light wooden hammers (mallets - Fig. 3, a), copper, brass or lead hammers, and very thin sheets 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 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 becomes less than 90°, then blows with a hammer are applied at the top internal 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 usually preparatory operation, preceding the main metal processing operations.

Steel sheets and sheets of non-ferrous metals and their alloys, strips, rod material, pipes, wire, as well as metal welded structures are subjected to straightening. 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 cold and heated states. In the latter case, you need to keep in mind that straightening steel blanks and parts can be done in the temperature range of 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 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 correct headstocks.

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, 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 corrected. 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 simplest operation. Curved workpiece it 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.

Edit 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 the bench, the other in a hand vice. Having untwisted the metal to the extent that can be controlled by eye, you need to continue straightening on a smooth, calibrated plate using the usual method, controlling the curvature in the light.

Various blanks and products have bulges, waviness, curvature and other irregularities. Straightening and editing corrects detected defects.

Edit- this is the alignment of unhardened parts, workpieces and sheets. A relatively simple process that can be done at home.

Before straightening, the curvature of workpieces and parts is checked. This is done by applying a metal ruler to the part (on the edge) or by eye. The edges of the curved areas are marked with chalk.

Editing is carried out on smooth, reliable pads or on a correct plate. You need to choose the right places to strike. The blows are applied with a force commensurate with the magnitude of the curvature. Gradually reduce the impact force when moving from a larger bend to a smaller one.

Straightening of rods and strip metal is carried out in the following order:

the boundaries of the bends on the convex side are marked;
a hammer is taken in the right hand, a cloth mitten is put on the left ();
the rod or strip is placed on an anvil or on correct slab convex upward. The blows are applied along the convexity towards the middle part from the edges of the bend. As the bend is corrected, the force of the blows decreases, and if necessary, the rod or strip is turned over. If they have several bends, then first straighten the bends located closer to the edges, and then those in the middle;
The results of editing are checked by applying a ruler or by eye.

Straightening metal blanks or sheets

Straightening of metal blanks or sheets is necessary when they have a bulge or waviness.

The procedure for editing blanks and sheets with waviness is as follows:

the boundaries of the undulation areas are outlined with chalk;
the workpiece or sheet is placed on an anvil or on a straight plate so that there is no overhanging edges;
the workpiece or sheet is pressed against the anvil or straightening plate, and straightening begins;
blows are applied with a hammer to the edge from the middle. The force of the blows decreases as you approach the edge. It is prohibited to strike repeatedly in the same place.

Correction of bulges on metal sheets is carried out in the following sequence.

The boundaries of the bulges are outlined with chalk.
The workpiece or sheet is placed on the anvil or plate with its convex side outward, preventing the edges from overhanging.
Editing begins from the bulge closest to the edge.
After this, blows are struck from the second edge. Frequent, but not strong blows are applied. The force of the blows is reduced towards the end of the edit. It is prohibited to strike several times in one place.

When there are several bulges nearby on a metal sheet, the bulges are combined into one with a hammer, and then it is straightened using the technology described above.

Bulging and waviness of thin metal sheets and blanks are straightened with mallets, lead, brass or copper hammers. Very thin sheets are placed on a flat slab and smoothed with wooden or metal blocks.

When straightening parts, workpieces and metal sheets, safety requirements must be observed. Wear gloves to avoid injury from impacts. Workpieces, workpieces and sheets must be held firmly on the anvil or leveling plate to prevent them from jumping off.

Metal straightening

Straightening is used in cases where it is necessary to eliminate distortion of the workpiece shape - waviness, warping, dents, bending, bulging, etc. Metal can be straightened both cold and heated. Heated metal is easier to straighten, which 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. The working surface of the stove must be smooth and clean. To make the impact noise less loud, the stove should be placed on a wooden table, which can also be used to level the stove so that it is in a horizontal position.

A special metalworking tool is required for editing. You cannot do it with any hammer that is at hand; the metal may not only not be straightened, but also get even larger 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 surface. The hammer head should be round and polished.

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, or 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 corrected. Curved places must be marked with chalk - this makes it much easier to strike with a hammer than when focusing only on the curvature noticeable to the eye.

Straightening of strip metal bent in a plane- This is the simplest 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. You should not strike only on one side of the workpiece - the metal may bend in the opposite direction. 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 must first straighten the edges of the workpiece, and then its middle.

Editing round metal. This type of work is basically similar to straightening strip metal. To do this, you need to mark uneven places with chalk and place the workpiece with the convex side up, applying blows 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 metal twisted in a spiral produced by the unwinding method. In order to straighten the curvature, you need to clamp one end of the twisted metal in a large vice on the bench, the other in a hand vice. Having untwisted the metal to the extent that can be controlled by eye, you need to continue straightening on a smooth, calibrated plate using the usual method, controlling the curvature in the light.

