# US 11,441,202 B2 · Wire rod for cold heading, processed product using same, and manufacturing method therefor

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- Number: US 11,441,202 B2
- Document ID: US11441202B2
- Status: Granted
- Kind: B2
- Application number: 16/772,391
- Filed: 2018-10-10
- Published: 2021-03-18
- Granted: 2022-09-13
- Earliest claimed: 2017-12-26
- Assignees: Posco
- Applicants: Posco
- Inventors: Jae Seung Lee; Han Hwi Kim; In-Gyu Park; Byoung Gab Lee; Sang-Yoon Lee
- Web page: https://patentgrep.com/patent/US11441202B2

## CPC

- C21D 9/0093: {for screws; for bolts}
- C21D 6/002: {containing Cr (C21D6/004 takes precedence)}
- C21D 6/005: {containing Mn}
- C21D 6/008: {containing Si}
- C21D 8/06: during manufacturing of rods or wires
- 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 38/06: containing aluminium
- C22C 38/22: with molybdenum or tungsten
- C22C 38/24: with vanadium
- C22C 38/26: with niobium or tantalum
- C22C 38/28: with titanium or zirconium
- F16B 33/00: Features common to bolt and nut
- C21D 2211/003: Cementite
- C21D 2211/005: Ferrite
- C21D 2211/009: Pearlite
- C22C 38/18: containing chromium
- Y02P 10/20: Recycling
- 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)
- F16B: DEVICES FOR FASTENING OR SECURING CONSTRUCTIONAL ELEMENTS OR MACHINE PARTS TOGETHER, e.g. NAILS, BOLTS, CIRCLIPS, CLAMPS, CLIPS OR WEDGES; JOINTS OR JOINTING (couplings for transmitting rotation F16D)
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

The present disclosure provides a wire rod for cold heading that can shorten the spheroidizing heat treatment time, processed products using the same, and manufacturing method thereof. A wire rod for cold heading according to an embodiment of present disclosure includes, in percent (%) by weight of the entire composition, C: 0.15 to 0.5%, Si: 0.1 to 0.4%, Mn: 0.3 to 1.5%, Cr: 0.1 to 1.5%, Al: 0.02 to 0.05%, N: 0.004 to 0.02%, at least one selected from the group consisting of Nb: 0.001 to 0.03%, V: 0.01 to 0.3%, Mo: 0.01 to 0.5%, Ti: 0.001 to 0.03%, and the remainder of iron (Fe) and other inevitable impurities, and the microstructure has a long and short axis ratio of cementite present in pearlite colonies of 200:1 or less.

## Claims

### Claim 1

A wire rod for cold heading comprising, in percent (%) by weight of the entire composition, C: 0.15 to 0.5%, Si: 0.1 to 0.4%, Mn: 0.3 to 1.5%, Cr: 0.1 to 1.5%, Al: 0.02 to 0.05%, N: 0.004 to 0.02%, at least one selected from the group consisting of Nb: 0.001 to 0.03%, V: 0.01 to 0.3%, Mo: 0.01 to 0.5%, Ti: 0.001 to 0.03%, and the remainder of iron (Fe) and other inevitable impurities,
wherein the wire rod comprises a pearlite colony as microstructure,
wherein the long and short axis ratio of cementite present in the pearlite colony is 200: 1 or less,
wherein the wire rod comprises a ferrite as a microstructure, and the maximum size of the ferrite grain size is 5 μm or less.

### Claim 2 (depends on 1)

The wire rod of claim 1, wherein an area fraction of segmented cementite in the pearlite is 5 to 50%.

### Claim 3 (depends on 1)

The wire rod of claim 1, wherein a maximum size of the pearlite colony is 5μm or less.

### Claim 4 (depends on 1)

The wire rod of claim 1, wherein the wire rod comprises at least one precipitate of Al-based carbonitride, Nb-based carbonitride, V-based carbonitride, Mo-based carbonitride, and Ti-based carbonitride.

### Claim 5 (depends on 1)

A manufacturing method of a wire rod for cold heading, the manufacturing method comprising:
heating a steel piece comprising, in percent (%) by weight of the entire composition, C: 0.15 to 0.5%, Si: 0.1 to 0.4%, Mn: 0.3 to 1.5%, Cr: 0.1 to 1.5%, Al: 0.02 to 0.05%, N: 0.004 to 0.02%, at least one selected from the group consisting of Nb: 0.001 to 0.03%, V: 0.01 to 0.3%, Mo: 0.01 to 0.5%, Ti: 0.001 to 0.03%, and the remainder of iron (Fe) and other inevitable impurities;
hot rolling the heated steel piece by finish rolling the heated steel piece at 700 to 780° C.;
cooling to 600° C. at 5 to 20° C./s after the hot rolling, and cooling to 400° C. at 5° C./s or less; thereby producing the wire rod of claim 1.

### Claim 6 (depends on 5)

The manufacturing method of claim 5, wherein, in the hot rolling, the austenite grain size immediately before the finish rolling is 10 μm or less.

### Claim 7 (depends on 5)

The manufacturing method of claim 5, wherein, in the hot rolling, the amount of deformation during finish rolling is 0.4 or more.

### Claim 8 (depends on 5)

The manufacturing method of claim 5, wherein the heating the steel piece proceeds by maintaining within 90 minute at 900 to 1050° C.