DE102010005894A1 - Thermally joining and/or coating or thermally separating the workpieces having heat-sensitive coating, comprises restoring coating by thermally coating the coating material after thermally joining and/or coating or thermally separating - Google Patents

Abstract

The method for thermally joining and/or coating or thermally separating the workpieces (1), which have a heat-sensitive coating (2), comprises restoring the coating by thermally coating a coating material (3) after thermally joining and/or coating or thermally separating the workpieces. A part of the thermal energy introduced in the workpiece for joining and/or coating or separating or in the workpieces is used for thermally coating the coating material. Two workpieces are welded or soldered with one another with a connecting seam. A blind seam (6) is welded or soldered at the workpiece. The method for thermally joining and/or coating or thermally separating the workpieces (1), which have a heat-sensitive coating (2), comprises restoring the coating by thermally coating a coating material (3) after thermally joining and/or coating or thermally separating the workpieces. A part of the thermal energy introduced in the workpiece for joining and/or coating or separating or in the workpieces is used for thermally coating the coating material. Two workpieces are welded or soldered with one another with a connecting seam. A blind seam (6) is welded or soldered at the workpiece. The workpiece is thermally separated under the formation of a cutting edge by using a cutting torch, plasma cutter or laser. The coating material is directly thermally introduced on the workpiece or the workpieces after thermally joining and/or coating or separating in a time-delayed manner. A residual heat present in the workpiece or in the workpieces is used for the thermal coating of the coating material. The residual heat is supplemented by an external energy supply. An external energy is supplied by light arc (4), laser, resistance heating or heat radiation for thermally coating the coating material. The coating material is thermally introduced on the connecting seam, the blind seam or the cutting edge. The workpiece is a metallic component with a zinc-containing coating. A part of the zinc-containing coating damaged by thermally joining and/or coating or separating is restored by coating zinc-containing coating material.

Description

The present invention relates to a method for the thermal joining and / or coating or thermal cutting of workpieces having a heat-sensitive coating. In particular, the present invention relates to a method for thermal joining and / or coating or thermal separation of corrosion-protected, metallic components, in particular galvanized sheets, such as those used in motor vehicle construction.

Metallic components, in particular sheets, are protected against corrosion by coatings, for example zinc-containing coatings. When welding or soldering these coated components, the coating is at least damaged in the seam area, but usually completely destroyed. Corrosion protection in the seam area is therefore only limited after thermal joining at best, but usually no longer exists at all.

For example, when welding galvanized steel sheet, the zinc coating in the seam area is melted and evaporated, because the welding process temperature is several hundred degrees Celsius above the melting temperature of zinc. Effects such as the cathodic action of the zinc of the adjacent, undamaged coating areas can not protect the seam areas from corrosion, since the seam areas are generally several millimeters wide.

Without aftertreatment, the weld seam and thus the entire component is subject to corrosion, whereby it must be taken into account that due to the metallurgical peculiarities of the weld seam, welds are generally more susceptible to corrosion than the respective base material.

In order to reduce or avoid the corrosion problem mentioned above, developments to date have reduced the process temperatures during thermal joining, thereby minimizing the damage to the anticorrosive coatings. If the coating of a component has been damaged by thermal joining in the area of the joint seam, further solutions consist of coating the seam area with similar or non-similar coatings after joining.

For example, welded seams of galvanized steel sheets are subsequently coated with various methods after welding. So it is possible to apply a corrosion-protective coating by zinc dust paint or zinc-aluminum spray in a short time on the weld. Since the zinc layer thus applied does not chemically bond to the parent metal, the properties of the original zinc coating are not achieved.

Alternatively, for example, it is possible by hand plating to subsequently chemically bond a zinc layer to the base material to provide better corrosion protection than when using zinc dust paints or zinc-aluminum sprays. However, this is generally associated with a very high technological and time expenditure.

It is therefore an object of the present invention to provide a method for thermal joining and / or coating or thermal separation of workpieces in order to restore a low-cost equivalent destroyed by heat input coating.

According to the invention, this object is achieved by a method for thermal joining and / or coating or thermal separation of workpieces having a heat-sensitive coating, wherein after the thermal joining and / or coating or thermal separation, the coating is restored by thermal application of coating material.

