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Spot Weld Al Equipment

Spot Weld Al Equipment. Single-Phase AC Machines Without slope control With Slope control. Polyphase Direct-Energy Machines Frequency Converter Rectifier Type. Various Types of Equipment. Stored-Energy Machines Electromagnetic Type Electrostatic Type Electrochemical Type

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Spot Weld Al Equipment

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  1. Spot Weld Al Equipment

  2. Single-Phase AC Machines Without slope control With Slope control Polyphase Direct-Energy Machines Frequency Converter Rectifier Type Various Types of Equipment • Stored-Energy Machines • Electromagnetic Type • Electrostatic Type • Electrochemical Type • Home-Polar Type • Single-Phase DC Machines • - Rectified DC • - Medium Frequency DC

  3. Typical Current-Force Diagram for Single-Phase AC Type Machines Weld Time Postheat Time Weld Heat Time Hold Time Downslope Time Time Forge-Delay Time Upslope Time Squeeze Time Forge Force Postheat Current Initial Current Weld Force Welding Current [Reference: Resistance Welding Manual, p.11-21, RWMA]

  4. Machine Settings for Spot Welding Aluminum Alloys on Single-Phase Machines (Recommendations without Slope Control) [Reference: Resistance Welding Manual, p.11-14, RWMA]

  5. Recommended Weld Current with a Single-Phase AC Supply 70 60 Weld Current, kA 50 40 30 20 1 2 3 Material Thickness, mm

  6. Recommended Electrode Force with a Single-Phase AC Supply Electrode Force, kN Material Thickness, mm

  7. Effect of AC Conduction Angle on Electrode Life Lower Peak Currents 4.6 msec Longer Conduction Period DC 4.6 Longer Conduction Periods Allow more Uniform Heating & (Lower Peak Current) Without Long Cool Periods Between Half-cycles Increasing Electrode Life No Weld Cracking Partial Nuggets Weld Cracking Increase Electrode Life 4.6 Spinella, D, “Implications for Aluminum Resistance Spot Welding Using Alternating Current”, Materials & Body Testing, IBEC , 1995

  8. Single-Phase AC Machines Without slope control With Slope control Polyphase Direct-Energy Machines Frequency Converter Rectifier Type Various Types of Equipment • Stored-Energy Machines • Electromagnetic Type • Electrostatic Type • Electrochemical Type • Home-Polar Type • Single-Phase DC Machines • - Rectified DC • - Medium Frequency DC

  9. Spot Welding Schedule of Single-Phase Direct Current Machines [Reference: Resistance Welding Manual, p.11-23, RWMA]

  10. Recommended Welding Conditions with a Single-Phase DC Supply Electrode Force, kN Weld Time, cycles Weld Current, kA Material Thickness, mm

  11. Effect of DC Current on Electrode Life DC Results in Off Center Weld More Wear on One Electrode Electrode Face with Higher Operating Temperature Kumagai, M, High Performance Electrode Material… IBEC’95, Material & Body Testing, 1995

  12. Single-Phase AC Machines Without slope control With Slope control Polyphase Direct-Energy Machines Frequency Converter Rectifier Type Various Types of Equipment • Stored-Energy Machines • Electromagnetic Type • Electrostatic Type • Electrochemical Type • Home-Polar Type • Single-Phase DC Machines • - Rectified DC • - Medium Frequency DC

  13. Newton, et al, Fund of RW Aluminum, AWS, SMWC VI Oct 1994

  14. Comparison of 50-Hz AC and MFDC Waveforms Current (kA) MFDC AC 50 HZ Time (sec)

  15. AC Mid-Frequency DC Reduced Expulsion 61114-T4 Aluminum Michaud, E, A Comparison of AC & MFDC SMWC VII, AWS, 1996

  16. MF DC AC

  17. Increase Force Effect of Force and Gage on Lobe for MF DC As Increase Gage, Lobe Moves Browne, D., Model to Predict, IBEC’95, Adv Tech & Processes, 1995

  18. Effect of Electrode Tip Diameters on MFDC Browne, D., Model to Predict, IBEC’95, Adv Tech & Processes, 1995

  19. Effect of Weld Spacing in MFDC Browne, D., Model to Predict, IBEC’95, Adv Tech & Processes, 1995

  20. Effect of Deteriorated Tips with MFDC Browne, D., Model to Predict, IBEC’95, Adv Tech & Processes, 1995

  21. Single-Phase AC Machines Without slope control With Slope control Polyphase Direct-Energy Machines Frequency Converter Rectifier Type Various Types of Equipment • Stored-Energy Machines • Electromagnetic Type • Electrostatic Type • Electrochemical Type • Home-Polar Type • Single-Phase DC Machines • - Rectified DC • - Medium Frequency DC

