KR20110069353A - High strength steel wire having excellent twist properties and mothod for manufacturing the same - Google Patents

Abstract

PURPOSE: A high-strength steel wire having excellent twist properties and a method for manufacturing the same are provided to restrain generation of delamination and increase wire drawing limit of a steel wire for wire drawing to enable manufacture of extra-high-strength steel wire. CONSTITUTION: A high-strength steel wire having excellent twist properties includes C 0.95~1.05%, Mn 0.3~0.8%, Si 0.4~1.0%, Cr 0.1~0.5%, residual Fe and other impurities. A twisting number is over 18 times. The high-strength steel wire is composed such that delamination is not generated. Hardening steel intensity is 2200~2400MPa.

Description

High strength steel wire with excellent torsion characteristics and its manufacturing method {HIGH STRENGTH STEEL WIRE HAVING EXCELLENT TWIST PROPERTIES AND MOTHOD FOR MANUFACTURING THE SAME}

The present invention relates to a high-strength steel wire used for bridge steel wire and tire cord steel wire, and a method of manufacturing the same, and more particularly, to control the drawing and heat treatment conditions to generate delamination during the post-processing of the wire. Instead, the present invention relates to a high strength steel wire having excellent torsion characteristics and a steel wire thereof.

Bridge steel wires and tire cords require high strength because they are reinforcements to support the force applied to the structure or tires.

Known methods for obtaining high strength steel wires are as follows.

1) how to increase the strength of the material itself

As a method for obtaining a high strength steel wire, there is a method of increasing the strength of the material itself by adding a large amount of reinforcing elements to increase the strength of the steel. Representative examples of such reinforcing elements include carbon. As the strength of the tire cord increases, the carbon content gradually increases from the sub-vacant area to the vacancy area and from the vacancy area to the super-vacant area. As described above, when the carbon content is increased, the fraction of hard cementite is increased in the wire rod and the lamellar spacing of the pearlite structure is dense, thereby improving the strength of the material. As such, a technique of adding various alloy elements in addition to carbon has been proposed.

2) How to increase work hardening rate

Steel wire for tire cords are manufactured by drawing and heat-treating rolled wire. The strength can be greatly improved by increasing the work hardening rate during the wire drawing of the wire rod. That is, when the work hardening rate is increased during lamination, the lamellar spacing becomes finer, the work hardening coefficient increases, and the degree of integration of dislocations increases, thereby increasing the strength of the steel wire.

3) Apart from the above, the strength can be improved by increasing the fresh strain of the tire cord material. At this time, the fresh strain of the material is closely related to the ductility of the material, and the material itself is advantageous in improving strength as it is easily processed without breaking wires during fresh processing.

However, since these methods do not all act independently but are related to each other to change the strength of steel wires, there is a limit to improving the strength of steel wires by controlling them independently.

For example, when a large amount of alloying elements are simply added to improve the strength of the wire rod, problems such as disconnection may occur due to poor ductility of the wire rod in a subsequent steel wire manufacturing process after wire rod rolling. Therefore, in order to improve the strength of the tire cord steel wire, it is necessary to consider various factors from various viewpoints.

The present invention is to solve the above-described problems, to provide a steel wire and a method of manufacturing the same, which maximizes the strength increase in consideration of various factors affecting the strength development of the steel wire, and at the same time excellent torsional characteristics.

The present invention is in weight percent, C: 0.95 to 1.05%, Mn: 0.3 to 0.8%, Si: 0.4 to 1.0%, Cr: 0.1 to 0.5%, the balance Fe and other unavoidable impurities, the number of twists more than 18 times It provides a high-strength steel wire having excellent torsion characteristics, characterized in that no delamination occurs during element wire processing.

At this time, the steel wire is characterized in that the phosphorus strength is 2200 ~ 2400MPa.

In addition, the present invention is a percentage by weight of the wire rod containing C: 0.95 to 1.05%, Mn: 0.3 to 0.8%, Si: 0.4 to 1.0%, Cr: 0.1 to 0.5%, balance Fe and other unavoidable impurities. Provides a method of manufacturing high strength steel wire with excellent torsion characteristics that does not cause delamination by heat treatment after drawing in the 80-90% range.

