Austenitic steel having excellent machinability and ultra-low temperature toughness in weld heat-affected zone, and method of manufacturing the same

Patent metadata

Field	Value
Publication number	US-10655196-B2
Application number	US-201214369090-A
Country	US
Kind code	B2
Filing date	Dec 27, 2012
Priority date	Dec 27, 2011
Publication date	May 19, 2020
Grant date	May 19, 2020

Abstract

According to the present invention, a low-cost ultra-low temperature steel may be obtained, a stable austenite phase may be formed at low temperature, carbide formation may be effectively suppressed, and a structural steel having excellent machinability and ultra-low temperature toughness in a weld heat-affected zone may be provided.

First claim

The invention claimed is:

1. An austenitic steel having improved machinability and ultra-low temperature toughness in a weld heat-affected zone, the austenitic steel comprising:
a parent material and a weld heat-affected zone,
wherein the parent material comprises:
15 wt % to 35 wt % of manganese (Mn);
carbon (C) satisfying 23.6C+Mn≥28 and 33.5C−Mn≤23;
5 wt % or less (excluding 0 wt %) of copper (Cu);
chromium (Cr) satisfying 28.5C+4.4Cr≤57 (excluding 0 wt %);
0.012 wt % to 0.13 wt % of nitrogen (N);
0.5 wt % or less (excluding 0 wt %) of niobium (Nb); and
iron (Fe) as well as other unavoidable impurities as a remainder, and
wherein a microstructure of the weld heat-affected zone comprises austenite having an area fraction of 95% or more, and
wherein an area fraction of carbide located at austenite grain boundaries in the weld heat-affected zone is 5% or less.

2. The austenitic steel having improved machinability and ultra-low temperature toughness in a weld heat-affected zone of claim 1 , the parent material further comprising:
0.03 wt % to 0.1 wt % of sulfur (S); and
0.001 wt % to 0.01 wt % of calcium (Ca),
wherein a Charpy impact value of the weld heat-affected zone at −196° C. is 41 J or more.

3. The austenitic steel having improved machinability and ultra-low temperature toughness in a weld heat-affected zone of claim 1 , the parent material further comprising at least one of 0.5 wt % or less of titanium (Ti), and 0.5 wt % or less of vanadium (V).

Assignees

• Posco

Inventors

• Lee Soon-Gi
• Choi Jong-Kyo
• Park Young-Hwan
• Noh Hee-Goon
• Cho Hyun-Kwan
• Suh In-Shik
• Park In-Gyu
• Lee Hong-Ju

Classifications

• C22C38/26

  with niobium or tantalum · CPC title

• C22C38/20

  with copper · CPC title

• C22C38/24

  with vanadium · CPC title

• C22C38/28

  with titanium or zirconium · CPC title

• C22C38/001

  containing N · CPC title