Due to the thermal application of coating material equivalent properties as in the previously destroyed by heat input coating can be achieved. At the same time, the thermal application represents only a small additional technological effort compared to the previous thermal joining and / or coating or thermal cutting.

Preferably, at least a portion of the thermal energy introduced for joining and / or coating or separating into the workpiece or into the workpieces is used for thermal application of the coating material. Thus, the preferred method is very cost effective because the workpiece (s) need not be heated, or only slightly heated, to thermally apply the coating material.

Preferably, at least two workpieces are thermally connected to one another with a connecting seam, preferably welded together or soldered together.

Likewise, it is also possible that a blind seam is thermally applied to at least one workpiece, preferably welded or soldered.

Also preferably, at least one workpiece is thermally separated to form at least one cutting edge, preferably by means of a cutting torch, plasma cutter or laser.

In particular, it is advantageous if the coating material is applied thermally immediately after the thermal joining and / or coating or thermal cutting on the workpiece or workpieces, preferably only used in the workpiece or in the workpieces residual heat for the thermal application of the coating material becomes. As a result, the thermal application of the coating material is particularly cost-effective, since no additional heating is necessary.

Alternatively, it is advantageous that the coating material is thermally applied after the thermal joining and / or coating or thermal cutting on the workpiece or workpieces, preferably for the thermal application of the coating material, the residual heat present in the workpiece or in the workpieces by external Energy supply is supplemented.

Preferably, energy is supplied externally to the thermal deposition of the coating material by an arc, by a laser, by resistance heating or by heat radiation.

Preferably, the coating material is applied thermally to the connecting seam, the blind seam or the cut edge.

In particular, it is advantageous if the workpiece is a metallic component with a zinc-containing coating or the workpieces are metallic components with zinc-containing coatings, and a part of the zinc-containing coating destroyed by the thermal joining and / or coating or thermal separation by thermal application of zinc-containing coating material is restored. As a result, a uniform corrosion protection is achieved in the said components.

The present invention will be described below in terms of preferred embodiments in conjunction with 1 explained in more detail.

1 shows a preferred embodiment of a method for thermal joining and / or coating or thermal cutting of workpieces.

In 1 is a workpiece 1 shown at least on one of its surfaces with a heat-sensitive coating 2 is provided. For example, the workpiece may be 1 to act a metallic component, such as a steel sheet. Preferably, such steel sheets are used in the automotive industry. In the heat-sensitive coating 2 it may be, for example, a zinc-containing coating that has been applied to the steel sheet, for example by means of hot-dip galvanizing.

In the illustrated embodiment is only a single workpiece 1 shown with a heat-sensitive coating 2 is coated. On the surface of the workpiece 1 that with the heat-sensitive coating 2 is provided, for example, a seam 6 as a blind seam by a thermal joining method, for example by welding or soldering applied. The order of such a blind seam can also be done in the context of a coating process.

However, it is also possible that several workpieces 1 that with heat-sensitive coatings 2 are provided, are joined together to form a connecting seam. The thermal joining is preferably carried out by welding or soldering.

It is also possible that at least one with a heat-sensitive coating 2 provided workpiece 1 is divided by a thermal separation process to form at least one cutting edge. In such thermal separation processes, for example, a cutting torch, a plasma cutter or a laser are used.

The three aforementioned methods have in common that by introducing thermal energy into the workpiece 1 the heat-sensitive coating 2 at least partially destroyed.

Generally, therefore, is a heat-sensitive coating 2 spoken when the evaporation temperature of the coating 2 below the process temperature of the thermal joining and / or coating or the thermal separation of the affected workpiece 1 of the affected workpieces 1 lies.

For example, when welding galvanized steel sheet metal, the process temperature for the welding process above 1536 ° C settled in order to melt at the metal joint the adjacent sheet metal areas and initiate the joining process. By contrast, the zinc of the zinc coating has a melting temperature of 419 ° C. and already evaporates at 907 ° C., ie far below the process temperature required for welding the steel sheets. Thus, in general Welding of galvanized steel sheet metals assumes that almost the complete zinc coating is vaporized near the welding zone, ie that the heat input no longer protects against corrosion of the welded steel sheets near the cooled weld seam.

