METHOD AND DEVICE FOR PLASMA TAP HOLE WELDING

• US 20100133241A1
• Filed: 11/30/2009
• Published: 06/03/2010
• Est. Priority Date: 11/28/2008
• Status: Active Grant

• Current Assignee: Linde AG (Linde Plc)
• Original Assignee: Linde AG (Linde Plc)
• Inventors: Wilhelm, Gerald, Siewert, Erwan
• Granted Patent: US 8,461,476 B2
• Time in Patent Office: Days
• US Class Current: 219/121.460
• CPC Class Codes: B23K 10/006 Control circuits therefor circuits for plasma torches H05H1/36
• CPC Class Codes: B23K 10/02 Plasma welding
• CPC Class Codes: B23K 9/0953 using computing means
• CPC Class Codes: B23K 9/0956 using sensing means, e.g. optical
• CPC Class Codes: B23K 9/167 and of a non-consumable electrode
• CPC Class Codes: H05H 1/3494 Means for controlling discharge parameters
• CPC Class Codes: H05H 1/36 Circuit arrangements H05H1/38, H05H1/40 take precedence

Abstract

In connection with plasma tap hole welding, in which a plasma jet (7) directed towards a workpiece (8) to be welded is generated by means of a welding current applied onto an electrode (2) and a plasma gas, the plasma jet at least partly penetrating through the workpiece (9), wherein at least one electrical conductor (10, 50, 60, 61) is arranged at the exit side (8″) of the plasma jet (7), a penetration current (I_2′) being measured via the electrical conductor (10, 50, 60, 61), it is suggested that the penetration current (I₂) is actively modified during the welding process.

Claims

1. Method for plasma tap hole welding, wherein a plasma jet directed onto a workpiece to be welded is generated by means of a welding current applied to an electrode and a plasma gas, the plasma jet at least partly penetrating through the workpiece, wherein on the exit side of the plasma jet at least one electrical conductor is arranged, via which a penetration current (I₂) is measured, characterized in that the penetration current (I₂) is actively modified during the welding process.

2. Method according to claim 1, characterized in that the penetration current (I₂) is modified by means of variable electrical resistors by means of power switches and/or by a modification of the distance between the electrical conductor and the workpiece

3. Method according to claim 1, characterized in that the penetration current (I₂) is modified periodically, stepwise, continuously or in situ and/or by at least one further external current applied to it.

4. Method according to claim 1, characterized in that variable process parameters are derived on the basis of the measured penetration current (I₂), and the modification of the penetration current (I₂) is effected on the basis of the variable process parameters.

5. Method according to claim 4, characterized in that root penetration, gap or crack width and/or the edge offset of the welding joint are used.

6. Method according to claim 1, characterized in that further to the plasma gas a focusing gas, an inert or shielding gas and/or a forming gas are used, a gas or gas mixture selected from the group consisting of argon, helium, hydrogen, carbon dioxide, oxygen and mixtures hereof being used as plasma gas, focusing gas, inert or shielding gas and/or as forming gas.

7. Method according to claim 1, characterized in that at least one water cooled copper rail which is arranged in a forming gas rail, is used as at least one electrical conductor.

8. Method according to claim 1, characterized in that at least two electrical conductors are provided, and the penetration current (I₂) is conducted over the at least two electrical conductors.

15. Computer program with program code means for carrying out a method according to claim 1, when the computer program is executed on a computer, especially on a corresponding computer unit in a device according to claim 9.

9. Device for plasma tap hole welding comprising at least one electrode, onto which a welding current can be applied, and at least one nozzle for a plasma gas, whereby a plasma jet can be generated, and at least one electrical conductor wherein a workpiece to be welded can be arranged between the electrode and the conductor, as well as means for measurement of a penetration current between the electrode and the at least one electrical conductor characterized in that the device further comprises means for active modification of the penetration current (I₂).

10. Device according to claim 9, characterized in that the means for modification of the penetration current (I₂) are variable resistors, power switches and/or distance setting means for modification of a distance between the electrical conductor and the workpiece.

11. Device according to claim 9, characterized in that the device comprises at least one conductor rail, especially two conductor rails, and at least one electrical conductor.

12. Device according to claim 11, characterized in that the at least one conductor rail is part of at least one forming gas rail.

13. Device according to claim 12, characterized in that the device comprises a U-shaped forming gas rail, the open side of which being directed towards the exit side of the plasma jet and perpendicular hereto, and at least one water cooled copper rail is provided as at least one electrical conductor.

14. Device according to claim 13, characterized in that the U-shaped forming gas rail, the open side of which is directed towards the exit side of the plasma jet and which is arranged perpendicular hereto, comprises two water cooled copper rails as electrical conductors, which are separated by a non-conducting element, and further the sides of the U-shaped forming gas rail facing the exit side of the plasma jet comprise a non-conducting material.