DE102007004030B3 - Hardening method for vehicle axles comprises heating them to austenite temperature using contact electrodes, after which they are quenched, ends of axle being cooled to keep them below austenite temperature - Google Patents

Abstract

Hardening method for vehicle axles (10) comprises heating them to the austenite temperature using contact electrodes (40, 50), after which they are quenched. The ends of the axle are cooled to keep them below the austenite temperature. An independent claim is included for use of apparatus comprising two contact electrodes, a feeder for fitting the axle between the electrodes, a current source, a cooling system for the ends of the axle and a unit for removing the axle.

Description

The The invention relates to a method for hardening vehicle axles, in particular Automotive axles, as well as the use of a device for curing Vehicle axles according to the preamble of claim 1.

in the Vehicle area will have different requirements on the properties of components that depend on the function of the component. So there is a need for axes for Automobiles available to provide the mechanically stable and preferably also possible are easy. To achieve mechanical stability the axles are hardened. The end parts are made by annealing softened again and welded to the wheel carriers to be fastened to it.

To The state of the art is hardening causes the vehicle axles by induction heating. When induction hardening is the one to be hardened Axis heated by an induction coil, which covers the entire axis heats until the austenitic temperature is reached. After that the axle is quenched in a water basin. After this cure is the axis over her entire length hardened.

This However, the method has many disadvantages. It has a bad one Efficiency.

It there is a risk of a spark gap in the area of the unclear points of contact in the field of material doubling (filling), with the risk of Violation of the inner surface and thus the danger of a crack source. This is especially problematic if, for example, a heavily dynamically loaded rear axle of a Car is to be produced, which must be particularly stable.

By the poor coupling of the filled areas arise long compensation times with lower power. To be in production the Cycle time of 30 seconds is a very strong one Inductor required, with the help of which are heated quickly can. The methods of curing have been carried out so far, for example, in a continuous roller hearth furnace. This Oven, however, is very expensive to buy and consumes a lot lots of space. Typical dimensions are 15m × 3m. It is not possible the To turn the oven on and off quickly, but rather requires it about five hours.

The Tails the axle, which with the wheel carrier will continue to be joined in a separate step annealed so that they are soft enough to be welded, what An additional Represents step.

From the German publication DE 10 2006 018 382 A1 Further, a shock absorbing vehicle carrier is known, which is manufactured with a heat treatment device having a pair of current-applying means for applying electricity directly to the vehicle carrier body. The application of the current hardens the component. Furthermore, means for quenching the carrier body are provided.

It It is the object of the invention to provide a method for curing make, which is cheaper as well as simpler and takes less time.

Especially a method is to be provided in which a vehicle axle can be produced in a process step that in the middle Part hardened and at the ends, which are welded to the wheel carriers which is enough to be easily welded can.

outgoing From the preamble of claim 1, the object according to the invention thereby solved that the vehicle axle by inclusion in at least two contact electrodes heated by conduction is heated, whereby the central region of the axis is heated and the two provided for the weld end pieces during the conductive heating cooled so far be that they do not have the austenitic temperature of the axle material reach and therefore do not harden.

With the method according to the invention or this use according to the invention the conductive hardening can Vehicle axles are produced in a process step, the be welded directly and without further follow-up with their ends with the wheel carriers can. This allows a short production time and lower unit costs during production be achieved. The disadvantages indicated in the prior art will be avoided.

Farther this method has the lowest energy consumption, since it is the converts electrical energy into heat directly in the workpiece.

advantageous Further developments of the invention are the subject of the dependent claims and are explained by way of example with reference to the figures.

From the drawings shows:

1 a vehicle axle to be manufactured in the exemplary form of a curved hollow axle and a device for its hardening and

2 an inventively hardened hollow axle.

in the The following is the method of the invention in its general form.

According to the invention is a Vehicle axle, in particular hardened an automobile axle.

It can diverse, preferably tubular axes hardened become. The term axis also includes forms that deviate from the bar shape, In particular, all forms are used which are used for axles of automobiles become.

The vehicle axles are - for example, by a production robot - with at least two contact electrodes 40 . 50 brought into contact. Preferably, the contact electrodes 40 . 50 designed to accommodate the ends of the axles. The nature and design of the contact electrodes 40 . 50 is known in the art. The special design may vary depending on the individual case. By way of example, but not limitation, the contact electrodes 40 . 50 at the ends 20 . 30 the axis 10 be attached.

