DE102015005522B4 - Method for producing a metallic hollow body - Google Patents

Abstract

Method for producing a metallic hollow body, wherein the hollow body with a constant tubular, round, square, rectangular, oval, hexagonal or polygonal starting cross-section is subjected to a forming process with the following process steps: - the hollow body held in a receiving device is partially inductively heated; - by at least one In the or on the hollow body inside and / or outside a and / or attached forming tool in the partially inductively heated area, the wall thickness of the hollow body is increased in an area loaded in the case of use and reduced in an area less loaded in the later case of use and / or the External cross-sectional dimensions of the hollow body held in the receiving device are partially reduced or partially increased by a forming tool; The forming tool is partially reduced or partially increased; - the hollow body held in the device is heated inductively to varying degrees over its length and across its cross-section; - the hollow body is guided linearly through the magnetic field of a fixed induction coil, or fixed induction coil and thereby set in a rotational movement, or- an induction coil is moved linearly around the immovable hollow body and rotates, or- the hollow body rotates and does not move linearly and an induction coil is moved linearly around the hollow body, or- the hollow body and one or several induction coil (s) move linearly at different speeds, the direction of linear movement of the hollow body and induction coil (s) being rectified or counter-directed, or - inside the hollow body, an induction coil is provided for partial heating, which is used for partial heating of the Hoh - the hollow body held in the device is reinforced with regard to its wall thickness in areas where forces are later introduced after the partial inductive heating; or raised connection surfaces are generated in order to connect components of assemblies to be assembled; - the connection surfaces are formed by the deformation of tools after inductive heating in such a way that they have a rotationally symmetrical, mirror-symmetrical and / or asymmetrical cross-sectional shape.

Description

The invention relates to a method for producing a metallic hollow body. In particular, the invention relates to a method for producing a metallic axle tube.

Metallic axle tubes of conventional design are generally known and can have a wide variety of dimensions. These are used, for example, when used in commercial vehicles as vehicle axles that are connected to the chassis via suitable connections and springs and / or links. For this purpose, the axle beam must be given the appropriate strength in order to withstand the everyday demands in use of a commercial vehicle. This is usually done by providing the axle body with tie rods and connecting blocks in order to attach the corresponding links or springs and then to connect the overall package to the vehicle chassis. This requires an axle body with correspondingly thick wall thicknesses in order to meet the strength requirements.

From the not pre-published DE 10 2014 014 818 A1 a method for producing a metallic hollow body is known in which a hollow body in different cross-sectional variants can be held in a receiving device in order to be partially inductively heated there. The external cross-sectional dimensions of the hollow body held in the receiving device are partially reduced or partially increased by a forming tool. With such a method, however, individual requirements of a metallic hollow body with regard to its cross-sectional geometry, its longitudinal geometry and its special strength requirements in partial areas of the hollow body cannot be taken into account.

From the DE 10 2007 053 551 A1 a method is known with which cross-sectional changes are to be made on hollow parts. Here, too, the hollow part should be partially heated and axially upset. The upsetting can take place outwards or inwards. Here, too, special requirements for the design of the hollow part in the longitudinal direction or in its cross-sectional design cannot be met.

From the DE 10 2013 209 948 A1 a method for processing or reshaping heavy-duty components in motor vehicles is known in order to avoid the risk of cracking during reshaping, in particular when upsetting a heavy-duty, tubular structural component made of high-strength or ultra-high-strength steel. For this purpose, a region of the tubular structural component that is to be upset is to be heated before the deformation, the heating of the tubular structural component being limited to the region of the tubular structural component that is to be upset. The area to be upset should be heated with the help of an inductor. However, this method and the heating are only limited to one area to be upset, so that no changes can be made elsewhere.

From US 2007/0 062 241 A1 a method for producing metallic hollow parts is known, in which different wall thicknesses and different diameters can be realized. The wall thickness of the hollow body can also be increased or decreased in certain areas. From the US 6 322 645 B1 a method for producing an elongated metallic body is known which has a certain external configuration. Inner areas can be provided that are encased by a coil in order to introduce induction heat into the part.

From the EP 2 687 392 A1 A method of manufacturing a pipe stabilizer for an automobile is known, wherein a pipe with an original outer diameter is reduced by a kneading process. This should make it possible to manufacture one-piece tube stabilizer halves of the same material.

