High Toughness Weld Metals With Superior Ductile Tearing Resistance

• US 20130292362A1
• Filed: 12/12/2011
• Published: 11/07/2013
• Est. Priority Date: 01/28/2011
• Status: Active Grant

• Current Assignee: Adnan Ozekcin, Douglas P. Fairchild, Hyun-Woo Jin, Mario L. Macia, Nathan E. Nissley, Raghavan Ayer, Steven J. Ford
• Original Assignee: Adnan Ozekcin, Douglas P. Fairchild, Hyun-Woo Jin, Mario L. Macia, Nathan E. Nissley, Raghavan Ayer, Steven J. Ford
• Inventors: Fairchild, Douglas P., Macia, Mario L., Ford, Steven J., Ayer, Raghavan, Jin, Hyun-Woo, Ozekcin, Adnan, Nissley, Nathan E.
• Granted Patent: US 9,821,401 B2
• Time in Patent Office: Days
• US Class Current: 219/74
• CPC Class Codes: B23K 2103/04 Steel or steel alloys
• CPC Class Codes: B23K 33/004 Filling of continuous seams
• CPC Class Codes: B23K 35/3053 Fe as the principal constituent
• CPC Class Codes: B23K 35/3066 with Ni as next major constituent
• CPC Class Codes: B23K 9/0213 Narrow gap welding
• CPC Class Codes: B23K 9/173 and of a consumable electrode
• CPC Class Codes: C22C 1/02 by melting C22C1/1036 takes precedence

Abstract

Weld metals and methods for welding ferritic steels are provided. The weld metals have high strength and high ductile tearing resistance and are suitable for use in strain based pipelines. The weld metal contains retained austenite and has a cellular microstructure with cell walls containing lath martensite and cell interiors containing degenerate upper bainite. The weld metals are comprised of between 0.02 and 0.12 wt % carbon, between 7.50 and 14.50 wt % nickel, not greater than about 1.00 wt % manganese, not greater than about 0.30 wt % silicon, not greater than about 150 ppm oxygen, not greater than about 100 ppm sulfur, not greater than about 75 ppm phosphorus, and the balance essentially iron. Other elements may be added to enhance the properties of the weld metal. The weld metals are applied using a power source with current waveform control which produces a smooth, controlled welding arc and weld pool in the absence of CO₂ or oxygen in the shielding gas.

Claims

1. A weld metal for ferritic steel base metals, comprising:

between 0.02 and 0.12 wt % carbon;

between 7.50 and 14.50 wt % nickel;

not greater than about 1.00 wt % manganese;

not greater than about 0.30 wt % silicon;

not greater than about 150 ppm oxygen;

not greater than about 100 ppm sulfur;

not greater than about 75 ppm phosphorus; and

the balance iron,

wherein the weld metal comprises retained austenite and further comprises a cellular microstructure comprising cell walls and cell interiors wherein the cell walls are harder than the cell interiors and said weld metal is applied using a gas metal arc welding process with pulsed waveform power supply.

2. The weld metal of claim 1 wherein the weld metal further comprises between 0.5 and 10 vol. % retained austenite.

3. The weld metal of claim 2 wherein the weld metal has a tensile strength greater than 110 ksi and R-curve toughness higher than a curve represented by a delta value greater than 1.0.

4. The weld metal of claim 3 wherein 50 or more percent of the volume of the cell walls comprises lath martensite and 20 or more percent of the volume of the cell interiors comprises degenerate upper bainite.

5. The weld metal of claim 4 further comprising at least one of the following:

not greater than about 0.30 wt % copper,

not greater than about 0.04 wt % vanadium,

not greater than about 0.30 wt % chromium,

not greater than about 0.40 wt % molybdenum,

not greater than about 0.04 wt % niobium,

not greater than about 0.02 wt % titanium,

not greater than about 0.02 wt % zirconium,

not greater than about 20 ppm boron.