Sheet metal straightening

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 at the same time (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: they will not only leave dents, but can also tear the 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.

The one who did the editing 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: tubercles are usually obtained by cutting a large number of mutually intersecting grooves located close to each other on a smooth slab. 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.

Editing hardened metal (straightening)

Soft straightening hammers are not suitable for straightening hardened metal. A special hammer with a hardened metal head or a rounded narrow side is required. You can make a straightening hammer yourself. To do this, it is necessary to make a slot in the narrow hammer head and tightly press a plate of wood, sharpened to a radius of 0.1–0.2 mm, into it. hard alloy VK6 or VK8.

Hardened metal is straightened using the reverse method: blows must be applied not to the convex, but to the concave section of the workpiece: it will begin to straighten due to the fact that the metal on the concave side will stretch (Fig. 16).

Rice. 16. Editing of hardened metal (straightening): a – strips; b, c – squares.

It is more convenient to perform straightening not on a flat plate, but on a special straightening headstock, which has a convex surface, moving the workpiece up and down along it.

It seems an impossible task for an inexperienced mechanic to straighten a flat square whose angle has changed and become more or less than 90°. Such squares are no longer suitable for checking right angles, and, as a rule, they are thrown away. Meanwhile, the hardened metal square can be straightened. If the right angle has decreased and is less than 90°, then blows with a hammer must be applied along the plane of the square at the top of the inner corner. If the angle has increased and exceeds 90°, blows should be applied at the top of the outer corner.

After the metal is straightened, you can begin further processing.

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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. Editing is carried out on a plate or reliable supports that prevent the part from slipping upon impact. Manual and machine straightening of metals should be done using gloves.

The curvature of parts is checked by eye or by the gap between the plate and the part laid on it. Bent areas are marked with chalk.

When straightening by hand, the hammer must be held by the end of the handle, as when chopping metal. Apply blows only with the convex part of the striker; Impacts from the edge of the striker leave nicks on the surface of the straightened part.

Straightening of strip metal is done manually on a straightening plate or anvil using a bench hammer.

The simplest thing is to straighten metal bent along a plane (Fig. 44, a). This type of editing is the most common; it is usually performed without any particular difficulties. It is more difficult to straighten metal that is bent along an edge (Fig. 44, b). If in the first case the task is to simply level the plane, then here you have to resort to tensile deformation of part of the metal, i.e. straightening. Even more difficult is the editing of twisted strips (Fig. 44, c).

Sometimes all the indicated types of bends are found in one workpiece. To completely straighten such metal, you need to implement a whole range of techniques. The curved strip is placed on the slab with the curved part up and, holding it with the left hand, the right hand applies strong blows with a hammer to the convex places, striking first at the edges of the convexity and, gradually, as the strip straightens, bringing the blows closer to the middle of the convexity. The greater the curvature and thickness of the strip, the stronger the blows should be and, conversely, as the strip straightens, they are weakened, ending the straightening with light blows. During the straightening process, the strip must be periodically rotated from one side to the other as necessary. Having straightened the wide side, proceed to

Straightening the ribs by turning the workpiece onto the edge. After one or two blows, the strip should be turned from one edge to another. As the curvature decreases, the impact force should be reduced.

Straightening of edge-bent strips is carried out by straightening. In such cases, strong blows are applied with the toe of a hammer in order to unilaterally stretch (lengthen) the bending points; strikes with the striker should be applied from the stretching points on the plane to the edges of the strip or workpiece.

It is recommended to straighten strips that have a twisted bend using the unwinding method. Such a workpiece is clamped in a vice and untwisted using a lever or hand vice. Finish editing on a plate or anvil with light blows of a hammer.

Straightening a thin steel strip curved along an edge is performed in a different sequence: the curved strip is placed on the plate and, pressing it with the left hand, the right hand strikes with a hammer in rows along the entire length of the strip, gradually moving from the lower edge to the upper. At first the blows should be strong, and as you move to the top edge they should be weaker, but delivered more often. With this method of straightening (straightening), the lower edge is extended more than the upper one, and the strip becomes even.

The elimination of irregularities after straightening is checked by eye, or more precisely, on a marking plate along the clearance or by applying a ruler to the strip.

Straightening sheet metal is a more complex operation. It depends on the type of deformations that acted on the sheet metal during rolling, cutting into dimensional pieces, electric gas cutting, punching, etc.

All sheet deformations can be divided into three types. The first type of deformation includes bulges and dents in the middle of the sheet or workpiece. The second type of deformation is characterized by waviness of the edges and edges of the sheet. The third type of deformation includes both convexity and waviness of the edges of the sheet and workpieces.

This type of deformation is called mixed or complex. Depending on the type of deformation, sheet editing has its own characteristics.

