DE102018001460A1 - Method and device for integrally joining metallic materials by means of at least one laser beam source - Google Patents

Abstract

The invention relates to a method and apparatus for cohesive bonding, in particular laser beam brazing or laser beam welding, metallic materials, in particular of surface-coated materials, such as metal or metalloxidbeschichteten materials by means of at least one laser beam source, wherein an upstream and / or downstream of a laser beam melting of a filler material and / or adjacent seam flank areas of a base material preforming and / or reheating by means of shortwave and / or longwave electromagnetic radiation is provided. For this purpose, at least one tempering radiation source for short-wave and / or long-wave electromagnetic radiation is arranged upstream and / or downstream of the laser beam source.

Description

The invention relates to a method and a device for bonded connection, in particular laser beam brazing or laser beam welding, metallic materials, in particular of surface-coated metallic materials, such as metal or metal oxide coated materials, by means of at least one laser beam source.

Laser beam brazing is an important process for joining metallic materials using a molten filler material, possibly with the use of flux. The melting temperature of the solder is below that of the base materials to be joined without being melted. Surface coatings or coatings with metals or metal oxides, hydroxides influence the flow behavior of the solder, furthermore the adhesion and diffusion of the solder material on or into the base material as well as the homogeneity of the formed solder seam.

In many cases, brazing is used in body and vehicle construction, for example for the production of flanged seams, as a rule zinc-coated steel sheets are processed which have to be reliably and long-lasting, tight and with high surface quality via the soldered seam. However, due to the high standards in automotive engineering, quality problems often arise that require extensive and costly reworking. Thus, in the case of materials with metallic surface coatings, in particular with anticorrosion coatings with zinc and its alloys, cracking and pore formation occur in the solidified solder seam. Thus, zinc deposits at the grain boundaries and thus under the influence of residual stresses can lead to solder breakage-like cracks in the solder seam. Pore formations are due to the evaporation of the coating material during the soldering process and its inclusion in the solder material, such as trapped zinc vapors. These in turn are based on different and unsteady, disturbed, time-dependent heat conduction processes during heating and cooling of the component (base material) and solder. For technological and economic reasons, these phases are extremely minimized in laser brazing in manufacturing. In addition, there is a negative enthalpy due to evaporative coldness when vaporizing low surface area metallic surface coatings, as is true for zinc.

The same applies to laser beam welding processes, especially in thicker-walled components, in which z.T. only an insufficient heating of the seam flanks of the base materials takes place.

The invention is therefore based on the object of specifying a method and a device of the type mentioned, which allow the cohesive bonding, in particular laser beam brazing or laser beam welding, metallic materials, in particular of materials having metallic or metal oxide coatings to improve , Furthermore, it should be possible to significantly improve the connection strength, quality and error-free formation of seams. At the same time it should be possible on the device side, existing equipment for material bonding, especially for laser beam brazing or laser beam welding in a simple manner and cost to complement and perfect.

The above object is achieved in terms of the method according to the invention by the features of claim 1. Advantageous developments of the method according to the invention are the subject of the associated subclaims.

According to the invention, therefore, the flow behavior of a filler material, such as a solder material and a harmonized heat of enthalpy, i. a uniform heat content of the component surfaces of the base materials to be joined, as well as the already formed seam achieved in that before and / or after Laserstrahlaufschmelzung a filler material, such as a solder material (ie upstream and / or downstream thereof) and / or adjacent seam flank regions of a base material a pre-heating and / or reheating of the base material and / or the seam, by means of short-wave and / or long-wave electromagnetic radiation, most preferably with a mixture of ultraviolet (UV) and infrared (IR) radiation, since the pros and / or reheating by UV radiation a penetration depth of the heating up to the root of the seam, such as a soldered seam allows, while the IR radiation a high degree of surface heating of both the already prepared seam and the surfaces of the base material in the vicinity of the flanks Area of the connection seam allows.

To support the laser beam melting process, therefore, an additional temperature regime is created which preheats and / or reheats the joint seam area, in particular the solder seam area (and its immediate surroundings). From the flow behavior of the additional material (eg solder material) and the total enthalpy, the heat content of the base material and the connection area width and depth of the Connecting seam, in particular soldering seam; Wetting degree, fine grain formation of the solidified additional material (eg Lotes), adhesion quality to the base material and the formation of diffusion ratios in the surface region of the connecting seam (especially solder seam) determined. The quality of the cohesive connection, in particular braze joint is largely a function of the cooling time.