From the DE 10 2010 027 093 A1 a method for producing a metallic hollow profile is known, the hollow profile being introduced in a deformation direction which has a guide device, a heating device, a feed device and a guide arm. Before the deformation, the hollow profile of the heating device is locally heated in a continuous process, after which the hollow profile is pushed through the heating device by means of the feed device. Behind the heating device, the hollow profile is guided by guide arms, the guide speed of the guide arm being varied to change the wall thickness of the hollow profile in the heat-affected zone of the heating device, so that at least a length section of the hollow profile is compressed or elongated.

From the DE 10 2011 086 125 B4 a pipe thickening process is known. This method is therefore limited to metallic hollow bodies in pipes with a round cross-section.

From the DE 10 2010 015 835 A1 a method for the machine production of cylindrical workpieces is known, in which a workpiece is axially upset in a tool press under the action of a press ram. The upsetting process is initiated with at least a pulse-like pressing force, which is greatly increased compared to the normal pressing force that follows. In order to This method is also only limited to the machine production of workpieces in cylinder shape.

From the DE 102 40 876 A1 a method for forming a metal element is known by means of a shaping die, in which the wall of the metal element is expanded via an internal pressure that is built up in the cavity of the metal element, in order then to bring it into contact with the shaping die in order to produce the corresponding metal element to get into shape. In this way, reshaping of a metallic hollow body cannot be achieved individually and at certain geometric points.

It is the object of the present invention to provide a method with which a metallic hollow body such as an axle tube can be produced with optimized strength properties and with such an optimized geometry that it can be installed more easily during subsequent assembly.

• - der in einer Aufnahmeeinrichtung gehaltene Hohlkörper wird partiell induktiv erwärmt;
• - durch zumindest ein in dem oder an dem Hohlkörper innen und/oder außen ein- und/oder angebrachtes Umformwerkzeug wird in dem partiell induktiv erwärmten Bereich die Wanddicke des Hohlkörpers in einem im späteren Verwendungsfall stärker belasteten Bereich erhöht und in einem im späteren Verwendungsfall weniger belasteten Bereichen verringert und/oder die Querschnittsaußenabmessungen des in der Aufnahmevorrichtung gehaltenen Hohlkörpers werden durch ein Umformwerkzeug partiell reduziert oder partiell erhöht;
• - und/oder bei gleichen Außenabmessungen des Hohlkörpers werden die Innenabmessungen des Hohlkörpers im partiell induktiv erwärmten Bereich durch das Umformwerkzeug partiell reduziert oder partiell erhöht;
• - der in der Vorrichtung gehaltene Hohlkörper wird über seine Länge und über seinen Querschnitt partiell unterschiedlich induktiv erwärmt;
• - der Hohlkörper wird linear durch das Magnetfeld einer festen Induktionsspule geführt, oder
• - der Hohlkörper wird durch das Magnetfeld einer feststehenden Induktionsspule geführt und dabei in eine Rotationsbewegung versetzt, oder
• - eine Induktionsspule wird linear um den unbeweglichen Hohlkörper bewegt und rotiert dabei, oder
• - der Hohlkörper rotiert und verfährt nicht linear und eine Induktionsspule wird linear um den Hohlkörper bewegt, oder
• - der Hohlkörper und eine oder mehrere Induktionsspule(n) verfahren mit unterschiedlichen Geschwindigkeiten linear, wobei die Linearbewegungsrichtung von Hohlkörper und Induktionsspule(n) gleichgerichtet oder gegengerichtet sind, oder
• - innerhalb des Hohlkörpers ist eine Induktionsspule zur partiellen Erwärmung vorgesehen, die zur partiellen Erwärmung des Hohlkörpers linear beweglich ausgebildet ist;
• - der in der Vorrichtung gehaltene Hohlkörper wird nach der partiellen induktiven Erwärmung hinsichtlich seiner Wandstärke in Bereichen verstärkt, an denen später Kräfte eingeleitet werden;
• - an dem in der Vorrichtung gehaltenen Hohlkörper werden nach der induktiven Erwärmung über ein Umformwerkzeug reduzierte oder erhöhte Anschlussflächen erzeugt, um Komponenten von zu montierenden Baugruppen anzubinden;
• - die Anschlussflächen werden durch das Umformen von Werkzeug derart nach der induktiven Erwärmung angeformt, dass diese eine rotationssymmetrische, eine spiegelsymmetrische und/oder eine asymmetrische Querschnittsform aufweisen.

