STEEL WIRE WITH IMPROVED DRAWABILITY, AND MANUFACTURING METHOD THEREFOR

Abstract

A steel wire with improved drawability, and a manufacturing method therefor are disclosed. A steel wire according to the present invention comprises, by wt %, 0.52-0.69% of C, 0.3-0.8% of Mn, 0.1-0.5% of Si, and the balance of Fe and inevitable impurities, wherein the carbon content of cementite in pearlite is 7 at. % or more, and the following formula (1) is satsified.

[TS]+exp(?)*10<1500(1)

In Expression (1), [TS] means the tensile strength (MPa) of a wire before drawing, and e means draw strain.

Claims

1. A steel wire with improved drawability, which comprises, in weight percent, C: 0.52 to 0.69%, Mn: 0.3 to 0.8%, Si: 0.1 to 0.5%, a balance of Fe, and unavoidable impurities, has a carbon content of cementite in pearlite of 7 at % or more, and satisfies the following Expression (1),
TS+exp(?)*10<1500(1) In Expression (1), TS denotes a tensile strength (MPa) of a wire rod before drawing, and ? denotes a drawing strain.

2. The steel wire of claim 1, wherein the wire rod has a tensile strength of 700 to 1,000 MPa before the drawing.

3. The steel wire of claim 1, wherein the torsion number of the steel wire is 27 or more.

4. The steel wire of claim 1, wherein delamination does not occur at a drawing strain of 4.02 or less.

5. A method for manufacturing a steel wire with improved drawability, comprising: hot-rolling a billet comprising, in weight percent, C: 0.52 to 0.69%, Mn: 0.3 to 0.8%, Si: 0.1 to 0.5%, a balance of Fe, and unavoidable impurities to obtain a wire rod; cooling the hot-rolled wire rod at a cooling rate of 3 to 20? C./s; and obtaining a steel wire by drawing the cooled wire rod to satisfy the following Expression (1),
[TS]+exp(?)*10<1500(1) In Expression (1), [TS] denotes a tensile strength (MPa) of a wire rod before drawing, and ? denotes a drawing strain.

6. The method of claim 5, wherein delamination does not occur at a wire strain rate of 4.02 or less during the drawing.

Description

EXAMPLES

[0052] After hot-rolling a billet having an alloy composition and a component range including, in weight percent, C: 0.57 to 0.67%, Mn: 0.3 to 0.8%, Si: 1.0 to 1.6%, a balance of Fe, and other unavoidable impurities, cooling was performed at a cooling rate of 17? C./s in Inventive Examples 1 to 3, and cooling at a cooling rate of 5? C./s in Inventive Examples 5 and 6 and Comparative Example 1 to obtain wire rods, and then for Inventive Examples 1 to 5 and Comparative Example 1 in Table 1 below, steel wires were manufactured by drawing according to conditions of a carbon content of cementite, a wire rod strength, and a drawing strain in Table 1 below. Table 1 below shows a torsion number of each steel wire manufactured as described above and whether delamination occurred.

[0053] The torsion number of the steel wire was determined by the number of turns until the steel wire broke during a torsion test applying transverse stress, and the presence or absence of delamination was indicated by checking whether a spiral fracture defect appeared at a wire fracture portion.

TABLE-US-00001 TABLE 1 Carbon Wire rod content of Delamination Value of strength Drawing cementite Torsion Occurred or Expression Classification (MPa) strain (at %) number not (1) Inventive 856 3.57 12 36 Did not occur 1211 Example 1 Inventive 844 3.79 11 34 Did not occur 1287 Example 2 Inventive 848 4.02 9 30 Did not occur 1405 Example 3 Inventive 948 3.57 10 35 Did not occur 1303 Example 4 Inventive 950 3.79 9 33 Did not occur 1393 Example 5 Comparative 967 4.02 6 24 Occurred 1524 Example 1

[0054] As shown in Table 1, it can be confirmed that Inventive Examples 1 to 5 manufactured under the carbon content of cementite and drawing conditions consistent with the present invention not only had an excellent torsion number of 30 or more, but also delamination did not occur. Specifically, in the case of Comparative Example 1 in which the carbon content of cementite in perlite after drawing is 6 at %, and a value of Expression (1) exceeds 1,500, the torsion number was remarkably low at 24, and delamination occurred, but in the case of Inventive Examples 1 to 5 having a carbon content of cementite of 9 at % or more and a value of Expression (1) of less than 1,500, the torsion number was 30 or more and delamination did not occur. It can be confirmed that as the drawing strain increases, the possibility of delamination increases, but when comparing Inventive Example 3 and Comparative Example 1, even though Inventive Example 3 had the same drawing strain as Comparative Example 1, the tensile strength of a wire rod was reduced by 119 MPa, thereby securing a torsion number of 30 or more, and suppressing delamination.

[0055] In the foregoing, although exemplary embodiments of the present invention have been described, the present invention is not limited thereto, and those skilled in the art will be able to understand that various changes and modifications are possible without departing from the concept and scope of the claims described below.

INDUSTRIAL APPLICABILITY

[0056] According to one embodiment of the present invention, it is possible to provide a steel wire with improved drawability by controlling the strength of a wire rod and slowing down a decomposition rate of cementite, and a method for manufacturing the same.