High toughness weld metals with superior ductile tearing resistance

Patent metadata

Field	Value
Publication number	US-9821401-B2
Application number	US-201113997610-A
Country	US
Kind code	B2
Filing date	Dec 12, 2011
Priority date	Jan 28, 2011
Publication date	Nov 21, 2017
Grant date	Nov 21, 2017

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 CO 2 or oxygen in the shielding gas.

First claim

The invention claimed is:

1. A weld comprising a weld metal for ferritic steel base metals, said weld metal comprising:
between 0.02 and 0.12 wt % carbon;
between 7.50 and 14.50 wt % nickel;
not greater than 1.00 wt % manganese;
not greater than 0.30 wt % silicon;
not greater than 150 ppm oxygen;
not greater than 100 ppm sulfur;
not greater than 75 ppm phosphorus; and
the balance iron,
wherein the weld metal comprises retained austenite and further comprises a cellular microstructure comprising cell walls having a volume fraction in the range of from 20% to 40% based on the total volume fraction of the weld metal and cell interiors having a volume fraction in the range of from 60% to 80% based on the total volume fraction of the weld metal, and wherein the cell walls are harder than the cell interiors and said weld metal in the weld has been 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 0.30 wt % copper,
not greater than 0.04 wt % vanadium,
not greater than 0.30 wt % chromium,
not greater than 0.40 wt % molybdenum,
not greater than 0.04 wt % niobium,
not greater than 0.02 wt % titanium,
not greater than 0.02 wt % zirconium,
not greater than 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 comprising a weld metal for ferritic steel base metals, said weld metal comprising:
between 0.02 and 0.12 wt % carbon;
between 7.50 and 14.50 wt % nickel;
not greater than 1.00 wt % manganese;
not greater than 0.30 wt % silicon;
not greater than 100 ppm sulfur;
not greater than 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 having a volume fraction in the range of from 20% to 40% based on the total volume fraction of the weld metal and cell interiors having a volume fraction in the range of from 60% to 80% based on the total volume fraction of the weld metal, and 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 in the weld has been applied using a gas metal arc welding process with pulsed waveform power supply and a shielding gas comprising helium, argon, and CO 2 wherein helium comprises 25 or more volume percent of said shielding gas and CO 2 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 1.00 wt % manganese, not greater than 0.30 wt % silicon, not greater than 150 ppm oxygen, not greater than 100 ppm sulfur, not greater than 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 150 ppm oxygen, and
controlling the weld pool characteristics and arc stability during welding to provide satisfactory weldability, wherein the weld metal has a cellular microstructure comprising cell walls having a volume fraction in the range of from 20% to 40% based on the total volume fraction of the weld metal and cell interiors having a volume fraction in the range of from 60% to 80% based on the total volume fraction of the weld metal, and wherein the cell walls are harder than the cell interiors.

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 and CO 2 , and the step of controlling the weld pool flow characteristics and arc stability comprises welding current waveform control sufficient to provide satisfactory weldability.

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 1.00 wt % manganese, not greater than 0.30 wt % silicon, not greater than 100 ppm sulfur, not greater than 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 using a welding shielding gas comprising not greater than 3 volume percent of CO 2 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, wherein the weld metal has a cellular microstructure comprising cell walls having a volume fraction in the range of from 20% to 40% based on the total volume fraction of the weld metal and cell interiors having a volume fraction in the range of from 60% to 80% based on the total volume fraction of the weld metal, and 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.

13. The method of claim 12 wherein the weld metal further comprises at least one of the following:
not greater than 0.30 wt % copper,
not greater than 0.04 wt % vanadium,
not greater than 0.30 wt % chromium,
not greater than 0.40 wt % molybdenum,
not greater than 0.04 wt % niobium,
not greater than 0.02 wt % titanium,
not greater than 0.02 wt % zirconium,
not greater than 20 ppm boron.

14. The method of claim 12 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

Assignees

• Fairchild Douglas P
• Macia Mario L
• Ford Steven J
• Nissley Nathan E
• Ayer Raghavan
• Jin Hyun-Woo
• Ozekcin Adnan
• Exxonmobil Upstream Res Co

Inventors

• Fairchild Douglas P
• Macia Mario L
• Ford Steven J
• Nissley Nathan E
• Ayer Raghavan
• Jin Hyun-Woo
• Ozekcin Adnan

Classifications

• B23K2103/04

  Steel {or steel} alloys · CPC title

• B23K9/173 Primary

  and of a consumable electrode · CPC title

• B23K35/3066

  with Ni as next major constituent · CPC title

• B23K33/004

  Filling of continuous seams · CPC title

• B23K35/3053

  Fe as the principal constituent · CPC title