By pre- and / or reheating thermal stresses to the environment due to the punctiform Laserstrahleinwirkung and thus seam defects are avoided or minimized Lötnahtfehler and avoided the negative effects of evaporation of the coating material, due to the occurring evaporation of cold on the environment of the seam, especially solder seam in the area the base materials to be joined as well as the formation of the joint itself.

Depending on the manufacturing task to be solved, the wave spectrum between short-wave and lag wave electromagnetic radiation is freely adjustable and miscible within a wide range.

Preferably, the cohesive bonding, in particular brazing in inert gas atmosphere and there is both a pre- and a reheating of seam and seam environment by the laser beam source upstream and / or downstream thereof associated tempering radiation sources, preferably a mixture of short and long-wave electromagnetic Provide radiation.

The above object is achieved according to the device according to the invention by the features of claim 8.

According to the invention, therefore, the laser beam source is assigned at least one tempering radiation source for short-wave and / or long-wave electromagnetic radiation, arranged upstream and / or downstream of the laser beam source, which homogenizes the heat entropy within the connecting seam, in particular solder seam, as well as in the flank region thereof and in the environment causes the seam in the base material.

Preferably, a tempering radiation source is arranged upstream of the laser beam source and a further tempering radiation source downstream of the laser beam source and these are movable in synchronism with the laser beam source in the working direction.

Each tempering radiation source preferably has two radiation sources for incoherent electromagnetic radiation, in particular one for short-wave, preferably ultraviolet radiation and in particular one for long-wave, preferably infrared radiation.

Depending on the particular manufacturing task and in particular the production speed, however, only one of the two radiation sources for electromagnetic radiation in the tempering radiation source may be provided, preferably alternately with respect to UV and IR radiation in the tempering radiation source leading and trailing to the working laser beam ,

It is also conceivable to arrange the two radiation sources below the components.

Preferably, the tempering radiation source comprises at least one radiation source for ultraviolet radiation and a radiation source for infrared radiation, preferably also a radiation source for visible light.

The tempering radiation source is preferably arranged in a cooled reflector chamber, which may be preceded by lens optics, for collimation or bundling of the electromagnetic radiation emitted by the temperature-controlling radiation source.

In an advantageous embodiment, the reflector chamber is connected to a protective gas source for supplying a protective gas to this and the electromagnetic radiation emitted from the reflector chamber and / or the reflector chamber and / or a protective gas flow exiting therefrom and / or the emitted electromagnetic radiation of the temperature control radiation source a resulting angle in the range of about 30 ° to 45 ° to a, a connecting seam, in particular solder seam forming laser beam (working laser beam) of the laser beam source is arranged.

One or more tempering radiation sources can be arranged on the same working side as the laser beam source (upper side) or also on the side opposite the laser beam head with regard to the base material (lower side).

Preferably, the reflector chamber is cooled by a directly connected to this heat pipe (heat pipe), in which one makes use of the energy balance of material conversion processes (evaporation / condensation), to advantage.

In a preferred embodiment of the invention, the laser beam source is a laser head with a plurality of monochromatic mono- or multifocal laser beams, in particular a Multifocal laser head which preferably emits a monochromatic, coherent main laser beam (working laser beam) and at least one, preferably two monochromatic, coherent secondary laser beams.

By means of the solution according to the invention, adjustment of necessary prewarming and reheating times takes place via the electromagnetic energy emitted by the radiation energy, preferably generated by a high-power mixed emitter in the wavelength ranges of electromagnetic radiation of ultraviolet and infrared. Shortwave, especially ultraviolet, radiation is absorbed in the zinc coatings of iron-based metallic components (base materials) found in vehicle bodywork. This leads to an energy conversion process within the metallic protective layers, such as a zinc layer, causing partial heating and promoting the energy transfer of incident infrared radiation components to these zinc surfaces, with propagation to the underlying base materials. Lattice vibrations generate component heating, electrons are transported to higher energy levels, the coupling of the laser radiation into the connection process phase is favored (in particular the soldering process phase "melting of the solder"), and the formation of adhesive bonding forces and diffusion processes between filler material, in particular solder and base material ,

Infrared radiation causes a classical surface heating, which counteracts the heat radiation of the metal vapor from additional material, in particular solder and zinc and the heat radiation from the molten bath of solidified filler melt, in particular solder melt, and the heat radiation from the component surface.

The combination of ultraviolet radiation and infrared radiation in a tempering radiation source before and after the laser beam head is therefore particularly advantageous.

The invention is explained below with reference to an embodiment and an accompanying drawing. In this is a schematic representation of a laser beam - soldering 100 with a laser beam source 1 and two tempering radiation sources 10 . 11 one of which is upstream of the laser beam source 1 and one downstream of the laser beam source 1 is arranged and at the same operating speed as the Laserstrahlquelle1 in one direction 12 be moved to form a braze joint.

