The initial metal rolling, both sheet and volumetric, does not always have flatness indicators sufficient for the high-quality performance of subsequent deformation operations. In such cases, metal correction is used as a preliminary operation. A related term - metal straightening - is a variation of this operation, as a result of which only the axis of the bar is aligned.

State standards stipulate the following types of tolerances for the form of finished hire:

1. For bars of round and square cross-section - spatial curvature and apparent curl
2. For bars of square section, in addition - concavity and convexity of the faces;
3. For steel strips - non-flatness, crescent, convexity of the side faces.
4. For sheets - non-flatness.
5. For ribbons and rolls - telescopic and rib 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 reason for such curvatures can also be separation operations on sheet and high-quality scissors, when the edges of the sheet / strip or the ends of the rods are unacceptably curved.

Even more prerequisites for editing during hot stamping. Finished forgings are bent when:

• Ejection from the cavity of a stamped stream (especially often this occurs with forgings of complex shape);
• Heat treatment, after which internal residual stresses occur in the metal;
• Trimming the flake due to uncontrolled shrinkage of the metal.

In cold stamping technologies, metal dressing is performed after bending parts from high carbon or spring steels, as well as during cold extrusion of products with a long rod part. Editing and straightening of metal in the form of a roll before its dissolution on tapes is also quite common.

The basis for the inclusion of such an operation in the production process is the results of measurements of the shape of the parts, for which either special templates or a universal measuring tool are used. With minor deviations, manual straightening of the metal is sometimes acceptable, but in most cases this is not enough.

Varieties of editing metal

The operation in question can be performed in the cold and hot state. In the hot state, forgings rule that have already passed all the deformation transitions, including clipping. In this case, they do not provide for a separate operation, but deform the edging press stamp in the final stream (although in justified cases, hot dressing of the metal can also be performed on the main stamping equipment). The advantages of such processing are considered to be lower energy intensity, as well as a beneficial effect on the structure and operational properties of the forging material.

Cold dressing in hot stamping is applied after the stamped products have undergone heat treatment. The tool for such an operation is very simple, and the configuration of the working cavity is fully consistent with the dimensions of the forging, which are shown in its drawing. The operation is often performed simultaneously in two planes, which improves the quality of the finished product.

In sheet stamping, editing is performed:

• After cutting-punching of plate metal, when the cutting of the metal fibers of the workpiece leads to the occurrence of internal stresses;
• After free bending (especially without pressing), to remove defects in the shape of the workpiece that arose due to springing;
• When stamping completely, when the curvature of a metal billet occurs due to intense friction of the product along the matrix;
• After multi-junction extraction of parts with flanges.

In cold stamping, compression is distinguished by smooth, punched and wafer dies. In the first case, a flat surface calibration is carried out, therefore, this method is effective for thin-sheet blanks of metals with high ductility. The specific forces do not exceed 100 MPa, and there are no imprints of the tool on the surface of the finished product.

For workpieces with a greater thickness, as well as of metals of increased hardness, it is necessary to perform point / waffle dressing. On the working tool, small incisions are made in the form of teeth, and their points on the punch and matrix should not coincide. The specific efforts are higher, up to 250 ... 300 MPa, but as a result, all surface defects are corrected.

Sometimes flat dressing is done before rolling. The initial 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, supporting).

Editing Equipment

If these transitions are combined with the basic operations of deformation (as is often the case with hot stamping), then special equipment is not required. Cold editing of metal bars or strips is performed on. They are horizontal machines that operate on the principle of rotational stamping.

The difference is that the pressure created by the working rollers must not exceed the ductility limit of the material being straightened. Such machines operate in automatic mode, and therefore are characterized by high performance. The rods are ruled in the same way, only the profile of the working rollers in this case is performed not flat, but according to the cross section of the source material.

It is possible to straighten bulky workpieces in terms of presses. If the specific force does not exceed 300 MPa, then screw presses with the F17__ series arc drive are used. The effect is achieved due to the high speed of impact of a flat die (attached to the slider) with the product, which requires editing. Since the pressure distribution over the entire surface is the same, then at the same time on the working plate there may be several parts of the same overall dimensions. This reduces the complexity of the operation.

The most difficult and responsible is the editing of parts after cold extrusion. Since the strain hardening of the material is very large, the specific forces can reach the limit of plasticity, i.e. 600 ... 800 MPa and even more. The impact nature of the load created by the screw press does not provide the proper quality of dressing 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 scheme of such a press is the ability to ensure exposure of the part (up to 2 ... 3 s) under pressure at the extreme lower position of the equipment slide. As a result, internal stresses are overcome, and the part is aligned.

DURING THE CLASSES

Plan

1. Editing metal.

2. Tools and devices used in straightening metal.

3. The basic rules for performing work when dressing metal.

4. Typical defects when editing metal, the reasons for their appearance and methods of prevention.

5. Safety rules when editing metal.

We must learn to do everything so well

as soon as we can, and identify our mistakes.

