DE102015005522A1 - Method for producing a hollow body - Google Patents

Abstract

A method for producing a metallic hollow body, wherein the hollow body with a constant tubular, round, square, rectangular, oval, hexagonal or polygonal output cross section is subjected to a forming process by the following method steps: - The held in a receiving device hollow body is partially inductively heated; - By at least one in or on the hollow body inside and / or outside and / or attached forming tool in the partially inductively heated area, the wall thickness of the hollow body is increased in a case of use burdened area and reduced in a later use case less loaded areas and / or the cross-sectional outer dimensions of the hollow body held in the receiving device are partially reduced or partially increased by a forming tool; - And / or at the same outer dimensions of the hollow body, the inner dimensions of the hollow body in the partially inductively heated area are partially reduced or partially increased by the forming tool;

Description

The invention relates to a method for producing a hollow body in an embodiment according to the preamble of claim 1. In particular, the invention relates to a method for producing an axle tube.

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

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

• – der in einer Aufnahmeeinrichtung gehaltene Hohlkörper wird partiell induktiv erwärmt;
• – durch zumindest eine in dem oder an dem Hohlkörper innen und/oder außen ein- und/oder angebrachtes Umformwerkzeug wird in dem partiell induktiv erwärmten Bereich der 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 wird;
• – 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.

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

• - The held in a receiving device hollow body is partially heated inductively;
• - By at least one in or on the hollow body inside and / or outside and / or attached forming tool is increased in the partially inductively heated area of the wall thickness of the hollow body in a later use case more heavily loaded area and in a later use case less burdened Reduced areas and / or the cross-sectional outer dimensions of the held in the receiving device hollow body are partially reduced or partially increased by a forming tool;
• - And / or at the same outer dimensions of the hollow body, the inner dimensions of the hollow body in the partially inductively heated area are partially reduced or partially increased by the forming tool.

Thus, a method is provided with which to produce a hollow body, which may have a non-constant cross-sectional shape and / or wall thickness as needed. Due to the partial inductive heating, the hollow body can also be tempered during the manufacturing process, wherein the inductive heating may have temperatures in the hollow body to be produced, with which can be achieved in the metallic hollow body partially structural changes. It is also possible that the temperature is controlled so far by controlling the energy supply or by a subsequent tempering or quenching of the hollow body material such that a targeted heat dissipation can be done by a medium to be introduced from the inside or from the outside. As a result, an extraordinarily homogeneous structure can be partially produced in the hollow body to be produced, and overall a very homogeneous entire hollow body.

This is a hollow body to produce during the manufacturing process, which is quite individually adapted to the later to be challenged properties and functions of the hollow body. In this case, the cross-sectional shape can be adjusted accordingly, but also the wall thickness by the partial cross-sectional shape and / or the desired wall thickness after partial inductive heating in preselected areas by one or more forming tool (s) can be partially produced. In this case, 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 over the cross-section of helical hollow bodies, but also cross-sectional shapes which are rotationally symmetrical , are mirror-symmetric and / or asymmetric. Thus, torsion bars, tension rods, compression bars but also bending rods (train / pressure) can be generated. It is also possible to draw or compress this by the forming tool attached to the hollow body. As a result, the hollow body as a whole can have optimized properties for the later application.

The volume of material is adjusted during the manufacturing process the subsequent load case of the hollow body or in this respect of the workpiece and thus adjusted. At later highly loaded areas, the wall thickness of the hollow body can be increased and reduced in less-stressed areas. The cross-sectional shape of the hollow body is adjusted so that the resistance torque (axial / polar) is increased in the direction of the subsequent load. For the resistance moment can be reduced against the loading direction. By optimizing the material thickness, the total weight of the hollow body can be reduced, since the hollow body produced in the areas where appropriate load peaks occur in the subsequent application, specifically designed reinforced and For example, this increased use of material in these partial areas of the hollow body is formed by materials which originate from areas which are exposed to lower loads during later use. Overall, therefore, can be produced hollow body with lower material costs.

The hollow body according to the invention, which is produced according to the method, is explained in more detail below with the aid of drawings.

The illustrations show the state of voltage equality, where 1 shows that the voltage over the outer dimensions of the hollow body are equal under load Bieb. In this case, the outer diameter of a clamped tube decreases from the clamping to the force application point in the ratio of the bending moment.

at 2 the stresses on the inner dimension of the hollow body are equal under load. The outer diameter of a clamped tube remains constant and the wall thickness decreases from the clamp to the force application point. This results in a reduction of the inner diameter of the power instruction up to the clamping. In addition, the stresses on the outer and on the inner dimension of the hollow body can be equal under load. It should be mentioned by way of example that an outer diameter of a clamped tube decreases in proportion to the bending moment, wherein the wall thickness is reduced in order to keep the tension over the outer as well as the inner diameter the same.