To solve this problem, the method for producing a metallic hollow body is characterized by the following method steps:

• - The hollow body held in a receiving device is partially inductively heated;
• - By at least one in or on the hollow body inside and / or attached to the inside and / or outside of the forming tool, the wall thickness of the hollow body is increased in the partially inductively heated area in a more heavily loaded area in a later use case and less loaded in a later use case Areas reduced and / or the external cross-sectional dimensions of the hollow body held in the receiving device are partially reduced or partially increased by a forming tool;
• - And / or with the same external dimensions of the hollow body, the internal dimensions of the hollow body in the partially inductively heated area are partially reduced or partially increased by the forming tool;
• - The hollow body held in the device is partially differently heated inductively over its length and over its cross section;
• - The hollow body is guided linearly through the magnetic field of a fixed induction coil, or
• - The hollow body is guided through the magnetic field of a stationary induction coil and set in a rotational movement, or
• - An induction coil is moved linearly around the immovable hollow body and rotates in the process, or
• - the hollow body rotates and does not move linearly and an induction coil is moved linearly around the hollow body, or
• the hollow body and one or more induction coil (s) move linearly at different speeds, the linear direction of movement of the hollow body and induction coil (s) being rectified or counter-directed, or
• - Within the hollow body, an induction coil for partial heating is provided, which is designed to be linearly movable for partial heating of the hollow body;
• - After the partial inductive heating, the hollow body held in the device is reinforced with regard to its wall thickness in areas where forces are later introduced;
• - On the hollow body held in the device, reduced or increased connection surfaces are produced after the inductive heating via a forming tool in order to connect components of assemblies to be assembled;
• - The connection surfaces are formed by the deformation of the tool after the inductive heating in such a way that they have a rotationally symmetrical, a mirror symmetrical and / or an asymmetrical cross-sectional shape.

A method is thus made available with which a hollow body can be produced which, depending on requirements, can have a non-constant cross-sectional shape and / or wall thickness. Due to the partial inductive heating, the hollow body can also be remunerated during the manufacturing process, wherein the inductive heating can have temperatures in the hollow body to be produced, with which structural changes can be partially achieved in the metallic hollow body. It is also possible that the temperature is controlled by controlling the energy supply or by subsequent tempering or quenching of the hollow body material in such a way that a targeted heat dissipation can take place through a medium to be introduced from the inside or from the outside. As a result, an extremely homogeneous structure can be produced partially in the hollow body to be produced and, overall, also a very homogeneous entire hollow body.

In this way, a hollow body is to be produced during the manufacturing process, which is to be adapted quite individually to the properties and functions of the hollow body that are to be required later. The cross-sectional shape can be adapted accordingly, but also the wall thickness by After the partial inductive heating in preselectable areas by one or more forming tool (s), the desired cross-sectional shape and / or the desired wall thickness can be partially produced. Various hollow bodies can be produced, for example axle tubes, round hollow bodies, square hollow bodies, rectangular hollow bodies, oval hollow bodies, hexagonal hollow bodies (hexagons), polygonal hollow bodies (polygons), hollow bodies with different wall thicknesses across the cross-section, helical hollow bodies, but also cross-sectional shapes that are rotationally symmetrical, mirror symmetrical and / or asymmetrical. In this way, torsion bars, tension bars, compression bars but also bending bars (tension / compression) can be created. It is also possible to pull or compress it through the forming tool attached to the hollow body. In this way, the hollow body can overall have properties that are optimized for later use.

During the manufacturing process, the material volume is adjusted accordingly and thus adapted to the subsequent load case of the hollow body or, in this respect, of the workpiece. In later highly stressed areas, the wall thickness of the hollow body can be increased and in less stressed areas it can be reduced. The cross-sectional shape of the hollow body is adapted in such a way that the moment of resistance (axial / polar) is increased in the direction of the subsequent load. For this, the moment of resistance against the direction of load can be reduced. By optimizing the material thickness, the total weight of the hollow body can be reduced, since the hollow body produced is specifically reinforced in the areas where corresponding load peaks occur in later use and, for example, this increased material input is formed by materials in these partial areas of the hollow body, that come from areas that are exposed to lower loads in later use. Overall, the hollow body to be produced can therefore be produced with lower material costs.

