KR20050023271A - Laser welding with beam oscillation - Google Patents

Abstract

A method of welding metal components to each other, the laser beam focused by moving the laser beam 20 in the first direction A along the interface 22 between the pair of metal components 24 and 26. Vaporizing each metal component to create a keyhole 28 in the molten metal pool 30 in the vicinity of 20. The laser beam 20 is different from the first direction so that as the position of the keyhole 28 changes, the keyhole 28 vibrates over the entire region of the molten metal pool 30 so that the molten metal fills the keyhole 28. It vibrates in the direction B (for example, across the first direction).

Description

Laser welding method using laser beam vibration {LASER WELDING WITH BEAM OSCILLATION}

TECHNICAL FIELD The present invention relates to laser welding, and more particularly, to vibration welding of a laser beam to produce a keyhole that moves and refills.

Typical welded joints include butt joints, overlap-penetration joints, and overlap-fillet joints. Laser welding uses a focused beam of coherent light to melt adjacent metal components and solidify the molten metal to the seam to join the metal components. Butt joints can be made by laser welding, but are not always suitable for the aerospace, automotive and marine industries. Laser welding of overlap-injection joints and overlap-fillet joints is more difficult to implement. 1 and 2 show the results of laser welding of overlap-welded joints where the laser beam is directed to the region of the interface 2 between the component 4 and the component 5. Relative movement is made along the interface 2 between the laser beam and the assembly of components. This laser beam may volatilize a portion of the metal at the interface to create a keyhole 8 bounded by molten metal 10. This keyhole 8 is advanced with movement of the laser beam in the direction of the arrow A. FIG. Molten metal 10 solidifies at the rear of the advancing keyhole 8 to make a joint between the components.

In practice, overlap-splice joints and overlap-fillet joints by laser welding are limited. For example, it is well known that in overlap-welding joints as shown in FIGS. 1 and 2, the width W of the weld should be greater than or equal to the thickness t of the thinnest side of the components to be joined. have. The welding process should be controlled to minimize the void generation of the weld caused by volatilization of the low melting point component (eg Mg) and / or instability in the keyhole at partial high pressure. In addition, laser welding is relatively expensive. Generally, the laser beam is operated at 10 ⁶ W / cm 2 or more and requires an efficiency of welding at a speed of at least 80 inches per minute at this power level. When welding a 0.1 inch thick component, it is possible to make the required 0.1 inch weld width W at speeds in excess of 120 inches per minute. The generation of voids can be properly controlled by using an out of focus beam or a bifocal optical system. However, the thicker the material, the more difficult it is to achieve the required weld width while maintaining acceptable weld quality and travel speed.

When laser welding overlap-fillet joints, the welding system is used to achieve performance comparable to that of weld metal produced by gas metal arc welding (GMAW) at a suitable speed for use in costly laser welding systems. The change in the lateral position of the laser beam with respect to the gap and the junction edge must be accommodated.

One option to overcome the problems of laser welding overlap-injection joints and overlap-fillet joints is to use a beam integrator, a focal optic (mirror or lens) with a long focal length, or an unfocused beam. However, in order to ensure reliable and consistent optical coupling between the component to be bonded and the laser and to achieve local melting at the joint, the power output of the laser system must be increased to compensate for the reduction in power density. If the power output is sufficient, a wider weld can be made in a quieter conduction mode rather than a keyhole mode. Unlike the keyhole mode, which involves the translation of the cavity (or keyhole) along the junction zone, the conduction mode is achieved by translating the molten pool of metal along the junction zone. By minimizing the intense volatilization of the metal in the keyhole, a more calm conduction mode can eliminate the instability of the keyhole mode. As a result, the conduction mode minimizes the formation of voids in the laser weld. However, the realization of this approach requires the use of very powerful lasers and costly laser generation systems, which is impractical for many industrial applications.