Editing a sheet with bulges is done in the following way. The sheet is placed on the slab with the convex side up and outlined with chalk. The edges of the sheet will touch the plate. Then, supporting the sheet with the left hand, the right hand strikes with a hammer from the edges of the sheet towards the convexity. Under the influence of such impacts, the flat part of the sheet adjacent to the slab will be stretched, and the convexity will gradually straighten.

If there are several bulges on the sheet, then blows should be applied in the spaces between the bulges. As a result of this, the sheet is stretched, and all the bulges are brought together into one common one, which is straightened in the manner indicated above.

It must be remembered that if a sheet with a convexity does not adhere to the edges of the slab, then it should be pressed either by hand or by placing a weight on the convex part of the sheet. If you do not do this and strike with a hammer on a sheet that does not fit tightly to the slab, then it will have many dents, and you will not be able to extract metal along the edges of the sheet. This increases the editing time and creates noise that tires the worker.

Having straightened the sheet on both sides, you should see how much the bulge has decreased. If it is still significant, then it is necessary to repeat the blows in the same order, but with less force until straightness is obtained over the entire sheet.

Editing a sheet that has deformation in the form of waviness along the edges, but with a flat middle, is performed in a similar way. Before straightening, placing the sheet on the plate, a weight is placed on one of its wavy edges, while the other is pressed against the plate by hand. This position is maintained when editing the sheet.

From the impact of impacts, the sheet in the middle part will be stretched and the waves along the edges of the sheet will begin to disappear. After this, the sheet should be turned over and editing continued in the same way until the required straightness is obtained.

Editing thin sheets is done with wooden hammers - mallets (Fig. 45, a); very thin sheets are placed on a straight plate and smoothed with smoothing irons (Fig. 45, b).

Straightening of short rod metal with a diameter of up to 30 mm and a length of up to 3 m is usually carried out with a metalworker's hammer on a leveling (straightening) plate. The straightening process in this case comes down to striking with a hammer the convexity of the rod placed on the plate, and checking the straightness by eye and the clearance between the plate and the rod. During the straightening process, the rod should be constantly rotated around its axis. Long bars are straightened on special roller straightening machines.

Editing (straightening) of hardened parts. After hardening, steel parts sometimes warp. In some cases, parts or tools that have undergone hardening are subject to deformation. The cause of deformation (warping) is internal stresses created by rapid cooling of parts in the quenching liquid. To eliminate the curvature of such parts, they are straightened. Straightening of hardened parts is called straightening. The straightening accuracy can be 0.01-0.05 mm.

Depending on the nature of straightening, different hammers are used: when straightening parts or tools on which traces of hammer blows are unacceptable, soft hammers (made of copper, lead) are used. When straightening, which involves significant deformation of the heated part, use a mechanic's hammer weighing from 200 to 600 or a special straightening hammer with sharp strikers (Fig. 46, a). The plate for straightening (straightening) must have a smooth polished surface.

The warped part is placed on the slab with the convex side down, pressing it tightly with the left hand to the slab and holding it by one end, applying gentle but frequent and accurate blows with the toe of a straightening hammer in the direction from the center of the concavity to its edges. This achieves stretching of the upper metal fibers on the concave side of the part and straightening it.

Products with a thickness of at least 5 mm, if they are not hardened through and 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 convex places.

Straightening (straightening) of parts of a more complex shape, for example a square, in which, after hardening, the deformation caused a perpendicular violation

These sides are produced as shown in Fig. 46. If the square has an angle of less than 90°, then it should be straightened at the top of the internal corner (Fig. 46, 6), and if the angle is more than 90°, then the square should be straightened at the top of the outer corner (Fig. 46, c). The straightening of the square is completed when its edges accept correct form and both angles will be 90°

In case of warping of parts or tools along the plane and along a narrow edge, they should be straightened separately: first along the plane, and then along the edges.

It should be noted that precision parts and tool blanks that have been straightened under a press or hammer in a cold state must be subjected to repeated tempering to relieve stress.

Heated editing. Profile metal (angles, channels, tees, I-beams), hollow shafts, thick sheet steel, forgings are straightened by heating the curved area (convexity) blowtorch or with a welding torch until cherry red; The layers of metal surrounding the bulge are cooled with damp asbestos or wet ends.

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 The following types of tolerances for the shape of finished products are stipulated:

For bars of round and square cross-section - spatial curvature and apparent curl
For square bars, 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 of the finished product 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 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 blanks from 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 machines horizontal version, which 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 are characterized by high productivity. Rods are also 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. The shock nature of the load created by a screw press does not ensure proper straightening quality 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.

Straightening of rods and strip metal is carried out in the following order:

Straightening metal blanks or sheets

Types of metal straightening

Straightening equipment

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