Karl Raymond Popper

Hello dear students!

Before proceeding directly to the subject of our consideration, this acquaintance with metal dressing technology, let me tell you a little about labor organization, about

how to equip a workplace, which tools to choose and which ones to use

materials. So, let's begin….

Workplace equipment is far from the last thing, although many often do

do not pay attention to this moment. No matter what you have, be it

a small tool box or an entire workshop — order should be everywhere. AND

the speed of execution depends on how quickly you find the tool you need

one or another work. And besides, it’s much nicer when everything lies in its place and

always at hand.

Rolled metal, pipes and sheet steel due to improper transportation methods

and storage are warped, bent. To eliminate these defects apply

Edit- This is an operation to straighten a curved or warped metal, which can only be subjected to plastic materials: aluminum, steel, copper, brass, titanium.

There are two types of metal dressing: dressing in the cold state and in the hot state. Edit by

  on special regular plates, which are made of cast iron or steel.

Editing of small parts can be done on blacksmith anvils. Edit

metals performed by hammers of various types depending on the condition

surface and material of the part to be edited.

When editing workpieces with a rough surface, hammers with

round strikers weighing 400g. A round firing pin leaves less marks on the surface than a square one.

When dressing workpieces with a machined surface, hammers are used that have hammer strips with soft inserts (made of copper, aluminum) that do not leave marks on the surface. When editing sheet material, wooden mallet hammers are used, and very thin sheets are ruled by wooden or metal bars-ironers.

Editing is carried out in several ways: by bending, stretching and smoothing.

Bendingused in straightening round (rods) and profile material, which

have a sufficiently large cross section. In this case, they use hammers with steel strikers. The workpiece is positioned on the correct plate with the bend up and strikes inflicted on convex places, bending the workpiece in the direction opposite to the existing bend. As the workpiece straightens, the impact force is reduced.

Edit by pullingused in straightening sheet material having a bulge

or waviness. Such editing is carried out with hammers with soft metal dies or mallets. In this case, the workpiece is laid on a regular slab with bulges upward and frequent light blows are applied, starting from the bulge border, towards the edge of the workpiece. The strength of the blows gradually decreases. In this case, the metal is drawn to the edges of the workpiece and the bulge is straightened due to this traction.

Editing by smoothingused in cases where the workpiece has a very small thickness. Smoothing is carried out with wooden or metal bars. The workpiece is smoothed on the correct plate, pulling the material with the help of trowels from the edge of the roughness to the edge of the workpiece, and by pulling the material, the surface of the workpiece is aligned.

Tools and devices used during dressing

Right slabsmade of gray cast iron with worktops

1.5 x 5.0; 2.0 × 2.0; 1.5 × 3.0; 2.0 × 4.0m. On such plates profile blanks and

blanks from sheet and strip material, as well as rods from black and color

Tailstockused for straightening straightening workpieces from

metals of high hardness or pre-hardened metals.

Straightening headstock is made of steel billets with a diameter

200..250mm, their working part has a spherical or cylindrical shape.

Hammerswhen editing is used to apply power

efforts in the place of editing. Depending on the physical and mechanical

properties of the workpiece and its thickness choose

various types of hammers. When editing workpieces from bar and

strip material used with square and round hammers

To edit the treated surfaces, soft hammers are used.

inserts from aluminum and its alloys or copper.

Sledgehammersare hammers of large mass (2.0 ... 5.0 kg) and

are used for straightening round and profile rolling of a large transverse

sections in those cases when the force of impact applied by a conventional bench hammer,

insufficient to straighten the deformed workpiece.

Mallet- these are hammers, the impact part of which is made of solid wood

rocks, they are ruled by sheet material of metals of high ductility.

A characteristic feature of editing with mallet is that they practically do not

  leave marks on the surface to be smoothed out.

Ironersmetal or wooden (from hardwood: beech, oak,

boxwood) are intended for straightening (smoothing) of sheet material

small thickness (up to 0.5mm). This tool is in process, like

as a rule, does not leave marks in the form of dents.

Metal editing

Editing is used in cases where it is necessary to eliminate the distortion of the shape of the workpiece - waviness, warping, dents, curvature, bulging, etc. Metal can be edited both in cold and in heated form. Heated metal heals more easily, which is also true of other types of plastic deformation, such as bending.

At home, dressing should be done on an anvil or a massive plate of steel or cast iron. The working surface of the plate should be smooth and clean. To make noise from impacts less loud, the plate should be installed on a wooden table, with which, in addition, you can level the plate so that it is in a horizontal position.

For editing, you need a special bench tool. You can not produce it with any hammer that is at hand, the metal can not only not straighten, but also get even bigger defects. The hammer should be made of soft material - lead, copper, wood or rubber. In addition, it is impossible to rule the metal with square hammer hammers: it will leave marks in the form of nicks on the surface. The hammer head must be round and polished.