Another approach to increasing the effectiveness of laser welding by vibrating a laser beam at frequencies above 1000 Hz is disclosed in US Pat. No. 4,369,348. This very fast movement of the laser distributes the laser's intensity on average at frequencies greater than the thermal response time of the metal. In this way, the average heat intensity received at the interface of a particular location between the joined metal components is greater than that received without vibration. However, operation of the laser beam at vibration frequencies of 1000 Hz or more is difficult and expensive. In addition, the only way to realize this approach is to weld in a conduction mode where a continuous melt pool is maintained.

Therefore, there is still a need for a low cost effective laser welding method.

1 is a schematic cross-sectional view of a pair of metal components laser welded to form a keyhole according to the prior art;

2 is a plan view of the laminated metal component shown in FIG. 1 operated according to the prior art;

3 is a perspective view of a pair of metal components laser welded according to the method of the present invention;

4 is a plan view of the stacked metal components shown in FIG. 3; And

5 is a schematic cross-sectional view of the metal component shown in FIG. 4.

Such a need relates to a method of the present invention comprising focusing a ray point beam at a junction area between a pair of metal components to form a continuous metal melt pool and creating a keyhole in the metal melt pool. Are satisfied by The metal melt pool is a mixture of each metal component. By vibrating the laser beam in a direction different from the first direction with respect to the molten metal pool while moving the focused laser beam along the joining zone in the first direction, the keyhole is continuously moved and immediately refilled by the adjacent molten metal. . Welding occurs as the keyhole passes through the molten metal pool to melt the metal component to be welded at the interface. In the vicinity of the focused laser beam, the molten metal pool is vaporized to create a keyhole that is moved by the vibrating laser beam. As the laser beam vibrates in a direction different from the first direction (eg, the direction transverse to the first direction), the keyhole vibrates through the molten metal pool and the molten metal is filled into the keyhole as the keyhole vibrates. . In this way, keyholes are continuously made and then refilled with molten metal which solidifies to make a weld.

The welding can be overlap-infusion welding, butt welding, or overlap-fillet welding. Depending on the joint, thickness combination, and welding position, the laser beam vibrates at a frequency of about 5 to about 120 Hz and advances in the first direction at a speed of about 5 to 400 inches per minute. When referring to the range of frequencies or dimensions herein, this range includes all intermediate values, for example the speed in the first direction includes all values ranging from about 5 to about 400 inches per minute. The vibration can be straight, circular, elliptical, or a combination thereof, or any other shape that causes the keyhole to move. The thinner side of the metal components may be at least 0.1 inch thick. The present invention enables various types of jointing methods with lasers having custom weld dimensions (e.g., 0.25 inch interface weld width between components having a thickness of 0.25 inch) using lasers. do.

In the method of the invention, metal components such as steel or aluminum alloy are laser welded. As shown in FIG. 3, radiation 20, such as a laser beam, is focused on the interface 22 between a pair of metal components 24, 26. The metal components 24, 26 of FIG. 3 are stacked together to form overlap-intrusion welds. Without being limited to this, other welded joints, such as butt welds and overlap-fillet welds, may be produced in accordance with the method of the present invention. The laser beam 20 travels in the direction of arrow A, which can be a straight path or other type of path. The path of arrow A determines the joint position between components 24 and 26.

