Editing plumbing. Presentation: Straightening and bending of metal. Types of bent parts
The metallurgy industry is actively developing, one of the most popular and widespread techniques in this area is metal bending and straightening.
What is the technology of the metal straightening and bending process?
Metal straightening is the process of eliminating flaws and defects in a metal workpiece. Defects can be considered bulges, waves on the surface, scratches, curvatures, and depressions. The essence of metal straightening operations comes down to compressing the bulges on the surface and expanding the depressions.
Editing can be carried out both when the metal is cold and when it is heated.
The choice of the state of the metal during heating depends on the size of the defects; for example, in case of serious damage to the surface, it will be easier to eliminate defects using hot straightening technology, and in case of small defects, you can work with cold metal.
Straightening can be done manually, using a steel or cast iron straightening plate, or it can also be done by machine, using a press.
The process of bending metals is very close to straightening. Bending is necessary to give the workpiece a curved shape.
The essence of this technology is that one part of the part is bent relative to the other at a certain angle. The action takes place under heavy load. In this case, it is important that the bending stress is greater than the elastic limit, and the deformation, which is a consequence of the load on the part, must be plastic. Otherwise, the workpiece will not retain its shape.
Types of metal straightening technologies
There are two types of straightening and bending of metals – manual and machine. Ductile metals such as copper and steel are subject to straightening and bending. Brittle metals cannot be edited.
Editing is necessary not only to eliminate defects, but also after welding, soldering and cutting blanks from sheets under the influence of temperatures.
- Manual editing Suitable if you need to correct minor defects. To perform it, tools such as sledgehammers based on cast iron and steel plates, as well as anvils are used. Requires a lot of effort.
- Typically used today machine straightening and bending. It provides a better result, in addition, the process is much easier. Performed using presses and rollers.
For straightening, round-faced hammers that have a strong handle are best, and sometimes bench hammers and hammers with soft metal inserts are also used. To straighten sheets, bars are used.
On an industrial scale, only machine methods are used. The workpiece is passed between rollers that rotate in different directions. Under their pressure, the metal becomes smooth.
When using a press, the workpiece is placed on supports, then the press is lowered onto it, as a result of which the workpiece is also straightened. As a rule, in case of serious defects, the metal is straightened under the influence of temperatures. The optimal temperature for this is 350-450 degrees; you cannot heat it any more, as burnout is possible.
When performing cold straightening, the temperature should be about 140 degrees. At a temperature of 0 degrees it is impossible to edit, as the metal becomes brittle and breaks.
Metal straightening and bending processes are used everywhere. When bending, it is very important to correctly calculate the bend angle and proportions. To carry out these processes efficiently, it is necessary good equipment – bending machines and the press.
Modern technologies for bending and straightening metal at the exhibition
In May, the metalworking exhibition “” will traditionally be held in Moscow. At this event, the world's leading engineers will present their developments.
The exhibition will show high-quality and reliable the latest machines for working with metals, and innovative developments are explained at presentations. The exhibition will take place at the Expocentre Fairgrounds.
Mechanical editing
TO category:
Bending and straightening of metal
Mechanical editing
Straightening is a method of processing workpieces with hammers or using special devices in order to eliminate deviations in the shape and location of surfaces. The main purpose of editing is to reduce allowances for subsequent processing. Correctable deviations include warping, dents, bulges, bends, and twisting.
Rice. 1. Straightening of sheet blanks: 1 - workbench, 2 - straightening plate, 3 - places of impact, 4 - bulge, 5 - weak blows, 6 - strong blows, 7 - sequence of blows
At the location of the defect, concave and convex sides appear on the workpiece. The fibers of the material on the concave side are compressed, and on the convex side they are stretched. Straightening is carried out in order to equalize the lengths of the fibers of the convex and concave sides, stretching the concave side or compressing the convex side. The concave side is stretched by purposefully hitting it with a hammer. At the center of the impact, the material is plastically deformed (compressed). Along the edges of the impact zone, particles of material are shifted to the sides and elongation of the material occurs, i.e., it is drawn out. A more significant drawing is achieved by striking the narrow toe of the hammer, as this increases the pressure on the surface of the workpiece. When processing with a flat hammer head, the degree of elongation is lower, and the hardening of the surface layer is higher.