In the following, drawing representations according to the 1 until 20th the hollow body according to the invention, which is produced by the method, explained in more detail.

The representations show the state of voltage equality, where 1 shows that the stress over the outer dimensions of the hollow body is the same under bending load. The outside diameter of a clamped pipe decreases from the clamping to the point of force application in the ratio of the bending moment.

at 2 the stresses over the inner dimension of the hollow body are the same under load. The outside diameter of a clamped pipe remains constant and the wall thickness decreases from the clamping to the point where the force is applied. This results in a reduction in the inside diameter from the force instruction to the clamping. In addition, the stresses across the outer and inner dimensions of the hollow body can be the same under load. It should be mentioned by way of example that the outer diameter of a clamped pipe decreases in proportion to the bending moment, the wall thickness being reduced in order to keep the tension across the outer and inner diameter the same.

3 shows that stiffening can also be provided.

The moment of resistance of the hollow body is increased in the direction of the introduction of force. In this figure, a clamped rectangular tube is subjected to bending loads from above. The cross-section is narrow and high and the wall thickness of the top / bottom is greater than that of the side legs.

Several cross-sectional shapes can also be formed over the length of the hollow body, like this 4th shows, in which the ends are made round in cross-section and the larger central area is square.

It is also possible that the hollow body to be produced is reinforced in areas where forces are introduced or in order to produce these force introduction points. Show this 5 and 6th , whereby force introduction points and connection points to other components are often more heavily loaded or weakened at the interface, such. B. on a weld seam or on a screw hole. At these points, the hollow body can be reinforced by targeted inductive heating and subsequent reshaping by increasing the wall thickness at a weld seam, increasing the diameter at a weld seam and / or increasing the wall thickness at a screw hole.

With the method according to the invention, it is particularly advantageous to produce a hollow body to which further parts are to be attached for later use, such as in the case of the aforementioned axle tube for a commercial vehicle, handlebars and / or springs, or connection surfaces for the handlebars and / or springs can be produced by the method according to the invention. This is what they show 7th and 8th . The connection surfaces can explicitly be closer to the center of the axis or further away from the center of the axis, as the first next illustration shows, in that a formation and, on the other hand, a constriction are provided there. These Cross-sectional shape can be rotationally symmetrical, mirror-symmetrical and / or asymmetrical. To reduce installation space, for example, the diameter can be partially reduced so that a component connected there is lower and the required installation space, for example an axle body with a part connected to it on a commercial vehicle, is reduced. Furthermore, the diameter on a flange surface can be increased in order to be able to bridge more installation space.

During the manufacturing process, the hollow body is partially heated by induction. The heated areas have a lower strength and can be deformed with less force. If the hollow body is heated differently over the cross section, the cross section deforms accordingly more in the warm areas than in the cooler areas when a deformation force is applied. The hollow body is partially heated both over its length and its cross-section. In addition to hot forming, inductive heating is also used for heat treatment of the hollow body, so that the temperature of the workpiece is increased so that structural changes can be achieved within the metal structure (tempering, tempering). Show this 9 and 10 .

• - Feststehende Induktionsspule(n), Hohlkörper wird linear durch das Magnetfeld bewegt (11).
• - Feststehende Induktionsspule(n), Hohlkörper wird linear durch das Magnetfeld bewegt und dabei rotierend bewegt (12)
• - Feststehender Hohlkörper, Induktionsspule(n) wird/werden um den Hohlkörper bewegt (13)
• - Feststehender Hohlkörper, Induktionsspule(n) wird/werden linear um den Hohlkörper bewegt und dabei rotierend bewegt (14)
• - Rotierender Hohlkörper, der nicht linear verfährt, Induktionsspule(n) werden linear um den Hohlkörper bewegt (15)
• - Hohlkörper und Induktionsspule(n) werden mit unterschiedlichen Geschwindigkeiten linear verfahren, Richtungen können gleichgerichtet oder gegengerichtet sein (16)
• - Innenliegende Induktionsspule (17)
• - Abstand der Induktionsspule(n) zur Körperoberfläche kann konstant oder inkonstant sein (ein konstanter Abstand einer Spule zur Körperoberfläche sorgt für eine gleichmäßige Wärmeverteilung über einen konstanten Querschnitt). Dabei können auch die Spulen radial bewegt werden. (18)
• - Beim Einsatz mehrerer Spulenelemente kann das Rotieren des Rohres und/oder die Bewegung der Spulenelemente vonnöten sein um eine gleichmäßige Wärmeinduktion über den Querschnitt zu erzeugen