While the laser beam 20 proceeds in the direction of the arrow A, the laser beam is also vibrated in the direction of the double arrow B. The double arrow B crosses the direction of the arrow A to form an angle with respect to the arrow A. FIG. In FIG. 3, the laser beam 20 is shown oscillating in a straight path perpendicular to the arrow A, but is not limited to this. The laser beam 20 may travel in other paths, such as circular, elliptical, sinusoidal, or the like. As shown in FIGS. 4 and 5, the metal of the components 24, 26 in the vicinity of the focused laser beam 20 vaporizes to create a keyhole 28 surrounded by molten metal 30. Vibration of the laser beam 20 causes the keyhole 30 to fill the molten metal 30 and to form a new keyhole 28 adjacent thereto. When the keyhole 28 moves from one position to another in succession across the path of arrow A and empties the previous position in the pool of molten metal 30, the empty keyhole 28 is filled and a new keyhole ( 28) is formed again. This process represents the type of movement of the keyhole across the molten metal 30 while acting to continually recover the emptied keyhole 28. In this way, welds with a significantly wider width W ₁ are made than prior art welds. For example, in welding overlap-welded joints, the present invention can be joined to have welds having interfaces that are equal to or greater than the thickness of the thinner portion of the welded portion. The welds produced using this method have a width of 2 to 5 times the width of the laser beam welds produced using conventional methods. Wider welds are particularly useful for producing thick components, ie, overlap-welding welds of thick components from 0.1 inch up to about 0.25.

Suitable frequencies of vibration of the laser beam 20 are about 5 to about 120 Hz and may be about 10 Hz. The laser beam may advance along the interface at a speed of about 5 to about 400 inches per minute, or about 40 to about 200 inches per minute, or about 80 inches per minute.

In some cases, it may be advantageous to include a source of filler material, such as filler wire. The filler metal may be added during welding and may be in the form of a wire or powder having a diameter between about 0.030 and 0.062. The filler metal can be an alloy selected based on the desired properties of the weld using established engineering principles. The filler metal can generally be added to the front or rear of the melt pool in a horizontal direction, ie at an angle between 30 and 60 degrees from the plane of the upper component. In addition, process gases may be used to protect the molten pool and redirect the vaporized metal away from the beam and material interaction zone, generally referred to as plasma suppression. In general, gas is provided in front of the welding pool through a nozzle facing the rear of the pool at an angle between 30 and 60 degrees from horizontal.

Yes

Overlap-welded laser welds are used on a 0.196 inch thick pair of aluminum-coated alloy 6013-T6 plates under the top surface of the laminated plate with a 4047 alloy filler wire of 0.045 inch diameter at a feed angle of 35 ° and a wire feed rate of 90 inches per minute. It was produced using a 10 kW power CO ₂ laser running at 80 inches per minute focused at 0.25 inch of a helium as a plasma inhibiting gas from the moving front, provided a flow rate of 110 cubic feet per hour. The laser was vibrated in a straight line in the direction transverse to the welding direction at a speed of 400 inches per minute and an overall vibration width of 0.25 inches (ie, 0.125 inches from center to center). The weld width of the resulting interface was slightly larger than 0.22 inches.

While the preferred embodiment has been described, the invention may be practiced in other ways within the scope of the claims.

Claims (12)

A method of welding metal components to each other, Moving the laser beam in a first direction along an interface between a pair of metal components to melt and vaporize metal from each metal component in the vicinity of the laser beam to create a keyhole in the molten metal pool; And Vibrating the laser beam in a direction different from the first direction so that the keyhole vibrates over the entire region of the molten metal pool so that the molten metal is filled in the keyhole as the position of the keyhole changes; Welding method comprising a. The welding method according to claim 1, wherein the laser beam vibrates in a direction transverse to the first direction. The welding method according to claim 1, wherein the welding method is overlap-welding welding. The welding method according to claim 1, wherein the welding method is butt welding. The welding method according to claim 1, wherein the welding method is overlap-fillet welding. The method of claim 1, wherein each metal component comprises an aluminum alloy. The method of claim 1, wherein the laser beam vibrates at a frequency of about 5 to about 120 Hz. 8. The method of claim 7, wherein the laser beam advances along the interface at a speed of about 5 to about 400 inches per minute. 8. The method of claim 7, wherein the welding is performed over a width of about 0.1 to about 0.25 inches. The welding method according to claim 1, wherein the laser beam vibrates in a straight path. The welding method according to claim 1, wherein the laser beam vibrates in a circular path, an elliptical path, or both paths of the circular path and the elliptical path. 4. The method of claim 3, wherein the thickness of the thinner of the metal components is at least about 0.1 inches.