Types of editing. IN plumbing Cold and less often hot straightening (manual and mechanized) is used, carried out by stretching, unwinding, bending and straightening.
Tools and accessories for editing. The main tool for manual straightening is hammers. The most commonly used hammers are those with a round head and a convex sphere. The square striker may leave indentations in the workpiece. The firing pin must be ground, and when performing particularly critical work, polished. To straighten hardened steel sheets, special hammers with a narrow, rounded side of a hardened striker or with hard, high-strength inserts are used. Straightening of soft, thin and cleanly processed workpieces sheet material carried out with hammers with inserts made of hardwood, copper, aluminum, lead, rubber, polyurethane.
Regular (steel or cast iron) plates with a flat surface are used as a strong, non-deformable support for the workpiece. They are installed on a strong and stable base.
Various devices are used for straightening bars made from long products, such as prisms, linings of various configurations, and bench vices. For machine straightening, presses are used various types(screw, hydraulic, pneumatic), sheet straightening machines, horizontal stretching machines.
Sequence and methods of performing work when editing. First, visually determine the convex part of the workpiece and mark its boundaries with chalk or pencil. Then they choose the straightening method, the necessary tools and devices, outline the straightening scheme, the places and sequence of blows, their strength. The thicker the workpiece, the stronger its material and the greater the deflection, the stronger the blows should be. As the workpiece is straightened, the force of the blows should be reduced. During the editing process, it is necessary to constantly evaluate the results of each blow and make the necessary adjustments to the intended processing scheme.
When manually straightened, hardened workpieces are placed on a straight plate. Then, using the toe of a hammer, apply even blows along the edge of the concave side. Gradually the force of the blows is reduced and they are applied as if in the intervals between the places of the first blows. The material “accelerates” to the sides, the concave side lengthens and the workpiece becomes straight. Several successive blows to one place can cause the appearance of new bulges, increased hardening, cracks and fractures.
When editing sheet material with the most complex look work is to eliminate bulges. Attempts to eliminate them by hitting the bulge itself will lead to its increase. The processing is carried out with a flat hammer head so as to stretch the layers of material adjacent to the convexity. If the bulge is in the middle of the workpiece, then the blows are applied from edge to bulge, gradually reducing the force of the blows and changing their places. If there is a convexity at the edge of the workpiece, blows are applied from its middle to the convexity. The straightening of a workpiece with several convexities begins with blows in the spaces between the convexities in the direction towards the convexities.
With large deviations in shape and large thickness and strength of the workpiece material, the force of the hammer blow is not enough for straightening. In this case, editing is carried out on presses.
Flexible (bending) is an operation as a result of which the workpiece takes the required shape (configuration) and dimensions due to stretching of the outer layers of metal and compression of the inner ones. During bending, all the outer layers of the material are stretched, increasing in size, and the inner layers are compressed, correspondingly decreasing in size. And only the metal layers located along the axis of the bent workpiece retain their original dimensions after bending. When bending, it is important to determine the dimensions of the workpieces. In this case, all calculations are carried out relative to the neutral line, i.e. those layers of the workpiece material that do not change in size during bending. If the drawing of a part that must be made flexible does not indicate the size of the workpieces, the mechanic must independently determine this size. The calculation is made by calculating the size of the part according to midline(determine the length of straight sections, calculate the length of curved sections and summarize the data obtained).
Bending can be done manually, using various bending devices and using special bending machines.
Tools, devices and materials used
when bending
The tools used for bending sheet material with a thickness of 0.5 mm, strip and rod material with a thickness of up to 6.0 mm are steel hammers with square and round strikers weighing from 500 to 1000 g, hammers with soft inserts, wooden hammers, pliers and round nose pliers. The choice of tool depends on the material of the workpiece, the dimensions of its cross-section and the design of the part that should be obtained as a result of bending.