By Applying a current will cause the axis to at least austenitic temperature heated. The austenitic temperature is different for each material and is known in the art. Typical materials for the axle are carbon or boron-alloyed steel.

According to the invention Axis at the ends during the supply of water cooled so far that at the ends of the Austenitemperatur is not reached or that the ends are cold stay. You can do this cooling elements be used, which is the heat dissipate. these can for example, be operated with water or piezoelectric. It is aimed at a temperature which is below the Austittemperatur lies. Are the contact electrodes at the end of the workpiece or on lateral end of the vehicle axle, so the cooling elements are preferably immediately adjacent.

In the Middle is not cooled, so that the Austenittemperatur is reached or exceeded.

Under "end" in the context of the invention is the range of the axis that is at least needed around with a wheel carrier be welded to be able to. He is however selectable and may vary.

Under "middle" within the meaning of the invention is the remaining area to understand which is not for welding with the wheels is determined. The range is also freely determinable, however The expert is the stability reasons Central area as big as possible choose and the end area for safety reasons as large as necessary.

Out establish the energy economy becomes the middle range during the warming preferably sheathed with insulating shells.

Basically Both AC and DC are used, however the use of DC is preferred to the skin effect to prevent the use of alternating current in which the electricity as a result of its magnetic field is forced outwards, with the filling less well warmed up becomes.

The currents and tensions can be like that chosen For example, the axes will range from 20 ° C to 900 ° C within 20 seconds heated can be. The registered services are material-dependent.

To the Cool the ends, for example, cooling elements are used, the be operated with water, nitrogen, air or piezoelectric.

After this the vehicle axles have been heated in this way according to the invention are You a cooling supplied at the time of curing of the middle range heated to austenite temperature or higher is reached. The ends that the austenitic temperature does not reach have, stay soft enough to be with without further intermediate step the wheel carriers welded to be able to. For cooling, the Vehicle axles, for example, be placed in a water bath. The Cooling methods are known to the skilled person.

To a possibly required tempering process, the axes with the wheel carriers welded.

With the method according to the invention can Hardened vehicle or automobile axles in one step, the directly with the wheel carriers welded can be.

• – Mittel zum Einlegen der zu härtenden Achsen in die Elektroden, beispielsweise ein Roboter,
• – mindestens zwei Kontaktelektroden, vorzugsweise für Endkontakte und/oder Seitenkontakte,
• – eine Strom-Spannungsquelle,
• – mindestens zwei Kühlelemente zum Abführen von Wärme an den Enden der eingelegten Achse. Diese Kühlelemente können auch Bestandteil der Kontaktelektroden sein.
• – Mittel zum Entfernen der Achsen aus den Kontaktelektroden, beispielsweise ein Roboter.

For carrying out the method, a device may be used which comprises the following features:

• Means for inserting the axes to be hardened into the electrodes, for example a robot,
• At least two contact electrodes, preferably for end contacts and / or side contacts,
• A current voltage source,
• - At least two cooling elements for dissipating heat at the ends of the inserted axis. These cooling elements can also be part of the Being contact electrodes.
• Means for removing the axes from the contact electrodes, for example a robot.

Example:

They become axes 10 made of a cross-section tube profile. The two ends 20 . 30 the axis 10 must in principle be soft for welding or machining, which has hitherto been carried out by inductive annealing after hardening, by applying current to austenitic temperature, wherein the two ends provided with contacts are kept cold with cooling elements and do not harden during subsequent water quenching. In order to better hold the generated heat in the component, insulating shells are folded around the component during the time of the current flow, grabbed by heating with the robot and quenched in a fixing device in the water. Preferably, direct current is used because it does not have the skin effect of the alternating current through which the current due to its own magnetic field is forced outwards and, for example, the filling is heated less well.

A Axis with e.g. 100 mm diameter, 1000 mm length and 3 mm wall thickness, and a mass m = 7,13kg needs to be heated from 20 to 900 ° C in 20 seconds, about 230 kW heating power with, for example, 23,000 amperes and 10 volts.

When industrial form is used transformers and rectifiers. Thyristors are then used for switching.

the It is clear to a person skilled in the art that he can suitably regulate the power supply.

preferred Areas of the vehicle axles are at a diameter 80 to 120mm, lengths from 900 to 1200mm and a wall thickness of 2 to 4mm.

