Method to improve the characteristics of a root pass pipe weld

Patent metadata

Field	Value
Publication number	US-9415458-B2
Application number	US-41471209-A
Country	US
Kind code	B2
Filing date	Mar 31, 2009
Priority date	Sep 26, 2007
Publication date	Aug 16, 2016
Grant date	Aug 16, 2016

Abstract

A method and a system for forming a root pass weld for a root pipe joint. A substantially periodic electric welding waveform is generated and a series of electric arc pulses are generated between an advancing welding electrode and a root pipe joint in response to the electric welding waveform. The electric welding waveform includes a base cycle having a background current phase providing a background current level, a peak current phase providing a peak current level, a tail-out current phase providing a decreasing tail-out current level, and at least one heat-increasing current pulse during the background current phase providing a heat-increasing current level being above the background current level.

First claim

What is claimed is:

1. A method of forming a root pass weld for a root pipe joint, said method comprising:
generating a substantially periodic electric welding waveform using a welding power source; and
generating a series of electric arc pulses between an advancing welding electrode and a root pipe joint in response to said electric welding waveform, wherein said electric welding waveform includes:
a base cycle having a background current phase providing a background current level, a peak current phase providing a peak current level, and a tail-out current phase providing a decreasing tail-out current level, and
at least one heat-increasing current pulse during said background current phase providing a heat-increasing current level being above said background current level.

2. The method of claim 1 wherein said electric welding waveform further includes a pinch current phase between said background current phase and said peak current phase providing an increasing pinch current level.

3. The method of claim 1 wherein a resultant hardness of said root pass weld is less than or equal to a value of 248 HV 10.

4. The method of claim 1 wherein a resultant welding travel speed while forming said root pass weld is greater than or equal to 12 inches per minute.

5. The method of claim 1 wherein said root pipe joint is an open root joint.

6. The method of claim 1 wherein said root pipe joint is a closed root joint.

7. The method of claim 1 wherein said welding electrode comprises carbon steel.

8. The method of claim 1 wherein said welding electrode comprises a nickel alloy.

9. The method of claim 1 wherein said welding electrode comprises a nickel-chromium-molybdenum alloy (e.g., Inconel 625).

10. The method of claim 1 wherein said method is part of a gas metal arc welding (GMAW) process using argon and CO 2 as shielding gases.

11. A system for forming a root pass weld for a root pipe joint, said system comprising:
means for generating a substantially periodic electric welding waveform; and
means for generating a series of electric arc pulses between an advancing welding electrode and a root pipe joint in response to said electric welding waveform, wherein said electric welding waveform includes:
a base cycle having a background current phase providing a background current level, a peak current phase providing a peak current level, and a tail-out current phase providing a decreasing tail-out current level, and
at least one heat-increasing current pulse during said background current phase providing a heat-increasing current level being above said background current level.

12. The system of claim 11 wherein said electric welding waveform further includes a pinch current phase between said background current phase and said peak current phase providing an increasing pinch current level.

13. The system of claim 11 wherein a resultant hardness of said root pass weld is less than or equal to a value of 248 HV 10.

14. The system of claim 11 further comprising means for providing a resultant welding travel speed, while forming said root pass weld, said resulting welding travel speed being greater than or equal to 12 inches per minute.

15. The system of claim 11 wherein said root pipe joint is an open root joint.

16. The system of claim 11 wherein said root pipe joint is a closed root joint.

17. The system of claim 11 wherein said welding electrode comprises carbon steel.

18. The system of claim 11 wherein said welding electrode comprises a nickel alloy.

19. The system of claim 11 wherein said welding electrode comprises a nickel-chromium-molybdenum alloy (e.g., Inconel 625).

20. The system of claim 11 wherein said system is a gas metal arc welding (GMAW) system using argon and CO 2 as shielding gases.

Assignees

• Doyle Thomas Edward
• Noel Clyde David
• Breaux Terry Louis
• Peters Steven R
• Lincoln Global Inc

Inventors

• Doyle Thomas Edward
• Noel Clyde David
• Breaux Terry Louis
• Peters Steven R

Classifications

• B23K2101/06

  Tubes · CPC title

• B23K9/0282

  for welding tube sections · CPC title

• B23K9/092 Primary

  characterised by the shape of the pulses produced · CPC title

• B23K2201/06

  Operations & Transport · mapped topic