3 shows that a stiffening can also be provided.

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

In this case, a plurality of cross-sectional shapes can be formed over the hollow body length, as this 4 shows, in which the ends are round in cross section and the larger central area square.

It is also possible that the hollow body to be produced is reinforced at areas where forces are introduced or to generate these force application points. Show this 5 and 6 , Where force application points and connection points to other components burdened many times higher or weakened at the interface, such. B. at a weld or at a screw hole. At these points, the hollow body can be reinforced by targeted inductive heating and subsequent forming by the wall thickness is increased at a weld, the diameter is increased at a weld and / or the wall thickness is increased at a screw hole.

Particularly advantageous can be generated by the method according to the invention, a hollow body to which for later use other parts as in the case of the aforementioned axle tube for a commercial vehicle handlebar and / or spring are to be connected, pads for the handlebar and / or spring can be generated by the granting Verfahrung. This is shown by the 7 and 8th , The connection surfaces may be located explicitly closer to the center of the axle or farther away from the center of the axle, as shown in the first representation, in which a shaping and, on the other hand, a constriction are provided there. This 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 thus the required installation space, for example, of an axle body with a part connected to it on a commercial vehicle is reduced. Furthermore, the diameter can be increased on a flange surface in order to be able to bridge more space.

During the manufacturing process, the hollow body is partially heated by induction. The heated areas have lower strength and can be formed with less force. If the hollow body is heated differently over the cross section, the cross section deforms accordingly when applying a forming force to the hot areas more than to the cooler ones. The hollow body can be partially heated both over the length, as well as over the cross section. In addition to the hot forming, the inductive heating is still the heat treatment of the hollow body, so that the temperature of the workpiece is increased so far that can be achieved within the metal microstructure changes (temper, temper). 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 rotiert (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 rotiert (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 an optimized partial inductive heating, the heat treatment process can be designed differently, for example by the design of the induction coils. This is in 11 to 18 shown.

• - 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 thereby rotated ( 12 )
• - Fixed hollow body, induction coil (s) is / are moved around the hollow body ( 13 )
• - Fixed hollow body, induction coil (s) is / are linearly moved around the hollow body while rotating ( fourteen )
• - Rotating hollow body, which does not move linearly, induction coil (s) are moved linearly around the hollow body ( 15 )
• - Hollow body and induction coil (s) are moved linearly at different speeds, directions can be rectified or counter-aligned ( 16 )
• - Internal induction coil ( 17 )
• - The distance of the induction coil (s) to the body surface may be constant or inconstant (a constant distance of a coil to the body surface ensures even heat distribution over a constant cross-section). In this case, the coils can be moved radially. ( 18 )
• - When using multiple coil elements, the rotation of the tube and / or the movement of the coil elements may be necessary to produce 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. In this case, an axial tensile force can be applied, which causes the warmer areas stretched and the cross-sectional area is reduced. The application of an axial compressive force causes the warmer portions to be compressed and the cross-sectional area to increase. By applying a torsional moment on the hollow body can be generated in the warmer area aligned to a "helical shape" contour. This shows the 19 ,

In addition, by applying tensile and compressive forces at an angle in the longitudinal plane, bending in the warmer region can be produced, as is 20 shows.

In this case, axial forces can be introduced via the hollow body ends. In addition, it is possible to attach a body to the hollow body end, which seals the interior, so that an internal pressure can be generated there with a medium as 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 hollow body causes a reduction in the outer diameter. The application of a radial force away from the axial center causes the hollow body to expand. The radial force from the outside with rollers and / or fittings as 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 axial forces can also be introduced simultaneously via a cone whose largest diameter is greater than the inner diameter of the hollow body. A medium which is pressed into the hollow body generates a radial force away from the center of the axle due to the internal pressure. By a negative pressure in the hollow body, a radial force is generated in the direction of the center of the axle. Radial forces can be generated from the inside by combining a medium and an expandable mandrel. The media used can generally liquids, emulsions, granules and / or ceramic balls use. Furthermore, a shape can be placed around the hollow body or held against the hollow body, to which the heated areas by means of the internal pressure or an axial or radial force is applied.

All forces can be applied at the same time, so that their influences are superimposed, such as pressure from the inside and in addition a compression, whereby the outer contour increases while maintaining the wall thickness.

The material of the hollow body can be cooled again immediately after the forming, so that the shape remains and on the new dimensions further forces can be applied.