Bending with a hammer is carried out in a metalworker's plane-parallel vice using mandrels (Fig. 2.44), the shape of which must correspond to the shape of the part being bent, taking into account the deformation of the metal.
Hammers with soft inserts (see Fig. 2.33) and wooden hammers - mallets are used for bending thin-sheet material up to 0.5 mm thick, non-ferrous metal blanks and pre-processed blanks. Bending is done in a vice using mandrels and linings (on the jaws of the vice) made of soft material.
Pliers and round nose pliers are used when bending profiles with a thickness of less than 0.5 mm and wire. Pliers (Fig. 2.45) are designed to grip and hold workpieces during the bending process. They have a slot near the hinge. The presence of a slot allows you to bite off the wire. Round nose pliers (Fig. 2.46) also provide gripping and holding of the workpiece during the bending process and, in addition, allow wire bending.
Manual bending in a vice is a complex and labor-intensive operation, therefore, to reduce labor costs and improve the quality of manual bending, various devices are used. These devices are usually designed to perform a narrow range of operations and are manufactured specifically for them.
In Fig. Figure 2.47 shows a device for bending a hacksaw square. Before bending, roller 2 of the bending device is lubricated with machine oil. Lever 1 with bending roller 2 is moved to the upper position A. The workpiece is inserted into the hole formed between roller 2 and mandrel 4. Lever 1 is moved to the lower position B, giving the workpiece 3 the desired shape.
Other bending devices work in a similar way, for example, a device for bending a ring from a rod round section(Fig. 2.48).
Most complex operation is pipe bending. The need for pipe bending arises during assembly and repair operations. Pipe bending is carried out both in cold and hot conditions. To prevent the occurrence of deformations of the internal lumen of the pipe in the form of folds and flattening of the walls, bending is carried out using special fillers. These features determine the use of some specific tools, devices and materials when bending pipes.
Devices for heating pipes. Hot bending of pipes is carried out after preheating with high frequency currents (HFC), in fiery furnaces or furnaces, gas-acetylene torches or blowtorches directly at the bending site. The most rational heating method is HDTV heating, in which heating is carried out in a ring inductor under the influence of a magnetic field created by high-frequency currents.
Fillers when bending pipes are selected depending on the material of the pipe, its size and bending method. The following are used as fillers:
Sand - when bending pipes with a diameter of 10 mm or more made of annealed steel with a bending radius of more than 200 mm, if it is carried out in both cold and hot states; pipes with a diameter of over 10 mm from annealed copper and brass with a bending radius of up to 100 mm in a hot state;
Rosin - for cold bending of annealed copper and brass pipes with a bending radius of up to 100 mm.
The use of filler when bending pipes is not required if they are made of annealed steel, have a diameter of up to 10 mm and a bending radius of more than 50 mm. In this case, bending is done in a cold state. Also, pipes made of brass and copper with a diameter of up to 10 mm with a bending radius of over 100 mm are cold bent without filler. Without filler, pipes are bent in special devices, where backpressure, which prevents the occurrence of deformations in the internal lumen of the pipe, is created by other means.
The simplest device for bending pipes is a plate, fixed on a workbench or in a vice, with holes in which pins are installed (see Fig. 2.47). The pins act as stops needed when bending pipes. Roller devices of various designs are also used.
Edit- this is a metalworking operation for straightening workpieces and parts that have dents, bends, or warping.
The metal is straightened in cold and hot conditions. The choice of straightening method is determined by the amount of deflection, the dimensions of the part and the material.
Only ductile materials - steel, copper, aluminum and their wrought alloys - are subject to straightening. The impact force at the edge of the curve is greater, at the edge of the sheet it is less.
Straightening- This is the editing of hardened parts, as well as parts bent through a stiffener.
When straightening parts, blows with a straightening hammer are applied to the concave (shortened) sides of the workpiece. In this case, the metal at the impact sites is plastically deformed, the shortened layers of metal are lengthened and the part is unbent.
Straightening of strip and rod metal is carried out on plates and anvils. Hammer blows are applied to the convex part. The quality of editing is checked by eye, with rulers or on plates.