After the thermal joining and / or coating or thermal separation, the heat-sensitive coating 2 will restore coating material 3 applied thermally in the seam area or cut edge area, where the heat-sensitive coating 2 previously destroyed by the heat input during joining, coating or separation.

Preferably, at least part of this is used for joining and / or coating or separating into the workpiece 1 or the workpieces 1 introduced thermal energy for thermal application of the coating material 3 used.

In the illustrated embodiment, the seam 6 as a blind seam by means of an arc 4 on the with the heat-sensitive coating 2 provided workpiece 1 applied. For this purpose, the burner head of a welding torch at a certain distance over the coated surface of the workpiece 1 moves, taking the arc 4 between a consumable as filler material electrode and the workpiece 1 formed. Due to the high temperature of the arc 4 becomes the workpiece 1 melted at the weld, and together with the consumable electrode material forms the seam 6 in the illustrated embodiment as a blind seam.

On the one hand, it is possible for the burner head over the coated surface of the workpiece 1 to move. On the other hand, it is also possible to keep the burner head stationary and the workpiece 1 to move under the burner head. Also a superposition of a movement of the burner head and a movement of the workpiece 1 is possible.

Based on the relative movement between the burner head and the workpiece 1 solidifies the molten material of the workpiece 1 and the molten electrode material behind the burner head in the region of the reference numeral 5 , The reference number 5 therefore represents an area of fresh suture 6 in which the suture material (workpiece material and possibly additions of the electrode) is already solidified, but in comparison to the adjacent areas of the workpiece 1 still has a much higher temperature, the amount of which is sufficient to the coating material 3 to melt, but not to evaporate.

Thus, it is particularly advantageous if the coating material 3 immediately after thermal joining and / or coating or thermal cutting on the workpiece 1 or the workpieces 1 is applied thermally. In the illustrated embodiment, preferably only in the workpiece 1 or in the workpieces 1 existing residual heat for the thermal application of the coating material 3 used.

For this example, a wire feed can be installed directly on the welding torch, so that a mechanically promoted zinc wire as a coating material 3 directly behind the arc 4 continuously on the cooling seam 6 and when in contact with the still hot suture in the already frozen seam area 5 melts. However, in addition to the previously described wire feed, it is also possible, for example, for the feed of the coating material 3 manually or by a device separate from the welding torch.

The liquid zinc wets the bright metal areas of the workpiece 1 or the workpieces 1 so that an immediate, continuous, thermal galvanizing of the damaged areas takes place. Ideally, the zinc-containing coating 2 of the workpiece 1 or the workpieces 1 completely restored after welding.

In particular, in inert gas welding, it is advantageous if the supply of the coating material 3 also under protective gas, especially if the solidified, but still warm seam area 5 to immediate corrosion tends. For this purpose, preferably, the supply of the coating material 3 such that the coating material 3 within the between the burner head and the workpiece 1 trained inert gas cone on the solidified, but still warm seam area 5 meets and is melted there by the residual heat.

Alternatively, however, it is also possible that the coating material 3 not immediately, but after a time delay after the thermal joining and / or coating or thermal separation on the workpiece 1 or the workpieces 1 is applied thermally.

Preferably, this is for the thermal application of the coating material 3 those in the workpiece 1 or in the workpieces 1 Existing residual heat supplemented by external energy supply. Such a supplementary, external energy supply can be done for example by means of an arc or by means of a laser. However, it is also possible that external energy for thermal application of the coating material 3 is additionally supplied by resistance heating or by thermal radiation.

In the alternative methods described above, the composition has the restored coating 7 preferably the same composition as the originally-existing and destroyed heat-sensitive coating 2 of the workpiece 1 , However, it is also possible that the recovered coating 7 one of the original on the workpiece 1 applied, heat-sensitive coating 2 has different composition.

Although only the arc welding and inert gas welding have been mentioned as preferred embodiments before, the restoration of the coating is 2 by thermal application in other welding processes, such. B. resistance welding or plasma welding possible.

Likewise it is possible the coating 2 by thermal application of coating material 3 restore after the workpieces 1 have been soldered. Unlike welding, soldering does not melt the workpieces 1 in the joint area, however, the soldering temperature is still high enough to cover the coatings 2 the workpieces 1 in the area of the soldering zone.

