Method for the end-side welding of metal sheets

Abstract

A method for the end-side welding of at least two metal sheets disposed on one another in sections, includes selecting welding parameters such that, in the metal sheets to be connected, at least one of which is composed of a high-strength steel, a temperature with which the high-strength steel of the at least one metal sheet is tempered is generated at least in direct vicinity of an end-side weld seam. In addition, through a suitable selection of the welding parameters, a weld pool volume forming the weld seam is generated at an end side of the metal sheets. The weld pool volume has a width greater than the width of the end side of the metal sheets. Therefore, an undercut can be generated between the outer sides of the metal sheets and the weld seam. A form-locking connection can thereby be generated between the metal sheets and the weld seam.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a diagrammatic, sectional view of a B pillar of a motor vehicle body;

FIG. 2 is an enlarged, fragmentary view of a flange illustrated in FIG. 1;

FIG. 3 is an elevational view of a welded connection produced through the use of the method according to the invention; and

FIG. 4 is a perspective view of the metal sheets during welding.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the figures of the drawings in detail and first, particularly, to FIG. 1 thereof, there is seen a sectional illustration of a body pillar 1, which is embodied as a B pillar, of a motor vehicle. The body pillar 1 which is embodied as a B pillar has three metal sheets 2, 3, 4 that are each made from different materials and which, in a region of two flanges 5, are disposed on one another and are connected to one another through the use of a weld seam 7 disposed at an end side 6 of the metal sheets 2, 3, 4. The metal sheets 2, 3, 4 have different metal sheet thicknesses (see FIG. 3) and different steel characteristics. The metal sheet 2 is composed of a deep-drawn soft steel, in particular DC 05 ZE, while the metal sheet 3 is composed of a high-strength boron-alloyed heat-treated steel, in particular 22MnB5, and the metal sheet 4 is composed of a cold-formed steel with a high yield strength, in particular ZStE260 Z100.

FIG. 2 is an enlarged illustration of the flange 5 shown in FIG. 1. A heat-affected zone 8 which has a width of approximately 2 to 3 mm has been formed directly adjacent the weld seam 6 during the welding, and a temperature has at the same time been generated as a result of which the high-strength steel of the metal sheet 3 has been tempered. As a result of the tempering, the hardness of the metal sheet 3 made from the high-strength steel has been reduced in the region of the heat-affected zone 8, while at the same time the toughness has been increased. The structure of the metal sheet 3 made from the high-strength steel has been changed only in the region of the heat-affected zone 8. In this way, the strength or hardness of the metal sheet 3 is maintained in the regions outside the heat-affected zone 8.

FIG. 3 is a diagrammatic illustration of the welded connection 7 produced through the use of the method according to the invention during the welding of the end side 6 of the metal sheets 2, 3, 4 which are of different thicknesses. A weld pool volume 11 is generated at the end side 6 of the metal sheets 2, 3, 4 through the use of a heat beam 10 generated by a welding device 9. The weld pool volume 11 has a width b1 which is greater than a width b2 of the end side 6 of the metal sheets 2, 3, 4. Therefore, an undercut 14 is formed between the weld seam 7 or the weld pool volume 11 and outer sides 12, 13 of the outer metal sheets 2, 4. A form-locking connection is thereby formed between the metal sheets 2, 3, 4 and the weld seam 7 generated from the weld pool volume 11.

FIG. 4 shows a perspective view of the metal sheets 3, 4 during the welding. The welding device 9 is connected through the use of a coupling device 15 to a pressing device 18 which has two contact rollers 16, 17. The metal sheets 3, 4 which are to be welded are disposed between the two contact rollers 16, 17, with the outer sides 13, 19 of the metal sheets 3, 4 being acted on by the pressing device 18 with a pressing force Fa which positions the metal sheets 3, 4 in an assembly position in the region of a joining location 20. The welding device 9 and the pressing device 18, which are connected through the use of the coupling device 15, are moved together in a feed direction 21. The movement in the feed direction 21 is provided through the use of a drive device which is associated with the coupling device 15 or through the use of at least one driven contact roller 16, 17.

Claims

1. A method for the end-side welding of at least two metal sheets disposed on one another in sections, the method comprising the following steps: providing at least one of the metal sheets as a high-strength steel sheet;selecting welding parameters for the metal sheets to be connected, to generate a temperature for tempering the high-strength steel of the at least one metal sheet, at least in a direct vicinity of an end-side weld seam;producing a weld pool volume forming the weld seam at an end side of the metal sheets to be connected, the weld pool volume having a width greater than a width of an end side of the metal sheets to be connected; andproducing an undercut between outer sides of the metal sheets and the weld seam.

2. The method according to claim 1, which further comprises producing the end-side weld seam by a beam welding process generating a temperature required for tempering, a formation of a heat-affected zone in the metal sheets to be connected and a sufficiently large weld pool volume at the end side of the metal sheets, by a variable adjustment of at least one of a welding speed or a beam power.

3. The method according to claim 2, wherein the beam welding process is a laser beam welding or electron beam welding process.

4. The method according to claim 1, which further comprises producing the end-side weld seam by a gas-shielded welding process generating a temperature required for tempering, formation of a heat-affected zone in the metal sheets to be connected and a sufficiently large weld pool volume at the end side of the metal sheets, by a variable adjustment of a welding current and at least one of a welding voltage or a welding speed.

5. The method according to claim 4, wherein the gas-shielded welding process is a GMA welding or TIG welding process.

6. The method according to claim 1, which further comprises adding a filler material and producing a sufficiently large weld pool volume by varying a quantity of the filler material during welding.

7. The method according to claim 6, which further comprises carrying out the step of varying the quantity of the filler material by varying a wire feed speed.

8. The method according to claim 1, which further comprises, during welding, acting on the metal sheets in a region of a joining location with a pressing force directed at outer sides of the metal sheets for positioning the metal sheets in an assembly position.

9. The method according to claim 8, which further comprises providing a pressing device generating the pressing force, and a welding device, and moving the pressing device and the welding device together in a feed direction.