Correct slabs are made of steel or gray cast iron. The mass of the slab should be 80-150 times the mass of the hammer.
Straightening hammers are used with round polished heads. Square-faced hammers leave nicks in the metal.
Wooden hammers used for straightening thin sheet metals.
Straightening of shafts with slight curvatures is carried out by applying light blows with a hammer to the concave side of the shaft, which leads to its lengthening and correction of the shaft. if the force from the hammer is not enough, screw or hydraulic presses are used.
Shafts straightened in this way may have internal residual stresses, which lead to their bending during operation. To eliminate stress, the shafts are heated to a temperature of 400-500 degrees.
Editing by heating is used to correct profile metal(corners, channels).
Editing is carried out using a non-stress method. Heat the curved part blowtorch or gas burner to a dark cherry color of 800-850 degrees, the parts of the part surrounding the convexity are cooled with wet asbestos or wet rags. In this case, the heated layers quickly reduce their length and unbend the part.
Bending- a method of pressure processing in which a workpiece or part thereof is given a curved shape.
Only plastic materials are subject to bending. The essence of bending is that, under the influence of forces exceeding the internal elastic forces of the metal, the workpiece is plastically deformed and one part of it is bent relative to the other at a given angle.
For pipe bending, fillers are used to prevent defects. The filler puts pressure on inner surface pipe wall and prevents changes in cross-sectional shape. Liquids and bulk materials are used as fillers when bending pipes.
When bending a workpiece, its various layers in cross section behave differently. The layers on the convex part of the workpiece are stretched, on the concave part they are compressed, and in the middle they do not change their length, and its length before and after bending remains constant. Therefore, the middle layer, the neutral line, can be used to determine the blank length of a curved part.
Pipe flaring consists in increasing the diameter of the end of the pipe or giving it conical shape. Used in preparing pipes for the formation of detachable and permanent connections
Lecture notes on the topic:
Metal cutting
cutting section, sheet and other metals are performed: without removing chips (manual or mechanical scissors, pipe cutters, nippers) and with removing chips ( hand hacksaw gas electric cutting)
The essence of cutting with scissors is this. that under the pressure of a pair of opposing knives, the metal is plastically deformed and divided into parts in the plane of movement of the knives.
The harder the metal being cut, the larger angle sharpening of the knife blade, for soft metals it is 65 g, for metals of medium hardness 70-75, for hard metals 80-85.
To reduce the friction of the knives on the metal being cut, the blades are given a small back angle of 1.5-3 degrees.
Hand scissors used for cutting steel sheets up to 0.5-1.0 mm thick, and for non-ferrous metals up to 1.5 mm thick.
According to the location of the cutting edges, scissors are divided into right-handed (with a bevel of the cutting part with right side) and left (with a bevel of the cutting part on the left side)
With right-handed scissors it is convenient to cut in a straight line and along a curve without rounding, because The marking mark is constantly visible. The left scissors are used to cut along the right edge of the sheet counterclockwise.
Chair scissors unlike manual ones, they have large sizes and are used for cutting sheet metal up to 3 mm thick
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Fig 1 Chair scissors
pic 2
Distance between cutting edges adjacent teeth - the tooth pitch for hand hacksaw blades can be 0.8-1.6 mm. The thinner the workpiece, the smaller the tooth should be. To make cutting easier, the teeth of the hacksaw blades are bent to the sides and moved apart.
The cutting speed should be 30-60 working strokes per minute. A high cutting rate leads to overheating and rapid dulling of the blade.
Brass and bronze are cut only new hacksaw blade. even slightly worn teeth do not remove chips due to low coefficient friction of these alloys
Lecture notes
Metal straightening and bending
TO category:
Metalwork and assembly works
Metal straightening and bending
Edit. Bends, local irregularities, bulges and dents appear on metal workpieces and parts after annealing, welding, cutting and other operations. various shapes, waviness and other defects. The operation to eliminate these defects is called editing.
Manual editing sheet metal is produced on a slab or anvil using wooden hammers or hammers made of copper, lead, aluminum or rubber.