In the schematic figure and single figure, 1 is the laser beam source, hereinafter as a laser head 1 referred to, for brazing between two zinc-coated steel sheets 2 , which are provided here as representatives of iron-based base materials which are conditioned by galvanic coatings of, for example, Zn, Sn, Cu, Ti, Mg and their alloys or oxides and in particular are corrosion-resistant. The steel sheets 2 should by a hemming seam 3 be joined together by brazing. An already made of brazing material portion of the solder seam is indicated in the figure with 4.

A separately supplied as filler material soldering material is here as a rod 5 shown, but can also be used as a wire or in powder form in a soldering area 6 , hereinafter also referred to as laser core melting range, are performed. The laser head 1 is provided with a laser optics for one or more monofocal or multifocal laser beams and has in the present embodiment, a monochromatic, coherent laser beam 7 as main jet (working jet), which is responsible for the melt liquefaction of the solder material 5 provides. In the present embodiment, the laser head 1 next to the laser beam acting as main and working beam 7 (Primary laser beam) two more, monochromatic, coherent secondary laser beams 8a . 8b on to the homogeneity of the energy input into the soldering area or laser core melting area 6 , increase and improve the quality of the braze joint in this way. The power of these secondary laser beams 8A . 8B is in the range of about 0.2 kW to about 0.8 kW. These secondary laser beams 8A . 8B are used to heat the laser to the core fusion area 6 for the soldering material 5 adjacent heating areas 9 , in particular towards the flanks of the solder seam 4 in the diffusion and transition region to the base material, ie to the steel sheets 2 , In this way, the bond and bond strength between the solder joint 4 and the steel sheets to be joined 2 in the flank area of the flanged seam 3 increased, with support of diffusion processes between the solder material 5 and the base material, ie the coated steel sheets 2 , An adhesion / diffusion zone between solder and base material (steel sheets 2 ) is designated 19 in the figure.

To introduce a controlled temperature regime and to establish a controlled heating and cooling of the solder material base material (steel sheet 2 ) -Verbundes becomes a harmonized distribution of the heat content (enthalpy) of the component surfaces in the area of the formation of the Lötnaht 4 achieved in that in the present embodiment, both upstream and downstream of the laser head 1 a preheat (reheat) (cooling) heat source in the form of a first and second tempering radiation source 10 . 11 is provided, which in one direction 12 leading and trailing with respect to the laser head 1 arranged and formed as electromagnetic radiation sources.

In the context of the present application, the terms "electromagnetic waves" and "electromagnetic radiation" are used synonymously.

In the present embodiment are for preheating (flank heating) of the solder seam near the edge regions 13 the steel sheets 2 and for postheating (= controlled cooling) of a solder diffusion zone 14 the finished soldered seam 4 downstream of the soldering area 6 and their adjacent areas of the base material (coated steel sheets 2 ) two synchronously with the laser head 1 moving tempering radiation sources (light source heads) 10 and 11 intended. They form light source heads for an incoherent mixed light, preferably in the ultraviolet range and infrared range, both for the base material (steel sheets 2 ) as well as for the solder material 5 and have a shortwave radiation source 15 and a long-wave radiation source 16 on, with the short-wave radiation source 15 to radiation of ultraviolet radiation and the long-wave radiation source 16 to radiation of infrared radiation is used. These light source heads 10 . 11 can also be used alternately or alternately, depending on the heat input conditions.

After the quality of the solder joint is also a function of the cooling time, it is possibly also possible only with respect to the laser head 1 downstream light wave head 10 or only one radiation source at a time 15 for short-wave UV radiation or a radiation source 16 provide for long-wave IR radiation or, if these two radiation sources 15 . 16 together in the relevant light source head 10 or. 11 are provided to use these only alternative. Preferably, however, a mixture of short-wave and long-wave electromagnetic radiation from both radiation sources 15 . 16 in a light source head 10 . 11 at the finished soldered seam 4 for controlling the cooling of the soldered seam 4 and the environment of the same.

However, it is also the application of the upstream light source head 11 for heating and preparing the flank areas of the steel sheets 2 in the area of the flanged seam 3 advantageous and preferred.

