METHOD AND DEVICE FOR SELF-REGULATED WELDING IN THE MANUFACTURE OF LONGITUDINALLY WELDED METAL TUBES

• US 3,573,416 A
• Filed: 09/24/1969
• Issued: 04/06/1971
• Est. Priority Date: 09/28/1968
• Status: Expired due to Term

• Current Assignee: Drechsler Guido
• Original Assignee: Drechsler Guido
• Inventors: DRECHSLER GUIDO
• Application Number:
  US04/860,681
• Time in Patent Office: 559 Days
• US Class Current: 219/608
• CPC Class Codes: B23K 13/02 Seam welding

Abstract

A method according to which the most important quantities in the manufacture of welded metal tubes, i.e. feeding speed of the metal band, upsetting pressure, intensity of the whole welding current, intensity of the so called back current, applied voltage and temperature of the welding seam, are continuously electrically measured and the measured values are correlated to each other obtaining a plurality of quotients which are compared with prefixed quotients corresponding to optimal welding conditions; the electrical value resulting from said comparison starts a self-regulating process of the concerned quantities in order to reach again said prefixed quotients.

Claims

1. A method of regulating welding in the manufacture of longitudinally welded metal tubes from a metal band comprising the steps of continuously measurIng the basic quantities of feeding speed of the band, active electric welding power, upsetting pressure and temperature of the welding seam;

electing one of said basic quantities as reference quantity;

converting the measured values into electric signals;

making ratios of the signals corresponding to each three basic quantities to the signal corresponding to said reference quantity for obtaining three quotient signals;

prefixing three limit signals for said ratios such as these give optimal welding results;

comparing each said quotient signals with the respective prefixed limit signal for obtaining three difference signals;

making the algebraic sum of said difference signals for obtaining a sum signal;

causing said sum signal to act on at least one of said three basic quantities until the suppression of said difference signals.

2. A method according to claim 1, wherein said sum signal is caused to act on the active electric welding power.

3. A method according to claim 1, wherein the temperature of the welding seam is measured by measuring the intensity of a secondary magnetic field induced by eddy currents generated by a primary magnetic field applied on the tube portion immediately downstream of the welding zone.

4. A method of regulating welding in the manufacture of longitudinally welded metal tubes from a metal band, comprising the steps of continuously measuring the values of feeding speed of the band, of the whole current delivered to the welding equipment, of the back current, of the voltage applied to the welding equipment, of the upsetting pressure and of the welding seam temperature;

converting the measured values into electric signals;

multiplying the signal corresponding to the applied voltage by the signal corresponding to the whole current and by the signal corresponding to the back current for obtaining a first product signal corresponding to the whole power and a second product signal corresponding to the back power respectively;

subtracting said second product signal from said first product signal for obtaining a signal corresponding to the active welding power;

making the ratio of the signal corresponding to the whole current to the signal corresponding to the feeding speed, the ratio of the signal corresponding to the active welding power to the signal corresponding to the upsetting pressure and the ratio of the signal corresponding to the welding seam temperature to the signal corresponding to the feeding speed for obtaining three quotient signals;

prefixing for each said quotient signals a limit signal such as to give optimal welding results;

comparing each said quotient signals with the respective limit signal such as to give optimal welding results;

comparing each said quotient signals with the respective limit signal for obtaining three difference signals;

making the algebraic sum of said difference signals for obtaining a sum signal;

causing said sum signal to act on the whole current until the suppression of said difference signals.

5. A method according to claim 3, wherein the back current is measured by determining the value of a magnetic field in the back of the tube opposite to the welding zone.

6. A method according to claim 3, wherein the welding seam temperature is measured by measuring the intensity of a secondary magnetic field induces by eddy currents generated by a primary magnetic field applied on the tube portion immediately downstream of the welding zone.

7. A device for regulating welding in the manufacture of longitudinally welded metal tubes from a metal band, comprising four measuring units each for the continuous electrical measure of the basic quantities of feeding speed of the band, active electric welding power, upsetting pressure and temperature of the welding seam respectively;

three dividing units each receiving as input the output signal of one of said measuring units, the output signal of the fourth of said measuring units being delivered as input to all said dividing units simultaneously;

three comparators eaCh connected to one of said dividing units and all connected in series to an adding unit, the input of each of said comparators being formed by the output signal of the connected dividing device and by a limit signal manually introducible in each comparator;

a regulating unit which receives the sum signal coming out from said adding unit and adapted to act on the feeder of one of said basic quantities until the output signals of said comparators are suppressed.

8. A device according to claim 7, wherein said unit measuring the active welding power comprises a subtracting unit which subtracts the signal corresponding to the back power from the signal corresponding to the whole power applied to the welding equipment, said signals being the output signals of two multipliers which multiply the applied voltage by the whole current or by the back current respectively, said back current being measured by means of a unit responsive to a magnetic field applied on the tube zone opposite to the welding zone.

9. A device according to claim 7, wherein said unit measuring the temperature of the welding seam comprises an excitation winding connected to a suitable power supply and coiled around the tube to be welded inducing therein eddy currents, and a secondary winding connected to a transductor the output of which is a signal corresponding to the seam temperature.

10. A device according to claim 7, wherein said measuring unit delivering its output signal to all said dividing units simultaneously is the unit measuring the feeding speed of the band.

11. A device according to claim 7, wherein said regulating device receiving the sum signal coming out from said adding unit acts on the power supply.

12. A device for regulating welding in the manufacture of longitudinally welded metal tubes from a metal band, comprising six measuring units each for the continuous electrical measure of the basic quantities of feeding speed of the band, whole current, back current, voltage applied to the welding equipment, upsetting pressure and temperature of the welding seam respectively;

a first multiplier which receives as input the output signals of the units measuring the whole current and the applied voltage respectively, the output signal of said first multiplier corresponding to the whole electric power applied to the welding equipment;

a second multiplier which receives an input the output signals of the units measuring the back current and the applied voltage respectively, the output signal of said second multiplier corresponding to the back power;

a subtracting unit which receives as input the output signals of said first and second multiplier and the output of which is a signal corresponding to the active welding power;

a first dividing unit which receives as input the output signals of the units measuring the whole current and the feeding speed respectively, the output signal of said first dividing unit corresponding to the quotient of these two basic quantities;

a second dividing unit which receives as input the output signals of said subtracting unit and of unit measuring the upsetting pressure, the output signal of said second dividing unit corresponding to the quotient of the active welding power to the upsetting pressure;

a third dividing unit which receives as input the output signals of the units measuring the welding seam temperature and the feeding speed respectively, the output signal of said third dividing unit corresponding to the quotient of these two basic quantities;

three comparators each connected to one of said dividing units and all connected in series to an adding unit, the input of each said comparators being the output signal of the dividing units connected thereto and by a limit signal manually introducible in each comparator;

a regulating unit which receives as input the sum signal coming out from said adding unit and is adapted to act on the whole current.