At this time, the heat treatment is characterized in that carried out for 10 to 40 seconds at 450 ~ 550 ℃.

As described above, the present invention can suppress the occurrence of delamination acting as a stumbling block of high strength, can provide a high strength steel wire with excellent torsional characteristics, and can increase the fresh system of the wire for wire drawing, ultimately the ultra high strength steel wire The effect of making it possible to manufacture can be obtained.

The present invention is in weight percent, C: 0.95 to 1.05%, Mn: 0.3 to 0.8%, Si: 0.4 to 1.0%, Cr: 0.1 to 0.5%, the balance Fe and other unavoidable impurities, the number of twists more than 18 times The present invention provides a high-strength steel wire having excellent torsion characteristics, and a method of manufacturing the same, wherein delamination does not occur during element wire processing.

Hereinafter, the present invention will be described in detail. (Hereinafter,% is% by weight.)

C: 0.95-1.05%

C is the most economical element for improving the strength of steel wire. If the content is less than 0.95%, the effect of improving strength is insufficient. If the content exceeds 1.05%, the strength is obtained but the ductility decreases. It is preferable to limit it to 0.95 to 1.05%.

Mn: 0.3 ~ 0.8%

Mn is an effective element to increase the hardenability or a high elemental segregation, which is very likely to cause low-temperature tissue when more than 0.8%, and the effect of the addition may not be sufficiently achieved when less than 0.3%. Therefore, the content of Mn is preferably limited to 0.3 ~ 0.8%.

Si: 0.4 ~ 1.0%

Si is a component that stabilizes the pearlite layer and increases strength and ductility along with a solid solution strengthening effect, and may be added at least 0.4% to achieve strength and ductility increase effect. However, when added in excess of 1.0%, the ductility is rapidly reduced to worsen the fresh workability. Therefore, the content of Si is preferably limited to 0.4 to 1.0%.

Cr: 0.1-0.5%

Cr is a component that improves strength and ductility by refining the layered structure of pearlite, and when added at less than 0.1%, there is no sufficient effect of miniaturization of the layered structure, and thus the strength and ductility improvement effect is insufficient. Slows down productivity. Therefore, the content of Cr is preferably limited to 0.1 to 0.5%.

The steel wire having the component system has a tensile strength of 2200 to 2400 MPa, the number of twists can be 18 or more, and no delamination occurs.

Hereinafter, the manufacturing method of the present invention will be described in detail.

Figure 1 shows a graph showing the change in tensile strength and the time of occurrence of delamination according to the cross-sectional reduction rate of the wire rod during the wire drawing of the present invention and the prior art.

As shown in Figure 1, in the prior art, although the steel wire was manufactured by stopping the drawing process before the point of delamination occurs, it can be seen that the present invention is drawn with a cross-sectional reduction rate that passes the point of delamination occurs.

According to the present invention, heat treatment is performed after the above-mentioned fresh working, and thus, heat treatment can be used to suppress delamination and to significantly improve the torsion characteristics.

In the present invention, the wire is processed to increase the strength of the wire rod having the composition as described above. When drawing, the cross-sectional reduction rate of the wire rod should be in the range of 80 to 90%, and if the cross-sectional reduction rate is less than 80%, the strength to be achieved by the present invention cannot be obtained. There is a disadvantage that disconnection occurs well.

After the drawing, the steel wire is heat-treated at a temperature in the range of 450 to 550 ° C. The heat treatment is to remove the residual stress that causes the delamination of the steel wire during the wire processing by remaining in the wire rod during the drawing process. If the heat treatment temperature is less than 450 ℃ steel wire is aged (aging) to increase the strength, but the ductility is sharply lowered, if it exceeds 550 ℃ the plate-like cementite contained in the pearlite structure changes into a spherical tensile strength Will drop. Therefore, the heat treatment temperature is preferably limited to the range of 450 ~ 550 ℃.

