# US 12,110,578 B2 · Austenitic stainless steel having a large amount of unifromly distributed nanometer-sized precipitates and preparing method of the same

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- Number: US 12,110,578 B2
- Document ID: US12110578B2
- Status: Granted
- Kind: B2
- Application number: 17/045,267
- Filed: 2019-12-06
- Published: 2023-04-20
- Granted: 2024-10-08
- Earliest claimed: 2019-11-18
- Assignees: Korea Advanced Institute of Science and Technology
- Applicants: Korea Advanced Institute of Science and Technology
- Inventors: Changheui Jang; Jiho Shin; Byeong Seo Kong; Hyeon Bae Lee; Chaewon Jeong; Hyun Woo Koo
- Web page: https://patentgrep.com/patent/US12110578B2

## CPC

- C22C 38/58: with more than 1.5% by weight of manganese
- C21D 6/004: {containing Cr and Ni}
- C21D 6/005: {containing Mn}
- C21D 6/02: Hardening by precipitation
- C21D 8/02: during manufacturing of plates or strips (C21D8/12 takes precedence)
- C21D 8/0226: {Hot rolling}
- C22C 38/00: Ferrous alloys, e.g. steel alloys (cast-iron alloys C22C37/00)
- C22C 38/001: {containing N}
- C22C 38/02: containing silicon
- C22C 38/04: containing manganese
- C22C 38/44: with molybdenum or tungsten
- C22C 38/48: with niobium or tantalum
- C22C 38/50: with titanium or zirconium
- C21D 2211/001: Austenite
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- C21D: MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B)

## Abstract

Austenitic stainless steel includes 16 to 26 wt % of chromium (Cr), 8 to 22 wt % of nickel (Ni), 0.02 to 0.1 wt % of carbon (C), 0.2 to 1 wt % of niobium (Nb), and 2 to 3.5 wt % of manganese (Mn), and has an austenite matrix, wherein a nanosized niobium carbide (NbC) is precipitated in the austenite matrix, and the nanosized niobium carbide is uniformly dispersed in the austenite matrix. The austenitic stainless steel may further include 0.5 to 1.5 wt % of molybdenum (Mo).

## Claims

### Claim 1

Austenitic stainless steel comprising
16 to 26 wt % of chromium (Cr), 8 to 22 wt % of nickel (Ni), 0.02 to 0.1 wt % of carbon (C), 0.2 to 1 wt % of niobium (Nb), and 2 to 3.5 wt % of manganese (Mn),
and including an austenite matrix, wherein
a niobium carbide (NbC) is precipitated in the austenite matrix, and
the niobium carbide is uniformly dispersed in the austenite matrix,
wherein an average diameter of the niobium carbide is equal to or less than 11 nm, and
wherein the austenitic stainless steel is a forged multi-pass hot rolled stainless steel.

### Claim 2 (depends on 1)

The austenitic stainless steel of claim 1, wherein
the austenitic stainless steel further includes 0.5 to 1.5 wt % of molybdenum (Mo).

### Claim 3 (depends on 2)

The austenitic stainless steel of claim 2, wherein
a niobium-molybdenum carbide is precipitated in the austenite matrix, and the niobium-molybdenum carbide is uniformly dispersed in the austenite matrix.

### Claim 4 (depends on 3)

The austenitic stainless steel of claim 3, wherein
the austenitic stainless steel further includes greater than 0 wt % and equal to or less than 0.3 wt % of silicon (Si).

### Claim 5 (depends on 3)

The austenitic stainless steel of claim 3, wherein
an average size of the niobium-molybdenum carbide is equal to or less than 6 nm.

### Claim 6 (depends on 3)

The austenitic stainless steel of claim 3, wherein
a number density of the niobium-molybdenum carbide is 5×1014-5×1015 #/m2 in the austenite matrix.

### Claim 7 (depends on 3)

The austenitic stainless steel of claim 3, wherein
a density of the niobium-molybdenum carbide is 1×1022-5×1023 #/m3 in the austenite matrix.

### Claim 8 (depends on 1)

The austenitic stainless steel of claim 1, wherein
a number density of the niobium carbide is 1×1014-5×1015 #/m2 in the austenite matrix.

### Claim 9 (depends on 1)

The austenitic stainless steel of claim 1, wherein
a density of the niobium carbide is 1×1022-1×1023 #/m3 in the austenite matrix.

### Claim 10 (depends on 1)

The austenitic stainless steel of claim 1, wherein
the austenitic stainless steel further includes greater than 0 wt % and equal to or less than 0.01 wt % of phosphorus (P) and greater than 0 wt % and equal to or less than 0.01 wt % of sulfur (S).