US2025333811A1PendingUtilityA1
Non-quenched and tempered steel rod wire with improved machinability and toughness and method for manufacturing same
Est. expiryMay 27, 2042(~15.8 yrs left)· nominal 20-yr term from priority
C21D 8/06C22C 38/60C22C 38/18C22C 38/06C22C 38/04C22C 38/02C22C 38/002C22C 38/001C21D 9/525B21C 47/02C21D 2211/009C21D 2211/005C21D 8/0226C21D 9/573B21B 1/16C21D 2211/004C22C 38/28C21D 8/065C21D 1/02
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Claims
Abstract
Provided are a non-quenched and tempered steel rod wire with improved machinability and impact toughness and method for manufacturing same. The non-quenched and tempered steel rod wire according to the present disclosure includes, in percent by weight (wt %), 0.3% to 0.5% of C, 0.4% to 0.9% of Si, 0.5% to 1.2% of Mn, 0.02% or less of P, 0.01% to 0.05% of S, 0.015% to 0.05% of sol·Al, 0.1% to 0.3% of Cr, 0.007% to 0.02% of N, and the balance being Fe and inevitable impurities, wherein a microstructure includes ferrite and pearlite, and Relational Expression 1 below is satisfied: [Relational Expression1][N]-[Al]/1.93≤0.009.
Claims
exact text as granted — not AI-modified1 . A non-quenched and tempered steel rod wire with improved machinability and impact toughness comprising, in percent by weight (wt %), 0.3% to 0.5% of C, 0.4% to 0.9% of Si, 0.5% to 1.2% of Mn, 0.02% or less of P, 0.01% to 0.05% of S, 0.015% to 0.05% of sol·Al, 0.1% to 0.3% of Cr, 0.007% to 0.02% of N, and the balance being Fe and inevitable impurities,
wherein a microstructure includes ferrite and pearlite, and
Relational Expression 1 below is satisfied:
[
N
]
-
[
Al
]
/
1.93
≤
0.009
.
[
Relational
Expression
1
]
2 . The non-quenched and tempered steel rod wire according to claim 1 , wherein Relational Expression 2 below was satisfied:
-
23
[
C
]
+
[
Si
]
(
5
-
2
[
Si
]
)
-
4
[
Mn
]
+
104
[
S
]
+
3
≥
0.
[
Relational
Expression
2
]
3 . The non-quenched and tempered steel rod wire according to claim 1 , wherein an area fraction of ferrite, measured in a region from the center to a quarter or more of the diameter of the steel rod wire from the surface, is 20% to 40%.
4 . The non-quenched and tempered steel rod wire according to claim 1 , wherein an area fraction of the formed AlN is 0.03% or more.
5 . The non-quenched and tempered steel rod wire according to claim 1 , wherein a size of the formed AlN is 150 nm or less.
6 . The non-quenched and tempered steel rod wire according to claim 1 , wherein the number of carbonitrides having an average equivalent circular diameter of 100 nm or less per unit area is 2 ea./μm 2 or more.
7 . The non-quenched and tempered steel rod wire according to claim 1 , wherein a tensile strength is 700 MPa or more.
8 . The non-quenched and tempered steel rod wire according to claim 1 , wherein a yield strength is 350 MPa to 450 MPa.
9 . The non-quenched and tempered steel rod wire according to claim 1 , wherein a yield ratio is 0.45 to 0.65.
10 . The non-quenched and tempered steel rod wire according to claim 1 , wherein a room-temperature impact toughness is 60 J/cm 2 or more.
11 . The non-quenched and tempered steel rod wire according to claim 1 , wherein a product of the tensile strength and the room-temperature impact toughness is 30000 to 60000.
12 . A method for manufacturing a non-quenched and tempered steel rod wire with improved machinability and impact toughness, the method comprising:
reheating a steel piece including, in percent by weight (wt %), 0.3% to 0.5% of C, 0.4% to 0.9% of Si, 0.5% to 1.2% of Mn, 0.02% or less of P, 0.01% to 0.05% of S, 0.015% to 0.05% of sol·Al, 0.1% to 0.3% of Cr, 0.007% to 0.02% of N, and the balance being Fe and inevitable impurities at a temperature of 950° C. to 1100° C.; finish rolling the reheated steel piece into a steel rod wire at a temperature of 750° C. to 850° C.; and winding and cooling the steel rod wire; wherein the cooling performed after the winding includes a process of cooling the steel rod wire to 400° C. at an average cooling rate more than 0.1° C./s but not more than 5.0° C./s, and the steel rod wire satisfies the Relational Expression 1 below:
[
N
]
-
[
Al
]
/
1.93
≤
0.009
.
[
Relational
Expression
1
]
13 . The method according to claim 12 , wherein Relational Expression 2 below is satisfied:
-
23
[
C
]
+
[
Si
]
(
5
-
2
[
Si
]
)
-
4
[
Mn
]
+
104
[
S
]
+
3
≥
0.
[
Relational
Expression
2
]
14 . The method according to claim 12 , wherein an area fraction of ferrite, measured in a region from the center to a quarter or more of the diameter of the steel rod wire from the surface, is 20% to 40%.
15 . The method according to claim 12 , wherein an area fraction of AlN formed in the reheating process is 0.03% or more.
16 . The method according to claim 12 , wherein a size of AlN formed in the reheating process is 150 nm or less.
17 . The method according to claim 12 , wherein the number of carbonitrides having an average equivalent circular diameter of 100 nm or less per unit area is 2 ea./μm 2 or more.
18 . The method according to claim 12 , wherein a tensile strength is 700 MPa or more.
19 . The method according to claim 12 , wherein a yield strength is 350 MPa to 450 MPa.
20 . The method according to claim 12 , wherein a yield ratio is 0.45 to 0.65.
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