In addition, the heat treatment is performed for 10 to 40 seconds, it is difficult to effectively remove the residual stress when less than 10 seconds, and when more than 40 seconds, the spheroidization of cementite occurs, causing the problem of cementite fragmentation.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited by the following examples.

[Example]

The ingot having a component range of the following Table 1 was hot-rolled at 1000 ° C to manufacture a wire rod, and then the total reduction ratio was drawn to 79%, 81%, 85% and 91%, respectively to prepare a steel wire. Inventive materials 1 to 4 and Comparative Materials 1 to 4 of Table 2 are heat-treated at 500 ° C. for 20 seconds after the fresh processing, and Comparative Material 5 is not heat-treated after the fresh processing. The mechanical properties of Inventive Materials 1 to 4 and Comparative Materials 1 to 5 prepared as described above were measured, and the results are shown in Table 2 below.

division Ingredient (% by weight) C Si Mn Cr Inventive Steel 1 0.98 0.6 0.5 0.3 Inventive Steel 2 1.02 0.6 0.5 0.3 Comparative Steel 1 0.98 0.6 0.5 0.3

Steel grade Wire Rod No. Manufacture process Mechanical properties Reduction rate of cross section when drawing Whether to conduct heat treatment The tensile strength
(MPa) Torsion
(time) Delamination occurrence Inventive Steel 1 Comparative material 1 79 ○ 2107 27 Not Occurred Invention 1 81 ○ 2176 26 Not Occurred Invention Material 2 85 ○ 2283 24 Not Occurred Comparative material 2 91 ○ 2581 12 Occur Inventive Steel 2 Comparative material 3 79 ○ 2081 23 Not Occurred Invention 3 81 ○ 2223 21 Not Occurred Invention 4 85 ○ 2331 18 Not Occurred Comparative material 4 91 ○ 2602 9 Occur Comparative Steel 1 Comparative material 5 85 × 2293 3 Occur

As shown in Table 2, Inventions 1 to 4 prepared in the component range and manufacturing conditions according to the present invention has excellent strength, at the same time excellent in the torsion characteristics, in particular, no delamination occurred. This increased the amount of fresh processing compared to the existing manufacturing method, but it is believed that the plastic deformation performance was improved by removing the stress of the severely deformed pearlite structure through heat treatment and separating the carbon adhered to the potential to the base.

On the other hand, Comparative materials 1 and 3, but satisfying the component range of the present invention, it was found that the tensile strength is lower than that of the invention materials 1 to 4 by drawing less than the draw range of the present invention. In addition, the comparative materials 2 and 4 were excellent in tensile strength due to excessive drawing, but the torsional number (the number of revolutions in the break zone during the torsion test) tended to decrease significantly, and delamination also occurred. In addition, Comparative Material 5 was not subjected to heat treatment after the fresh working, so that the torsion characteristics were significantly lowered, and delamination occurred.

1 is a graph showing the change in tensile strength and the time of delamination according to the cross-sectional reduction rate when the wire is wired in the present invention and the prior art.

Claims (4)

In weight percent, C: 0.95 to 1.05%, Mn: 0.3 to 0.8%, Si: 0.4 to 1.0%, Cr: 0.1 to 0.5%, balance Fe and other unavoidable impurities, with at least 18 twists, High strength steel wire with excellent torsion characteristics, characterized in that no delamination occurs during processing. The high strength steel wire having excellent torsion characteristics according to claim 1, wherein the steel wire has a phosphorous strength of 2200 to 2400 MPa. By weight percent, wires containing C: 0.95 to 1.05%, Mn: 0.3 to 0.8%, Si: 0.4 to 1.0%, Cr: 0.1 to 0.5%, balance Fe and other unavoidable impurities, Process for producing high strength steel wire with excellent torsion characteristics that does not occur delamination by heat treatment after drawing in the range. The method of manufacturing a high strength steel wire having excellent torsion characteristics according to claim 3, wherein the heat treatment is performed at 450 to 550 ° C for 10 to 40 seconds.

Images