# US 2025/0060054 A1 · Austenitic welded steel tube having wear resistance and manufacturing method for same

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- Number: US 2025/0060054 A1
- Document ID: US20250060054A1
- Status: Published application
- Kind: A1
- Application number: 18/722,239
- Filed: 2022-12-20
- Published: 2025-02-20
- Earliest claimed: 2021-12-21
- Assignees: Posco
- Applicants: POSCO Co., Ltd
- Inventors: Sang-Chul LEE
- Web page: https://patentgrep.com/patent/US20250060054A1

## CPC

- B23K 9/0282: {for welding tube sections}
- F16L 9/02: of metal (F16L9/16 - F16L9/22 take precedence)
- B23K 9/16: making use of shielding gas
- B23K 9/18: Submerged-arc welding
- B23K 31/027: {Making tubes by soldering or welding}
- B23K 35/3073: {with Mn as next major constituent}
- C21D 1/18: Hardening (C21D1/02 takes precedence); Quenching with or without subsequent tempering (quenching devices C21D1/62)
- C21D 6/002: {containing Cr (C21D6/004 takes precedence)}
- C21D 6/005: {containing Mn}
- C21D 8/0226: {Hot rolling}
- C21D 8/10: during manufacturing of tubular bodies
- C21D 9/08: for tubular bodies or pipes
- C21D 9/14: wear-resistant or pressure-resistant pipes
- C21D 9/46: for sheet metals
- C22C 38/02: containing silicon
- C22C 38/04: containing manganese
- C22C 38/38: with more than 1.5% by weight of manganese
- B23K 2101/04: Tubular or hollow articles
- B23K 2103/04: Steel {or steel} alloys
- C21D 2211/001: Austenite
- B23K: SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- F16L: PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- 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)
- C22C: ALLOYS (treatment of alloys C21D, C22F)

## Abstract

According to aspects of the present invention, provided are a welded steel tube and a manufacturing method for the same which can provide excellent wear resistance and also minimize hot cracking of the welded portion, so a lifespan thereof may be effectively maximized even when applied in harsh wear-resistant environments.

## Claims

### Claim 1

A manufacturing method for an austenitic welded steel tube, the method comprising:
forming an austenitic steel sheet into a tubular shape to form a butted portion; and
providing a welded steel tube by welding the butted portion with a heat input of 4.3 kJ/mm or less.

### Claim 2 (depends on 1)

The manufacturing method for an austenitic welded steel tube of claim 1, wherein the austenitic steel sheet comprises, by wt %, C: 0.6 to 1.3%, Si: 0.1 to 1.0%, Mn: 11 to 28%, Cr: 5.0% or less (including 0%), P: 0.025% or less, S: 0.025% or less, and a balance of Fe and unavoidable impurities,
stacking fault energy (SFE) defined by the following Relational Expression 1 satisfies a range of 10 to 40 mJ/m2, and
a microstructure includes austenite in an amount of 80 area % or more,
Stacking
⁢
Fault
⁢
Energy
⁢
(
SFE
)
=
⁠
-
24.9
+
0.814
*
[
Mn
]
+
44.3
*
[
C
]
-
0.62
*
[
Si
]
+
1.06
*
[
Cu
]
+
7.9
*
[
Al
]
-
0.555
*
[
Cr
]
[
Relational
⁢
Expression
⁢
1
]
where [Mn], [C], [Si], [Cu], [Al], and [Cr] denote the contents (wt %) of Mn, C, Si, Cu, Al, and Cr included in the steel sheet, respectively, and when the component is not included, 0 is substituted.

### Claim 3 (depends on 1)

The manufacturing method for an austenitic welded steel tube of claim 1, wherein a forming method of the austenitic steel sheet is any one selected from a spiral forming method, a UOE pressing method, a roll bending method, and a JCO forming method.

### Claim 4 (depends on 1)

The manufacturing method for an austenitic welded steel tube of claim 1, wherein a welding method of the butted portion is one or more arc welding selected from shield metal arc welding (SMAW), gas metal arc welding (GMAW), gas tungsten arc welding (GTAW), flux cored arc welding (FCAW) and sub-merged arc welding (SAW), or is electric resistance welding (ERW).

### Claim 5

An austenitic welded steel tube, comprising:
a welded steel tube base material portion in which austenite is a base structure; and
a welded portion connecting both ends of the welded steel tube base material portion to each other,
wherein a maximum crack length of hot cracks formed in the welded portion is 0.5 mm or less.

### Claim 6 (depends on 5)

The austenitic welded steel tube of claim 5, wherein the welded steel tube base material portion comprises, by wt %, C: 0.6 to 1.3%, Si: 0.1 to 1.0%, Mn: 11 to 28%, Cr: 5.0% or less (including 0%), P: 0.025% or less, S: 0.025% or less, and a balance of Fe and unavoidable impurities,
stacking fault energy (SFE) defined by the following Relational Expression 1 satisfies a range of 10 to 40 mJ/m2, and
a microstructure includes austenite in an amount of 80 area % or more,
Stacking
⁢
Fault
⁢
Energy
⁢
(
SFE
)
=
⁠
-
24.9
+
0.814
*
[
Mn
]
+
44.3
*
[
C
]
-
0.62
*
[
Si
]
+
1.06
*
[
Cu
]
+
7.9
*
[
Al
]
-
0.555
*
[
Cr
]
[
Relational
⁢
Expression
⁢
1
]
where [Mn], [C], [Si], [Cu], [Al], and [Cr] denote the contents (wt %) of Mn, C, Si, Cu, Al, and Cr included in the welded steel tube base material portion, respectively, and when the component is not included, 0 is substituted.

### Claim 7 (depends on 5)

The austenitic welded steel tube of claim 5, wherein during a wear resistance test specified in ASTM G65, a wear amount of the welded steel tube is 4 g or less.