Non-quenched and non-tempered steel wire rod for hot forging with excellent machinability and impact toughness and method for manufacturing same
Abstract
Provided are a non-quenched and non-tempered steel wire rod with improved machinability and impact toughness and a method for manufacturing the same. The non-quenched and non-tempered steel wire 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 balance of Fe and inevitable impurities, and includes ferrite and pearlite as a microstructure, wherein Relational Expression 1 below is satisfied and an area fraction of MnS satisfies a range of 0.10% to 0.60%. [Relational 2 0 ≤ [ Mn ] / [ S ] ≤ 7 0 [ Relational Expression 1 ]
Claims
exact text as granted — not AI-modifiedThe invention claimed is:
1 . A non-quenched and non-tempered steel wire rod 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 balance of Fe and inevitable impurities, and including ferrite and pearlite as a microstructure, wherein Relational Expression 1 below is satisfied and an area fraction of MnS satisfies a range of 0.10% to 0.60%:
20
≤
[
Mn
]
/
[
S
]
≤
70.
[
Relational
Expression
1
]
2 . The non-quenched and non-tempered steel wire rod according to claim 1 , wherein a number density of MnS is 70 ea/mm 2 or more.
3 . The non-quenched and non-tempered steel wire rod according to claim 1 , wherein an aspect ratio of MnS is 40 or less.
4 . The non-quenched and non-tempered steel wire rod according to claim 1 , wherein a tensile strength is 700 MPa or more.
5 . The non-quenched and non-tempered steel wire rod according to claim 1 , wherein a yield strength is 350 MPa to 500 MPa.
6 . The non-quenched and non-tempered steel wire rod according to claim 1 , wherein a yield ratio is 0.45 to 0.65.
7 . The non-quenched and non-tempered steel wire rod according to claim 1 , wherein an impact toughness is 60 J/cm 2 or more.
8 . The non-quenched and non-tempered steel wire rod according to claim 1 , wherein a tensile strength x impact toughness value is 45000 MPa·J/cm 2 or more.
9 . A method for manufacturing a non-quenched and non-tempered steel wire rod with improved machinability and impact toughness, the method comprising:
reheating a steel piece 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 balance of Fe and inevitable impurities, and including ferrite and pearlite as a microstructure in a temperature range of 950° C. to 1120° C.; finish rolling the reheated steel piece into a steel wire rod at a temperature of 750° C. to 850° C.; and winding and cooling the steel wire rod, wherein the cooling performed after the winding comprises a process of cooling to 400° C. at an average cooling rate of 0.1° C./s to 5.0° C./s, wherein the steel wire rod includes ferrite and pearlite as a microstructure, Relational Expression 1 is satisfied, and an area fraction of MnS is 0.10% to 0.60%:
20
≤
[
Mn
]
/
[
S
]
≤
70.
[
Relational
Expression
1
]
10 . The method according to claim 9 , wherein a number density of MnS is 70 ea/mm 2 or more.
11 . The method according to claim 9 , wherein an aspect ratio of MnS is 40 or less.
12 . The method according to claim 9 , wherein a winding temperature is 750° C. to 850° C.Join the waitlist — get patent alerts
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