Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
  • B23K26/03—Observing, e.g. monitoring, the workpiece
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
  • B23K26/035—Aligning the laser beam

Definitions

• the present invention relates to a method and a device for testing the weld seam of a weld connection made in the butt joint by deep welding with a laser beam.
• tailored blanks Usage-tailored and welded sheet metal parts, so-called "tailored blanks", are being used increasingly in particular in the automotive industry. On the one hand, savings in raw material can be achieved and process planning and execution can be simplified.
• Such "tailored blanks” are made by laser welding in the butt joint. The edges of two complementarily cut sheet metal parts are butted against each other, fixed with a clamping device and passed through a welding station equipped with a laser. In particular, high-power lasers are used for this, with which deep welding can be carried out.
• welding plane which is spanned by the weld seam and the laser beam.
• the stability and thus the quality of the weld seam of the depth welding process depends on numerous parameters, for example the welding speed, the properties of the laser and the properties of the workpieces, especially the edge surface and the edge course.
• the gas dynamic conditions ie the type of supply of the process gas, the extraction of the welding smoke and the ventilation of the laser beam tube are of considerable importance. All of these parameters are in a complex and unstable equilibrium during the welding process.
• a disturbance in the equilibrium position due to accidental changes in the influencing variables can lead to a brief interruption of the deep welding and irregular ejection of the melt from the welding bath.
• the locally missing metal is replenished by the liquid welding bath.
• drop-like material deposits can extend over the entire width of the weld seam in a length of 0.5 mm to 5 mm and have a height of approximately 1 mm. Since this ejected and deposited material no longer flows back into the welding capillary, a crater, a furrow or a gap forms in the weld seam before such a drop-like deposit.
• Such welding errors occur regularly when welding with high-power lasers and are generally not tolerated according to the specifications for the weld seam quality of welded connections with laser beam as defined in ISO 13919-1.
• the method disclosed in this document is based on the detection of the weld seam profile by means of an optical system. Evaluation devices can then assess whether the weld seam profile of the welded connection of sheet metal parts meets the quality requirements or not. With this method, welding profile measurements are carried out approximately every 15 mm.
• a method and a device are to be created with which welding defects, in particular craters, furrows, gaps and / or material accumulations along the weld seam can be detected in a simple manner and thus the fulfillment of the specifications mentioned in ISO 13919-1 can be checked.
• This object is achieved according to the invention with a method for welding seam testing in accordance with claim 1 and with a device with the features of claim 5.
• means are provided for detecting the welding errors mentioned in a butt joint by means of deep welding with a laser beam of sheet metal parts by means of which the weld seam height is continuously scanned along the weld seam. This means that craters, furrows and crevices as well as the material accumulations described above on the weld seam can be recorded.
• sampled height values are transmitted to a display and / or evaluation device.
• the evaluation device can compare the sampled values with the various quality levels of ISO 13919-1, display the exact positions of the welding defects and / or save the measured data.
• the method according to the invention is therefore characterized by an extremely simple measuring principle, which allows a simple device structure and is a reliable, uncomplicated and inexpensive method for welding seam inspection and detection of welding defects.
• a mechanically deflectable needle is provided, the deflection of which can be converted, for example, with the aid of piezo crystals into electrical signals.
• Figure 1 is a schematic view of a flawless weld.
• FIG. 3 shows a schematic view of a weld seam with crater formation
• Fig. 5 is a schematic representation of a preferred embodiment
• FIG. 1 schematically shows a weld seam 11 of a weld connection of two sheet metal parts 12 and 13 of different thickness which was made in the butt joint by deep welding with a laser beam.
• the weld seam width 14, the height Profile 15 perpendicular to the weld seam and the surface structure 16 along the weld seam depend on the welding parameters, such as the properties of the laser, the properties of the workpieces, in particular the edge surface, the edge course and edge preparation, as well as the thickness of the sheet edges and the welding speed - speed.
• the width of the weld seam 14 can vary from 0.3 to 1.3 mm.
• the weld seam 11 In the case of a welded connection of sheet metal parts that conforms to the standard, the weld seam 11 generally has a scale-like surface structure 16 whose variations in the weld seam height along the weld seam are in the range of a few hundredths of a millimeter, for example 0.02 mm.
• sheet metal part refers to metallic, preferably made of steel flatware, such as e.g. Metal strips, metal sheets or metal plates of any size, thickness and surface.
• the welded connection of sheet metal parts described here relates to a connection made by welding between two sheet metal edges, wherein the sheet metal edges can have different thicknesses and do not necessarily have to originate from two separate sheets, but can also belong to a previously rounded one-piece sheet metal, for example.
• butt joint is used here to denote the position of sheet metal parts whose sheet metal edges are butted and fixed against one another.
• welding seam height includes depressions as well as elevations of the weld seam.
• FIG. 2 shows schematically the situation at the location of the welding process.
• a high-power laser beam 21 strikes the sheet metal parts 22 and 23 to be welded (the latter not shown).
• the incident energy of the laser beam 21 leads to the melting of the sheet metal parts 22, 23 and forms a welding bath 27.
• the heat caused by the laser beam 21 generates a plasma 24 which forms a deep and narrow capillary 25 in the welding bath 27.
• the relative movement R of the laser beam 21 and sheet metal parts 22, 23 creates a zone 26 behind the weld pool 27 with solidified weld metal, which forms the weld seam. It can be seen from FIG.
• the liquefied metal 28 lying in front of the laser beam 21 switches to the rear side 29 of the laser beam 21 due to the relative movement R during the welding process and is preferably deposited on the top of the zone 26.
• the capillary 25 fills with liquid weld metal when the balance of the plasma 24 is disturbed, and therefore no or only a partial weld connection is established. If the laser beam 21 strikes an already existing welding bath 27, larger quantities of the liquid weld metal can be ejected explosively. These ejections are usually deposited behind the welding beam on the welding seam and can be clearly recognized as teardrop-shaped deformations.
• the weld seam 31 shown in FIG. 3 of a welded connection between two sheet metal parts 32 and 33 of the same thickness has a welding defect in the form of a crater 34, a drop-shaped material deposit 35 being located directly behind.
• craters also known as pinholes with a diameter of approx. 0.1 mm and more, can have different depths, typically do not extend over the entire width of the weld seam and are preferably located in the middle of the weld seam.
• the teardrop-shaped "material deposits 35" lead to weld seam elevations which can extend over the entire width of the weld seam and have a length of approximately 0.5 mm to approximately 5 mm and a height of several tenths of a millimeter. 8th
• the schematic view of a weld seam 41 shown in FIG. 4 between two sheet metal parts 42, 43 of the same thickness has a welding defect in the form of a weld seam gap 44, a drop-shaped material deposit 45 being located directly behind this column 44.
• Such weld seam gaps generally have a length of 0.05 to 0.2 mm and typically do not extend over the entire weld seam, but have a width of approximately 0.2 mm.
• the weld seam gaps 44 are often in the form of holes with a diameter of approximately 0.2 mm.
• the drop-shaped material deposits 45 lead to weld seam elevations which have a height of several tenths of a millimeter.
• FIG. 5 schematically shows a device for carrying out the method according to the invention.
• Optical means 54 are preferably used to scan the height of the weld seam along the weld seam 51 of a weld connection of two sheet metal parts 52, 53 with different thicknesses.
• these optical means 54 comprise three optical distance meters equipped with semiconductor lasers, which are preferably arranged at an inclination angle of 30 ° from the surface normal.
• a detector needle is used instead of the optical detectors, which is guided along the weld seam 51.
• the deflections of this detector needle can be converted into electrical signals with the aid of piezo crystals, which in turn are processed with corresponding threshold value circuits.
• the structure of these detectors is not part of the present invention and is not explained in detail here. What is essential for the selection of suitable detectors is their ability to detect height differences of the order of several tenths of a millimeter. tern safe and easy to determine. In particular, it should be possible to detect weld seam elevations of this magnitude.
• the advantages of the method according to the invention can be seen in the simplicity of the detection of welding defects - in particular by the sole detection of weld seam elevations - during deep welding with high-power lasers. In addition, the continuous scanning of the weld seam leads to a reliable detection of these welding errors.