In addition to hammers, wooden and metal trowels and supports are used. They are used for dressing thin sheet and strip metal. For dressing hardened parts with shaped surfaces, there are the right headstock.

It’s probably not worth recalling that straightening (straightening) of the metal must be done in the working gloves, regardless of whether the work is difficult or not, the workpiece is large or small and whether it is severely curved.

To check the curvature of the workpiece, you need to lay it on a smooth plate with that surface, which after editing should be a plane. The gap between the plate and the workpiece will show the degree of curvature that needs to be eliminated. Curved places should be noted with chalk - it is much easier to strike with a hammer than when orienting only on the curvature noticeable to the eye.

Editing 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. Hammers or a sledgehammer must be struck at the most convex places and the strength of the blows should be reduced as the bulges become smaller. You should not strike only on one side of the workpiece - the metal can bend in the opposite direction. To prevent this from happening, the workpiece needs to be turned over from time to time. For the same reason, do not hit 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 mostly similar to editing strip metal. For this purpose it is necessary to mark uneven places with chalk and place the workpiece with the bulge up, apply blows to the convex part from the edges of the bend to the middle of the bulge. When the main curvature is corrected, the impact force must be reduced and the metal rod periodically rotated around its axis in order to prevent curvature in the opposite direction.

Square metal bars must be edited in the same sequence.

Editing metal twisted in a spiralproduced by unwinding. In order to straighten the curvature, you need to clamp one end of the twisted metal into a large vice on a bench table, and the other into a manual vice. Having unwound the metal to the extent that you can control it by eye, you need to continue editing on a smooth verified plate in the usual way, controlling the curvature of the lumen.

Sheet metal editing

The complexity of editing sheet metal depends on what type of defect the sheet has - the waviness of the edge, or the bulge, or a dent in the middle of the sheet, or both at the same time (Fig. 15).

Fig. 15. Methods of editing sheet metal: a - with a deformed middle of the sheet; b - with deformed edges of the sheet; c - using a wooden trowel; g - using a metal trowel.

When editing a bulge, it is necessary to strike, starting from the edge of the sheet in the direction of the bulge (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 section, which further complicate the uneven surface. In addition, the metal in such cases experiences a very strong tensile strain. You need to do exactly the opposite: the strokes should become weaker, but more often, as the edit approaches the center of the bulge. The sheet of metal must be constantly rotated in a horizontal plane so that the impacts are evenly distributed over its entire surface.

If the sheet has not one convex section, but several, you must first reduce all the convexities into one. To do this, strike with a hammer in the spaces between them. The metal between the bulges is stretched, and they are combined into one. Then you need to continue editing in the usual way. If the middle of the sheet is flat and the edges are distorted by waves, then the sequence of strokes during 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 at its edges will disappear.

Very thin sheets cannot be straightened even with mallets made of soft material: they will not only leave dents, but can also tear thin metal.

In this case, straighteners made of metal or wood are used for dressing, with which the sheet is ironed on both sides, turning it periodically. The quality of editing can be checked using a metal ruler.

Anyone who has taken on straightening a steel sheet knows that this work is quite difficult: while straightening one bend, others appear on the sheet. However, this can be avoided and thereby greatly facilitate the work. The steel sheet needs to be laid for editing, not on a smooth plate, as is usually done, but on a lining plate with many small blunt tubercles, evenly spaced on its surface. In this case, the quality of work should increase, and the complexity should decrease. The metal under the blows of a rubber mallet will, as it were, look for its place. In this case, barely noticeable waves form on the sheet, when putty and painted, they will fill up and contribute to the fact that the putty and paint will adhere to the metal very tightly. Irregularities after coating the metal are completely invisible. The only difficulty is how to make the required lining plate. It is really difficult to make it at home: tubercles are usually obtained by cutting a large number of grooves mutually intersecting and located close to one another on a smooth slab. This can be done on a planing or milling machine, so if there is such an opportunity, it is better to use it.

Editing of hardened metal (straightening)

Soft straightening hammers are unsuitable for dressing hardened metal (straightening). A special hammer is required with a striker made of hardened metal or with a rounded narrow side. The straightening hammer can be made by yourself. To do this, in a narrow hammer striker, it is necessary to make a cut and tightly press into it a VK6 or VK8 hard alloy plate sharpened under a radius of 0.1-0.2 mm.

The hardened metal is corrected by the method from the opposite: strikes must be applied not on the convex, but on the concave part of the workpiece: it will begin to straighten due to the fact that the metal on the concave side will stretch (Fig. 16).

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

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

An insoluble task for an inexperienced locksmith is editing a flat square, in which the angle has changed and has become greater or less than 90 °. Such squares are no longer suitable for controlling right angles, and, as a rule, they are thrown away. Meanwhile, a hardened metal square can be straightened. If the right angle has decreased and is less than 90 °, then hammer blows 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 proceed to its further processing.