Preferably, therefore, each light source head 10 . 11 a radiation source 15 for short-wave electromagnetic radiation (UV radiation) and a radiation source 16 for long-wave electromagnetic radiation (IR radiation), which are used alternately, alternately, but most preferably cumulatively together and simultaneously. Wavelengths in the range of <= 400 nm and as long-wave electromagnetic radiation preferably wavelengths of> = 780 nm are considered as short-wave electromagnetic radiation, wherein their mixing ratio (proportions of radiation of a defined frequency spectrum) can be selected freely adjustable. Optionally, the light source head 10 . 11 also additionally have a radiation source for electromagnetic waves in the range of visible light (about 400 nm to about 800 nm).

The particular advantage of the simultaneous use of short and long-wave electromagnetic radiation in the soldering area 6 and most preferably on both sides of the laser head 1 and under the influence also in the Lötnaht 4 neighboring areas 13 the steel sheets 2 (the base material) is that it has been recognized that the flow behavior of the solder material 5 and the total enthalpy, ie the total heat content of the base material (steel sheets 2 ) in the solder area 6 , the width and depth of the soldered seam 4 , the degree of wetting of the steel sheets 2 , the fine grain formation of the solidified solder material, ie the finished soldered seam 4 and adhesion quality and the formation of diffusion ratios in the surface area and in the flank areas of the solder seam 4 determine.

The additional arrangement of tempering radiation sources 10 . 11 allows to control the quality of the solder joint as a function of the cooling time and the base material (steel sheets 2 ) by preheating the subsequent soldering process and the action of the working laser beam 7 prepare so that the temperature gradient between the laser core melt area 6 and the environment of this area decreases, the negative influence of the evaporative cooling due to the evaporation of the zinc coating canceled or at least drastically reduced and thus the quality of the solder joint towards a crack and pore-free solder seam 4 is improved.

The UV radiation, which preferably first comes into action, becomes the zinc coatings of the steel sheets 2 strongly absorbs and heats the zinc protective layers and promotes the transfer of energy, preferably subsequent to incident infrared radiation components on these zinc surfaces while forwarding the heat energy to the underlying steel sheets 2 , In the metal lattices of the steel sheets 2 occurring lattice vibrations generate heat in the steel sheets 2 and promote the coupling of the laser radiation in the soldering process while melting the solder material 5 , wherein at the same time the formation of adhesive bonding forces and diffusion processes between solder and base material (steel sheets 2 is transported. In the figure, these edge areas for Flankenerwärmung the flanged seam 3 both in the reading head 1 Leading area as well as in the already soldered area designated 13, while UV / IR heating / melting areas are designated 14 in a solder diffusion zone.

The light source heads 10 . 11 which are preferably high power mixed light emitters, preferably at least two standard light radiation sources 15 . 16 with incoherent radiation components, are preferably arranged in a cooled reflector chamber, which may be preceded by lens optics for combining or focusing the electromagnetic radiation. This is not shown in detail in the figure. Spotlight and / or line radiation preferably emerges from the reflector chamber; at the same time, the reflector chamber also serves to supply protective gases into the respective radiation area for protection against oxidizing atmosphere, for heat mass transport onto the steel sheets 2 or the Lötnahtbereich and for cooling the light radiation sources 15 . 16 even.

It should be pointed out here only in addition, that in this embodiment, the process laser beam 7 as well as the secondary laser beams 8A and 8B from a substantially laminar inert gas atmosphere 17 are surrounded. The protective gas jacket with the UV and IR radiation of the light source heads 10 . 11 are surrounded in the figure with 18 designated.

In the present embodiment, the reflector chambers are at an angle of about 30 ° to 45 ° to the process laser beam 7 Such an angular range can also apply to the resultant of the infrared or ultraviolet radiation, this arrangement of the reflector chambers with the protective gas flow emerging from the same 18 preferably a flow of inflowing or inflowing heat on the surface of the steel sheets 2 in the area of the solder seam 4 causes.

An advantageous direct cooling of the reflector chambers can be done to minimize the size of the same preferably by a heat pipe (heat pipe). Overall, the structural design, eg by arranging the light source heads 10 and 11 in a common housing, possibly also in a common housing with the laser head 1 (or one of the light source heads 10 . 11 with the laser head 1 ) such that the laser beam soldering device 100 small-sized, space-saving, inexpensive, robust, low-wear and easy to mount to complement existing laser beam systems.

The vorerläuterte solution can also be used for laser welding processes to achieve in thick-walled components, an additional heating of the seam flanks of the base materials or thin sheet metal <1mm form a wider heat input zone and in this way to achieve a "gentler" cooling of the weld seams, at the same coarse grain formations minimize and allow a reduction in laser power.

