Non-quenched and tempered steel rod wire for hot forging with improved machinability and toughness and method for manufacturing same
Abstract
Provided are a non-quenched and tempered steel rod wire with improved machinability and toughness and a method for manufacturing the same. The non-quenched and tempered steel rod 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, 0.01% to 0.05% of sol.Al, 0.1% to 0.3% of Cr, 0.01% to 0.02% of Ti, 0.0005% to 0.002% of Ca, 0.007% to 0.02% of N, and the remainder being Fe and inevitable impurities, and includes ferrite and pearlite as microstructures and satisfies Relational Expression 1 below: 2 ≤ ( Al + Ti ) / N ≤ 5. [ Relational Expression 1 ]
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, 0.01% to 0.05% of sol.Al, 0.1% to 0.3% of Cr, 0.01% to 0.02% of Ti, 0.0005% to 0.002% of Ca, 0.007% to 0.02% of N, and the remainder being Fe and inevitable impurities, and
including ferrite and pearlite as microstructures, wherein the steel rod wire satisfies Relational Expression 1 below:
2
≤
(
Al
+
Ti
)
/
N
≤
5.
[
Relational
Expression
1
]
2 . The non-quenched and tempered steel rod wire according to claim 1 , wherein the non-quenched and tempered steel rod wire satisfies Relational Expression 2 below:
10
≤
S
/
Ca
≤
7
0
.
[
Relational
Expression
2
]
3 . The non-quenched and tempered steel rod wire according to claim 1 , wherein the non-quenched and tempered steel rod wire satisfies Relational Expression 3 below:
7
0
0
≤
3
0
0
+
903
X
C
+
95
X
Si
+
154
X
Mn
-
2303
X
S
.
[
Relational
Expression
3
]
4 . The non-quenched and tempered steel rod wire according to claim 1 , wherein an average inter-layer spacing between ferrite and pearlite is 10.0 μm to 15.0 μm.
5 . The non-quenched and tempered steel rod wire according to claim 1 , wherein a thickness of the ferrite is 5.0 μm to 10.0 μm.
6 . The non-quenched and tempered steel rod wire according to claim 1 , wherein an aspect ratio of the ferrite is 4 or less.
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 an impact toughness is 60 J/cm 2 .
11 . The non-quenched and tempered steel rod wire according to claim 1 , wherein a product of tensile strength and 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, 0.01% to 0.05% of sol.Al, 0.1% to 0.3% of Cr, 0.01% to 0.02% of Ti, 0.0005% to 0.002% of Ca, 0.007% to 0.02% of N, and the remainder being Fe and inevitable impurities, and including ferrite and pearlite as microstructures, in a temperature range of 950° C. to 1120° 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 of 0.1° C./s to 5.0° C./s, and the steel rod wire satisfies Relational Expression 1 below:
2
≤
(
Al
+
Ti
)
/
N
≤
5.
[
Relational
Expression
1
]
13 . The method according to claim 12 , wherein the steel rod wire satisfies Relational Expression 2 below:
10
≤
S
/
Ca
≤
7
0
.
[
Relational
Expression
2
]
14 . The method according to claim 12 , wherein the steel rod wire satisfies Relational Expression 3 below:
7
0
0
≤
3
0
0
+
903
X
C
+
95
X
Si
+
154
X
Mn
-
2303
X
S
.
[
Relational
Expression
3
]
15 . The method according to claim 12 , wherein the steel rod wire has an average inter-layer spacing between ferrite and pearlite of 10.0 μm to 15.0 μm.
16 . The method according to claim 12 , wherein the ferrite of the steel rod wire has a thickness of 5.0 μm to 10.0 μm.
17 . The method according to claim 12 , wherein the ferrite of the steel rod wire has an aspect ratio of 4 or less.
18 . The method according to claim 12 , wherein a tensile strength of the steel rod wire is 700 MPa or more.
19 . The method according to claim 12 , wherein a yield strength of the steel rod wire is 350 MPa to 450 MPa.
20 . The method according to claim 12 , wherein a yield ratio of the steel rod wire is 0.45 to 0.65.
21 . The method according to claim 12 , wherein an impact toughness of the steel rod wire is 60 J/cm 2 or more.
22 . The method according to claim 12 , wherein a product of tensile strength and impact toughness of the steel rod wire is 30000 to 60000.Join the waitlist — get patent alerts
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