By tempering the material of the hollow body, the strength is increased. Thereafter, higher voltages can be allowed. Thus, less material can be used at the same load. This reduces weight and material costs. The hollow body can also be hardened during the forming process by a heat removal from the outside by a medium is brought into contact with the surface, for example by spraying water or the hollow body is poured over with water. Alternatively or at the same time, targeted heat removal by a medium in the interior can take place, and this medium can also be that used for a forming process. The heat dissipation can of course also be done from the inside by another medium for forming. Overall, a homogeneous structure can thus be generated. A subsequent tempering of the material of the hollow body is of course also possible, as well as a controlled cooling.

Claims (26)

A method for producing a metallic hollow body, wherein the hollow body with a constant tubular, round, square, rectangular, oval, hexagonal or polygonal output cross-section is subjected to a forming process, characterized by the following method steps: - The held in a receiving device hollow body is partially heated inductively; - By at least one in or on the hollow body inside and / or outside and / or attached forming tool in the partially inductively heated area, the wall thickness of the hollow body is increased in a case of use burdened area and reduced in a later use case less loaded areas and / or the cross-sectional outer dimensions of the hollow body held in the receiving device are partially reduced or partially increased by a forming tool; - And / or at the same outer dimensions of the hollow body, the inner dimensions of the hollow body in the partially inductively heated area are partially reduced or partially increased by the forming tool; A method according to claim 1, characterized in that the held in the device hollow body is strengthened after the partial inductive heating in terms of its wall thickness in areas where forces are introduced later. A method according to claim 1 or 2, characterized in that reduced or increased connection surfaces are produced on the hollow body held in the device after the induction heating via a forming tool to connect components of assemblies to be mounted. A method according to claim 3, characterized in that the connection surfaces are formed by the forming of tools after the inductive heating, that they have a rotationally symmetrical, a mirror-symmetrical and / or an asymmetric cross-sectional shape. Method according to one of claims 1 to 4, characterized in that the hollow body to be machined consists of a metallically conductive material. Method according to one of claims 1 to 5, characterized in that the hollow body consists of a steel, a tempering steel or a spring steel. Method according to one of claims 1 to 6, characterized in that the hollow body is heated differently inductively across the cross section. A method according to claim 7, characterized in that the held in the device hollow body is partially heated differently over its length but also over its cross section. Method according to one of claims 1 to 8, characterized in that the hollow body held in the device is heated so inductively that set in its metallic material structural changes. Method according to one of claims 1 to 9, characterized in that the held in the device hollow body is stretched by the forming tool with a reduction in its cross-sectional area. Method according to one of claims 1 to 10, characterized in that the held in the device hollow body after its inductive partial heating, the heated areas are compressed by the forming tool. Method according to one of claims 1 to 11, characterized in that on the held in the device hollow body by the forming a torsional moment is generated, so that in the clamped hollow body in the heated areas a helical shape is generated. Method according to one of claims 1 to 12, characterized in that by applying tensile or compressive forces on the hollow body held in the device at a angle in the longitudinal plane, a bend in the inductively partially heated region of the hollow body is generated. Method according to one of claims 1 to 13, characterized in that in the interior of the device held in the hollow body, a pressure in the hollow body is applied. Method according to one of claims 1 to 14, 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 claims 1 to 15, characterized in that over the held in the device hollow body in the partially inductively heated region, an inner and / or outer shape is slipped or stopped, to which a partially inductively heated area using a Pressure in the cavity of the held in the device hollow body applies. Method according to one of claims 1 to 16, characterized in that in the device held in the hollow body, an expandable mandrel for expanding the hollow body is introduced in a partially inductively heated area. Method according to one of claims 1 to 17, characterized in that the hollow body is guided linearly through the magnetic field of a fixed induction coil. Method according to one of claims 1 to 18, characterized in that the hollow body is guided by the magnetic field of a fixed induction coil and is thereby set in a rotational movement. Method according to one of claims 1 to 19, characterized in that an induction coil is moved linearly around the stationary hollow body and thereby rotates. Method according to one of claims 1 to 20, characterized in that the hollow body rotates and does not move linearly and an induction coil is moved linearly around the hollow body. Method according to one of claims 1 to 21, characterized in that the hollow body and one or more induction coil (s) are moved linearly at different speeds, wherein the linear movement directions of the hollow body and induction coil (s) are rectified or directed. Method according to one of claims 1 to 22, characterized in that an induction coil is provided for partial heating within the Hohlköpers. A method according to claim 23, characterized in that the internal induction coil for partial heating of the hollow body is designed to be linearly movable. Method according to one of claims 1 to 24, characterized in that the distance between the hollow body surrounding the induction coil for partial heating of the hollow body to the body surface has a constant or an inkonstanten distance. Method according to one of claims 1 to 25, characterized in that the hollow body is quenched and / or annealed after the partial heating.

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