Hollow axes - in particular for small and compact cars - have for example, a weight m of 5 to 11 kg.

preferred Values for the cycle time of the production is between 15 and 45 seconds.

preferred Ranges of temperature rise from ambient to at about 900 ° C, but at least at austenite temperature.

The this required power is for example 100 to 400 kW.

The For example, a current between 10,000 and 25,000 Amps and a voltage 5 to 20 volts is reached.

The Ends stay below through targeted cooling the austenitic temperature so that they remain weldable.

10

axis

15

hardened part the axis

20

The End the axis

30

The End the axis

40

electrode (Contact)

50

electrode (Contact)

60

Wheel bearings

70

Wheel bearings

Claims (29)

Method for hardening vehicle axles by heating and cooling, in which the vehicle axle is conductively heated to at least the austenitic temperature of its material, wherein the vehicle axle is heated by at least two contact electrodes and the vehicle axle is cooled by quenching after reaching the austenitic temperature, characterized in that the Ends of the vehicle axle are cooled during the heating time, wherein the ends of the vehicle axle are cooled to a temperature below the Austenittemperatur. Method according to claim 1, characterized in that that the contact electrodes are attached to the ends of the vehicle axle become. Method according to one of claims 1 to 2, characterized that contact electrodes attached to the side of the vehicle axle become. Method according to claim 1, characterized in that that the ends of the vehicle axle to a temperature between 100 ° C and 800 ° C are cooled. Method according to one of claims 1 to 4, characterized that the middle part of the vehicle axle at Austenittemperatur is heated. Method according to one of claims 1 to 5, characterized that at least a portion of the central part of the vehicle axle is thermally insulated by an insulating shell. Method according to one of claims 1 to 6, characterized in that the vehicle axle is made of a material consisting of at least one component from the group of carbon-hardened steel or boron hardened steel or this includes. Method according to one of claims 1 to 7, characterized that the vehicle axle is hollow. Method according to one of claims 1 to 8, characterized that the vehicle axle is rod-shaped is or has a common form in the automotive industry, or is bent in the middle in one direction. Method according to one of claims 1 to 9, characterized that hardened an automobile axle becomes. Method according to one of claims 1 to 10, characterized that for the heating DC is used. Method according to one of claims 1 to 10, characterized that for the heating AC is used. Method according to one of claims 1 to 12, characterized that the vehicle axle after reaching the Austenittemperatur in cooled in a water bath becomes. Method according to one of claims 1 to 13, characterized that the vehicle axle after reaching the Austenittemperatur with a spray, especially water spray, is cooled. Method according to one of claims 1 to 14, characterized that the vehicle axle is conductive between 10 seconds and 60 seconds is heated. Method according to claim 15, characterized in that that the heating takes place with a power of 100 kW to 1000 kW. Method according to one of claims 1 to 16, characterized that the vehicle axle after quenching without further treatment by Heating the ends is welded to at least one wheel or a suspension. Method according to one of claims 1 to 17, characterized that the contact electrodes cooled and thereby the workpiece held in the region of the ends below the austenite temperature becomes. Method according to one of claims 1 to 18, characterized that for cooling the ends of the vehicle axle cooling elements be used. Method according to claim 19, characterized that as a cooling element a Peltier element is used. Method according to claim 20, characterized in that that as a cooling element a water element is used. Use of a device for curing, comprising following components: - Medium for inserting the vehicle axle into the contact electrodes, - at least two contact electrodes, - one Current voltage source, - Medium for cooling the tails the vehicle axle, - Medium for removing the vehicle axle from the contact electrodes. Use according to claim 22, characterized in that the means for inserting the vehicle axle into the contact electrodes and / or for removing the vehicle axle from the contact electrodes a robot is. Use according to claim 22 or 23, characterized the current voltage source generates direct current. Use according to claim 22 or 23, characterized that the current-voltage source generates alternating current. Use according to one of Claims 22 to 25, characterized that means for cooling the ends of the vehicle axle is a Peltier element. Use according to one of Claims 22 to 25, characterized that means for cooling the ends of the vehicle axle is a water cooling element. Use according to one of Claims 22 to 27, characterized that used for quenching a spray cooling becomes. Use according to one of Claims 22 to 27, characterized that for quenching a cooling bath is used.