Welded joint of extremely low-temperature steel, and welding materials for preparing same

Patent metadata

Field	Value
Publication number	US-9981346-B2
Application number	US-201314442505-A
Country	US
Kind code	B2
Filing date	Nov 22, 2013
Priority date	Nov 22, 2012
Publication date	May 29, 2018
Grant date	May 29, 2018

Abstract

Provided are a welded joint of extremely low-temperature steel and flux cored, submerged, and gas metal arc welding materials which can be used to prepare the welded joint, wherein the welded joint of extremely low-temperature steel has outstanding impact toughness in extremely low-temperature conditions and excellent yield strength at room temperature.

First claim

The invention claimed is:

1. A welded joint of extremely low temperature steel, the welded joint comprising, by wt %, carbon (C): 0.05% to 1.30%, silicon (Si): 0.2% to 1.8%, manganese (Mn): 0.4% to 23%, chromium (Cr): 0.01% to 12%, nickel (Ni): 23% to 49%, at least one selected from molybdenum (Mo), cobalt (Co), and tungsten (W): 0.01% to 10%, aluminum (Al): 0.2% or less (excluding 0%), titanium (Ti): 0.9% or less (excluding 0%), at least one selected from niobium (Nb) and vanadium (V): 0.9% or less, at least one selected from sulfur (S) and phosphorus (P): 0.035% or less (excluding 0%), and the balance of iron (Fe) and inevitable impurities,
wherein the at least one selected from molybdenum (Mo), cobalt (Co), and tungsten (W) (expressed as “Mo+W+Co”), the at least one selected from niobium (Nb) and vanadium (V) (expressed as “Nb+V”), and the nickel (Ni), chromium (Cr), aluminum (Al), and titanium (Ti) satisfy Formula 1 below:
1.5Ni-8Cr-2.5(Mo+W+Co)-20Al-29Ti-55(Nb+V)≥0.  (Formula 1)

2. The welded joint of claim 1 , wherein the at least one selected from molybdenum (Mo), cobalt (Co), and tungsten (W) (expressed as “Mo+W+Co”), the at least one selected from niobium (Nb) and vanadium (V) (expressed as “Nb+V”), and the nickel (Ni), chromium (Cr), aluminum (Al), and titanium (Ti) further satisfy Formula 2 below:
98.5C-1.08Mn+9.73Cr-1.52Ni+10.3(Mo+W+Co)+122Ti+34.7(Nb+V)≥0.  (Formula 2)

3. The welded joint of claim 1 , wherein the silicon (Si), aluminum (Al), and titanium (Ti) satisfy Formula 3 below:
Si+Al+Ti≤2.0.  (Formula 3)

4. The welded joint of claim 1 , wherein the welded joint has an impact toughness of 27 J or greater at an extremely low temperature of −196° C.

5. The welded joint of claim 1 , wherein the welded joint has a yield strength of 360 MPa or greater at room temperature.

6. The welded joint of claim 1 , further comprising, by wt %, one or more of nitrogen (N): 0.001% to 0.6% and boron (B): 0.0001% to 0.008%.

7. The welded joint of claim 6 , wherein the at least one selected from molybdenum (Mo), cobalt (Co), and tungsten (W) (expressed as “Mo+W+Co”), the at least one selected from niobium (Nb) and vanadium (V) (expressed as “Nb+V”), and the nickel (Ni), chromium (Cr), aluminum (Al), and titanium (Ti) further satisfy Formula 2 below:
98.5C-1.08Mn+9.73Cr-1.52Ni+10.3(Mo+W+Co)+122Ti+34.7(Nb+V)≥0.  (Formula 2)

8. The welded joint of claim 6 , wherein the silicon (Si), aluminum (Al), and titanium (Ti) satisfy Formula 3 below:
Si+Al+Ti≤2.0.  (Formula 3)

9. The welded joint of claim 6 , wherein the welded joint has an impact toughness of 27 J or greater at an extremely low temperature of −196° C.

Assignees

• Posco
• Posco Gyeongsangbuk Do

Inventors

• Han Il-Wook
• Kim Jeong-Kil
• Lee Bong-Keun
• Lee Hong-Kil

Classifications

• C22C38/10

  containing cobalt · CPC title

• C22C38/42

  with copper · CPC title

• B23K35/3086

  containing Ni or Mn · CPC title

• B23K35/3073

  with Mn as next major constituent · CPC title

• C22C38/12

  containing tungsten, tantalum, molybdenum, vanadium, or niobium · CPC title