MXPA00001597A - Method of laser beam welding of zinc-coated steel sheet - Google Patents

Abstract

A pair of coated components are laser welded to one another by initially forming protuberances on one of the components. The protuberances maintain juxtaposed surfaces separated and the components are then laser welded to one another. The separation of the surfaces vents vapor generated by the coating.

Description

METHOD OF WELDING WITH LASER RAY, OF STEEL SHEET REVERSED WITH ZINC FIELD OF THE INVENTION The present invention relates to a method for producing an overlap joint, of zinc-coated steel sheets, using a laser beam.

BACKGROUND OF THE INVENTION The increased use of steel sheets with high zinc coating, in automobile body components, to obtain an improved resistance against corrosion, poses a demand for an acceptable welding method, to join these types of sheet. One of the advantages of laser welding is the low total heat consumption and thus causes a low distortion of the high zinc content coating of the sheet. Therefore, welding with laser beam is being evaluated as a desirable joining technique for steel sheets, in both configurations REF: .32752 butt joint as overlap joint. However, a problem arises in the welding of these materials, in the overlap joint configuration, due to the low boiling point of the zinc (906 ° C) compared to the melting temperature of the steel (approximately 1550 ° C). If there is no joint gap, between the sheets, the zinc vapor, during welding can only escape through the molten solder pool, and this typically results in excessive porosity of the weld or a complete expulsion of the solder. welding metal. To make a good quality solder, there are two solutions in principle to avoid this problem: (1) create a vent channel for the zinc vapor, during welding; or (2) remove the zinc coating in the welding step. Both approaches require additional techniques to be carried out. Many techniques have been developed to provide clearance between the sheets in order to perform laser welding and remove the zinc coating at the point of welding. These approaches typically require the use of complementary components or separators and can not be used in the production line since additional equipment is required to create a clearance or to remove the coating. This will incur a significant expense and an increase in production time. Therefore, an object of the present invention is to obviate or mitigate the above disadvantages.

BRIEF DESCRIPTION OF THE INVENTION The present invention aims to provide a practical and flexible way to produce an overlap welding, with laser beam, of zinc-coated steel sheets. In general terms, a laser beam interaction is used with a surface of the material to create an acceptable clearance between the sheets, before performing the welding step. More specifically, protrusions are formed on a surface of a sheet by the incidence of a laser beam which maintains the opposing surfaces of the sheets in separate relation. In this way, the welding can be completed completely in a single welding apparatus, in an efficient and cost-effective manner. With such a technique it is possible to carry out a curved welding step and can be applied to a three-dimensional welding configuration. Therefore, this technique makes possible the production of welds, with laser beam overlap, of steel sheets coated with zinc, using an existing system for butt welding. The preferred embodiment of the invention relates to a method for creating a clearance for gas ventilation. steam, by the laser beam, before carrying out the welding. The principle is that a laser beam pulse, with an appropriate pulse length, can melt a spot on the metal sheet, when it interacts with the metal and the solidification of the molten metal forms a protrusion. The height of the protrusion, above the surface of the sheet, can be a few tenths of millimeters. A series of protuberances in a line or curve, it serves as a separator. When the sheet previously processed by laser pulses is placed next to another sheet, a gap is formed. Laser welding can thus be carried out along the marked line / curve and pass over the protuberances. The appropriate distance between the two protuberances created by laser depends on the clamping force, the power of the laser beam, the scanning speed and the thickness of the metal sheets. In the lap weld, the sheet on which the laser pulses generate protuberances may be either the top or the bottom. For both configurations, good quality welds can be produced.

DESCRIPTION OF THE INVENTION Now embodiments of the invention will be described by way of example only, with reference to the accompanying drawings in which: Figure 1 is a plan view of a pair of welded overlap components; Figure 2 is a view, on line 2-2, of the sequential steps for carrying out a welding on the components; Figure 3 is an alternative embodiment showing the production of a spot welding; Figure 4 is a photographic representation of a portion of one of the sheets shown in Figure 2; Figure 5a is a photographic representation of a section on the weld shown in Figure 1; Figure 5b is a photographic representation of a plan view of the weld shown in Figure 1; Y Figure 6 is a photographic representation of welded components, produced by the technique shown in Figure 2.

Therefore, referring to Figure 1, a pair of components 10, 12 are connected by seam or continuous welding, along a seam line 13 indicated in the line of chain stitches. Each of the components is a steel sheet having opposite directed surfaces 16, 17 and 18, 20 respectively. Each of the surfaces has an oxide inhibitor coating, typically a zinc coating 22 to provide protection against corrosion. As shown in Figure 2, one of the components to be welded, namely the zinc-coated steel sheet 10 is placed on a welding table (any type of table used for laser welding). A series of laser beam pulses 14 transmitted through a laser head 23 is used to strike one of the surfaces 16 of the sheet 10 and create a series of protuberances 15 along the intended welding line 13.