  22. Typical Current-Force Diagram for Electrostatic Stored Energy Type Machines Forge-Delay Time Forge Force Weld Force Current Squeeze Time Hold Time Weld Time [Reference: Resistance Welding Manual, p.11-21, RWMA]

  23. Spot Welding Schedule of Electrostatic Stored Energy Machines [Reference: Resistance Welding Manual, p.11-23, RWMA]

  24. Single-Phase AC Machines Without slope control With Slope control Polyphase Direct-Energy Machines Frequency Converter Rectifier Type Various Types of Equipment • Stored-Energy Machines • Electromagnetic Type • Electrostatic Type • Electrochemical Type • Home-Polar Type • Single-Phase DC Machines • - Rectified DC • - Medium Frequency DC

  25. Insert diagram of Frequency Converter waveform

  26. Spot Welding Schedule of Typical Three-Phase Frequency Converter [Reference: Resistance Welding Manual, p.11-22, RWMA]

  27. Single-Phase AC Machines Without slope control With Slope control Polyphase Direct-Energy Machines Frequency Converter Rectifier Type Various Types of Equipment • Stored-Energy Machines • Electromagnetic Type • Electrostatic Type • Electrochemical Type • Home-Polar Type • Single-Phase DC Machines • - Rectified DC • - Medium Frequency DC

  28. Typical Current-Force Diagram for Three-Phase Rectifier Type Machines Forge-Delay Time Final Force Weld Time Postheat Current Welding Current Initial Force Postheat Time Hold Time Total Weld Time Squeeze Time [Reference: Resistance Welding Manual, p.11-20, RWMA]

  29. Spot Welding Schedule of Typical Three-Phase Direct Current Rectifier [Reference: Resistance Welding Manual, p.11-22, RWMA]

  30. SUMMARY

  31. Weld Current High current levels are required to break down the surface oxide and generate the heat necessary for developing an acceptable weld nugget Weld Time Require short weld time due to high current levels Upslope/Downslope Generally not recommended for welding aluminum alloys Electrode Design/Material Due to the required higher current levels, electrodes with high current capacity, such as Class 1 and Class 2, are commonly used Electrode designs have mainly been dome-shaped Electrode tips must also be dressed frequently Forging Forging cycles are commonly used to prevent weld cracking in aluminum alloys Process Parameters

  32. Surface Burning and Tip Pickup Cracks Excessive Indentation Sheet Separation Porosity Weld Metal Expulsion Unsymmetrical Weld Nugget Inclusion of Unwelded Weld Defects

  33. [Cause] Surface burning is caused by excessive heat on the metal surface under the electrode and is indicated by burned, pitted and discolored welds. Excessive electrode pickup is caused primarily by the same factors. [Remedy Those Conditions] Improper surface conditions Electrode skidding Improper Electrode Material - conductivity too low Dirty or improper cleaned electrodes Excessive “weld time” Excessive welding current Inadequate welding force Surface Burning and Tip Pickup

  34. [Cause] Internal and external cracks in welds, generally caused by improper thermal and pressure conditions, are observed in the weld structure and surface, respectively. [Remedy Those Conditions] Excessive penetration Insufficient force Improper rate of current rise Improper electrode cooling Improper electrode contour Delayed application of forging force Electrode skidding Cracks

  35. [Cause] Excessive indentation, generally caused by improper force application, is indicated by depression on the weld surface. [Remedy Those Conditions] Excessive force Weld metal expulsion Improper electrode contour Excessive surface heating Improper forging cycle Excessive Welding Current Excessive Indentation

  36. [Cause] Excessive sheet separation, generally caused by poor fitup of parts and excessive surface deformation, is indicated by a wide separation of the base metal adjacent to the weld. [Remedy Those Conditions] Excessive force Improper fitup of parts Weld metal expulsion Incorrect electrode contour Excessive welding current Tip misalignment Excessive “weld time” Sheet Separation

  37. [Cause] A porous weld structure, generally caused by improper application of heat and force, is observed by sectioning and etching the weld. [Remedy Those Conditions] Insufficient “weld time” Improper rate of current rise Improper electrode contour Incorrect sequencing of weld and forging force Insufficient force Porosity

  38. [Cause] Weld expulsion, generally caused by extreme heat and improper force, is indicated by expelled metal from the weld. [Remedy Those Conditions] Insufficient force Tip misalignment Erratic contact resistance Foreign substance at faying surface Electrode skidding Excessive welding current Excessive “weld time” Weld Metal Expulsion

  39. [Cause] Unsymmetrical welds, generally caused by unsymmetrical gauge combination, improper electrode contour, poor fitting workpiece or surface preparation, may be observed by sectioning the weld. [Remedy Those Conditions] Improper electrode contour Inadequate surface preparation Improper fitup of workpieces Electrode misalignment Electrode skidding Unsymmetrical Weld Nugget

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