Workpieces made of bar and profile steel are adjusted with steel hammers with a round convex striker. Large workpieces they rule with blows of a sledgehammer or with mechanical hammers and presses.
Since when struck with a steel hammer, marks inevitably remain on the metal, when straightening products with an already treated surface, pads made of soft materials(wood, brass, etc.). Thin sheet precious metal(gold, silver), as well as foil, are straightened by smoothing with wooden or metal irons.
The most labor-intensive operation is the straightening of sheet metal. There are three cases: straightening the waviness of the strip or at the edges (Fig. 1, a), straightening curved (crescent-shaped) workpieces under the ruler (Fig. 1, b) and straightening bulges.
When straightening the waviness of a strip or along the edges of a workpiece, which is most often obtained by cutting it out of a sheet, blows are applied with a hammer, starting from the most convex places to the edges of the fissure. 1, a). The strongest blows are applied in the middle and the force of the blow is reduced as they approach the edges. Thus, the convex sections of the strip are settled and the waviness is leveled out.
The thinner the sheet workpiece, the more carefully and carefully the editing must be done, since if the hammer is hit incorrectly, its side edges can easily damage the workpiece or even pierce it.
Straightening of long, narrow crescent-shaped workpieces is carried out on a plate under a ruler. To do this, the workpiece is placed on the slab, pressed against the slab with one hand, and blows are struck with a hammer (wooden or steel with a convex head), starting from the shorter concave edge of the curved workpiece, i.e., the one where the metal fibers are compressed and need to be stretched in order to so that the workpiece is level. At the beginning of straightening, the blows on the concave edge should be stronger, and as they approach the opposite edge, they should become weaker and weaker. This ensures that the concave, shorter edge is gradually extended and the workpiece is straightened, which is controlled by a ruler (Fig. 1, b).
Rice. 1. Straightening of strip and sheet metal: a - straightening of the strip on the plate; b - editing of a strip having a crescent curvature; c - edit sheet stock with a bulge
Rice. 2. Consecutive operations of bending a lattice element from a square bar on a special mandrel: c - mandrel, b - successive bending operations
Flexible. Using bending, a curved product is obtained from a straight blank. Bending of the workpiece is carried out by bending it around any mandrel, the shape of which it takes, in a vice or on a plate to the desired angle. In Fig. 2 shows the mandrel and successive bending operations (1-6) of a square rod for the manufacture of a lattice element. For thick workpieces, bending is carried out with blows of a hammer, preferably a wooden one, which does not leave any traces of impact on the metal. Sometimes bending is done by eye or according to a template. The wire is bent with pliers or round nose pliers (Fig. 3).
During the bending process, the outer layers of the metal are stretched and lengthened, while the inner layers are compressed and shortened. The so-called neutral layer remains unchanged in length, which for workpieces symmetrical in cross-section (square, rectangular, round, oval, hexagonal, etc.) lies at an equal distance from the sides, in the middle, and for asymmetrical profiles (triangular, semicircular) the neutral layer passes through the center of gravity of the section.
Rice. 3. Modern jewelry
The dimensions obtained in the examples should be rounded to a larger value for filing the edges to size after bending.
Often the length of the workpiece is indicated on the drawing; then there is no need to define it. If the bending radius is very small, then cracks may form in the metal. To avoid this, do not bend along radii smaller than twice the thickness of the workpiece.
Sheet metal after rolling has a fibrous structure. To avoid cracks, it should be bent across the fibers or so that the bend line makes an angle of 45° with the rolling direction.
When bending sheet metal parts (and in in some cases also round and round wires square section, strips, etc.) the phenomenon of springing occurs, i.e. the bending angle increases slightly, and the part straightens after the stress is removed. The magnitude of the angle through which the part is straightened, due to elastic recoil, depends on the degree of elasticity of the metal, its thickness and bending radius. It is very difficult to accurately determine the spring angle in advance, so the workpieces have to be bent more strongly, i.e. with obviously smaller radii and bending angles, and the equipment (mandrels) to obtain precise bends of the parts must be selected and refined (finished) experimentally.