This process can be performed by moving the laser beam 14 on the sheet 10 or by manipulating the optical focusing elements of the laser head. Once the protrusions are formed by the pulses, the zinc-coated steel sheet 12 is placed on top of the sheet 10 subjected to laser pulses, such that the surface 18 is on the surface 16. Alternatively, Of course, the steel sheet 10 subjected to laser pulses can be placed on the upper part of the steel sheet coated with zinc 12. Under any conditions, the steel sheets 10, 12 are pressed against each other by a clamping press (not shown). As a result, the two sheets to be welded are clamped together and ready to be welded. The protuberances 15 form an air gap 24 between the opposing surfaces 16, 18 of the overlapping portions of the zinc-coated steel sheets 10, 12 along the weld line 13. The welding operation is carried out by applying the laser beam 14 to the steel sheets 10, 12 as indicated in Figure 2 by the arrow A. During welding the zinc vapor 26 of the zinc coating 22 can flow into the air space 24 surrounding the Thus, the weld is not formed, or few holes are formed for air, in the weld of solidified metal 19. Thus, the resulting weld has a satisfactory quality.In a typical welding operation, which uses a laser C0 of 1.5 W, the protuberances 15 were formed by pulses of the beam or beam, of 100-150 milliseconds in duration.The thickness of the sheet 10 was approximately 1.0 mm and the material was galvanized steel.The height of the protuberances 15 e of the order of 0.4 mm with a diameter of the order of 2 m. As can be seen from Figure 4, the protrusion is irregular but of a sufficient height. to keep the surfaces 16, 18 separated. The separation of the protuberances was approximately 50 mm for the selected material, although this spacing can be varied according to the material. The components 10, 12 were welded with welding seam using the 1.5 kW laser in continuous mode, making a run at a welding speed of 3.81 cm / second (1.5 inches / second). The resulting weld is presented in Figure 5 where it can be seen that a good homogeneity has been obtained. The above embodiment has been described with respect to a seam weld but a similar technique can be used for spot welding. As shown in Figure 3, one of the components 10 to be welded is placed on a table or work structure. In the places where the spot welds are to be made, with laser, a laser beam pulse 14 is applied on the surface 16, to create a protuberance 15. After all the sites are subjected to the lightning impulse laser 14, the steel sheet coated with zinc 12 is placed on top and held with the press. As a result of this configuration, an air space is formed between two sheets of steel coated with zinc, around the ridges generated by laser. The welding operation is carried out by applying a laser beam 14 to the steel sheets adjacent to each protrusion 1 * 5. The laser beam draws a circle of small radius around the protrusion to provide a localized circular weld. The weld will not be affected if the beam path intersects the protrusion. As described in the seam welding mode above, zinc vapor 26 escapes into the air space around the ridge. Therefore, a circular weld 19 is produced and the resulting weld has a satisfactory cavity. This circular weld can be considered as a spot welding. From the above description it will be seen that the creation of a natural separator by this technique is simple and flexible since the laser beam can be placed anywhere on the sheet, to create protuberances and to perform welding. In addition, the implementation of the lap weld can be carried out with the laser welding systems of the present, with few additional costs.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention. Having described the invention as above, property is claimed as contained in the following:

Claims (12)

1. A method for laser welding a pair of juxtaposed components, acterized in that it comprises the steps of forming on a surface of a component, a protuberance so that this projecting above that surface, juxtaposing the components in such a way that the opposite surfaces are keep separated by the protrusion, and laser weld the components by the incidence of a laser beam in the region in which the surfaces are located.

2. A method according to claim 1, acterized in that the protuberance is formed by the incidence of the laser beam.

3. A method according to claim 1, acterized in that the welding is formed by rotating the beam around one of the protrusions.

A method according to claim 1, acterized in that a plurality of protuberances are formed in a spaced relation, along a surface of one of the components.

5. A method according to claim 4, acterized in that the components are welded together by moving the laser beam along the surface and in the direction of the protuberances.

6. A method according to claim 4, acterized in that the components are welded to one another by rotating the beam around the respective protuberances, to provide a generally circular weld.

7. A method according to any of the preceding claims, acterized in that at least one of the components is coated with an oxide inhibitor coating.

8. A method according to claim 7, acterized in that the coating includes zinc.

9. A method for welding a pair of metal sheet components, having a corrosion resistant coating, with one another, acterized in that it comprises the steps of striking a laser beam on a surface of one of the components, to form a plurality of protuberances located thereon, at separate intervals, juxtapose the sheets with the protrusions interposed on the sheets, to maintain a separation thereof, and weld the sheets together by the incidence of the beam in the vicinity of the protuberances. .

10. A method according to claim 9, acterized in that the welding is carried out by transferring the beam through the components.

11 A method according to claim 10, acterized in that the beam is rotated around the protuberances, to provide a circular weld.

12. A method according to claim 9, acterized in that the beam intersects the protuberances during welding.