The previous explanations apply equally to thermal separation processes, with an added aspect in thermal cutting that not only is the heat-sensitive coating 2 on the existing surfaces of the workpiece 1 is destroyed in the region of the cutting edge, but that by the cut itself an uncoated, exposed workpiece surface is newly formed (the flanks of the cutting edge), which must be protected from environmental influences, especially corrosion. Again, this is possible with the aforementioned method by utilizing the residual heat remaining in the cutting edge from the thermal separation process.

Although the aforementioned embodiments relate essentially to metallic components, the technical teaching can be applied, for example, to other materials to be thermally bonded or thermally separated, which are provided with a heat-sensitive coating. For example, coated plastics, in particular thermoplastics, may be mentioned here.

With regard to the possible heat-sensitive coatings 2 of the workpiece 1 / the workpieces 1 they do not necessarily have corrosion-inhibiting properties, but may, for example, also have surface-active properties, for example in the form of nanoparticles. The same applies equally to the restoration of the coating 2 to be applied coating material 3 ,

The present embodiments may be applied in all fields where heat-sensitive coatings are used 2 provided workpieces 1 thermally joined or separated and in which it is necessary to restore the coating properties after thermal joining or separation.

A major field of application is the metalworking industry, where galvanized steel sheets are welded. Preferably, the workpieces 1 metallic components with a preferably zinc-containing coating 2 caused by thermal application of zinc-containing coating material 3 is restored. Thus, the corrosion protection of the metallic component again reaches the initial level without an additional manufacturing step, eg. B. a separate coating step, is necessary.

The preceding embodiments relate to a method for the thermal joining and / or coating or thermal cutting of workpieces 1 containing a heat-sensitive coating 2 in which, after the thermal joining and / or coating or thermal separation, the coating 2 by thermal application of coating material 3 is restored.

Claims (10)

Method for thermal joining and / or coating or thermal cutting of workpieces ( 1 ), which is a heat-sensitive coating ( 2 ), characterized in that after the thermal joining and / or coating or thermal separation, the coating ( 2 ) by thermal application of coating material ( 3 ) is restored. A method according to claim 1, characterized in that at least a part of the joining and / or coating or cutting into the workpiece ( 1 ) or in the workpieces ( 1 ) introduced thermal energy for thermal application of the coating material ( 3 ) is being used. Method according to claim 1 or 2, characterized in that at least two workpieces ( 1 ) are thermally connected to each other with a connecting seam, preferably welded together or soldered together. Method according to claim 1 or 2, characterized in that at least one workpiece ( 1 ) a blind seam ( 6 ) is applied thermally, preferably welded or soldered. Method according to claim 1 or 2, characterized in that at least one workpiece ( 1 ) is thermally separated to form at least one cutting edge, preferably by means of a cutting torch, plasma cutter or laser is separated. Method according to at least one of claims 1 to 5, characterized in that the coating material ( 3 ) immediately after the thermal joining and / or coating or thermal separation on the workpiece ( 1 ) or the workpieces ( 1 ) is applied thermally, preferably only in the workpiece ( 1 ) or in the workpieces ( 1 ) residual heat for the thermal application of the coating material ( 3 ) is being used. Method according to at least one of claims 1 to 5, characterized in that the coating material ( 3 ) offset in time after the thermal joining and / or coating or thermal separation on the workpiece ( 1 ) or the workpieces ( 1 ) is applied thermally, wherein preferably for the thermal application of the coating material ( 3 ) in the workpiece ( 1 ) or in the workpieces ( 1 ) existing residual heat is supplemented by external energy supply. A method according to claim 7, characterized in that for the thermal application of the coating material ( 3 ) is supplied externally by an electric arc, by a laser, by resistance heating or by heat radiation. Method according to at least one of claims 3 to 8, characterized in that the coating material ( 3 ) on the connecting seam, the blind seam ( 6 ) or the cutting edge is applied thermally. Method according to at least one of claims 1 to 9, characterized in that the workpiece ( 1 ) a metallic component with a zinc-containing coating ( 2 ), or the workpieces ( 1 ) metallic components with zinc-containing coatings ( 2 ), and a part of the zinc-containing coating destroyed by the thermal joining and / or coating or the thermal separation ( 2 ) by thermal application of zinc-containing coating material ( 3 ) is restored.

Images