For optimized partial inductive heating, the heat treatment process can be designed differently, for example through the design of the induction coils. This is in 11 until 18th shown as below:

• - Fixed induction coil (s), hollow body is moved linearly through the magnetic field ( 11 ).
• - Fixed induction coil (s), hollow body is moved linearly through the magnetic field and rotated in the process ( 12th )
• - Fixed hollow body, induction coil (s) is / are moved around the hollow body ( 13th )
• - Fixed hollow body, induction coil (s) is / are moved linearly around the hollow body while rotating ( 14th )
• - Rotating hollow body that does not move linearly, induction coil (s) are moved linearly around the hollow body ( 15th )
• - Hollow bodies and induction coil (s) are moved linearly at different speeds, directions can be in the same direction or in opposite directions ( 16 )
• - Internal induction coil ( 17th )
• - The distance between the induction coil (s) and the body surface can be constant or inconstant (a constant distance between a coil and the body surface ensures an even distribution of heat over a constant cross-section). The coils can also be moved radially. ( 18th )
• - When using several coil elements, the rotation of the tube and / or the movement of the coil elements may be necessary in order to generate a uniform heat induction over the cross-section

With the application of an axial force, it is possible to change the contour and the wall thickness of the hollow body. An axial tensile force can be applied, which has the effect that the warmer areas are stretched and the cross-sectional area is reduced. The application of an axial compressive force causes the warmer areas to be compressed and the cross-sectional area to increase. By applying a torsional moment to the hollow body, a contour adapted to a "helical shape" can be generated in the warmer area. This shows the 19th .

By applying tensile and compressive forces at an angle in the longitudinal plane, a bend can also be created in the warmer area, like this 20th shows.

Axial forces can be introduced via the ends of the hollow body. In addition, it is possible to attach a body to the end of the hollow body which seals the interior space so that an internal pressure can be generated there with a medium as a forming tool. The medium can be introduced through the open end of the hollow body during the manufacturing process.

By applying a radial and / or axial force, the diameter and thus the outer contour of the hollow body can be changed. The application of a radial force in the direction of the center of the axis of the hollow body causes the outer diameter to be reduced. The application of a radial force away from the center of the axis causes the hollow body to expand. The radial force from the outside with rollers and / or shaped pieces as a forming tool is applied after the partial inductive heating. A radial force from the inside can be generated by means of an expandable mandrel. Radial forces and also axial forces can also be introduced simultaneously via a cone, the largest diameter of which is larger than the inner diameter of the hollow body. A medium that is pressed into the hollow body generates a radial force away from the center of the axis due to the internal pressure. A negative pressure in the hollow body generates a radial force in the direction of the center of the axis. Radial forces can be generated from the inside by combining a medium and an expandable mandrel. Liquids, emulsions, granules and / or ceramic balls can generally be used as media. Furthermore, a shape can be placed around the hollow body or held against the hollow body, to which the heated areas are applied with the aid of the internal pressure or an axial or radial force.

All forces can be applied at the same time, so that their influences are superimposed, such as pressure from the inside and additional upsetting, which increases the outer contour while maintaining the wall thickness.

The material of the hollow body can be cooled down again immediately after the deformation, so that the shape is retained and further forces can be applied to the new dimensions.