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• Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Engineering & Computer Science (AREA)
• Plasma & Fusion (AREA)
• Mechanical Engineering (AREA)
• Laser Beam Processing (AREA)
• Investigating Materials By The Use Of Optical Means Adapted For Particular Applications (AREA)
• Length Measuring Devices By Optical Means (AREA)
• Length Measuring Devices With Unspecified Measuring Means (AREA)

Applications Claiming Priority (3)

Publications (1)

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Family Applications (1)

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• 1999
  • 1999-02-26 BR BR9908490-2A patent/BR9908490A/pt not_active Application Discontinuation
  • 1999-02-26 WO PCT/CH1999/000089 patent/WO1999044784A1/de not_active Application Discontinuation
  • 1999-02-26 CA CA002322531A patent/CA2322531A1/en not_active Abandoned
  • 1999-02-26 EP EP99904675A patent/EP1060051A1/de not_active Withdrawn
  • 1999-02-26 KR KR1020007009535A patent/KR20010041402A/ko not_active Application Discontinuation
  • 1999-02-26 RU RU2000124878/02A patent/RU2194601C2/ru active
  • 1999-02-26 CN CN99803519A patent/CN1291928A/zh active Pending
  • 1999-02-26 AU AU25087/99A patent/AU2508799A/en not_active Abandoned
  • 1999-02-26 JP JP2000534370A patent/JP2002505199A/ja active Pending

Non-Patent Citations (1)

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