C+N AUSTENITIC STAINLESS STEEL HAVING HIGH STRENGTH AND EXCELLENT CORROSION RESISTANCE, AND FABRICATION METHOD THEREOF

• US 20110226391A1
• Filed: 08/20/2009
• Published: 09/22/2011
• Est. Priority Date: 07/13/2009
• Status: Abandoned Application

• Current Assignee: Korea Institute of Machinery and Materials (Dawonsys Co., Ltd.)
• Original Assignee: Korea Institute of Machinery and Materials (Dawonsys Co., Ltd.)
• Inventors: Lee, Tae-Ho, Ha, Heon-Young, Oh, Chang-Seok, Kim, Sung-Joon
• Application Number:
  US12/994,815
• Publication Number:
  US 20110226391A1
• Time in Patent Office: Days
• US Class Current: 148/542
• CPC Class Codes: C21D 1/18 Hardening C21D1/02 takes precedence; Quenching with or without subsequent tempering quenching devices C21D1/62
• CPC Class Codes: C21D 2211/001 Austenite
• CPC Class Codes: C21D 6/002 containing Cr C21D6/004 takes precedence
• CPC Class Codes: C21D 6/005 containing Mn
• CPC Class Codes: C21D 8/021 involving a particular fabrication or treatment of ingot or slab
• CPC Class Codes: C21D 8/0226 Hot rolling
• CPC Class Codes: C21D 8/0405 of ferrous alloys
• CPC Class Codes: C21D 8/041 involving a particular fabrication or treatment of ingot or slab
• CPC Class Codes: C21D 8/0426 Hot rolling
• CPC Class Codes: C22C 38/001 containing N
• CPC Class Codes: C22C 38/22 with molybdenum or tungsten
• CPC Class Codes: C22C 38/38 with more than 1.5% by weight of manganese
• CPC Class Codes: C22C 38/44 with molybdenum or tungsten
• CPC Class Codes: C22C 38/58 with more than 1.5% by weight of manganese

Abstract

A C+N austenitic stainless steel with high mechanical strength and excellent corrosion resistance and a fabrication method thereof are provided. The C+N austenitic stainless steel consists of: 8 to 12 wt. % manganese; 15 to 20 wt. % chromium; 2 wt. % or less nickel; 4 wt. % or less tungsten; 2 wt. % or less molybdenum; 0.6 to 1.0 wt. % of total C+N content; a balance of iron; and unavoidable impurities. The austenitic stainless steel fabricated provides mechanical properties of a tensile strength of 850 MPa or higher and an uniform elongation of 45% or higher, obtained through controlling the contents of the interstitial elements and those of the substitutional elements. The alloy also provides corrosion resistance and a biocompatibility due to the minimized content of nickel which causes allergic reaction to the human body. Therefore, the C+N austenitic stainless steel is applicable in the fabrication of a variety of functional components and structural fields.

Claims

1. The C+N austenitic stainless steel with high mechanical strength and excellent corrosion resistance comprising:

8 to 12 wt. % manganese (Mn);

15 to 20 wt. % chromium (Cr);

2 wt. % or less nickel (Ni);

0.6 to 1.0 wt. % of total C+N content;

4 wt. % or less tungsten (W);

2 wt. % or less molybdenum (Mo);

a balance of iron (Fe); and

unavoidable impurities.

2. The C+N austenitic stainless steel of claim 1, wherein the wt. % of tungsten (W) is 1 to 4 wt. %, and the wt. % of molybdenum (Mo) is 0 wt. %.

3. The C+N austenitic stainless steel of claim 1, wherein the wt. % of tungsten (W) is 0 wt. %.

4. The C+N austenitic stainless steel of claim 1, wherein the wt. % of tungsten (W) is 1 to 4 wt. %.

5. The C+N austenitic stainless steel of claim 1, wherein the ratio of manganese (Mn) to chromium (Cr) (Mn/Cr) ranges from 0.5 to 1.0.

6. The C+N austenitic stainless steel of claim 1, wherein the total content of manganese (Mn) and chromium (Cr) ([Mn+Cr]) is 30 wt. % or less.

7. The C+N austenitic stainless steel of claim 1, wherein the nitrogen (N) content is 0.3 wt. % or more.

8. The C+N austenitic stainless steel of claim 1, wherein the total content of tungsten (W) and molybdenum (Mo) (0.5W+Mo) is 3 wt. % or less.

9. The C+N austenitic stainless steel of claim 1, further comprising mechanical properties including a tensile strength of 850 MPa or higher, and an uniform elongation of 45% or more.

10. A fabrication method of the C+N austenitic stainless steel with high mechanical strength and excellent corrosion resistance, the fabrication method comprising:

master alloy charging in which a master alloy is charged into a vacuum melting furnace;

vacuum maintaining in which the vacuum melting furnace with the master alloy charged therein is maintained under vacuum;

master alloy melting in which the vacuum melting furnace is heated and the master alloy is melted;

nitrogen (N) content adjusting in which nitrogen gas is injected into the vacuum melting furnace;

melted alloy agitating in which the melted master alloy is agitated;

ingot forming in which an ingot is formed by pouring the agitated melted alloy from the vacuum melting furnace;

hot-rolling the formed ingot; and

performing water quenching of the hot-rolled stainless steel to prevent precipitation of carbide which degrades the mechanical property and corrosion resistance.

11. The fabrication method of claim 10, wherein in the vacuum maintaining step, the vacuum level inside the vacuum melting furnace is kept at 10⁻

3 torr or lower.

12. The fabrication method of claim 10, wherein the nitrogen (N) content adjusting comprises:

nitrogen gas injecting in which nitrogen gas is injected to the interior of the vacuum melting furnace; and

pressure adjusting in which the partial pressure of nitrogen gas of the interior of the vacuum melting furnace is adjusted to 1 atm.