Claims (18)

Method for integrally joining, in particular laser steel brazing or laser beam welding, metallic materials, in particular of surface-coated materials, such as metal or metal oxide coated materials by means of at least one laser beam source, characterized by an upstream and / or downstream of a laser beam melting of a filler material (5) and / or adjacent Seam flank regions of a base material (2) pre-heating and / or reheating by means of short-wave and / or long-wave electromagnetic radiation. Method according to Claim 1 , characterized by an irradiation of ultraviolet and / or infrared radiation. Method according to Claim 1 or 2 , characterized in that an irradiation of ultraviolet and / or infrared waves simultaneously with the laser beam melting of the additional material (5) upstream and / or downstream of the laser beam source (1). Method according to at least one of the preceding Claims 1 - 3 , characterized in that at least the Laserstrahlaufschmelzung of the additional material (5) takes place in a protective gas atmosphere. Method according to at least one of the preceding Claims 1 - 4 , characterized in that the irradiation of electromagnetic waves takes place from a cooled reflector chamber. Method according to at least one of the preceding Claims 1 - 5 , characterized in that the short-wave electromagnetic radiation has wavelengths of about up to <= 400 nm and the long-wave electromagnetic radiation wavelengths of about> = 780 nm, in particular a mixing ratio between short-wave and long-wave radiation proportions freely selected, in particular adjustable is selected , Method according to at least one of the preceding Claims 1 - 6 , characterized in that the pre- and / or reheating of the solder material and / or the base material is effected by means of a mixture of short-wave and long-wave electromagnetic radiation, in particular this mixture has radiations with wavelengths of about <= 400nm and> = 780 nm. Device for bonded connection, in particular laser beam brazing or laser beam shearing, metallic materials, in particular of surface-coated materials, such as metal or metal oxide coated materials by means of at least one laser beam source, in particular for performing the method according to at least one of the preceding Claims 1 - 7 , characterized by at least one tempering radiation source (10, 11) for short-wave and / or long-wave electromagnetic radiation, arranged upstream and / or downstream of the laser beam source (1). Device after Claim 8 , characterized in that the tempering radiation source (10,11) is an incoherent radiation source, in particular for irradiation of a mixture of ultraviolet and infrared radiation. Device according to at least one of the preceding Claims 8 or 9 , characterized in that at least one tempering radiation source (10) upstream of the laser beam source (1) and at least one tempering radiation source (11) downstream of the laser beam source (1) is arranged. Device according to at least one of the preceding Claims 8 - 10 , characterized in that the at least one tempering radiation source (10) and the laser beam source (1) or a plurality of tempering radiation sources (10,11) or the plurality of tempering radiation sources (10, 11) including the laser steel source (1) are arranged in a common housing. Device according to at least one of the preceding Claims 8 - 11 , characterized in that the tempering radiation source (10,11) at least one radiation source (15) for ultraviolet radiation and a radiation source (16) for infrared radiation in a common housing, in particular a reflector chamber having. Device according to at least one of the preceding Claims 8 - 12 , characterized in that the tempering radiation source (10,11) has a radiation source for visible light, in particular for electromagnetic waves in the range of about 400nm to 780nm. 15 device according to one of the preceding Claims 8 - 13 , characterized in that at least one tempering radiation source (10,11) with respect to the laser beam source (1) and to be connected, in particular to be soldered base material (2) on the same side as the laser beam source (1) or on a reference is arranged on the base material opposite side of the laser beam source. Device according to at least one of the preceding Claims 8 - 14 , characterized in that a housing containing the laser beam source is connected to a protective gas source for supplying a protective gas to a laser beam emitted from the laser beam source laser beam and / or the tempering radiation source is arranged in a cooled reflector chamber, which is preceded by a lens optics, for collimation or bundling the electromagnetic radiation emitted by the tempering radiation source. Device after Claim 15 , characterized in that the reflector chamber is connected to a protective gas source for supplying a protective gas to this and the electromagnetic radiation emitted therefrom and / or the reflector chamber and / or a protective gas flow exiting therefrom and / or the emitted electromagnetic radiation at a resulting angle in the Range of about 30 ° to 45 ° to a, a soldering seam forming laser beam of the laser beam source is arranged. Device according to at least one of the preceding Claims 15 or 16 , characterized in that the reflector chamber is cooled directly by a heat pipe connected to this (heat pipe). Device according to at least one of the preceding Claims 8 - 17 , characterized in that the laser beam source comprises a laser head (1) with a laser beam (7) or a plurality of mono- or multifocal laser beams (7, 8A, 8B)), in particular the laser beam source is a multi-focal laser head, preferably the laser beam source one monochrome, coherent main laser beam (7) and at least one, in particular two monochromatic, coherent secondary laser beams (8A, 8B) emitted.

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