6. The weld metal of claim 4 wherein said weld metal is applied using a shielding gas comprising helium and argon.

7. The weld metal of claim 6 wherein said shielding gas comprising helium and argon is substantially oxygen free.

8. The weld metal of claim 7 wherein said helium comprises 25 or more volume percent of said shielding gas.

9. A weld metal for ferritic steel base metals, comprising:

between 0.02 and 0.12 wt % carbon;

between 7.50 and 14.50 wt % nickel;

not greater than about 1.00 wt % manganese;

not greater than about 0.30 wt % silicon;

not greater than about 100 ppm sulfur;

not greater than about 75 ppm phosphorus; and

the balance iron,

wherein the weld metal has a tensile strength greater than 110 ksi and R-curve toughness higher than a curve represented by a delta value greater than 1.0;

the weld metal comprises between 0.5 and 10 vol. % retained austenite and further comprises a cellular microstructure comprising cell walls and cell interiors wherein 50 or more percent of the volume of the cell walls comprises lath martensite and 20 or more percent of the volume of the cell interiors comprises degenerate upper bainite and the cell walls are harder than the cell interiors; and

said weld metal is applied using a gas metal arc welding process with pulsed waveform power supply and a shielding gas comprising helium, argon, and CO₂ wherein helium comprises 25 or more volume percent of said shielding gas and CO₂ comprises not greater than 3 volume percent of said shielding gas.

10. A method of welding ferritic steel pipelines comprising:

determining a desired HSW weld metal chemistry comprising between 0.02 and 0.12 wt % carbon, between 7.50 and 14.50 wt % nickel, not greater than about 1.00 Wt % manganese, not greater than about 0.30 wt % silicon, not greater than about 150 ppm oxygen, not greater than about 100 ppm sulfur, not greater than about 75 ppm phosphorus, and the remainder essentially iron,

determining a welding consumable wire chemistry from a calculation using as inputs a pipeline base metal chemistry and a desired weld metal chemistry,

welding the pipeline base metal using the welding consumable wire, further comprising the steps of;

controlling the weld pool oxygen content to achieve a target weld metal oxygen content that is not greater than about 150 ppm oxygen, and

controlling the weld pool characteristics and arc stability during welding to provide satisfactory weldability.

11. The method of claim 10 wherein the step of welding the pipeline base metal comprises a gas metal arc welding process with pulsed waveform power supply, the step of controlling the weld pool oxygen content comprises a welding shielding gas substantially free of oxygen or CO₂, and the step of controlling the weld pool flow characteristics and arc stability comprises welding current waveform control sufficient to provide satisfactory weldability.

13. The method of claim 11 wherein the weld metal further comprises at least one of the following:

not greater than about 0.30 wt % copper,

not greater than about 0.04 wt % vanadium,

not greater than about 0.30 wt % chromium,

not greater than about 0.40 wt % molybdenum,

not greater than about 0.04 wt % niobium,

not greater than about 0.02 wt % titanium,

not greater than about 0.02 wt % zirconium,

not greater than about 20 ppm boron.

14. The method of claim 11 wherein the welding shielding gas comprises helium and argon.

15. The method of claim 14 wherein helium comprises 25 or more volume percent of said shielding gas.

16. The method of claim 10 wherein the step of welding the base metal comprises hybrid laser arc welding.

17. The method of claim 10 wherein the step of welding the base metal comprises submerged arc welding

18. The method of claim 10 wherein the step of welding the base metal comprises Tip TIG welding.

19. The method of claim 10 wherein the step of mitigating the viscosity of the weld metal comprises weld pool agitation.

12. A method of welding ferritic steel pipelines comprising:

determining a desired HSW weld metal chemistry comprising between 0.02 and 0.12 wt % carbon, between 7.50 and 14.50 wt % nickel, not greater than about 1.00 Wt % manganese, not greater than about 0.30 wt % silicon, not greater than about 100 ppm sulfur, not greater than about 75 ppm phosphorus, and the remainder essentially iron,

determining a welding consumable wire chemistry from a calculation using as inputs a pipeline base metal chemistry and a desired weld metal chemistry,

welding the pipeline base metal using the welding consumable wire and a gas metal arc welding process with pulsed waveform power supply, further comprising the steps of;

controlling the weld pool oxygen content comprising a welding shielding gas comprising not greater than 3 volume percent of CO₂ to achieve a target weld metal oxygen content, and

controlling the weld pool characteristics and arc stability during welding with welding current waveform control sufficient to provide satisfactory weldability.