By tempering the material of the hollow body, the strength is increased. Thereafter, higher voltages can be allowed. This means that less material can be used with the same load. This reduces weight and material costs. The hollow body can also be hardened during the forming process by dissipating heat from the outside by bringing a medium into contact with the surface, for example by spraying water or pouring water over the hollow body. Alternatively or at the same time, targeted heat dissipation can also take place through a medium in the interior, wherein this medium can also be that which is used for a forming process. The heat can of course also be dissipated from the inside through another medium for forming. Overall, a homogeneous structure can thus be created. Subsequent tempering of the material of the hollow body is of course also possible, as is controlled cooling.

Claims (14)

Method for producing a metallic hollow body, wherein the hollow body with a constant tubular, round, square, rectangular, oval, hexagonal or polygonal starting cross-section is subjected to a forming process with the following process steps: - The hollow body held in a receiving device is partially inductively heated; - By at least one in or on the hollow body inside and / or attached to the inside and / or outside of the forming tool, the wall thickness of the hollow body is increased in the partially inductively heated area in a stressed area in the case of use and reduced in an area less stressed in the later use case and / or the external cross-sectional dimensions of the hollow body held in the receiving device are partially reduced or partially increased by a forming tool; - And / or with the same external dimensions of the hollow body, the internal dimensions of the hollow body in the partially inductively heated area are partially reduced or partially increased by the forming tool; - The hollow body held in the device is partially differently heated inductively over its length and over its cross section; - The hollow body is guided linearly through the magnetic field of a fixed induction coil, or - The hollow body is guided through the magnetic field of a stationary induction coil and set in a rotational movement, or - An induction coil is moved linearly around the immovable hollow body and rotates in the process, or - the hollow body rotates and does not move linearly and an induction coil is moved linearly around the hollow body, or the hollow body and one or more induction coil (s) move linearly at different speeds, the linear movement direction of the hollow body and induction coil (s) being rectified or counter-directed, or - Within the hollow body, an induction coil for partial heating is provided, which is designed to be linearly movable for partial heating of the hollow body; - After the partial inductive heating, the hollow body held in the device is reinforced with regard to its wall thickness in areas where forces are later introduced; - On the hollow body held in the device, reduced or increased connection surfaces are produced after the inductive heating via a forming tool in order to connect components of assemblies to be assembled; - The connection surfaces are formed by the deformation of the tool after the inductive heating in such a way that they have a rotationally symmetrical, a mirror symmetrical and / or an asymmetrical cross-sectional shape. Procedure according to Claim 1 , characterized in that the hollow body to be processed consists of a metallically conductive material. Method according to one of the Claims 1 or 2 , characterized in that the hollow body consists of a steel, a quenched and tempered steel or a spring steel. Procedure according to Claim 3 , characterized in that the hollow body held in the device is inductively heated in such a way that structural changes occur in its metallic material. Method according to one of the Claims 1 until 4th , characterized in that the hollow body held in the device is stretched by the forming tool with a reduction in its cross-sectional area. Method according to one of the Claims 1 until 5 , characterized in that the hollow body held in the device, after its inductive partial heating, the heated areas are compressed by the forming tool. Method according to one of the Claims 1 until 6th , characterized in that a torsional moment is generated on the hollow body held in the device by the forming tool, so that a helical shape is generated in the clamped hollow body in the heated areas. Method according to one of the Claims 1 until 7th , characterized in that the application of tensile or compressive forces to the hollow body held in the device at an angle in the longitudinal plane produces a bend in the inductively partially heated area of the hollow body. Method according to one of the Claims 1 until 8th , characterized in that a pressure is applied in the hollow body inside the hollow body held in the device. Method according to one of the Claims 1 until 9 , characterized in that the hollow body held in the device is exposed to a liquid, an emulsion, a granulate and / or ceramic balls for forming in the inductively heated area. Method according to one of the Claims 1 until 10 , characterized in that an inner and / or outer shape is placed or held over the hollow body held in the device in the partially inductively heated area, to which a partially inductively heated area attaches with the aid of a pressure in the cavity of the hollow body held in the device applies. Method according to one of the Claims 1 until 11 , characterized in that an expandable mandrel for expanding the hollow body in a partially inductively heated area is introduced into the hollow body held in the device. Procedure according to Claim 1 , characterized in that the distance between the induction coil surrounding the hollow body for partial heating of the hollow body and its body surface has a constant or an inconstant distance. Procedure according to Claim 1 , characterized in that the hollow body is quenched and / or tempered after the partial heating.

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