DE102004045436B3 - Process to harden the rim of a double-walled metal rim, e.g. steering wheel column, by heating, quenching, tempering and alternating current induction circuit - Google Patents

Abstract

In a process to harden the double-walled metal rim around a detent in e.g. an automotive steering wheel column, the metal is heated, quenched and tempered as required, during which both sides of the rim are in contact with a water-cooled induction loop bearing alternating current. The electrical current is identical on both sides of the rim, inside and outside.

Description

The The present invention relates to a method of curing edges indentation, inductive hardenable metallic objects, as well as Products made by this process.

At the hardening Steel parts are placed on e.g. heated above 900 ° C and subsequently quenched, with the desired martensitic microstructure transformations occur. Thereafter, the parts are tempered by moderate heating.

In the EP 1 160 108 B1 a method for the partial hardening of torsion beam axles is described in which induction conductors, for example as a helix, are placed around their ends in order to harden their ends. This is to ensure that the end areas are indeed hardened, the middle area, however, "torsionally soft".

apart of that with it the edge around the depression of the torsion beam axle is not curable, consists in such a procedure in the curing of Twisted-beam axles pose the danger of being on the interior areas where the upper, down-compressed phase is applied to the lower or this close, a weld by heating occurs, which can lead to cracking (multiple) twisting, because here the two sheet metal segments can no longer slide together, which when tearing off the welding leads to notch effect. Furthermore, the upper edge of the channel-shaped depression is uncured one exposed by the shaping increased risk of injury, plastic deformation on this one edge representing sensitive Area leads also to easier kerf formation than in the mechanically more stable Coat.

The The present invention is therefore based on the object, a method to create, after which wells having objects alone curable in its edge region are, in particular, so that twist-beam axles without the risk of internal welding be produced at the close areas, the modified Have properties.

The solution This object is achieved in a method for curing double-walled edges of metallic depressions by heating, quenching and possibly Tempering, wherein on both sides of the edge and near this one current-carrying, water-cooled Induction conductor laid in such a way and charged with alternating current, that the current direction is outside and inside are the same.

The cooled Conductors are preferably laid near the inner and outer edges, that the current direction is opposite to the outside on the inside reverses, i. the ladder is returned here. The ladder is here arranged meandering and to the opposite Ends of the wells led out. Such an arrangement opens the possibility, e.g. arrange pairs of conductors on both sides, which are then the same on each side Have current directions. This is therefore of particular importance otherwise heating up to the required for the martensite about 950 ° not is reached, wherein the bent edges which occur in itself Shield opposing fields.

The Copper conductor advantageously have a rectangular, z. B. square cross section, causing them to be heated edges relatively large surfaces return.

It may be advantageous, in particular in the case of the above-mentioned composite link axles, which have a stretched shape, including the throat at the inner ends to harden the depression. For this purpose, it is proposed that the current conductor correspondingly deep from the Lead out Muldenkehlen.

It is according to the invention also possible, the hardening the edge areas to modify, for example, that the Current conductor along the edges not linear, but curved run, for example, be pulled down slightly in the middle. scares you have such a heated Subject from, so creates a corresponding hardened profile.

Based The enclosed figures, the present invention will be explained in more detail. there demonstrate

1 a Torsionslenkerachse and

2 a cut through this.

1 shows as a typical example of the application of the present invention, the center piece 1 a torsion beam axle of a car. It is made of a tube into which an elongated recess 2 was formed, creating a circumferential edge 3 is formed, which has a relatively small bending radius. At the ends remain round openings 4 in which the trailing arm (not shown) can be inserted. At the same time, this structure has a medium cross-sectional taper.

The torsion beam axle according to the invention 1 differs from the state of the art in that these are around their edge 3 around inside and outside has a few centimeters wide strip of harder, martensitic structure, which on the one hand increases the strength of the edge against impact injury, on the other hand, does not adversely affect the torsion properties. In addition, this axis has no internal welding points. The service life is thereby increased.

2 illustrates the manufacturing process. Shown is a cross section through the central region of the axis 1 (The underlying round tail is omitted). The axis 1 consists of the outer jacket 5 and the inner coat 6 , Dashed, the average cross-sectional taper is indicated.

Next to the coats 5 . 6 are the interconnected conductors 7 . 7 ' shown. These run in the opposite direction to the outer, with each other they have the same direction of flow outside or inside, where they are laid in a meandering manner such that the ends of the conductor to their connections inside the throats 8th led out of the depression.

It is advantageous in such an arrangement that the meandering current conductor 7 . 7 ' can remain stationary, the object to be cured is inserted from below. This allows automated heating (and hardening or automated tempering).

The ladder 7 have outer dimensions of eg 10 × 10 mm. The wall thickness is 1 mm. The heating takes place, for example, with 35 kW at 400 V and 600 amps with mF energy, preferably 10 kHz.

Of the Steel jacket edge is heated to 950 ° C within 15 seconds, for 60 Seconds to keep the temperature at this temperature, to quench within 10 seconds.

Claims (8)

Method for hardening double-walled edges of metallic wells by heating, quenching and optionally Tempering, wherein on both sides of the edge and near this one current-carrying, water-cooled Induction conductor laid in such a way and charged with alternating current, that the current direction is outside and inside is the same. Method according to claim 2, characterized in that that you laid the conductor in pairs meandering so that on both sides the edge ever co-running pairs arise, with the inside and outside entgegenlauflaufende Couples present. Method according to claim 1 or 2, characterized that the conductor is a square, internally cooled by water cross-section having. Method according to one or more of claims 1 to 3, characterized in that in elongated depressions the Conductor ends are brought out in near the throats. Method according to one of claims 1 to 4, characterized the recess is part of a torsion beam axle. Twist-beam axle for a car, characterized that these are longitudinal hardened the edge of their depression is. Twist-beam axle according to claim 6, characterized in that that the hardened Edge one by shaping the conductor or by an additional Conductor has given edge area with profiled hardening. Method according to claim 6 or 7, characterized in that in addition to the edge ( 3 ) also the throats ( 8th ) are cured.